The team headed by Eric Ford, an assistant professor of astronomy, used the Canary Islands-based GTC to observe a known star and its Jupiter-sized orbiting planet as part of an effort aimed in part at learning how planets contract in size as their stars age. With analysis of the data from the observations now under way, the team also hoped to glean insights about how to tune the GTC’s capabilities to study not only huge, gaseous Jupiter-size planets but also Neptune-sized or “super-Earth”-sized planets that could be closer in composition to Earth.

“The excellent site and large size of the GTC plus the unique filtering capabilities of its detectors will allow astronomers to minimize the effects of Earth’s atmosphere,” Ford said. “By repeatedly measuring the color of exoplanets’ host stars, astronomers can study the atmospheres of exoplanets — and distinguish small planets from other phenomena such as large star spots or binary stars.”

The UF team’s late-May observations were among several announced earlier this week by the Instituto de Astrofisica de Canarias that marked the long-awaited scientific debut of the GTC, first launched in 2000 on the island of La Palma, and only recently completed. UF contributed $5 million to the roughly $180 million telescope and owns a 5 percent share – the only U.S. institution with an ownership stake in the telescope. The Spanish government owns 90 percent, with Mexico owning the remaining 5 percent.

The GTC’s unique 34.1-foot primary mirror, composed of 36 hexagonal segments, gives it unparalleled abilities to see deep into the universe and examine distant objects in great detail. The telescope is equally notable for the ultra-precise computer control of its mirror segments — control that makes possible more finely detailed images than achievable with other telescopes. Its size and controllability makes the GTC powerful enough to detect an ordinary candle from 20,000 miles away — and resolve the width of its flame from six miles away.

UF astronomers say they will use the telescope to learn more about what occurred in the earliest years of the universe, how stars, planets and galaxies come into being, and to discover and learn more about planets outside our solar system.

“We made this investment because we want our excellent faculty and students to have as much opportunity as possible for top-class research,” said Stan Dermott, chairman of the astronomy department. “In astronomy, that requires access to the best facilities.”

Ford, graduate student Knicole Colón, and postdoctoral associates Brian Lee and Suvrath Mahadven, tapped a Spanish-built astronomical instrument, OSIRIS, to gather the data on the extrasolar star, HAT-P-3, and its planet, HAT-P-3b.

However, A UF-designed and built instrument, CanariCam, is anticipated to be the second instrument installed on the GTC. Among other goals, CanariCam will explore origins and early evolution of planetary systems by imaging the protoplanetary disks where planets are born. UF astronomers also made significant contributions to a third instrument expected to be installed on the GTC known as FRIDA.

“The University of Florida is a partner not just in the observing sense,” Dermott said. “We are also a partner in the sense of being the major builder of instruments for the telescope.”

The GTC’s first, ceremonial observations occurred in 2007, before the telescope’s mirror was complete. A formal inauguration is planned for July 24 on the island of La Palma. King Juan Carlos I and Queen Sofia of Spain will preside over the ceremony.

University of Florida and University of California-Santa Cruz astronomers are the first to discover the onset of a huge flow of gas from a quasar, or the super-bright core of an extremely remote young galaxy still being formed. The gas was expelled from the quasar and its enormous black hole sometime in the space of four years around 10 billion years ago – an extremely brief and ancient blip noticed only by a sharp-eyed undergraduate and the unlikely convergence of two separate observational efforts.

“It was completely serendipitous,” said Fred Hamann, a UF astronomy professor. “In fact, the only way it could have happened is through serendipity.”

A paper about the research appeared online this month in the Letters of the Monthly Notices of the Royal Astronomical Society.

Quasars are enormously bright cores of very distant galaxies thought to contain “super-massive” black holes a billion times larger than our sun. They are seen only in the centers of very distant galaxies that formed long ago — galaxies whose light is just now reaching Earth after billions of years in transit. The quasar in question occurred about 10.3 billion years ago.

The black holes within quasars are invisible, but the cosmic material cascading toward them builds up and forms hot “accretion” disks, the source of quasars’ intense light. Some of the incoming material also can be expelled from quasars to form enormous gas clouds that zoom out at extremely high speeds. With the quasar in question, the gas is flowing at an astonishing rate of 58 million mph, Hamann said.

But while astronomers had observed the presence of such gas clouds with other quasars, they had never witnessed one actually coming into being — until now.

Hamann said the discovery was initiated when Kyle Kaplan, an undergraduate at UC-Santa Cruz, earlier this spring noticed peculiarities in the spectra, or wavelengths of light, that had been observed and recorded from the quasar. The spectra were gathered in 2006 as part of an effort to study the galaxies between the quasar and Earth.

UC-Santa Cruz Professor Jason Prochaska was aware of Hamann’s work on quasars and asked him to take a look.

When Hamann and other astronomers checked the spectra against the spectra of the same region recorded in a separate sky survey in 2002, they were surprised to discover that there were zero indications of the gas cloud.

“So that’s how we know this appeared between 2002 and 2006,” he said.

Daniel Progra, a physics professor at the University of Nevada, Las Vegas and an expert on gas outflows from astronomical objects, indicated the discovery is a lucky one.

“I am most excited about this work,” he said. “We humans cannot directly monitor changes in quasars as they take very many years. Therefore, a discovery of a change over a few years is very interesting. It is not unexpected, but chances are very small.”

He said the discovery supports a computer model he developed that predicts the gas outflows are dynamic and complicated.

Hamann said the discovery also opens a window to understanding more about how quasars come into being.

“The fact that we saw one appear in so short a time frame means that it’s a volatile type of structure,” he said. “It could be an evolutionary phase, or maybe a transition stage from one phase to another.”

It also poses interesting questions about the role of quasars in the formation of galaxies. Astronomers hope future observations will prove telling, Hamann said.

“One interesting question in astronomy is ‘how does the evolution of quasars relate to the evolution of galaxies?,’” he said. “The matter ejected from quasars might be the key to this relationship because it can disrupt or regulate the formation of galaxies around quasars. This discovery is a small piece of that story that we can see happening in real time, and what we are going to do now is keep watching.”

Other astronomers and authors of the paper are Paola Rodriquez Hidalgo, a UF graduate student, and Stephane Herbert-Fort, a University of Arizona graduate student.

The Sloan Digital Sky Survey III, slated to begin mid-year and end in mid-2014, consists of four independent surveys operated by the survey’s consortium. One will probe the distant universe and seek to learn more about mysterious dark energy, while two of the surveys will map the Milky Way and examine origins of stars. The UF-led survey will seek to find giant planets orbiting nearby stars and uncover more about the conditions in which they form.

“What we’re undertaking here is the largest homogeneous survey of planets ever conducted,” said Jian Ge, a UF professor of astronomy and the project’s principal investigator. “We not only want to find more planets, we also want to try to understand the big picture of how and where they form and evolve over time.”

At the heart of the survey — known as MARVELS, short for Multi-object Apache Point Observatory Radial Velocity Exoplanet Large-area Survey – is a UF-designed and built instrument capable of simultaneously surveying as many as 120 stars for planets.

The plan is to use the instrument, which employs a specially designed interferometer, to scour some 11,000 stars for orbiting giant planets — more than three times the number of stars searched by all other telescopes to date. The instrument detects planet signals through measuring the gravitational pull of the planet on the star.

The search is expected to yield not only at least 150 planets, almost double today’s number, but also provide much better understanding of the conditions needed for planets to be present. That’s important for future planet searches, including searches for Earth-like planets, because it will help astronomers narrow their search among millions of stars for those most likely to yield fast or interesting results.

“Only through a systematic, homogeneous survey like this one can we begin to understand different planet populations and probe planet distributions among different type stars and environments,” Ge said. “Also, this survey will provide many signposts for other astronomers using the really big, really expensive telescopes to discover smaller mass planets, possibly Earth-like planets, and also find more systems like our solar system.”

In order to substantially boost the survey speed and sample over current planet surveys capable of single object observations, the MARVELS survey will simultaneously target 120 relatively faint stars. The faintness of the stars largely limits the survey’s sensitivity to giant planets, although the UF instrument has four times the light particle, or photon, collecting power than current single object planet hunting instruments at other telescopes.

The search is expected to begin in the fall, shortly after the instrument is completed and installed. Like the other surveys, the MARVELS survey will be conducted from the 2.5 meter SDSS telescope at Apache Point Observatory in New Mexico.

The Sloan Digital Sky Survey III is a continuation of two previous SDSS surveys in the past eight years. The new survey is expected to be funded in part with a $7 million grant from the Alfred P. Sloan Foundation, with the survey and its four component surveys representing a total investment of about $50 million.

UF’s MARVELS instrument has about $2.5 million in funding, including part of an $875,000 grant from the W.M. Keck Foundation for an earlier, prototype version called the W.M. Keck Exoplanet Tracker. The UF survey is also being funded by the National Science Foundation, NASA and UF. Once the instrument is up and running, UF is expected to receive an additional roughly $6 million in funding for building another survey instrument, operating the survey, and handling the survey data, Ge said.

Ge said an added benefit of UF’s participation in the project is that it will allow UF astronomers free and timely access to data from all of the surveys. “We have full access to all that data, which is a huge scientific resource,” he said.

Stan Dermott, chairman of the UF astronomy department, noted that UF is also a partner with Spain in the world’s largest telescope, the Gran Telescopio Canarias, expected to begin scientific observations this year.

“Over the next 10 years,” he said, “the combination of the SDSS telescope and the GTC telescope may offer UF a unique tool to investigate both giant and Earth-like planets.”

But what if aliens were hunting life outside their own planet? Armed with telescopes only a bit bigger and more powerful than our own, could they peer through the vastness of space and lock in onto Earth as a likely home to life?

That’s the question at the heart of paper co-authored by a University of Florida astronomer that appeared this week in the online edition of Astrophysical Journal. The answer, the authors say, is a qualified “yes.” With a space telescope larger than the Hubble Space Telescope pointed directly at our sun, they say, “hypothetical observers” could measure Earth’s 24-hour rotation period, leading to observations of oceans and the chance of life.

“They would only be able to see Earth as a single pixel, rather than resolving it to take a picture,” said Eric Ford, a UF assistant professor of astronomy and one of five authors of the paper. “But that could be enough for them to identify our planet as one that likely contains clouds and oceans of liquid water.”

This research may sound whimsical, but it has a serious goal: to provide a road map for Earth-bound astronomers trying to study Earth-like planets — a task expected to become possible in coming decades as more powerful telescopes come on line, said Enric Palle, the lead author of the paper and an astronomer with the Instituto de Astrofisica de Canarias.

For humans or curious aliens, observing planets is challenging for a number of reasons – habitable planets all the more so. The planet can’t be too close or too far away from its star, or its surface would scald or freeze. And, it must have a protective atmosphere like Earth’s.

Most planets found so far are much larger than Earth, which means they are likely hot gas planets similar to Jupiter, a profoundly uninhabitable place with no solid surface and atmosphere composed largely of hydrogen and helium.

But astronomers are beginning to plan how future space telescopes could directly detect planets much closer to Earth’s size and proximity to the sun. One challenge: To figure out how to use a planet’s light to recognize if its surface and atmosphere are Earth-like.

For Ford and his colleagues, the answer lies in probing how the Earth would appear to outside or alien observers.

Astronomers have long recognized that even a large telescope would need to observe Earth for several weeks to collect enough light to identify chemicals in the planet’s atmosphere. During these observations, the brightness of the Earth would change, primarily because of clouds rotating into and out of view. If astronomers could measure Earth’s rotation period, then they would know when a given part of the planet was in view. The hitch was that astronomers were unsure whether Earth’s seemingly chaotically changing cloud patterns would make it impossible for alien observers to determine this rotation rate.

Based on data retrieved from satellite observations of Earth, Ford and his colleagues created a computer model for the brightness of the Earth, revealing that on the global scale Earth’s cloud cover is remarkably consistent — with rain forests usually turning up cloudy, arid regions clear, and so on. As a result, extraterrestrial astronomers who watched Earth for a period of several months would notice repeating patterns – a bit like watching the spots on a spinning ball come into view and then disappear. From those repeating patterns, they could then deduce Earth’s 24-hour rotation period, Ford said.

That done, the “E.T.” astronomers could infer that anomalies in the pattern were caused by changing weather patterns, most prominently, clouds, he said. Although some uninhabitable planets are extremely cloudy, the repeated presence and absence of clouds indicates active weather. On Earth, this variability results in water turning from gas to a vapor and back again, so finding similar variability on another planet would be a reasonable indication of liquid water.

“Venus is always covered in clouds. The brightness never changes,” Ford said. “Mars has virtually no clouds. Earth, on the other hand, has a lot of variation.”

Not only that, but observers could likely also infer the presence of continents and oceans from Earth’s changing light pattern.

The research will be useful to astronomers designing the next generation of space telescopes because it provides an outline of the capabilities required for studying the surfaces of Earth-like planets, Ford said. He said it appears that zeroing in on Earth-like planets orbiting the nearest stars would require a telescope at least twice the size of the Hubble Space Telescope. Ford said he hopes that his research will help to motivate an ever larger space telescope that could search for Earth-like planets around many stars.

The other authors of the paper are P. Montañés-Rodríguez and M. Vazquez, both of the Instituto de Astrofisca de Canarias in Spain, and Sara Seager, of the Massachusetts Institute of Technology. The IAC and UF are partners in the construction of the Gran Telescopio Canarias, a 10-meter telescope in the Canary Islands, which will start operations in 2008.

The research was funded in part by a Ramon y Cajal fellowship for Palle, by a Hubble fellowship and UF for Ford, and by a NASA grant for Seager.

MIT release | IAC release in Spanish | IAC release in English

The Gran Telescopio Canarias, or GTC, under construction in Spain’s Canary Islands for the past seven years, will hold its “first light” opening ceremony Friday. UF, which contributed $5 million to the project and owns a 5 percent share, is the only U.S. institution with a stake in the massive telescope.

“This is one of the largest international projects that the university is involved in, and first light is certainly a big step for a small department,” said Stan Dermott, astronomy department chairman and one of four UF astronomy faculty members who will attend Friday’s ceremony.

The roughly $175 million GTC is not yet complete. Only 12 of the 36 mirrors that together will compose its 34.1-foot primary mirror have been installed, Dermott said. The rest are expected to be mounted this year, with the telescope’s grand opening — to be presided over by King Juan Carlos I of Spain — set for next summer. Only after that date will scientific-quality observations begin.

All that said, enough of the mirror is assembled to allow telescope operators to make initial test runs, he said. So at 10 p.m. Greenwich Mean Time Friday (6 p.m. EDT), Prince Felipe, heir to the Spanish throne, will train the telescope on Polaris, the North Star, for a ceremonial observation to be attended by about 300 people.

Besides Dermott, the UF contingent will be astronomers Charlie Telesco, Rafael Guzman and Anthony Gonzalez, as well as Tom Walsh, UF director of sponsored research. “This will be the first demonstration that the telescope can produce a focused image of a star,” Dermott said.

The Spanish government is the main owner of the GTC, with UF and two institutes in Mexico as partners. As a result of its participation, UF astronomers will be allotted 20 nights of telescope time annually for observations. A UF-designed and built infrared imager and spectrometer, meanwhile, will be one of the first instruments mounted on the telescope when it opens for scientific observation next year.

“We are not just passive partners in this project,” Dermott said. “We are the world’s leader in developing astronomical instruments, and our instrument, CanariCam, will be one of the first instruments used on the GTC.”

Dermott said UF’s participation in the GTC effectively makes it one of a handful of institutions with guaranteed access to the world’s most powerful telescopes. That will open the door to a wide range of research not only at the GTC but elsewhere as well.

”Already we are forming scientific teams that will involve other telescopes to take part in surveys of the distant universe,” he said. “For example, Rafael Guzman is leading a team that will investigate the origin of galaxies. In a sense, we have joined the club of big observers now.”

Funded in part by the Spanish government with a $6.5 million grant, Guzman’s team of 40 astronomers from the U.S., Spain, France and England is conducting a survey called GOYA, or Galaxy Origins and Young Assembly. Other UF astronomers are also participating or heading GTC-related projects.

But University of Florida physicists have proposed a way to do just that, a step they say considerably improves the chance of detecting one of the universe’s most elusive particles, a candidate for the common but mysterious dark matter.

In a paper that appears online today in the journal Physical Review Letters, physicists at the University of Florida and Lawrence Livermore National Laboratory propose a redesign of the experiment currently being attempted in various forms by several groups of physicists worldwide. Although theoretical at the moment, they say their design could make such experiments a billion times more sensitive in their goal of detecting axions.

Axions are elemental particles whose confirmation would shed light on several different conundrums in particle physics. These could include pinning down the nature of dark matter, the mysterious substance said to make up 30 percent of the universe but so far observed only indirectly by its effects.

“A half dozen groups want to do this experiment, and some of them probably will try this approach,” said Pierre Sikivie, a faculty member in UF’s physics department and an author of the paper. “It works in principle, but in reality it will take some effort to set this up right so that it can produce a result.”

The unimproved experiment seeks to detect axions by shining a laser down the bore of a powerful superconducting magnet. A wall in the middle stops the laser cold, with the theoretical axions continuing through the wall and into the other side of the magnet. There, the magnet reconverts them into photons, or particles of light.

The detection of this light “reappearing” on the other side of the wall is what gives the experiment its iconic name.

Researchers in the U.S. and Europe are in various stages of conducting the experiment. The activity has been stimulated by a recent Italian experiment that claims to have discovered axion-like particles. The hope is to confirm the Legnaro National Laboratories’ results or take them a step further.

Sikivie, UF physics professor David Tanner and Karl van Bibber, a physicist at the Lawrence Livermore National Laboratory, propose a redesign of the “shining light through walls” experiment to make it, in their words, “vastly more sensitive.”

In a nutshell, they suggest placing pairs of highly reflective mirrors called Fabry-Perots cavities on both sides of the wall. The cavity on the laser light side of the wall would cause the light to bounce back and forth repeatedly, as though in an echo chamber. This action would produce many more of the hypothesized axions than a single beam of light, making them easier to detect on the other side of the wall.

“What happens is, because the light goes back and forth many times as it goes through the magnet, it produces more axions,” Sikivie said.

The Fabry-Perot cavity on the other side of the wall would perform a similar function, producing even more photons from the added axions.

Sikivie said researchers are doing separate experiments to detect axions produced by the sun, which would seem to be an easier approach because the sun is a much more powerful source than any laser. But the modified experiment would at least in theory have a higher sensitivity than these solar-based experiments.

“With these two cavities on both sides, it actually gets better, by a factor of 10 maybe, than the solar axion experiments,” he said.

A University of Florida astronomer is among more than three dozen astronomers who found the new large planets, announced today at the Transiting Extrasolar Planets Workshop at the Max Planck Institute for Astronomy in Heidelberg, Germany.

Stephen Kane, a UF postdoctoral associate, said he and his colleagues pinpointed the planets by detecting the slight dimming of starlight that occurs when the planets pass in front of their stars. Of about 200 planets discovered so far, the new planets are only the 13th and 14th to be found using this technique, called the transit method. But that’s likely to change quickly as the United Kingdom-based effort to discover planets with the transit method gathers steam, Kane said.

“We can expect these two planets to be the first in a wave of a whole lot of these new types of planets,” he said.

Known as “Hot Jupiters” because of their Jupiter-like size and temperature, the new planets are so close to their stars that they complete their orbit in a mere two and two-and-one-half days, respectively. That compares to 88 days for Mercury, the planet with the fastest orbit nearest the sun in our solar system. The very close orbit also means that the new planets are hotter than Mercury, which has a surface temperature of 752 degrees Fahrenheit. The planets are estimated to have a temperature of at least 3,272 degrees.

There is also evidence that the solar radiation from the stars is so intense that it is whipping away their atmospheres. “Hot Jupiters are assumed to have a significantly reduced lifetime due to their proximity to the star,” Kane said.

Most planets outside our solar system have been found using the radial velocity method, which measures the gravitational wobble in the star induced by the orbiting planet. The transit method would seem at first to be impractical because it requires a lucky break: The orbital plane of the planets under observation must be aligned toward Earth so astronomers can see the starlight dim as the planets pass.

The astronomers who discovered the two new planets dealt with this complication through, in Kane’s words, “brute force.” The astronomers surveyed millions of stars using twin telescopes snapping photos of the southern and northern skies from La Palma in Spain’s Canary Islands and Sutherland, South Africa. Each telescope is equipped with eight wide-angle cameras, each of which has a field of view of eight degrees, which comprises a relatively large chunk of the sky. By comparison, the full moon comprises about half a degree.

The work was done through UK’s leading planet detection program, a consortium of eight universities called SuperWASP, or Wide Angle Search for Planets.

Kane’s role in the research was to help pick out from the vast numbers of photographed stars the most likely candidates for further investigation. The job was a difficult one because planets passing in front of stars only slightly diminish the starlight, dimming it by only about 1 percent for just a few hours. Kane also led the research on the prototype for SuperWASP, and has worked on both SuperWASP telescopes, among other efforts.

“We have computer programs which are able to search all of these light curves from the stars and see if there’s something in them which looks like the star has become fainter for a short period, but it’s a complicated task,” Kane said.

After SuperWASP identified the tiny dips in starlight caused when the planets passed in front of their stars, a French-built instrument detected a slight wobble in each star’s motion as the planets passed around them, confirming the existence of the planets.

The planets are located in the constellations Andromeda and Delphinius, respectively. The Andromeda planet is more than 1,000 light years away, while the Delphinius planet is 500 light years away.

Both of the new planets are far too hot to support life. But Kane said their discovery adds to growing knowledge about how planets form, which should help astronomers understand and zero in on Earth-like planets.

“Once we understand planet formation, we’ll understand a lot more about how terrestrial planets form as well,” he said.

Source
Stephen Kane, skane@astro.ufl.edu, at conference in Germany:
(011) 49-6221-9130, Room 422

“It’s the most direct evidence that we have for dark matter,” said Anthony Gonzalez, an assistant professor of astronomy at the University of Florida and a member of the team of astronomers who made the discovery. “You can actually see the separation between where the bulk of the matter is and the normal everyday matter.”

These results are being published in an upcoming issue of The Astrophysical Journal Letters. The discovery was made with NASA’s Chandra X-ray Observatory and other telescopes.

Despite considerable evidence for dark matter, some scientists have proposed alternative theories for gravity where it is stronger on intergalactic scales than predicted by Newton and Einstein, removing the need for dark matter. However, such theories cannot explain the observed effects of this collision.

“A universe that’s dominated by dark stuff seems preposterous, so we wanted to test whether there were any basic flaws in our thinking,” said Doug Clowe of the University of Arizona at Tucson, leader of the study. “These results prove that dark matter exists.”

Gonzalez echoed Clowe, characterizing the results as raising a “significant challenge” to dark matter alternative theories.

In galaxy clusters, the “normal” matter, like the atoms that make up the stars, planets and everything on Earth, is primarily in the form of hot gas and stars. The mass of the hot gas between the galaxies is far greater than the mass of the stars in all of the galaxies. The galaxies and hot gas are bound in the cluster by the gravity of an even greater mass of dark matter. Without dark matter, which is invisible and currently can be detected only through its gravity, the fast-moving galaxies and the hot gas would quickly fly apart.

The team used about a week of Chandra time to observe the galaxy cluster 1E0657-556, which is also known as the “bullet cluster” because of a spectacular bullet-shaped cloud of extremely hot gas. The X-ray image shows that the bullet shape is due to a wind produced by the high-speed collision of a smaller cluster with a larger one.

Meanwhile, the Hubble Space Telescope, European Southern Observatory’s Very Large Telescope and Magellan optical telescopes were used to determine the location of the mass in the clusters. This was done using a technique known as gravitational lensing, where gravity from the clusters distorts light from background galaxies as predicted by Einstein’s theory of general relativity.

Gonzalez assisted in the analysis of the Hubble Space Telescope images and otherwise contributed to the optical data analysis.

The hot gas in this collision was slowed by a drag force, similar to air resistance. In contrast, the dark matter was not slowed by the impact because it does not interact directly with itself or the gas except through gravity. This produced the separation of the dark and normal matter seen in the data. If hot gas were the most massive component in the clusters, as proposed by alternative gravity theories, such a separation would not be seen. Instead, dark matter is required.

“This is the type of result that future theories will have to take into account,” said Sean Carroll, a cosmologist who was not involved with the study. “As we move forward to understand the true nature of dark matter, this new result will be impossible to ignore.”

This result also gives scientists more confidence that the Newtonian gravity familiar on Earth and in the solar system also works on the huge scales of galaxy clusters.

“We’ve closed this loophole about gravity, and we’ve come closer than ever to seeing this invisible matter,” said Clowe.

NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency’s Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center, Cambridge, Mass.

Additional information and images can be found at: http://chandra.harvard.edu and http://chandra.nasa.gov.

Other scientists involved in the research include Marusa Bradac of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC); Dennis Zaritsky of the University of Arizona’s Steward Observatory; Maxim Markevitch, Scott Randall, Christine Jones and William Forman of the Harvard-Smithsonian Center for Astrophysics, Tim Schrabback of the University of Bonn, and Phil Marshall of KIPAC. Support for this work was provided by the National Science Foundation and NASA. This project was also partially supported by the Department of Energy through the Stanford Linear Accelerator Center.

GAINESVILLE, Fla. — Astronomers from Spain, Mexico and the United States will gather in Miami next week to plan for the first observations of the world’s largest telescope – a $160 million behemoth under development for the past six years on Spain’s Canary Islands.

As many as 150 astronomers from the partner institutions in the Gran Telescopio Canarias or GTC – the University of Florida, two universities in Mexico and several Spanish institutions — will meet in Coral Gables starting Tuesday to plan the telescope’s first observations, expected late next year.

The highlight of the weeklong “First Light Science with the GTC” conference will be a reception, to be attended by UF President Bernie Machen, U.S. and Mexican officials and astronomers, Thursday evening at the Biltmore Hotel in Coral Gables.

Members of the media are invited to the event, which will feature speeches and presentations by Machen and other dignitaries, as well as leading astronomers. There will also be a detailed scale model of the GTC on display, as well as a live video tour of the telescope on the Canary Islands off Africa’s west coast.

A 5 p.m. lecture on the history of astronomy in Spain and the Americas will precede the cocktail reception, which begins at 6 p.m. Presentations and the guided video tour will follow from 7 to 8 p.m. The Biltmore is at 1200 Anastasia Ave., Coral Gables.

When the GTC is completed, the telescope will have a 10.4 meter, or 34.1 foot, primary mirror, the largest mirror of any optical telescope in the world. That will give it unprecedented power to peer into the heavens — the equivalent of the ability to see the edge of a dime from two miles away, said UF astronomy professor Charlie Telesco. That means the telescope will be able to spot both extremely faint objects, such as dim planets orbiting bright stars, and very distant ones, such as galaxies millions of light years away.

Because of the time it takes for light to travel, the most distant objects are also the oldest, and the GTC will be able to peer back to when the 13-billion-year old universe was just 7 percent of its current age, or 900 million years old, Telesco said. That will significantly enhance astronomer’s understanding of the origins of galaxies, stars and planets, he said.

“When we add all the pieces together, we can weave a fabric that can begin to describe the universe,” he said.

The Universidad Nacional Autónoma de México and the Instituto Nacional de Astrofísica, Óptica y Electrónica in Mexico, as well as the Instituto de Astrofisca de Canarias in Spain, are among the GTC’s other partners. The international element is important because it represents a unique opportunity for Florida to build a top telescope program, said Stan Dermott, professor and chairman of the UF astronomy department.

“A single university like UF does not have the financial resources to build a giant telescope or the complex instruments that go with it on its own,” Dermott said. “We can only participate in world-class astronomy and space science through collaboration.”

Dermott noted that the GTC endeavor represents a renewal of ties between countries with traditions in astronomy. Spain was a leading center of astronomy in the era leading up Columbus. Indeed, Spanish astronomers warned Columbus that his estimate of the distance to India was far too low, a warning that proved correct when he stumbled on America en route, said Steve Eikenberry, a UF astronomer. Meanwhile, indigenous people in pre-Columbian Mexico were finely attuned to astronomical calendars and events, he said.

“The Maya in particular in Mexico had very advanced astronomical science,” Eikenberry said. “They built their cities around astronomical orientations and had accurate calendars.”

He and UF astronomy Professor Rafael Guzman will cover that and other elements of the history of Hispanic astronomy leading up to the GTC in their lecture Thursday prior to the reception. “There are significant historical roots for the GTC project,” Eikenberry said. “Today, Hispanic astronomy is seeing a tremendous upsurge and the University of Florida is very much at the epicenter of a lot of that activity.”

Besides the participants, sponsors of the conference include the National Science Foundation, the Greater Miami Convention & Visitors Bureau, the Canary Islands Foundation and Schott, the manufacturer of the glass used in the mirror.

En Español:
Astronomos se reunen en Miami en torno al telescopio mas grande del mundo

The team of astronomers from the University of Florida, NASA’s Jet Propulsion Laboratory and the Lawrence Livermore National Laboratory has found nearly 300 new galaxy clusters and groups, including nearly 100 at distances of eight to 10 billion light years. The new sample, a six-fold increase in the number of known clusters and groups at such extreme distances, will allow astronomers to study very young galaxies two-thirds of the way back to when the universe is believed to have originated in the Big Bang.

The team will present its findings today in Calgary, Canada, at the American Astronomical Society’s biannual meeting.

Anthony Gonzalez, an assistant professor of astronomy at UF and one of the team of astronomers who made the discovery, likened the view of the clusters to a glimpse at the Los Angeles basin when it was still home only to a collection of dusty, small towns. By knowing what the clusters looked like eight to 10 billion years ago, the astronomers will have a better idea of where and when the first stars and galaxies formed and how they grew and changed over the universe’s full 13.7 billion- year lifespan.

“It would be like taking a snapshot of cities as they were near the beginning,” he said. “You’re watching everything fall together, so you can see some of the pieces, some of the little towns, before they become part of a giant city.”

Galaxy clusters are among the universe’s most dense places, similar to cities on Earth, and a single galaxy cluster can contain hundreds of large galaxies similar to our Milky Way.

The most massive, oldest galaxies tend to be found in galaxy clusters. This makes clusters the best place to look to determine when the first stars formed and how these galaxies grew with time. While individual galaxy clusters have previously been found at similar distances, this is the first time that such a large number of galaxy clusters has been detected so far away.

Gonzalez said the astronomers’ key step in finding the large number of clusters was to merge infrared data from NASA’s Spitzer Space telescope with existing deep optical imaging obtained by National Optical Astronomy Observatory Deep Wide-Field Survey team at Kitt Peak National Observatory in Arizona.

The team used the Spitzer telescope to make infrared mosaics, a process that was thousands of times faster than with the biggest ground-based telescopes because of the Spitzer telescope’s unique capabilities. The combined Kitt Peak and Spitzer data provided information on the distances to the galaxies, enabling the astronomers to weed out small, nearby galaxies whose light was cluttering the view between the observers and the most distant clusters. Gonzalez’s main role was to analyze the maps of massive galaxies and detect the hidden galaxy clusters.

“We’re basically getting rid of all the junk to isolate the most distant, massive galaxies,” Gonzalez said.

The research will allow astronomers to embark on several new studies, said Mark Brodwin, an astronomer at the Jet Propulsion Laboratory and a co-investigator on the team.

“Clusters of galaxies are the repositories of the most massive galaxies in the universe,” he said. “As such, our survey serves as an ideal laboratory in which to study the process of massive galaxy formation over the last two-thirds of the lifetime of the universe.”

The next step is to study the newly discovered galaxies in detail, Brodwin said. Astronomers want to learn more about their size, shape, mass and the rate at which they form new stars and merge together to form larger galaxies. “These key measurements will improve our fundamental understanding of the galaxy formation process,” he said.

NASA’s Jet Propulsion Laboratory, based in Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. JPL is a division of Caltech.

Researchers, including a University of Florida astronomer, found the planet, which has a mass about five times that of Earth, orbiting a small star near the center of the galaxy in the constellation Sagittarius.

Located about three times as far away from its star as the distance from Earth to the sun, it is probably too cold to support life. But its presence suggests there are many other small planets orbiting the star. That makes it likely that at least some are located in the so-called habitable zone, the region around stars where temperatures are moderate enough for liquid water to appear on their surfaces.

“The good thing about this is it shows that planets this size might be quite common in habitable zones,” said Stephen Kane, a postdoctoral associate in UF’s astronomy department.

Kane co-authored a paper about the discovery set to appear Jan. 26 in the journal Nature.

Since the first planet was discovered outside our solar system in 1992, astronomers have found the vast majority of the 160-plus planets so far with a technique called radial velocity. The technique detects planets that are too faint to be seen with visual telescopes by observing the wobble in the stars induced by the orbiting planet.

Bigger planets have more gravitational pull, inducing bigger, more detectable wobbles. Also, the closer planets lie to the star, the more wobble they cause. As a result, radial velocity tends to turn up the largest, closest, hottest and consequently the most gaseous planets – planets, in other words, that are not good candidates for supporting life.

Astronomers discovered the new, small planet by tapping a completely different stellar phenomenon: galactic microlensing. Most easily observed with small, older stars known as M dwarfs, microlensing occurs when light from a distant star encounters the gravitational field of a closer star as the closer star passes in front or just to the side it. The gravitational field literally bends and magnifies the light.

The effect is a bit like the beam from a searchlight encountering a giant magnifying glass. But, for planet-finders, the key item of interest is that if the parent star is orbited by a planet, the planet’s gravitational field also acts as its own little lens — magnifying some of the distant star’s light in a brief but distinctive flicker.

“There’s a very subtle effect, a spike, and that’s what we’re looking for,” Kane said.

It’s rare for one star to pass so near another star that it causes microlensing to occur. The timing is also brief, with most microlensing events lasting 30 days or less. As a result, astronomers hunting such events focus their searches on the center of the galaxy, where stars are most densely distributed. This area is best viewed from the Southern Hemisphere, so astronomers coordinate observations using multiple telescopes in such places as Australia, Chile, South Africa and the Canary Islands.

“We have a real-time alert system,” Kane said. “We’ve got people in Australia observing, and if they see something strange happen but their source is starting to set, they call up South Africa and say, ‘Something’s happening here. Point your telescopes at this.’”

In the latest finding, some 73 astronomers affiliated with three independent groups coordinated observations of a microlensing event first identified on July 11, 2005. Nearly a month later, on Aug. 9, the astronomers observed “a short duration deviation from a single-lens light curve … due to a low-mass planet orbiting the lens star,” the Nature paper says.

The planet is at the outer edge of the zone where it can be seen. With a surface temperature below 350 degrees below zero, it is probably rocky and icy. Even if conditions appeared more favorable for life, its location would make it tough to learn more: The planet is located 7,000 parsecs, or nearly 23,000 light years, from Earth.

That said, M dwarfs are the most common type of stars in the galaxy. The fact that microlensing uncovered such a small planet around one M dwarf suggests that there are likely many others, possibly with better conditions, Kane said.

“This has huge implications for finding life,” he said.

The feat suggests that astronomers have found a way to dramatically accelerate the pace of the hunt for planets outside our solar system.

“In the last two decades, astronomers have searched about 3,000 stars for new planets,” said Jian Ge, a professor of astronomy at the University of Florida. “Our success with this new instrument shows that we will soon be able to search stars much more quickly and cheaply – perhaps as many as a couple of hundred thousand stars in the next two decades.”

Ge and colleagues at the University of Florida, Tennessee State University, the Institute of Astrophysics in Spain’s Canary Islands, Pennsylvania State University and the University of Texas presented their findings today at the American Astronomical Society’s annual meeting in Washington, D.C.

Their work is important in part because of what the astronomers found – a planet, at least half as massive as Jupiter, orbiting a star just 600 million years old. That’s very young compared, for example, with the sun’s 5 billion years.

“This is one of the youngest stars ever identified with a planetary companion,” Ge said. Perhaps more significant, the instrument used to find the planet points the way to a much more accessible method for finding others — including those capable of supporting life.

Planets outside our solar system are typically swamped by the light of their stars, making it difficult to observe them visually. In the 1990s, astronomers began using a measurement technique called Doppler radial velocity to detect planets by observing the wobble in a star that is gravitationally induced by an orbiting planet.

This technique, which has uncovered the vast majority of the 160-plus extrasolar planets found so far, works by hunting through the spectrum of starlight for the subtle Doppler shifts that occur as the star and planet move toward and away from their common center of mass. The instrument at the heart of this technique is usually a spectrograph, but this instrument is problematic.

“A major problem with spectrographs is that they collect only a small percentage of photons from the target light source, which means that they are only useful to search for distant planets when mounted on relatively large telescopes,” Ge said.

The astronomers’ new instrument, the Exoplanet Tracker, or ET, eliminates this problem by swapping the spectrograph with an interferometer, a device that can take more precise radial velocity measurements. Tests show the interferometer can capture as much as 20 percent of available photons, making the instrument far more powerful, which opens its use for distant planet hunting to smaller telescopes.

At a development cost of about $200,000, the interferometer-equipped ET is also far cheaper than comparable spectrographs, which cost more than $1 million. And at about 4 feet long, 2 feet wide and weighing about 150 pounds, it is lighter and smaller. The instrument is based on a concept first proposed in 1997 by Lawrence Livermore National Lab physicist David Erskine.

The astronomers used the Exoplanet Tracker on the special 0.9-meter Coudé feed system within the National Science Foundation’s 2.1-meter telescope at Kitt Peak National Observatory near Tucson, Ariz.

Like radial velocity instruments equipped with spectrographs, the ET instrument in its present form can search only one object at a time. But Ge’s team has demonstrated that it can hunt for planets around multiple stars simultaneously – a key element of its heightened utility. The team is working on a version capable of surveying as many as 100 stars simultaneously.

The Exoplanet Tracker will be used next spring for a trial planet survey on the Sloan Digital Sky Survey 2.5 meter wide-field telescope at the Apache Point Observatory in New Mexico. The new instrument is funded with an $875,000 grant from the W.M. Keck Foundation. A much more ambitious, long-term survey is in the planning stages.

The Kitt Peak Coudé feed telescope that Ge and colleagues used to discover the new planet has a 0.9-meter mirror on a tall tower, a mirror that directs incoming starlight into an observing room in the base of the 2.1-meter telescope. The standard spectrograph in the facility fills the room — while ET occupies a small corner.

The new planet is the most distant ever found using the Doppler technique with a telescope mirror less than 1 meter in size. There are hundreds of such telescopes worldwide, compared with just a handful of the larger 2- and 3-meter telescopes more commonly used in planet finding – telescopes that tend to be in extremely high demand and difficult to access.

“These smaller telescopes are relatively cheap and relatively available,” Ge said, “so you can often get access to many dozens of nights on them if you have a promising proposal.”

Kitt Peak National Observatory is part of the National Optical Astronomy Observatory, Tucson, Ariz., which is operated by the Association of Universities for Research in Astronomy Inc., under a cooperative agreement with the National Science Foundation.

“This is the first time that a planet has been discovered using a publicly funded telescope at the U.S. national observatory,” said Buell Jannuzi, acting director of Kitt Peak National Observatory. “We are very excited that the broader community of astronomers around the world will be able to propose to use the single-object Exoplanet Tracker instrument at Kitt Peak to carry out their own research programs, starting in the fall of 2006.”

That said, discovering new planets is never easy.

In the latest find, astronomers went to great lengths to ensure they were actually “seeing” a planet. That’s because the star, which has about 80 percent of the mass of our sun, retains much of its youthful rotation speed, which makes it capable of generating strong magnetic fields and associated dark star spots. These are similar to the magnetically generated sunspots on our own sun, and they can mimic the presence of a planet in orbit around the star.

To check against this possibility, Greg Henry, an astronomer at Tennessee State, observed the star with an automated telescope in Arizona, and found the star to be changing its brightness as it rotates.

“My observations reveal a rotation period of about 12 days for the star,” Henry said. “Thus, if the planetary orbital period is indeed less than five days, the dark spots rotating around on the surface of the star every 12 days cannot be causing the false appearance of a planet.”

Located in the direction of the constellation Virgo, the newly discovered planet completes its orbit in less than five days, meaning it orbits very close to its parent star and is very hot. That means it’s too close to the star to lie within the “habitable zone” where life is possible.

Relying on observations from the Gemini South telescope in Chile, the University of Florida-led team has concluded that differences in brightness in the dust disc surrounding a star known as Beta Pictoris stem from an extra bright clump on one side of the disc. This clump, the astronomers say, is composed of dust particles that are consistently smaller than particles elsewhere in the disc – likely evidence of a collision of two massive asteroids or tiny developing planets known as planetismals that may have occurred as recently as in the past few decades.

An article about the discovery is set to appear Jan. 13 in the journal Nature.

“What we’re proposing is that a planetesimal – either a very small planet or a very large asteroid — has collided with another similar object and has been catastrophically destroyed,” said Charlie Telesco, a UF astronomy professor and the paper’s lead author. “It’s a cloud now, but what we’re proposing is that this cloud represents the debris of a major collision.”

The findings are of interest because they suggest a new explanation for a phenomenon — asymmetries or lopsided appearances in star dust discs — that has long puzzled astronomers, Telesco said. The results also continue to help refine the evolving science of planet-finding, an endeavor that has turned up more than 100 planets outside our solar system since the first was discovered in 1995.

Stars are thought to form when gravity causes a rotating cloud of gas to contract. Before the actual star is formed, the gas collapses into a rotating disk of gas and dust particles ranging in size from tiny grains to household-sized dust to rocks and boulders. Astronomers had long predicted that some of this material may coagulate into planets as it rotates around the core, but Beta Pictoris, first detected by the Infrared Astronomy Satellite in 1983, was the first such “circumstellar” star to be imaged.

Beta Pictoris is about 63 light years from Earth in the southern constellation known as Pictor, or Painter’s Easel. It barely clears the horizon on the southern edges of the Northern Hemisphere, where it is seen most easily from Hawaii.

Like other planet-forming stars, Beta Pictoris, which is between 10 million and 20 million years old, is extremely young by stellar standards, with mature stars living billions of years. Also like some other young stars, it has an attribute that has long proved puzzling to astronomers: One side, or “wing,” of the star’s 200-billion-mile diameter dust disc is both brighter and longer than the other.

Some astronomers theorized that this anomaly was caused by the presence of a large planet orbiting the star. But the UF-led team came to a different conclusion after observing Beta Pictoris during six nights in December 2003 and last January using the Gemini telescope. The telescope had been specially equipped with a UF-designed and -built observational camera called the Thermal Region Camera and Spectograph, or T-ReCS, according to Telesco.

T-ReCS allows astronomers to detect faint sources of thermal or infrared radiation by isolating them from the far more powerful and more obvious radiation generated by the Earth’s atmosphere, the telescope and the star itself.

“We’re able to see sources that are at least a million times fainter than the background,” Telesco said. “It’s like trying to detect a match when you’re actually holding the match up to the sun.”

What Telesco characterized as “the most complete and the best resolution imaging at multiple wavelengths” of the star revealed that the wing’s brightness stemmed from a “knot” of emissions, or clump. Further examination showed this clump contained a higher concentration of smaller, finer dust particles than elsewhere, suggesting a violent and recent collision of asteroids or tiny planets.

“Many of us remember pounding chalk dust out of erasers at school,” said Scott Fisher, an astronomer at Gemini South and a co-author of the Nature paper. “After you sneeze a few times, you open a window and the fine dust blows away. In Beta Pictoris, the radiation from the star should blow away the fine particles from the collision quite rapidly. The fact that we still see them in our observations means that the collision probably happened in the past 100 years or so.”

An alternative explanation of the clump may be the “collisional grinding” of two planets located closely together in orbit, Telesco said. “Over time, the planets bang into each other, and when they do they actually produce debris,” he said.

The findings suggest a possible explanation for other observed lopsided discs, Telesco said. They also may help astronomers weed out planets from other possible sources of brightness.

“One of the problems for astronomers is if there are clumps in the disc associated with planetismals, it’s hard to tell the difference between those clumps and a planet,” he said. “So we’re hoping to use these results to understand how we can distinguish these structures from planets until the time comes when we have sensitivity to see the planet itself.”

Besides Telesco, the other UF authors of the paper are Stan Dermott, professor and chairman of the astronomy department; Thomas Kehoe, an assistant scientist; Steven Novotny, a recent UF graduate; Naibl Mariñas, a graduate student; James Radomski, a postdoctoral research associate; and Christopher Packham, an assistant scientist.

A team of scientists led by a University of Florida astronomer analyzed a sample of galaxies located 100 million light years away and discovered the number of violent encounters between large galaxies is one-tenth the number that earlier studies had suggested.

Although theoretical models had predicted fewer collisions were involved in the evolution of the universe, these are the first observational measurements confirming those assumptions, said UF astronomer Alister Graham, who will present the results Tuesday at the American Astronomical Society meeting in Denver. The research was funded by NASA through a grant from the Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy.

“The new result is in perfect agreement with popular models of hierarchical structure formation in our universe,” said Graham, a faculty scientist at the University of Florida and the Australian National University in Canberra. “Galactically speaking, things appear a little safer out there.”

For years, astronomers have known the collision and merger of galaxies resulted in the formation of larger galaxies. The biggest of these new-formed galaxies appear largely devoid of stars at their cores, a phenomenon believed to result from the damage caused by “supermassive” black holes from the smaller galaxies as they merge at the center of the new galaxy. These huge black holes, a billion times heavier than the sun, act like a giant gravitational slingshot, ejecting stars away from the galaxy cores. These black holes also have been known to devour stars that venture too near.

Together with Peter Erwin, of the Spanish Instituto de Astrofiscia de Canarias in the Canary Islands, and Ignacio Trujillo, of the Max Planck Institute for Astronomy in Germany, Graham used this deficit of core stars as a gauge to determine the number of collisions that created the large galaxies.

Prior measurements in similarly sized elliptical galaxies suggested they had been formed by eight to 10 major collisions not involving the formation of new stars, but Graham’s team arrived at a much different conclusion.

Using images from Hubble’s Wide Field Planetary Camera 2, the researchers were able to examine galaxies whose cores had not been depleted of stars. The technique allowed the astronomers to observe what the central stellar distributions looked like before any major collisions had occurred, enabling them to better reconstruct the loss of stars from the galaxies which had partially depleted cores.

In addition, by considering the overall galaxy structure, they were able to more accurately measure the mass and size of the galaxies’ centrally depleted regions, which typically ranged from 300 to 900 light years across. The result: The mass of the deficit of stars at the galaxies’ centers, on average, equaled rather than exceeded the mass of the black hole. “If there had been 10 mergers, we would have found a stellar deficit 10 times the mass of the central black hole,” Graham said.

“It’s important to realize that many galaxies have large central black holes but no depleted cores. It is therefore not the case that every black hole is formed by simply gobbling up its surrounding stars. Instead, we are observing the demolished cores of galaxies after the union of two massive cosmic wrecking balls,” he said.

Although small satellite galaxies have been captured by our galaxy, the Milky Way, it has not experienced a recent major merger, Graham said. If it had, the plane of its disk, visible as a faint wide ribbon in the night sky, would have been scattered and dispersed across the heavens. Such a fate is expected in about 3 billion years when the Milky Way collides with a neighboring spiral galaxy, Andromeda, he said.

Graham said he plans to expand his research by applying his method of analysis to more galaxies, and also will use Hubble’s Advanced Camera for Surveys, which will provide a wider field of view and enhanced sensitivity.

“This work nicely quantifies the amount of ‘damage’ that supermassive black holes do to galaxy cores during galaxy mergers,” said astrophysicist David Merritt, a professor at the Rochester Institute of Technology. “Previous work in this area had been hampered by a lack of knowledge of the initial (pre-merger) state. The new results are nicely consistent with the merger paradigm for galaxy formation, and with the observed masses of SMBHs (supermassive black holes) in galaxies. This work should motivate further simulations of galaxy mergers in order to pin down the precise effects of SMBHs on galaxy luminosity profiles.”

But don’t expect to find the star — which is at least 5 million times brighter than the sun — in the night sky. Dust particles between Earth and the star block out all of its visible light. Whereas the sun is located only 8.3 light minutes from Earth, the bright star is 45,000 light years away, on the other side of the galaxy. It is detectable only with instruments that measure infrared light, which has longer wavelengths that can better penetrate the dust.

In a National Science Foundation-funded study scheduled to be presented today at the American Astronomical Society national conference in Atlanta, the team says the star is at least as bright as the Pistol Star, the current record holder, so named for the pistol-shaped nebula surrounding it. Whereas the Pistol Star is between 5 million and 6 million times as bright as the sun, however, the new contender, LBV 1806-20, could be as much as 40 million times the sun’s brightness.

“We think we’ve found what may be the most massive and most luminous star ever discovered,” said Steve Eikenberry, a UF professor of astronomy and the lead author of a paper on the discovery that was recently submitted to the Astrophysical Journal.

Eikenberry will discuss his findings in a news conference to be held by the society at 12:30 p.m. today at the Courtland Room in the Hyatt Regency Atlanta, where the conference is being held.

One longstanding problem with gauging the brightness of stars at great distances is that what seems at first to be one amazingly bright star turns out on closer examination to be a cluster of nearby stars. Don Figer, an astronomer at the Baltimore-based Space Telescope Science Institute who led the team that discovered the Pistol Star in 1997, said the high-quality data collected by the UF-led team reduced but did not eliminate this possibility.

“The high-resolution data prove that the object is not simply a cluster of lower mass stars, although it is possible that it is a collection of a few stars in a tight orbit around each other,” Figer said. “More study will be needed to determine the distance and singularity of the object in order to establish whether the object is truly the most massive star known.”

Astronomers have known about LBV 1806-20 since the 1990s. At that time, it was identified as a “luminous blue variable star” - a relatively rare, massive and short-lived star. Such stars get their names from their propensity to display light and color variability in the infrared spectrum.

Luminous blue variable stars are extremely large, with LBV 1806-20 probably at least 150 times larger than the sun, Eikenberry said. The stars are also extremely young by stellar time. LBV 1806-20 is estimated at less than 2 million years old. The sun in our solar system, by contrast, is 5 billion years old. Typical stars, such as the sun, live 10 billion years.

LBVs have “short and troubled lives,” as Eikenberry put it, because “the more mass you have, the more nuclear fuel you have, the faster you burn it up. They start blowing themselves to bits.”

Eikenberry’s team made several key advances that led to the estimate of the star’s oversized mass and brightness, he said.

One, they sharpened infrared images obtained from the Palomar 200-inch telescope at the California Institute of Technology’s Palomar Observatory using a camera equipped with “speckle imaging,” a relatively new technology for improving resolution of objects at great distances.

“The shimmering that you see coming off a hot blacktop road in the summer - the upper atmosphere kind of does that with star light,” Eikenberry said. “Speckle imaging kind of freezes that motion out, and you get much better images.”

Composed of 17 astronomers and graduate students, the team also came up with an accurate estimate for the distance from the Earth to the bright star. Team members further determined its temperature and how much of the star’s infrared light gets absorbed by dust particles as the light makes its way toward Earth. The scientists relied on data collected by the Blanco 4-meter telescope at the National Optical Astronomy Observatory’s Cerro Tololo Inter-American Observatory in Chile.

Each of these variables contributed to the estimate of the star’s remarkable candlepower. “You correct for dust absorption, then you correct for temperature of the star, you correct for distance of the star - all of those things feed into luminosity,” Eikenberry said.

One of the mysteries about LBV 1806-20 is how it got so big. Current theories of star formation suggest they should be limited to about 120 solar masses, or 120 times as large as the sun, because the heat and pressure from such big stars’ cores force matter away from their surfaces. Eikenberry said one possibility is that the big star was formed in a process called shock-induced star formation, which occurs when a supernova blows up and slams the gaseous material in a molecular cloud together into a massive star.

The star’s size is not its only distinguishing characteristic. It is located in a small cluster of highly unusual or extremely rare stars, including a so-called “soft gamma ray repeater,” a freakishly magnetic neutron star that is one of only four identified in the entire galaxy of 100 billion stars. With a magnetic field hundreds of trillions of times more powerful than Earth’s magnetic field, this type of star gets its name from its periodic bursts of gamma rays. The cluster also apparently includes an infant or newly formed star.

“We’ve got this zoo of freak stars, all crammed together, really nearby, and they’re all part of the same cluster of stars,” Eikenberry said. “It’s really kind of weird.”

Also buried within the cluster is an extremely young infant star, Eikenberry said. The presence of the infant star, the luminous blue variable and the soft gamma ray repeater are vivid examples of an important emerging fact about stellar evolution: All stars in a single cluster don’t form at the same time, he said. “We’re seeing what I think is going to become a textbook example of the fact that stars aren’t all born in an instant, even in a small cluster,” he said.

Figer, the Pistol Star discoverer, said the research makes an important contribution to astronomers’ understanding of the star formation process.

“The findings are significant because such massive stars are very rare and define the upper limits of the star formation process,” he said. “The team has made a remarkable contribution to our understanding of the most extreme stars.”

The team carrying out this work also included UF’s Jessica LaVine; Keith Matthews, with the California Institute of Technology; Stephane Corbel, with the Universite de Paris; John-David Smith, with the University of Arizona; John Wilson, with the University of Virginia; Donald Barry, Michael Colonno and James Houck, all with Cornell University; and undergraduate research students Shannon Patel, Malia Jackson, and Dounan Hu of Cornell University; and Megan Garske of Northwestern Nazarene University.