Category: Astronomy

An amateur astronomer has discovered what could be a new object orbiting the Earth; maybe it’s a recently captured space rock, or maybe it’s just a remnant from the Apollo program. Whatever it is, the object, dubbed J002E2, seems to orbit the Earth every 50-days in a wide orbit. If it turns out to be natural, the object will become the Earth’s 3rd moon (and you only thought we had one), after Cruithne which was discovered in 1986 in a long erratic orbit. (BBC News Story)

Image credit: SWRI

Although the Kuiper Belt, a region of icy objects located past the orbit of Neptune, was only discovered in 1992, it’s already presented a host of mysteries. One mystery is why an unusually large number of these objects have small satellites orbiting them – 8 out of the 500 objects discovered so far have had satellites. The high number brings into question the traditional theory that they’re caused by collisions.

The Kuiper Belt region of the solar system, which stretches from just past Neptune to beyond the farthest reaches of Pluto?s orbit, was only discovered in 1992, but continues to reveal new knowledge into the formation processes of the planets. Now, in a paper to be published in the October issue of The Astronomical Journal, a Southwest Research Institute? (SwRI?) scientist reveals a new mystery about Kuiper Belt Objects (KBOs).

The study examined the formation of KBO satellites, which have been observed only since 2001 and continue to be discovered around an unexpectedly large number of the more than 500 known KBOs.

?In just over a year since the first satellite of a KBO was found, scientists have discovered a total of seven KBO satellites. Surprisingly, observations by both ground-based telescopes and the Hubble Space Telescope have indicated that, in many cases, the KBO satellites are as large or nearly as large as the KBOs around which they orbit,? says Dr. S. Alan Stern, director of the SwRI Space Studies Department. ?That so many binary or quasi-binary KBOs exist came as a real surprise to the research community.?

The focus of Stern?s work was not observational in nature, but rather it sought to understand how such large KBO-satellite pairs could form. The standard model for large satellite formation is based on collisions between an interloping body and the parent object around which the satellite orbits. This model has successfully explained binary systems around asteroids and the Pluto-Charon system, and also has direct relevance to the formation of the Earth-moon system.

Stern?s findings call into question the formation of KBO satellites by standard collisional processes. Collisions of the magnitude required, Stern found, appear to be energetically improbable, given the number and masses of potential impactors in both the ancient (more massive) and modern day (eroded) Kuiper Belts.

This likely implies one of two alternatives: Either KBO satellites were not formed by collisions, as has been commonly assumed, or the surface reflectivities (which help determine size) of KBOs with satellites, or the reflectivity of the satellites themselves, have been significantly underestimated.

?If the surfaces of KBOs with satellites, or the satellites themselves, are more reflective than previously thought,? says Stern, ?these objects would be smaller and less massive, and would therefore require smaller, less energetic impacts to create the satellite systems we see.?

NASA?s new Space Infrared Telescope Facility (SIRTF), set for launch early next year, will help resolve these two alternatives, Stern says, by directly measuring the reflectivities and sizes of numerous KBOs, including those with satellites.

In addition to this work, Stern serves as principal investigator of the NASA New Horizons mission to Pluto and the Kuiper Belt. Expected to launch in January 2006, this spacecraft will make the first ever flyby reconnaissance of the Pluto and Charon system and then go on to explore KBOs as it leaves the solar system. New Horizons is the only NASA mission planned to study Kuiper Belt Objects at close range.

The NASA Origins of Solar Systems program provided funding for this research.

Original Source: SWRI News Release

Image credit: Hubble

Astronomers have spotted a number of young stellar clusters dotted around a very old elliptical galaxy – this disputes the established theory that old galaxies contain only older stars. The team used the Hubble Space Telescope and the ESO Very Large Telescope to take a series of images of galaxy NGC 4365, and they were able to identify star clusters that were only a few billion years old, while the majority were over 12 billion years old. Why the galaxy contains such a combination of young and old stars is still a mystery.

Combining data from the NASA/ESA Hubble Space Telescope and the ESO Very Large Telescope (VLT), a group of European and American astronomers have made a major discovery. They have identified a huge number of ‘young’ stellar clusters, in an old elliptical galaxy.

For the first time, it has been possible to identify several distinct periods of star formation in a galaxy as old as this one. Elliptical galaxies have always been considered to have undergone one early star-forming period and thereafter to be devoid of star formation. However, the combination of the best and largest telescopes in space and on the ground has now clearly shown that there is more than meets the eye.

Do elliptical galaxies only contain old stars?
One of the challenges of modern astronomy is to understand how galaxies – large systems of stars, gas and dust – form and evolve. When did most of the stars in the Universe form? Did this happen at a very early stage, within a few billion years of the Big Bang? Have a significant number of the stars we now observe formed much more recently?

Spectacular collisions between galaxies take place all the time, triggering the formation of thousands or even millions of stars. However, when looking at the Universe as a whole, most of its stars are found in elliptical galaxies whose overall appearance has so far led us to believe that they, and their stars and as well, are old.

These elliptical galaxies do shine with the diffuse, reddish glow normally associated with stars that are many thousand million years old. However, what is the underlying mix of stars that produces this elderly appearance? Could a significant number of much younger stars be ‘hiding’ among the older ones?

Detailed observations with the world’s premier telescopes have now cast new light on this central question about the behaviour of some of the major building blocks of the Universe.

Cosmic paleonthology
To break the stellar ‘cocktail’ in elliptical galaxies down into its different constituents, a team of European and American astronomers observed massive stellar clusters in and around nearby galaxies. These “globular” clusters, so called because of their shape, exist in large numbers around all observed galaxies and form a kind of ‘skeleton’ within their host galaxies. These ‘bones’ receive an imprint for every episode of star formation they undergo. By reading the ages of the globular clusters in a galaxy, it is possible to identify the past epoch(s) of active star formation in a galaxy.

Reading the imprints and deducing the distribution of ages of the globular clusters, astronomers can reveal when many of the stars in elliptical galaxies formed. This is similar to the way a palaeontologist uses the skeletons of dinosaurs to deduce information about the era in which they lived.

A surprising discovery
The team combined images of a number of galaxies from Hubble’s Wide Field and Planetary Camera 2 with infrared images obtained from the multi-mode ISAAC instrument on the 8.2m VLT Antu telescope at the ESO Paranal Observatory (Chile). To their great surprise, they discovered that many of the globular clusters in one of these galaxies, NGC 4365, a member of the large Virgo cluster of galaxies, were only a few thousand million years old, much younger than most of the other stars in this galaxy (roughly 12 thousand million years old).

The astronomers were able to identify three major groups of stellar clusters. There is an old population of clusters of metal-poor stars, some clusters of old but metal-rich stars and now, seen for the first time, a population of clusters with young and metal-rich stars.

These results have been fully confirmed by spectroscopic observations made with another of the world’s giant telescopes, the 10-metre Keck on Hawaii.

“It is a great pleasure to see two projects wholly or partly funded by Europe – VLT and Hubble – work in concert to produce such an important scientific result”, says Piero Benvenuti, ESA Hubble Project Scientist. “The synergy between the most advanced ground and space telescopes continues to prove its effectiveness, paving the way to impressive new discoveries that would not otherwise be possible.”

The discovery of young globular clusters within old galaxies is surprising since the stars in the giant elliptical galaxies were until now believed to have formed during a single period early in the history of the Universe. It is now clear that some of the galaxies may be hiding their true nature and have indeed experienced much more recent periods of major star formation.

Original Source: ESA News Release

Image credit: ESO

The latest image released from the European Southern Observatory is of the Tarantula Nebula, located in the Large Magellanic Cloud approximately 170,000 light years from here. The nebula measures more than 1,000 light years across and covers the same amount of sky as the Moon. The image is a composite made up of 15 individual exposures taken with the 2.2m telescope at La Silla Observatory in Chile.

The largest emission nebula in the sky, the Tarantula Nebula (also known as NGC 2070 or 30 Doradus) is located in the Large Magellanic Cloud (LMC), one of the satellite galaxies to our own Milky Way system. Seen far down in the southern sky at a distance of about 170,000 light-years, this beautiful nebula measures more than 1000 light-years across and extends over more than one third of a degree, almost, but not quite the size of the full moon. It received its descriptive name because of the unusual shape.

It is a splendid object with a central cluster of hot and luminous young stars that powers strong emission from hydrogen and oxygen gas, making the Tarantula Nebula an easy and impressive target for observations, even with the unaided eye. It is well visible from ESO’s mountain observatories at La Silla and Paranal in Chile and it has been the object of innumerable research programmes with many different telescopes.

The present images of the Tarantula Nebula were obtained with the Wide-Field Imager (WFI) on the MPG/ESO 2.2-m telescope at the La Silla Observatory. This advanced digital camera has already produced many impressive pictures, cf. the WFI Photo Gallery [1].

As the name indicates, the WFI has a comparatively large field-of-view, 34 x 34 arcmin2, and it is therefore well suited to show the full extent of this stunning nebula.

The WFI image
PR Photo 14a/02 has been produced from 15 individual WFI-exposures obtained in September 2000. Details are available below about the way it was made.

A large number of different and colourful objects are seen in this amazing image. The very complex nebulosity is prominent in most of the field; it predominantly emits red light from hydrogen atoms (the H-alpha spectral line at wavelength 656.2 nm) and green-blue light from hydrogen atoms (H-beta line at 486.2 nm) and oxygen ions (two [O III] lines at 495.7 and 500.7 nm).

This emission is excited by the strong ultraviolet (UV) radiation emitted by hot young stars in the central cluster (known as “R136”) which were born 2-3 million years ago at the heart of the Tarantula Nebula.

Throughout the field, there are several other smaller, young open stellar clusters that are still embedded in nebulosity. Two globular clusters can also be seen, NGC 2100 at the very left of the field-of-view (see PR Photo 14d/01 below), and KMHK 1137 at the upper right (PR Photo 14e/01) [2].

Note the very different colours of these two globular clusters: the stars in NGC 2100 appear blue and bright, indicating their relative youth, whereas those in KMHK 1137 are fainter and much redder, due to their older age and possibly also the reddening effect of dust in this area.

The entire field is full of stars of very different colours and luminosity – most of them belong to the LMC, but some are foreground objects in our own galaxy, the Milky Way.

Original Source: ESO News Release

Image credit: NASA

A team of astronomers from the Space believe that red quasars may be more common in the Universe than previously thought. Quasars are bright, distant objects and the current theory is that they are caused by the black holes that reside at the centre of galaxies – because they’re so hot, they usually appear blue. Red quasars are largely obscured by dust and were typically hard to find in visible light, but they can be found in infrared light. The team compared sky surveys in visible and infrared light and turned up 17 of the elusive red quasars.

Elusive red quasars may be more common than previously expected, according to a recent survey conducted by a research team headed by Dr. Mark Lacy, an astronomer at the Space Infrared Telescope Facility Science Center in Pasadena.

The team will display its report on June 3 at the American Astronomical Society meeting in Albuquerque, N.M.

“Every galaxy is thought to have contained a quasar at some point in its lifetime. We wanted a good estimate of the number of quasars existing early in the life of the universe to compare to the numbers of black holes we see in the centers of galaxies today,” Lacy said.

Quasars are thought to be caused by black holes that reside at the centers of galaxies and attract matter from their host galaxies. As the matter falls into the black hole, it heats up and glows brightly, producing a quasar. Because the gas is so hot, many quasars appear very blue in color. Red quasars, however, have smoke-like dust in front of them. This dust absorbs the blue light from the quasar, making it appear redder and fainter than it would otherwise.

Red quasars, which are less common than normal quasars, are difficult to detect because their colors make them hard to distinguish from stars. To find red quasars, Lacy and his team first matched two surveys revealing the positions of existing quasars, among other objects. The two surveys used were the near-infrared Two Micron All-Sky Survey, carried out by the University of Massachusetts and processed at the JPL/Caltech Infrared Processing and Analysis Center in Pasadena, and the Faint Images of the Radio Sky at Twenty-centimeters survey, conducted by R.H. Becker, R.L. White, and D.J. Helfand using the Very Large Array, about 50 miles west of Socorro, New Mexico.

To determine which of the existing quasars were red, the team then used digitized Palomar Observatory sky survey plates, which show images of the sky in visible light. Red quasars were faint or invisible in these plates because of the dust in front of them, but were detected in the infrared. Halfway through their project, Lacy and his team had already found 17 of the reddest quasars known.

“Seventeen is a big number because it implies that there are a lot more red quasars in the universe that we have yet to find,” Lacy said.

Lacy’s team suspects there are many quasars that are even redder than those they observed. They believe these objects, called Quasar-2’s, are just as common as normal quasars. These highly reddened quasars were undetectable through their methods; however, other surveys have reported that they exist.

Lacy co-authored the report with M. Gregg and R.H. Becker, University of California, Davis and the Institute of Geophysics and Planetary Physics Lawrence Livermore National Laboratory, Livermore, Calif.; R.L. White, the Space Telescope Science Institute, Baltimore, Md.; and E. Glikman and D.J. Helfand, Columbia University, New York, N.Y.

The Faint Images of the Radio Sky at Twenty-centimeters survey is supported by the National Science Foundation, Arlington, Va.; the Institute for Geophysics and Planetary Physics Lawrence Livermore National Laboratory; the California Space Institute of the University of California; the Space Telescope Science Institute; Columbia University; Sun Microsystems, Santa Clara, Calif.; the North Atlantic Treaty Organization, Brussels, Belgium; and the National Geographic Society, Washington, D.C.

The Space Infrared Telescope Facility Science Center will handle science operations for the Space Infrared Telescope Facility mission, launching next year. The mission is managed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif., for NASA’s Office of Space Science, Washington, D.C.

Original Source: NASA/JPL News Release

Image credit: 2MASS

One of the most groundbreaking work in astronomy being done right now is the Two Micron All-Sky Survey which is producing a high-resolution survey of the entire sky in the Infrared spectrum. Two telescopes, one in Arizona, the other in Cerro Tololo, Chile have been working non-stop for 4 years to take over 100 million individual images; these have been stitched together by computer. Infrared light has a much longer spectrum than visible light, so the images reveal objects which would normally be obscured by thick clouds of gas and dust.

Would it be possible to see the entire sky without ever stepping outside? Well, if you have access to a computer, the answer would be ?yes,? thanks to the Two Micron All-Sky Survey (2MASS), the most detailed digital map of the heavens ever made.

“These telescopes have given us the first detailed global view of our Milky Way Galaxy and the galaxies that lie beyond,” said Dr. Michael Skrutskie of the University of Virginia, the survey?s principal investigator. “The resulting databases and source catalogues are a treasure trove which will be mined for discovery by scientists and the public alike for decades to come.”

A Huge Undertaking
This tremendous task was accomplished by dividing the sky into nearly 60 thousand strips, each covering roughly the area of a toothpick held at arm?s length. Two dedicated telescopes, one in Arizona, the other in Cerro Tololo, Chile, patiently scanned these strips of sky every night, weather permitting, for nearly four years. The telescopes were built and observations conducted by the University of Massachusetts at Amherst.

While observations concluded in February 2001, the massive data reduction efforts have continued at the Infrared Processing and Analysis Center on the Caltech campus.

The 2MASS software automated what would have taken astronomers decades to do using conventional techniques. The system processed over 100 million individual frames, stitching them together into larger images while simultaneously identifying and measuring the properties of all the stars and galaxies seen within them.

An Infrared Perspective
The ?Two Micron? part of the sky survey refers to the part of the spectrum viewed by the survey?s digital eyes. Near-infrared light has a wavelength about four times longer than visible light, well beyond the limits of human vision. The survey telescopes employed sophisticated electronic cameras cooled to temperatures not far above absolute zero to see into this part of the spectrum.

The cameras simultaneously captured the sky in three different colors of infrared light. By remapping these colors into the visible colors of red, green, and blue, astronomers have produced full color images of the sky that look similar to ordinary visible light images, but show different features. Even well-known objects like the Orion Nebula take on striking new appearances.

Near-infrared light offers several advantages to astronomers. It more easily penetrates clouds of dust like those found across the Milky Way, revealing stars and galaxies that are completely hidden in visible light. It is also more sensitive to the largest population of stars in the Galaxy, the ones that are smaller and cooler than the Sun. The Two Micron All-Sky Survey observations open up the universe for studies of previously unknown stars and lay bare the internal structures of distant galaxies.

The Galaxy Inside-Out
One stunning product of the survey is an ?inside-out? view of our own Milky Way Galaxy. Constructed from the database of half a billion stars automatically identified by the processing software, it gives an unparalleled census of the Milky Way?s geography and population.

Evident in striking detail is the flat disk, punctuated by thin lanes of dense dust clouds. Towards the center we find the galactic bulge surrounding the inner nucleus of the Milky Way, long thought to harbor a supermassive black hole.

The view also extends beyond just the local Milky Way stars. Just beneath and right of the galactic center we can see the star clouds associated with our nearest neighbors: the Large and Small Magellanic clouds. A very sharp eye can even pick out a faint ?finger? of stars in the lower left side of the galactic bulge; this is the first direct image ever made of a small dwarf galaxy recently discovered to be in the process of merging with the Milky Way.

Getting the Pictures
The Two Micron All-Sky Survey has opened up new views of the universe, literally allowing people to see the whole sky in a different light. And anyone with access to a web browser can enjoy the visual feast.

The catalogues and images are distributed freely to the astronomical community and the general public via the Internet. Nearly half of the sky is currently available, and processing is ongoing for the final data release, expected in late summer 2002.

When the final sets of catalogues and images come online, they will consist of about 2 terabytes (that’s 2,000 gigabytes, or 2 million megabytes!) of computer data.

The final release will include catalogues of about half a billion stars and 2 million galaxies. Over one million research-quality images of the whole sky will be available in each of the three infrared colors observed by 2MASS. Such huge data sets represent part of astronomy’s future, as scientists learn interesting new things by analyzing terabyte-sized sets of data.

Fortunately the astronomy enthusiast has more direct access to this fantastic sky imagery. A new ?2MASS Showcase? gallery contains a selection of the very finest full color images from the survey, some at resolutions suitable for printing full posters!

In addition, the existing Image Gallery and Picture of the Week archives contain hundreds of images of interesting objects throughout the Galaxy and beyond. Even the most demanding visitors should be able to find the infrared views of their favorite objects now that the sky is online for everyone to enjoy!

Original Source: NASA News Release

Image credit: NSF

Astronomers from the National Science Foundation and Caltech have created the most detailed images ever made of the oldest light emitted by the Universe. The team used the Cosmic Background Imager, an array of sensitive microwave detectors in the Chilean desert, to gather light that had traveled 14 billion years to reach the Earth; it shows us the Universe at only 300,000 years old, just as seeds of matter had started to form, eventually becoming galaxies, stars, planets, and us.

Astronomers operating from a remote plateau in the Chilean desert have produced the most detailed images ever made of the oldest light emitted by the universe, providing independent confirmation of controversial theories about the origin of matter and energy.

Pushing the limits of available technology, the Cosmic Background Imager (CBI) funded by the National Science Foundation (NSF) and California Institute of Technology (Caltech) detected minute variations in the cosmic microwave background, the radiation that has traveled to Earth over almost 14 billion years. A map of the fluctuations shows the first tentative seeds of matter and energy that would later evolve into clusters of hundreds of galaxies.

The measurements also provide independent evidence for the long-debated theory of inflation, which states that the universe underwent a violent expansion in its first micro-moments. After about 300,000 years it cooled enough to allow the seeds of matter to form and became “transparent,” allowing light to pass through. CBI observed remnants of that early radiation. The data are also helping scientists learn more about the repulsive force called “dark energy” that appears to defy gravity and force the universe to accelerate at an ever-increasing pace.

“This is basic research at its finest and most exciting,” said NSF Director Rita Colwell. “Each new image of the early universe refines our model of how it all began. Just as the universe grows and spreads, humankind’s knowledge of our own origins continues to expand, thanks to the technical expertise and patient persistence of scientists such as these.”

“We have seen, for the first time, the seeds that gave rise to clusters of galaxies, thus putting theories of galaxy formation on a firm observational footing,” said team leader Anthony Readhead of Caltech. “These unique high-resolution observations provide a new set of critical tests of cosmology, and provide new and independent evidence that the universe is flat and is dominated by dark matter and dark energy.”

Readhead, with Caltech colleagues Steve Padin and Timothy Pearson and others from Canada, Chile and the United States, generated the finest measurements to date of the cosmic microwave background. Cosmic microwave background (CMB) is a record of the first photons that escaped from the rapidly cooling, coalescing universe about 300,000 years after the cosmic explosion known as the Big Bang that is commonly believed to have given birth to the universe.

Data from the CBI on temperature distributions in the CMB support a modification of the Big Bang theory; that modification is called inflation theory. Inflation states that the hot plasma of the initial universe underwent an extreme and rapid expansion in its first 10 -32 second. The variations in temperature measured by the CBI are as small as 10 millionths of a degree.

By plotting the peaks of temperature distribution, the scientists showed that the precise CBI data are entirely consistent with inflation and confirm earlier findings by other scientists. In April 2000, an international team of cosmologists led by Caltech’s Andrew Lange announced the first compelling evidence that the universe is flat-that is, its geometry is such that parallel lines will neither converge or diverge. Lange’s team observed at a different frequency from CBI, using a high-altitude balloon flown over Antarctica.

Since then, two other teams — using independent methods — have revealed their analyses of the very faint variations in temperature among the cosmic microwaves. The four instruments have conducted precise measurements of parameters that cosmologists have long used to describe the early universe. Each set of data has offered new clues to the form of the embryonic plasma and has drawn scientists closer to definitive answers. NSF has supported the work of all four teams and their instruments, some of them for more than 15 years.

Five papers on the CBI data were submitted today to the Astrophysical Journal for publication.

The CBI consists of 13 interferometers mounted on a 6-meter-diameter platform, operating at frequencies from 26 GHz to 36 GHz. Located in the driest desert in the world — the Atacama — CBI takes advantage of the low humidity at an altitude of 5,080 meters (16,700 feet). NSF has supported the CBI research since 1995. The National Council of Science and Technology of Chile provided the CBI site.

Original Source: NSF News Release

Image credit: NASA

A team of astronomers from UCLA have found cloudy, stormy atmospheres on brown dwarfs – objects larger than gas giants like Jupiter, but not large enough to ignite into full stars. They believe the discovery of these storms could provide insights into some strange observations of brown dwarfs. Instead of steadily cooling, the objects have been seen to get brighter for brief periods, so this could be accounted for by breaks in the cloudy atmosphere.

For the first time, researchers have observed planet-like weather acting as a major influence on objects outside our solar system.

A team of scientists from NASA and the University of California, Los Angeles (UCLA), has found cloudy, stormy atmospheres on brown dwarfs, celestial bodies that are less massive than stars but that have more mass than giant planets like Jupiter. The discovery will give scientists better tools for interpreting atmospheres and weather on brown dwarfs or on planets around other stars.

“The best analogy to what we witness on these objects are the storm patterns on Jupiter,” said Adam Burgasser, astronomer at UCLA and lead author of the study. “But I suspect the weather on these more massive brown dwarfs makes the Great Red Spot look like a small squall.” Jupiter?s Great Red Spot is a massive storm more than 15,000 miles across and with winds of up to 270 miles per hour. Burgasser teamed up with planetary scientist Mark Marley, meteorologist Andrew Ackerman of NASA Ames Research Center in California’s Silicon Valley, and other collaborators to propose how weather phenomena could account for puzzling observations of brown dwarfs.

“We had been thinking about what storms might do to the appearance of brown dwarfs,? Marley said. “And when Adam showed us the new data, we realized there was a pretty good fit.” The team calculated that using a model with breaks or holes in the cloudy atmosphere solved the mysterious observations of cooling brown dwarfs.

Brown dwarfs, only recently observed members of the skies, are “failed stars at best,” said Ackerman. Not massive enough to sustain the burning of hydrogen like stars, brown dwarfs go through cooling stages that scientists observe with infrared energy-detecting telescopes. They appear as a faint glow, like an ember from a fire that gives off both heat and light energy as it dims.

Astronomers expected brown dwarfs, like most objects in the universe, to grow steadily fainter as they cool. However, new observations showed that during a relatively short phase brown dwarfs appear to get brighter as they cool. The explanation lies in the clouds.

At least 25,000 times fainter than the sun, brown dwarfs are still incredibly hot, with temperatures as high as 2,000 degrees Kelvin (3,140 F). At such high temperatures, things like iron and sand occur as gases. As brown dwarfs cool, these gases condense in the atmosphere into liquid droplets to form clouds, similar to water clouds on Earth. As the brown dwarf cools further, there is a rapid clearing of the clouds caused by atmospheric weather patterns. As the clouds are whisked away by the storms, bright infrared light from the hotter atmosphere beneath the clouds escapes, accounting for the unusual brightening of the brown dwarfs.

“The model developed by the group for the first time matches the characteristics of a very broad range of brown dwarfs, but only if cloud clearing is considered,” said Burgasser. “While many groups have hinted that cloud structures and weather phenomena should be present, we believe we have actually shown that weather is present and can be quite dramatic.”

By using Earth’s weather as a starting point, Ackerman helped the team work storms?that include wind, downdrafts and iron rain?into their calculations. “The astrophysicists needed some help understanding rain because it’s not an important process in most stars,? Ackerman said. “We used observations and simulations of terrestrial clouds to estimate the effect of iron rain on the thickness of an iron cloud.”

The team’s study, to be published in the June 1 issue of Astrophysical Journal Letters, will help researchers determine the make-up of atmospheres outside our solar system. “Brown dwarfs have traditionally been studied like stars, but it’s more of a continuum,” Marley said. “If you line a mug shot of Jupiter up with these guys, it is just a very low-mass brown dwarf.” Brown dwarfs are a training ground for scientists to learn how to interpret observations of planet-like objects around other stars, he said. “Everybody wants to find brown dwarfs that are even colder and have water clouds just like Earth. Once we find those, that will be a good test of our understanding.”

Original Source: NASA News Release

Image credit: Gemini

Thanks to the adaptive optics system of the Gemini observatory, astronomers have been able to spot a brown dwarf orbiting a star only three times the distance of the Earth to the Sun. This newly discovered pair, LHS 2397a, is located only 46 light years from Earth and is the closest separation of a binary star ever uncovered. The Hawaii-based Gemini telescope is so powerful because it uses a flexible mirror that counteracts the blurring caused by the Earth’s atmosphere.

Astronomers using adaptive optics technology on the Gemini North Telescope have observed a brown dwarf orbiting a low-mass star at a distance comparable to just three times the distance between the Earth and Sun. This is the closest separation distance ever found for this type of binary system using direct imaging.

The record-breaking find is just one of a dozen lightweight binary systems observed in the study. Together, they provide a new perspective on the formation of stellar systems and how smaller bodies in the Universe (including large planets) might form.

“By using Gemini’s advanced imaging capabilities, we were able to clearly resolve this binary pair where the distance between the brown dwarf and its parent star is only about twice the distance of Mars from the Sun,” said team member Melanie Freed, a graduate student at the University of Arizona in Tucson. With an estimated mass of 38-70 times the mass of Jupiter, the newly identified brown dwarf is located just three times the Sun-Earth distance (or 3.0 Astronomical Units) from its parent star. The star, known as LHS 2397a, is only 46 light-years from Earth. The motion of this object in the sky indicates that it is an old, very low-mass star.

The previous imaging record for the closest distance between a brown dwarf and its parent (a much brighter, Sun-like star) was almost five times greater at 14 AU. One Astronomical Unit (AU) equals the average distance between the Earth and the Sun or about 150 million kilometers (93 million miles).

Often portrayed as “failed stars,” brown dwarfs are bigger than giant planets like Jupiter, but their individual masses are less than 8% of the Sun’s mass (75 Jupiter masses), so they are not massive enough to shine like a star. Brown dwarfs are best viewed in the infrared because surface heat is released as they slowly contract. The detection of brown dwarf companions within 3 AU of another star is an important step toward imaging massive planets around other stars.

This University of Arizona team led by Dr. Laird Close used the Gemini North Telescope to detect eleven other low mass companions, suggesting that these low-mass binary pairs may be quite common. The discovery of so many low-mass pairs was a surprise, given the argument that most very low-mass stars and brown dwarfs were thought to be solo objects wandering though space alone after being ejected out of their stellar nurseries during the star formation process.

“We have completed the first adaptive optics-based survey of stars with about 1/10th of the Sun’s mass, and we found nature does not discriminate against low-mass stars when it comes to making tight binary pairs,” said Close, an assistant professor of astronomy at the University of Arizona. Dr. Close is the lead author on a paper presented today at the Brown Dwarfs International Astronomical Union Symposium in Kona, Hawaii, and he is the principal investigator of the low-mass star survey.

The team looked at 64 low-mass stars (originally identified by John Gizis of the University of Delaware) that appeared to be solo stars in the lower resolution images from the 2MASS all-sky infrared survey. Once the team used adaptive optics on Gemini to make images that were ten times sharper, twelve of these stars were revealed to have close companions. Surprisingly, Close’s team found that the separation distances between the low mass stars and their companions were significantly less than expected.

“We find companions to low-mass stars are typically only 4 AU from their primary stars, this is surprisingly close together,” said team member Nick Siegler, a University of Arizona graduate student. “More massive binaries have typical separations closer to 30 AU, and many binaries are much wider than this.” The new Gemini observations, Close said, “imply strongly that low-mass stars do not have companions that are far from their primaries.” Similar results had been found previously by a team led by Dr. Eduardo L. Martin of the University of Hawaii Institute for Astronomy in a survey of 34 very low-mass stars and brown dwarfs in the Pleiades cluster carried out with the Hubble Space Telescope. These two surveys together clearly demonstrate that there is an intriguing dearth of brown dwarfs at separations larger than 20 AU from very low-mass stars and other brown dwarfs.

The team projects that one out of every five low-mass stars has a companion with a separation in the range (3-200 AU). Within this separation range, astronomers have observed a similar frequency of more massive stellar companions around larger Sun-like stars.

Taken as a whole, these new results suggest that (contrary to theory) low-mass binaries may form in a process similar to that of more massive binaries. Indeed, this finding adds to growing evidence from other groups that the percentage of binary systems is similar for bodies spanning the range from one solar mass to as little as 0.05 solar masses (or 52 times Jupiter’s mass). For example, a group led by Neill Reid of the Space Telescope Science Institute and the University of Pennsylvania has come to a similar conclusion with a smaller sample of 20 even lower-mass stars and brown dwarfs observed with the Hubble Space Telescope.

The fact that low-mass stars have any low-mass brown dwarf companions inside 5 AU is also surprising because the exact opposite is true around Sun-like stars. Very few Sun-like stars have brown dwarf companions inside this distance, according to radial velocity studies. “This lack of brown dwarf companions within 5 AU of Sun-like stars has been called the ‘brown dwarf desert’,” Close noted. “However, we see there is likely no brown dwarf desert around low-mass stars.”

These results form important constraints for theorists working to understand how the mass of a star affects the mass and separation distance of the companions that form with it. “Any accurate model of star and planet formation must reproduce these observations,” Close said.

These observations were possible only because of the combination of the University of Hawaii’s uniquely sensitive Hokupa’a adaptive optics imaging system and the technical performance of the Gemini telescopes. The Hokupa’a system sensitivity is due to the curvature wavefront sensing concept developed by Dr. Francois Roddier. Adaptive optics is an increasingly crucial technology that eliminates most of the “blurring” caused by the turbulence in the Earth’s atmosphere (i.e., the twinkling of the stars). It does this by rapidly adjusting the shape of a special, smaller flexible mirror to match local turbulence, based on real-time feedback to the mirror’s support system from observations of the low-mass star. Hokupa’a can count individual photons (particles of light) and so can sharpen accurately even very faint (i.e., low-mass) stars.

The near-infrared adaptive optics images made by the 8-meter Gemini telescope in this survey were twice as sharp as those that can be made at the same wavelengths by the Earth-orbiting, 2.4-meter Hubble Space Telescope. The only ground-based survey of its kind, this work required five nights over one year with the Hokupa’a system at Gemini North.

It is important to note that the distances used here are as measured on the sky. The real orbital separations may be slightly larger once the full orbit of these binaries is known in the future.

Other science team members include James Liebert (Steward Observatory, University of Arizona), Wolfgang Brandner (European Southern Observatory, Garching, Germany), and Eduardo Martin and Dan Potter (Institute for Astronomy, University of Hawaii).

The observations reported here are part of an ongoing survey. Initial results from the first 20 low-mass stars of our survey have been published in the March 1, 2002 issue of The Astrophysical Journal Letters vol 567 Pages L53-L57.

Images and illustrations related to this news release are available on the Internet at: http://www.gemini.edu/media/images_2002-7.html.

Laird Close can be contacted at 520/626-5992, [email protected], after he returns to his office on May 28.

This survey was supported in part by the U.S. Air Force Office of Scientific Research and the University of Arizona’s Steward Observatory. Hokupa’a is supported by the University of Hawaii Adaptive Optics Group and the National Science Foundation.

The Gemini Observatory is an international collaboration that has built two identical 8-meter telescopes. The telescopes are located at Mauna Kea, Hawaii (Gemini North) and Cerro Pach?n in central Chile (Gemini South), and hence provide full coverage of both hemispheres of the sky. Both telescopes incorporate new technologies that allow large, relatively thin mirrors under active control to collect and focus both optical and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in each partner country with state-of-the-art astronomical facilities that allocate observing time in proportion to each country’s contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the UK Particle Physics and Astronomy Research Council (PPARC), the Canadian National Research Council (NRC), the Chilean Comisi?n Nacional de Investigaci?n Cientifica y Tecnol?gica (CONICYT), the Australian Research Council (ARC), the Argentinean Consejo Nacional de Investigaciones Cient?ficas y T?cnicas (CONICET) and the Brazilian Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq). The Observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.

For more information, see the Gemini website at: http://www.us-gemini.noao.edu/media/.

Original Source: Gemini News Release

Image credit: PPARC

A team of UK astronomers have discovered a new class of cannibalistic stars that may explain one of the mysteries surrounding the Big Bang. These stars formed shortly after the Big Bang but don’t contain any lithium -which astronomers predicted should be there. Astronomers believed that they must have misunderstood some essential aspect about the early universe, but this new research helps explain what happened to the lithium; it was destroyed by the star’s interaction with a partner star.

A team of UK astronomers announced this month the discovery of cannibalistic stars that explain one of the mysteries surrounding the Big Bang. The stars are almost as old as the Universe and they reveal what space was like in the very beginning.

The team from the Open University found that a group of 14-billion-year-old stars were all in a spin (literally) because of a nasty phase earlier in their lives. They were, in short, cannibalistic stars. The scientists’ discovery not only explains the origin of these mysterious stars, but also strengthens the Big Bang theory. The Big Bang is the name given to the rapid expansion of the Universe that marked the beginning of space and time; it explains the origin of the matter in the universe – including the matter which people are made of.

The stars under investigation are some of the oldest in the Universe. They formed out of gas clouds not long after the Big Bang. The OU team, led by Dr Sean Ryan, found that some of the stars that formed early in the life of the Universe were very unusual. They contained none of the metal lithium which astronomers believe is produced in the Big Bang.

Dr Ryan said:

“Observations showed that about 1 star in 20 contained no lithium, and some astronomers were concerned that this might mean we had misunderstood something important about the Big Bang and the origin of the Universe.”

New and more detailed observations of the peculiar stars were made with the 4.2-metre-diameter William Herschel Telescope. Using high precision equipment, the team found that most of the stars without lithium were spinning very fast. “Measuring the spin speed of stars is very difficult,” said Dr Ryan, “this is why no-one had seen this before. Most 14-billion-year-old stars do not spin very fast at all but these ones had up to 16 times as much spin energy as the Sun, our nearest star. We knew that the extra energy could come from only one source; another star.”

Dr Ulrich Kolb, an OU astronomer who specialises in interacting stars, explained what happened. “When these stars formed out of the gas clouds, not just one but two stars formed very near one another. Fatally, they were too close together for their own good. As they grew older, the smaller one captured the outer layers of the larger one. Very little now remains of what was the larger star; it has been cannibalised by its companion.”

The material captured by the companion carried orbital energy that was converted into spin energy. It was the discovery of the excessive spin energy that revealed the history of the objects.

The scientists believe that the lithium was destroyed in nuclear reactions shortly before the star-eating episode occurred.

Dr Ryan said:

“It’s rather a relief that we have discovered why the lithium-depleted stars are so different to most others. Knowing that the Big Bang theory tells us correctly how much lithium was produced gives us confidence that we really do understand much about the origin of the entire universe. Hydrogen that was formed in the Big Bang powers the Sun, which in turn provides energy to the Earth. It is also a vital component of pure water, which is so essential to life. Also we now know more about what happens when stars feed on one another.”

Using a technique called Doppler spectroscopy, the observations were made by measuring the speeds at which the stars are moving. This is similar to the way traffic speeds are measured on roads, but with stars clocking up many kilometres per second, not just a few kilometres per hour. The William Herschel Telescope on which the observations were made is one of the UK’s major telescopes. It is co-funded and operated by the Particle Physics and Astronomy Council (PPARC). It is located under the clear skies of the Canary Islands, where observing conditions are much better than in Great Britain. The telescope is shared with Dutch and Spanish astronomers. Dr Sean Ryan will be observing from the Canary Islands on 22-24 May.

Original Source: PPARC News Release