Carnegie Science News - Astronomy/Cosmology

Pasadena, CA – The board of directors of the Giant Magellan Telescope Organization (GMTO) has informed the National Science Foundation (NSF) that they will not participate in an upcoming funding opportunity. The partners in the project feel that they are making such rapid progress that they have chosen to press ahead at full speed, looking to link up with the NSF at a later date when the needs of both organizations are better aligned. With nearly half of the $700M needed to build the observatory committed, the partners are confident that they will complete the telescope.
 
In December, the NSF issued a call for proposals to develop a plan for partnering with the NSF, but is unable to commit to a partnership or to identify a path towards federal funding for construction before the end of the decade. The NSF solicitation offers $250,000 per year in funding for activities related to community involvement, scientific workshops, and other planning work. In a letter to the NSF director of the Division of Astronomical Sciences, Dr. James Ulvestad, GMTO board chair Dr. Wendy Freedman stated: “After careful consideration, the GMT Board has chosen not to pursue this solicitation, but to develop our own program for cultivating partnerships within the U.S. community and with our international partners. We believe this is the best course for the GMT.” She went on to assure the NSF that “we remain committed to your stated goal of realizing the ‘significant opportunities in research, education, and instrumentation for the U.S. community under a public/private/international partnership’.”
 
The Giant Magellan Telescope (GMT) is a next generation astronomical observatory with unprecedented power. Its 85-foot diameter segmented primary mirror will provide approximately 4,000 square feet of light-collecting area. In the past few months the project has successfully polished the first off-axis mirror segment, cast the second giant mirror, started demolition and earth moving at the site at the Carnegie Institution’s Las Campanas Observatory in Chile, and selected their first generation of scientific instruments.
 
At its March 27/28 meeting the GMTO board accepted recommendations from a blue-ribbon panel regarding the selection of a suite of first generation instruments that includes powerful cameras and spectrographs that will allow the GMT to explore planetary systems around other stars and to look back to the dawn of time and the birth of the first stars, galaxies, and black holes. The GMT will help astronomers probe the nature of dark matter and dark energy, mysterious forms of matter and energy that allow galaxies to form while the expansion of the universe accelerates.
 
The GMT partner institutions are the Australian National University, Astronomy Australia Limited, the Carnegie Institution for Science, Harvard University, the Korea Astronomy and Space Science Institute, The Smithsonian Institution, Texas A&M University, the University of Arizona, the University of Chicago, and the University of Texas at Austin. More information regarding the GMT project and their statement regarding the NSF solicitation can be found at: www.gmto.org [3]
 

Pasadena, CA--Astronomers have begun to blast 3 million cubic feet of rock from a mountaintop in the Chilean Andes to make room for what will be the world’s largest telescope when completed near the end of the decade. The telescope will be located at the Carnegie Institution’s Las Campanas Observatory—one of the world’s premier astronomical sites, known for its pristine conditions and clear, dark skies. Over the next few months, more than 70 controlled blasts will break up the rock while leaving a solid bedrock foundation for the telescope and its precision scientific instruments.
 
(High-resolution image [6] courtesy US State Department)
 
The Giant Magellan Telescope (GMT) will have unprecedented capabilities, allowing it to peer back to the dawn of time, witnessing the birth of the first stars, galaxies and black holes, while also exploring planetary systems similar to our own around nearby stars in the Milky Way. The GMT will help astronomers probe the nature of dark matter and dark energy, mysterious forms of matter and energy that allow galaxies to form while the expansion of the universe accelerates.
 
At a ceremony on the mountaintop March 23, Dr. Wendy Freedman, director of the Carnegie Observatories and chair of the Giant Magellan Telescope Organization (GMTO) said, “Today marks a historic step toward constructing an astronomical telescope larger than any in existence today. Years of testing have shown that Las Campanas is one of the premier observatory sites in the world and the Carnegie Institution is proud to host the GMT.”
 
The Giant Magellan Telescope is being built by a consortium of U.S., South Korean and Australian institutions with funding from both private and public sources. To date 40% of the telescope’s ultimate $700M price tag has been committed and active fundraising is underway to secure the remaining funds.
Carnegie president Richard A. Meserve remarked, “The Carnegie Institution has been a world leader in telescope design and construction for over a century, building the largest and most advanced telescopes in the world. We continue this tradition with the GMT and look forward to the exciting scientific bounty it will yield.”
 
In January of this year the partners cast the second of GMT’s seven 28-foot diameter primary mirror segments at the University of Arizona’s Steward Observatory Mirror Laboratory. The seven primary mirrors, each weighing 20 tons, are the heart of the giant telescope, providing nearly 4,000 square feet of light-gathering area.
 
Optical scientists at the Mirror Lab are putting the finishing touches on the first mirror segment, whose surface now matches its optical prescription to better than one millionth of an inch. Dr. Patrick McCarthy, the GMT project director, said “2012 is a banner year for the GMT project as we complete the design process, develop the primary mirrors, and begin work on the site in Chile.”
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The GMT partner institutions are the Carnegie Institution for Science, The Australian National University, Astronomy Australia Limited, Harvard University, the Korea Astronomy and Space Science Institute, The Smithsonian Institution, Texas A&M University, the University of Arizona, the University of Chicago, and the University of Texas at Austin. More information regarding the GMT project and Las Campanas Observatory can be found at: www.gmto.org [3].

Pasadena, CA— Eta Carinae, one of the most massive stars in our Milky Way galaxy, unexpectedly increased in brightness in the 19th century. For ten years in the mid-1800s it was the second-brightest star in the sky. (Now it is not even in the top 100.) The increase in luminosity was so great that it earned the rare title of Great Eruption. New research from a team including Carnegie’s Jose Prieto, now at Princeton University, has used a “light echo” technique to demonstrate that this eruption was much different than previously thought. Their work is published Feb. 16 in Nature.
Eta Carinae is a Luminous Blue Variable (LBV), meaning it has periods of dimness followed by periods of brightness. The variations in brightness of an LBV are caused by increased instability and loss of mass. The Great Eruption was an extreme and unique event in which the star, which is more than 100 times the mass of the Sun, lost several times the mass of the Sun. Scientists have believed that this rare type of eruption was caused by a stellar wind.
The team of scientists, led by Armin Rest of the Space Telescope Science Institute, used images of Eta Carinae over 8 years to study light echoes of the Great Eruption. For the first time, they observed light from the eruption that bounced, or echoed, off interstellar dust tens of light years from the star. Those extra tens of light years mean that the light is reaching Earth now rather than in the 1800s when people on Earth observed the light that traveled here directly.
They then used the Magellan and du Pont telescopes at Las Campanas Observatories, in Chile, to obtain spectra of the echoes of light. The spectra allow them to precisely separate the light into its constituents, much like a drop of rain naturally acts as a prism and separates sunlight into the colors of the rainbow. These observations give important information about the chemical composition, temperature, and velocity of the material ejected during the 19th century Great Eruption.
Most surprisingly, their observations show that the Great Eruption is different from so-called “supernova impostor,” events in nearby galaxies that are thought to be eruptions from LBVs. For example, the Great Eruption was significantly cooler than allowed by simple stellar-wind models used to explain supernova impostors.
“This star’s Giant Eruption has been considered a prototype for all supernova imposters in external galaxies,” Prieto said. “But this research indicates that it is actually a rather unique event.”
Thus, scientists still don’t know what phenomenon caused Eta Carinae to erupt and lose such a quantity of mass without being destroyed. Further research is necessary to determine whether other proposed models could have triggered this activity instead.
 
Caption: These images reveal light from a massive stellar outburst in the Carina Nebula reflecting off dust clouds surrounding a behemoth double-star system, a phenomenon called a light echo.
The color image at left shows the Carina Nebula, a star-forming region located 7500 light-years from Earth. The massive star Eta Carinae resides near the top of the image. The double-star system, about 120 times more massive than the Sun, produced a spectacular outburst that was seen on Earth from 1837 to 1858. But some of the light from the eruption took an indirect path and is just now reaching our planet. The light bounced off dust clouds (the box about 100 light-years away at the bottom of the image) and was rerouted to Earth. The image was taken by the U.S. National Optical Astronomy Observatory’s Curtis-Schmidt Telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile.
The three black-and-white images at right show light from the eruption illuminating the dust clouds over an eight-year span as it moves through them. The effect is like shining a flashlight on different regions of a vast cavern. The images were taken by the U.S. National Optical Astronomy Observatory’s Blanco 4-meter telescope at the CTIO. Photo credits: NASA, NOAO, and A. Rest (STScI)

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Observations were made at the Blanco 4m telescope, a facility of the Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation. Observations were also obtained at Las Cumbres Observatory Global Telescope Network and some of the scientists received support from LCOGT. The researchers used data from the UVES Paranal Observatory Project. The computations in this paper were run on the Odyssey cluster supported by the FAS Science Division Research Computing Group at Harvard University. Prieto received support from NASA’s Hubble fellowship.
 

Pasadena, CA— A team of scientists, including Carnegie’s Mansi M. Kasliwal, has observed the early stages of a Type Ia supernova that is only 21 million light years away from Earth--the closest of its kind discovered in 25 years. The Palomar Transient Factory team’s detection of a supernova less than half a day after it exploded will refine and challenge our understanding of these stellar phenomena. Their breakthrough observations are published December 15 in Nature.
Type Ia supernovae are violent stellar explosions. Observations of their brightness are used to determine distances in the universe and have shown scientists that the universe is expanding at an accelerating rate. The Nobel Prize in Physics was awarded December 10 to three astronomers for their "discovery of the accelerating expansion of the Universe through observations of distant supernovae.”
The PTF team, led by Professor Shri Kulkarni of the California Institute of Technology, discovered this supernova, named SN2011fe, just 11 hours after it exploded. They were able to pinpoint the explosion in the Pinwheel Galaxy to August 23 at about 4:30 p.m. Universal Time.
“For several years, I had been taking images with robotic telescopes at Palomar Observatory of the Pinwheel Galaxy every night I possibly could, hoping it would give birth to a rare cosmic feat,” Kasliwal said. “When we saw SN2011fe, I fell off my chair as its brightness was too faint to be a supernova and too bright to be nova. Only follow-up observations in the next few hours revealed that this was actually an exceptionally young Type Ia supernova."
The widely accepted theory is that Type Ia supernovae are thermonuclear explosions of a white dwarf star that’s part of a binary system--two stars that are physically close and orbit around a common center of mass.
There are two different models for how Type Ia supernovae are created from this type of binary system. In the so-called double-degenerate (or DD) model, the orbit between two white dwarf stars shrinks until the lighter star’s path is disrupted and it moves close enough for some of its matter to be absorbed into the primary white dwarf and initiate an explosion. In the so-called single-degenerate (or SD) model, the white dwarf slowly accretes mass from a different, non-white dwarf type of star, until it reaches an ignition point. There are three potential methods for the transfer of mass and--depending on which one is used--the second star is likely to be a red giant, a helium star, or a so-called subgiant or main-sequence star.
Observations of the early stages of the supernova--presented in a paper by lead author Peter Nugent of Lawrence Berkeley Laboratory--showed direct evidence that the primary star was a type of white dwarf called a carbon-oxygen white dwarf.
Very sensitive and early radio and X-ray observations, presented in a separate paper to be published in The Astrophysical Journal, show no evidence of interaction with surrounding material. Combining this data with an analysis of historical images, the team ruled out luminous red giants and the vast majority of helium stars for the second star in the binary system before the explosion.
These clues meant that the secondary star was either another white dwarf, as in the DD model, or a subgiant or main-sequence star, as created by one of the three SD model methods.
Analysis of the matter ejected by the supernova’s explosion suggests that the second star is less likely to be another white dwarf. Thus, the solution to the mystery of SN2011fe’s origin is probably a primary white dwarf accreting matter from a neighboring subgiant or main-sequence star.
"The fact that we discovered this supernova in its infancy, and that the Pinwheel Galaxy is in our cosmic backyard, has given us an unprecedented opportunity to make this the best studied supernova to date,” Kulkarni said.
 
Caption: SN 2011fe in the Pinwheel Galaxy (M101) at maximum brightness, a composite of optical data from the Las Cumbres Observatory Global Telescope Network 0.8m Byrne Observatory Telescope at the Sedgwick Reserve and (purple) hydrogen emission data from the Palomar Transient Factory. The left side shows the galaxy with no labels and the right shows the same with the SN2011fe labled.

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The Palomar Transient Factory (PTF) is based on the 48-inch Oschin Schmidt telescope and the 60-inch telescope of the Palomar Observatory of the California Institute of Technology and is a collaboration of the following institutions: California Institute of Technology, Columbia University, Las Cumbres Observatory Global Telescope, Lawrence Berkeley Laboratory, Oxford University, the University of California at Berkeley and the Weizmann Institute of Science. The Principal Investigator of PTF is Professor S. R. Kulkarni.
This work received financial, staff and computing...