 |
|
Hubble images some of galaxy's dimmest stars
August 21, 2006Using the Hubble Space Telescope, astronomers have imaged some of the galaxy's oldest and dimmest stars, offering a rare experimental glimpse of two mysterious star types - tiny, slow burners less than one-tenth the size of our sun and once giant stars that still glow more than 10 billion years after their deaths.
The research appears in this week's issue of the journal Science.
"This project pushed the limits of what even Hubble can do," said study co-author Jay Anderson, a research scientist at Rice University. "These stars can't be reliably detected in a single image. You have to combine a large number of images to find them."
In total, the research team trained Hubble's cameras on the same patch of sky for more than 75 hours, gathering 378 overlapping images. The target was a region of space containing about 1 percent of the globular cluster NGC 6397 - a collection of stars that formed early in our galaxy's history.
"When we look at random stars in the sky they have a variety of ages," Anderson said. "Globular clusters offer unique opportunities for astronomers to study a population of stars that are all the same age. All the stars we see in clusters are ancient, because they were created when the galaxy was forming. They're fossils from the galaxy's earliest days."
There are about 150 globular clusters in our galaxy, and most contain between 100,000 and 1 million stars. While most of the galaxy's stars - including our own sun - orbit the galactic center in the plane of the galaxy, globular clusters predate the flattening of the Milky Way, so they're scattered in a more spherical distribution.
NGC 6397 is one of the nearest clusters to Earth, located just 8,500 light years away. But even at this relatively close astronomical distance, the light from NGC 6397's faintest stars is easily lost in the glare from its brightest stars.
To survey the dimmest objects, Anderson and colleagues relied on computers. Anderson, whose specialty is writing programs to sift through astronomical data, spent months writing and refining software that could examine each Hubble image, pixel by pixel, and find the faintest stars.
The two types of object imaged represent the heavy end and the light end of the stellar mass spectrum.
A star's destiny is determined by its mass. There's a minimum mass that a star must have in order to burn hydrogen, and objects below that threshold cool rapidly and fade away. From the NGC 6397 survey, Anderson and his colleagues identified the smallest visible stars yet seen in a globular cluster, stars less than one-tenth the mass of Earth's sun. This is very near the predicted theoretical threshold, and Anderson said data from the survey will be helpful for verifying and refining theories about the structure and evolution of low-mass stars.
On the other end of the stellar mass spectrum are stars that are significantly larger than the sun. Stars about eight times the mass of the sun burn quickly and die in spectacular planetary nebulae, explosions that spew much of the star's material into space. Upon their final collapse, these stars become white dwarfs, extremely dense objects that radiate heat for billions of years as they slowly fade into darkness. Anderson said that while the brightest - and therefore youngest - white dwarfs have been seen in many clusters, the new survey yielded the first images of the faintest and oldest white dwarfs in an ancient cluster. The brightness of the white dwarfs at this end of the scale can help astronomers find out how long the stars have been cooling. From that, they can better determine the age of the cluster, which in turn can be used to narrow estimates of the lower limit of the age of the universe.
Rice University
In total, the research team trained Hubble's cameras on the same patch of sky for more than 75 hours, gathering 378 overlapping images. The target was a region of space containing about 1 percent of the globular cluster NGC 6397 - a collection of stars that formed early in our galaxy's history.
"When we look at random stars in the sky they have a variety of ages," Anderson said. "Globular clusters offer unique opportunities for astronomers to study a population of stars that are all the same age. All the stars we see in clusters are ancient, because they were created when the galaxy was forming. They're fossils from the galaxy's earliest days."
There are about 150 globular clusters in our galaxy, and most contain between 100,000 and 1 million stars. While most of the galaxy's stars - including our own sun - orbit the galactic center in the plane of the galaxy, globular clusters predate the flattening of the Milky Way, so they're scattered in a more spherical distribution.
NGC 6397 is one of the nearest clusters to Earth, located just 8,500 light years away. But even at this relatively close astronomical distance, the light from NGC 6397's faintest stars is easily lost in the glare from its brightest stars.
To survey the dimmest objects, Anderson and colleagues relied on computers. Anderson, whose specialty is writing programs to sift through astronomical data, spent months writing and refining software that could examine each Hubble image, pixel by pixel, and find the faintest stars.
The two types of object imaged represent the heavy end and the light end of the stellar mass spectrum.
A star's destiny is determined by its mass. There's a minimum mass that a star must have in order to burn hydrogen, and objects below that threshold cool rapidly and fade away. From the NGC 6397 survey, Anderson and his colleagues identified the smallest visible stars yet seen in a globular cluster, stars less than one-tenth the mass of Earth's sun. This is very near the predicted theoretical threshold, and Anderson said data from the survey will be helpful for verifying and refining theories about the structure and evolution of low-mass stars.
On the other end of the stellar mass spectrum are stars that are significantly larger than the sun. Stars about eight times the mass of the sun burn quickly and die in spectacular planetary nebulae, explosions that spew much of the star's material into space. Upon their final collapse, these stars become white dwarfs, extremely dense objects that radiate heat for billions of years as they slowly fade into darkness. Anderson said that while the brightest - and therefore youngest - white dwarfs have been seen in many clusters, the new survey yielded the first images of the faintest and oldest white dwarfs in an ancient cluster. The brightness of the white dwarfs at this end of the scale can help astronomers find out how long the stars have been cooling. From that, they can better determine the age of the cluster, which in turn can be used to narrow estimates of the lower limit of the age of the universe.
Rice University
Hubble Space Telescope News and Current Hubble Space Telescope Events RSSClash of clusters provides new dark matter clue
A powerful collision between galaxy clusters has been captured by the NASA/ESA Hubble Space Telescope and NASA's Chandra X-ray Observatory. This clash of clusters provides striking evidence for dark matter and insight into its properties.
Hubble sees magnetic monster in erupting galaxy
The Hubble Space Telescope has found the answer to a long-standing puzzle by resolving giant but delicate filaments shaped by a strong magnetic field around the active galaxy NGC 1275. It is the most striking example of the influence of these immense tentacles of extragalactic magnetic fields, say researchers.
Hubble unveils colourful star birth region on 100 000th orbit milestone
In commemoration of the NASA/ESA Hubble Space Telescope completing its 100 000th orbit around the Earth in its 18th year of exploration and discovery, scientists have aimed Hubble to take a snapshot of a dazzling region of celestial birth and renewal.
'Cosmic ghost' discovered by volunteer astronomer
When Yale astrophysicist Kevin Schawinski and his colleagues at Oxford University enlisted public support in cataloguing galaxies, they never envisioned the strange object Hanny van Arkel found in archived images of the night sky.
Caltech astronomers describe the bar scene at the beginning of the universe
Bars abound in spiral galaxies today, but this was not always the case. A group of 16 astronomers, led by Kartik Sheth of NASA's Spitzer Science Center at the California Institute of Technology, has found that bars tripled in number over the past seven billion years, indicating that spiral galaxies evolve in shape.
Hubble finds large sample of very distant galaxies
New Hubble Space Telescope observations of six spectacular galaxy clusters acting as gravitational lenses have given significant insights into the early stages of the Universe. Scientists have found the largest sample of very distant galaxies seen to date: ten promising candidates thought to lie at a distance of 13 billion light-years (~redshift 7.5).
Hubble's sweeping view of the Coma Galaxy Cluster
The NASA/ESA Hubble Space Telescope captures the magnificent starry population of the Coma Cluster of Galaxies, one of the densest known galaxy collections in the Universe.
Team hopes to use new technology to search for ETs
A Johns Hopkins astronomer is a member of a team briefing fellow scientists about plans to use new technology to take advantage of recent, promising ideas on where to search for possible extraterrestrial intelligence in our galaxy.
Astronomers Weigh the Coldest Brown Dwarfs with Astronomy's Sharpest Eyes
Astronomers have used ultrasharp images obtained with the Keck Telescope and Hubble Space Telescope to determine for the first time the masses of the coldest class of "failed stars," a.k.a. brown dwarfs.
Hubble, Keck images show continued turbulence in Jupiter's atmosphere
Increased turbulence and storms first observed on Jupiter more than two years ago are still raging, according to astronomers from the University of California, Berkeley, and the W. M. Keck Observatory in Hawaii, who snapped high-resolution pictures of the planet earlier this month.
More Hubble Space Telescope News Articles
 | The Universe in a Mirror: The Saga of the Hubble Space Telescope and the Visionaries Who Built It by Robert Zimmerman The Hubble Space Telescope has produced the most stunning images of the cosmos humanity has ever seen. It has transformed our understanding of the universe around us, revealing new information about its age and evolution, the life cycle of stars, and the very existence of black holes, among other startling discoveries. The Universe in a Mirror tells the story of this telescope and the visionaries... |
 | Hubble: The Mirror on the Universe by Robin Kerrod, Carole Stott The latest photos from Hubble's recent discoveries, with fascinating new and updated information. After 17 years, 25,000 astronomical targets and more than 700,000 images, the Hubble Space Telescope (HST) continues to return images and data that amaze astronomers. Within the past few months alone, the Hubble has revealed a gold mine of just-formed star systems in the newborn Universe,... |
 | Hubble: 15 Years of Discovery by Lars Lindberg Christensen, Robert A. Fosbury Hubble: 15 Years of Discovery forms a key element of the European Space Agency's 15th anniversary celebration activities for the 1990 launch of the NASA/ESA Hubble Space Telescope. As an observatory in space, Hubble is one of the most successful scientific projects of all time, both in terms of scientific output and its immediate public appeal. Hubble continues to have an enormous impact by... |
 | Hubble Space Telescope: New Views of the Universe by Mark Voit In April 1990, the space shuttle Discovery carried the Hubble Space Telescope to an altitude of some 600 kilometers above the Earth, where it has since been delivering images of the distant heavens to scientists below. Despite disappointing early results--the telescope's mirror and camera were revealed to have significant flaws, which were quickly repaired--Hubble has yielded extraordinary views,... |
 | Space Views from the Hubble Telescope 2009 Wall Calendar by Pomegranate Three and a half centuries after Galileo's revolutionary explorations of the night sky, the Hubble Space Telescope has lifted astronomers still closer to the stars. Accompanying each of this calendar's twelve Hubble images is a concise description of the celestial phenomenon depicted. The calendar also notes important dates in the history of space exploration, as well as current astronomical... |
 | The Hubble Wars: Astrophysics Meets Astropolitics in the Two-Billion-Dollar Struggle over the Hubble Space Telescope, With a New Preface by Eric J. Chaisson The Hubble Space Telescope is the largest, most complex, and most powerful observatory ever deployed in space, designed to allow astronomers to look far back into our own cosmic past with unprecedented clarity. Yet from its launch in 1990, when it was discovered that a flawed mirror was causing severe "myopia" and sending fuzzy images back to Earth, the HST has been at the center of a... |
 | State of the Universe 2008: New Images, Discoveries, and Events (Springer Praxis Books / Popular Astronomy) by Martin Ratcliffe The aim of the State of the Universe annuals is to provide an annual astronomy review suitable for the popular science level reader to be published every September in a format that will be suitable for, and appeal to, the Christmas market. The book will cover all major astronomical news on topics beyond the Solar System and place them in the context of the longer term goals of astronomers and... |
 | Destination: Space by Seymour Simon Exceptional nonfiction for children from two of the most trusted names in science education: Seymour Simon and the Smithsonian Institution.... |
 | Adventures in Space: The Flight to Fix the Hubble by Elaine Scott |
 | New Cosmic Horizons: Space Astronomy from the V2 to the Hubble Space Telescope by David Leverington New Cosmic Horizons tells the extraordinary story of space-based astronomy since the Second World War. Starting with the launch of the V2 rocket in 1946, this book explores the triumphs of space experiments and spacecraft designs and the amazing astronomical results that they have produced. David Leverington examines the fascinating way in which the changing political imperatives of the United... |
| © 2008 BrightSurf.com |