Science News & Science Current Events
 
Email a Friend Send to a friend
Printer Friendly Print Astronomers find the most distant star clusters hidden behind a nearby cluster

Astronomers find the most distant star clusters hidden behind a nearby cluster

January 11, 2007

Astronomers find the most distant star clusters hidden behind a nearby cluster

SEATTLE, WA - Astronomers have discovered the most distant population of star clusters ever seen, hidden behind one of the nearest such clusters to Earth. At a distance of more than a billion light-years, the newly discovered star clusters provide a unique probe of what similar systems in our own galaxy once looked like.




"Given their distance, the light that we see today from these clusters was emitted more than one billion years ago and may hold important clues for understanding the evolution of globular clusters," said Jason Kalirai, a postdoctoral fellow at the University of California, Santa Cruz, who will present the findings in a talk at the American Astronomical Society meeting in Seattle.

Kalirai and Harvey Richer of the University of British Columbia led the study, which began as an investigation of a globular star cluster in the Milky Way galaxy known as NGC 6397. The researchers acquired one of the deepest optical images ever taken with the Hubble Space Telescope's Advanced Camera for Surveys, focusing on a small field within NGC 6397. This cluster, home to hundreds of thousands of stars, is 8,500 light-years away, making it one of the closest globular clusters to Earth.

The new data from stars within NGC 6397 have yielded important insights into the age, origin, and evolution of this cluster. Hidden in the background, however, were findings that may hold even greater promise for understanding the evolution of such clusters, Kalirai said. Within the population of stars and galaxies behind NGC 6397, the Hubble image revealed a large elliptical galaxy that contains several hundred globular clusters.

Although each of these clusters probably contains hundreds of thousands of stars, they are so far away from the Earth that each cluster appears as a single faint point of light in the Hubble image. In fact, a single giant star in NGC 6397 appears 10 million times brighter than one of the distant globular clusters. Nevertheless, the faint light from these clusters could yield valuable information, Kalirai said.

Kalirai and Richer followed up the Hubble imaging observations with spectroscopic observations using the Gemini Multi-Object Spectrograph on the Gemini South Telescope on Cerro Pachon in Chile. They were able to determine the distance of the elliptical galaxy hosting the globular clusters by measuring its redshift (a measure of how the expansion of the universe shifts the wavelengths of light from a distant object). This showed that the globular clusters are the most distant ever studied.

"The properties that we infer for these clusters may therefore represent an important clue in understanding what our own Milky Way globulars, such as NGC 6397, looked like in the past," Kalirai said.

Previous studies by other researchers of globular clusters in nearby galaxies, including the Milky Way, have shown that these systems play a very important role in understanding the formation and evolution of galaxies. With a sample of almost 200 clusters in this one distant galaxy, Kalirai's team will test whether the properties of these globulars are consistent with the idea that elliptical galaxies formed the bulk of their stars at early times. For the first time, the observations may also allow astronomers to test for evolution in the properties of globular clusters themselves, Kalirai said.

University of California-Santa Cruz



Related Globular Clusters Current Events and Globular Clusters News Articles Globular Clusters Current Events and Globular Clusters News RSS Globular Clusters Current Events and Globular Clusters News RSS
Black hole found in enigmatic Omega Centauri
A new discovery has resolved some of the mystery surrounding Omega Centauri, the largest and brightest globular cluster in the sky. Images obtained with the Advanced Camera for Surveys onboard the NASA/ESA Hubble Space Telescope and data obtained by the GMOS spectrograph on the Gemini South telescope in Chile show that Omega Centauri appears to harbour an elusive intermediate-mass black hole in its centre.

Galaxy may hold hundreds of rogue black holes
If the latest simulation of what happens when black holes merge is correct, there could be hundreds of rogue black holes, each weighing several thousand times the mass of the sun, roaming around the Milky Way galaxy.

UBC astronomers discover how white dwarf stars get their 'kicks'
University of British Columbia astronomer Harvey Richer and UBC graduate student Saul Davis have discovered that white dwarf stars are born with a natal kick, explaining why these smoldering embers of Sun-like stars are found on the edge rather than at the centre of globular star clusters.

Bonn astronomers simulate life and death in the universe
Stars always evolve in the universe in large groups, known as clusters. Astronomers distinguish these formations by their age and size. The question of how star clusters are created from interstellar gas clouds and why they then develop in different ways has now been answered by researchers at the Argelander Institute for Astronomy at the University of Bonn with the aid of computer simulations.

Hubble sees multiple star generations in a globular cluster
Hubble's observations of the massive globular cluster NGC 2808 provide evidence for three generations of stars that formed early in its life. This is a major upset for conventional theories that propose a single period of star birth.

Star Family Seen Through Dusty Fog
Images made with ESO's New Technology Telescope at La Silla by a team of German astronomers reveal a rich circular cluster of stars in the inner parts of our Galaxy. Located 30,000 light-years away, this previously unknown closely-packed group of about 100,000 stars is most likely a new globular cluster.

Hubble yields direct proof of stellar sorting in a globular cluster
A seven year study with the NASA/ESA Hubble Space Telescope has provided astronomers with the best observational evidence yet that globular clusters sort out stars according to their mass, governed by a gravitational billiard ball game between stars.

Hubble sees faintest stars in a globular cluster
The NASA/ESA Hubble Space Telescope has uncovered what astronomers are reporting as the dimmest stars ever seen in any globular star cluster.

Hubble images some of galaxy's dimmest stars
Using 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.

Astronomers see faintest stars in a globular cluster
Astronomers report in the Aug. 18 issue of the journal Science seeing the faintest stars ever seen in any globular star cluster. The light from these dim stars is only as bright as the light produced by a birthday candle on the moon, as seen from Earth. The astronomers used NASA's Hubble Space Telescope.
More Globular Clusters Current Events and Globular Clusters News Articles
Webb Society Deep-Sky Observers Handbook: Open and Globular Clusters
by Kenneth Glyn



Globular Cluster Systems (Cambridge Astrophysics)
by Keith M. Ashman, Stephen E. Zepf

Globular clusters are roughly spherical, densely packed groups of stars found around galaxies. Most globular clusters probably formed at the same time as their host galaxies. Therefore they provide a unique fossil record of the conditions during the formation and early evolution of galaxies. This volume presents a comprehensive review of globular cluster systems. It summarizes their observed...

Webb Society Deep-Sky Observers Handbook: Open and Globular Clusters

Structure and Dynamics of Globular Clusters (Asp Conference Series Publications : Volume 50)

Chemical Abundance in Globular Cluster Turn-off Stars from Keck/HIRES Observations
by Ann Merchant; Stephens, Alex; King, Jeremy; Deliyannis, Constantine Boesgaard

Luminosity Functions of Old and Intermediate-Age Globular Clusters in NGC 3610 (Preprint Series 1543)
by Bradley; Schweizer, Francois; Kundu, Arunav; Miller, Bryan Whitmore

Deep Mixing in Globular-cluster Red Giants (Y)
by Pavel Denissenkov

Astrophysical Parameters for Globular Clusters
by A. G. Davis & Hayes, D. S. (Eds) Philip

Very Large Telescope Observations of the Peculiar Globular Cluster NGC 6712. Discovery of a UV H(alpha) Excess Star in the Core
by F. R.; Paltrinieri, B.; Paresce, F.; de marchi, G. Ferraro



Globular Clusters (Cambridge Contemporary Astrophysics)
by C. Mart^D'inez Roger, I. P^D'erez Fournon, F. S^D'anchez

Globular clusters are spherical, densely packed groups of stars found around galaxies. They are thought to have formed at the same time as their host galaxy and thus provide a powerful probe for understanding galaxy evolution, as well as being studied as objects of interest in their own right. This volume presents invited articles by a team of world leaders who gathered at the X Canary Islands...

© 2008 BrightSurf.com