Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hubble finds multiple stellar “baby booms” in a globular cluster

02.05.2007
Analysis of Hubble observations of the massive globular cluster NGC 2808 provides evidence that it has three generations of stars that formed early in the cluster’s life. This is a major upset for conventional theories as astronomers have long thought that globular star clusters had a single “baby boom” of stars early in their lives and then settled down into a long, quiet middle age.

New observations by the NASA/ESA Hubble Space Telescope have overturned conventional ideas about the early life of some massive globular clusters, showing that they can go through several periods of intense stellar formation rather than the previously accepted single burst. The analysis of Hubble data from the massive globular cluster NGC 2808 provides evidence that star birth occurred over three generations early in the cluster’s life.

“We had never imagined that anything like this could happen,” said Giampaolo Piotto of the University of Padua in Italy and leader of the team that made the discovery. “This is a complete shock.”

Globular clusters are among the earliest settlers of our Milky Way Galaxy, born during our Galaxy’s formation. A typical cluster consists of hundreds of thousands of stars held together by gravity in a compact swarm.

“The standard picture of a globular cluster is that all of its stars formed at the same time, in the same place, and from the same material, and that they have co-evolved for billions of years,” said team member Luigi Bedin of ESO in Garching, Germany, the European Space Agency, and Space Telescope Science Institute in Baltimore, USA. “This is the cornerstone on which much of the study of stellar populations has been built. So we were very surprised to find several distinct populations of stars in NGC 2808. All of the stars were born within 200 million years very early in the life of the 12.5-billion-year-old massive cluster.”

Finding multiple stellar populations in a globular cluster so close to home has deep cosmological implications, the researchers said. "We need to do our best to solve the enigma of these multiple generations of stars found in these Hubble observations so that we can understand how stars formed in distant galaxies in our early Universe," Piotto explained.

The astronomers used Hubble’s Advanced Camera for Surveys to measure the brightness and colour of the cluster stars. Hubble's exquisite resolution allowed the astronomers to sort out the different stellar populations. The Hubble measurements showed three distinct populations, with each successive generation appearing slightly bluer. This colour difference suggests that successive generations contain a slightly different mix of some chemical elements.

“One assumption, although we have no direct proof,” said team member Ivan King of the University of Washington in Seattle, USA, “is that the amount of helium increases with each generation of stars. The successively bluer colour of the stellar populations indicates that the amount of helium increases in each generation. Perhaps massive star clusters like NGC 2808 hold onto enough gas to ignite a rapid succession of stars.”

The star birth would be driven by shock waves from supernovae and stellar winds from red giant stars, which compress the gas and make new stars, King explained. The gas would be increasingly enriched in helium from previous generations of stars more massive than the Sun.

Astronomers commonly assumed that globular clusters produce only one stellar generation because the energy radiating from the first batch of stars would clear out most of the residual gas needed to make more stars. But a hefty cluster like NGC 2808 is two to three times more massive than a typical globular cluster and may have sufficient gravity to hang onto enough gas, which is then enriched by helium from the first stars. Of the about 150 known globular clusters in our Milky Way Galaxy, NGC 2808 is one of the most massive, containing more than 1 million stars.

Another possible explanation for the multiple stellar populations is that NGC 2808 may only be masquerading as a globular cluster. The stellar grouping may have been a dwarf galaxy that was stripped of most of its material due to gravitational capture by our Milky Way.

Omega Centauri, the first globular cluster Piotto’s group found to have multiple generations of stars, is suspected to be the remnant core of a dwarf galaxy, Bedin said.

Although the astronomers have searched only two globular clusters for multiple stellar populations, they say this may be a typical occurrence in other massive clusters.

“No one would make the radical step of suggesting that previous work on other clusters is no longer valid,” King said. “But this discovery shows that the study of stellar populations in globular clusters now opens up in a new direction.”

The team plans to use ESO’s Very Large Telescope in Chile to make spectroscopic observations of the chemical abundances in NGC 2808, which may offer further evidence that the stars were born at different times and yield clues to how they formed. They also will use Hubble to hunt for multiple generations of stars in about 10 more hefty globular clusters.

Lars Christensen | alfa
Further information:
http://www.spacetelescope.org/news/html/heic0708.html

More articles from Physics and Astronomy:

nachricht A better way to weigh millions of solitary stars
15.12.2017 | Vanderbilt University

nachricht A chip for environmental and health monitoring
15.12.2017 | Friedrich-Alexander-Universität Erlangen-Nürnberg

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First-of-its-kind chemical oscillator offers new level of molecular control

DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.

Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

Engineers program tiny robots to move, think like insects

15.12.2017 | Power and Electrical Engineering

One in 5 materials chemistry papers may be wrong, study suggests

15.12.2017 | Materials Sciences

New antbird species discovered in Peru by LSU ornithologists

15.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>