Featured Research

from universities, journals, and other organizations

Hubble catches end of star-making party in nearby dwarf galaxy

Date:
February 3, 2010
Source:
Space Telescope Science Institute
Summary:
Galaxies throughout the universe are ablaze with star birth. But for a nearby, small spiral galaxy, the star-making party is almost over. Astronomers were surprised to find that star-formation activities in the outer regions of NGC 2976 have been virtually asleep because they shut down millions of years ago. The celebration is confined to a few die-hard partygoers huddled in the galaxy's inner region.

NGC 2976 does not look like a typical spiral galaxy, as this NASA Hubble Space Telescope image shows. In this view of the oddball galaxy's inner region, there are no obvious spiral arms. Dusty filaments running through the disk show no clear spiral structure. A raucous interaction with a neighboring group of hefty galaxies stripped away some gas and funneled the rest to the galaxy's inner region, fueling star birth about 500 million years ago. At the same time, the galaxy's outer regions stopped making stars because the gas ran out. Now, the inner disk is almost out of gas as new stars burst to life, shrinking the star-formation region to a small area of about 5,000 light-years around the core.
Credit: NASA, ESA, and J. Dalcanton and B. Williams (University of Washington, Seattle)

Galaxies throughout the universe are ablaze with star birth. But for a nearby, small spiral galaxy, the star-making party is almost over.

Related Articles


Astronomers were surprised to find that star-formation activities in the outer regions of NGC 2976 have been virtually asleep because they shut down millions of years ago. The celebration is confined to a few die-hard partygoers huddled in the galaxy's inner region.

The explanation, astronomers say, is that a raucous interaction with a neighboring group of hefty galaxies ignited star birth in NGC 2976. Now the star-making fun is beginning to end. Images from NASA's Hubble Space Telescope show that star formation in the galaxy began fizzling out in its outskirts as some of the gas was stripped away and the rest collapsed toward the center. With no gas left to fuel the party, more and more regions of the galaxy are taking a much-needed nap.

"Astronomers thought that grazing encounters between galaxies can cause the funneling of gas into a galaxy's core, but these Hubble observations provide the clearest view of this phenomenon," explains astronomer Benjamin Williams of the University of Washington in Seattle, who directed the Hubble study, which is part of the ACS Nearby Galaxy Survey Treasury (ANGST) program. "We are catching this galaxy at a very interesting time. Another 500 million years and the party will be over."

NGC 2976 does not look like a typical spiral galaxy. It has a star-forming disk, but no obvious spiral pattern. Its gas is centrally concentrated, but it does not have a central bulge of stars. The galaxy resides on the fringe of the M81 group of galaxies, located about 12 million light-years away in the constellation Ursa Major.

"The galaxy looks weird because an interaction with the M81 group about a billion years ago stripped some gas from the outer parts of the galaxy, forcing the rest of the gas to rush toward the galaxy's center, where it is has little organized spiral structure," Williams says.

The tsunami of gas racing toward the center has fueled rapid star birth for at least the past 500 million years in the relatively armless disk. At the same time, star birth ended in the galaxy's outer regions because the gas ran out. Now, the inner disk is running out of gas as new stars burst to life, shrinking the star-birth zone to a 5,000-light-year-wide area around the core.

"At one point during this process, the density of gas in the inner regions of this galaxy was very high, about five times higher than it is today," explains Julianne Dalcanton of the University of Washington, and leader of the ANGST team. "The gas vanished incredibly fast, and the galaxy now appears to be settling down."

Astronomers pieced together this star-formation story with the help of Hubble's sharp vision. The galaxy's relatively close distance to Earth allowed Hubble's Advanced Camera for Surveys (ACS) to resolve hundreds of thousands of individual stars. By studying those stars, the astronomers determined their color and brightness, which provided information about when the stars formed. The astronomers combined the Hubble results with a map, made from radio observations, showing the current distribution of hydrogen across the galaxy. The map is part of The HI Nearby Galaxy Survey by the National Radio Astronomy Observatory's Very Large Array in New Mexico. By analyzing the combined data, Williams and the team then reconstructed the star-making history for large areas of the galaxy.

"This type of observation is unique to Hubble," Williams says. "If we had not been able to pick out individual stars, we would have known that the galaxy is weird, but we would not have dug up evidence for a significant gas rearrangement in the galaxy, which caused the stellar birth zone to shrink toward the galaxy's center."

Simulations predict that the same "gas-funneling" mechanism may trigger starbursts in the central regions of other dwarf galaxies that interact with larger neighbors. The trick to studying the effects of this process in detail, Williams says, is being able to resolve many individual stars in galaxies to create an accurate picture of their evolution.

Williams' results will appear in the January 20, 2010 issue of The Astrophysical Journal.


Story Source:

The above story is based on materials provided by Space Telescope Science Institute. Note: Materials may be edited for content and length.


Cite This Page:

Space Telescope Science Institute. "Hubble catches end of star-making party in nearby dwarf galaxy." ScienceDaily. ScienceDaily, 3 February 2010. <www.sciencedaily.com/releases/2010/02/100202110743.htm>.
Space Telescope Science Institute. (2010, February 3). Hubble catches end of star-making party in nearby dwarf galaxy. ScienceDaily. Retrieved October 30, 2014 from www.sciencedaily.com/releases/2010/02/100202110743.htm
Space Telescope Science Institute. "Hubble catches end of star-making party in nearby dwarf galaxy." ScienceDaily. www.sciencedaily.com/releases/2010/02/100202110743.htm (accessed October 30, 2014).

Share This



More Space & Time News

Thursday, October 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Antares Liftoff Explosion

Raw: Antares Liftoff Explosion

AP (Oct. 29, 2014) Observers near Wallops Island recorded what they thought would be a routine rocket launch Tuesday night. What they recorded was a major rocket explosion shortly after lift off. (Oct 29) Video provided by AP
Powered by NewsLook.com
Raw: Russian Cargo Ship Docks at Space Station

Raw: Russian Cargo Ship Docks at Space Station

AP (Oct. 29, 2014) Just hours after an American cargo run to the International Space Station ended in flames, a Russian supply ship has arrived at the station with a load of fresh supplies. (Oct. 29) Video provided by AP
Powered by NewsLook.com
Journalist Captures Moment of Antares Rocket Explosion

Journalist Captures Moment of Antares Rocket Explosion

Reuters - US Online Video (Oct. 29, 2014) A space education journalist is among those who witness and record the explosion of an unmanned Antares rocket seconds after its launch. Rough Cut (no reporter narration) Video provided by Reuters
Powered by NewsLook.com
Rocket Explosion Under Investigation

Rocket Explosion Under Investigation

AP (Oct. 28, 2014) NASA and Orbital Sciences officials say they are investigating the explosion of an unmanned commercial supply rocket bound for the International Space Station. It blew up moments after liftoff Tuesday evening over the launch site in Virginia. (Oct. 28) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins