Featured Research

from universities, journals, and other organizations

Energized "Heartbeats" May Explain Why Galaxies Are Continually Stirred Up, UCSD Researchers Say

Date:
November 1, 2002
Source:
University Of California - San Diego
Summary:
Until now, astronomers haven't been able to offer a full explanation for why the Milky Way and other galaxies produce new stars at a relative snail's pace. While they have known for decades that high turbulence keeps huge clouds of hydrogen gas from condensing into stars, they haven't identified all the causes of the galactic perturbations.

Until now, astronomers haven't been able to offer a full explanation for why the Milky Way and other galaxies produce new stars at a relative snail's pace. While they have known for decades that high turbulence keeps huge clouds of hydrogen gas from condensing into stars, they haven't identified all the causes of the galactic perturbations.

Related Articles


In a report to be published in the November 20 issue of Astrophysical Journal Letters, researchers at the University of California, San Diego have discovered that a well-known, but overlooked source of heating--regular outbursts of ultraviolet radiation from clusters of very large, bright stars--may play a significant role in keeping the Milky Way's gas continually stirred up.

In a rapid-release online publication of the report today, Alexei G. Kritsuk, a visiting researcher at UCSD, and Michael L. Norman, a professor of physics at UCSD and a senior fellow at UCSD's San Diego Supercomputer Center, detailed their findings, which were made with a sophisticated hydrodynamic computer simulation.

"The most massive and brightest stars in the spiral arms of our galaxy emit lots of ultraviolet radiation in regular cycles," said Norman. As clouds of cold, dense gas condense into very bright stars, the ultraviolet radiation they emit dissipates the remaining clouds of gas, which causes further star formation to slow considerably. "We think this radiation may act as an important regulation mechanism, providing a feedback effect from star-formation that may inhibit further star formation," he said.

Light with wavelengths shorter than the human eye can see is called ultraviolet (beyond violet) light, and its energy is readily transferred to gas clouds in galaxies. (The sun also produces ultraviolet light, which is absorbed by the ozone layer in Earth's atmosphere or reflected back into space.)

Astrophysicists agree that some form of energy must be supplied to gases in the so-called interstellar medium of galaxies to sustain the turbulence that astronomers have noted in beautiful images of the spiral arms of the Milky Way and nearby galaxies. Researchers have identified a variety of potential energy sources that in some situations could maintain the turbulence--such as violent stellar explosions called supernovae, or blasts of supersonic "winds" given off by massive newborn stars.

"Astronomers have been thinking about these mechanical effects for several decades, but not really considering the radiation effects, which travel at the speed of light and exert a heating effect much farther away than a supernova shock or a stellar wind," said Norman. "Ultraviolet radiation may not be the complete answer to all the galactic turbulence, but I'm confident that it plays some role in what astronomers call the interstellar medium."

In a research paper published online this year at http://lanl.arXiv.org/abs/astro-ph/0202196, a group of researchers led by Venezuelan astrophysicist Antonio Parravano reported that large, bright stars generate large, bursts of ultraviolet radiation on timescales of about 10 million years. Norman and Kritsuk used Parravano's findings as the starting point for their simulation studies.

"The ultraviolet radiation in a huge section of the Milky Way's disk goes up by a factor of two to 10 and then, falls, and then repeats like heartbeats," said Kritsuk. "Our numerical simulations show that this time-dependent heating of the interstellar medium would be a good driving force for the filaments and blobby sheets of gas actually observed by astronomers in the regions of the galaxy where background ultraviolet radiation is the main source of energy."

Kritsuk and Norman used supercomputers at the San Diego Supercomputer Center at UCSD and the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign. The machines are provided by the National Science Foundation to enable computationally intensive approaches to astrophysical research by scientists at dozens of colleges and universities in the United States.


Story Source:

The above story is based on materials provided by University Of California - San Diego. Note: Materials may be edited for content and length.


Cite This Page:

University Of California - San Diego. "Energized "Heartbeats" May Explain Why Galaxies Are Continually Stirred Up, UCSD Researchers Say." ScienceDaily. ScienceDaily, 1 November 2002. <www.sciencedaily.com/releases/2002/10/021031074647.htm>.
University Of California - San Diego. (2002, November 1). Energized "Heartbeats" May Explain Why Galaxies Are Continually Stirred Up, UCSD Researchers Say. ScienceDaily. Retrieved March 26, 2015 from www.sciencedaily.com/releases/2002/10/021031074647.htm
University Of California - San Diego. "Energized "Heartbeats" May Explain Why Galaxies Are Continually Stirred Up, UCSD Researchers Say." ScienceDaily. www.sciencedaily.com/releases/2002/10/021031074647.htm (accessed March 26, 2015).

Share This


More From ScienceDaily



More Space & Time News

Thursday, March 26, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Supermassive Blackhole Detector Ready for Business

Supermassive Blackhole Detector Ready for Business

Reuters - Innovations Video Online (Mar. 25, 2015) Construction of the world&apos;s largest and most powerful observatory designed to detect and analyze gamma rays has been completed in Mexico. Gamma ray particles are considered the most energetic in the universe and scientists hope to use the observatory to learn more about the supernovas and black holes that produce them. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com
Rocket Blasts Off Carrying U.S. Air Force GPS Satellite

Rocket Blasts Off Carrying U.S. Air Force GPS Satellite

Reuters - News Video Online (Mar. 25, 2015) A U.S. Air Force GPS IIF-9 satellite launches aboard a United Launch Alliance Delta IV rocket into semi-synchronous orbit. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Opportunity's Marathon: The Mars Rover Just Keeps Going

Opportunity's Marathon: The Mars Rover Just Keeps Going

Newsy (Mar. 24, 2015) NASA&apos;s Opportunity Mars Rover finished a full marathon, making it the first human creation to do a full 26.2 miles on another planet. Video provided by Newsy
Powered by NewsLook.com
Twin Astronaut to Break NASA Record in Study

Twin Astronaut to Break NASA Record in Study

AP (Mar. 23, 2015) NASA astronaut Scott Kelly will be the first American to spend a year aboard the International Space Station in an experiment to test human endurance in space, while his twin brother&apos;s health is compared on Earth. (March 23) 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