Subscribe free to our newsletters via your
. 24/7 Space News .




STELLAR CHEMISTRY
Galaxies are running out of gas
by Staff Writers
Canberra, Australia (SPX) Aug 30, 2011


Mopra radio telescope, near Coonabarabran, NSW. Image credit - CSIRO.

The Universe forms fewer stars than it used to, and a CSIRO study has now shown why - the galaxies are running out of gas. Dr Robert Braun (CSIRO Astronomy and Space Science) and his colleagues used CSIRO's Mopra radio telescope near Coonabarabran, NSW, to study far-off galaxies and compare them with nearby ones.

Light (and radio waves) from the distant galaxies has taken time to travel to us, so we see the galaxies as they were between three and five billion years ago.

Galaxies at this stage of the Universe's life appear to contain considerably more molecular hydrogen gas than comparable galaxies in today's Universe, the research team found.

Stars form from clouds of molecular hydrogen. The less molecular hydrogen there is, the fewer stars will form.

The research team's paper is in press in Monthly Notices of the Royal Astronomical Society.

Astronomers have known for at least 15 years that the rate of star formation peaked when the Universe was only a few billion years old and has declined steeply ever since.

"Our result helps us understand why the lights are going out," Dr Braun said.

"Star formation has used up most of the available molecular hydrogen gas."

After stars form, they shed gas during various stages of their lives, or in dramatic events such as explosions (supernovae).

This returns some gas to space to contribute to further star formation.

"But most of the original gas-about 70%-remains locked up, having been turned into things such as white dwarfs, neutron stars and planets," Dr Braun said.

"So the molecular gas is used up over time. We find that the decline in the molecular gas is similar to the pattern of decline in star formation, although during the time interval that we have studied, it is declining even more rapidly."

Ultimately, the real problem is the rate at which galaxies are 'refueled' from outside.

Gas falls into galaxies from the space between galaxies, the intergalactic medium. Two-thirds of the gas in the universe is still found in the intergalactic medium and only one third has already been consumed by previous star formation in galaxies, astronomers think.

"The drop-off in both gas availability and star formation seems to have started around the time that Dark Energy took control of the Universe," Dr Braun said.

Up until that time, gravity dominated the Universe, so the gas was naturally pulled in to galaxies, but then the effect of Dark Energy took over and the Universe started expanding faster and faster.

This accelerating expansion will have made it increasingly difficult for galaxies to capture the additional gas they need to fuel future generations of star formation, Dr Braun speculates.

The galaxies used for the Mopra study were of a kind called ultra-luminous infra-red galaxies or ULIRGs, chosen because they are known to have large reservoirs of gas and because they are so bright that there was a complete census of them within the volume of the Universe that the team studied. They ranged in redshift from 0.2 to 0.5 (that is, they had a look-back time of three to five billion years).

Molecular hydrogen is difficult to detect directly, and this study (like many previous studies) used emission from carbon monoxide (CO) as a proxy for the molecular hydrogen.

The astronomers observed the emission arising from the CO(1-0) transition: this study is significant because most other studies have had to rely on observing different transition lines for galaxies at different redshifts. This study, however, compared "apples with apples", using CO(1-0) for both the nearby and distant galaxies under study.

.


Related Links
CSIRO Astronomy and Space Science
Stellar Chemistry, The Universe And All Within It






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle








STELLAR CHEMISTRY
Notre Dame astrophysicists identify missing fuel for galactic star formation
Notre Dame IN (SPX) Aug 29, 2011
The Milky Way will have the fuel to continue forming stars, thanks to massive clouds of ionized gas raining down from its halo and intergalactic space. This is the conclusion of a new study by Nicolas Lehner and Christopher Howk, faculty in the Department of Physics at the University of Notre Dame. Their report, "A Reservoir of Ionized Gas in the Galactic Halo to Sustain Star Formation in ... read more


STELLAR CHEMISTRY
Armstrong relives historic Moon landing

NASA's Next Generation Robotic Lander Gets Sideways During Test

Moon Express Gets Thumbs-Up from NASA for Developing New Lunar Landing Technology

NASA Moon Mission in Final Preparations for September Launch

STELLAR CHEMISTRY
Out of Thin Martian Air

Russian, European space agencies to team up for Mars mission

New Rover Snapshots Capture Endeavour Crater Vistas

France, Russia talk of Mars mission

STELLAR CHEMISTRY
NASA Aeronautics Is Focus Of Research And Technology Roundtable

New Report Analyzes Development Paths of Emerging Space Nations and Sustainable Use of Outer Space

First Soyuz launch from Kourou to go ahead: Arianespace

Recent grad's astro feats regarded as research crown 'joule'

STELLAR CHEMISTRY
Orbits for Tiangong

Chinese orbiter launch failure will not affect unmanned space module launch

Rocket malfunction causes satellite to not reach preset orbit

China satellite aborts mission after 'malfunction'

STELLAR CHEMISTRY
The next ATV resupply spacecraft arrives next mission to ISS

Russia delays next manned space flight

Thales Alenia Space's Cygnus PCM shipped to United States

Resupply Craft Lost While Crew Focuses on Departure and Science

STELLAR CHEMISTRY
Progress space freighter destroyed in atmosphere

Russia to test launch Soyuz rockets before delivering ISS crews

The fifth Ariane 5 of 2011 is ready for integration of its dual-satellite payload

Glonass-M satellite launch postponed for additional check

STELLAR CHEMISTRY
Greenhouse Effect Could Extend Habitable Zone

A Planet Made of Diamond

Astronomers Find Ice and Possibly Methane on Snow White

Hubble to Target 'Hot Jupiters'

STELLAR CHEMISTRY
Scientists put a new spin on traditional information technology

HP plans one last production run for the TouchPad

Indian MPs get iPad lessons to cut paperwork

Amazon tablet seen as worthy iPad rival




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement