Featured Research

from universities, journals, and other organizations

Hubble Finds That Earth Is Safe From One Class Of Gamma-ray Burst

Date:
May 14, 2006
Source:
Space Telescope Science Institute
Summary:
Homeowners may have to worry about floods, hurricanes, and tornadoes destroying their homes, but at least they can remove long-duration gamma-ray bursts (GRBs) from their list of potential natural disasters, according to recent findings by NASA's Hubble Space Telescope.

This is a sampling of the host galaxies of long-duration gamma-ray bursts taken by NASA's Hubble Space Telescope. Gamma-ray bursts are powerful flashes of high-energy radiation that arise from some supernovae, the explosive deaths of extremely massive stars. Long-duration bursts last more than one to two seconds.
Credit: NASA, ESA, Andrew Fruchter (STScI), and the GRB Optical Studies with HST (GOSH) collaboration

Homeowners may have to worry about floods, hurricanes, and tornadoes destroying their homes, but at least they can remove long-duration gamma-ray bursts (GRBs) from their list of potential natural disasters, according to recent findings by NASA's Hubble Space Telescope.

Related Articles


Long-duration gamma-ray bursts are powerful flashes of high-energy radiation that are sometimes seen coming from certain types of supernovae (the explosions of extremely massive stars). If Earth were flashed by a nearby long-duration burst, the devastation could range from destroying the ozone in our atmosphere to triggering climate change and altering life's evolution.

Now astronomers analyzing long-duration bursts — those lasting more than one to two seconds — in several Hubble telescope surveys have concluded that the Milky Way Galaxy is an unlikely place for them to pop off. They find that blasts tend to occur in small irregular galaxies where stars are deficient in the heavier elements. The Milky Way's starry population, by contrast, is rich in elements heavier than hydrogen and helium.

Suspecting that knowledge of their environments might help determine what types of stars produce gamma-ray bursts, the astronomers, led by Andrew Fruchter of the Space Telescope Science Institute in Baltimore, Md., used Hubble to examine the environments of 42 long-duration bursts and 16 supernovae. They found that the small fraction of supernovae that produce the bursts live in a very different environment from the average supernova. Fruchter's results appear in the May 10 online edition of the journal Nature.

Fruchter's team found that most of the long bursts in the sample were detected in small, faint, misshapen, (irregular) galaxies, which are usually deficient in heavier elements. Only one of the bursts was spotted in a spiral galaxy like our Milky Way, suggesting that our galaxy is an unlikely host for long-duration bursts. By contrast, the hosts of supernovae were divided equally between spiral and irregular galaxies, those with greater or smaller concentrations of the heavier elements.

Fruchter's team also found that long bursts are far more concentrated in the brightest regions of their host galaxies where the most massive stars reside. Supernovae, on the other hand, occur throughout their host galaxies.

"The discovery that long-duration gamma-ray bursts lie in the brightest regions of their host galaxies suggests that they come from the most massive stars – 20 or more times as massive as our Sun," Fruchter said. "Their occurrence in small irregulars implies that only stars that lack heavy chemical elements tend to produce long-duration GRBs." This means that long bursts happened more often in the past when galaxies did not have a large supply of heavy elements. Galaxies build up a stockpile of heavier chemical elements through the ongoing evolution of successive generations of stars. Early generation stars formed before heavier elements were abundant in the universe.

Massive stars abundant in heavy elements are unlikely to trigger bursts because they may lose too much material through stellar "winds" off their surfaces before they collapse and explode. When this happens, the stars don't have enough mass left to produce the proper conditions that would trigger the phenomenon.

Astronomers think that gamma-ray bursts are produced by rotating black holes left over from stellar explosions. The energy from the collapse of a star's core escapes along a narrow jet, like a stream of water from a lawn sprinkler. The jet burns its way through the remnants of the star. The formation of directed jets, which concentrate energy along a narrow beam, would explain why the bursts are so powerful. But if a star loses too much mass, it may only leave behind a neutron star, not a black hole, and thus cannot create the jet. On the other hand, if the star loses too little mass before its collapse, the jet cannot burn its way through the dense outer layers of the star.

This means that extremely high-mass stars that puff away too much material may not be candidates for long bursts. Likewise, neither are stars that give up too little material. "It's a Goldilocks scenario," Fruchter said. "Only supernovae whose progenitor stars have lost some, but not too much, mass appear to be candidates for the formation of GRBs."

Gamma-ray bursts can be divided into two classes: short bursts, which last between milliseconds and about two seconds, and produce very high-energy radiation, and long bursts, which last between two and tens of seconds, and create less energetic gamma rays. Although long bursts are unlikely to strike in galaxies like our Milky Way, short bursts could still happen. Short bursts are believed to arise from collisions between two compact objects, such as neutron stars. However, even with their higher-energy radiation, short bursts are typically 100 to 1,000 times less powerful overall than long bursts and would pose much less of a threat to life if one were to occur in our galaxy.


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 Finds That Earth Is Safe From One Class Of Gamma-ray Burst." ScienceDaily. ScienceDaily, 14 May 2006. <www.sciencedaily.com/releases/2006/05/060512205431.htm>.
Space Telescope Science Institute. (2006, May 14). Hubble Finds That Earth Is Safe From One Class Of Gamma-ray Burst. ScienceDaily. Retrieved October 30, 2014 from www.sciencedaily.com/releases/2006/05/060512205431.htm
Space Telescope Science Institute. "Hubble Finds That Earth Is Safe From One Class Of Gamma-ray Burst." ScienceDaily. www.sciencedaily.com/releases/2006/05/060512205431.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