Featured Research

from universities, journals, and other organizations

Astronomers Find First Ever Gamma Ray Clock

Date:
November 28, 2006
Source:
Particle Physics & Astronomy Research Council
Summary:
Astronomers using the H.E.S.S. telescopes have discovered the first ever modulated signal from space in Very High Energy Gamma Rays -- the most energetic such signal ever observed. Regular signals from space have been known since the 1960s, when the first radio pulsar (nicknamed Little Green Men-1 for its regular nature) was discovered. This is the first time a signal has been seen at such high energies -- 100,000 times higher than previously known.

Map of the gamma ray sky in the region of LS5039. The green star shows the position of LS5039 as measured using radio telescopes and the white ellipse shows the gamma ray position.
Credit: Image courtesy of Particle Physics & Astronomy Research Council

Astronomers using the H.E.S.S. telescopes have discovered the first ever modulated signal from space in Very High Energy Gamma Rays -- the most energetic such signal ever observed. Regular signals from space have been known since the 1960s, when the first radio pulsar (nicknamed Little Green Men-1 for its regular nature) was discovered. This is the first time a signal has been seen at such high energies -- 100,000 times higher than previously known - and is reported today (24th November) in the Journal Astronomy and Astrophysics.

Related Articles


The signal comes from a system called LS 5039 which was discovered by the H.E.S.S. team in 2005. LS5039 is a binary system formed of a massive blue star (20 times the mass of the Sun) and an unknown object, possibly a black hole. The two objects orbit each other at very short distance, varying between only 1/5 and 2/5 of the separation of the Earth from the Sun, with one orbit completed every four days.

"The way in which the gamma ray signal varies makes LS5039 a unique laboratory for studying particle acceleration near compact objects such as black holes." Explained Dr Paula Chadwick from the University of Durham, a British team member of H.E.S.S.

Different mechanisms can affect the gamma-ray signal that reaches Earth and by seeing how the signal varies, astronomers can learn a great deal about binary systems such as LS 5039 and also the effects that take place near black holes.

As it dives towards the blue-giant star, the compact companion is exposed to the strong stellar 'wind' and the intense light radiated by the star, allowing on the one hand particles to be accelerated to high energies, but at the same time making it increasingly difficult for gamma rays produced by these particles to escape, depending on the orientation of the system with respect to us. The interplay of these two effects is at the root of the complex modulation pattern.

The gamma-ray signal is strongest when the compact object (thought to be a black hole) is in front of the star as seen from Earth and weakest when it is behind the star. The gamma rays are thought to be produced as particles which are accelerated in the star's atmosphere (the stellar wind) interact with the compact object. The compact object acts as a probe of the star's environment, showing how the magnetic field varies depending on distance from the star by mirroring those changes in the gamma ray signal.

In addition, a geometrical effect adds a further modulation to the flux of gamma-rays observed from the Earth. We know since Einstein derived his famous equation (E=mc²) that matter and energy are equivalent, and that pairs of particles and antiparticles can mutually annihilate to give light. Symmetrically, when very energetic gamma rays meet the light from a massive star, they can be converted into matter (an electron-positron pair in this case). So, the light from the star resembles, for gamma rays, a fog which masks the source of the gamma rays when the compact object is behind the star, partially eclipsing the source. "The periodic absorption of gamma-rays is a nice illustration of the production of matter-antimatter pairs by light, though it also obscures the view to the particle accelerator in this system" (Guillaume Dubus, Astrophysical Laboratory of the Grenoble Observatory, LAOG).

UK work on H.E.S.S. is funded by the Particle Physics and Astronomy Research Council.


Story Source:

The above story is based on materials provided by Particle Physics & Astronomy Research Council. Note: Materials may be edited for content and length.


Cite This Page:

Particle Physics & Astronomy Research Council. "Astronomers Find First Ever Gamma Ray Clock." ScienceDaily. ScienceDaily, 28 November 2006. <www.sciencedaily.com/releases/2006/11/061128083953.htm>.
Particle Physics & Astronomy Research Council. (2006, November 28). Astronomers Find First Ever Gamma Ray Clock. ScienceDaily. Retrieved December 28, 2014 from www.sciencedaily.com/releases/2006/11/061128083953.htm
Particle Physics & Astronomy Research Council. "Astronomers Find First Ever Gamma Ray Clock." ScienceDaily. www.sciencedaily.com/releases/2006/11/061128083953.htm (accessed December 28, 2014).

Share This


More From ScienceDaily



More Space & Time News

Sunday, December 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

NASA Cameras Capture Solar Flare

NASA Cameras Capture Solar Flare

Reuters - US Online Video (Dec. 25, 2014) — NASA cameras capture images of intense solar flare on the sun. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
NASA Proposes Studying Venus With Blimps

NASA Proposes Studying Venus With Blimps

Buzz60 (Dec. 24, 2014) — NASA is proposing a way of studying the toxic surface of Venus by using blimps. They've created a video to highlight their ideas for the project called HAVOC. Patrick Jones (@Patrick_E_Jones) explains. Video provided by Buzz60
Powered by NewsLook.com
NASA Prepares for Next Phase of Hubble Successor

NASA Prepares for Next Phase of Hubble Successor

Reuters - Innovations Video Online (Dec. 22, 2014) — Scientists and engineers prepare for the next phase of the James Webb Space Telescope, the scientific successor to the Hubble. Nathan Frandino reports. Video provided by Reuters
Powered by NewsLook.com
Spokesman: 'NORAD Ready to Track Santa'

Spokesman: 'NORAD Ready to Track Santa'

AP (Dec. 19, 2014) — Pentagon spokesman Rear Adm. John Kirby said that NORAD is ready to track Santa Claus as he delivers gifts next week. Speaking tongue-in-cheek, he said if Santa drops anything off his sleigh, "we've got destroyers out there to pick them up." (Dec. 19) 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