"Here we have this very bright burst, yet it's surrounded by darkness on all sides," says Brad Cenko of the California Institute of Technology, Pasadena, Calif., lead author of the team’s paper, which has been accepted for publication in The Astrophysical Journal. "The nearest galaxy is more than 88,000 light-years away, and there's almost no gas lying between the burst and Earth."
The blast was detected on January 25, 2007, by several spacecraft of the Inter-Planetary Network. Observations by NASA's Swift satellite pinpointed the explosion, named GRB 070125 for its detection date, to a region of sky in the constellation Gemini. It was one of the brightest bursts of the year, and the Caltech/Penn State team moved quickly to observe the burst’s location with ground-based telescopes.
Using the team's robotic 60-inch telescope at Palomar Observatory in Calif., the astronomers discovered that the burst had a bright and fast-fading afterglow in visible light. This prompted them to observe the afterglow in detail with two of the world's largest telescopes, the 8-meter Gemini North telescope and 10-meter Keck I telescope, both near the summit of Hawaii's Mauna Kea.
What came next was a total surprise. Contrary to experience with more than a hundred previous GRBs, Gemini spectra revealed no signs of dense gas and dust absorbing the light of the afterglow. A trace of magnesium revealed that the burst took place more than 9.4 billion years ago, as deduced by the shift in wavelength of the afterglow’s light, and that the surrounding gas and dust was more tenuous than the environment around any previous burst.
To further pin down the environment that could produce such an unusual explosion, the group obtained Keck images of the location of GRB 070125 long after its afterglow light had faded away. Surprisingly, the resulting images showed no galaxy at this location. "A Keck image could have revealed a very small, faint galaxy at that distance," says coauthor Derek Fox of Penn State. Astronomers have amassed a great deal of evidence that GRBs are triggered by the explosive deaths of massive stars, which live very short lives. Because of their short lifespans, massive stars don’t have time to wander far from their birthplaces, usually dense clouds of gas and dust inside respectable-size galaxies. So GRB 070125 raises the perplexing question of how a massive star could be found so far away from any galaxy.
"Big stars live fast and die young, without much time to move around," says Fox. "So if this massive star died far away from any galaxy, the key question is, how did it manage to be born there?" The formation of massive stars requires similarly massive aggregations of gas and dust, which are usually found in bright galaxies.
One possibility is that the star formed in the outskirts of an interacting galaxy, as seen in the famous Hubble Space Telescope picture of the "Tadpole" galaxy, UGC 10214. "In the local universe, about one percent of star formation happens in tidal tails, on the outskirts of two interacting galaxies," says Cenko. "So it might even make sense to find one in 100 gamma-ray bursts in such an environment."
If this idea is correct, it should be possible to detect the tidal tail hosting GRB 070125 by taking a long exposure with the Hubble Space Telescope. "That's definitely our next stop," says Cenko.
"Many Swift discoveries have left astronomers scratching their heads in befuddlement," adds Swift lead scientist Neil Gehrels of NASA Goddard Space Flight Center in Greenbelt, Md. "But this discovery of a long GRB with no host galaxy is one of the most perplexing of all."
Robert Naeye | EurekAlert!
New NASA study improves search for habitable worlds
20.10.2017 | NASA/Goddard Space Flight Center
Physics boosts artificial intelligence methods
19.10.2017 | California Institute of Technology
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research