July 18, 2013
Neutron Star Collisions May Have Created All The Gold In The Universe
[ Watch the Video: Merging Neutron Stars ]
redOrbit Staff & Wire Reports - Your Universe OnlineA gamma-ray burst (GRB) created by the collision of two neutron stars has given researchers new insight into how gold, one of the rarest elements on Earth, and in the entire universe, is formed.
Lead author Edo Berger of the Harvard-Smithsonian Center for Astrophysics (CfA) and his colleagues explain that unlike elements such as carbon or iron, gold cannot be created inside of a star.
Rather, it has to be formed as the result of a more cataclysmic event, such as the GRB that astronomers observed back in June. Observations of the GRB provided evidence that gold resulted from the collision of two neutron stars - the dead cores of stars that had previously exploded as supernovae, according to the CfA.
Additionally, scientists observed an unusual glow that lasted at the burst's location for several days, potentially signifying that a substantial amount of gold and other heavy elements were created as a result of the collision.
"We estimate that the amount of gold produced and ejected during the merger of the two neutron stars may be as large as 10 moon masses - quite a lot of bling!" Berger explained. "To paraphrase Carl Sagan, we are all star stuff, and our jewelry is colliding-star stuff."
Berger presented his team's findings at a press conference at the CfA in Cambridge, Massachusetts on Wednesday. In addition, he and co-authors Wen-fai Fong and Ryan Chornock have submitted a paper describing their results to The Astrophysical Journal Letters.
The researchers explain that a gamma-ray burst is a flash of high-energy light caused by an extremely energetic explosion, typically found in the distant universe. The burst studied by Berger's team is known as GRB 130603B, and at 3.9 billion light-years from Earth it is one of the nearest such events ever observed.
There are two types of gamma-ray bursts - long and short - depending upon the duration of the gamma rays' flash. GRB 130603B, which was detected by the NASA Swift satellite on June 3, lasted for less than two-tenths of a second, the study authors said.
Despite disappearing quickly, GRB 130603B also displayed a slowly fading glow that was dominated by infrared light, and its brightness and behavior did not match the typical "afterglow" created when a high-speed jet of particles collides with its surrounding environments, Berger and his associated noted.
Based on the behavior of the glow, they believe that it most likely originated from exotic radioactive elements. Those elements can be generated from the neutron-rich material ejected by colliding neutron stars, which ultimately undergo radioactive decay and emit the same type of infrared light observed by the CfA researchers.
"We've been looking for a 'smoking gun' to link a short gamma-ray burst with a neutron star collision," said Fong, who is a graduate student at the center. She, Berger and Chornock calculate that approximately about one-hundredth of a solar mass of material was ejected by the gamma-ray burst, and that some of it was gold.
By combining estimates about the amount of the rare metallic element produced from a lone short GRB with the number of explosions believed to have occurred throughout the history of the universe, they assert that all of the gold existing throughout the cosmos could have been created as the result of gamma-ray bursts.