A minor speck of light flashed March 19, barely illuminating the night sky, representing the death of a star long before Earth’s formation. In the constellation Boötes, in a galaxy located 7.5 billion light years away from Earth, this burst was the grand finale of enormous gamma ray explosions, notorious among astronomers for their violence and magnitude.
This explosive gamma ray burst, named GRB 080319B for the date of its sighting, set the record for the most distant object visible to the naked human eye. (New York Times) Although barely visible, this burst was 10 million times as bright as a supernova would have appeared at the same distance from Earth, according to NASA experts. Gamma ray bursts are believed to be the most luminous explosions to follow the big bang, and this particular burst had an afterglow 2.5 million times more luminous than the previous record holder, qualifying this burst as the brightest object to be observed by Earth. (Fox News)
Gamma ray bursts usually indicate the collision of dense neutron stars or the implosion of a massive star running out of nuclear fuel, causing a black hole to form in its place. The collision or implosion results in the explosive burst of high-energy gamma rays, along with the release of inflamed particle jets that race through the universe at just under the speed of light. This particular star was 40 times larger than our sun.
Given that the universe is approximately 14 billion years old, the light from the Boötes burst has been travelling to our line of vision for half the age of the universe, long before the formation of our solar system. The burst was detected by NASA’s Swift satellite, which alerted numerous self-operating telescopes across the world to redirect their attention to the coordinates specified by the satellite. These telescopes captured the optical afterglow of the brief burst. (New York Times)
By recording and inspecting the spectral measurements of the burst, the telescopes were able to calculate the approximate distance of the glow. This is done by measuring the glow’s redshift – or the shift that emits red waves representing the object’s movement away from the observer – and estimations based on similar data of locations in an ever-expanding universe. (New York Times) Both the Hobby-Eberly Telescope in Texas and the Very Large Telescope in Chile measured the redshift to be 0.94, indicating a distance of about 7.5 billion light years.
It is still unknown to astronomers why this particular burst was so powerful and its afterglow so luminous. Some have theorized that the burst was simply more energetic than most, due to the mass, velocity or magnetic field power surrounding the preexisting star.