The Atacama Large Millimeter/submillimeter Array (ALMA) observed for the first time mapped out gamma-ray bursts (GRBs), and found that the Universe's biggest explosions are shrouded in more dust than previously thought.
GRBs are intense bursts of extremely high energy seen in distant galaxies. Releasing as much energy as the Sun will in its entire ten-billion-year lifetime, they are the brightest explosive phenomenon in the Universe. Some can even last as little as a couple of seconds, referred to as long-duration gamma-ray bursts (LGRBs), and associated with supernovas.
An afterglow, or slowly fading emission, is observed during the aftermath of such an explosion, which is supposedly created by collisions between the ejected material and the surrounding gas.
But some GRBs, called "dark GRBs," appear to have no afterglow - scientists believe surrounding clouds of dust absorb the afterglow radiation.
In an attempt to solve the mystery, scientists started studying their host galaxies, expecting to find active stars shrouded in clouds of molecular gas - the fuel for star formation - believed to be GRB precursors.
They found no such evidence until recently, when Bunyo Hatsukade and a team of astronomers from the National Astronomical Observatory of Japan used ALMA to detect the radio emission from molecular gas in two dark LGRB hosts located 4.3 billion and 6.9 billion light-years away.
"We have been searching for molecular gas in GRB host galaxies for over ten years using various telescopes around the world. As a result of our hard work, we finally achieved a remarkable breakthrough using the power of ALMA," researcher Kotaro Kohno said in a statement.
Astronomers also discovered something about the composition of GRB host galaxies - they are clouded in a remarkable amount of dust compared to molecular gas, which was only found as its center.
"We didn't expect that GRBs would occur in such a dusty environment with a low ratio of molecular gas to dust. This indicates that the GRB occurred in an environment quite different from a typical star-forming region," Hatsukade added.
The findings will appear in the journal Nature on June 12.