Calm down, it’s only Science

cosmosscience:

In the late 1960′s, gamma-ray bursts were discovered. However, this was not an intentional discovery.  They were discovered by the U.S. Vela satellites that were actually built to detect gamma radiation pulses emitted by nuclear weapons tested in Space! Why? Well, the USA suspected that the USSR might attempt to conduct secret nuclear tests after signing the Nuclear Test Ban Treaty in 1963. However, that wasn’t the case.

On the second of July in 1967, the Vela 4 and Vela 3 satellites detected a flash of gamma radiation unlike any known nuclear weapons’ signature. The team at the Los Alamos Scientific Laboratory (led by Ray Klebesadel) were rather uncertain of what had happened. However, they didn’t consider the matter urgent and filed the data away for investigation.  As more Vela satellites were launched with better instruments, they continued to find these gamma-ray bursts in their data. They analyzed the different arrival times of the bursts as detected by different satellites and the team was able to determine rough estimates for the sky positions of sixteen bursts.

So what were these mysterious outbursts? Was America about to get bombed?

Well, America wasn’t about to get bombed, so that’s one less thing we have to read about in our history books! Instead, it was suggested that the gamma-ray bursts happened inside of the Milky Way Galaxy. This theory was found incorrect when in 1991, the Compton Gamma Ray Observatory, and its’ Burst and Transient Source Explorer instrument was launched. This instrument provided data that showed an absence of gamma-ray bursts in our galaxy and therefore, they had to be beyond our galaxy.

Alright, well, get to the point. Where are gamma-ray bursts?!

Gamma-ray bursts are flashes of gamma rays (electromagnetic radiation of high frequency)  that are associated with very energetic explosions that have been observed in distant galaxies. They are known to be the most radiating electromagnetic events in the Universe. The bursts can last from ten milliseconds to several minutes (a typical burst lasts 20-40 seconds). This is usually followed by an “afterglow” emitted at longer wavelengths such as X-ray, ultraviolet, optical, infrared, microwave and radio.

Picture above: An Artist’s illusion that shows the life of a massive star as nuclear fusion converts lighter elements into heavier ones. Sooner or later, the process comes to and end and the star will collapse and form a black hole. It is theoretically possible that a gamma-ray burst can be formed during the collapse.

There are two different types of Gamma-ray bursts, long and short:

Long gamma-ray bursts: Most of the gamma-ray bursts we have observed, have lasted for longer than two seconds and are then classified as long gamma-ray bursts. Long gamma-ray bursts tend to have the brightest afterglows and are studied in much greater detail than short gamma-ray bursts. From what we have observed, most long gamma-ray bursts are a result of a galaxy with rapid star formation, a core-collapse supernova and generally the deaths of massive stars.

In March 28 2011, there was a very unique gamma-ray burst (GRB 110328A), one that lasted more than two and half months! The event is interpreted as a supermassive black hole devouring a star (probably a white dwarf) and emitting its beam of radiation towards Earth.

Short gamma-ray bursts:

Gamma-ray bursts that have a duration of less than two seconds are classified as short gamma-ray bursts. There are not as many as these as long gamma-ray bursts, only 30 % of those we have observed. Many short gamma-ray burst afterglows have been detected and most of them have been found in regions of little (or non) star formation (such as large elliptical galaxies and the center regions of large galaxy clusters). There have been none that are associated with supernovae. It is believed that they originate from the mergers of binary neutron stars or a neutron star with a black hole.

Picture above: An Artist’s illusion of a gamma-ray burst. The energy from the explosion is shown as two oppositly-directed jets.

So there we have it, no nuclear tests, no blowing up the USA, just a wonderful and fascinating gamma-ray burst!

Sources:

http://astro.berkeley.edu/research/grbs/grbinfo.html

http://www.nasa.gov/mission_pages/swift/bursts/

Illustrated Science Magazine