Silent explosion happens in the universe

A group of European astronomers provided information that recent supernovae are not as normal as we thought. Instead, the star is said to have exploded and fell into a black hole, creating a weak ray, often seen in intense events, called a gamma-ray explosion.

The object, SN 2008D, may be one of the weakest explosions to produce extremely fast moving rays.This discovery is an important event for understanding the most intense phenomenon observed in the universe.

These impressive results, in part based on observations with ESO's Large Telescope, were published in Science Express, the online version of Science.

Stars about 8 times the size of the sun end their short life with a massive explosion that illuminates the universe. The result of such explosions is the formation of dense objects such as neutron stars and black holes. When it explodes, some of the biggest stars emit 'tragic cries', in the form of huge energy rays like X-rays or gamma rays.

In the afternoon (in Europe) on January 9, 2008, the NASA / STFC / ASI Swift telescope accidentally discovered the sudden occurrence of five-minute X-rays that originated from the galaxy. spiral NGC 2770, located 90 million light-years away in the direction of the constellation Lynx. The Swift satellite is investigating another supernova explosion that occurred last year in this galaxy, and X-rays appear in another location, and are then identified as coming from a supernova named is SN 2008D.

Researchers from the Italian National Institute of Astrophysics (INAF), Max-Planck Astrophysics Institute (MPA), and many other offices have observed supernova for a long time. The research team is led by Paoplo Mazzali of INAF's Padova Observatory. Mazzali said: 'What makes this event particularly interesting is the very weak and' soft 'X-ray signal (1), completely different from Gama rays and looks like a normal supernova explosion' .

Spiral galaxy NGC 2770 and two supernovae are observed by Asiago Observatory.The photo taken on January 12, 2008 shows that the star SN 2007uy faded away and SN 2008D was discovered.(Photo: ESO)

After the supernova was discovered, the team quickly observed it from the Asiago observatory in Northern Italy and determined that it was supernova type Ic. Mazzali explains: 'This is a supernova created from a star that has depleted hydrogen and lost its helium-rich outer layer before exploding; it is the only type of supernova that has the appearance of Gama rays (for a long time). This object is therefore particularly interesting '.

Not long ago, a group of independent astronomers published in Nature that SN 2008D is a normal supernova. X-rays were discovered because this was the first time astronomers were lucky enough to catch a star exploding . Mazzali and colleagues have the opposite idea: 'Our observation and modeling methods show that this is an unusual event, which needs to be better understood in terms of objects located in the middle boundary. Normal supernova and a Gama ray burst '.

The team set up a monitoring campaign to control the development of supernovae, using both ESO telescopes and national telescopes to collect large amounts of data. Supernova activity indicates that it is a high energy phenomenon, though not as strong as a gamma ray explosion. However, after a few days the spectrum of the supernova began to change. Specifically, Helium lines appear, indicating that the original star is not as deeply ingrained as Gama ray bursts.

For years, Mazzali and his team have developed theoretical models to analyze the properties of supernovae. When applied to SN2008D, their models showed that the original star was 30 times more massive than the Sun, but at the time of the explosion, it shrank and was only 8-10 times larger than the sun . The result of the collapse of such a large star is a black hole.

Massimo Della Valle, co-author, said: 'Because of the size and energy associated with any known Gama-ray burst, we think that the collapse of this star creates a weak ray. , and in the presence of helium, it is difficult to keep the alignment for this beam. So when it appears from the surface of the star, the signal is very weak. '

Co-author Stefano Valenti added: 'Our hypothesis leads to the conclusion that Gama ray activity is like an explosion that exists in all supernovae that form a black hole'.

Guido Chincarini, co-author and chief investigator of Italian research on gamma-ray bursts, explains: 'With Gama and X-ray devices becoming increasingly advanced, we gradually discover properties. variety of stellar explosions. Gama ray explosion is the most easily discovered phenomenon. We realize that there are many changes on the same topic that connect these special events with more normal phenomena. '

However, these are important discoveries in completing the overall picture of how big stars end their lifetimes, creating dense objects, as well as introducing chemical elements. New to the cosmic gas to create new stars.

(1) Astronomers classify X-rays as "soft" when the amount of high-energy X-rays is less than the number of low-energy X-rays.

Refer

1. Paolo Mazzali et al.The metamorphosis of Supernova SN 2008D / XRF 080109: a link between Supernovae and GRBs / Hypernovae.Science, 24 July 2008