The mysterious death of some stars

As a song of farewell to the universe, most of the big stars explode, turning into a super-giant fireball and releasing a lot of energy when they die. But astronomers discovered a strange type of stars: they silently disappeared in the cosmic night.

This discovery can reveal to us a new way of living in the universe.

Until now, scientists thought stars were far apart from the universe in two ways. When it swells up to eight times the size of our Sun and runs out of fuel (hydrogen and helium gas), the layers of matter outside the star split away, leaving a smoldering core - called a white dwarf. .

The deaths of stars larger than 8 times the Sun seem much more dire and noisy. When the fuel runs out, its core crumbles, creating tremendous explosions (called supernova) in space, releasing many giant dust into the universe. After the explosion, what remains at the star's position is a neutron star or black hole.

Super large supernova explosion (Photo: pbs.org)

Recent observations show that many of these large explosions release massive, gamma-ray beams, including many that exist for more than 2 seconds in space.

Last June, the Swift telescope from the US Aerospace Agency (NASA) discovered a large gamma beam emitted from a white dwarf star in the constellation Indus - 1.6 billion light years from Earth. shining. This gamma beam, called GRB 060614, lasts 102 seconds. Astronomers quickly turned the ground telescopes toward GRB 060614, hoping to see a big explosion.

But nothing happened

That silence made the astronomers confused. " It's like you didn't hear any thunder coming from a nearby storm even though you saw a long lightning bolt ," said Johan Fynbo, an expert at the Niels Bohr Astronomical Research Institute at the University of Copenhagen ( Denmark), speak.

Scientists believe that some giant stars may have perished without going through an explosion, only releasing a gamma beam before turning into a black hole. In this case, all the matter on the star is swallowed by the black hole.

Another possibility is: gamma beams are created by a combination of two objects of the same type. For example, the collision between two neutron stars or between a neutron star and a black hole also produces gamma beams.

But the explanation is inconsistent with the reality, because the gamma rays' lifetime is often very short - usually less than 2 seconds and their energy is not large.

"Some mysterious process involved in the destruction of super-massive stars. Collisions between two neutron stars or a giant star explosion can release gamma rays, but certainly that gamma rays cannot escape the attraction of the black hole, so our telescope found them to be unusual, " Massimo Della Valle, scientist at the Observatory Text Arcetri, Firenze, Italy, speak.

Viet Linh