Astronomers have found a monstrous neutron star that lived less than a second

(ORDO NEWS) — The variety of physical processes that take place in the Universe never ceases to amaze.

It is worth getting used to how unimaginably long some cosmic events take, how scientists find those that last only a fraction of a second.

Astronomers recently discovered strange pauses in the emission from two pairs of colliding neutron stars in archived data.

It is known that for luminaries of a sufficiently large mass, this collision leads to the appearance of a black hole at the site of a “cosmic accident”.

However, it turned out that during pauses that lasted from 10 to 300 milliseconds, superheavy neutron stars managed to form from two merging stars.

And only then did they turn into a black hole: the collapse of an already very dense substance under the influence of gravity leads to the appearance of a black hole.

In order for neutron stars not to die immediately (not be reborn into a black hole), they had to rotate dizzyingly fast. That was the only way they could delay the inevitable.

Let us explain that stars of large mass end their lives with a supernova explosion. After that, a very dense core, known as a neutron star, remains in place of the luminary.

These strange stars contain a mass of more than one and a half masses of the Sun, and at the same time they themselves can be a couple of tens of kilometers in diameter.

At the same time, neutron stars (like all other luminaries of the Universe) often exist in the form of binary systems – that is, two stars that are connected by gravity and revolve around a common center of mass.

Gradually, over the course of millions of years, these luminaries approach each other, rotating in a huge spiral. Eventually they collide to form one new object.

What kind of object it is depends on the total mass of the two stars. For example, a neutron star of maximum mass (more than three solar masses) will shrink under the influence of its own gravity and form a black hole.

If the sum of the masses of two colliding neutron stars is below this limit, they form a new neutron star. And if their total mass is greater, the collision will give rise to a black hole.

Astronomers know all this, but until now the exact sequence of events has not been clear.

The researchers realized that they were missing some intermediate stage in the emergence of a black hole at the site of two merged neutron stars.

Therefore, they somewhat changed the approach to the search for superheavy neutron stars. And then they analyzed the archival data on the collisions of such luminaries.

Let us explain that the birth of a black hole is accompanied by a surge of gravitational waves – a kind of “earthquake” of the space-time canvas.

And if a superheavy neutron star manages to form in the process of the appearance of a black hole, a pattern known as quasi-periodic oscillations should appear in gravitational waves.

Current observatories are not sensitive enough to detect these quasi-periodic fluctuations in gravitational waves, write the authors of the new study. But they determined that the “signatures” of such oscillations must also appear in gamma rays.

Since short gamma-ray bursts are also generated during the collision of neutron stars, the researchers found the necessary data set for study very quickly.

To test their assumptions, astronomers looked at archived data on 700 short gamma-ray bursts collected over the past few decades.

So quasi-periodic fluctuations were detected in two events at once – one was recorded in July 1991, and the other in November 1993.

The team calculated that the resulting superheavy neutron stars could have a mass of more than 2.5 times that of the Sun and last no more than 300 milliseconds before collapsing into black holes.

They also rotated very quickly – at a speed of almost 78 thousand revolutions per minute. But they lived tens of thousands of times less than a minute.

By comparison, the fastest pulsar, a neutron star that also spins at a tremendous speed, spins at less than 43,000 revolutions per minute.

Scientists write that in the future, gravitational wave detectors should become sensitive enough to directly find the “signatures” of superheavy neutron stars in the ripples of space-time – gravitational waves.


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