In the past few days it has been smallest but most massive white dwarf star ever seen from a group of astronomers coming from California Institute of Technology of Pasadena (CA, USA), from University of British Columbia of Vancouver (British Columbia, Canada), from University of California of Santa Cruz (CA, USA) and by University of Washington of Seattle (WA, USA).
According to the new study published on Thursday in the Nature magazine, the “very special” star has a mass greater than that of our sun, all enclosed in a body relatively small, of similar in size to our moon.
The smallest white dwarf ever found to date was formed when two less massive white dwarfs, which have spent their lives in pairs orbiting each other, collided and merged together.
But how is a white dwarf created? Essentially, at the end of their life, the vast majority of stars become so, these are in fact “smoking corpses” and, in about 5 billion years, our sun will also become a red giant before suffering the same fate.
But why is the discovery of this smaller white dwarf so important? In addition to being one of the densest objects in the universe – together with black holes and neutron stars -, they also allow us to estimate how the universe “evolves” and what we can find there.
“It may seem counterintuitive, but a smaller white dwarf is more massive. This is due to the fact that white dwarfs do not have the nuclear combustion that keeps normal stars against their own gravity, and their size is instead regulated by quantum mechanics. “
he said in a note the main author Ilaria Caiazzo.
The discovery of the smallest white dwarf
The smallest white dwarf that we know of is highly magnetized and has been named ZTF J1901 + 1458; the dead star is relatively close to the Earth, only 130 million light years away and came discovered by the Zwicky Transient Facility (ZTF) ofCaltech Palomar Observatory.
When the two white dwarfs merged, they joined to form a new star, approx 1.35 times the mass of our sun resulting, in addition to being the smallest white dwarf, also the most massive ever found of its kind.
If one of the stars had a slightly larger mass, the merger would have resulted in an intense explosion called a supernova.
ZTF J1901 + 1458 also has a magnetic field Almost “extreme” 1 billion times stronger than the sun, which quickly rotates to complete a complete tour in just seven minutes which, when compared with the sun, makes an impression, the latter in fact takes about 27 days to complete a rotation.
With a diameter of 2,670 miles, it is the smallest known white dwarf in the universe and if you think that, in comparison, the moon is 2,174 miles in diameter, well I leave the rest to you.
“We captured this very interesting object that wasn’t massive enough to explode. We are really probing how massive a white dwarf can be ”.
What future awaits the smallest white dwarf?
Researchers believe the star has a mass large enough to evolve into a neutron star, which usually forms when a star with a mass much larger than the sun explodes in a supernova.
If their hypothesis were to be correct, it means that many of the neutron stars in the universe may have formed in this previously unknown way.
“It is so massive and dense that, in its nucleus, electrons are captured by the protons in the nuclei to form neutrons. Since the pressure of the electrons pushes against the force of gravity, keeping the star intact, the nucleus collapses when enough electrons are removed ”.
The star’s proximity to Earth and its young age – only about 100 million years or less – mean that similar stellar phenomena can more commonly occur in our galaxy.
“So far, no one has been able to systematically explore short-term astronomical phenomena on this type of scale. THE results of these efforts are surprising“
he said Kevin Burdge, who first identified the star in images of the whole sky.
Despite this, the researchers say their work has only just begun:
“There are so many questions to be addressed, such as what is the merger rate of white dwarfs in the galaxy, and is that enough to explain the number of Type Ia supernovae?
How is a magnetic field generated in these powerful events and why is there such diversity in magnetic field strength among white dwarfs? Finding a large population of merged white dwarfs will help us answer all of these questions and more. “
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