Astronomers discover a record-breaking star as small as the moon, but with more mass than the sun


(CBS News) – Astronomers have discovered the smallest, yet most massive white dwarf Star ever seen.

According to a new study published on Thursday in the Nature magazine, the “very special” star has a mass that is greater than that of our sun, and all of this in a relatively small body, similar to our moon. It emerged when two less massive white dwarfs, who circled their lives as a couple, collided and merged.

At the end of their life, most stars become white dwarfs, which are essentially glowing corpses and are also one of the densest objects in the universe Black holes and neutron stars. In about 5 billion years, our sun will become a red giant before it ultimately suffers the same fate.

“It may seem counter-intuitive, but smaller white dwarfs are more massive,” said lead author Ilaria Caiazzo in a statement. “That’s because white dwarfs lack the nuclear burn that normal stars maintain against their own gravity, and their size is instead regulated by quantum mechanics.”

The highly magnetized dead star named ZTF J1901 + 1458 is relatively close to Earth, only about 130 million light years away. It was discovered by the Zwicky Transient Facility (ZTF) of Caltech’s Palomar Observatory.

When the two white dwarfs merged, they combined to form a new star about 1.35 times the mass of our Sun, the most massive of its kind ever found. If one of the stars had just a little more mass, the merging would have resulted in an intense explosion called a. guided Supernova.

ZTF J1901 + 1458 also has an “extreme” magnetic field nearly 1 billion times stronger than the sun, which spins quickly to complete a full revolution in just seven minutes. The sun needs about 27 days to make one revolution.

At 2,670 miles in diameter, it is the smallest known white dwarf in the universe at over 400 miles. By comparison, the moon is 2,174 miles in diameter.

“We caught this very interesting object that wasn’t massive enough to explode,” says Caiazzo. “We’re really investigating how massive a white dwarf can be.”

So what’s next for the rare star?

Researchers believe the star has enough mass to potentially evolve into into Neutron star, which usually arises when a star with a mass much larger than the sun explodes in a supernova. If your hypothesis is correct, it means that many of the neutron stars in the universe could have formed in this previously unknown way.

“It’s so massive and dense that in its core, electrons are captured by protons in nuclei to form neutrons,” said Caiazzo. “Since the pressure of the electrons works against gravity and keeps the star intact, the nucleus collapses when a sufficiently large number of electrons are removed.”

The star’s proximity to Earth and its young age – only around 100 million years old or less – mean that similar stellar phenomena can be more common in our own galaxy.

“Up to now, nobody has been able to systematically research astronomical phenomena on a short time scale on this scale. The results of these efforts are overwhelming, ”said Kevin Burdge, who first spotted the star in all-sky images.

But researchers say they are just getting started.

“There are so many questions to answer, such as the rate of white dwarf mergers in the galaxy, and is that enough to explain the number of Type Ia supernovae?” Said Caiazzo. “How is a magnetic field generated during these powerful events, and why is there such a variety of magnetic field strengths in white dwarfs? Finding a large population of merger white dwarfs will help us answer all of these questions and more. “

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