Tiny, fast-spinning white dwarf is the most massive ever discovered

By Georgina Torbet July 4, 2021

The white dwarf ZTF J1901+1458 is about 2,670 miles across, while the moon is 2,174 miles across. It is depicted above the Moon in this artistic representation. — The white dwarf ZTF J1901+1458 is about 2,670 miles across, while the moon is 2,174 miles across. The white dwarf is depicted above the Moon in this artistic representation; in reality, the white dwarf lies 130 light-years away in the constellation of Aquila. Giuseppe Parisi

When our sun finally runs out of fuel and nears the end of its life, it will puff up to become a red giant before it throws off its outer layers and shrinks down to become a white dwarf. This is the eventual fate of the vast majority of stars in the universe, which will come to an evolutionary end as white dwarfs.

Now, researchers from the W. M. Keck Observatory have found an unusual white dwarf which is both the smallest and the most massive ever observed. It is named J1901+1458 and is located relatively nearby, at 130 light-years from Earth.

This remarkable object is “packing a mass greater than that of our sun into a body about the size of our moon,” said lead author Ilaria Caiazzo of Caltech. “It may seem counterintuitive, but smaller white dwarfs happen to be more massive. This is due to the fact that white dwarfs lack the nuclear burning that keep up normal stars against their own self gravity, and their size is instead regulated by quantum mechanics.”

The researchers believe this particular white dwarf became so massive because it was once part of a pair of white dwarfs orbiting each other. These two stars eventually crashed together and merged into one heavier star. This process also increases the magnetic field around the star, which makes it spin faster. This white dwarf spins at a head-turning rate, completing a rotation every seven minutes.

Due to its mass, this white dwarf might evolve further into a neutron star, which is almost as dense as a black hole and usually forms from a supernova explosion.

“This is highly speculative, but it’s possible that the white dwarf is massive enough to further collapse into a neutron star,” said Caiazzo. “It is so massive and dense that, in its core, electrons are being captured by protons in nuclei to form neutrons. Because the pressure from electrons pushes against the force of gravity, keeping the star intact, the core collapses when a large enough number of electrons are removed.”

“We caught this very interesting object that wasn’t quite massive enough to explode,” said Caiazzo. “We are truly probing how massive a white dwarf can be.”

Topics

Georgina Torbet

Space Writer

Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…

Space

Astronomers spot the shiniest exoplanet ever discovered

An artist impression of exoplanet LTT9779b orbiting its host star.

When you look up at the night sky you see mostly stars, not planets -- and that's simply because planets are so much smaller and dimmer than stars. But you can see planets in our solar system, like Venus, which is one of the brightest objects in the night sky. Due to its thick, dense atmosphere, Venus reflects 75% of the sun's light, making it shine brightly. Recently, though, astronomers discovered a planet that reflects even more of its star's light, making it the shiniest exoplanet ever found.

Exoplanet LTT9779 b reflects 80% of the light from its star, which it orbits very close to. That makes it extremely hot, and researchers believe that the planet is covered in clouds of silicate and liquid metal, which is what makes it so reflective.

Space

James Webb spots the most distant active supermassive black hole ever discovered

Crop of Webb's CEERS Survey image.

As well as observing specific objects like distant galaxies and planets here in our solar system, the James Webb Space Telescope is also being used to perform wide-scale surveys of parts of the sky. These surveys observe large chunks of the sky to identify important targets like very distant, very early galaxies, as well as observe intriguing objects like black holes. And one such survey has recently identified the most distant active supermassive black hole seen so far.

While a typical black hole might have a mass up to around 10 times that of the sun, supermassive black holes are much more massive, with a mass that can be millions or even billions of times the mass of the sun. These monsters are found at the heart of galaxies and are thought to play important roles in the formation and merging of galaxies.

Space

Amateur astronomer spots dwarf galaxy that computers missed

Right in the middle of this image taken with the NASA/ESA Hubble Space Telescope, nestled among a smattering of distant stars and even more distant galaxies, lies the newly discovered dwarf galaxy known as Donatiello II. If you can’t quite discern Donatiello II’s clump of faint stars in this image, then you are in good company. Donatiello II is one of three newly discovered galaxies. All three were missed by an algorithm designed to search astronomical data for potential galaxy candidates. Even the best algorithms have their limitations when it comes to distinguishing very faint galaxies from individual stars and background noise. In such challenging situations, identification must be done the old-fashioned way – by a dedicated human trawling through the data themselves.

As machine learning approaches get more and more sophisticated, they are increasingly used in astronomy for difficult tasks like spotting dim and distant galaxy clusters. It can be tremendously helpful to have computers search through astronomical data to look for particular objects as they can process a huge amount of data -- however, there are some judgments that still require the human touch.

This week's image from the Hubble Space Telescope shows an object that was spotted by a human even after it had been missed by a computer algorithm. The dwarf galaxy Donatiello II is very faint and hard to pick out from the background behind it, but an amateur astronomer was able to point it out.