WASHINGTON, June 30 – At their death, about 97 percent of all stars turn into star zombies called white dwarfs, one of the most dense objects in space. The newly discovered white dwarf is recognized as one of the most “extreme” of these, and has stuck a horrible amount of mass into a surprisingly small collection.
Scientists say that this white dwarf, which is very magnetic and rotates fast on Wednesday, is 35 percent larger than our sun, but has a smaller diameter that is slightly larger than Earth’s moon. This means that due to its enormous density, it has the largest mass and, conversely, the smallest size among any known white dwarf.
Only two types of objects – black holes and neutron stars – are relatively compact in white dwarfs.
The birth of this white dwarf called ZTF J1901 + 1458 is also unusual. Apparently, these two stars are the product of a binary star system orbiting each other. These two stars became separate at the end of their life cycles, evolving into dwarf dwarfs, and then merged into a single whole, spiraling toward each other.
Even if it were a mass combined with Smidgen, the merger would have led to a giant star explosion called a supernova, said Ilaria Kayazzo, a leading author of the study published in the journal Nature, Caltech astrophysicist. In the future, it could still explode, Kayazzo added.
“This white dwarf is really extreme,” Caiazzo said. “We found an object that could really be as small and heavy as a white dwarf.”
It is relatively close to our Milky Way galaxy, about 130 light-years from Earth. The light year – that’s the distance covered in a year – is about 5.9 trillion miles (9.5 trillion km).
The white dwarf is actually slowly shrinking and becoming increasingly dense. If it doesn’t explode, it could cause the nucleus to collapse, turning it into a neutron star, another type of city-sized stellar remnant that usually forms after very large stars hit a supernova. This will be a previously unrecognized way of neutron star formation.
The white dwarf was seen by astrophysicist and research co-author Kevin Burge of Keltech’s Palomar Observatory.
“The white dwarf is the most common form of stellar remnant,” said Burdge, who worked at Keltech and made his way to MIT. “So it’s great to see the most extreme advantages among them.”
Its diameter is about 2670 miles (4300 km) – the distance from Boston to Los Angeles or London to Tehran – the diameter of the Moon is slightly more than about 2160 miles (3475 km).
While our sun revolves around its own axis once every 27 days, this white dwarf does it every seven minutes. Its magnetic field is about a billion times stronger than Earth’s.
Stars that are eight times the mass of the Sun are thought to eventually become white dwarfs. Such stars eventually burn all the hydrogen they use as fuel through nuclear fusion. Gravity at this point causes them to collapse and explode their outer layers in a “red giant” phase, leaving a dense core that is a white dwarf.
The white dwarf initially has a high temperature, but gradually cools over time, there is no new source of energy. In about 5 billion years, our sun will turn into a red giant and then a white dwarf.