The Einstein Probe Discovered Two Vampire Stars That Are Eating One Another, Which Is Highly Unusual
While astronomers were using the Einstein probe, they noticed a flash of powerful X-ray light coming from a nova explosion on a white dwarf star.
The flare was spotted on May 27, 2024, within a star system in the Small Magellanic Cloud (SMC), a satellite next to the Milky Way galaxy.
In January 2024, the Einstein probe was launched to study the high-energy universe. Among the probe’s instruments, there was its Wide-field X-ray Telescope (WXT), the only telescope in orbit that can detect the sources of lower-energy X-rays.
“We were chasing fleeting sources when we came across this new spot of X-ray light in the SMC,” said Alessia Marino of the Institute of Space Sciences in Spain.
“We realized that we were looking at something unusual, [something] that only Einstein Probe could catch.”
What they saw was an odd pairing of stars. One of them was a “Be” star, and it was particularly massive at around 12 times the mass of our sun. The other was a white dwarf star, which was about 20 percent more massive than our sun.
A sun-like star can survive for at least hundreds of millions of years, but a star of 12 solar masses should explode as a supernova after about 20 million years. It is unclear how a Be star and a white dwarf can be orbiting together since they are so far apart in age.
The most likely answer is that the Be star and white dwarf star are sharing material. They take turns feeding off each other like vampires.
The astronomers believe that the system initially contained two stars with masses six and eight times the mass of our sun. The larger star was the first to reach the end of its fuel supply.
Sign up for Chip Chick’s newsletter and get stories like this delivered to your inbox.
As its core struggled to keep the fusion reactions going, the energy produced in those reactions weakened, allowing gravity to make the outer layers around the core more compact. This caused pulsations in the outer layers, causing the star to expand into a giant.
At this stage, the smaller star was near enough so that its gravity began pulling material away from the giant star.
Over time, the smaller star gained mass, growing to 12 times the mass of our sun, while the once-larger star was stripped down to its dense core: a white dwarf about 1.23 times the mass of our sun.
Now, the white dwarf is stealing back material from the 12-solar-mass star. As the material falls back onto the white dwarf, the pressure and temperature at the white dwarf’s point of impact grows until the buildup triggers a localized thermonuclear explosion, resulting in a nova, a brilliant burst of light that includes X-rays.
“This study gives us new insights into a rarely observed phase of stellar evolution, which is the result of a complex exchange of material that must have happened among the two stars,” said Ashley Chrimes of the European Space Agency.
“It’s fascinating to see how an interacting pair of massive stars can produce such an intriguing outcome.”
The research was published in The Astrophysical Journal Letters.
More About:News
Read This Next
