Astronomers discover what may be 21 neutron stars orbiting sun-like stars

Most stars in the universe are in pairs. While the Sun exists alone, many stars like the Sun orbit similar stars. There are also rare pairs between stars and cosmic spheres dotted throughout the universe. For example, black holes often orbit each other. One pair that has proven to be extremely rare is between a Sun-like star and a type of dead star called a neutron star.

Now, astronomers led by Kareem El Badry of the California Institute of Technology have discovered 21 neutron stars orbiting Sun-like stars. Neutron stars are the burnt-out, dense cores of massive stars that have exploded. By themselves, they are very dim and usually cannot be detected directly. But as a neutron star orbits a Sun-like star, it tugs on its companion star, causing the star to move back and forth in the sky. Using the European Space Agency’s Gaia mission, the astronomers were able to capture these characteristic wobbles and reveal a new population of dark neutron stars.

“Gaia is continuously scanning the sky and measuring the wobble of more than a billion stars, so there’s a good chance it will discover even the most unusual objects,” said El Badry, an assistant professor of astronomy at the California Institute of Technology and an adjunct scientist at the Max Planck Institute for Astronomy in Germany.

The new study includes a team of co-authors from around the world. Published in Open Journal of AstrophysicsSome data Ground TelescopeTo follow up on Gaia’s observations and learn more about the mass and orbit of the hidden neutron star, observatories such as W. M. Keck Observatory on Mauna Kea in Hawaii, La Silla Observatory in Chile, and Whipple Observatory in Arizona were used.

Neutron stars have been found orbiting Sun-like stars before, but all those systems were much more compact. The close distance between the two objects allows the neutron star (which is more massive than a Sun-like star) to steal mass from its partner. This mass-transfer process makes the neutron star shine brightly at X-ray and radio wavelengths. In contrast, the neutron star in the new study is much farther away from its partner, on the order of one to three times the distance between Earth and the Sun.

That means the newly discovered stellar remnants are too far away to have any material to steal from. Instead, they’re motionless and dim. “These are the first neutron stars to be discovered purely through gravitational influences,” El Badry says.

The discovery is somewhat surprising because it’s not clear how an exploded star could end up next to a star like the Sun.

“We don’t yet have a complete model for how these binaries form,” El Badry explains. “In principle, the progenitor star would have grown massive and interacted with a Sun-like star at a final stage in its evolution. The massive star would likely have shaken the smaller star and briefly engulfed it. The progenitor star would then explode in a supernova, which, according to the model, would have unbound the binary system and sent the neutron star and the Sun-like star flying off in opposite directions.

“The discovery of these new systems indicates that at least some binary systems survive these cataclysmic processes, even though models cannot yet fully explain how they work,” he says.

Gaia was able to find the unlikely companion star because of its wide orbit and long period (the orbit of a sun-like star around the sun). Neutron Star The duration ranges from 6 months to 3 years.

“If an object is too close, the wobble is too small to detect,” El Badry says. “With Gaia, we’re more sensitive to wider orbits.” Gaia is also most sensitive to relatively nearby binary systems. Most of the newly discovered systems are within 3,000 light-years of Earth, a relatively small distance compared to, say, the Milky Way’s 100,000 light-year diameter.

The new observations suggest just how rare this combination is: “We estimate that about one in a million solar-like stars orbits a neutron star in a wide orbit,” he notes.

El Badri is also interested in discovering what lies hidden within the invisible. Black Hole in Orbit Black holes with stars like the Sun. Using Gaia data, he discovered two quiet black holes hidden in the Milky Way. One is called Gaia BH1, The closest known black hole to Earth It is located 1,600 light years away.

“We don’t know for sure how these black hole binaries formed,” El Badry said. “Our models for binary evolution are clearly flawed. Discovering more of these dark companions and comparing their population statistics with the predictions of different models will help us shed light on how they formed.”