Eddie Gonzales Jr. – MessageToEagle.com – As many as 21 neutron stars orbiting sun-like stars have already been discovered by astronomers led by Caltech’s Kareem El-Badry.
This illustration depicts a binary star system consisting of a dense neutron star and a normal sun-like star (upper left). Using data from the European Space Agency’s Gaia mission, astronomers found several systems like this one, in which the two bodies are widely separated. Because the bodies in these systems are far apart, with separations on average 300 times the size of a sun-like star, the neutron star is dormant—it is not actively stealing mass from its companion and is thus very faint. To find these hidden neutron stars, the scientists used Gaia observations to look for a wobble in the sun-like stars caused by a tugging action of the orbiting neutron stars. These are the first neutron stars discovered purely due to their gravitational effects. Credit: Caltech/R. Hurt (IPAC)
Neutron stars, dense remnants of exploded massive stars, are typically too faint to detect directly. However, their gravitational pull causes their companion stars to wobble, which Gaia mission detected.
“Gaia’s continuous sky scanning and measurement of over a billion stars’ wobbles increases the chances of discovering rare objects,” El-Badry, an astronomy professor at Caltech and scientist at the Max Planck Institute or Astronomy in Germany, said in a press release.
Ground-based telescopes in Hawai’i, Chile, and Arizona supplemented Gaia providing more information about the hidden neutron stars.
Neutron stars have been found orbiting sun-like stars in compact systems, where their proximity allows mass transfer, causing them to emit X-rays or radio waves.
The newly discovered neutron stars, however, orbit at greater distances—one to three times the Earth-Sun distance—from their companion stars.
The newly discovered stellar remnants are too distant from companion stars to absorb their material, remaining inactive and invisible. “These are the first neutron stars found solely through gravitational effects,” states El-Badry.
The discovery is surprising, as it’s unclear how an exploded star ended up near a sun-like star.
The neutron star’s progenitor likely expanded and interacted with its solar-type companion during its late stages. This interaction may have temporarily engulfed the smaller star. The progenitor’s subsequent supernova explosion should have separated the binary system, propelling the neutron star and sun-like star in opposite directions.
The researcher said that the discovery of these new systems shows that some binaries survive cataclysmic processes, though models can’t yet fully explain how.”
Gaia detected these unusual companions due to their wide orbits and long periods, with the sun-like stars orbiting the neutron stars every six months to three years.
El-Badry explains that Gaia is better at detecting wider orbits and nearby binary systems. Most new discoveries are within 3, 000 light-years of Earth, a small distance compared to the Milky Way’s 100, 000 light-year diameter.
“If the bodies are too close, the wobble will be too small to detect,” El-Badry says. “With Gaia, we are more sensitive to the wider orbits.”
Most of the newly discovered systems are located within 3,000 light-years of Earth—a relatively small distance compared, for example, to the 100,000 light-year-diameter of the Milky Way galaxy.
Probably, one in a million solar-type stars orbits a neutron star in a wide orbit.
El-Badry also seeks dormant black holes orbiting sun-like stars. Using Gaia data, he discovered two quiet black holes in our galaxy, including Gaia BH1, the closest known black hole to Earth at 1, 600 light-years away.
Written by Eddie Gonzales Jr. – MessageToEagle.com Staff Writer