The members of the LP 413-53AB system are so close that it takes just 17 hours to revolve around each other.
An artist’s rendering of two brown dwarfs. Image credit: Roberto Molar Candanosa & Sergio Dieterich, Carnegie Institution for Science.
Previously, astronomers had only detected three short-period ultracool dwarf binary systems, all of which are relatively young — up to 40 million years old.
LP 413-53AB, also known as 2MASS J03505737+1818069, is estimated to be billions of years old, but has an orbital period that is at least 3 times shorter than the all ultracool dwarf binaries discovered so far.
“It’s exciting to discover such an extreme system,” said Dr. Chih-Chun ‘Dino’ Hsu, an astrophysicist with the Center for Interdisciplinary Exploration and Research in Astrophysics at Northwestern University and the Center for Astrophysics and Space Science at the University of California, San Diego.
“In principle, we knew these systems should exist, but no such systems had been identified yet.”
Dr. Hsu and colleagues first discovered LP 413-53AB, which is located 120 light-year away in the constellation of Taurus, while exploring archival data.
They then obtained high-resolution near-infrared spectra of the binary system using the Near-InfraRed SPECtrometer (NIRSPEC) on the Keck II telescope at the W.M. Keck Observatory.
“When we were making this measurement, we could see things changing over a couple of minutes of observation,” said Professor Adam Burgasser, an astronomer at the Center for Astrophysics and Space Science at the University of California, San Diego.
“Most binaries we follow have orbit periods of years. So, you get a measurement every few months. Then, after a while, you can piece together the puzzle.”
“With this system, we could see the spectral lines moving apart in real time. It’s amazing to see something happen in the universe on a human time scale.”
The observations show that the distance between the two stars is about 1% of the distance between the Earth and the Sun.
“This is remarkable, because when they were young, something like 1 million years old, these stars would have been on top of each other,” Professor Burgasser said.
The team speculates that the stars either migrated toward each other as they evolved, or they could have come together after the ejection of a third — now lost — stellar member.
By studying similar star systems, astronomers can learn more about potentially habitable exoplanets.
Ultracool dwarfs are much fainter and dimmer than the Sun, so any worlds with liquid water on their surfaces would need to be much closer to the star.
However, for LP 413-53AB, the habitable zone distance happens to be the same as the stellar orbit, making it impossible to form habitable planets in this system.
“These ultracool dwarfs are neighbors of our Sun,” Dr. Hsu said.
“To identify potentially habitable hosts, it’s helpful to start with our nearby neighbors.”
“But if close binaries are common among ultracool dwarfs, there may be few habitable worlds to be found.”
The findings were published in the Astrophysical Journal Letters.
Chih-Chun Hsu et al. 2023. Discovery of the Exceptionally Short Period Ultracool Dwarf Binary LP 413-53AB. ApJL 945, L6; doi: 10.3847/2041-8213/acba8c
Source : Breaking Science News