Astronomers have discovered a strange star system containing two ultra-cold dwarfs. Two ultracold dwarfs are so close that they orbit each other within a day. Oh, they are invisible to the human eye.
Ultracold dwarfs, as their name suggests, are relatively cold stars with temperatures below 2,430 °C (4,400 °F). This means they emit most of their light in the infrared.
The system in question, called LP 413-53AB, has been known to astronomers for decades, but was always thought to be a single star. But that changed recently when Chih-Chun Hsu, an astrophysicist at Northwestern University, took a closer look at it. Using an algorithm of his own design, he modeled the stars from his spectral data and found that the spectral lines shifted in opposite directions and eventually separated into pairs. This actually showed him that the two stars were incredibly close.
To see for themselves, Sue and his team used the Keck Observatory in Hawaii to study the system. And sure enough, the team could see the system change very quickly in his series of observations from March 2022 to his January 2023.
“When we were doing this measurement, we could see things change in just a few minutes of observation,” said study co-author Professor Adam Burgasser. “Most of the binary stars we track have orbital periods that span many years, so we get measurements every few months. After a while, we can put the puzzle together. With this system, we were able to see the spectral lines moving apart in real time.It’s amazing to see something happening in space on a human timescale.”
These observations showed that LP 413-53AB consists of a pair of ultracold dwarfs separated by only 1% of the distance between Earth and the Sun. That means they orbit each other in just 17 hours, the tightest orbit ever found for a binary star of this kind, and one of the tightest orbits known. .
Astronomers believe that these stars may have naturally moved toward each other over time, or they may have had a third companion star that was ejected first, bringing the remaining two closer together. It suggests that there is a
Proximity isn’t the only record broken by this system. The star is also the oldest known star. Most ultracold dwarfs are “only” around 40 million years old, but these are estimated to be billions of years old, which is comparable in age to our Sun.
The team plans to use this technique to investigate other ultracold dwarfs and reveal other currently unknown binary star systems.
This research Astrophysics Journal Letter.
Source: Northwestern University
