These binary stars are so close together that their year is only 20.5 hours long

(ORDO NEWS) — A team of astrophysicists has discovered a double pair of ultracold dwarfs so close together they look like a single star.

They are remarkable in that it takes them only 20.5 hours to orbit each other. this means that their year is less than one Earth day. In addition, they are much older than similar systems.

We cannot see ultracool dwarf stars with the naked eye, but they are the most abundant stars in the galaxy. They have such a low mass that they only emit infrared light, and we need infrared telescopes to see them.

These are interesting objects because theory shows that stars must exist so close together, but this system is the first time astronomers have observed this extreme closeness.

A group of astronomers presented their findings at the 241st meeting of the American Astronomical Society in Seattle. Zhi-Chun “Dino” Xu, an astrophysicist at Northwestern University, led the study. The system was named LP 413-53AB.

“It’s very exciting to discover such an extreme system,” said Zhi-Chun “Dino” Xu, a Northwestern astrophysicist who led the study. “In principle, we knew that these systems must exist, but such systems have not yet been identified.”

The extremes of nature play an important role in calibrating our theoretical models, and this is true for low-mass binaries. Prior to this discovery, astronomers only knew of three short-period supercold binaries.

The research team found this pair in archival data. They combed through the data with an algorithm Xu wrote that models stars based on their spectral data.

But in these earlier images, the stars just happened to be aligned, so they looked like a single star. The odds are high for a tight double pair like this one.

But Hsu and his colleagues thought the data was strange, so they looked at the star more closely using the Keck Observatory. Observations have shown that the light curve changes so rapidly that there must be two stars.

They eventually realized that they had found the closest double pair ever found.

“When we were doing this measurement, we could see how things change within minutes of observation,” said Professor Adam Burgasser of the University of California, San Diego. Burgasser was Hsu’s adviser while Hsu was a graduate student.

“Most of the binary systems that we follow have an orbital period of several years. So you get measurements every few months.

Then, after a while, you can piece together the data. puzzle. With this system, we could see how the spectral lines diverge in real time. It’s amazing to see something happening in the universe on the scale of human time.”

To emphasize how close the stars are to each other, Xu compared them to our solar system and another known system.

This pair is closer together than Jupiter and one of its Galilean moons, Callisto. In addition, it is closer than the red dwarf TRAPPIST-1 to its nearest planet TRAPPIST-1b.

These stars are much older than three other similar systems known to astronomers. While these three are relatively young, around 40 million years old, LP 413-53AB is several billion years old, just like our Sun.

Their age is a clue that the stars did not originate during this period. close to each other. The researchers think they could have started with an even tighter orbit.

“This is remarkable because when they were young, they were about 1 million years old, these stars were stacked on top of each other,” Burgasser said.

Or the stars could start out as a pair in wider orbits and then move closer together over time.

Another possibility is that the stars began as a triple star system. Gravitational interactions could simultaneously eject one star and pull the remaining two into a narrower orbit.

More observations of the unique system may help answer this question.

Astronomers are interested in stars like this because of what they can tell us about habitable worlds. Because ultracold dwarfs are so dim and cold, their habitable zones are cramped regions.

This is the only way they could heat the planets enough to support liquid surface water. But in the case of LP 413-53AB, the habitable zone distance is the same as the stellar orbit, eliminating the possibility of habitable exoplanets.

“These ultracold dwarfs are neighbors of our Sun,” Xu said. “In order to identify potentially habitable hosts, it is helpful to start with our nearby neighbors. But if close binaries are common among ultracold dwarfs, few habitable worlds could be found.”

Now that astronomers have found one such dense system, they want to know if there are more. This is the only way to understand all these different scenarios.

It’s hard to even jump to any conclusions when you only have one data point.

But astronomers don’t know if they’ve only found one because they’re very rare or because they’re so hard to spot.

“These systems are rare,” said Chris Theissen, study co-author and chancellor researcher at the University of California, San Diego.

“But we don’t know if they are rare because they rarely exist, or because we just don’t find them. This is an open question. We now have one data point to start with. This data has been archived for a long time. The Dino tool will allow us to find more of these binaries.”

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