Some planets have a strange ability to slow down their sidereal age
(ORDO NEWS) — It seems stars have an anti-aging trick that people can only dream of: their families.
Astronomers have found that the presence of a planet of the right size, orbiting its parent fast enough, appears to slow down the star’s aging process.
In particular, a gas giant in a close orbit can transfer angular momentum to the star’s rotation, counteracting the gradual loss of rotation due to the decelerating effect of the star’s magnetic field.
The influence of exoplanets on the rotation of their host star is a little tricky to study. If you’re looking at one star and one planet, you have almost no way of knowing if the planet actually affected the rotation rate at all.
However, many stars in the universe occur multiple times. star systems. Binary stars are usually stellar twins born in the same nebula from the same collection of dust and gas.
Thus, their properties are often very similar. They have similar color, size, brightness and, yes, rotation.
So, in order to study in more detail the influence of planets on the rotation and activity of stars, a group of astronomers led by Nikoleta Ilich from the Leibniz Institute for Astrophysics in Potsdam (AIP) in Germany conducted the equivalent of a twin study for stars.
They were looking for binary star systems in which one star has exoplanets in orbit and the other does not.
They then used the planetless star as a reference point to look for changes potentially caused by a planet orbiting another star.
But one star system would not be enough to establish a pattern; in their study, the team carefully examined 34 binaries.
“In medicine, you need a lot of patients included in a study to know if the effects are real or if they are some kind of outliers,” says Ilic.
“The same may be true in astronomy, and this study gives us confidence that these hot Jupiters do make the stars they orbit appear younger than they are.”
Hot Jupiters are weirdos. These are gas giants, like Jupiter, but they hang incredibly close to their stars – with an orbital period of days or even hours. In such proximity, they are overheated by the star, for which they got their name.
Ilich and her colleagues studied X-ray data from NASA‘s Chandra Observatory on their 34 binary systems.
Because faster-rotating stars exhibit more X-ray activity than slower-rotating stars, they were able to find a distinct difference in rotation rates between two stars in their binary pairs.
Of course, the faster stars were those with hot Jupiters; giants that orbited at a greater distance from their star had no noticeable effect. This excludes our own Sun (sorry Sun).
Since the rotation of stars gradually slows down over time, young stars tend to rotate faster than older stars with similar properties. This suggests that hot Jupiters are something of a wrinkle cream for the stars.
The interaction between the star and the exoplanet leads to a transfer of rotation from the exoplanet to the star, which increases the rotation of the latter.
The finer details of this interaction currently remain a mystery. F or for analysis purposes, the researchers assumed that it was a tide based on the gravitational attraction between the two bodies.
But magnetic forces may have played a role. Further investigation may help to find out the smallest details.
“In previous cases, there were very intriguing hints, but now we finally have statistical evidence that some planets do influence their stars. and keep them young,” says AIP astronomer Marzi Hosseini.
“Hopefully, future research will open up more systems to better understand this effect.”
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