Found a planetary system with almost perfect orbital "harmony"

Found a planetary system with almost perfect orbital "harmony"
Found a planetary system with almost perfect orbital "harmony"
Anonim

To date, astronomers have discovered hundreds of planetary systems scattered throughout the galaxy. Each is unique, but the system orbiting HD 158259, 88 light years away, is particularly unusual.

The mass of HD 158259 is comparable to that of the Sun and slightly larger in diameter than the Sun. The planet closest to the star is a super-earth with a mass about twice that of the Earth and with a radius of 1, 2 of the Earth. The rest of the celestial bodies are about six times heavier than the Earth and belong to the class of minineptuns.

After observing the system for seven years, astronomers found that all six planets revolve around their star in near-perfect orbital resonance. This discovery may help us better understand how planetary systems form and how they end up in the configurations we see.

Orbital resonance in celestial mechanics is a phenomenon where the orbits of two bodies around a parent body are closely related, since both objects exert a gravitational effect on each other. So, in the solar system, Neptune and Pluto are in the 3: 2 orbital resonance. This means that for every two circles Pluto makes around the Sun, Neptune makes two. It resembles musical measures performed simultaneously, but with different time signatures - two beats for the first and three for the second.

t.co/K1nYvT6SOt Scientists discover six-planet system moving almost in rhythm. The planets are said to be in almost 3: 2 resonance. This means that for every three orbits of the innermost planet, the second innermost one completes two orbits. And for every three orbits o…

- Science news (@UpdateonScience) April 18, 2020

The researchers found that in the HD 158259 system, all the planets are as close as possible to an orbital resonance of 3: 2, which can also be described as the ratio of periods - 1, 5. Using measurements made using the SOPHIE spectrograph and the TESS space telescope, an international team of researchers led by astronomer Nathan Haray of the University of Geneva in Switzerland was able to accurately calculate the orbits of each planet.

All of them are located compactly: even the outermost of the six exoplanets of the system is 2, 6 times closer to the star than Mercury is to the Sun. These planets make a complete revolution around HD 158259 in 2, 7, 3, 4, 5, 2, 7, 9, 12 and 17, 4 Earth days, respectively.

Consequently, the ratio of the periods for each pair of planets is 1, 57; 1, 51; 1, 53; 1, 51 and 1, 44. This is not exactly a perfect resonance, but it is close enough to classify HD 158259 as an extraordinary system.

It is believed that the planets that are in resonance form at a relatively large distance from the star. It is likely that the HD 158259 system was once the same, but later became compact.

“There are several known compact systems with several planets in or near resonances, for example, TRAPPIST-1 or Kepler-80. It is believed that such systems form far from the star before migrating to it. In this scenario, resonances play a decisive role,”- astronomer Stéphane Oudry of the University of Geneva.

This is because these resonances are thought to arise when protoplanets (planetary embryos) in a protoplanetary disk grow and migrate inward, away from the outer edge of the disk. This creates a chain of orbital resonance throughout the system. Then, when the remaining disk gas dissipates, it can destabilize the orbital resonances, as in HD 158259. These tiny differences in orbital resonances can tell us more about how this destabilization occurs.

“The current deviation of period ratios from 3: 2 contains a wealth of information. With these values on the one hand and tidal models on the other, we could figure out the internal structure of the planets in future studies. Thus, the current state of the system opens a window for us at the time of its formation,”- Nathan Hara.

The study was published in the journal Astronomy & Astrophysics.

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