An exoplanet with a mass 11 times that of Jupiter – HD 106906 b – is located 336 light-years from Earth. It was discovered in 2013 with the Giant Magellanic Telescope in Chile’s Atacama Desert. However, astronomers knew nothing about the planet’s orbit.
This required what only the Hubble Space Telescope could do: measure the movement of an object over 14 years with high accuracy. Over the course of 14 years, he took further pictures, collecting data on the movement of the planet even when it was not yet discovered.
The authors of the new work used data from the Hubble archive, with the help of which they were able to describe the orbit of a distant celestial body. It was this apparatus that was able to collect the most data about the system under study.
It turned out that the exoplanet is extremely far from its two parent stars – at a distance of 730 astronomical units (one astronomical unit corresponds to the distance from the Sun to the Earth). A year on such a planet is estimated to be about 15,000 years. The object is moving so slowly in its orbit due to the weak attraction of the parent stars.
Astronomers have found that the exoplanet has such an elongated orbit offset from the center of mass of the system. The orbit extends beyond the debris disk within the system, which is located approximately the same distance from the star as the Kuiper belt in the solar system. The debris disk also looks unusual, possibly due to the gravitational pull of a distant planet. Based on the data obtained, the researchers predicted a potential mechanism for the formation of such celestial bodies.
So what happened to the exoplanet?
According to astronomers, the exoplanet was formed close enough to its parent stars – at a distance of about 3 astronomical units. But the stress that arose in the gas-dust disk forced the body to change its orbit so that it passed very close to the parent stars. As a result, due to the effect of the gravitational catapult, the planet was thrown out of the system into a very elongated orbit. A star passing by by chance stabilized the planet’s orbit, giving it the characteristics that it has now.
What does Planet Nine have to do with it?
The discovery of such an exoplanet and the mechanism of its formation could help researchers understand where to look for a hypothetical ninth planet in the solar system, the presence of which could explain the anomaly in the distribution of the orbits of trans-Neptunian objects.
The discovery of the exoplanet made by the Hubble Telescope does show that the existence of such planets is possible. Hypothetical Planet Nine could be very similar to HD 106906 b. It could have formed in the early stages of the development of the solar system in its inner part and later be thrown to the outskirts by our giant – Jupiter – far beyond Pluto. And a star passing by chance could also stabilize the planet’s orbit, giving it unusual characteristics.
To date, astronomers have only indirect evidence of the existence of the Ninth Planet. They discovered a cluster of small celestial bodies behind Neptune, which move in orbits unusual relative to other objects in the solar system. Some astronomers argue that such a configuration of orbits can only be explained by the presence of a rather large invisible planet.
This theory has an alternative, which is that the reason for the unusual characteristics of the orbits of some trans-Neptunian objects is the gravitational influence of many much smaller bodies. Some believe that there is no Ninth Planet at all, and the unusual configuration of the orbits of objects in the Zaneptune is just a statistical anomaly. One way or another, the question remains open and astronomers hope that this exoplanet could be the answer.
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• Hubble Pins Down Weird Exoplanet with Far-Flung Orbit. (n.d.).
• Jenner, L. (2020, December 09). Hubble Pins Down Weird Exoplanet with Far-Flung Orbit.
• Meiji M. Nguyen et al 2021 AJ 161 22. First Detection of Orbital Motion for HD 106906 b: A Wide-separation Exoplanet on a Planet Nine–like Orbit