Astronomers have discovered a new exoplanet that is massive coming in at three times the mass of Jupiter. The giant planet travels on a long, egg-shaped path around its star. The scientists say that if the planet, called HR 5183 b, were placed into our solar system it would have a highly elliptical orbit that took it from within the asteroid belt out past Neptune.
Giant planets with highly elliptical orbits have been discovered before, but none of them was at the outer reaches of its parent star system. Astronomer Sarah Blunt says that the highly eccentric nature of the planet’s orbit speaks to some difference in either the way it formed or evolved relative to the other planets in the system.
The planet was discovered using the radial velocity method where planets are discovered using the way the host star wobbles. This method requires observations taken over a planet’s entire orbital period that can take tens or hundreds of years. This particular host star has been watched since the 1990s, but so far there is no data on the full orbit of HR 5183 b because it circles the star every 45 to 100 years.
The planet was discovered because of its strange orbit. The team says that the planet spends most of its time loitering in the outer part of the star’s planetary system. As it moves closer to the star, it accelerates and slingshots around the star. The team detected the slingshot motion.
The findings show that scientists can detect planets using the radial velocity method without having to wait for decades. One theory on how the planet got such an eccentric orbit is that it once had a neighbor of similar size and when the two planets got too close, HR 5183 b was pushed out of the solar system.