Astronomers have discovered a giant planet whose extreme orbit makes it different from anything they've ever seen.
Called HR 5183 b, the exoplanet is at least three times as massive as Jupiter and requires a long, circular path around a star that lies about 100 light-years away in the constellation Virgo. If the exoplanet were in our own solar system – in which the Earth and other planets orbit the Sun in almost circular orbits – its extremely elliptical orbit would have carried it beyond Neptune to Jupiter's orbit (see video below).  The discovery shows that "our universe is filled with many strange solar systems, completely unlike our own," Sarah Blunt, a graduate student at the California Institute of Technology in Pasadena and one of the scientists behind the discovery, said in an email. , "It seems that every time we think we have discovered the strangest solar system, something very strange is discovered."
Blunt, the lead author of an article on the discovery, called the exoplanet a "crazy object" and likened its movements around the host star, HR 51
She said that other exoplanets are highly elliptical or eccentric orbits have been observed, but HR 5183 b is the only one known to orbit a star at such extreme distances.
"Something must have interacted with the planet to pump its eccentricity," she says in an email, adding that one possible scenario is that HR 5183 b once had a neighboring planet whose gravity deflects the exoplanets. But it may be a star that has deflected the exoplanets – or "something we haven't thought of yet."
Astronomers did not observe HR 5183 b directly but concluded its size and orbit by observing small "oscillations" in light from the host star caused by the changing gravitational pull of the orbiting planet (a technique known as radial velocity method). The data that led to the discovery come from observations made at the Lick Observatory in Hamilton, California; the Keck Observatory in Waimea, Hawaii; and the McDonald Observatory in Fort Davis, Texas.
Brendan Bowler, an astronomer at the University of Texas who did not participate in the new research, welcomed the discovery, saying that the extrasolar planet's orbit around its star "tells us something about the outskirts of planetary systems." on the road to "understanding how planets form and understanding their statistical properties."
The astronomers behind the discovery have not yet been made with HR 5183 b. Blunt said it may be possible to determine the absolute mass of exoplanets using data from the European Space Agency's Gaya Observatory, which aims to perform a detailed count of about 1 million stars. In addition, she said, astronomers can simulate the formation of HR 5183 b to learn more about the conditions that led to such an exoplanet.
"There are many next steps for this planet!"
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