Astronomers in Poland have discovered a nearby exoplanet more than 11 times the size of Jupiter, placing it well within the realm of the largest known worlds.
The object is a cold super-Jupiter; simply put, that means it’s colder and bigger than Jupiter, the yardstick by which the largest planets are measured. The characteristics of a very large exoplanet—and the star system where it resides—are described in a paper published last month. Astronomy & Astrophysics.
The giant Earth sits in a multi-planet system a little more than 300 light-years from Earth in the constellation Ursa Major. The host star in the system, HD 118203, is about 20 percent as massive and twice as massive as our Sun, but older than our star. One of the planets in the system—hot Jupiter that’s just twice the size of Earth—was spotted by the Transiting Exoplanet Survey Satellite (or TESS) back in 2005.
“However, the Doppler observations showed that this was not the end of the story, that there might be another planet out there,” said Andrzej Niedzielski, an astronomer at Nicolaus Copernicus University in Poland, in a university speech. “So, we immediately put this program on our watch list.”
Using TESS data and measurements from the 12-foot (3.6-meter) Telescopio Nazionale Galileo and Texas’ Hobby-Eberly 9-meter telescope, the team analyzed the system and saw that there was another object orbiting the star. Although the planet itself is invisible—the star is too bright to be seen—the team discovered its presence through radial velocity data that caused the star’s brightness to change slightly over time.
In an eccentric twist, the hot Jupiter seen in 2005 was found to be on an orbit just over six days long. The newly described cold super-Jupiter has a more leisurely cycle: It takes the exoplanet about 14 years to complete an orbit around its star.
The largest exoplanet is not the largest known to astronomers. That subject belongs to TrES-4b, which resides about 1,430 light-years away in the constellation Hercules. TrES-4b is 142,915 miles (230,000 km) in diameter, compared to Jupiter’s radius of 88,670 miles (142,700 km). But TrES-4b is slightly larger than Jupiter—so the newly described world is really dense.
The line between “massive exoplanet” and “massive brown dwarf” is often blurred, but at about 11 Jupiter masses, the cold super-Jupiter is in the same orbit as the giant Beta Pictoris b, which is several times -12 is heavier. of Jupiter and 63 light years away from Earth.
Source link
