Exoplanets have been found in all different types and sizes, showing how much diversity there is among planets outside of our own Solar System. Now another one, a "monster exoplanet," is of interest to astronomers because according to current models of planetary formation, it shouldn't exist — but does.
The giant planet, called NGTS-1b, is known as a "hot Jupiter," a gas giant similar to Jupiter but scorching hot due to orbiting close to its star. That's not so unusual, but what is odd is that the planet orbits a very small red dwarf star. Current understanding of planetary formation says that such a large planet shouldn't be able to form easily around such small stars.
It should be noted that although this is actually the third hot Jupiter found orbiting a red dwarf star, it is also the largest planet compared to the size of its companion star ever discovered so far, making it a bit more unique. From the new paper:
"NGTS-1b is the third transiting giant planet found around an M-dwarf, reinforcing the notion that close-in gas giants can form and migrate similar to the known population of hot Jupiters around solar type stars."
NGTS-1b, about 600 light years away, orbits its star in only 2.6 days and its orbit is only 3 percent of the distance between Earth and the Sun.
According to Professor Peter Wheatley from the University of Warwick, "Despite being a monster of a planet, NGTS-1b was difficult to find because its parent star is so small and faint. Small stars like this red M-dwarf are actually the most common in the Universe, so it is possible that there are many of these giant planets waiting to found."
The planet was discovered by monitoring patches of the night sky over many months, and detecting the red light from the star with innovative red-sensitive cameras.
Hot Jupiters have been found to be quite common in our galaxy, but mostly orbiting larger stars.
As Dr. Daniel Bayliss, lead author of the study and also from the University of Warwick, noted, "The discovery of NGTS-1b was a complete surprise to us — such massive planets were not thought to exist around such small stars — importantly, our challenge now is to find out how common these types of planets are in the Galaxy, and with the new Next-Generation Transit Survey (NGTS) facility we are well-placed to do just that."
NGTS-1b is also the first exoplanet to be discovered by NGTS.
"Having worked for almost a decade to develop the NGTS telescope array, it is thrilling to see it picking out new and unexpected types of planets," said Wheatley. "I'm looking forward to seeing what other kinds of exciting new planets we can turn up."
So far, about 3,500 exoplanets have been found in our galaxy by the Kepler Space Telescope and other observatories. The total number is estimated to be in the billions for our galaxy alone, and some studies have even suggested that there are more planets than stars. Many are hot-Jupiters, but the most common appear to be smaller planets, including "super-Earths" which are rocky planets larger than Earth but smaller then Neptune. That is good news as far as the search for extraterrestrial life is concerned. In the next few years, telescopes will also be better at analyzing the atmospheres of some of these planets, looking for possible biosignature gasses such as oxygen or methane.
The largest exoplanet discovered so far is DENIS-P J082303.1-491201 b, which has a mass 28.5 times that of Jupiter; it is so massive that it may actually be a brown dwarf, a "failed star," rather than a planet.
The new paper, "NGTS-1b: A hot Jupiter transiting an M-dwarf," is available here.