Lead author Dr. Ed Bryant (Mullard Space Science Laboratory at UCL, formerly the University of Warwick), who initiated the work as part of his Ph.D., stated: “Low-mass stars are better at forming giant worlds than we believed. In specific, our detection of gas giants orbiting stars as low as 20% of the mass of the Sun postures a conflict with current theory.”
One possible interpretation is that gas giants do not form through core accretion however through gravitational instability, where the disk surrounding a star pieces into planet-sized clumps of dust and gas. If this is the case, low-mass stars could host very large gas giants, 2 or three times the mass of Jupiter. The team will infer these items masses by looking for a “wobble” in their host stars position, indicating the possible worlds gravitational yank.
In the research study, which was recently released in the Monthly Notices of the Royal Astronomical Society (MNRAS) and funded by the UK Science and Technology Facilities Council (STFC), scientists took a look at 91,306 low-mass stars, using observations from NASAs Transiting Exoplanet Survey Satellite (TESS), and in 15 cases found dips in the brightness of the light representing a gas giant passing in front of the star.
Artists impression of dawn on planet NGTS-1b, a gas giant formerly discovered orbiting a low-mass star. Credit: University of Warwick/Mark Garlick
Five out of the 15 possible giant worlds have since been validated as planets using independent techniques. One of these validated planets orbits a star that is a fifth of the mass of the Sun– which would not be possible according to planet development designs.
Lead author Dr. Ed Bryant (Mullard Space Science Laboratory at UCL, previously the University of Warwick), who initiated the work as part of his Ph.D., said: “Low-mass stars are much better at forming giant worlds than we thought. Our results raise serious questions for planet formation models. In specific, our detection of gas giants orbiting stars as low as 20% of the mass of the Sun postures a dispute with current theory.”
Co-author Dr. Vincent Van Eylen (Mullard Space Science Laboratory at UCL): “The truth that, although uncommon, gas giants do exist around low-mass stars suggests and is an unforeseen finding that models of world development will need to be modified.”
One possible interpretation is that gas giants do not form through core accretion however through gravitational instability, where the disk surrounding a star fragments into planet-sized clumps of dust and gas. Low-mass stars could host really big gas giants, 2 or three times the mass of Jupiter if this is the case. Nevertheless, this is considered unlikely, as the disks around low-mass stars do not appear to be massive sufficient to fragment in this way.
Another explanation, the scientists say, is that astronomers have underestimated how massive a stars disk can be, indicating small stars might form giant worlds via core accretion.
This could either be because we have incorrectly calculated the mass of disks we can observe through telescopes, or because disks have a greater mass at the start of a stars life when they are extremely challenging to observe (as they are embedded in clouds of dust), compared to later on in a stars life when we can observe them.
Co-author Dr. Dan Bayliss (University of Warwick) stated: “Its possible we dont comprehend the masses of these protoplanetary disks as well as we thought we did. Effective new instruments such as the James Webb Space Telescope will be able to study the properties of these disks in more information.”
In their paper, the researchers sought to identify how frequently huge worlds took place around low-mass stars, screening if this occurrence rate fit with what core accretion designs would anticipate.
They utilized an algorithm to identify the signals of transiting gas giants in the light emitted by low-mass stars. They then vetted these signals, marking down a number of false positives.
To figure out how likely their technique was to detect actual gas giants orbiting these stars, they placed simulations of thousands of signals of transiting planets in the actual TESS starlight data and after that ran their algorithm to see how many of these worlds would be spotted.
These prospects could possibly be buddy stars or there could be another reason for the dips in brightness. The team will infer these items masses by looking for a “wobble” in their host stars position, showing the possible planets gravitational tug.
Reference: “The occurrence rate of huge worlds orbiting low-mass stars with TESS” by Edward M Bryant, Daniel Bayliss and Vincent Van Eylen, 3 March 2023, Monthly Notices of the Royal Astronomical Society.DOI: 10.1093/ mnras/stad626.
Artists impression of dawn on world NGTS-1b, a gas giant formerly found orbiting a low-mass star. Credit: University of Warwick/Mark Garlick
Stars with a mass less than half that of the Sun can harbor huge gas giants similar to Jupiter, contradicting the dominating theory of planetary development, a current research study by scientists from University College London (UCL) and the University of Warwick reveals.
Gas giant worlds, together with other celestial bodies, originate from the material disks encircling young stars. The core accretion theory posits that these worlds at first develop a core of rock, ice, and other heavy solids, which, upon reaching a mass 15 to 20 times that of Earth, draws in a gaseous outer layer.
Nevertheless, low-mass stars have low-mass disks that, designs predict, would not offer enough material to form a gas giant in this way, or at least not quickly adequate before the disk separates.
