2023-07-22 15:54:31
A galaxy can throw strange curveballs, but an exoplanet discovered 1,232 light-years away is one of the strangest yet. It’s WASP-193b, and although it’s regarding 50% more massive than Jupiter, it’s so light and fluffy that its overall density is comparable to that of cotton candy. That’s just a hair over 1% of Earth’s density. It’s an absolute dandelion ball from a world…if a dandelion ball might ever be a planet. Although little known, exoplanets like WASP-193b are rare, and might help us better understand planetary evolution, according to an international team led by astronomer Khaled Barkawi of the University of Liège in Belgium. A paper describing the discovery has been accepted for publication and is available on the arXiv preprint server. Artist’s impression of a bloated world. (NASA, ESA, CSA, J. Olmsted/STScI) Looking at all the weird and wonderful worlds out there not only allows us to contextualize our own solar system, but it also provides a window into how planetary systems formed and evolved. Gas giants near their stars is a great tool for this because our understanding of planet formation means they must have formed elsewhere and migrated inward. In addition, the star’s radiation also means that many of these worlds are shrinking. WASP-193b is an exoplanet orbiting a sun-like star named WASP-193. This star has a mass of regarding 1.1 times the radius of the Sun by 1.2 times, and it is very close to the Sun in terms of temperature and age. But WASP-193b orbits its star much closer than any planet in the solar system: It gets bigger regarding once every 6.25 days. Studying how the light from a star changes as an exoplanet orbits it allowed Barkawi and his colleagues to calculate its radius and mass. Its radius is regarding 1.46 times the radius of Jupiter. But in comparison, its mass is incredibly small: only 0.139 times that of Jupiter. From these characteristics, the researchers deduced the exoplanet’s density: 0.059 grams per cubic centimeter. By comparison, Earth’s density is 5.51 grams per cubic centimeter. Jupiter’s density is 1.33 grams per cubic centimeter, which makes sense – there are a lot of clouds. The density of cotton candy is 0.05 grams per cubic centimeter. Animation showing how radial velocity is measured, which is one of the ways a planet can affect the light from its star. (Alyssa Ubertas/Wikimedia Commons/CC BY-SA 4.0) Very few other worlds of similar density have been found, but they do provide some clues as to how such thin worlds exist. The proximity of the star can cause the atmosphere to heat up and swell, especially if that atmosphere is mainly hydrogen and helium. But such a world will only look like WASP-193b for a few tens of millions of years or so, when the star is younger and hotter; Moreover, the star’s heat and winds can strip such a fragile atmosphere very quickly. So this poses some problems. The star is believed to be up to 6 billion years old; Although there may be a mechanism for internal heat to inflate WASP-193b’s atmosphere, the observed properties of the exoplanets cannot be recreated using complex models of planetary evolution. The good news is that WASP-193b makes an excellent candidate for follow-up studies to see what its atmosphere is made of. This is one of the tasks the James Webb Space Telescope is designed for; Only one transit observation, the team says, might provide information explaining how such a thin, alien world might exist in the universe. The team’s research has been accepted for publication and is available on arXiv.
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