Skip to main content
  1. Home
  2. Space
  3. News

Unusual puffy exoplanet has the density of marshmallow

By

Exoplanets come in all sorts of sizes and all sorts of densities, from solid rocky planets like Earth or Mars to super-puff planets discovered by Hubble. Now, researchers using the WIYN 3.5-meter Telescope at Kitt Peak National Observatory have identified a puffy, low-density “marshmallow” planet orbiting a cool red dwarf star. TOI-3757 b, located 580 light-years away, is the lowest-density gas giant planet ever discovered orbiting this kind of star.

Red dwarfs are the most common type of star in the galaxy and are cooler than our sun, but they can give off powerful flares of radiation that would bombard nearby planets with ultraviolet light. These flares could strip the atmosphere off a planet, so it was thought that it would be unlikely to find puffy gas giants orbiting these stars.

Recommended Videos

A gas giant exoplanet [right] with the density of a marshmallow has been detected in orbit around a cool red dwarf star [left] by the NASA-funded NEID radial-velocity instrument on the 3.5-meter WIYN Telescope at Kitt Peak National Observatory, a Program of NSF’s NOIRLab. The planet, named TOI-3757 b, is the fluffiest gas giant planet ever discovered around this type of star.
A gas giant exoplanet [right] with the density of a marshmallow has been detected in orbit around a cool red dwarf star [left] by the NASA-funded NEID radial-velocity instrument on the 3.5-meter WIYN Telescope at Kitt Peak National Observatory, a Program of NSF’s NOIRLab. The planet, named TOI-3757 b, is the fluffiest gas giant planet ever discovered around this type of star. NOIRLab/NSF/AURA/J. da Silva/Spaceengine/M. Zamani
“Giant planets around red dwarf stars have traditionally been thought to be hard to form,” said lead researcher Shubham Kanodia of the Carnegie Institution for Science in a statement. “So far this has only been looked at with small samples from Doppler surveys, which typically have found giant planets further away from these red dwarf stars. Until now we have not had a large enough sample of planets to find close-in gas planets in a robust manner.”

Related

The researchers think that this unusual planet was able to form because of the composition of its stars and its orbit. The star has an unusually low level of heavier elements which could have caused the core of the planet to form more slowly than is typical, making it acquire gas slowly and contributing to its low density. The planet’s orbit seems to be elliptical as well, meaning it comes closer to the star at some times than at others, which would have warmed the planet and caused its atmosphere to puff up further.

Current estimations put the density of the planet at an average of 0.27 grams per cubic centimeter, which is less than half the density of Saturn — “or in fact, similar in density to a marshmallow,” as NOIRLab writes.

The researchers plan to make more observations of the planet using the James Webb Space Telescope, looking at its atmosphere in particular. And they plan to search for other similar planets.

“Finding more such systems with giant planets — which were once theorized to be extremely rare around red dwarfs — is part of our goal to understand how planets form,” said Kanodia.

The research is published in The Astronomical Journal.

Editors’ Recommendations

Topics
Georgina Torbet
Georgina Torbet
Space Writer
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
Tatooine-like exoplanet orbits two stars in rare astronomical discovery
An artist's illustration shows that the stars in the TOI 1338 system make an eclipsing binary — they circle each other in our plane of view.

Anyone who has watched Star Wars has likely found themselves enchanted by the views from Luke's home planet of Tatooine, with its pair of suns visible in the sky over the desert. As visually striking as this concept it, it isn't purely fantasy: there do exist planets that orbit two stars, called circumbinary systems, and standing on one of these planets you would see two stars in the sky.

Astronomers recently discovered one such planet, named BEBOP-1c. Located in the same system as a previously discovered planet, TOI-1338b, the team was trying to measure the mass of the older known planet when they discovered the new one. “Only 12 circumbinary systems are known so far, and this is only the second that hosts more than one planet,” said one of the researchers, David Martin of Ohio State University, in a statement.

Read more
Hubble image of the week shows an unusual jellyfish galaxy
The jellyfish galaxy JO206 trails across this image from the NASA/ESA Hubble Space Telescope, showcasing a colorful star-forming disk surrounded by a pale, luminous cloud of dust. A handful of foreground bright stars with crisscross diffraction spikes stands out against an inky black backdrop at the bottom of the image. JO206 lies over 700 million light-years from Earth in the constellation Aquarius.

This week's image from the Hubble Space Telescope shows an unusual type of galaxy named for its aquatic look-alike: a jellyfish.

The jellyfish galaxy JO206 is shown below in an image taken using Hubble's Wide Field Camera 3 instrument. Located 700 million light-years away, in the constellation of Aquarius, this image of the galaxy shows both the bright center of the galaxy and its long tendrils reaching out toward the bottom right. It is these tendrils that give jellyfish galaxies their names, and they are formed through a process called ram pressure stripping.

Read more
CHEOPS planet-hunter detects four rarely seen mini-Neptunes
Artist's impression of Cheops, ESA's Characterising Exoplanet Satellite, in orbit above Earth.

The European Space Agency (ESA)'s CHEOPS satellite has discovered four new exoplanets -- and they are a hard-to-detect type called a mini-Neptune. These planets are notable because they are the "missing link" between rocky Earth-sized planets and ice giants like Neptune. They are thought to be very common in our galaxy, but they are hard to spot because they are small and cool compared to the big, bright hot Jupiters which are most commonly detected by exoplanet-hunting telescopes.

Mini-Neptunes do orbit close to their stars, typically being found closer to their stars than Mercury is to the sun. However, hot Jupiters orbit even closer -- which gives them very high surface temperatures of over 1,000 degrees Celsius. Mini-Neptunes have relatively cooler surface temperatures of around 300 degrees Celsius.

Read more