Astronomers have discovered an exoplanet five times the mass of Jupiter that makes a very peculiar orbit around its star.
An artist’s impression of TIC 241249530b. Image credit: NOIRLab / NSF / AURA / J. da Silva, Spaceengine.
TIC 241249530b was first detected by NASA’s Transiting Exoplanet Survey Satellite (TESS) in January 2020.
To confirm the planetary nature of the object, astronomers used two instruments on the WIYN 3.5-m telescope at NSF’s Kitt Peak National Observatory, a Program of NOIRLab.
They first utilized the NN-EXPLORE Exoplanet and Stellar Speckle Imager (NESSI) in a technique that helps to ‘freeze out’ atmospheric twinkling and eliminate any extraneous sources that might confuse the signal’s source.
Then, using the NEID spectrograph, they measured the radial velocity of TIC 241249530b by carefully observing how its host star’s spectrum, or wavelengths of its emitted light, shifted as a result of the exoplanet orbiting it.
“NESSI gave us a sharper view of the star than would have been possible otherwise, and NEID precisely measured the star’s spectrum to detect shifts in response to the orbiting exoplanet,” said Dr. Arvind Gupta, a postdoctoral researcher at NOIRLab.
“The unique flexibility of NEID’s observation-scheduling framework as it allows for swift adaptation of the team’s observing plan in response to new data.”
The analysis of the spectrum confirmed that TIC 241249530b is approximately five times more massive than Jupiter.
The spectrum also revealed that the exoplanet is orbiting along an extremely eccentric, or stretched-out, path.
The eccentricity of a planet’s orbit is measured on a scale from 0 to 1, with 0 being a perfectly circular orbit and 1 being highly elliptical.
This exoplanet has an orbital eccentricity of 0.94, making it more eccentric than the orbit of any other exoplanet ever found via the transiting method.
For comparison, Pluto’s highly elliptical orbit around the Sun has an eccentricity of 0.25; Earth’s eccentricity is 0.02.
If this planet was part of our Solar System its orbit would stretch from its closest approach 10 times closer to the Sun than Mercury all the way out to its most distant extent at Earth’s distance.
This extreme orbit would cause temperatures on the planet to vary between that of a summer’s day to hot enough to melt titanium.
To add to the unusual nature of the exoplanet’s orbit, the team also found that it’s orbiting backwards, meaning in a direction opposite to the rotation of its host star.
This is not something that astronomers see in most other exoplanets, nor in our own Solar System, and it helps inform the team’s interpretation of the exoplanet’s formation history.
The exoplanet’s unique orbital characteristics also hint at its future trajectory.
It’s expected that its initial highly eccentric orbit and extremely close approach to its host star will ‘circularize’ the planet’s orbit, since tidal forces on the planet sap energy from the orbit and cause it to gradually shrink and circularize.
Discovering this exoplanet before this migration has taken place is valuable as it lends crucial insight into how hot Jupiters form, stabilize, and evolve over time.
“While we can’t exactly press rewind and watch the process of planetary migration in real time, this exoplanet serves as a sort of snapshot of the migration process,” Dr. Gupta said.
“Planets like this are incredibly rare and hard to find, and we hope it can help us unravel the hot Jupiter formation story.”
“We’re especially interested in what we can learn about the dynamics of this planet’s atmosphere after it makes one of its scorchingly close passages to its star,” said Penn State’s Professor Jason Wright.
“Telescopes like the NASA/ESA/CSA James Webb Space Telescope have the sensitivity to probe the changes in the atmosphere of the newly discovered exoplanet as it undergoes rapid heating, so there is still much more for the team to learn about the exoplanet.”
TIC 241249530b is only the second exoplanet ever discovered to demonstrate the hot Jupiter pre-migration phase.
Together, these two examples observationally affirm the idea that higher-mass gas giants evolve to become hot Jupiters as they migrate from highly eccentric orbits toward tighter, more circular orbits.
“Astronomers have been searching for exoplanets that are likely precursors to hot Jupiters, or that are intermediate products of the migration process, for more than two decades, so I was very surprised — and excited — to find one. It’s exactly what I was hoping to find,” Dr. Gupta said.
The team’s paper appears today in the journal Nature.
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Arvind Gupta et al. 2024. A hot Jupiter progenitor on a super-eccentric, retrograde orbit. Nature, in press; doi: 10.1038/s41586-024-07688-3
This article is a version of a press-release provided by NOIRLab.
Source : Breaking Science News