Astronomers have discovered an exoplanet that’s five times the mass of Jupiter and follows a very unusual orbit around its star.
Artist’s impression of TIC 241249530b. Image courtesy of NOIRLab / NSF / AURA / J. da Silva, Spaceengine.
TIC 241249530b was first detected in January 2020 by NASA’s Transiting Exoplanet Survey Satellite (TESS).
To confirm that the object is a planet, astronomers used two instruments on NSF Kitt Peak National Observatory’s WIYN 3.5-meter telescope, a program of NOIRLab.
They first harnessed the NN-EXPLORE Exoplanet and Stellar Speckle Imager (NESSI) with a technique that “freezes” atmospheric glitter, eliminating extraneous light sources that could confuse the signal source.
The team then used the NEID spectrometer to carefully observe how the host star’s spectrum, or the wavelengths of light it emits, changes as a result of the exoplanet orbiting TIC 241249530b, and measure the radial velocity of TIC 241249530b.
“NESSI provided much sharper images of the star than was possible with any other method, while NEID precisely measured the star’s spectrum and detected changes in response to the exoplanet orbiting it,” said Dr. Arvind Gupta, a postdoctoral researcher at NOIRLab.
“The unique flexibility of NEID’s observing schedule framework allows the team to quickly adjust their observing plans in response to new data.”
Analysis of the spectrum confirmed that TIC 241249530b has a mass about five times that of Jupiter.
The spectrum also revealed that the exoplanet orbits along a highly eccentric, or elongated, orbit.
The eccentricity of a planet’s orbit is measured on a scale from 0 to 1, with 0 representing a perfectly circular orbit and 1 representing an elliptical orbit.
The exoplanet’s orbital eccentricity is 0.94, higher than any exoplanet discovered so far by the transit method.
By comparison, Pluto orbits the Sun in an elliptical orbit with an eccentricity of 0.25. Earth’s eccentricity is 0.02.
If the planet were part of the solar system, its orbit would stretch from its closest point, ten times closer to the Sun than Mercury, to its farthest point, about the same distance as Earth.
This extreme orbit would cause the planet’s temperatures to vary from mild to hot enough to melt titanium.
In addition to the unusual nature of the exoplanet’s orbit, the team also discovered that it orbits in a retrograde direction, meaning it moves in the opposite direction to the rotation of its host star.
This is a phenomenon astronomers have not seen in most other exoplanets or in our own solar system, and it helps the research team interpret the history of exoplanet formation.
The exoplanet’s unique orbital properties also hint at its future trajectory.
Because its initial orbit is highly eccentric and it is so close to the star, the planet’s orbit is expected to become “circular” because the planet’s tidal forces will sap energy from the orbit, causing it to gradually shrink and become circular.
Discovering this exoplanet before this migration occurs is valuable because it will give us important insight into how hot Jupiters form, stabilize, and evolve over time.
“While we can’t hit the rewind button and watch the planetary migration process in real time, this exoplanet serves as a kind of snapshot of the migration process,” Dr Gupta said.
“Planets like this are extremely rare and hard to find, so we hope they will help shed light on how hot Jupiters form.”
“We’re particularly interested in what we can learn about the dynamics of the planet’s atmosphere after it gets so close to its star,” said Professor Jason Wright of Pennsylvania State University.
“With telescopes like the NASA/ESA/CSA James Webb Space Telescope having the sensitivity to study atmospheric changes on newly discovered exoplanets undergoing rapid heating, there is still much more for research teams to learn about exoplanets.”
TIC 241249530b is the second exoplanet discovered so far that represents the pre-transitional stage of a hot Jupiter.
Together, these two examples provide observational support for the idea that high-mass gas giants evolve into hot Jupiters as they move from highly eccentric orbits to tighter, more circular orbits.
“Astronomers have been searching for exoplanets for over 20 years that could be precursors to hot Jupiters or intermediate products in the migration process, so I was very surprised and excited to find one – it’s exactly what I was hoping to find,” Dr Gupta said.
Team paper Published in today’s journal Nature.
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Arvind Gupta others2024. Hot Jupiter ancestor on a highly eccentric retrograde orbit. Naturein press; doi: 10.1038/s41586-024-07688-3
This article is a version of a press release provided by NOIRLab.
Source: www.sci.news
