There’s more to the distant gas giant than meets the eye.
Named TIC 241249530 b, the exoplanet is located about 998 light-years from Earth. NASA’s Transiting Exoplanet Survey Satellite (TESS) In January 2020, the star passed, or “transited,” across the face of its parent star.
The planet orbits its star, TIC 241249530, at a distance of about 12% of the distance between the Sun and the Moon. Earth and Sun This close proximity means that the planet orbits once every just 15.2 Earth days. But that’s not the only reason the planet’s orbit is so extreme.
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Most planets do not have perfectly circular orbits. Instead, the majority of planetary orbits are elliptical with some degree of flattening, which astronomers call “eccentricity.” TIC 241249530 b has the most elongated and flattened orbit astronomers have ever seen. Additionally, the Jupiter-sized planet orbits its star “backwards” relative to the star’s rotation.
But a hot Jupiter is an exoplanet that orbits a planet at a distance that takes just 10 Earth days or less to complete an Earth year. That means TIC 241249530 b isn’t a hot Jupiter — at least, not yet. Right now, it’s a mystery to astronomers how hot Jupiters work. Hot Jupiter Because these planets get so close to their parent stars, scientists speculate that they may form farther away from the parent star and then migrate inward.
But the early stages of this migration process remain frustratingly elusive, even though astronomers have observed and confirmed at least one phenomenon. 5,600 exoplanets.
The team of astronomers used two instruments on the WIYN 3.5-meter telescope to Kitt Peak National Observatory (KPNO) observed TIC 241249530 b and revealed that it is an early-stage hot Jupiter.
“For more than 20 years, astronomers have been searching for exoplanets that could be precursors to hot Jupiters or intermediate products in the transition process, so this discovery was very surprising and exciting,” said Arvind Gupta, a postdoctoral researcher at NOIRLab and team leader. It said in a statement “Exactly what I was looking for.”
Formation of Hot Jupiters
Scientists first used the NN-EXPLORE Exoplanet and Stellar Spectroscope Imager (NESSI) “Sparkle” patterns caused by Earth’s atmosphere It also reduces noise coming from other light sources that could contaminate the signal from the star, TIC 241249530, as the planet passes over its surface.
The researchers then used the NEID spectrometer to measure the exoplanet’s speed around the star and determine changes in the star’s light.
“NESSI provided us with much clearer images of the star than would have been possible otherwise, and NEID precisely measured the star’s spectrum to detect changes in response to the exoplanet orbiting it,” Gupta said.
When the team analyzed the spectrum, they determined that TIC 241249530 b has a mass roughly five times that of Jupiter, and that the planet’s orbit is extremely eccentric. Eccentricity of a planet’s orbit is measured on a scale of 0 to 1, with 0 being a perfectly circular orbit and 1 being a highly elliptical orbit.
Dwarf planet Pluto An elliptical orbit around the Sun has an eccentricity of 0.25, while Earth’s nearly circular orbit has an eccentricity of 0.02. TIC 241249530 b’s orbit has an eccentricity of 0.94, making it more eccentric than the orbit of any exoplanet discovered so far. The transit method of exoplanet detection.
Of note is another planet with a flatter orbit, the gas giant HD 20782 b, 1,117 light years away. This planet has an orbital eccentricity of 0.956, but this planet was not discovered using the transit method.
An image showing the oddly elongated orbit of TIC 241249530 b compared to the nearly circular orbits of Earth and Mercury, the planets closest to the Sun. (Image courtesy of NOIRLab/NSF/AURA/R. Proctor)
If TIC 241249530 b were placed within the solar system, its orbit would bring it nearly 10 times closer to the Sun. Mercury (about 3 million miles, or 4.8 million kilometers) and The greatest distance from the Earth to the Sun (About 95 million miles, or 153 million kilometers.) This causes temperatures on TIC 241249530 b to range from a comfortable summer’s day on Earth to temperatures hot enough to melt lead.
TIC 241249530 b’s motion around its star also has another unusual feature. The planet orbits the star in the opposite direction to the star’s rotation, a phenomenon known as “Retrograde motion This is a feature rarely seen on exoplanets, and is only seen on two planets in our solar system. Venus and Uranus.
These two features of TIC 241249530 b’s orbit led the team to believe that the planet is on the verge of transforming into a hot Jupiter. The team believes that as the planet approaches its star due to its highly eccentric orbit, it will begin to bulge, like the 2D shadow of an inflated beach ball. This is expected to happen because tidal forces generated by the star’s gravity pull orbital energy away from the exoplanet.
As the planet’s orbit “circularizes,” it also shrinks, pulling TIC 241249530 b closer to its star until its year is less than 10 Earth days, marking the completion of its transformation into a hot Jupiter.
TIC 241249530 b is the second exoplanet discovered that appears to be in the pre-hot Jupiter transition stage. TIC 241249530 b and previous examples of such hot Jupiter progenitor planets appear to support the transformation of high-mass exoplanets. Gas giants It transforms into a hot Jupiter through the transition from a highly eccentric orbit to a narrower, more circular orbit.
Press the rewind button Planetary migration “This exoplanet acts as a sort of snapshot of the migration process in real time,” Gupta concluded. “Planets like this are very rare and hard to find, so we hope they can help us unravel the story of hot Jupiter formation.”
The research team’s study was published in the journal Neurology on July 17th. Nature.
