Astronomers spot giant backward-orbiting exoplanet 1,100 light years away

Astronomers have identified a weird exoplanet orbiting backward, which is nestled 1,100 light years away from Earth.

This Jupiter-like planet, designated TIC 241249530 b, was first discovered by NASA’s Transiting Exoplanet Survey Satellite (TESS) in 2020.

The satellite noticed a slight dimming in a distant star’s light, hinting at a giant planet passing by. Astronomers used powerful Earth-based instruments to establish its existence and learn more about it.

High eccentric orbit

A team of NOIRLab researchers conducted follow-up observations using high-tech instruments (NESSI and NEID) of the WIYN 3.5-meter Telescope in Arizona.

NESSI enhanced the starlight’s clarity to minimize distractions, while NEID measured the star’s wobble caused by the planet’s gravitational pull. The analysis revealed a massive planet five times the size of Jupiter.

But here’s the twist: its orbit is incredibly stretched out, or eccentric, a measure of how circular a planet’s orbit is. The eccentricity of a planet is measured on a scale from 0 to 1.

The newly discovered exoplanet has an unusually high eccentricity of 0.94. This indicates that it has the most stretched-out orbit of any exoplanet detected so far using the transit technique.

Imagine this oddball in our Solar System. With this eccentricity, at its closest point, it would be a highly scorching world, ten times closer to the Sun than Mercury. This super close distance would allow titanium to melt easily. Then, it would swing outwards to Earth’s distance, where temperatures would be considerably milder.

On top of that, this bizarre world orbits in the reverse direction of its star.

“The direction of the orbit tells us a lot about the history of the planet — that is, something must have happened to make the orbit backward in the first place — but it actually shouldn’t have any major impact on the future,” Arvind Gupta, NOIRLab postdoctoral researcher, and lead author told Interesting Engineering (IE). The findings were published in the journal Nature.

Migration of hot Jupiters

For years, astronomers have been puzzled by a class of giant planets called hot Jupiters. These monsters are similar to our Jupiter, but they orbit incredibly close to their stars.

As per the press release , how they end up in such close orbits has remained a long mystery. The study authors emphasize that this discovery sheds light on the pre-migration phase of hot Jupiters.

This high eccentric orbit might be a temporary phase. Scientists believe this giant planet is on its way to becoming a blazing-hot Jupiter. Tidal forces from the star will ultimately draw it in, resulting in a more circular orbit. Interestingly, this is just the second time a planet has been observed in its early phases before migrating.

“This discovery reinforces the high-eccentricity migration channel as a viable pathway for hot Jupiter formation. Giant planets can be excited onto highly eccentric orbits by a variety of processes, but we have rarely found any that are eccentric enough to then migrate inward and become hot Jupiters,” explained Gupta.

The James Webb Space Telescope (JWST) is expected to help researchers learn more about this exoplanet’s atmosphere. “I would really like to study how the atmosphere heats up as the planet rapidly approaches the star. This type of heating only occurs for exoplanets on highly eccentric orbits, and it is difficult to observe for almost all other exoplanet systems,” Gupta told IE.

But peeking into this planet’s fiery atmosphere might take some years due to the telescope’s jam-packed schedule.