Astronomers discover new Jupiter-like exoplanet

Astronomers discover new Jupiter-like exoplanet

Phase-folded best-fit orbital solution of HD 167768. Source: Teng et al., 2022.

Using radial velocity measurements, astronomers from Japan and China have discovered a new exoplanet orbiting a giant G-type star. The newly discovered extraterrestrial world is similar in mass to Jupiter but much hotter than the solar system’s largest planet. The discovery is reported in an article published on November 12 on the pre-print server arXiv.

The radial velocity (RV) method of detecting an exoplanet is based on detecting variations in the velocity of the host star due to the changing direction of an invisible exoplanet’s gravitational pull as it orbits the star. Thanks to this technique, more than 600 exoplanets have been discovered so far.

Now a group of astronomers led by Huan-Yu Teng of the Tokyo Institute of Technology in Tokyo, Japan, reports the discovery of a new giant planet as a result of RV measurements with the HIgh Dispersion Echelle Spectrograph (HIDES) at the Okayama Astrophysical Observatory ( OAO) in Japan. The planet orbits a deeply evolved solar-mass G-type giant star known as HD 167768, located about 353 light-years away.

‘For HD 167768 RVs we could find a strong signal at 20 d, indicating a regular variation in the time series,’ the researchers explain.

The newly discovered exoplanet, designated HD 167768 b, is estimated to have a mass of at least 0.85 masses of Jupiter. It orbits its host every 20.65 days at a distance of about 0.15 AU. The equilibrium temperature of this planet has been calculated to be 1.874 K.

Due to its parameters, the authors of the paper classified HD 167768 b as “warm Jupiter”. The planet has been found to have one of the shortest orbital periods ever found around deeply evolved stars using radial velocity methods.

Estimated to be 5.3 billion years old, the host star HD 167768 belongs to the spectral type G8 III, has a mass of about 1.08 solar masses and is almost ten times larger than the Sun. It has an effective temperature of 4,851 K and its metallicity is -0.75.

As HD 167768 is expected to climb the red giant branch, astronomers predict that its planet will be astronomically swallowed up in a relatively short time. By analyzing the orbital evolution, they estimate that HD 167768 b will be engulfed by the expanding star within about 150 million years.

The researchers also assume that at least two other planets in the system HD 167768 could still be undiscovered. This assumption is based on the two additional regular variations identified in the RV measurements.

“In the periodogram of the residuals there are two additional signals at 41 d and 95 d with FAP [false alarm probability] a little under 0.1 percent, which indicates possible additional companions in the system,” the scientists note.

More information:
Huan-Yu Teng et al, A Close-in Planet Orbiting Giant Star HD 167768, arXiv (2022). DOI: 10.48550/arxiv.2211.06576

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