Using radial velocity measurements, astronomers from Japan and China have detected a new exoplanet orbiting a giant G-type star. The new alien world is similar in mass to Jupiter but much hotter than the largest planet in the solar system . The discovery is reported in a paper posted Nov. 12 on the arXiv preprint server.
The radial velocity (RV) method for detecting an exoplanet relies on detecting changes in the velocity of the central star due to the change in direction of the gravitational pull of an invisible exoplanet as it orbits the star. Thanks to this technique, more than 600 exoplanets have been detected so far.
Now, a group of astronomers led by Huan-Yu Teng of the Tokyo Institute of Technology in Tokyo, Japan, report the discovery of a new giant planet as a result of RV measurements using the High Dispersion Echelle Spectrograph (HIDES) at the observatory. astrophysicist of Okayama (OAO) in Japan. The planet orbits a deeply evolved solar-mass giant G-type star known as HD 167768, located about 353 light-years away.
“For HD 167768 RV, we could find a strong signal at 20 days, indicating smooth variation in the time series,” the researchers explain.
The newly detected exoplanet, designated HD 167768 b, is estimated to have a mass of at least 0.85 Jupiter masses. 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 at 1,874 K.
Due to its parameters, the authors of the article classified HD 167768 b as a “hot Jupiter”. The planet turned out to have one of the shortest orbital periods ever found around deeply evolved stars using radial velocity methods.
The host star HD 167768, estimated to be 5.3 billion years old, is of spectral type G8 III, has a mass of about 1.08 solar masses, and is nearly 10 times the size of the sun. It has an effective temperature of 4,851 K and its metallicity is at a level of -0.75.
Given that HD 167768 is expected to ascend the red giant branch, astronomers predict that its planet will be engulfed in a relatively short time in astronomical terms. Analyzing orbital evolution, they estimate that HD 167768 b will be engulfed by the expanding star within about 150 million years.
The researchers also hypothesize that at least two other, yet undetected, planets may be present in the HD 167768 system. This assumption is based on the two additional regular variations identified in the RV measurements.
“In the residual periodogram, there are two additional signals at 41 of 95 d with FAP [false alarm probability] slightly less than 0.1%, suggesting possible extra companions in the system,” the scientists note.
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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