An article published in “The Astronomical Journal” reports confirmation of the existence of the exoplanet HD 63433d, a rocky planet with a size close to the Earth’s that orbits a star very similar to the Sun in a system that was already known. A team of researchers led by Melinda Soares-Furtado of the University of Wisconsin-Madison and Benjamin Capistrant, now a student at the University of Florida, used data collected by NASA’s TESS space telescope to identify HD 63433d within the THYME (TESS Hunt for Young and Maturing Exoplanets) survey. Its close proximity to its star probably makes it a so-called lava planet since on the dayside, the temperature on its surface is estimated at over 1,500° Kelvin.
Just over 70 light-years away from Earth, the HD 63433 star system has already been studied over the years, and in 2020, the existence of two exoplanets, two mini-Neptunes, was already confirmed. The one cataloged as HD 63433c was interesting because it’s losing its atmosphere. Research continued, also within the THYME survey, whose main aim is to identify young exoplanets in groups of stars of various types. The star is very similar to the Sun but far younger given that it has an age estimated at “only” 400 million years.
The exoplanet HD 63433d is very close to its star with a year estimated to be around 4.2 Earth days, making it difficult to identify. Astronomers believe it’s tidally locked to its star, always showing the same face, just like the Moon does with the Earth. For this reason, its dayside is perpetually hit by emissions from its star, which bring its surface temperature to levels estimated at over 1,500° Kelvin. The consequence is that the dayside is probably covered in lava, which is why it’s one of the brightest planets detected via its transits in front of its star from the perspective of the TESS space telescope.
Due to its characteristics, the transits of the exoplanet HD 63433d were barely detected and it was more necessary than ever to eliminate the risk of a false positive in the detections. Follow-up examinations of data collected by TESS and data collected with other instruments confirmed the existence of HD 63433d.
The transits of the exoplanet HD 63433d allowed to estimate that its size is slightly larger than the Earth’s but that’s the only similarity. Hit by stellar wind, if it initially had an atmosphere, it was probably blown away. However, we still know little about atmospheric loss processes, so HD 63433d could be an interesting object of study from this point of view just like HD 63433c.
The TESS space telescope conducted new observations of the HD 63433 system that need to be analyzed. They could be useful for obtaining more precise information on the known planets and for verifying the possibility that there are others that had escaped the analyzes conducted so far. Given its young age in astronomical terms, it’s also interesting in studies of the evolution of young planets.
The position of the HD 63433 system makes it visible from both the Northern and Southern Hemispheres, so it can be studied with many ground-based telescopes. It’s in the cosmic neighborhood and this further increases its potential as an object of observation with the James Webb Space Telescope, which could among other things offer information on whether or not there’s an atmosphere on the exoplanet HD 63433d.
