TOI-1227 b

TOI-1227 b is one of the youngest transiting exoplanets discovered (as of September 2022), alongside K2-33b and HIP 67522 b. The exoplanet TOI-1227 b is about $0.854$ million years old and currently large. It will become a planet in about 1 billion years, because the planet is still contracting. TOI-1227 b orbits its host star every 27.36 days.

Characteristics
TOI-1227 b has a size that is 85% that of Jupiter, or 9.6 times that of Earth. No other Jupiter-sized planet was detected around mid- to late M-dwarfs, despite the deep transits such a planet would create. The researchers find that the planet is still hot from its formation and this heat, combined with a hydrogen-dominated primary atmosphere makes the atmosphere of TOI-1227 b inflated. Evolutionary models suggest that TOI-1227 b will eventually evolve into a sub-Neptune within the next billion years.

Future research
Radial velocity follow-up to determine the mass of TOI-1227 b is not possible in the optical, but might be possible in the near-infrared. A less challenging follow-up would be the measurement of the Spin-Orbit-Alignment via the Rossiter–McLaughlin effect.

Host star
TOI-1227 was first identified as a pre-main-sequence star (PMS star) with the Gaia satellite. Without this prior identification as a PMS star the exoplanet signal of TOI-1227 b would have been disregarded as an eclipsing binary due to the V-shape of the transit signal.

The star is located north of the globular cluster NGC 4372, but it is much closer to earth than this cluster of stars, at a distance of about 101 pc. NGC 4372 is 5800 pc away.

The host star TOI-1227 is part of a subgroup of the Lower Centaurus Crux OB association, sometimes called B, A0 and called Musca group by the scientists that discovered TOI-1227 b. This group was called Musca after the constellation Musca in which most of its members are located.

TOI-1227 has a spectral type of M4.5V to M5V, a mass 17% of the Sun and a radius 56% of the Sun. The host star is relative faint for a TOI with a visual magnitude of about 17. The right ascension of 12:27:4.31 and the declination -72°27′6.5″ implies that it is located in the Musca constellation. The host star shows Lithium in its atmosphere, which should be depleted within 10-200 million years for M-dwarfs.