Pi Men - a transiting super-Earth and a non-coplanar eccentric super-Jovian

TESS's first planet discovery!!

TESS Discovery of a Transiting Super-Earth in the Π Mensae System
https://arxiv.org/abs/1809.05967

Quote :

We report the detection of a transiting planet around π Mensae (HD\,39091), using data from the Transiting Exoplanet Survey Satellite (TESS). The solar-type host star is unusually bright (V=5.7) and was already known to host a Jovian planet on a highly eccentric, 5.7-year orbit. The newly discovered planet has a size of 2.14± 0.04~R⊕ and an orbital period of 6.27 days. Radial-velocity data from the HARPS and AAT/UCLES archives also displays a 6.27-day periodicity, confirming the existence of the planet and leading to a mass determination of 4.82± 0.85~M⊕. The star's proximity and brightness will facilitate further investigations, such as atmospheric spectroscopy, asteroseismology, the Rossiter-McLaughlin effect, astrometry, and direct imaging.

Following the Kepler naming scheme for objects of interest, π Men c is also known as TOI-144.01, which in itself tells you they may have already at least 143 more transiting planet candidates already that are awaiting confirmation.

Also, on the potential detection of π Men b with Gaia, they note that it will take the full five year mission to achieve a detection of 10σ, but,

Quote :

Ranalli et al. (2018) predicted that the astrometric signal of π Men b will be detectable with a signal-to-noise ratio higher than 10 by the end of the mission. Indeed, the fit to the existing Gaia data exhibits an excess scatter of 295 µ" (37σ), perhaps a hint of planet-induced motion

Notable discovery. Certainly there's much more to reveal...

Same planet but another team :

TESS's first planet : a super-Earth transiting the naked-eye star π Mensae

https://arxiv.org/abs/1809.07573

page 1 :

"...Following a successful commissioning of 3 months, TESS
started the science operation on 25 July 2018 by photometrically
monitoring its first sector (Sector 1), which is centered
at coordinates  = 352.68,  = 􀀀64.85 (J2000). Shortly after
30 days of (almost) continuous observations in Sector 1, 73
transiting planet candidates were detected in the 2-min cadence
light curves by the TESS team and made available to the scientific
community through a dedicated web portal hosted at the
Massachusetts Institute of Technology (MIT) web page..."

Quite difference in planet radius in this paper 1.84 .Density suggests envelope but is it water or hydrogen ?`I did not expect any of them so close around G star

There does seem to be a bit of controversy going on with the early results, e.g. why the two papers about Pi Mensae c ended up with different planetary radii...

https://twitter.com/benmontet/status/1043222872834170881

Since this system is getting a bit of attention. I've split this from the TESS results thread.

Especially interesting, even if not terribly surprising, is a new result using Hipparcos+Gaia data to constrain the inclination of the b planet, finding it to be misaligned with the transiting planet. They also find similar results for HAT-P-11.

Evidence for a high mutual inclination between the cold Jupiter and transiting super Earth orbiting π Men
https://arxiv.org/abs/2007.01871

I like that they explain in detail the coordinate system used and the reason for the 180° offset in ω between their orbital elements and past papers. Useful information if you want to use the elements to represent the planets in 3D space simulator software...

Another paper on the subject, now with ESPRESSO radial velocities, and similar findings.

A precise architecture characterization of the π Men planetary system
https://arxiv.org/abs/2007.06410

Have you heard the news? The planets at π Men have a significant mutual inclination!

A significant mutual inclination between the planets within the π Mensae system
https://arxiv.org/abs/2007.08549

Not entirely surprising, but:

Orbital misalignment of the super-Earth π Men c with the spin of its star
https://arxiv.org/abs/2007.11564

A Heavy Molecular Weight Atmosphere for the Super-Earth π Men c
https://arxiv.org/abs/2102.00203

Quote :

Strongly irradiated exoplanets develop extended atmospheres that can be utilized to probe the deeper planet layers. This connection is particularly useful in the study of small exoplanets, whose bulk atmospheres are challenging to characterize directly. Here, we report the 3.4{\sigma} detection of C II ions during a single transit of the super-Earth {\pi} Men c in front of its Sun-like host star. The transit depth and Doppler velocities are consistent with the ions filling the planet's Roche lobe and moving preferentially away from the star, an indication that they are escaping the planet. We argue that {\pi} Men c possesses a thick atmosphere with abundant heavy volatiles (>= 50{\%} by mass of atmosphere) but that needs not be carbon rich. Our reasoning relies upon cumulative evidence from the reported C II detection, the nondetection of H I atoms in a past transit, modeling of the planet's interior, and the assumption that the atmosphere, having survived the most active phases of its Sun-like host star, will survive another 0.2-2 Gyr. Depending on the current mass of atmosphere, {\pi} Men c may still transition into a bare rocky core. Our findings confirm the hypothesized compositional diversity of small exoplanets, and represent a milestone toward understanding the planets' formation and evolution paths through the investigation of their extended atmospheres.