Exoplanet Discoveries and Updates

[AstroChara]

Today we have two interesting news. One is the direct imaging of TYC 8998-760-1, a young solar analog star with two planets, and another is the detection of transits of the known planets around the star Nu2 Lupi.

A star some three hundred light-years away, TYC 8998-760-1 was already known to host one planet, detected by direct imaging. The new image reveals the presence of its sibling planet, which is smaller and probably further away from the star than the first planet.

(LINK)

TYC 8998-760-1 b
Projected physical separation: 160 AU
Mass: 14 Jupiters

TYC 8998-760-1 c
Projected physical separation: 320 AU
Mass: 6 Jupiters
Radius: 1.1 Jupiters
Effective temperature: 1240 K

Closer to home we have Nu2 Lupi, which is colonized as NewRoot in Orion's Arm. The system has three known planets occupying mass ranges from 4-11 Earth masses. With the detection of transits of these planets, it is now possible to find both radii and true masses, the two keys to figuring out density and thus a rough but solid idea of what the planet is like. Combined with improved radial velocity data yields a vastly expanded view of the inner Nu2 Lupi system.

(LINK)

Nu2 Lupi b
Semi-major axis: 0.0969 AU
Orbital period: 11.57779 days
Eccentricity: 0.079
Inclination: 88.86 degrees
Mass: 4.62 Earths
Radius: 1.482 Earths
Equilibrium temperature: 911 K


Nu2 Lupi c
Semi-major axis: 0.1729 AU
Orbital period: 27.5909 days
Eccentricity: 0.037
Inclination: 88.658 degrees
Mass: 11.29 Earths
Radius: 2.608 Earths
Equilibrium temperature: 682 K

Nu2 Lupi d
Semi-major axis: 0.4285 AU
Orbital period: 107.63 days
Eccentricity: 0.075
Minimum mass: 10.5 Earths
Equilibrium temperature: 433.3 K

This measurement confirms that Nu2 Lupi b is a dense rocky planet, while Nu2 Lupi c is a gaseous planet. While its actual radius is not available, judging from its mass, Nu2 Lupi d is most likely to also be a Neptunian.
If Nu2 Lupi d is aligned with the other two planets, it wouldn't transit the star.

[stevebowers]

Yeah; Nu2 Lupi needs an update.


On another note, the big planet around TYC 8998-760-1 falls into the brown dwarf category, more-or-less. But it has probably stopped fusing, so it is more like a planet these days.

[AstroChara]

Yeah; Nu2 Lupi needs an update.


On another note, the big planet around TYC 8998-760-1 falls into the brown dwarf category, more-or-less. But it has probably stopped fusing, so it is more like a planet these days.

I can work on a Nu2 Lupi update. The article does state that Nu2 Lupi's inner planets (does say there are two though) are disassembled for use in the construction of the System Grid, but just how massive is the System Grid?

[QuantumJack1]

According to Wikipedia page Tau Ceti:

In a paper published in 2019 in Astronomy & Astrophysiscs, scientists analyzing radial velocity data found a regular, long-period spike. Said spike could be explained by a Jupiter-analog planet orbiting at around 5 AU. However, the planet could be as heavy as 5 Jupiter masses and orbit anywhere between 3 and 20 AU from its parent star.[68]

A mesojovian may exist at inner edge of debris disk at ~ 5AU. Will Zeus return?

[AstroChara]

According to Wikipedia page Tau Ceti:

In a paper published in 2019 in Astronomy & Astrophysiscs, scientists analyzing radial velocity data found a regular, long-period spike. Said spike could be explained by a Jupiter-analog planet orbiting at around 5 AU. However, the planet could be as heavy as 5 Jupiter masses and orbit anywhere between 3 and 20 AU from its parent star.[68]

A mesojovian may exist at inner edge of debris disk at ~ 5AU. Will Zeus return?

Interestingly enough, an earlier paper rules out any planet more massive than Neptune orbiting at 5 AU.

[AstroChara]

Yesterday an interesting paper dropped on ArXiv. It contains a boatload of companions, both stellar (and brown dwarf) and planetary. It contains huge walls of data, so I’ll grab a summary of new planets provided by a user on another Forums here:



I don’t know about the HD stars, but you might be able to recognize that 20 Leonis Minoris is Halcyon, and Lambda Serpentis is Orinoco’s system. Omicron2 Eridani A is Keid, by the way.

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20 Leonis Minoris b
Semi-major axis: 0.2003 AU
Orbital period: 31.15 days
Eccentricity: 0.2
Mass: 10 Earths
Irradiance: ~35 Earths

Lambda Serpentis b
Semi-major axis: 0.123611 AU
Orbital period: 15.508 days
Eccentricity: 0.2
Mass: 14 Earths
Irradiance: ~140 Earths

[stevebowers]

Omicron-2 Eridani Ab is in OA, as the planet Dawn; we may have to re-jig that system slightly, if the planet is confirmed as non-existent.

[AstroChara]

I skipped out a whole lot of exoplanet discoveries, but I figured this one is just too important to skip.

However it's really late in the night here, so I'll just post the link to the paper for you guys to read. Maybe will update this later.

https://www.nature.com/articles/s41467-021-21176-6

[stevebowers]

Max Stable orbit ~2.8 AU. Interesting.

[AstroChara]

The latest paper on Kapteyn's Star suggested that neither of its proposed planets (b, c) exist - instead both appeared to be artifacts of stellar rotation and activity. This work also reported the rotation period of Kapteyn's Star to be around 125 days.

Back in 2014 a team of researchers led by Anglada-Escudé announced the discovery of two exoplanets around this star, one located in the 'habitable zone' and has minimum mass low enough to have a shot of being rocky (although very unlikely given our current knowledge). The existence of this planet was challenged before in 2015, which apparently didn't sit well with the discoverers, so it seems there is an ongoing debate on whether these two planets exist or not. People in the Celestia discord (where I got the news from) said we could expect a response from Anglada-Escudé soon.

In Orion's Arm, the Kapteyn's Star system doesn't have its own article, but it is mentioned to had been home to the Andromeda Kids during the First Federation. Needless to say there are no mentions of these two planets, which seems like a good idea given things that are going on right now...