Exoplanet Discoveries and Updates

[AstroChara]

Same thing as above for Barnard's Star b, turning out to be an alias of the star's 145 day rotation period.

[AstroChara]

Today a rather big paper dropped. The paper lists a number of planets, as well as making its own discoveries and determining false positives.

Most notable of them are a new, potentially Neptune or Saturn-like planet at Lalande 21185, and the confirmation of one planet around Lambda Serpentis and 14 Herculis each.

Lalande 21185 c
Semi-major axis: 3.1 AU
Orbital period: 8.73 years
Eccentricity: 0.14
Minimum mass: 18.0 Earth masses

Lambda Serpentis b
Semi-major axis: 0.1238 AU
Orbital period: 15.5083 days
Eccentricity: 0.16
Minimum mass: 13.6 Earth masses

Several planets have been determined as false positives, including 61 Virginis d, known in Orion's Arm as Iolus. That planet was kind of in the way of Eostremonath, so this might be a good news if it means we can replace it with a smaller planet with more circular orbit.

[sandcastles]

https://www.sciencenews.org/article/tiny...-iron-star
A newly discovered exoplanet is really making astronomers prove their mettle.

GJ 367 is a red dwarf 31 light years away in Vela.

The exoplanet was first spotted in data from NASA’s TESS telescope in 2019.

Period 7.7 hours


Diameter .72 Earth, 9184 kms., 5707 miles.

Mass .55 Earth    3.2841e24 kg.

Irradiation 500 times Earth

Temperature 1,500 Celsius, 2,732 Fahrenheit

Density 8.1 g/cc
86 percent of it could comprise an iron core, with only a sliver of rock left on top.

Is there enough information here to include it in the EG?

[stevebowers]

Sure, there should be. I doubt that a planet this small could retain much of an atmosphere, unless it were silicate or metal vapour of some sort. A tricky place for colonisation, although a tidally-locked world would be somewhat cooler on the dark side. Perhaps it would be better disassembled to create megastructures at a cooler distance.

[Drashner1]

Sure, there should be. I doubt that a planet this small could retain much of an atmosphere, unless it were silicate or metal vapour of some sort. A tricky place for colonisation, although a tidally-locked world would be somewhat cooler on the dark side. Perhaps it would be better disassembled to create megastructures at a cooler distance.

As an intermediate step, it might be doable to set up automated resource extraction systems (possibly just on the dark side depending on how intense local conditions are) that launch payloads out to a habitat(s) orbiting at some more comfortable distance.

This is basically planetary disassembly, just slower.

Todd

[AstroChara]

Today a new paper that described a nearby star TZ Arietis came out. The paper finds a Saturn-massed planet in a wide, eccentric, and possibly misaligned orbit. This suggest that the star system went through planet-planet scattering. For a star with only 0.15 solar masses, it's certainly an unusual find.

The other two planets found by a previous paper were discredited.

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TZ Arietis b
Semi-major axis: 0.88 AU
Orbital period: 771.36 days
Eccentricity: 0.46
Minimum mass: 0.21 Jupiter masses

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[stevebowers]

A variable star, I see. Flares and probably sunspots. Could it have another, closer planet as well?

[AstroChara]

A variable star, I see. Flares and probably sunspots. Could it have another, closer planet as well?

Not sure, but the paper suggests the other two planets aren’t real. It certainly could have some in real life I suppose? It seems to be miniaturized but otherwise analogous to, say Pi Mensae (with three planets, one of which is an eccentric jovian and two much smaller) or Titawin (with three planets, two of which are misaligned scattered jovians and another one being a hot jovian probably brought in by aforementioned scattering).

[AstroChara]

Among the stars mentioned in this new paper is 51 Ophiuchi, known in Orion's Arm as Gearhead. Apparently, the system's disk was not detected, but the presence of the brown dwarf companion was confirmed.

HD 158643 B
Separation = 0.118 ± 0.013 arcsecond = 14.8 +- 1.6 AU
Mass = 0.07 +0.01 -0.02 Sol

I also tried to revise the architecture of the star system but it was hell, so I'll just drop this panel and leave the rest to whoever's in charge of the article...

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Gearhead (51 Ophiuchi)

System
Location:
- Distance from Sol: 410.1 ly (J2000)
- Constellation: Ophiuchus

Star
Names: Gearhead, c Ophiuchi, 51 Ophiuchi, HD 158643, HIP 85755, HR 6519
Physical characteristics:
- Mass: 3.348 x Sol
- Radius: 8.08 x Sol (equator), 5.66 x Sol (pole)
- Oblateness: 0.300
- Temperature: 9,800 Kelvin
- Luminosity: 178 x Sol (bolometric)
- Spectral type: B9.5 IIIe
- Rotation period: 1.51 days
- Age: 1.22 million years

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[stevebowers]

Curious that they failed to find the dust disk, since this paper published in April 2020 discusses the spectrographic composition of the disk.
https://arxiv.org/abs/2004.10238

We found that most of the gas is situated at about 6AU from the star, has an electron volume density 10^5 <n(e) <3×10^6cm^3, and a temperature T=8000K. Our interpretations reveal that the gas is partly ionized, has a column density of neutral hydrogen equal to 10^21cm^2, and has a composition similar to that of a mildly depleted interstellar medium or that of Jupiter-family comets. Compared to results for disks around some other stars, such as β Pic and 49 Cet, we find surprisingly little neutral carbon. No molecular features were detected, which indicates that our line of sight misses the molecule-rich central plane of the disk. The tilt of the disk is also validated by our being able to detect resonant scattering of the starlight by oxygen atoms.

Perhaps it is just a depleted disk rather than the dense disk depicted in the article (which was based on the 2009 Keck observations).