KOI 5715.01

[pzmcgwire]

Just saw an article about this superhabitable planet, KOI 5715.01, and wondering about its size, which is about 1.9x the radius of Earth, making it size classification F, 15, or larger. https://en.wikipedia.org/wiki/KOI-5715.01

This planet couldn't be randomly generated through CT world generation and could through GM fiat.

Classic Traveller planet generation is 2D-2, which has a maximum planetary diameter for the main world of size 10.

Has our knowledge of potential exoplanets changed since Traveller was originally published so that larger worlds are probable or even more likely now?

 

[AnotherDilbert]

Just saw an article about this superhabitable planet, KOI 5715.01, and wondering about its size, which is about 1.9x the radius of Earth, making it size classification F, 15, or larger. https://en.wikipedia.org/wiki/KOI-5715.01

Potentially "superhabitable" to life, not necessarily Earth life.

Surface gravity would presumably rule it out for human habitation?

 

[Grav_Moped]

Potentially "superhabitable" to life, not necessarily Earth life.

Surface gravity would presumably rule it out for human habitation?

In general, yes. At or above TL-8 with gravitics, it'd be possible -- though perhaps not entirely practical.

 

[Rupert]

Potentially "superhabitable" to life, not necessarily Earth life.

Surface gravity would presumably rule it out for human habitation?

That would depends on its density, but yes, it's likely that the surface gravity would be too high for real-life humans to live on long-term. SF humans, OTOH, often live and even thrive on worlds with 2G+ gravity, so they'd be okay on this world.

 

[Dragoner]

Just saw an article about this superhabitable planet, KOI 5715.01, and wondering about its size, which is about 1.9x the radius of Earth, making it size classification F, 15, or larger. https://en.wikipedia.org/wiki/KOI-5715.01

This planet couldn't be randomly generated through CT world generation and could through GM fiat.

Classic Traveller planet generation is 2D-2, which has a maximum planetary diameter for the main world of size 10.

Has our knowledge of potential exoplanets changed since Traveller was originally published so that larger worlds are probable or even more likely now?

At it's distance, it is difficult to say. Though I have done a lot of translating of real exoplanets into Traveller stats in Solis People of the Sun. Running the data from NASA through astrosynthesis it is 1.9g (assuming Earth density), 12°C equatorial, marginal. One could have too many variables that could change things one way or another.

Maps:




The brown-orange color is a close enough match for vegetation under a K3V star from this site:

Colors of Alien Plants

 

[kilemall]

At it's distance, it is difficult to say. Though I have done a lot of translating of real exoplanets into Traveller stats in Solis People of the Sun. Running the data from NASA through astrosynthesis it is 1.9g (assuming Earth density), 12°C equatorial, marginal. One could have too many variables that could change things one way or another.

Maps:

View attachment 6020

View attachment 6021
The brown-orange color is a close enough match for vegetation under a K3V star from this site:

Colors of Alien Plants

Oh yay tytyty! I’ve been wanting a site explaining what color plants will have.

A lot of planets will have less atmosphere pressure, so will have to shift the other way for those.

 

[Dragoner]

Oh yay tytyty! I’ve been wanting a site explaining what color plants will have.

A lot of planets will have less atmosphere pressure, so will have to shift the other way for those.

Yes, I used that a lot in my books for vegetation colors.

 

[kilemall]

Hmm also occurs to me atmospheric composition would also affect what wavelengths would punch through to affect coloration.

For animals many would have similar colors for same excess energy/damage mitigation. But on low energy environments like red dwarfs exothermics might evolve colors that capture more energy. Probably more endothermic development though.

 

[atpollard]

Running the data from NASA through astrosynthesis it is 1.9g (assuming Earth density)

I have a vague recollection that Earth Density is a bad assumption. I seem to recall that Earth has a “double sized” core (increasing the average density and gravity) with the extra mantle flung into space to create a really large (low density and gravity) moon.

A quick Google search indicates the density of Earth is 5.5 g/cu.m. compared to Mars at 3.9 g/cu.m. and Europa at 3.0 g/cu.m.

So a Mars like density might reduce the 1.9g to 1.35g

 

[Rupert]

Part of Earth's higher density is from compression due to its larger size and mass, so a planet 1.9 times the diameter of Earth will have a higher density for the same composition.

Also, Venus has a density of 5.243 Tonnes/m3, suggesting that most or all of Earth's high density is not especially anomalous. One factor that might indicate the density of extra-solar planets is the metallicity of their star - the higher it is, the more heavy elements would be available, and the higher the likely density of any will be.

 

[Dragoner]

Yes, I was going to mention the star's metallicity has a lot to do with density. I ran typical numbers just to see, otherwise, there are too many variables that could change things.

 

[Spinward Flow]

suggesting that most or all of Earth's high density is not especially anomalous.

If there's one thing we've learned from surveys of exoplanets, it's that the Solomani home solar system is WEIRD.
Like really ... really ... weird.

The similarities between the planets in our own solar system with the planets in other star systems basically "stop" after recognizing that other stars have planets too.

I mean ... we don't have inner orbit gas giants (evaporating away) in our home solar system, but they're almost common elsewhere ...?

 

[Dragoner]

Hmm also occurs to me atmospheric composition would also affect what wavelengths would punch through to affect coloration.

For animals many would have similar colors for same excess energy/damage mitigation. But on low energy environments like red dwarfs exothermics might evolve colors that capture more energy. Probably more endothermic development though.

Many of the m type stars we see are older pop II stars, low metallicity, and often flare stars; planets orbiting them will likely be tide locked, and in a very close orbit, less than 0.2 AU to have liquid water. Though their age probably means they will have had their atmosphere stripped, or simply sublimated.

 

[Rupert]

If there's one thing we've learned from surveys of exoplanets, it's that the Solomani home solar system is WEIRD.
Like really ... really ... weird.

The similarities between the planets in our own solar system with the planets in other star systems basically "stop" after recognizing that other stars have planets too.

I mean ... we don't have inner orbit gas giants (evaporating away) in our home solar system, but they're almost common elsewhere ...?

Bear in mind that close gas giants and super-earths are comparatively easy to find, especially around small stars. Distant gas giants and 'normal' earths around relatively large stars (i.e. not red dwarfs) are much harder to find. Thus there's a bias in our current dataset, and we just don't know how much is because normal earths are rare and how much is because of this bias.

 

[aramis]

The current detection methods strongly select for larger planets and smaller stars.
Occultation method: the amount of dimming indicates the fraction of the face covered, allowing determining orbital period, diameter, and atmospheric composition. Note that the atmospheric composition is not considered highly reliable, most is 3σ or lower.
Stellar Motion method: The barycenter needs to be near or above stellar surface to be notable; the actual motion creates cyclic red-shift and blue-shift around the "at rest" spectrum.

For occultation:

• the bigger the planet, the stronger the signal difference, as it covers more of the solar disk
• the smaller the star, the stronger the signal difference, as there's less space to block
• only works when view angle is near the orbital plane
• Problem: Smaller stars are less bright to begin with, so a lower total luminosity difference can be present in smaller stars than in larger ones, even tho' it's a higher proportion; this can lead to

For Stellar motion:

• The smaller the star, the more motion for a given mass planet
• the bigger the planet, the more motion for a given mass star.
• the closer the two, the more significant the motion
• the closer to the plane of the planetary orbit the view angle is, the more significant the motion will be (due to inverse square).

Also worth noting - many sites are not up to date with the catalogs' used color indicators. The main sequence temperature based "colors" now run OBAFGKMLTY; there are also a bunch of special ones other than those. Also the scale has added a second digit to the color; best practice is to the 0.5, but some have used 0.1 increments.

Have an overlydeep look at the history of stellar spectral classification:

https://www.researchgate.net/publication/384812125_Spectral_classification