Star A

Mass: 1.2 x Sol

Radius: 1.157 x Sol

Luminosity: 2.074 x Sol

Temperature: 6,444 K

Star B

Mass: 0.63 x Sol

Radius 0.691 x Sol

Luminosity: 0.158 x Sol

Temperature: 4,378 K

Semi-Major Axis: 852.1 au

Eccentricity: 0.1259

Apoapsis: 959.38 au

Periapsis: 744.82 au

Period: 22721.53 years


Mass: 0.64 x Earth

Radius: 0.87 x Earth

Gravity: 0.85 x Earth

Rotation: 30 Hours

Tilt: 19.25°

Semi-Major Axis: 1.5 au (Star A)

Eccentricity: 0.0159



Period: 1 year, 247 days.

Local Year: 490.076 days.

Water: 81%

Atmospheric Pressure: 234.061 kPa

Atmospheric Composition:

N2: 87.34% O2: 11.52% Ar: 1.02% CO2: 0.06% H2O (water vapor): 0.04% CH4: 0.00020%

Average Temp: 11° C (probably underestimated or overestimated the increased greenhouse gas, but I'm going with it unless someone points out just how off this is.)


Mass: 2.84 x Luna

Radius: 1.43 x Luna

Semi-Major Axis: 213,845 km

Eccentricity: 0.0450

Apoapsis: 223,468 km

Periapsis: 204,222 km

Period: 13 days, 20 hours

Based on this information, could humans live on this planet without genetic modifications or being in a space suit all the time? How difficult would it be to grow Earth-based crops?

  • $\begingroup$ Such a low oxygen percentage might prove problematic. $\endgroup$
    – Hyfnae
    Jun 11, 2017 at 18:43
  • $\begingroup$ People could use oxygen masks and they actually get used to low oxygen level like they do on Everest. $\endgroup$
    – keiv.fly
    Jun 11, 2017 at 20:11
  • 2
    $\begingroup$ @Hyfnae: Look at the pressure. The proposed planet has 2.3 atm pressure (presumably at sea level); with 12% oxygen the partial pressure of oxygen is actually higher than on Earth. There is also a lot more carbon dioxide than on Earth. $\endgroup$
    – AlexP
    Jun 11, 2017 at 20:29
  • $\begingroup$ I'm looking for the science-based or hard-science tag :P This might generate more precise and researched answers in the Space Exploration/Physics Community. Especially in the first one. But that's just a guess/opinion $\endgroup$ Jun 12, 2017 at 8:43
  • $\begingroup$ star temperature is at surface or core? Our sun is about 1k suface and 10k core temperatures. The smaller star seems to be at the edge of the solar system, which is physicaly very weird (could be the feeling you are going for). $\endgroup$
    – ivbc
    Jun 12, 2017 at 15:11

2 Answers 2


As user @Hyfnae indicated in comments the low oxygen content is a problem. This short article explains why. Basically you need something between 19% and 23.5% for safety. You could probably dip to 16% if your colony spends most of it's time in sealed habitats or uses breathing apparatus normally.

Atmospheric pressure at over twice Earth-average would seem a problem. I'm out of my depth here (no pun intended) but this is equivalent to I think being submerged at about 30 feet. Humans can do that for a while, but you're talking about living at that permanently.

I'm also not sure what effect this has on how much oxygen content you need (increased pressure may compensate for the lack of oxygen). There's also the inert gas content, as I seem to recall there's a narcotic effect from inert gas use in diving (you really need to investigate aspects of diving and living in pressurized conditions to find out more).

There's also the length of day. Human biofunctions are regulated by a thing called the Circadian rhythm. Now the normal day-light lighting cycle and the level of lighting both affect your body because it gets out of whack with the "designed-in" 24 hour cycle it expects. I'd be very surprised if anyone trying to live in a 30hr day would be able to - your body clock will be out of sync with the environment. If they try and live inside an artificially lit habitat that might work, but anything else would be like doing shift work that constantly changes the hours of work - it would quickly disrupt your sleep pattern (at a minimum) and you'd cease to function effectively. You'd become clinically depressed.

So as it stands this planet could be colonized only by people living in closed habitats with life support (oxygen) and a completely artificial lighting system that mimicked the normal 24 hour day-night cycle.

Note that even with this, if they needed to work outside for long periods they'd require not only life support (oxygen) but they would likely start to suffer depressive symptoms as their body clocks (24 hr cycle) would be out of sync with the planet's environment (30 hr cycle).

  • 2
    $\begingroup$ Look at the pressure. The proposed planet has 2.3 atm pressure (presumably at sea level); with 12% oxygen the partial pressure of oxygen is actually higher than on Earth. There is also much more carbon dioxide than on Earth. $\endgroup$
    – AlexP
    Jun 11, 2017 at 20:29
  • $\begingroup$ As others have said, the lower oxygen percentage is to compensate for the increased atmospheric pressure. Even as is, the partial pressure is much higher than Earth. Also, the increased CO2 is to compensate for the planet being a little too far from its star; with the same amount of greenhouse gas levels as Earth, it would freeze. $\endgroup$ Jun 11, 2017 at 20:48
  • $\begingroup$ Accepting this, there remains the issue of whether sustained (permanent) living in a high pressure is viable. Also consider (for the purposes of your scenario) the effect of this high pressure or enclosed living on visiting space ship crews. $\endgroup$ Jun 11, 2017 at 20:58
  • $\begingroup$ So far as I can tell 2.3 x Earth's atmosphere is about the same as diving 13 meters. So far I can't find anything on exactly how tolerable that would be. $\endgroup$ Jun 11, 2017 at 22:40

As stated in another answer by StephenG the day length is a challenge but I would personally disagree that the circadian rhythm is the major concern. Humans can adapt to different sleeping schedules. It would be a problem for newcomers at first because orbital period is different, but the biological clock doesn't split hours of the day as discrete values as we do when we think of time, it just does its job in setting up a rhythm for activity and a period of rest.

My concern would be more of the tilt of the planet being less than that of Earth, further increasing the average daylight time on the 30 hour rotational period.

You also have two stars, increasing the point sources of light shining on the planet, further increasing daylight time.

You have a satellite with greater size than the Moon at a similar orbit if not closer. Which will also reflect light from both stars depending on its composition, so nights will be brighter.

The stars' combined luminosity is much higher than that of our Sun.

Greater green house gas presence.

Adding to all this your note on the average temperature....

What I'm trying to get at is that even at 1.5 AU, the amount of light possibly entering the planet is far greater than that of our Earth, you might actually have a really hot planet.

The higher water surface coverage also doesn't help, water absorbs the heat from the day to keep the planet warm at night, further increasing the average temperature.

A more massive satellite also means greater tide differences at half the period of our Moon.

I guess after looking up online about Gamma Leporis, the distance is about right for liquid water and a comfortable planet, but all these other factors might just make your planet really hot and probably stormy and aggressive for any permanent residence. Also I'm not sure if the calculation was done considering a binary star system, or if the star was on its own.

Depending on your orbits of star B and said planet, you may also have situations where the planet is ~.8 AU away from the 2nd star, which might still seem far from its comfortable orbit around star B as any page on these stars states. But you still have light from star A heating the planet, so you might have periodic mass extinction due to abnormally hot weather.

I don't doubt people can find a way to live on this planet if they have to, but the solution probably involves taking advantage of the life which may exists on this planet for food. The environment needed for Earth-based crops is just too vastly different and expensive to maintain on such a planet which is already taxing for maintaining a livable space for unmodified humans.

Even if you start with Earth based crops, they may evolve overtime as only those members of the crop which have a gene ideal for survival on this planet will proliferate, the rest will just die out. Indoor farming might be out of the question if it's just too expensive to maintain the internal environment.

All this also does not involve dealing with solar activity and surviving solar flares in a system which may or may not have a Jupiter-like big brother blocking out radiation from such events. This will also effect the technology available to people outside of pre-built safe zones.

Anyway, that's my thought on the matter.

  • $\begingroup$ However, a mean temperature of 11 C puts the planet in an ice age, which may cause the settlers problems. $\endgroup$ Jun 22, 2017 at 0:21
  • $\begingroup$ That was also put with a comment that it may or may not be true. $\endgroup$
    – V. Sim
    Jun 22, 2017 at 20:03
  • $\begingroup$ I mean star B is ridiculously far away so it doesn't affect brightness on the surface really. The habitable zone is prop to the sqrt of the luminosity of Star A, so it checks out. The higher CO2 however may mean the planet should be more like 1.6 AU instead of 1.5 AU. Sorry for necroposting $\endgroup$
    – majestas32
    Sep 22, 2018 at 23:21

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .