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Alpha Centauri Bb is an exoplanet orbiting Alpha Centauri B. It is asserted that given the close distance to the star the planet should be tidally locked.

The orbiting period of the planet is about 3.2 days.

If the planet has no atmosphere (which is very possible due to proximity to the star), its dark side should experience low temperatures like permanently-shadowed areas of Mercury do.

At the same time the planet is about 11 AU from the other star, Alpha Centauri A.

This possibly means that the planet should experience quasi-day/night cycle each 3.2 days.

My questions are:

  1. To what temperatures the dark surface of such planet could be heated? Is there possibility of liquid water?

  2. Will the radiation of the second star be enough to provide normal day-like illumination and heating?

  3. Will the calendar on such a planet differ sufficiently from a calendar of a planet that experiences day/night cycles from the nearest star?

  4. Will such planet experience seasons and how they would be arranged?

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This is just a partial answer (so far), but it will address at least part of your question.

1.To what temperatures the dark surface of such planet could be heated? Is there possibility of liquid water?

Wikipedia gives a good estimate for this: 1,200 degrees Celsius. For a planet, that's pretty hot! Any water there would evaporate very quickly. In fact, it is expected that a lot of the planet's surface is molten. Now, does this apply to the back side of the planet? I would think so. While only the front side of the planet would bask in the warmth of Alpha Centauri B, the heat should dissipate throughout the entire planet.

2.Will the radiation of the second star be enough to provide normal day-like illumination and heating?

The short answer here is no. In fact, when compared to our solar system, nothing about the radiation Alpha Centauri Bb gets is normal. It is situated extremely close to Alpha Centauri B - 0.04 AU. Given that both Alpha Centauri A and Alpha Centauri B are similar to the Sun, I think it's clear that this exoplanet will not receive a "normal" (normal here meaning similar to Earth) amount of radiation from Alpha Centauri B. Conversely, Alpha Centauri Bb is 11 AU away from Alpha Centauri A - much greater than the distance between it and Alpha Centauri B (a bit more than the distance between Saturn and the Sun). This means that the planet will receive only a tiny fraction of light from Alpha Centauri A relative to Alpha Centauri B.

4.Will such planet experience seasons and how they would be arranged?

Seasons depend on the tilt of a planet's axis. Unfortunately, it is hard (if not impossible) to measure the tilt of the axis of Alpha Centauri Bb (I haven't been able to find any measurements). I would assume that it would experience some seasons, but I don't know how much they would extend.

As for question 3 - I'm not quite sure what you mean by "calendar." If you mean an artificial calendar, I would think that any beings on the planet (life there is extremely unlikely) would only use Alpha Centauri B to determine their years (just over three days and five hours).

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  • $\begingroup$ I think your answer assumes the planet to have a thick atmosphere? $\endgroup$ – Anixx Oct 10 '14 at 1:42
  • $\begingroup$ @Anixx What do you mean? $\endgroup$ – HDE 226868 Oct 10 '14 at 1:44
  • $\begingroup$ "Now, does this apply to the back side of the planet? I would think so." - how this can be the case if there is no atmosphere? And how the atmosphere can persist if at least part of a planet has temperature 2500K? I think the warm-side temperature guarantees no atmosphere and no atmosphere guaranteed freezing cold on the dark side (unless the other star is involved). $\endgroup$ – Anixx Oct 10 '14 at 8:28
  • $\begingroup$ @Anixx The planet is largely molten. Heat can be transferred as the molten material from the front of the planet moves around. $\endgroup$ – HDE 226868 Oct 10 '14 at 14:55
  • $\begingroup$ do you mean its darker side is also molten? $\endgroup$ – Anixx Oct 10 '14 at 14:58

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