Gliese 581g: Newsletter Challenge (April 2016)

Maybe they want to fly back to Earth and landing somewhere else would cost more fuel when starting again!

That's where all the tourist destination parks are located....

Gliese 581g is believed to be tidally locked.

https://en.wikipedia.org/wiki/Gliese_581_g#Tidal_locking_and_habitability

Yep. Which is why I replied with rotational and/or orbital speed.

In that case, they might be as interested in longitude as latitude. The "sun" never sets on one side and never rises on the other. I would expect it would be hot on the sunny side, cold on the dark side and windy in between.

If the rotation period is the same as the year (32 days), the equatorial rotation speed would not be of much help.

https://en.wikipedia.org/wiki/Gliese_581_g

From the wiki article:

Because of Gliese 581 g's proximity to its parent star, it is predicted to be tidally locked to Gliese 581.

In other words, it hasn't been observed to be tidally locked to its parent star. Keep in mind for a long time they thought the planet Mercury was tidally locked with the Sun and it turned out it wasn't, so "predicted" doesn't really mean anything in the context of this question IMO.

I'm sure that's the answer they're looking for. In practice, the rotational speed of the planet would amount to a miniscule energy savings compared to the energy required for interstellar flight. The orbital motion of the planet would be much larger. (For example, the earth's orbital velocity is about 67000 mph compared with about 1000 mph rotational velocity at the equator.)

After 20 light years of travel, the earthlings are really fatigued and anxious to get out and take a break from travel so they just head for the widest area to land and stretch their legs.

They all need a quick potty break!

My Question:"considering earlier data". What earlier data, since the discovery of this planet was not confirmed by later observations (that could be wrong). We still do not have sufficient data. Tidal lock means there is no turning of day, that the same face is always presented. Warming of the backside (away from the star) is only by circulating winds, which could be very energetic.

Having stated this, I see NO advantage on any significant level to landing, much less landing at the equatorial region, although they is a very slight enhanced orbital velocity on the furthest point from the star. This really only helps with reaching escape velocity from the star.

At the equator region the force of gravity would be some what negative to the rest of the planet because the planets rotation would create a kind of null region thus causing landing and take off easer to achieve.

1. centripetal force is higher

2. an orbit other than above the equator requires vectorial forces and inclined orbits

3. star trek is just a picture of money-crazy crackpots

That's where the only landmass is. Leaving the planet from a splash down would use more fuel.

A planet with an Earth-like environment would have to be very close to a Red Dwarf, since they emit much less radiation than stars like the Sun. The proximity to the Red Dwarf would make it likely that it had become tidally locked and, therefore, deformed into a non-spherical shape, due to gravitational forces. However, the question states that Gliese 581g is observed to be almost a perfect sphere ("considering earlier data" - as per Doorman's answer) which implies, in the fictional context of the question, that it is most likely spinning about its own axis to avoid becoming deformed. Otherwise as Usbport's answer.

There is no general requirement for any such planet to be in orbit near a Red Dwarf, unless the star's mass, planetary mass, and orbital period observed dictate this as a solution to the mechanics. Certainly being nearer a red dwarf (if you like them) is better, warmer than being further away, but I prefer blondes (as we have here on Earth). If the planet is in tidal lock, and the orbital period is small, could this have a similar effect as rotational momentum?

I suppose we will never know until we get there. Speaking of getting there, I heard an announcement over the weekend of a consortium preparing a group of small laser-propelled probes to be sent to Alpha Centauri. The probes are to be traveling at a significant fraction of light speed by the end of laser impulse cycling. I bet their little butts will be quite hot for a time thereafter.

I hate to answer this month's question like last months, but, the reasons for landing in the equatorial region to save fuel have already been covered very well.

However, the answer to the question:-

"They decide to land in the equatorial region to save fuel. Why?"

is surely, because it's difficult to find a filling station when you're 20 light years from home.

Incidentally this guy does some really accessible calculations on all sorts of interesting subjects:-

http://mathscinotes.com/2016/04/exoplanet-revolution-period-about-a-dwarf-star/

That was a particularly well phrased explanation, and was relatively easy to follow (for a change). Thank you for sharing.Cheers!