Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[WillowLuman]

Neato! Hopefully we can get some of our space telescopes to examine them for a long period and get some spectral analysis of the planets themselves.

[TempAcc]

If the planets are stable (have an atmosphere, are not irradiated as all infinite hell, etc), then ye, it might have primitive life on it, since life on earth is suspected to have started pretty damn fast once the right conditions were in place.

Hopefuly they aren't tidal locked rocks or colder versions of venus.

[Starver]

Trying to use a simple online relativistic calculator (doesn't do return journeys, although it does do the half-accelerate, half-decelerate thing) to save time debugging my own calculations, it appears as if if we can get a probe to consistently accelerate (then decelerate, symmetrically) at 0.2g for just under 50 of our own years, it would travel those 40ly, with an assumed similar time to sample-return for the next half of that century.  (On-board time would be 20-odd years, per direction, as it tops out at 98ish% of SoL each time. -  Remember to design the antenna/transeiver stuff to deal with the redshift/blueshift, if you're wanting contact mid-flight!)

0.02g would give just under 97 years (70% SoL at midway, 85 years on-board), but that doesn't factor the wait for the return transmission, so an 0.08g acc/deceleration cycle is just under 60 years (40 years on-board, 92.6% SoL max), ready for the 40yr return transmission.

(Coasting, for a period at max velocity, is easily calculable but introduces another level of arbitrary vagueness to the mission parameters unless you have any definite constraints in mind.)

But now you have try to design that mission, with suitable reaction mass (rocket equation madness!) and/or a handwavium-type reactionless drive such as is still far from confirmed and with both sufficient power and effect. And to operate and control itself appropriately for several decades, not even including the investigative payload, whatever that is... 

[martinuzz]

Neato! Hopefully we can get some of our space telescopes to examine them for a long period and get some spectral analysis of the planets themselves.

The US Kepler telescope has in fact been observing the same system since late 2016. It's data will become available on the 6th of march.

[Max™]

The Guardian article: https://www.theguardian.com/science/2017/feb/22/thrilling-discovery-of-seven-earth-sized-planets-discovered-orbiting-trappist-1-star

The thing though is that they'd likely be tidally locked, which would make things harsher for life, but certainly not impossible. However, given that the planets orbit so closely together, I wonder if the perturbations would be enough to keep them rotating.

Also, is that star a known flare star? Red dwarf stars are notorious for throwing massive flares.

Given the age it is weird that it rotates as slowly as it does, but that would lead one to think it is unlikely to flare much if at all, though we're still investigating the causes of stellar flares.

Fun word for the day: Magnetohydrodynamics!

"The study of the magnetic properties of electrically conducting fluids. Examples [...] include plasmas," sounds like a fun field to me!

"What do you want to study when you grow up, Billy?"
'The dynamics of dense fluids composed of tiny little magnets, oh and the magnets are on fire!'
"Uh... good luck with that?"

Yeah, 100 years is the estimated for the Alpha Centauri system which is around 4 light years away, this one is 39-40 light years away.

edit: https://en.wikipedia.org/wiki/TRAPPIST-1 The star is apparently a very young star, only about 500 million years old, so, if there IS life on there, the most we could expect to find is something resembling the primitive life forms that evolved on early Earth. There's evidence that life started extremely quickly, so, chances are good we could find something there, given the right conditions.

This is weird but kinda more exciting because it isn't just a red dwarf, it's a young and very cool dwarf at the lower end of the Red Dwarf scale, 2550~ Kelvins and 0.08 Solar Masses when Red Dwarf stars can go up to 4000 Kelvins and 0.5 Solar Masses.

Spoiler (click to show/hide)

Neat setting material for sci fi though, finally a story setting where you could look up and actually resolve other planets as discs without making astronomy nerds everywhere cringe *cough*looking at you, Predators*cough* and enjoy playing with the possibilities there.

A neat possibility would be if one of the planets had a large enough moon to keep the night side from freezing entirely due to tidal smushing, so the atmosphere didn't end up snowed out and frozen in place.

Don't think there would be enough light reflecting off the other planets to influence life cycles much, but it could probably have a similar sort of influence that full moons and new moons have on nocturnal hunting I think?

[Reelya]

http://www.bbc.com/news/science-environment-39034050

They found a small star 40 light years away that has 7 Earth-like planets in inner orbits, at least three should be in the habitable zone of that star. The star's low intensity means that we can see them clearer so they're hopeful that can get spectrography readings for what's in the atmospheres. That star is a really good research candidate.

[TheDarkStar]

A neat possibility would be if one of the planets had a large enough moon to keep the night side from freezing entirely due to tidal smushing, so the atmosphere didn't end up snowed out and frozen in place.

Don't think there would be enough light reflecting off the other planets to influence life cycles much, but it could probably have a similar sort of influence that full moons and new moons have on nocturnal hunting I think?

I doubt there are moons around the tidally-locked planets. Over large amounts of time, moons end up tidally locked to planets, but if the planet is already tidally locked then the the only places that the moon could still be gravitationally bound the the planet and still be tidally locked would be the Lagrange points which aren't especially stable (or close to the planet).

[TheBiggerFish]

http://www.bbc.com/news/science-environment-39034050

They found a small star 40 light years away that has 7 Earth-like planets in inner orbits, at least three should be in the habitable zone of that star. The star's low intensity means that we can see them clearer so they're hopeful that can get spectrography readings for what's in the atmospheres. That star is a really good research candidate.

This has been the topic of the past 10 posts.

Ninja.

[tonnot98]

http://www.bbc.com/news/science-environment-39034050

They found a small star 40 light years away that has 7 Earth-like planets in inner orbits, at least three should be in the habitable zone of that star. The star's low intensity means that we can see them clearer so they're hopeful that can get spectrography readings for what's in the atmospheres. That star is a really good research candidate.

This has been the topic of the past 10 posts.

Ninja.

By 10 others.

Anyway, it's great because if we can only travel at light speed, it's still a feasible travel location!

[Starver]

I doubt there are moons around the tidally-locked planets. Over large amounts of time, moons end up tidally locked to planets, but if the planet is already tidally locked then the the only places that the moon could still be gravitationally bound the the planet and still be tidally locked would be the Lagrange points which aren't especially stable (or close to the planet).

The Earth is not tidally locked to the Moon which is tidally locked to it.

The complications of the Sun's towards-a-tidal-lock-upon-Earth influence also affecting the lunar orbit isn't inconsequential, but I don't think there's any technical reason why a moon can't be orbiting a planet, locked to it, whilst the planet is orbiting the star and locked to said star.

(Note that L1 and L2 (also L3) are unstable points of equilibria, so I would not expect a natural 'perma-conjuction/opposition' to form up. L4/5 are loosely stable, but expect a 'kidney-bean' orbit without artificial efforts to place the moons into the ioscelesal third point, effectively ±60° off in the same orbit.   All this vastly complicated by the masses of the moons (a factor not usually significant with spacecraft, in their perturbation of the barycentre of all three objects), and of course the additional planets (and moons) co-orbiting in dissimilar resonances complicate things even further.  If there are L4/5 moons, in principle, then I expect them to occasionally 'defect' - if not get thrown away beyond any planet's momentary 'ownership'.  Seven significant planets in narrow orbits probably already jostle around and 'migrate', their ancillary satellites little more than chaff on the stellar winds, but I've yet to look at the specifics so far discovered about this system. And smarter minds than mine will have already shoved all available data through countless analyses that are beyond even my own imagination, never mind expertise.)

It would be tricky to get non-mutual/cascading locking, but less tricky than any three-body locking [well, two-body and the star yet to be dragged to a rotation matching its subordinate partners... that last step will probably take longer than the system has 'life' for]. I think, more likely, would be that chaotic degeneration of any star-planet-moon system, as described, before the planet locks to star.  But it would benefit from some many simulations of wide ranging and contrived setups, to be sure.

[Max™]

I doubt there are moons around the tidally-locked planets. Over large amounts of time, moons end up tidally locked to planets, but if the planet is already tidally locked then the the only places that the moon could still be gravitationally bound the the planet and still be tidally locked would be the Lagrange points which aren't especially stable (or close to the planet).

This system hasn't had a large amount of time yet, it looks to be like half a billion years old apparently.

[Il Palazzo]

The system is comparable in size to Jupiter and its Galilean moons, only with the central object 80 times and the satellites ~10E12 times as massive. The only reason it's stable as it is, is due to orbital resonances all planets are in. There's no way you could plop anything into any Lagrange point and expect it to stay there. The dynamic stability of L4&5 is only a solution of a restricted 3-body problem, and this system doesn't qualify as such.

A moon that actually orbits a planet would have to be within its Hill sphere, so a bit closer than L1&2. Since a moon that is tidally-locked to a planet which is tidally-locked to its star would have to be in either of those points, it tells us that:
- there can't be such a moon in this system
- any moons the planets might actually have will orbit them closer than L1&2, which means they will orbit faster than the planet rotates, which means that the moons are destined to collide with any planet that might have them, within geological timescales*

This in turn means that either the planets don't have moons, or will eventually not have moons.

*these are likely to be relatively short, since the Hill spheres for all planets are between 1/2 and 1/10th of the Earth-Moon distance, so tidal interactions would be intense - the larger the satellite, the stronger.

[Starver]

There's no way you could plop anything into any Lagrange point and expect it to stay there.

I agree with this, and said as much, and therefore assume you weren't replying to me.

The dynamic stability of L4&5 is only a solution of a restricted 3-body problem, and this system doesn't qualify as such.

Ditto.

A moon that actually orbits a planet would have to be within its Hill sphere, so a bit closer than L1&2. Since a moon that is tidally-locked to a planet which is tidally-locked to its star would have to be in either of those points, it tells us that:
- there can't be such a moon in this system

I disagreed on this point, omitting to give the main reason to assume that a freely orbiting (whether or not tidally-locked) moon would tidally drag the planet (towards spinning at the rate of once per local 'lunar month', sidereally, I think that is), to at some point counteract the slower solar-tidal-drag (once per solar year, likewise).  In an otherwise stable and long-lived (three-body!) solution, the ultimate convergence would be upon a rate of spin somewhere between the two (probably related to ratios of the masses; distances seem to cancel out, in my basic headcalculations...)

- any moons the planets might actually have will orbit them closer than L1&2, which means they will orbit faster than the planet rotates, which means that the moons are destined to collide with any planet that might have them, within geological timescales*

That's a point I can't argue with. The faster Earth is lending orbital velocity to the Moon and sending it outwards, but 'getting close to annual rotation' planets are doubtless buying back the potential.  That'd be fun to watch, the proximity rendering the moon-mass no longer stable as a whole body, creating a close ring that eventually starts to bombard around the equator, with various other interesting after-effects to both lithosphere and atmosphere.  Maybe.

This in turn means that either the planets don't have moons, or will eventually not have moons.

Eventually, the Earth wouldn't have a Moon, if not for Sol's middle-age spread getting in on the act and disrupting things.. In a multibody system, already with suspected resonances, an equivalent time-scale might well rearrange any moons there are (assuming that at least one of the planets isn't a conglomeration of 'spare moons', or proto-moon/proto-planet/prior-collision-debris that (literally!) gravitated towards a meeting at some suitable resonance), but there could be a temporary arrangement (on stellar terms) that can still inspire and even outlast a pretty sharpish civilisation.

[Dorsidwarf]

It's interesting how close all these planets are. According to Scott Manley , the ratio of infrared light to visible light would be like standing on earth at dusk, but as warm as midday.

[WillowLuman]

Also, a tidally locked planet wouldn't necessarily have its atmosphere snow out. Venus experiences days longer than its years, yet its atmosphere essentially rotates approximately every 4 Earth days. Thermodynamics drives global winds from the warmer day side across the cooler night side and back.

A planet experiencing such constant, strong global winds presents challenges of its own to life, but not insurmountable I think.