At least 3 planets in habital zone, one star:

Originally posted by twhitehead
And if it turns out its not suitable, you just kill off that group and move on to the next star?

Well you would of course suss out the planets before hand with super telescopes and probes if you can, but the nice thing about this discovery is you have a large number of planets to choose from.

Just like my previous thoughts about Alpha Centauri, you go there, robots or humans, whatever, and you get three for the price of one. Three stars within a tenth of a light year apart.

Originally posted by Metal Brain
Even if you made the long trip you might get there and find a Venus like planet.

I think it is amusing that news reporters leave out the word "may" and say they are Earth like planets just because they are of similar size. Odds are they are Venus like planets.

Well the odds in our solar system, 8 or so planets, one Venus.

So it might go on this new system. There are 7 possibles and the thing is, the star is a dwarf with .0005 X the radiation output of our star so that limits the possibility of Venus worlds right there. In our neck of the woods, on top of our atmosphere we get about 1300 watts per square meter. At the same distance from that dwarf star, about a half watt per square meter. So the planets have to be a LOT closer to get something like that amount of radiation per square meter. They found these planets in orbits close to the dwarf star where the amount of radiational heating is similar to Earth's orbit, except the light is more infrared than visible but it still would do the job of heating up the planets.

It depends on the atmosphere whether it turns into radical greenhouse heating like Venus.

How much CO2 and so forth in the atmosphere.

They could all just be barren rocks, we don't know at this point in time.

I expect we will know as better telescopes come on line. I'd like to see a 10 mile wide scope (made with separate mirrors combined optically and electronically to act as one giant mirror) on the backside of the moon. No atmosphere and a scope like that would have something like 10,000 times the resolution of Hubble. It would be able to see features about 1000 miles across at 40 light years which would enable them to suss out just exactly what, if any, atmospheres they have. I think we will know way before a scope like that ever gets built though. There are tricks you can play with regular big guy telescopes like the ones in Chile where you very carefully watch the beginnings and endings of eclipses around that star and bits and pieces of what is in the atmosphere can show up. But that is a far cry from a scope that can actually image the planets even with a low res of 1000 miles, that would tell them directly what the planet is made of.

Originally posted by sonhouse
There are 7 possibles and the thing is, the star is a dwarf with .0005 X the radiation output of our star so that limits the possibility of Venus worlds right there.

No, you have it all wrong. There are only three planets in the 'habitable zone', not 7.

At least one of the seven is closer to the star than the habitable zone, so mercury type temperatures.

Another factor is I think they said some, or all of them, are tidally locked, so they get radiation on one side only. They also interact with each other which may cause all sorts of weird issues.

Originally posted by sonhouse
I expect we will know as better telescopes come on line. I'd like to see a 10 mile wide scope (made with separate mirrors combined optically and electronically to act as one giant mirror) on the backside of the moon. No atmosphere and a scope like that would have something like 10,000 times the resolution of Hubble. It would be able to see features about 10 ...[text shortened]... ght years which would enable them to suss out just exactly what, if any, atmospheres they have.

Actually for studying planets that far away, spectography is far more important than resolution.

Originally posted by twhitehead
No, you have it all wrong. There are only three planets in the 'habitable zone', not 7.

At least one of the seven is closer to the star than the habitable zone, so mercury type temperatures.

Another factor is I think they said some, or all of them, are tidally locked, so they get radiation on one side only. They also interact with each other which may cause all sorts of weird issues.

All seven planets could have liquid water under the right atmospheric conditions, however.

https://www.nasa.gov/press-release/nasa-telescope-reveals-largest-batch-of-earth-size-habitable-zone-planets-around

The "habitable" zone is really more of a "greatest likelihood of having life-as-we-know-it zone."

In any case it is indeed likely that all the planets are tidally locked to the star. Also, the orbits of the planets are so close together that some of them will appear bigger in the sky than the moon does from Earth, and be visibly moving from minute to minute. That's pretty amazing.

If Earth were the third rock from the sun in that system, then instead of moon landings half a century ago, we would have been visiting the other six worlds, and possibly establishing colonies. Trappist-1 is estimated to be at least half a billion years old, and possibly over one billion, but will live for up to 12 trillion years.

Weird issues do arise with planetary orbits on a gigayear scale, even (according to computer models) in our own solar system. Neptune and Uranus could someday trade places, or one could get flung out into "Planet Nine" territory or be plunged into the inner solar system. The Trappist system could experience worse over time.

Here's an interesting paper I skimmed through months ago. One page 11 and elsewhere are some curious things that computer models indicate could happen over the span of 10 or 20 billion years on account of a hypothetical Planet Nine far out in our solar system.

https://arxiv.org/pdf/1608.07580.pdf

Originally posted by Soothfast
Here's an interesting paper I skimmed through months ago. One page 11 and elsewhere are some curious things that computer models indicate could happen over the span of 10 or 20 billion years on account of a hypothetical Planet Nine far out in our solar system.

https://arxiv.org/pdf/1608.07580.pdf

A bit much to read so went directly to conclusions. It won't help Earth much when the sun grows to be one AU in diameter and Earth gets fried. Of course humans will be long gone by then anyway so it is a moot point for us here on Earth. It of course has implications for the study of interstellar solar systems, because there are already stars 13 billion years old so the 7 billion years mentioned should have happened trillions of times already in our universe. So it may help in the quest for Earth like planets and such but no help for humans.

Originally posted by Soothfast
I'm ignoring the practical issues involved in sustaining a 1g acceleration for a year, which would indeed be astronomical. I don't seriously propose such an endeavor. Getting up to 0.1c or 0.2c would be, I think, about the best that we could hope for for a ship with a human crew.

I wasn't aware of the issues with the interstellar medium, though. You ...[text shortened]... reminded me of the ramjet proposals of old, which would use the medium for fuel en route.

I was slightly suspicious of my own statement, which was based on a media report that said an expert had done a calculation. So I did a calculation. The proper acceleration, in other words the one an instantaneously comoving observer sees the spaceship accelerate with is 1g. An earth bound observer (I'll call this the "stationary frame" from now) sees an acceleration that is smaller by three powers of the gamma factor. A few integrations later I got some expressions for the speed a ship would get to if it travelled for various amounts of time in the stationary frame. After one year they would be at about 72% of the speed of light and the corresponding gamma factor would be about 1.45. So the number density of particles in the interstellar medium would scale by one gamma factor, which follows from length contraction in the direction of movement. This means the crew of the spaceship would see 1.45 particles per metre cubed rather than 1. The incoming flux is then density times velocity. These protons hit the front of the spaceship at 72% of the speed of light and will produce 423 MeV of gamma radiation as bremsstrahlung (and more exotic reactions) so the flux of ionising radiation is 0.31 MBq per metre squared of ship's cross-section per second. That's going to produce doses of up to 0.02 Sieverts per metre squared per second. A lethal dose is about 5 Sieverts and that will happen in minutes. This is going to require a lot of shielding...

Originally posted by DeepThought
This is going to require a lot of shielding...

It sounds to me like 'starshot' idea will fail due to the electronics being fried and the sail being destroyed by the interstellar medium.

YouTube

Originally posted by twhitehead
It sounds to me like 'starshot' idea will fail due to the electronics being fried and the sail being destroyed by the interstellar medium.

https://www.youtube.com/watch?v=l6cjAyneeY4

They're only talking about 20% of light speed, so the gamma factor is small (~1.02) and the best space hardened electronics can take amazing levels of radiation (see eg [1]). Aiming the laser over interstellar distances is going to be the problem with that thing (I didn't watch it as it is 90 minutes long).

I noticed I wrote 0.31 MBq above, that should read GBq, in other words a 300 million particles per second, and it should be per metre squared and not per metre squared per second - I was getting confused with the radioactive dose units which are cumulative and not rate based. Bequerel isn't quite the right unit as that is source intensity (disintegrations per second) but since the "source" is particles striking the ship's hull and the ensuing radiation is indistinguishable from nuclear radiation (except for the higher energy) it seemed appropriate. The actual apparent activity will be higher as the protons have kinetic energy about 45% of their rest mass in the co-moving inertial frame after 1 years acceleration at 10m/s^2, so each one will undergo multiple scattering events as it ploughs through the hull. Each scattering event will produce secondary radiation which will either be hard gammas or leptons, hadrons are also a possibility but because the energy is too low for baryon production, they'll be mesons which will decay into gammas or leptons. My estimates are over estimates because I didn't account for the astronauts not absorbing all the radiation that impinges on them and I haven't taken into account energy loss due to neutrino production, but well hey it's an internet forum...

It also occurs to me, how are they going to slow the probe down? Put the laser into tractor beam mode?

[1] https://en.wikipedia.org/wiki/RAD750

Originally posted by DeepThought
They're only talking about 20% of light speed, so the gamma factor is small (~1.02) and the best space hardened electronics can take amazing levels of radiation (see eg [1]). Aiming the laser over interstellar distances is going to be the problem with that thing (I didn't watch it as it is 90 minutes long).

I noticed I wrote 0.31 MBq above, that shou ...[text shortened]... e probe down? Put the laser into tractor beam mode?

[1] https://en.wikipedia.org/wiki/RAD750

That would be for craft with 20th and 21st century design. There are designs afoot that instead have a donut shaped craft with a huge magnetic field that guides the radiation inside the donut where the ship isn't and it just passes by with no impacts on the ship. So it emulates Earth's magnetic field except needing to be thousands of times stronger. If we ever get room temp and above superconductors it wouldn't even be that big a deal to create. Even the present generation of high temp supers at say 100 degrees Kelvin could do the job but needing an input of energy for the refrigeration required.

Originally posted by DeepThought
Aiming the laser over interstellar distances is going to be the problem with that thing (I didn't watch it as it is 90 minutes long).

It also occurs to me, how are they going to slow the probe down? Put the laser into tractor beam mode?

I believe the idea is to get it up to speed well within our solar system.

There is no slowing down. It just zooms past the system it is targeted at, rather like the New Horizons mission did with Pluto.

If the idea works, then they can send one every week to monitor a star, or send one, or several to every nearby star. If it worked, the cost per probe would be minimal.

I wonder how steerable they would be. If you are off by a tiny amount within the solar system, you will miss the target star by a large amount. If they were accurate enough then one could arrange flybys of planets at target stars.

Originally posted by twhitehead
I believe the idea is to get it up to speed well within our solar system.

There is no slowing down. It just zooms past the system it is targeted at, rather like the New Horizons mission did with Pluto.

If the idea works, then they can send one every week to monitor a star, or send one, or several to every nearby star. If it worked, the cost per prob ...[text shortened]... e amount. If they were accurate enough then one could arrange flybys of planets at target stars.

That makes sense. How do they intend to get a signal back? That in itself is not a trivial matter. For steering the probe could have its own boosters, they wouldn't need to carry much propellant.

Originally posted by Soothfast
All seven planets could have liquid water under the right atmospheric conditions, however.

https://www.nasa.gov/press-release/nasa-telescope-reveals-largest-batch-of-earth-size-habitable-zone-planets-around

The "habitable" zone is really more of a "greatest likelihood of having life-as-we-know-it zone."

In any case it is indeed likely that all the ...[text shortened]... r be plunged into the inner solar system. The Trappist system could experience worse over time.

Red dwarves tend to flare a lot so although the temperature is right for liquid water everything else is wrong for life. The planets are tidally locked and radiation from stellar storms will be intense.

Originally posted by DeepThought
How do they intend to get a signal back?

The video I watched didn't go into details on the signaling method. They seemed to imply it was easy (although with a time constraint obviously). So you need travel time to the system plus signal time back.