Source on the &#x27;trillions of years&#x27; number?

Well, it&#x27;s estimated that it will still be around in 4-5 trillion years, so, if we can get there, and it&#x27;s habitable, that gives humanity a little longer lease in the universe.

It&#x27;s 39 light years so no fewer than 39 years from our perspective. The closer to the speed of light the travelers are the less time will appear to have elapsed from their perspective. If you had rockets that could instantaneously accelerate to infinitessimally close to the speed of light, no time at all would appear to have elapsed from the travelers perspective (or no time that they would notice), but this is very unlikely.

Well it is approximately 40 light years away from our solar system. So the basic calculation would say about 42 years but this doesn&#x27;t account for acceleration and deceleration and such.

At a constant 1g of acceleration, you could travel there, from the traveler&#x27;s point of view, in ~2-3 years. (And in ~40 years from a stationary observer&#x27;s point of view.)Mind you, a constant 1g acceleration (Or accelerating any human-carrying spaceship to relativistic speeds, really,) is about as plausible as a spaceship driven by pixie dust and unicorn farts.

The answer for an outside observer is: 
@ 1g of acceleration it would take 11 months to accelerate to the speed of light. A formula you can put in Google is: (285000000&#x2F;9.8)&#x2F;(60x60x24).So 39-(.475x2) = 38, and 38&#x2F;.95 = 40. So 42 years is your answer.I have no idea how to calculate the relativistic spaceship&#x27;s elapsed time.It&#x27;s all wishful thinking. The fastest thing man has created, the Juno spacecraft, travels, by some quick calculations, @ 0.00147% of the speed of light.

It&#x27;s a Trap ;)On a serious note, if we can travel close to the speed of light , say 95%, using for example, nuclear rockets, how long would it take to arrive ? ( from the travellers perspective )

I don&#x27;t know about all of that speculation, but you did give me a nice mental image of a barren, battle-scarred solar system littered with battleships containing black holes, ready to cause catastrophe at any moment, much like the nuclear wastelands of the Arctic.

&gt; So we may have to wait a century or two.It took some thousands of years to be able to circumnavigate the planet, and some centuries after that to do it quickly and safely.It feels IST in a matter of centuries from now is extremely optimistic.

I doubt we&#x27;ll attempt serious inter-stellar travel before we figure out antimatter or black hole-powered engines. So we may have to wait a century or two.This century we should be more worried about making fusion-powered intra-solar system travel a common thing, and about establishing large colonies on Mars and several moons.

At Voyager-I speed (17km&#x2F;s) we need just 688k years to get there.
Not bad considering the humble satelite doesn&#x27;t accelerate anymore.

I was essentially thinking the same thing. I wonder if an elevator could be built between all of them?

I guess J.J. Abrams is somewhat forgiven for this, then:<a href="http:&#x2F;&#x2F;vignette4.wikia.nocookie.net&#x2F;startrek&#x2F;images&#x2F;2&#x2F;29&#x2F;Vulcan_dies_in_Delta_Vegan_skies.jpg" rel="nofollow">http:&#x2F;&#x2F;vignette4.wikia.nocookie.net&#x2F;startrek&#x2F;images&#x2F;2&#x2F;29&#x2F;Vul...</a> [edited for direct .jpg]

Uh, Mongo when it flew by Earth?edit: Mongo from Flash Gordon

One of the games I&#x27;m working on (a sci-fi mech and space combat action rpg) actually is set in a solar system like this. Cool to see one in reality relatively close by! I think it provides a lot of interesting situations allowing for basically a &quot;space opera in a solar system&quot;.

Anyone else immediately think that we&#x27;d discovered Krypton when they read &quot;red sun?&quot;

Sounds like you haven&#x27;t read The Three Body Problem (which is a shame, you should totally check it out).

*Hollywood sci-fiYou get a lot more crazy worlds in written sci-fi. You can start with the Culture orbitals, some of the Commonwealth Saga worlds or Alastair Reynolds&#x27; inhibitors. If you count a neutron star with life on it, you get dragon&#x27;s egg which is a must-read.

So, basically, this is cooler than just about any world that&#x27;s been depicted in sci-fi.

Actually they are fewer. A dim star has less high energy radiation and a lower probability of harmful solar flares.

&gt; are there...hazards simply due to the proximity of a dim starTidal locking [1]. Similar to how our moon shines at us ass first all the time, the planets around TRAPIST-1 would be expected to have one face locked to their star. Instead of an equatorial belt bookended with loops of temperate zones, as we have on Earth, we should expect, climatically, an &quot;equatorial&quot; face and a &quot;polar&quot; face separated by a tropic-to-temperate transition area.[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Tidal_locking" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Tidal_locking</a>

Depending on the spectrum of the star, I would be concerned about non-visible radiation doses when in close proximity to the star.IANA astrophysicist, though.Actually, adding onto that, I&#x27;m wondering whether orbits this tight would result in a noticeable centripetal force -- that is, that you&#x27;d feel lighter on the night side of the planet than on the day side.

Michael Okuda has raised the question on his Twitter feed of whether the planets would be close enough to the star that tidal force could be an issue---hard to say at this point (in the sense that they&#x27;re not loose clouds of rocks, so tidal forces haven&#x27;t sheared them apart, but I&#x27;d assume it&#x27;s unclear whether they might have interesting geological activity, such as frequent earthquakes or unexpected extra heat due to internal friction).

Like others have pointed out, the combination of the planets being tidally locked so only one side gets sunlight and the strong X-ray radiation and flaring from the host star make it considerably un-Earth-like, and harder for life as we know it to develop.

Out of interest , although dimmer, are there any potential hazards simply due to the proximity of a dim star?

Those cool stars are also very durable and will not burn that easily.

And they all seem to rotate around their sun in 1.5-20 days.<a href="https:&#x2F;&#x2F;i.kinja-img.com&#x2F;gawker-media&#x2F;image&#x2F;upload&#x2F;s--YG_G3T_3--&#x2F;c_scale,fl_progressive,q_80,w_800&#x2F;x6skcv87jisavlga1bmq.jpg" rel="nofollow">https:&#x2F;&#x2F;i.kinja-img.com&#x2F;gawker-media&#x2F;image&#x2F;upload&#x2F;s--YG_G3T_...</a>

I wonder what planets that close together would do to tides on one another.

Other awesome facts, the closest star in the habitable zone might have a &quot;year&quot; of a day and a half, and the furthest out in the zone, a &quot;year&quot; of 20 days.

Melancholia by Lars von Trier is another great movie about the earth colliding with another planet.<a href="http:&#x2F;&#x2F;www.imdb.com&#x2F;title&#x2F;tt1527186&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.imdb.com&#x2F;title&#x2F;tt1527186&#x2F;</a>

&gt; If a person was standing on one of the planet’s surface, they could gaze up and potentially see geological features or clouds of neighboring worlds...Makes me think of the film Another Earth<a href="http:&#x2F;&#x2F;imgur.com&#x2F;a&#x2F;01xlN" rel="nofollow">http:&#x2F;&#x2F;imgur.com&#x2F;a&#x2F;01xlN</a>

Sounds like tidal forces would be extreme.

And I was just thinking, if there were ever or ever to be oceans on these planets what kind of brutal tides would be experienced?

I&#x27;m blown away the planets haven&#x27;t torn each other apart or all collided by now...

&gt; the TRAPPIST-1 star – classified as an ultra-cool dwarfI propose we name it &quot;Dinklage.&quot;

&gt; no way that a civilization that developed on such a planet would not at some point endeavor to travel to those other planets.That seems like a very human statement.One could argue for a civilization to succeed it must be content with living on its home planet. And as a result, it would take good care of it.

Importantly, that means there is basically no way that a civilization that developed on such a planet would not at some point endeavor to travel to those other planets.

A colleague of mine has an insider info that the telescope was named after beer on purpose.

And the name of the star is shared with Trappist beer!

Wonder how tidal forces from these planets would affect [possible] oceans on their neighbors.  Would imagine it would make for quite a perturbed environment.

Perhaps some of them, especially the innermost. Considering the orbital periods and resonance it seems like this system might be similar to the Jovian or Saturnian systems.The planets may be tidally locked but there is also a chance they could have a slow rotation similar to Mercury. That planet has also shown us that a magnetic field is possible without a fast rotation so there&#x27;s a chance of these exoplanets having one as well.Tidal forces can be a boon to planets with synchronous rotation since they provide an additional source of heating for the side of the planet that faces away from the star. If there is liquid water or a thick atmosphere they may also drive tidal and weather patterns that could help circulate heat from the warm side to the cold side.Geological activity also &#x27;stirs the pot&#x27; when it comes to precursors for life. All this extra energy in the system could mean that even TRAPPIST-1g (outside the habitable zone) might have an atmosphere and oceans.

So this means all the planets are all a volcanic mess because of the tidal forces?

My thoughts exactly. The coolest skyscapes ever!
On edit: This also reminds me of U. LeGuin&#x27;s system in the dispossessed.

maybe them aliens made the system up, so that it doesn&#x27;t fall apart under its own gravity. Makes sense: just increase the habitable area by bringing in smaller planets into the goldilock zone - that might come out cheaper then to go interstellar.Maybe lots of planets that circle the same star over the same orbit would be a better indicator of alien activity than a dyson sphere.

I&#x27;m wondering since these planets are so close to the parent star and to each other would it induce any gravitational instabilities?

Well, in Lexx, there was Fire[0] and Water[1], which shared an atmosphere[2] which could be traversed with balloons.[3]0) <a href="http:&#x2F;&#x2F;lexx.wikia.com&#x2F;wiki&#x2F;Fire" rel="nofollow">http:&#x2F;&#x2F;lexx.wikia.com&#x2F;wiki&#x2F;Fire</a>1) <a href="http:&#x2F;&#x2F;lexx.wikia.com&#x2F;wiki&#x2F;Water" rel="nofollow">http:&#x2F;&#x2F;lexx.wikia.com&#x2F;wiki&#x2F;Water</a>2) <a href="https:&#x2F;&#x2F;goo.gl&#x2F;images&#x2F;xmxoJ9" rel="nofollow">https:&#x2F;&#x2F;goo.gl&#x2F;images&#x2F;xmxoJ9</a>3) <a href="https:&#x2F;&#x2F;goo.gl&#x2F;images&#x2F;oyVNF0" rel="nofollow">https:&#x2F;&#x2F;goo.gl&#x2F;images&#x2F;oyVNF0</a>

Thank you, this is truly amazing. For all the people interested in any way in space - watch this :)

I just watched this twice. It made me smile, hopeful, and happy. Thank you.

I watched this 10 times in a row. It gave me shivers every time...

If you liked this, you&#x27;ll probably also like MelodySheep&#x27;s Symphony of Science series.<a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=zSgiXGELjbc" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=zSgiXGELjbc</a>

Have you seen Reid Gower&#x27;s Sagan Series?<a href="http:&#x2F;&#x2F;saganseries.com" rel="nofollow">http:&#x2F;&#x2F;saganseries.com</a>It similarly combines HD cinematography with Carl Sagan&#x27;s narration. It&#x27;s not CG like this, but the overall quality is extremely high (at least after the first chapter).

It actually reminded me of Rick and Morty Season 2 last episode.

It reminded me of the end (spoiled by the poster, of course) of the (somewhat obscure) NZ sci-fi flick &quot;The Quiet Earth&quot;:<a href="https:&#x2F;&#x2F;assets.mubi.com&#x2F;images&#x2F;film&#x2F;14662&#x2F;image-w856.jpg?1445882511" rel="nofollow">https:&#x2F;&#x2F;assets.mubi.com&#x2F;images&#x2F;film&#x2F;14662&#x2F;image-w856.jpg?144...</a>

Wonderful and inspiring. I loved the narration from Carl Sagan. One of the greatest.

It reminds me of Land and Overland by Bob Shaw:&quot;The setting for the trilogy is a pair of planets, Land and Overland, which orbit about a common centre of gravity, close enough to each other that they share a common atmosphere.&quot;They don&#x27;t share a common atmosphere, but I guess the delta required for interplanetary transfer is really low.

I was very stressed and watching this calm me down. Thanks

Wanderers is indeed excellent.See also: the timelapse footage of the sky from the VLT, Paranal. Just thinking about it gives me vertigo.<a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=wFpeM3fxJoQ" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=wFpeM3fxJoQ</a>

I was very skeptical but pleasantly surprised.

I get a little choked up every time I watch this.

&gt; The planets also are very close to each other. If a person was standing on one of the planet’s surface, they could gaze up and potentially see geological features or clouds of neighboring worlds, which would sometimes appear larger than the moon in Earth&#x27;s sky.this reminds me of one my favorite films ever. it is just four minutes long<a href="http:&#x2F;&#x2F;www.erikwernquist.com&#x2F;wanderers&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.erikwernquist.com&#x2F;wanderers&#x2F;</a>

On the other hand, tidal locking can stir the pot, possibly creating more opportunities for the chemistry of life to form.One of the astronomers, Triaud has been quoted saying this is a relatively calm red dwarf that doesn&#x27;t produce a lot of flares.

As these planets are most probably TIDALLY LOCKED, making it hard for LIFE to thrive.&gt; All seven of TRAPPIST-1&#x27;s planets orbit much closer than Earth orbits the Sun. A year on the closest planet passes in only 1.5 Earth days, while the sixth planet&#x27;s year passes in only 12.3 days&gt;Tidally locked planets likely have very large differences in temperature between their permanently lit day sides and their permanently dark night sides, which could produce very strong winds circling the planets, while making the best places for life close to the mild twilight regions between the two sides.&gt; Another important consideration is that red dwarf stars are subject to frequent, intense flares that are likely to have stripped away the atmospheres of any planets in such close orbits.<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;TRAPPIST-1" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;TRAPPIST-1</a>

Nuclear pulse propolsion... Project Orion... if only we could figure out the darn problem with the fallout and treaties&#x2F;bans.

Just as interesting is a recent news story about a plan to build an interstellar space ship, propelled by giant solar sails to travel about .2c (20% of the speed of light).In other words, we could get to the Trappist-1 star system in about 145 years.. practically in the blink of an eye.<a href="https:&#x2F;&#x2F;www.gizmodo.com.au&#x2F;2017&#x2F;02&#x2F;how-an-interstellar-starship-could-actually-explore-alpha-centauri&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.gizmodo.com.au&#x2F;2017&#x2F;02&#x2F;how-an-interstellar-stars...</a>

I wonder what kind of tidal forces these planets exert one one another.

That&#x27;s exactly the premise of the (good) movie Another Earth: <a href="http:&#x2F;&#x2F;www.imdb.com&#x2F;title&#x2F;tt1549572" rel="nofollow">http:&#x2F;&#x2F;www.imdb.com&#x2F;title&#x2F;tt1549572</a>

I am wondering how it could affect our psyche if we were able to gaze on a mirror world with our own eyes in broad daylight. This is the first VR application I would think of: display an Earth like planet in the sky and see how it affects us.

My favourite part of the press release:&gt; The planets also are very close to each other. If a person was standing on one of the planet’s surface, they could gaze up and potentially see geological features or clouds of neighboring worlds, which would sometimes appear larger than the moon in Earth&#x27;s sky.&gt; In contrast to our sun, the TRAPPIST-1 star – classified as an ultra-cool dwarf – is so cool that liquid water could survive on planets orbiting very close to it, closer than is possible on planets in our solar system. All seven of the TRAPPIST-1 planetary orbits are closer to their host star than Mercury is to our sun.<a href="https:&#x2F;&#x2F;www.nasa.gov&#x2F;press-release&#x2F;nasa-telescope-reveals-largest-batch-of-earth-size-habitable-zone-planets-around&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.nasa.gov&#x2F;press-release&#x2F;nasa-telescope-reveals-la...</a>

It&#x27;ll be in the near-infrared, but the light won&#x27;t be separated from the star. How they observe the atmosphere is that when the exoplanets transit, they block out different amounts of light at different wavelengths. From that, one can deduce an atmospheric spectrum.

Optically? That&#x27;s nuts! Anyone know how this would work? Can we really expect Webb to measure light diffraction&#x2F;refraction through a few miles of atmosphere on a planet 40 ly away?

A Hubble or James Webb is easily a billion dollar effort, making it THE major limitation for discovery. No one is investing that sort of money for no return. Honestly, even if they did, it would be frowned upon considering the more important humanitarian investments at hand.

It looks like the James Webb cost $8.7B to launch.  The Hubble $4.7B at launch and $10B through till 2010.  So it seems cost is the limiting factor.  Replicas might be cheaper, but they wouldn&#x27;t be kickstarter cheap.

Can someone explain to me why we don&#x27;t replicate some of these key platforms like the Hubble and James Webb ST?It seems like the major limitation for discovery is getting enough observation time for whatever certain point in the sky that scientists are researching.Why don&#x27;t we launch a second copy of James Webb?

Apparently finds are close enough to us that we should be able &quot;to follow up, to see, for example with the James Webb Space Telescope that we&#x27;re going to launch [next] year, the atmospheres and also to look at bio-signatures, if there are any&quot; !

Link to live stream on YouTube (supports rewinding) <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=UdmHHpAsMVw" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=UdmHHpAsMVw</a>

You could, and probably would.  But, how would you send everyone else?  That &#x27;traditional&#x27; method (carbon based fuels to propel a heavy payload) is extremely expensive, and slow.  So if you ever wanted to send more than just 1 payload, you&#x27;d quickly reach resource limitations (namely cost, and time).

Yup, for several hundred thousand year&#x27;s journey. No problem. :-)I would just hope my emacs session will stay up that long.

Why not just make that first payload contain actual humans? Seems a helluva lot simpler.

I think the magic speed is actually 10% the speed of light.

Or cryogenically freeze yourself with instructions to be brought back in a few millennia near the new star system. From the observer&#x27;s point of view you could be there Tuesday week or so.

40 light years isn&#x27;t a big deal if humans lived to be thousands of years old. That&#x27;s another solution.

Not to mention the reliability and throughout requirements of such a data link to another planet so far away.

has a mammalian fetus ever been developed to maturity outside of a natural womb?

If you&#x27;re going to assume heavy equipment on the other end (ours or &quot;someone else&#x27;s&quot;), it&#x27;s not ridiculously beyond our current capabilities to simply transmit DNA sequences along with enough digital training material to &quot;grow&quot; and raise a human population from scratch.

I hate to always post links to Greg Egan, but he&#x27;s sort of the XKCD of SciFi - if there&#x27;s an out there concept, he&#x27;s usually written a book about it. In this case Incandescence:<a href="https:&#x2F;&#x2F;www.amazon.com&#x2F;dp&#x2F;B0070YQOHW" rel="nofollow">https:&#x2F;&#x2F;www.amazon.com&#x2F;dp&#x2F;B0070YQOHW</a>Top review has the best summary: &quot;Egan&#x27;s story is set in the galactic core, inhabited by a race known as the Aloof, because they seem almost indifferent to any attempts at communication from the Amalgam, the loose network of civilizations that inhabit the rest of the galaxy. However, they do allow thrill-seeking members of the Amalgam to enter their transportation network, digitizing themselves for transmission at the speed of light across the galactic core, instead of the long way around it.&quot;

The whole idea of digitizing humans is silly. It would lead to spooky action at distance. For example what if when humans are digitized you send it to two different machines? Which one would be the real you?

Why humans? People are concerned about the survivability of human species, and it&#x27;s certainly a noble goal, but at this point it&#x27;s outside or technological reach. Preserving life, in the other hand, could be doable. We «just» need to take some prokaryotic cells to one of those planets, assuming they have the right environment, and in some million years you have a complete ecosystem...Assuming also, of course, that there is not life there already.

I was reading up about earth alternatives recently, and upon realizing the distance was always going to limit us, no matter how perfect the planet, I realized we need to travel at the speed of light.I think our &quot;best shot&quot; at that right now, is to digitize humans. If we could store consciousness in binary, we could then transmit it at the speed of light (like we do with data every day!). You&#x27;d need a receiver on the distant planet though. So, your first &#x27;payload&#x27; would have to be the receiver, and it would need to travel the slow old fashioned way :(

It was stated by the scientists at the NASA press release. They also stated that all seven of the planets have the potential for liquid water depending on (unspecified) circumstances.

It was said by one of the scientist in live Nasa TV broadcast <a href="https:&#x2F;&#x2F;www.nasa.gov&#x2F;multimedia&#x2F;nasatv&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.nasa.gov&#x2F;multimedia&#x2F;nasatv&#x2F;</a>

Are you basing that statement purely on the appearance of the planets in the artist&#x27;s conception you linked, or was it stated in another article somewhere?

Three of those discovered planets are in habitable zone<a href="https:&#x2F;&#x2F;www.dropbox.com&#x2F;s&#x2F;bdeog7ta7i4rb7c&#x2F;alien%20planets.png?raw=1" rel="nofollow">https:&#x2F;&#x2F;www.dropbox.com&#x2F;s&#x2F;bdeog7ta7i4rb7c&#x2F;alien%20planets.pn...</a>

Yes, the exoplanet discovery was the important announcement.

Is this from NASA news conference that was announced for today? I couldn&#x27;t find it in article? They said they have important announcement.

According to the Nature paper (last section of <a href="http:&#x2F;&#x2F;www.nature.com&#x2F;nature&#x2F;journal&#x2F;v542&#x2F;n7642&#x2F;full&#x2F;nature21360.html" rel="nofollow">http:&#x2F;&#x2F;www.nature.com&#x2F;nature&#x2F;journal&#x2F;v542&#x2F;n7642&#x2F;full&#x2F;nature2...</a>) --We computed [via n-body and other simulations] that TRAPPIST-1 has a 25% chance of suffering an instability over 1 Myr, and an 8.1% chance of surviving for 1 billion years (Gyr), in line with our n-body integrations.And, further,However, [these lifetimes] do not take into account the proximity of the planets to their host star and the resulting strong tidal effects that might act to stabilize the system. ... The masses and exact eccentricities of the planets remain uncertain, and our results make it likely that only a very small number of orbital configurations lead to stable configurations. ... The system clearly exists, and it is unlikely that we are observing it just before its catastrophic disruption, so it is probably stable over a long timescale. These facts and the results of our dynamical simulations indicate that, given enough data, the very existence of the system should bring strong constraints on its components’ properties...

If we could do large scale engineering we would engineer something like this I suppose to increase the habitable worlds in a system.

&gt; Gillon says that the six inner planets probably formed farther away from their star and then migrated inward. Now, they are so close to each other that their gravitational fields interact, nudging one another in ways that enabled the team to estimate each planet&#x27;s mass. They range from around 0.4 to 1.4 times the mass of the Earth.Given that these planets are so close to each other, and interacting with each other gravitationally, how likely is it that their orbital arrangement is stable over geological time?

Maybe several times over independently. Hopefully we won&#x27;t have to speculate long. As Jill Tarter says, &quot;we count one, two, infinity.&quot; Still waiting for two, and I hope it happens in my lifetime.

I think this is why there is no life on any of the planets. The star is just too young. However, the star could have a life span of 5 trillion years, it is safe to say that life could form on the planets and have plenty of time to develop.

&gt; it&#x27;s difficult to constrain the life of the long-lived ultraviolet dwarf starsWhat&#x27;s the upper bound on their estimate for TRAPIST-1&#x27;s age?

Typo: Ultraviolet should be &quot;ultracool&quot;. Darn autocorrect

In the Q&amp;A session they said it&#x27;s difficult to constrain the age of the long-lived ultraviolet dwarf stars once they finish the active early phase, as their lifecycle progresses so slowly. They live for more than a trillion years, compared to stars like our sun which are larger and burn through their fuel in less than 10 billion years.It&#x27;s somewhat counterintuitive, but the bigger a star is, the faster it uses up its fuel, despite having much more of it. As size increases, the rate of fusion in the star&#x27;s core increases such that the extra fuel isn&#x27;t enough to prevent the lifespan from shortening. In fact, a common type of supernova occurs in stars that are at least 8 times the size of the sun, burn through their fuel in less than 100 million years, and then go out in style.Crash course astronomy has some great videos on this stuff:
<a href="https:&#x2F;&#x2F;youtu.be&#x2F;PWx9DurgPn8" rel="nofollow">https:&#x2F;&#x2F;youtu.be&#x2F;PWx9DurgPn8</a>

&gt; trillions of yearsThis is off by several orders of magnitude. Like estimating the age of your neighbor to be somewhere around 400,000 years old.

I&#x27;d be surprised if there isn&#x27;t other microbe-like life in our own solar system. And the path from microbial to &quot;complex&quot; life is just a matter of whether the environment provides enough energy to support it (nearby sun + photosynthesis in our case). This is because cellular communities will always have certain niche advantages (homeostatis etc).Complex life developed on Earth because it is advantageous in a physics&#x2F;evolutionary sense, not because the universe accidentally slipped on a banana. Complex life is only an &quot;accident&quot; in that the search algorithm took a while to find the maxima. Otherwise it&#x27;s just a matter of running the search long enough, and for that all you need is a star.

Well, it&#x27;s &quot;at least&quot; 500m, but is probably much more[1]:<pre><code> &quot;Determining the ages of such small stars is difficult because they evolve so slowly over their lifetimes of trillions of years but it is estimated to be in excess of a half a billion years and is probably much more.&quot;
</code></pre>
And abiogenesis occurred on Earth within about 500m years of the Earth&#x27;s formation, so life can clearly arise pretty quickly. It&#x27;s complex, multi-cellular life that seems to be hard part. Although this is based on our observations of a single example.[1] <a href="http:&#x2F;&#x2F;www.drewexmachina.com&#x2F;2016&#x2F;05&#x2F;03&#x2F;habitable-planet-reality-check-trappist-1&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.drewexmachina.com&#x2F;2016&#x2F;05&#x2F;03&#x2F;habitable-planet-rea...</a>

&gt; Too young star for alien life hopes?Not necessarily -- life on Earth may have arisen a remarkably short time after accretion, perhaps even in the first few hundred million years. See this old HN discussion: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=10415212" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=10415212</a>

Moore&#x27;s Law applied to DNA complexity hints that life could be way older than Earth itself: <a href="https:&#x2F;&#x2F;www.technologyreview.com&#x2F;s&#x2F;513781&#x2F;moores-law-and-the-origin-of-life&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.technologyreview.com&#x2F;s&#x2F;513781&#x2F;moores-law-and-the...</a>

Earth is 4.5G years old, and the earliest undisputed microbial life fossils are 3.5G years old, so that gives 1000 million years.But we can also say that Earth was cool enough for liquid water 4.4G years ago, and there are some findings suggesting microbial life already 4.1G years ago. So only 300 million years, at maximum.

That&#x27;s &quot;at least&quot;; the age is a lower limit. These stars basically live forever, even in astronomical terms, and evolve extremely slowly, so all you know is that it&#x27;s not &quot;young&quot;.

Wiki says &quot;TRAPPIST-1 is an ultracool dwarf star that is approximately 8% the mass of and 11% the radius of the Sun. It has a temperature of 2550 K and is at least 500 million years old.&quot;<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;TRAPPIST-1" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;TRAPPIST-1</a>Too young star for alien life hopes?

The GP already posits a theoretical perfect fusion drive.

This estimation was already assuming a fusion engine.

What if we used engines powered by nuclear energy (fission or fusion)? Could we reduce the amount of fuel, since the energy density is so much higher?

No. If I&#x27;m not mistaken we&#x27;re in the order of magnitude of 0.0001c.

No, but we probably could with enough fuel. The bigger issue is space dust. Hitting it at relativistic speeds would be like flying into a cosmic shotgun for the entire journey.

I&#x27;ve read about laser systems for sending unmanned crafts at high speed: <a href="http:&#x2F;&#x2F;www.space.com&#x2F;29950-lasers-power-tiny-interstellar-spacecraft.html" rel="nofollow">http:&#x2F;&#x2F;www.space.com&#x2F;29950-lasers-power-tiny-interstellar-sp...</a>

If I understand our capabilities correctly we can&#x27;t even escape the solar system without using gravity assist boosts from other planets, let alone sustaining thrust for a long period.<a href="http:&#x2F;&#x2F;solarsystem.nasa.gov&#x2F;basics&#x2F;chapter4-1" rel="nofollow">http:&#x2F;&#x2F;solarsystem.nasa.gov&#x2F;basics&#x2F;chapter4-1</a>

I think we do if you look at it in terms of acceleration. As I understand it, In space there is almost 0 friction so &quot;fast&quot; is more about acceleration than &quot;top speed&quot;. In this view, 1g isn&#x27;t that fast.

We don&#x27;t have any spacecraft that can go that fast, do we?

You have a path from earth to a planet 40 lightyears away. There is a planet every K meters that can house a fuel tank to serve as a checkpoint. Let F be the amount of fuel to take a ship between two adjacent planets. Let 0 be the first and L be the last checkpoint.Suppose a rocket can hold 3F. Go to A, deposit F, and return 2 times. Next rocket goes to B, stopping at A each way to take F -- do the B trip two times. Now you have two tanks at B and none at A. Repeat like binary addition till you fill L-2 with F, then repeat for L=L-3 to L=0. Now each checkpoint except the last and next-to-last has 1F. A final ship can make the trip to the planet, build a civilization, find a fuel source and return with pics.

If you make the fuel on Mars it will take less effort to get it into orbit. It&#x27;s also a bit further up the suns gravity well.

Are we willing to use a railgun, with a rocket burn at apogee? (So one-half orbit from the starting point: without the burn, the object will hit the ground when it completes its orbit). If so, a lot less than is needed by pure rocket burns, where you have to carry all of the mass used to accelerate to orbital velocity.

The best way would be to use a space elevator pipe for this. But it&#x27;s still not feasible.

Better off Enceladus. A ship that size probably would be built in space.

How much fuel would it take to get 6 million tons of fuel off Earth into the interstellar ship?

Which begs the question, why haven&#x27;t we at least even tried to have done anything like this already?Do we really need to repeatedly spend comparable amounts of money on yet another dramatic TV special about humans traveling to Mars, as narrated by a favored celebrity? We really are running out of time. And it almost seems like it&#x27;s pre-determined to happen. :\

Is it plausible for anything we&#x27;d build to travel .998c and survive the journey?

All about funding. NASA, for example, is about 35 years behind schedule by my math, solely from funding.Now whether throwing money at a public agency would have made advancements in lensing, transistor along with propulsion technology happen quicker. Thats a tougher question that leans towards the &quot;unlikely&quot;.

The problem is far easier to state than implement.

EDIT: My math was totally wrong. 10 trillion dollars, 0.1x world GDP. (Still a lot of money though) Leaving the old text below so the replies make sense.---To move 6,000,000 megatons of fuel into low earth orbit would take 111,111 Falcon Heavy launches, at a total cost of $10,000,000,000,000 dollars. (10 quadrillion dollars, 93x world GDP)Something that takes the total global economic output of the planet a century just to lift the fuel into orbit doesn&#x27;t read as plausible in the next 50 years to me.

The rocket equation is the biggest block. Getting a constant thrust of 1g for 7.3 years is hard.It takes an incredible amount of fuel, and an incredible specific velocity.

That actually sounds... more plausible than I would have expected. Like, doable with technology I can imagine being within reach in the next 50 years even if we don&#x27;t achieve any currently-unforseen breakthroughs.

That&#x27;s 2000 chemical rockets.  The example talks about a perfect Hydrogen-Helium conversion.

What&#x27;s the math behind your estimations? Doesn&#x27;t sound so unfeasible.

Note that he&#x27;s not giving a figure for a chemical engine, but a fusion engine (sometimes termed a &quot;torchship&quot; due to the absurd power involved.) That would be strictly more efficient than VASIMR or similar. The figure would be even more ludicrous with a LOX&#x2F;LH2 engine.(I did not check his math, however.)

Upvote for doing the math, but we&#x27;re going to have to ditch traditional chemical rockets for this kind of trip. Fortunately, we&#x27;re making progress on alternatives.<a href="https:&#x2F;&#x2F;arstechnica.com&#x2F;science&#x2F;2017&#x2F;02&#x2F;nasas-longshot-bet-on-a-revolutionary-rocket-may-be-about-to-pay-off&#x2F;" rel="nofollow">https:&#x2F;&#x2F;arstechnica.com&#x2F;science&#x2F;2017&#x2F;02&#x2F;nasas-longshot-bet-o...</a>

Though that kind of performance is probably not going to come about from improvements to chemical rockets but moving to fusion. There are some promising developments on fusion reactors (see Breakthrough in Nuclear Fusion? - Prof. Dennis Whyte <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=KkpqA8yG9T4" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=KkpqA8yG9T4</a>)Guess something like that with the 100 million C gas doing the propulsion maybe?

To put that 60 years into perspective: It was 66 years between the first powered airplane flight and landing people on the moon.

Note that GP was talking about the mass of two thousand Saturn V&#x27;s, not the payload. It would take 20,000 BFR launches to put 6 million tons in orbit.

Don&#x27;t forget about space debris. Hitting anything at the posted max speed is just gonna dril a hole straight through your ship. If it&#x27;s big enough, it&#x27;ll add some nice shockwaves to really mess up your ship.

&gt; about...2,000 Saturn V rocketsOr about 670 BFRs [1].It would take 6 cycles of tripling size and&#x2F;or performance to get a single system with enough thrust to meet your 7&#x2F;42 year schedule. The Saturn V first flew in 1967 [1]; SpaceX plans to launch its Interplanetary Transport System (ITS) in 2022 or 2024 [2]. That&#x27;s an expected 60 years to triple performance.[1] <a href="http:&#x2F;&#x2F;waitbutwhy.com&#x2F;2016&#x2F;09&#x2F;spacexs-big-fking-rocket-the-full-story.html" rel="nofollow">http:&#x2F;&#x2F;waitbutwhy.com&#x2F;2016&#x2F;09&#x2F;spacexs-big-fking-rocket-the-f...</a>[2] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Saturn_V" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Saturn_V</a>[3] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Interplanetary_Transport_System#SpaceX_tentative_calendar_for_Mars_missions" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Interplanetary_Transport_Syste...</a>

Honestly that amount of mass seems doable (the hard part being a near perfect fusion engine of course).Just curious about your calculations though. Did you take into account the fact that you could eject spent helium and therefore lower your mass in transit? Assuming most of the mass is fuel, I would imagine by the time you&#x27;re arriving there would be very little mass left to decelerate.

How many Saturn V rockets have we launched in total?

Most likely several hundred quatloos&#x27; worth, I&#x27;m guessing. :DEdit: Oh, HN, you are so humor impaired sometimes.

&gt; I have no idea how much dilithium crystal would be required though.Depends on the plot needs for the ~~episode~~ journey.

Their engines don&#x27;t consume dilithium.  Rather, it&#x27;s a catalyst to the matter-antimatter reaction.

It would take 37 days at warp 6 (assuming we&#x27;re using the new warp factors established in The Next Generation). I have no idea how much dilithium crystal would be required though.

For anyone (like me) who wants to adjust the parameters while not having to deal with calculus, this[1] &quot;Space travel calculator&quot; works great.[1]: <a href="http:&#x2F;&#x2F;nathangeffen.webfactional.com&#x2F;spacetravel&#x2F;spacetravel.php" rel="nofollow">http:&#x2F;&#x2F;nathangeffen.webfactional.com&#x2F;spacetravel&#x2F;spacetravel...</a>

If we had a near-perfect hydrogen -&gt; helium fusion engine, why would we want to stop at 2,000 saturn V rockets of mass? Hydrogen is cheap AF.Also why would we only want to stop at helium, why not fuse any further?Also why would you want to stop at 1g acceleration - why not 1.5g or 2g, say? Surely living in 2g environment is okay for that period?However presumably there is no good reason for us to go there. Just because there are planets doesn&#x27;t make it worth the trip.

Your speed doesn&#x27;t affect the laws of physics you experience.

Its probably more clear to say that a constant 1G acceleration in the local reference frame takes constant fuel, but produces a progressively smaller acceleration (asymptotically approaching zero as speed in the fixed frame approaches c) in the fixed reference frame you were launched in (or of the point you are trying to reach, the logic is equivalent) because relativity.

&gt; you had a near perfect hydrogen -&gt; helium fusion engine, 
it&#x27;d take about 6 million tons of fuel (about the mass of the Pyramids of Egypt or 2,000 Saturn V rockets)That is assuming constant energy consumption to sustain 1g, but unfortunately that&#x27;s not the case, the closer you get to the speed of light, the more energy you&#x27;d need to sustain 1g, and this becomes unrealistic long before you are anywhere close to the speed of light.

What do you consider a spacecraft though. What is the payload mass ?

That actually sounds pretty achievable. Difficult, but all within the boundaries of known physics and existing human lifetimes.

I&#x27;m pretty sure he meant a probe.  Not a good idea to send a bunch of people to a planet we don&#x27;t know is habitable (and probably isn&#x27;t).

Is that just for the rockets? We would definitely need much more than that considering we would also need to carry at least a city&#x27;s worth of infrastructure, supplies, settlers, etc.

At 0.125g&#x2F;cm^3 of density, this amounts to a cube of liquid helium about 350 meters per side (43.5 million cubic meters).

If you accelerate beyond the halfway point you&#x27;re not going to be able to stop in time.

Is there any reason to accelerate to the half way point? Accelerating to .99c is much faster and would use much less fuel. It also wouldn&#x27;t make the travel time much different, to the outside observers anyway.

At first I was confused about if the star is 39 light years from earth, how come it would take just 41.8 years from the observer perspective (assuming me looking out of the window). But with pen and paper I see that you would be accelerating the first year up to speed of light, then 40 years at almost speed of light and then one year decelerating. 
What is the efficiency of some current hydrogen -&gt; helium fusion engine?

That&#x27;s correct. You wouldn&#x27;t be able to do the roundrip expedition in less than 78 years from an observer&#x27;s standpoint so you still can&#x27;t transmit information faster than the speed of light, however from the explorer&#x27;s point of view it might take a lot less time to do that as you get closer to c.If you travel at the speed of light (assuming you&#x27;re a photon or something) then time stops &quot;existing&quot; altogether and you are simultaneously at the point of origin, destination and everywhere in between. At least that&#x27;s my understanding of it.I find it both exciting and depressing at the same time, it means that you could potentially make a rountrip to the center of the milky way and back within a human lifetime but by the time you&#x27;ll be back everybody that remained on earth would be long dead and nothing would be the same anymore. If those types of travels become common then society would stop existing on a single timeframe. It&#x27;s pretty mind boggling.

I don&#x27;t understand how it could be less than 39 years for the traveler. Time dilation is a thing, but being less than 39 years would mean the traveler observed the planet approaching faster than the speed of light, which should be impossible.Or does space contract as well?

wouldn&#x27;t it be better to plot a course where pitstops could be made at gas giants?

For others who don&#x27;t know how much an American ton is, 6 mil of them = (5.44 * (10^9)) kilograms.

I didn&#x27;t get the same result. I used the relativistic rocket equation [1], and the change in rapidity from 0 to 0.998c is about 3.5, which means a total change of rapidity of about 7 (static to full speed and then back to static). Assuming perfect hydrogen-&gt;helium fusion engine (specific impulse=0.12c) the ratio between initial mass and final mass is 10^25. For comparison the mass of the earth is about 0.6*10^25, or in other words, if you want to send only 2kg of load to this star, you need fuel as much as the mass of the earth.[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Relativistic_rocket" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Relativistic_rocket</a>

To get a spacecraft there it would take:Accelerating at 1g the 1st half, and decelerating at 1g the 2nd half, the traveler would experience 7.3 years of time. For observers it would take 41.8 years at a max speed of 0.998cIf you had a near perfect hydrogen -&gt; helium fusion engine, it&#x27;d take about 6 million tons of fuel (about the mass of the Pyramids of Egypt or 2,000 Saturn V rockets)

&gt; then it&#x27;s more likely it lies in our future (e.g. global thermonuclear war, plague, difficulty of space travel, etc)Difficulty of space travel is one of the possible filters.

Actually, the article explicitly calls out that step as one potential &quot;great filter&quot;. It also (click the link) lists the theoretical ways it could be accomplished.It seems to leave out the Von Neumann Probe:<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Self-replicating_spacecraft" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Self-replicating_spacecraft</a>This is not exactly colonization but possibly an easier step. Either way, the point is that if either we or our machines can get to another star system and repeat the process from there, exponential growth means it pretty much doesn&#x27;t even matter how long it takes. In astronomical time, we&#x27;d cover the galaxy in the blink of an eye.

The theory as described in your link seems to hand-wave away the difficulties incumbent in the &quot;colonization explosion&quot; step. As it stands, intergalactic space travel (at scale) is utterly inconceivable in practical terms, and to simply assume that it is inevitable seems like a major flaw in the theory.

That&#x27;s almost equally depressing. &quot;Really, we&#x27;re the best the universe has to offer?&quot;

Isn&#x27;t that highly unlikely due to the age of the universe vs age of the Solar System?

But what if we are the first and no filter exists at all?

Great link, thanks.Cant help but be reminded of the premise of the Halo games, and the objectives of the alien race.

The &quot;Transcension Hypothesis&quot; is a possible solution to the Fermi Paradox...<a href="http:&#x2F;&#x2F;www.sciencedirect.com&#x2F;science&#x2F;article&#x2F;pii&#x2F;S0094576511003304" rel="nofollow">http:&#x2F;&#x2F;www.sciencedirect.com&#x2F;science&#x2F;article&#x2F;pii&#x2F;S0094576511...</a>

Uh oh.The &quot;great filter&quot; hypothesis is essentially that the rarity of intelligent life has to be explained by some parameter of the Drake equation, and that whatever the &quot;small&quot; parameter is is either in our past or in our future.If the &quot;great filter&quot; is the rarity of habitable worlds, then clearly we don&#x27;t need to fear it, since we already found one. But if habitable worlds aren&#x27;t rare, then it&#x27;s more likely it lies in our future (e.g. global thermonuclear war, plague, difficulty of space travel, etc).Thus things like discovery of exoplanets, bacteria on mars, etc should make us rather concerned.<a href="https:&#x2F;&#x2F;en.m.wikipedia.org&#x2F;wiki&#x2F;Great_Filter" rel="nofollow">https:&#x2F;&#x2F;en.m.wikipedia.org&#x2F;wiki&#x2F;Great_Filter</a>

The article mentions the star being an ultra-cool dwarf star, but doesn&#x27;t give an explanation of what that means. Here&#x27;s some info from Wikipedia that I found useful:TRAPPIST-1 is an ultracool dwarf star that is approximately 8% the mass of and 11% the radius of the Sun. It has a temperature of 2550 K and is at least 500 million years old. In comparison, the Sun is about 4.6 billion years old and has a temperature of 5778 K.Due to its mass, the star has the ability to live for up to 4–5 trillion years ...<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;TRAPPIST-1" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;TRAPPIST-1</a>

Yes, in all bayesian likeness this is a class of star systems that populates the universe. Suddenly the universe does not seem so dark and foreboding anymore.

It&#x27;s not just that one. The vast majority of stars, by number (but not by light), are stars like these. The universe might dim, but it won&#x27;t be dark for a long, long time.

Don’t worry, in five billion years that will be some other Earthling’s problem.

The optimism in this thread regarding the practical feasibility of long-distance space travel is encouraging. I truly hope it&#x27;s just another hurdle for us to technologically overcome, rather than an insurmountable barrier.Even if it weren&#x27;t doable, who knows what kind of destiny awaits us as our mastery over physics advances.

&quot;Due to its mass, the star has the ability to live for up to 4–5 trillion years&quot;So when the rest of the universe cools off and stars start to die, Trappist one keeps on shining and shining... We need to get there. But first, let&#x27;s get rid of our genocidal tendencies.

Hah, called it: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=13698672" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=13698672</a>

Probably used jet airplane more of a frame of reference for the general public.

That is exactly what I meant, thank you for the link. I defiantly would support projects like that.

18k years is a very long time, though. There is a project looking at the feasibility of getting very small probes somewhere 10 times closer in perhaps decades rather than millennia:<a href="https:&#x2F;&#x2F;www.nytimes.com&#x2F;2016&#x2F;04&#x2F;13&#x2F;science&#x2F;alpha-centauri-breakthrough-starshot-yuri-milner-stephen-hawking.html" rel="nofollow">https:&#x2F;&#x2F;www.nytimes.com&#x2F;2016&#x2F;04&#x2F;13&#x2F;science&#x2F;alpha-centauri-br...</a>

Unless you&#x27;re talking about a Starshot-type probe, I think it&#x27;s probably better to wait for improved propulsion technology that would end up arriving before a probe we sent now.

Based on Voyagers current speed it would take approximately 18000 years to reach this system, the referance of a jet airplane taking millions of years seemed a bit misleading, with current technology and using gravitational boosting I would think that the time could be much less. Maybe it would be worth sending a probe? Granted I will never see it in my lifetime but it might be a project I could get behind.

Once again, the universe shows that not only is it strange, it&#x27;s stranger in ways we can&#x27;t possibly imagine. This is truly a golden age of space science and, as Kay said in M.I.B., &quot;I wonder what we&#x27;ll know tomorrow.&quot;.

It&#x27;ll be interesting to see this reflected in the Drake equation (average number of planets per star that can potentially support life).It&#x27;d be amazing if the number was above 1 (or terrible if you believe in the Great Filter hypothesis).

What&#x27;s wrong with begs the question?  It&#x27;s a regular part of my vocabulary and I&#x27;m a southern American.

It&#x27;s an incorrect and jarring usage of the phrase.  Plenty of folks on HN are non-native speakers who benefit from knowing when colloquialisms are used incorrectly.

That&#x27;s essentially what blueprint said. You didn&#x27;t have any trouble figuring out what blueprint was saying, right?

We detached this subthread from <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=13707913" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=13707913</a> and marked it off-topic.

I don&#x27;t think we know for sure, but it&#x27;d be hard to place another star in the system and have it a) not disrupt the planets and b) go unnoticed as the primary star is so faint.

Is it possible there isn&#x27;t an asteroid belt to be concerned about?

Do we know definitively that there are no other planets in this system?The presence of a large, Jupiter-sized planet in a system is thought to be helpful for deflecting asteroid impacts. Obviously we are talking &#x27;to scale&#x27; given TRAPPIST-1 itself is around the size of Jupiter!The more we learn about this system is going to be fascinating though - the supposed inward migration of these planets may even help us understand more about how our own system formed.

The moon rotates once every ~27 days, so its day is ~27 days. It&#x27;s just in sync with its orbit of the earth, so it appears to us that it doesn&#x27;t rotate.<a href="http:&#x2F;&#x2F;www.space.com&#x2F;24871-does-the-moon-rotate.html" rel="nofollow">http:&#x2F;&#x2F;www.space.com&#x2F;24871-does-the-moon-rotate.html</a>

If they are tidally locked as reported, then there will be no day, not really. Just as there is no day on the moon.

&gt; Because the planets are so close to Trappist-1, they have quite likely become “gravitationally locked” to the star, always with one side of the planets facing the star, much as it is always the same side of Earth’s moon facing Earth.Also, during the live stream they said that the furthest planet does a complete orbit around the star in 20 Earth days.So there are likely no &#x27;days&#x27; on any of these planets and a &#x27;year&#x27; goes by in less than a month on Earth.

Close orbit around a relatively cold star. Interesting. I wonder what their &#x27;day&#x27; vs &#x27;year&#x27; looks like. Also their atmosphere and surface pressure. They could be 7 copies of Venus for all we know.

We could catch it and use as a fuel or recoil mass!(does napkin math)Nope :-(

It&#x27;s almost all Hydrogen&#x2F;Helium gas. Other larger atoms and molecules are known to exist in the interstellar medium, but it&#x27;s primary gas.Also, a good way to remember the density is ~1 Hydrogen atom per cm^3.

I&#x27;m having a hard time finding more data on the density of matter in interstellar space.Wikipedia says&gt; The density of matter in the interstellar medium can vary considerably: the average is around 10^6 particles per m3 but cold molecular clouds can hold 10^8–10^12 per m3 [1]But I imagine that interstellar gas would be easier to fly through than interstellar sand. Do we know the composition of matter in interstellar space?[1] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Outer_space#Interstellar_space" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Outer_space#Interstellar_space</a>

Seven earth-sized planets discovered circling a star 39 light years from Earth