Further Thoughts on TRAPPIST-1

by Paul Gilster on February 23, 2017


In yesterday’s news conference on the seven planets around TRAPPIST-1, exoplanet scientist Sara Seager (MIT) pointed to the discovery as accelerating our search for habitable worlds. “Goldilocks,” Seager said in a finely chosen turn of phrase, “has many sisters in this system.” I think she’s exactly correct, even though we don’t yet know if any of these particular worlds house life. For as Seager went on to point out, we now need to study the atmospheres of these planets to find out what’s really going on, especially on potentially habitable TRAPPIST-1e, f and g.

Seager’s enthusiasm for TRAPPIST-1 is based on the fact that, whatever we eventually learn about its planets, we’re seeing such an abundance of possibilities here that similar, possibly life-bearing systems are doubtless commonplace. And with this system, we have transiting worlds in the solar neighborhood whose atmospheres can be analyzed by upcoming missions like the James Webb Space Telescope, or via installations on the ground like the soon to be available European Extremely Large Telescope. We’re swiftly moving to a place where the active search for biosignatures in distant atmospheres becomes a regular activity.


Image: This artist’s concept shows what the TRAPPIST-1 planetary system may look like, based on available data about the planets’ diameters, masses and distances from the host star. Credit: NASA-JPL/Caltech.

Those atmospheres, of course, are a cause of concern when planets are in such proximity to a young star. Yesterday I pointed to a paper, one of whose co-authors was Michaël Gillon (STAR Institute, University of Liège), a key player in all of the TRAPPIST-1 planetary findings. Noting the opportunity these planets present for atmospheric analysis, the authors discussed the X-ray and ultraviolet radiation that could damage planetary atmospheres. I notice that Lisa Kaltenegger (director of the Carl Sagan Institute at Cornell), shares radiation concerns.

Kaltenegger has already homed in on the problem with two papers currently in the works on how life would fare in a high ultraviolet radiation flux environment. Her take:

“How good or bad would such a UV environment be for life? Our paper, currently under review at Monthly Notices of the Royal Society, discusses just this scenario for the Trappist-1 system, examining the consequences of different atmospheres for life in a UV environment. We find that if the star is active, as indicated by the X-ray flux, then planets need an ozone layer to shield their surface from the harsh UV that would sterilize the surface. If the planets around Trappist-1 do not have an ozone layer (like a young Earth), life would need to shelter underground or in an ocean to survive and/or develop strategies to shield itself from the UV, such as biofluorescence.”

Notice that Kaltenegger is not ruling out life even under strong radiation constraints. We know from our own world how adaptable life can be, and we can’t rule out the possibility that even a young flare star could serve as an evolutionary spur to forms of adaptation and protection. We also know nothing of possible magnetic fields on these worlds. So I come back to Seager’s point: We now need to study these atmospheres to go beyond theory to observation.

About the worlds themselves, I noticed in the paper that Michaël Gillon and colleagues wrote for Nature that the planetary orbital inclinations found at TRAPPIST-1 are all very close to 90°, which tells us we’re looking at a system that is ‘dramatically co-planar,’ and we’re seeing it nearly edge-on. What a spectacular opportunity this gives us. The authors tell us that the six inner planets are moving in resonance with each other, which can be deduced from transit timing variations (TTVs). This is of more than theoretical interest because it goes to the origin of these planets, and hence to their possible composition. From the paper:

Orbital resonances are naturally generated when multiple planets interact within their nascent gaseous discs. The favoured theoretical scenario for the origin of the TRAPPIST-1 system involves accretion of the planets further from the star, followed by a phase of disc-driven inward migration — a process first studied in the context of the Galilean moons around Jupiter. The planets’ compositions should reflect their formation zone, so this scenario predicts that the planets should be volatile-rich and have lower densities than Earth, in good agreement with our preliminary result for planet f…

In other words, we’re dealing with worlds that likely migrated in from much further out in the planetary system, meaning they formed beyond the ‘snowline,’ where ice should have been plentiful. That bodes well for possible water on the surface, depending on what we find through our atmospheric studies. TRAPPIST-1 gives us what Seager referred to as a ‘laboratory’ to study planets around red dwarfs. Here we can test out questions of tidal lock and radiation as we perform follow-up work with Hubble, Spitzer and other instruments, all the while awaiting the chance with the James Webb instrument to analyze planetary atmospheres. Transmission spectroscopy, after all, can detect water, methane, oxygen.


Image: An artist’s conception of the view from the surface of TRAPPIST-1f like this might easily have run as the cover on a 1950s issue of Hans Stefan Santesson’s Fantastic Universe, or maybe one of the large-size Analogs from the early 1960s. Now we’re learning that places like this are really out there. Credit: NASA/JPL-Caltech.

Meanwhile, I can’t help but think in terms of science fiction, and how well the image above would have fit on many a novel dust jacket or magazine cover. From one of these planets, we can look up and see other planets close enough to spot geographical features and cloud patterns. If life emerges on one of these worlds, it can surely move between them, as we know from the presence of so many Martian rocks that have made their way to the Earth. And if a civilization might arise with views like these, what a spur toward the development of technologies to go into space and visit not one but a host of compelling neighbors!

The paper is Guillon et al., “Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1,” Nature 542, 456–460 (23 February 2017). Abstract.


{ 63 comments… read them below or add one }

Harry R Ray February 23, 2017 at 10:25

NOT SO FAST!!!!! Anyone who sees this comment should IMMEDIATELY google(by the way, TRAPPIST-1 is the google DISPLAY today-check it out)http://www.oklo.org. In his latest posting, Greg Laughlin states that there is ONLY A 60% chance that TRAPPIST-1d is a main sequence star. There is a 40% chance that, instead, it is a Brown Dwarf that has JUST RECENTLY REACHED ITS MAXIMUM LUMINOSITY! If this is the case, Oxygen in the planets’ atmospheres’ will NOT be NEARLY depleted as if they had to suffer under MUCH HIGHER TEMPERATURES in their infancy!!! IF JWST detects abundant oxygen in their atmospheres, ALL BETS ARE OFF for the GLOOMY prognoses of no primitive life on some of these worlds.


Paul Gilster February 23, 2017 at 10:33

Greg Laughlin is always worth reading. Here’s the relevant paragraph from his post today:

“2MASS J20362926-0502285, now much better known as TRAPPIST-1, straddles the boundary between the lowest mass main sequence stars and the highest mass brown dwarfs. Depending on precisely what its mass and metallicity turn out to be, it could either be arriving at self-sustaining core hydrogen fusion, which would make it a main sequence star (about a 60% chance) or it could be currently achieving its peak brown dwarf luminosity and bracing for a near-eternity of cooling into obscurity (about a 40% chance).”

Also quite interesting here is his take on the future of this system, assuming TRAPPIST-1 is indeed a main sequence star:

“An object with solar composition and 0.08 solar masses never turns into a red giant. As time goes on, it maintains a near-constant radius, and slowly burns nearly all of its hydrogen into helium. In roughly 10 trillion years, TRAPPIST-1 will reach a maximum temperature of ~4000K, pushing it briefly toward K-dwarf status for a few tens of billions of years, before eventually running out of fuel and fading out as a degenerate helium dwarf.”


Bruce Mayfield February 23, 2017 at 18:07

Thanks Harry and Paul for alerting us to and quoting the exoplanet expert Greg Laughlin. This question of whether TRAPPIST-1 is a star or a brown dwarf is huge.

I think Greg has now edited the paragraph you quoted Paul, adding that if TRAPPIST-1 is a star it will have a 12 trillion year lifetime on the main sequence.

So it will heat these balmy planets for a virtual eternity, or it’s already a cooling ember. VAST difference in outcomes!



Harry R Ray February 24, 2017 at 10:38

Would it be possible to determine the TRUE MASS(and thus resolve the star-brown dwarf conundrum ONCE AND FOR ALL)of TRAPPIST-1 in a few years JUST by observing IN GREAT DETAIL, the interaction of all the planets with EACH OTHER? Here’s my line of reasoning:A DIFFERENCE of, say; 0.065 and 0.075 solar mass would result in VERY SMALL DIFFERENCE in distance between the orbits of each planet. This would affect the time of transit and secondary eclipse data RECEIVED ON EARTH due to the speed of light discrepancy due to the distance VARIATION with respect to the POTENTIAL lesser mass of the PARENT BODY, if indeed it were a Brown Dwarf. If this IS possible, with the ADDED(hopefully) Kepler data, JWST secondary eclipse detections for ALL OF THE PLANETS, and the MUCH ANTICIPATED TESS and PLATO observations, we should know one way or the other in about ten years,


Ashley Baldwin February 24, 2017 at 14:31

And at some point in the distant future may represent the last haven of life in a fossilised , burnt out universe . This while enjoying a multi billion year stable Renaissance as a temperate hypothesised “blue dwarf” . Interesting to see what effect that has on the current planetary system provided its finely poised resonance hasn’t subsided long before .


Harry R Ray February 27, 2017 at 20:59

Paul Gilster: Have you contacted Dan Wertheimer recently regarding updates on his “evesdroppingSETI” project? He must be literally chomping at the bit to analyze the TRAPPIST-1 data so he can observe when two “habitable zone” planets are directly lined up with Earth! Unlike his previous efforts, which could take MONTHS for a proper alignment to take place, SEVERAL could take place ON ANY GIVEN WEEK for TRAPPIST-1! You may want to even ask him to do a guest post on this subject sometime soon!


Paul Gilster February 27, 2017 at 21:27

I’d love to have a guest post from Dr. Wertheimer. Good idea!


Harry R Ray February 28, 2017 at 10:22

If he DOES agree to do one, please ask him if the INITIAL ATA observation of the TRAPPIST-1 system had such an alignment during the time series. The odds for are not that good, but the odds against are not that overwhelming, either.


Horatio Trobinson February 23, 2017 at 10:37

One consideration I haven’t seen discussed anywhere yet is that even if these planets are tidally locked, that doesn’t mean that their dark side is perfectly dark.
The dark sides are more likely to have irregular periods of penumbra made from light (and radiation) reflected by every planet’s next outer planet.

Not quite like a full Moon is witnessed from Earth because of the fainter glow of TRAPPIST-1, but the capacity for reflectiveness increases with distance from the star, if water ice is present on the outermost planets.

And if planetary migration from the snowline zone of the original disc was indeed how the system was formed, the likelihood of having more reflective outermost planets is greater than zero.

Those are interesting ifs, but by no means unlikely ifs.


George King February 23, 2017 at 16:28

With the star/brown dwarf radiating mostly in the infrared, I wonder then whether the thus reflected radiation might have some periodic warming effect on at least a portion of the dark side of an interior planet. Even if otherwise mostly “dark” to our own visual acuity.

Also, if a tidally locked interior planet is subject to libration like the Moon, then more than 50% of its surface — during each relatively brief duration orbit — potentially would receive direct stellar irradiance. According to Wikipedia, lunar libration allows us to see 59% of the lunar surface from Earth over time.

A combination of such effects might help avoid the prospect of a totally frozen dark side, or at least reduce its scope and duration in certain areas.

I remember seeing a reference somewhere here on Centauri Dreams to a study that cut against the concept that tidally locked planets necessarily would be frozen on the dark side.

Yes, lots of interesting ifs.


George King February 23, 2017 at 16:38

And would any such libration be magnified by the multi-body situation presented around TRAPPIST-1, in comparison to the only single body orbiting the Earth?

They were talking at the press conference about how they measured how much each planet was tugged on by the others in its orbit, in determining mass, etc. If that “tugging” induced more oscillation/libration in the planets, perhaps that would periodically expose more of the dark side of the planets to stellar irradiance, in comparison to that 59% value for our Moon.


David A. Hardy February 23, 2017 at 12:03

NASA/JPL-Caltech is not an artist! It has been suggested that some of these images are mine, but not so. However, artists DO deserve to be credited, their work is so important in visualising these new worlds.


Paul Gilster February 23, 2017 at 15:54

I certainly agree. Unfortunately, the JPL press materials did not give the artist’s name. I’m with you that they should have.


David A. Hardy February 23, 2017 at 16:28

I know, they never do and it’s all wrong!


Raj Pillai February 24, 2017 at 4:24

David, Agree 100%…
The least they can do now is go back and give those artists credits in a separate press release.. Were those artists commissioned by JPL/CalTech just for this announcement/discovery?.. and waived use of credits.. ?.
Raj Pillai


Alex Tolley February 23, 2017 at 12:06

Regarding the atmospheric characterization. On Earth, the great oxidation event didn’t get going for over 3 billion years since its formation. Nevertheless, oxygen was present at very low partial pressures coincident with photosynthetic life.

My question is this: how sensitive are spectrographic analyses of these planets likely to be. Could we detect low oxygen levels, potentially hinting at photosynthetic life, or do we need planets where photosynthetic life is both abundant and the O2 sinks depleted so that O2 reaches much higher partial pressure?


jonW February 23, 2017 at 12:23

According to the datasheet here http://www.spitzer.caltech.edu/images/6282-ssc2017-01e-500-Hours-of-Spitzer-Observations-of-TRAPPIST-1 it looks (to the eye! I didn’t see it confirmed) like the orbits of b, c, d and e are in an 8:5:3:1 resonance. It seems like I’ve seen ratios like these in other systems – is there any reason to get Fibonacci-like recurrences or is my mind over-actively pattern-finding?


Geoffrey Hillend February 23, 2017 at 17:08

If we are seeing all the planets edge on we should be able to do transit spectroscopy which is the subtraction of the light of a planet not in front of the star from the planet in front of the star, or star plus planet and what is left over is the spectroscopy of the planets atmosphere.

It might be possible to do a spectroscopic half life of the elements in the star which would give an age to the star.

Interesting that the conclusions of the scientists of TRAPPIST-1 are the same as the Centauri Dreams comments on Proxima B about life needing ozone or with out ozone needing an ocean to protect it from the x-rays and UEV.

Hopefully, we can get some information about the spectroscopy of planets around red dwarf stars which will universally to other similar systems and definitely apply to Proxima B as well.


Ashley Baldwin February 24, 2017 at 14:41

Be interesting to see what the tides and currents are like in any of those putative oceans what with the extreme proximity of numerous Earth mass planets and an 80 Mjup primary .

Also , one of posited theories for the transmission of heat from day to night side of tidally locked planets is ocean currents , even under ice . A further benefit offered by M dwarfs emitting most of their “light” in the NIR is that it helps avoids the ice/albedo positive feedback that can lead to “snowball” worlds ( including Earth ) around stars emitting in shorter Sunlike wavelengths . Ice tends to absorb in the NIR thus helping resist freezing .


Ronald February 25, 2017 at 10:26

Does the tidal locking have a significant (negative) impact on the magnetic field?


Ashley Baldwin February 25, 2017 at 17:13

Very likely. It has been hypothesised that tidally locked planets can create Earth like dipole magnetic fields from convection in an outer iron / nickel core alone ( assuming it has enough iron and nickel for around the 0.32 core/planetary mass ratio of Earth and a convective lower mantle too ) . However the magnetosphere ( the stand off distance of the field from the planetary surface ) is much smaller than a field created by a planetary rotation derived dynamo as with Earth. The polar area left exposed by such a field is also much larger than for a rotational Dynamo field .

This is important as the magnetosphere needs to extend beyond any atmosphere to prevent erosion by stellar flux and is also pushed back towards the atmosphere by said stellar flux. Especially in the case of an active M dwarf which is capable of depressing it below the outer bounds of any atmosphere down even to the surface leading to atmospheric removal in a few tens of millions of years . Thus surface magnetic field strength is not in itself helpful .

Planetary Rotation rate is important with Morales-Lopez et al showing a rotation length of one day or less creating the most potent fields and extended magnetospheres . Beyond a day the field strength drops off rapidly . There also seems to be an optimum planetary mass ( depending also on core and lower mantle constiuents , mass and density ) of about 2 Me for both types of mechanism.

Larger outer core convection fields are mooted for greater than 2Me planets but tend to be multipolar with colander like holes offering much less protection to any atmosphere and planetary surface .

For active M dwarfs it’s unlikely that even the most potent rotational Dynamo and/or outer core convection magnetic fields with stand off magnetospheres of many planetary radii could withstand the stellar flux and this has also been posited for planets orbiting Sun like stars within 0.8 AU .


George King February 23, 2017 at 17:21

A system that could keep a science fiction writer occupied for a while with all the possibilities.

If UV radiation flux contributed to the widespread development of biofluorescence in life forms, that same functionality perhaps might become also a manner of communication for one or more of the life forms.

For sentient life, they perhaps would naturally develop a heliocentric type cosmology without ever first forming a geocentric type one. Given both that their planet basically always would have one face to the star/brown dwarf (without the star instead appearing from the surface to go around the planet) and further that they could see the multiple other planets with their phases obviously relating to their respective positions around the star/dwarf. Might lead to an entirely different view of their place in the universal order of things, from early on.

And given their proximity to the (albeit smaller than ours) star/dwarf and the multiple proximate planets, perhaps they would liberally use light (well, primarily in IR) sails and gravitational assists to saunter around the system.


Phil February 23, 2017 at 18:19

(Assuming the ‘star’ is on, or entering the main sequence)…10 trillion years. Think about that, that’s a HELL of a long time. To this star the universe has only just been born, and when it dies it will look TOTALLY different (and much darker).



Ashley Baldwin February 24, 2017 at 21:42

Even a 0.5-0.6 Msun , M0 dwarf has a main sequence life of about 75 billion years , over 7 times that of the Sun and 5.5 times the current age of the Universe. Such a star will eventually turn into a red giant but then remain stable for a further 5 billion years with a habitable zone around 5 AU or Jupiter’s current orbital distance . Red dwarfs are life’s redouts of the medium and long term future as well as possibly the present.

There has just been a release of 20 yrs worth of precision HIRES RV observations from Keck-1 with numerous unconfirmed planetary signals around nearby stars including a 3.8 Me Super Earth orbiting Lalande 21185 , a quiescent 5 billion year plus old M2 dwarf just 8.3 ltyrs away. (It isn’t all transit based discoveries with the additional mass estimates RV spectroscopy provides for transiting planets critical for their characterisation. ) With a ten day period not habitable but if there are similar planets ( as seems increasingly likely ) further out around 0.2 AU ( 35 -40 day period ) then things become interesting .

With third generation high res RV spectrographs like ESPRESSO and bespoke EXPRES coming on line this year to further push the discovery envelope and , in a few years there will be countless additional planetary signals /candidates to supplement SPECULOOS ,TESS and ChEOPS as the Sun’s neighbourhood is mapped out and understood in increasing detail.


Dave Moore February 23, 2017 at 20:03

I came across a chart of the radii and masses of the planets and did a quick and dirty calculation of their densities.

(Mass and radius in Earth units. Density gms/cc)
b/ 0.85 / 1.09 / 3.6
c/ 1.38 / 1.06 / 6.4
d/ 0.41 / 0.77 / 4.9
e/ 0.62 / 0.92 / 4.4
f/ 0.68 / 1.04 / 3.3
g/ 1.34 / 1.13 / 5.1
h/ ? / 0.76

They appear to be all over the place with no trend with regard to size or distance..
b has the density of Io, which would imply, at its size, it would have almost no Iron core.
c has the right parameters for a planet larger than Earth with a large iron core.
d & e look about right for terrestrial planets.

You’d have trouble explaining f without a thick atmosphere and an ice layer.

g passes muster as a terrestrial planet.

Any one of these could have a Venusian atmosphere and we couldn’t detect it from its density.


Mauldred February 24, 2017 at 9:46

I suspect f to be an ocean planet, with a thick atmosphere of water vapour keeping the temperatures well above freezing on the entire ‘surface’. And probably between the bottom of the ocean and the bedrock, a layer of ice VI or VII due the higher pressure.

This is compatible with both the inward migration hypothesis and the luminous brown dwarf hypothesis.


Ashley Baldwin February 24, 2017 at 14:47

With all the EUV and X Rays pumped out by TRAPPIST-1 most of the planets and especially larger “g” could easily be “habitable evaporated cores ” too. The lack of a thick atmospheric blanket observed on the inner planets wouldn’t exclude this, or indeed a thinner terrestrial atmosphere or just as likely, none. All options still open.


Michael February 24, 2017 at 16:19

Due to tidal heating from the effect of the other worlds Trappist 1 b may be an Io type Venus with a degassed interior and very hot surface which would bloat the atmosphere out, hence the low density for its mass.


b/ 0.85 / 1.09 / 3.6

e/ 0.62 / 0.92 / 4.4 (Waterless world with thick extended atmosphere)
f/ 0.68 / 1.04 / 3.3 (Same as Trappist b)
g/ 1.34 / 1.13 / 5.1 (Water world with thick atmosphere)

But your guesses are as good as mine, fun times ahead.


hiro February 24, 2017 at 19:14

The mass uncertainty of planet e is huge, 0.62 +/- 0.58 M Earth is not even normal in error estimate. If its mass > 1 Me then it’s Venus-like planet; on the other hand if its mass < 0.5 Me then it's Mars-type planet which has its atmosphere disappearing slowly over billions of year.

The condition of planet f depends on degree of tidal lock, star flares and gravitational effects of nearby planets (e & g). Planet g looks like the best candidate in this system even though the surface temperature is low, its thick atmosphere is good enough against star flares, small asteroids etc…


DCM February 24, 2017 at 4:35

You just never know what’s there.
Now let’s build the lunar station and Martian settlements, start mining asteroids, and begin space biosphere experiments.


Michael February 24, 2017 at 6:03
David A. Hardy February 24, 2017 at 10:47

I don’t think any artist would waive his/her credit, given a choice! But why would JPL et al do that anyway?


Alex Tolley February 24, 2017 at 16:08

Don’t commercial artists remain uncredited, e.g. advertising? Maybe JPL considers these artists as paid employees to produce output for the organization’s PR, rather than as independent artists?


Ashley Baldwin February 25, 2017 at 17:23

“The Atlantic” have an article on the image creators today . Science loving artist Tim Pyle ( formerly of Nickelodeon) and Art loving astronomer Robert Hurt from the Caltech Infrared Imaging Processing and Analysis Centre using off the shelf Lightwave 3D , Adobe After Effects and Photoshop software .


Paul Gilster February 25, 2017 at 17:53
Alex Tolley February 25, 2017 at 20:13

It’s ironic that the images are then credited to Nasa/JPL and not the artists who are the subject of the article.


Harry R Ray February 24, 2017 at 10:58

TRAPPIST-1 is in paper-a-day mode. Here’s the latest: ArXiv: 1702.07004 Reconnaisance of the TRAPPIST-1 exoplanet system in the Lyman-alpha line. by V Bourrier, D Ehrenreich, P.J. Wheatley, E. Bolmont, M. Gillon, J. De Wit, A.J. Burgasser. E. Jehin, D. Queloz, A.H.M.J. Triaud. The big result here is that despite being magnetically as active as Proxima Centauri, the TYPES of flares are not nearly as damaging to the planets’ atmospheres’ as Proxima Centauri’s would be. The authors estimate it would take SEVERAL BILLION YEARS for the atmospheres of the inner planets to be COMPLETELY STRIPPED AWAY!


Gideon Marcus February 24, 2017 at 13:14

Do these planets fit nicely into a Bode-Titian paradigm?

Thanks for a great article, as usual, Paul.


Harry R Ray February 26, 2017 at 14:52

According to David Kipping, they do! So does the Kepler 186 system if you plug in two HYPOTHETICAL NON-TRANSITING PLANETS in certain positions between Kepler 186e and Kepler 186f.


Alex Tolley February 24, 2017 at 16:12

Lots of planets packed around a sun that will burn for an extremely long time. Several of those worlds in the HZ and others relatively nearby.

What if it is an artificial system created by advanced beings? Just a fanciful, speculative thought.


David A. Hardy February 24, 2017 at 17:05

Good point. I think it’s unlikely that they have artists on their staff (none of our IAAA artists are, and I’m sure somebody would know) but it would explain it, I suppose. . .


RobFlores February 24, 2017 at 17:45

Re-estimating the average distance of a close twin of Earth;

Kepler discoveries ~3500. covering just 8 degs of sky to round off things abit. We need to correct for Kepler’s blindness to worlds 1) smaller than super terrestrials and 2) located at HZ and beyond. Here we make a assumption. that Kepler missed a potential 66% of planets that existed and transited but where not detected. we will assume that an improved version of Kepler would have spotted ~ 10,000 solar systems with at least one planet.

We are going to keep things 2 dimensional ignoring galaxy thickness.
Kepler can see about 8 degs of 360 deg of sky. 1/45 of sky

10,000 / 45 = 450,000 is the number of solar systems with at least one planet Kepler would have found IF it had 360 deg view and had more upgraded capability.

Assuming only 1.5 % of solar systems aligned to Earth for transits to occur.
The aligned and non-aligned total solar systems with at least one planet would be 450,000/.015 = 30,000,000 within 3,000 LY (kepler range)

Filtering out all M dwarfs, and Ks and G and cooler F’s type stars. retaining 20% of all stars this leaves about 6,000,000 solar systems with suns approximately like ours.

Avg = 3,000^2 x PI / 6,000,000 1 per 4.7 Ly. (alpha cent, reality check)

Filtering for Terrestrial Near twin. In earlier analysis I assumed there is an equal distribution of planets from Mars size to Mini-neptunes. Trappist hints that this is not necessarily so. For .5 RE to 2.5 RE. We will assume 1/4 of these ranges will have RE .85 – RE 1.15 which for my book is a twin of Earth. Further filtering for Habitable zone location. 1/5 (data from Trappist and other Kepler data ). Further filtering plate tectonics, (this will depend on the age of the planet) 1/3.

6,000,000 x .25 (size) x .2 (hz) x .33 (tec) ~ 100,000 Earth twins within 3,000Ly

3,000LY ^2 * PI / 79,200 = 272 LY Avg Distance to Close Earth Twin.
Probably a bit further since red dwarfs are long lived, and plate tectonics
may have died out on some worlds.

IF we dont’ filter for Reds the situation changes.
30,000,000 x .25 x .2 x .33 ~ 500,000

3,000Ly^2 x PI / 500,000 = 56 LY dist on average to Close Earth size in HZ with tectonics, with Red Dwarf star most likely.

So We can find close worlds that are much better than any planet
around OUR solar system save Earth, for habitation. since we have found
one of this type , Trappist, odds are that there is another one , probably not as generous in planetary count.

I put The odds of a true twin earth within 50 ly at about 1.5% ( which
harbors about 63 Stars somewhat close to our in size sun that are single star systems). But the good news is that every time we go out a further 5 Ly it brings substantially more suns to consider, raises that percent probability
of a twin closer to a reasonable number.


Abelard Lindsey February 25, 2017 at 0:12

All this means is that without a method of FTL:

1) All of this is irrelevant.

2) The O’neill High Frontier concept is the ONLY future in space for us.


RobFlores February 25, 2017 at 22:12

You maybe right.
If the closest ideal world for human colonization is 100’s of LY away

Any advanced tech human civilization ready to send colonists that far
will have a space infrastructure that will render the need to
spread the risk of humanity becoming extinct moot.

It would be like someone in the age of exploration sending European colonists to New Zealand in the 1500’s instead of the North/South America(relatively nearby transit with only a moderate risk of failure)

It would have to be a schism in humanity that causes a great emigration
out of the Solar System into Solar Systems 100’s of light years away. Otherwise a very slow stream of “adventurer families” would be the only candidates to emigrate, probably to a less than desirable close Red Dwarf system. I wonder if they will have the option to return if some can’t adapt.


Abelard Lindsey February 26, 2017 at 14:03

I did a rough calculation a few years ago last time I had interest in space stuff. I came up with a rough estimate that the nearest habitable planet is 75 to 100 light years away. ILet’s take the 56 LY estimate from above.

I read somewhere else (maybe here) that the maximum speed of space craft, due to interstellar gases and what not, was somewhere between 10 to 30%, with 30% being the upper limit (there goes Alastair Reynold’s lighthugger space craft). This means at least 150 year travel time to the nearest Earth like worlds. That’s doable if you put your people into cryo-suspension or something similar. However, if the upper speed is 10% light speed, then you’re looking at more than 500 years travel time. This is a bit long to me.

Robert Forward once said you never want to leave the solar system until you can get your travel time down to 40-50 years, just in case the guys back home invent warp drive while you’re in transit.


James Scanlon February 24, 2017 at 18:51

Alex ..

I’m with you ..
Pretty much checks all the “boxes” ..
A variety of usable habitats ..
Easy commuting between ‘worlds’ ..
An extremely long lived stable energy source ..
A lucky throw of the dice or intelligent design ??


Patient Observer February 25, 2017 at 1:10

Some relevant links regarding the number of planets that can fit in the habitable zone:


(5 per the above with M or K stars)


(For an artificially created planetary system, 36+ habitable worlds using gas giants each with a number of habitable moons)


Andrew LePage February 25, 2017 at 9:54

For those who may be interested, I have posted my new “Habitable Planet Reality Check” for TRAPPIST-1:



Ronald February 25, 2017 at 10:52

I said that I had a suggestion for suitable names. There happen to exist 6 official Belgian Trappist breweries and 1 Dutch (i.e. in The Netherlands, my country).
Their names are: Achel, Chimay, Orval, Rochefort, Westmalle, Westvleteren, Koningshoeven. The last one is the Dutch one and is also known as La Trappe.


Ashley Baldwin February 26, 2017 at 6:15

Sound good to me.


Patient Observer February 26, 2017 at 22:41

The next step is selling naming rights to newly discovered planets – Google-A, Sprint-B, Target-C.

As if we do not already live in a super-saturated corporation-created environment, lets keep the cosmos free of crassness. Mythology be it Western, Eastern or indigenous cultures should be enough for naming heavenly bodies.


Joshua March 13, 2017 at 20:14

Well, if naming rights were sold, the Trappist breweries would not be in the running, because they are NOT-FOR-PROFIT. All proceeds from the sale of Orval and Chimay and the nine other Trappist beers, after the small portion that is used for monastic upkeep, are donated to charity. A beer is not called Trappist if it is any other way.
I would have a great issue if someone wished to call Proxima Centauri b “Heineken”; but if they want to call the planets around TRAPPIST-1 “Orval” and “Chimay” and “Achel” etc. I think it would be fantastic.
What’s so terrible about commemorating the virtuous monastic tradition? They name asteroids after heavy metal guitarists and the like . . . . .


David A. Hardy February 26, 2017 at 4:29

Thanks. Do you have a link?


Paul Gilster February 26, 2017 at 9:39
Patient Observer February 26, 2017 at 22:34

Curious if anyone has calculated the ∆V and travel times to travel from world to world. This system is absolutely perfect for good/plausible interplanetary sci-fi story; just getting there is the problem.


Michael February 27, 2017 at 11:16

The delta V should be quite low as the Lagrange points must be closer than the moon between some of them, moving between worlds would be quite easy, I am thinking along the lines of less than 1 km/s.


RobFlores February 27, 2017 at 16:07

Clarification on Re-calculating odds of Twin of Earth nearby.
Bad statement here:
Filtering out all M dwarfs, and Ks and G and cooler F’s type stars. retaining 20% of all Stars.

“Filtering out all M. Dwarfs. Counting only Ks and G and cooler F’s type stars. retaining 20% of all stars:

I think most caught it, if not things should make better sense.

M dwarfs habitability is the crux of the proximity question.

If Neptune class planets in the HZ commonly have large moons, then we are in a bonus situation if they occur in M type stars. If said moon had an orbital period of 3-4 days, it would certainly be more habitable than ANY planet in orbit around a red dwarf. Perhaps bringing the overall odds of
an imperfect twin of Earth to within 100 LY.


Harry R Ray March 3, 2017 at 11:03

The first “Global Ocean” exoplanets have been CONFIRMED! NO! IT IS NOT ANY OF THE TRAPPIST-1 PLANETS, but more on SOME OF THEM later. The discovery paper is: “Strong HI Lyman-alpha Variations from a 11 Gyr old Host Star.” by V. Bourrier, D. Ehrenreich, R. A. Allart, A. Wyttenbach, T. Semaan, N. Astudillo-Defru, A. Garcia Berna, C. Lovis, F. Pepe, N. Thomas, S. Udry. Hydrogen exospheres have been detected on Kepler 444e and Kepler 444f with a VERY HIGH DEGREE OF CONFIDENCE!!!! There are ONLY TWO EXPLANATIONS FOR THIS! ONE: The planets have puffed up Hydrogen atmospheres and a rocky surface. TWO: The planets have deep oceans with a temperature high enough to BOIL unless their atmospheres are dense enough to have an atmospheric pressure HIGH ENOUGH to PREVENT them from boiling! This atmosphere MUST be composed of elements and/or compounds MUCH HEAVIER THAN HYDROGEN. ONE is IMMEDIATELY DISPROVED by the VERY SMALL RADII OF THE TWO PLANETS. ALSO: The recently proposed “Volcanic Hydrogen” scenario is invalid because of the AGE of the system(i.e., there would not be ENOUGH internal Hydrogen to maintain enough Hydrogen in the atmospheres of these two planets over 11 Billion years. This leaves TWO as the ONLY SOLUTION!!!!! This is EXTREMELY SUPRISING TO ME because the radius of Kepler 444e is ONLY 0.546 Earth radii(i.e., only slightly LARGER than that of Mars)! How this MAY pertain to TRAPPIST-1: The FIRST TWO authors of this paper are BOTH heavily involved with the TRAPPIST-1 team. They recently were involved in a recently published paper claiming TENTATIVE detection of Hydrogen exospheres on TRAPPIST-1b and TRAPPIST-1c, BOTH OF WHICH may host high-temperature global oceans(b WAY TOO HIGH for organic chemicals to form and c VERY questionable but possible for them to form)with dense high-pressure atmospheres.


Harry R Ray March 3, 2017 at 11:10

Actually, it IS Kepler 444e after all. SORRY!


Larrry March 6, 2017 at 14:19

Is there oxygen there?


Harry R Ray March 9, 2017 at 14:49

FREE Oxygen(O,O2,O3) has not been detected yet, but MASSIVE AMOUNTS of Oxygen are present in the water(H2O).


Harry R Ray March 9, 2017 at 12:06

BREAKING NEWS!!!!! Ethan Kruse tweeted this 15 hours ago: There are SO MANY transits in the #TRAPPIST-1 light curve. Been exausting but fun day playing with the #K2Mission data. This puts to rest FOR GOOD the concern that TRAPPIST-1 is SO RED that Kepler could NOT DETECT ANY transits of Earth-sized planets AT ALL! And this is just the UNPROCESSED VERSION. The processed version comes out in May. Could it reveal transits of objects as small as 1/3Rmars(to find out why I asked this,check out my latest comments on the latest Ceres posting on this website, and/or log onto https://www.manyworlds.space)?


Keven Bennett March 10, 2017 at 20:13

This is just a hunch, but wouldn’t it be more likely in such a crowded neighborhood that spin/orbit resonances other than 1:1 be more likely?


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