Let’s turn the clock back a bit on the TRAPPIST-1 discoveries with a reminder of Hubble work on this system announced last July. A team led by Julien de Wit (MIT) used the Hubble Space Telescope’s Wide Field Camera 3 to look for atmospheres on TRAPPIST-1b and 1c, two of the three planets then known around this star. The researchers were able to take advantage of a rare simultaneous transit, when both planets crossed the star within minutes of each other, an event that has been calculated to occur only every two years.
The result: No sign of the kind of hydrogen-dominated atmospheres we would expect on gaseous worlds. That was good news, for reasons that Nikole Lewis (Space Telescope Science Institute) explained:
“The lack of a smothering hydrogen-helium envelope increases the chances for habitability on these planets. If they had a significant hydrogen-helium envelope, there is no chance that either one of them could potentially support life because the dense atmosphere would act like a greenhouse.”
Image: NASA’s latest exoplanet ‘travel poster.’ From the JPL caption: “Some 40 light-years from Earth, a planet called TRAPPIST-1e offers a heart-stopping view: brilliant objects in a red sky, looming like larger and smaller versions of our own moon. But these are no moons. They are other Earth-sized planets in a spectacular planetary system outside our own. These seven rocky worlds huddle around their small, dim, red star, like a family around a campfire.” The poster can be downloaded here. Credit: NASA-JPL/Caltech.
This was, of course, before we knew there were seven planets in this system, but it was clear at the time that future observations would be needed to tell us what kind of atmospheres these worlds had, if any, and what their surface conditions might be. The paper in Nature also noted the need for spectroscopic analysis to look for methane or water features, all part of estimating the depth of any atmospheres on the two worlds.
I hark back to this story because we’re proceeding with exactly the kind of focused work the de Wit team was calling for in the summer of 2016. For it turns out that the discovery of TRAPPIST-1’s first three planets, and the four subsequent ones, was part of a larger project called the Search for habitable Planets EClipsing ULtra-cOOl Stars (SPECULOOS), whose goal is to search for planets in the habitable zones of the nearest 500 ultracool stars and brown dwarfs.
Its acronym created as a nod to a Flemish spiced shortbread, SPECULOOS is in the early stages of its work. At the European Southern Observatory’s Paranal Observatory in Chile, four robotic telescopes make up the observing infrastructure, each of them housing a one-meter primary mirror and cameras sensitive in the near-infrared. The project involves scientists from the University of Liège (Belgium) as well as other universities, and is under the leadership of Michaël Gillon, who has led the TRAPPIST-1 planetary discovery effort.
Thus the TRAPPIST effort (TRAnsiting Planets and PlanetesImals Small Telescopes) is actually folded into the larger SPECULOOS survey, as is a second ESO effort at Oukaïmden Observatory in Morocco. But SPECULOOS is designed to survey ten times as many red dwarfs as TRAPPIST does, and according to this ESO news release, it is expected to discover a number of systems similar to TRAPPIST-1, at least in terms of the number of planets involved, if perhaps not as fortuitously angled to give us seven transits.
Thus the Hubble work of 2016 can be placed within a larger context, the ongoing effort to survey nearby red dwarfs and brown dwarfs and determine which of these are most suitable for studying their atmospheres. By examining the mass, radius and orbital parameters of such worlds and analyzing possible atmospheres, SPECULOOS will feed future observatories like the James Webb Space Telescope and the 39-meter European Extremely Large Telescope with the target list they need.
The excitement of this ‘golden age’ of exoplanet discovery can only build as we realize that these upcoming observatories, along with missions like TESS (Transiting Exoplanet Survey Satellite) and CHEOPS (CHaracterising ExOPlanets Satellite) are not that far in the future (TESS is scheduled for launch in 2018, and CHEOPS should be ready for launch by then). Having made a statistical analysis of the broad exoplanet population with Kepler, we now turn to stars closer to home, and the possibility of finding biomarkers in their atmospheres.
Image: Planets in a compact red dwarf system. Credit: ESO.
In addition to the paper on TRAPPIST-1’s seven planets cited yesterday, I also want to cite the de Wit et al. paper referenced above, “A combined transmission spectrum of the Earth-sized exoplanets TRAPPIST-1 b and c ‘,” Nature 537, (01 September 2016), 69-72 (abstract) and Gillon et al., “Temperate Earth-sized planets transiting a nearby ultramool dwarf star,” Nature 533 (12 May 2016), 221-224 (abstract).
Arthur C Clarke is famously quoted as saying that he felt that it would ultimately be found that life was either ubiquitous in the Universe or rare bordering on non existent . Both of which he found equally terrifying .
Fear apart, the absence of life on a TRAPPIST -1 or SPECULUOOS derived planet would not necessarily exclude the latter but if life was discovered in such an exotic and apparently hostile environment ( so utterly different from Earth- something which the JPL posters convey well ) , it would surely hint at the former. And the beauty is that these systems are within technology’s near term grasp to characterise , not just some decades distant pipe dream. Indeed a golden age.
If the Trappist 1 planet you happen to be on had several moons of its own that would be a rather crowded sky. I imagine an amateur astronomer would be kept rather busy on a world like that.
This is just a question I have and don’t pretend to have an answer. If an earth type planet were in a close orbit around a red dwarf star (like these or Proxima b) what sort an effect would a good size moon(s) have on that planet being locked with one face constantly facing the star. Could a moon negate that situation. It was assumed for decades that Mercury was tidily locked until we discovered more recently that it wasn’t. Mercury does not have a moon, but our making the assumption that planets like these are tidely might be premature without enough data. If we made that error with a planet within our own system could not do the same with an exoplanet light years away?? I think you understand what I am saying. Very interest any which way you look at it,,,we have so much to learn.
A double planet (e.g. Pluto and Charon) would be tidally locked to each other but have sunrises and sunsets. None of the planets in question seem to be doubled up.
Here is a good explanation of why Mercury is not tidally locked to the sun:
http://cseligman.com/text/planets/mercuryrot.htm
Could be an issue in small M dwarfs certainly. I’m no astrophysicist , but as I understand it the “Hill” radius is the area of gravitational influence of a planet over that of its parent star. The nearer to said star the planet that is , the smaller the Hill radius becomes till so small that the planet can’t sustain a moon and for really close proximity is also subject to direct and substantial gravitational tides.
That’s before factoring in the additional none negotiable influence of extremely close Earth mass planets to boot. This system is a gravitational Gordian knot, regardless of stable resonant orbits .
Another issue is the fact that it’s believed that the planets may have migrated in from further out which would disrupt any moons the planets may have possessed in a more stable gravitational milieu.
Tom, if we are going to consider postage-sized planetary systems around red dwarf stars, we may find instances of two planets tidally-locked in relationship to each other orbiting around a common center of gravity so that they are not locked in relationship to their star. So we might have planets with days and nights that each take up a goodly percentage of each orbit around their star. That certainly would have a major effect on the lifeforms of such planets. Perhaps day lifeforms and night lifeforms?
For those who may be interested, I have posted my new “Habitable Planet Reality Check” for TRAPPIST-1:
http://www.drewexmachina.com/2017/02/25/habitable-planet-reality-check-the-seven-planets-of-trappist-1/
Thanks . Great review as ever and perhaps the most positive to date within the bounds of data available .
What an incredible piece of good fortune that Kepler is currently observIng a star field for near three months that includes TRAPPIST-1 and increasing the number of recorded transits from 92 to 220 plus . That should refine the transit data dramatically just in time for JWST to take over . NIRSPEC awaits . The frequent and deep planetary transits will also help compensate for the star’s low magnitude, even in the preferred near infrared. All options still apply, but clearly e, f and g hold great promise not just for habitability but for understanding the nature of M dwarf planetary systems as a whole. It’s difficult to overstate its importance . It might indeed be a golden age for exoplanet science but it promises to be rose tinted .
A general question. Are flares on dim red dwarf stars at a higher temperature than the typical surface temperature?
Yes. Higher energy flare EUV and X-Ray radiation arise from higher temperatures created by stellar flux trapped within convection driven entwined magnetic fields . ( and released when they snap )
It will be interesting to see if the planets positions and alignments effect the flares on TRAPPIST-1. A little out of the box thinking, could the flares be closer to the poles in red dwarfs, would the magnetic dwarf-spots be in the same locations that Jovian auroral flares are at?
That’s very interesting, Ashley Baldwin. Without a moon, an exoplanet will have a wide axial tilt over time which might give it extreme weather changes over time. That might make it harder for life to adapt but not impossible.
It remains to yet to be known that in order for a planet to have a strong magnetic field to deflect the solar wind, it must have a collision with a Mars sized body to give it a large iron core and the necessary angular momentum to give it a fast rotation. If this is true, exact Earth twins need a Moon and need to be further away from their stars so they are limited to G and K type stars.
I’m not sure about the TRAPPIST-1 system with its complex interplanetary gravitational intersections but the process of planetary tidal locking apart from leading to one side facing the star also leads to “circularisation ” of the orbit and negligible obliquity . Illustrated nicely by Jupiter’s moons to which this system has already been compared for other reasons.
Good point about varying tilt for moonless non synchronised planets . Jim Kasting looked at this ( with Mars as a comparator ) in his book “How to make a habitable planet” and did find a range of small and stable obliquities a terrestrial planet could adopt without the influence of a large moon. That was largely as a rebuttal of the recently published “Rare Earth ” which suggested a stable and not excessive orbital tilt was a key element in the development of intelligent life on Earth . Since then numerous studies have been done looking at a wide range of obliquities and certainly shown that a planet could in theory be habitable even with extreme and fluctuating values . ( “intelligence” as we understand it is probably a matter apart )
What would evolve in such a milieu is anyone’s guess but it’s certainly no more exotic a setting than the outer TRAPPIST-1 planets. All options still open…..
If we look at the velocity of these worlds they are quite high for the light flux they get which means higher impact velocities and that does not bode well for advanced life.
Perhaps the role of a large moon for tilt stabilization is replaced in tightly packed systems like this by the nearness of the other planets.
And even more importantly, the nearness of the 80 Jupiter mass star they orbit. Close in worlds motions should get “locked-in” in more ways than one.
Hats off to Professor Gillon and the University of Liege. Rapidly becoming a centre of excellence in exoplanet science as they have also developed impressive new coronagraphs for direct imaging too.
If you look at the original poster submission in which Gillon kicks off the entire TRAPPIST/ SPECULOOS programme he accurately predicts Jupiter moon like planetary systems around low mass M dwarfs , with sufficient strength to win the grant that builds not one but four bespoke 1m telescopes for the task. No mean feat and entirely vindicated already.
Greg Laughlin strikes again! In his latest posting on the systemic website, there is an illustration depicting a TRIPLE TRANSIT(two of the three planets in the habitable zone)captured by the VLT in DECEMBER 2015!!! Gillon et al MUST HAVE KNOWN that they had A LOT MORE THAN JUST THREE PLANETS way back then!
I wonder how far into the future they’ve projected the orbits and whether fatal instabilities lurk in the short- and medium-term. One would need decent accuracy for such predictions to be trustworthy, of course.
The giant impact hypothesis includes the idea that a Mars sized object shattered into many smaller pieces after it hit the Earth. Some of the Iron came out of Theia and went into the core of Earth giving it a large Iron core and the angular momentum needed to have a strong magnetic field. The idea is that even a planet with a large iron core without a rotation as fast as Earth’s will not have a strong enough magnetic field to block the solar wind which would result in the planet losing it’s atmosphere over the long term from being stripped by the solar wind.
This sounds like an unnecessary limitation but science works that way. If intelligent life can only evolve on Earth like planets with moons the size of our own life would be rarer but not that rare. There still would be a lot twin systems like ours. Consequently, if a planet does not have a Moon then it might not have strong magnetic field. This could be wrong but it makes sense to use Earth as a model for what is crucial to have a magnetic field Venus is a good example of slow rotation and no magnetic field.
There is still the idea that an Earth sized planet could have a large magnetic field and fast rotation without a Moon but that remains to still be seen. Mars has a rotation as fast as Earth but it is a smaller planet with less mass. Also we might be able to see if any of the exoplanets around TRAPPIST-1 have a magnetic field since they are seen edge on. Astronomers might be able to determine the size of the bow shock or if any hydrogen cloud is trapped in the magnetic field by it’s transit in front of the star.
Venus is has a density of 5250 kg/m3 ( Earth 5520 kg/m3) with probably a liquid Iron core but no magnetic field.
“Alien Worlds Could Be Habitable Around Small Red Suns for Up to 11 Billion Years”
March 06, 2017
All throughout the universe, there are stars in varying phases and ages. The oldest detected planets found using NASA’s Kepler telescope are about 11 billion years old, and the planetary diversity suggests that around other stars, such initially frozen worlds could be the size of Earth and could even provide habitable conditions once the star becomes older. Astronomers usually looked at middle-aged stars like our sun, but to find habitable worlds, one needs to look around stars of all ages.
“Worlds could become habitable around small red suns for billions of years, maybe even starting life, just like Earth. That makes me very optimistic for the chances for life in the long run,” says Lisa Kaltenegger, associate professor of astronomy at Cornell, and director of the Carl Sagan Institute.
In their work, Ramses M. Ramirez, research associate at Cornell’s Carl Sagan Institute and Lisa Kaltenegger, associate professor of astronomy and director of the Carl Sagan Institute, have modeled the locations of the habitable zones for aging stars and how long planets can stay in it. Their research, “Habitable Zones of Post-Main Sequence Stars,” is published in the Astrophysical Journal.
Full article here:
http://www.dailygalaxy.com/my_weblog/2017/03/worlds-could-be-habitable-around-small-red-suns-for-billions-of-years.html
To quote:
“When a star ages and brightens, the habitable zone moves outward and you’re basically giving a second wind to a planetary system,” said Ramirez. “Currently objects in these outer regions are frozen in our own solar system, and Europa and Enceladus – moons orbiting Jupiter and Saturn – are icy for now.”