We’re pretty sure that all seven are rocky worlds, like the Solar System’s inner planets.
Three are in the star’s habitable zone. The inner two definitely do not have one sort of atmosphere that would make life as we know it impossible.
Even if we don’t find life there, we’ll learn a great deal while looking.
- Size, Comparisons, and a Little Math
- Alien Life, Tourists, and Robots
- Voyage to a Distant Star
- Beyond Setting Records
TRAPPIST-1 is a small, very dim, very cool, star. Its diameter is about 158,600 kilometers, bigger than Jupiter’s 142,900, but not by much. TRAPPIST-1 b through h orbit very close to their sun.1
We know how big the TRAPPIST-1 planets are, but not what they look like.
Like I said, we don’t know if there’s life on any of them; or even if it’s possible.
Truth cannot contradict truth, being curious is a good idea, and scientific discoveries are opportunities for greater admiration of God’s creation. (Catechism of the Catholic Church, 159, 214–217, 283, 294, 341)
I’ve been over that before, too. Quite often, actually:
- “Epiphany Sunday”
(January 8, 2017)
- “Making a Universe: Why Bother?”
(January 29, 2017)
- “Right-Handedness and Evolving Jaws”
(October 28, 2016)
- “Alchemy, Science, Life, and Health”
(October 16, 2016)
“…TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) is a project led by the Department of Astrophysics, Geophysics and Oceanography (AGO) of the University of Liège (Belgium), in close collaboration with the Observatory of Geneva (Switzerland). TRAPPIST is mostly funded by the Belgian Fund for Scientific Research (FNRS) with the participation of the Swiss National Science Foundation (SNF).
“The team is composed of Emmanuël Jehin, Michaël Gillon, Pierre Magain, Virginie Chantry, Jean Manfroid, and Damien Hutsemékers (University of Liège, Belgium) and Didier Queloz and Stéphane Udry (Observatory of Geneva, Switzerland).
“The name TRAPPIST was given to the telescope to underline the Belgian origin of the project. Trappist beers are famous all around the world and most of them are Belgian. Moreover, the team members really appreciate them!”
(eso1023 — Organisation Release (June 8, 2010))
“Trappists” is what folks call monks in the Order of Cistercians of the Strict Observance. If you’re into Latin acronyms, that’s O.C.S.O.: Ordo Cisterciensis Strictioris Observantiae. They’re contemplative monks and nuns, part of the Benedictine family. (August 14, 2016)
“What Would Life Be Like on the TRAPPIST-1 Planets?”
Calla Cofield, Space.com (February 24, 2017)
“The TRAPPIST-1 system is home to seven planets that are about the size of Earth and potentially just the right temperature to support life. So how would life on these alien worlds be different than life on Earth? Here are some of the major differences.
“Amazing night-sky views
“Perhaps one of the most dramatic things that visitors to the TRAPPIST-1 system would notice is the view of the other six planets in the sky. In some cases, a neighboring planet might appear twice as large as the full moon seen from Earth. [Images: The 7 Earth-Size Worlds of TRAPPIST-1]
“‘If you were on the surface of one of these planets you would have a wonderful view of the other planets,’ Michaël Gillon, an astronomer at the University of Liège in Belgium and an author on the new paper, said in describing the discovery. ‘You wouldn’t see them like we see Venus or Mars, like dots of light. You would see them really as we see the moon. … You would see the structures on these worlds.’…”
Even so, a half-dozen ‘moons’ in the sky would make landscapes on TRAPPIST-1’s planets resemble (very slightly) Golden Age of Science Fiction magazine covers.
How big each of the other planets would look would depend on where they were in their orbits. Those closer to TRAPPIST-1 than the observer would go through phases, like we see on our moon.
I like to check assertions I read, so I looked up the TRAPPIST-1 system’s orbits.
The semimajor axis for TRAPPIST-1b, the first planet out from its star, is 1,660,000 kilometers. In other words, the planet’s center is 1,660,000 kilometers from the star’s center, on average.
TRAPPIST-1c’s semimajor axis is 2,280,000 kilometers. The distance between the two orbits is around 620,000 kilometers.
Comparison time. The semimajor axis for our moon’s orbit is about 384,400 kilometers. The distance between the orbits of TRAPPIST-1b and c is only about 1.6 time the distance to our moon.
Each planet is about the size of Earth, so when they’re close, the other world would look a lot larger than our moon does from Earth.
If any have water and support life, that’s a big “if,” I suspect poets will eventually wax eloquent about crescent worlds over the sparkling waters of distant lands.
Their “sun” would look much larger than ours, too, but TRAPPIST-1 is much smaller than our star.
That may be why its planets orbit so closely: or not. We’ve learned quite a bit about how stars and planets form, and there’s a great deal left to learn.
“Trappist-1 Planet Discovery Ignites Enthusiasm In Search For Alien Life”
Marcelo Gleiser, Op-ed, NPR (February 23, 2017)
“A group of astronomers announced Wednesday that seven Earth-size planets orbit a small, red, dwarf star 40 light-years away.
“The findings were published in the journal Nature. Observations indicate that at least three of the planets may be at temperate zones where liquid water may exist.
“The extraordinary finding — discovered by astronomers from an international collaboration led by Michaël Gillon from the University of Liège in Belgium, places the search for Earth-like planets and, more spectacularly, the search for alien life, under a brand-new lens. NASA released a fun poster about the findings….”
That poster is from NASA’s strictly-for-fun “Exoplanet Travel Bureau.”
Elon Musk says his SpaceX company will fly tourists around Earth’s moon in late 2018. (BBC News (February 28, 2017))
Sending human explorers to Mars may happen in the 2030s. Reaching the stars — I’ll get back to that.
Finding alien life depends, basically, on two things: extraterrestrial life existing; and knowing what to look for.
There’s a lively debate going on about how, exactly, to define “life” in the physical sense. Searching for alien life depends on knowing what we should look for.
Defining “life” seems simple enough. A Wikipedia page says “Life is a characteristic distinguishing physical entities having biological processes, such as signaling and self-sustaining processes….”
Another Wikipedia page says biological process are “processes vital for a living organism to live…” That definition brings us back to defining “life,” both of which are not particularly helpful, so far.
If “signalling and self-sustaining processes” are what makes something “alive,” then rovers like Curiosity are close to being “alive.” That definition isn’t particularly useful, assuming that most folks don’t think robots are “alive.”
Living critters on Earth are “organic” in the sense that we’re made of organic compounds.
“Organic” in that sense means that the compound contains carbon. The term goes back to when vitalism still made sense, and that’s yet another topic.
We’ve downgraded hopes for Mars from finding Martian people to finding Martian microbes. (December 16, 2016)
We’re also learning a great deal about how to look for extraterrestrial life.
Oxygen in a planet’s atmosphere seemed like an obvious biomarker. Then the National Institutes of Natural Sciences’ Norio Narita and Shigeyuki Masaoka showed how non-biological processes could oxygenate a planet’s atmosphere.2
Making the search more interesting, some critters don’t need oxygen. Or sunlight, for that matter.
Definitions of life-as-we-know-it got stretched in 1977. That’s when researchers found critters living around hydrothermal vents in the Galápagos Rift.
Up to that point, assuming that all life needed sunlight seemed reasonable. After all, plants photosynthesize using sunlight, which provides food for other critters.
Since then, we’ve found extremophiles, critters living in “extreme” places, in quite a few ‘uninhabitable’ spots.
No matter where they live, though, all living critters need water.
It’s where a planet like Earth is far enough from its star for water to be liquid, but not so far that it freezes. But they’re not the only places where we can look for life.
We’ve learned that liquid water can, and almost certainly does, exist in the outer Solar System. Subsurface oceans of Europa and Enceladus, moons of Jupiter and Saturn, may support life. (September 30, 2016)
That may be the only way “life” can work. Properties of the elements and compounds in our bodies seem ideally suited for life’s complex chemistry.
Carbon can bond with a great many other elements, and will form extremely complex molecules.
Water is a really good solvent, and stays liquid over a wide temperature range. It doesn’t get hotter or colder easily, and has other properties that make it an obvious choice for life’s working fluid.
Maybe it’s the only possible choice. Then again, maybe not.
In the ’60s, a former professor at Boston University suggested more-or-less-plausible life chemistries for temperatures ranging from near red-hot to near absolute zero.
We’re third down, nucleic acid/protein (O) in water:
- Fluorosilicone in fluorosilicone
- Fluorocarbon in sulfur
- Nucleic acid/protein (O) in water
- Nucleic acid/protein (N) in ammonia
- Lipid in methane
- Lipid in hydrogen
(“View from a Height” Isaac Asimov (1963), Lancer Books (p. 63))
Isaac Asimov’s grasp of ecology and physics was a trifle shaky in his fiction: but this time he was speculating in his professional field, chemistry.
Since then, quite a few scientists have started taking non-organic life chemistries seriously.3
“TRAPPIST-1: How Long Would It Take to Fly to 7-Planet System?”
Hanneke Weitering, Space.com (February 23, 2017)
“The discovery of seven Earth-size planets around a nearby star, TRAPPIST-1, is certainly exciting news. But what would it take to visit one of these potentially Earth-like alien worlds?
“TRAPPIST-1 is 39 light-years away from Earth, or about 229 trillion miles (369 trillion kilometers). It would take 39 years to get to its current location traveling at the speed of light. But no spacecraft ever built can travel anywhere near that fast.
“That said, people have sent some pretty fast vehicles into outer space. With today’s technology, how long would it take to get to TRAPPIST-1?…”
We’ll have to be patient. Light from TRAPPIST-1 takes about 39 years to get here, and today’s spacecraft are a whole lot slower.
New Horizons would make the trip in 817,000 years. Voyager 1 is faster, and would cover the distance in 685,000 years.
Stephen Hawking’s Breakthrough Starshot initiative microprobes would be much faster, once folks develop the technology. They’d go 39 light-years in roughly 200 years.
Something like Hawking’s Breakthrough Starshot is probably our best option for interstellar probes using technology that’s not too far from off-the-shelf hardware.
Instead of building a single probe, Hawking’s Starshot would be a fleet of 1,000 StarChip mini-probes.
Each StarChip would be a light sail, like NASA’s NanoSail-D: only smaller. A lot smaller. Each mini-probe would be a centimeter across, equipped with a tiny camera, electronics, and a transmitter.
Once in space, several gigawatt lasers — this is tech we don’t quite have yet — would push them up to about 20% speed of light.
They could reach Proxima Centauri in about two decades. A quarter-century after launch, pictures taken by the probes and transmitted back to Earth would give us the first close(ish) pictures of Proxima Centauri b.
We’ve made lasers, like the Argus, handling gigawatt-level emissions.
Getting the things to last more than a few moments, and focusing the beam, is another matter. Besides, I’m not sure how national leaders would take the idea of someone building what amounts to a laser cannon.
“Star’s seven Earth-sized worlds set record”
Paul Rincon, BBC News (February 22, 2017)
“Astronomers have detected a record seven Earth-sized planets orbiting a single star.
“The researchers say that all seven could potentially support liquid water on the surface, depending on the other properties of those planets.
“But only three are within the conventional ‘habitable’ zone where life is considered a possibility.
“The compact system of exoplanets orbits Trappist-1, a low-mass, cool star located 40 light-years away from Earth.
“The planets, detected using Nasa’s Spitzer Space Telescope and several ground-based observatories, are described in the journal Nature….”
Folks at SETI checked the TRAPPIST-1 system for radio signals last year, using the Allen Telescope Array. They ‘heard’ no obviously-artificial signal, but will try again.4
That could mean there’s nobody there.
Or maybe radio isn’t the only long-range communication technology. We started using wavelengths between 1 millimeter and 100 kilometers about a century back. I’ve talked about tech, time, and SETI, before. (December 16, 2016; September 16, 2016)
Finding life, intelligent or otherwise, would be enormously exciting. But that’s not the only reason scientists study TRAPPIST-1 and its planets.
Because the star is so dim, and fairly close, studying its planets will be comparatively easy. As BBC Science Editor David Shukman said, “telescopes studying the planets are not dazzled as they would be when aiming at far brighter stars.” (BBC News)
Besides being much closer than most of our galaxy’s stars, TRAPPIST-1’s planets pass between their star and ours once each of their years. That lets scientists study light that passes through their atmosphere. Assuming they have atmospheres.
(From NASA’s Goddard Space Flight Center, used w/o permission.)
(“To determine what’s in the atmosphere of an exoplanet, astronomers watch the planet pass in front of its host star and look at which wavelengths of light are transmitted and which are partially absorbed.”
J. de Wit’s artwork shows TRAPPIST-1 and two of its planets. It’s a good illustration, but includes details that are educated guesses: not facts.
Scientists got a picture of TRAPPIST-1 last year, but they were looking for a companion star or brown dwarf. Those images were very low-resolution, too; and confirmed that TRAPPIST-1 is a single star.5 The pictures didn’t show planets, and weren’t intended to.
We use something like transmission and absorption spectroscopy each time we look at something and notice what color it is. Different materials reflect, transmit, and absorb, light in distinct ways.
I could explain that by saying “energy associated with the quantum mechanical change primarily determines the frequency of the absorption line.” If you’re interested, I put a few links to geek-speak resources near the end of this post.6
You can blame Isaac Newton for spectroscopy. He called the colors we get when light passes through a prism a spectrum. William Hyde Wollaston noticed dark absorption lines in our star’s spectrum in 1802.
Anyway, each element emits a particular set of wavelengths if it’s heated enough; and absorbs those wavelengths if it’s not. I’m over-simplifying it: a lot.
Wondering why elements act that way helped scientists develop quantum mechanics, and that’s yet again another topic.
Scientists got a ‘look’ at the atmospheres of TRAPPIST-1 b and c last year. (July 29, 2016)
They found a “featureless spectrum,” which rules out a puffy atmosphere of mostly hydrogen.
We’re still not sure what their atmospheres are like, but we know their masses and diameters. Scientists think the odds are good that each of the seven planets found so far are rocky, like the Solar System’s inner worlds.
TRAPPIST-1 is upwards of 500,000,000 years old. How much older is hard to say, since low-mass stars change very slowly after settling on to the main sequence. A star like TRAPPIST-1 could last a hundred billion years.
That could mean that habitable planets in such systems stay habitable for a very long time.
On the other hand, last year scientists measured x-rays from TRAPPIST-1. That’s nothing unusual. Our star produces about as much x-ray radiation during its quiet phase.
TRAPPIST-1’s planets are so close, though, that these x-rays could do a lot more than the ones hitting Earth. That may affect the TRAPPIST-1 planetary atmospheres, or not.7
The planets are almost certainly either tidally locked, with one side always facing their sun, or in a spin-orbit resonance like Mercury. Either way, life on such worlds wouldn’t be entirely like its terrestrial analog.8
That could mean that life on the TRAPPIST-1 planets is impossible — or that this amazing puzzle collection we call the universe has more surprises for us.
More about how I see life, science, and the Fermi paradox:
- “SETI: What If?”
(December 23, 2016)
- “Mars, Aliens, and SETI”
(December 16, 2016)
- “Europa, Mars, and Someday the Stars”
(September 30, 2016)
- “Proxima Centauri b, Looking for Life”
(September 2, 2016)
- “Studying Thousands of New Worlds”
(July 29, 2016)
- “Ultracool Dwarf and the Seven Planets”
eso1706 — Science Release (February 22, 2017)
- “TRAPPIST-1 Comparison to Solar System and Jovian Moons”
Jet Propulsion Laboratory, California Institute of Technology (February 22, 2017)
- “The TRAPPIST-1 Habitable Zone”
Jet Propulsion Laboratory, California Institute of Technology (February 22, 2017)
- “NASA’s Hubble Telescope Makes First Atmospheric Study of Earth-Sized Exoplanets”
NASA press release (July 20, 2016)
- “Oxygen Is Not Definitive Evidence of Life on Extrasolar Planets”
NAOJ, Astrobiology (September 10, 2015)
- “Titania may produce abiotic oxygen atmospheres on habitable exoplanets”
Norio Narita, Takafumi Enomoto, Shigeyuki Masaoka, Nobuhiko Kusakabe; Scientific Reports (Received March 31, 2015; Accepted August 12, 2015; Published online September 10, 2015)
- “This Weird Planetary System Seems Like Something From Science Fiction”
Seth Shostak, Senior Astronomer, SETI; NBC News (February 22, 2017)
- “7 Earth-Size Planets Orbit Dwarf Star, NASA and European Astronomers Say”
Kenneth Chang, The New York Times (February 22, 2017)
- “Speckle Imaging Excludes Low-Mass Companions Orbiting the Exoplanet Host Star TRAPPIST-1”
Steve B. Howell, Mark E. Everett, Elliott P. Horch, Nicholas Jon Scott; researchgate.net (September 2016)
- “Strong XUV irradiation of the Earth-sized exoplanets orbiting the ultracool dwarf TRAPPIST-1”
Peter J. Wheatley, Tom Louden, Vincent Bourrier, David Ehrenreich, Michaël Gillon; Monthly Notices of the Royal Astronomical Society (October 8, 2016)