NASA announces seven ‘Earths’ found around one star, TRAPPIST-1

IS this an intergalactic housing estate? Seven Earth-sized worlds have been found orbiting a single star 39 light-years away. And these new worlds could hold life.

The red dwarf star TRAPPIST-1, which sits in the constellation of Aquarius and barely the size of Jupiter, was thought a year ago to have three planets in orbit around it.

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Tau.Neutrino said:

IS this an intergalactic housing estate?

NO. THIS IS WITHIN OUR GALAXY.

party_pants said:

Tau.Neutrino said:

IS this an intergalactic housing estate?

NO. THIS IS WITHIN OUR GALAXY.

Indeed, this star is extremely close to us.

The geometry seems remarkable, 7 earth-sized planets all closer to the star than Mercury is to the sun. To someone on one of the planets, the other planets would look as big as the moon looks to us, or bigger.

Copied from Chat without attribution.

Someone in chat announced that NASA would announce a major new exoplanet discovery.
Mrs m just heard on radio. It’s seven new exoplanets with water.

from what I caught on the teev this morning only 3 or 4 of them have liquid water
No confirmation of water. Only that 3 are in the habitable zone
And a couple more may be under gravitational influences which may cause liquid water below the surface.

Water below the surface due to gravity. WTOLFE (wipes tears of laughter from eyes).
Great joke.
.
I can imagine it’s true, because subsurface water due to gravitational influences immediately implies that they’re really very close to their suns, like all the Kepler planets. Which implies that their suns produce hardly any heat. Which mean’s they’re likely to be flare stars which means that life on the surface is impossible.

Do the news reports say anything about orbit eccentricity?

No. But apparently they are all within the orbit of Mercury…

Everything from Kepler is.

I take it this means that the planets are not around nearby stars.
Do the news reports say anything about orbit eccentricity?
Apparently they are all within the orbit of Mercury…

wow, and we’ve only just found them? what have those astronomers being doing for the last 1000 years???

OK. Good joke. Add “wry” emoji here.

Astronomers have looked for asteroids within the orbit of Mercury, they’ve even been given a groups name “Vulcans”, but when last I checked, none had been found. According to Wikipedia, none exist.

Google is celebrating the discovery with their thingy.

Bubblecar said:

Google is celebrating the discovery with their thingy.

So is apod.

https://apod.nasa.gov/apod/ap170218.html

I can’t understand how so many planets orbiting that close to each other could have stable orbits.

Spiny Norman said:

I can’t understand how so many planets orbiting that close to each other could have stable orbits.

It does sound a bit hectic.

Spiny Norman said:

I can’t understand how so many planets orbiting that close to each other could have stable orbits.

Interesting celestial mechanics.

No doubt that system will gets some attention..

• I can’t understand how so many planets orbiting that close to each other could have stable orbits.

Spiny Norman said:

I can’t understand how so many planets orbiting that close to each other could have stable orbits.

I don’t see why not. The Sun has its asteroid belt with 500,000 plus asteroids.
Saturn has its ring system. Seven is quite small.

Orbits that are initially random will tend to circular and in-plane over time.

furious said:

• I can’t understand how so many planets orbiting that close to each other could have stable orbits.

Flare star for sure, being that small. As stars get smaller, their solar flares and sunspots get larger. Couple that with overall light more feeble and planet distance closer and you end up with wild variations in solar brightness.

Sure point noted over Saturn’s various moons and there’s certainly some orbital resonance going on, but oly one of Saturn’s Moons (Titan) is big enough to be close to being called a planet. There’s seven planet-sized bodies orbiting around Trappist-1.
It just seems odd to me that such (relatively) massive bodies can orbit so (relatively) closely and be fairly stable.

Spiny Norman said:

Sure point noted over Saturn’s various moons and there’s certainly some orbital resonance going on, but oly one of Saturn’s Moons (Titan) is big enough to be close to being called a planet. There’s seven planet-sized bodies orbiting around Trappist-1.
It just seems odd to me that such (relatively) massive bodies can orbit so (relatively) closely and be fairly stable.

What seems seriously odd to me is the combinations of rings and moons in our own solar system. How are the waves in Saturn’s rings that are generated by moons such a Diane and Prometheus damped out so rapidly without introducing instabilities?

Why do we find moons and rings both inside and outside the Roche limit for each planet? Rings are only supposed to be formed within the Roche limit and moons outside.

Where do the spokes in Saturn’s rings come from?

Those are the stability questions that bother me.

mollwollfumble said:

Spiny Norman said:

Sure point noted over Saturn’s various moons and there’s certainly some orbital resonance going on, but oly one of Saturn’s Moons (Titan) is big enough to be close to being called a planet. There’s seven planet-sized bodies orbiting around Trappist-1.
It just seems odd to me that such (relatively) massive bodies can orbit so (relatively) closely and be fairly stable.

What seems seriously odd to me is the combinations of rings and moons in our own solar system. How are the waves in Saturn’s rings that are generated by moons such a Diane and Prometheus damped out so rapidly without introducing instabilities?

Why do we find moons and rings both inside and outside the Roche limit for each planet? Rings are only supposed to be formed within the Roche limit and moons outside.

Where do the spokes in Saturn’s rings come from?

Those are the stability questions that bother me.

My best theory is that the universe we see is just the alpha version. The final version will make a lot more sense.

But seriously, yes, there’s a lot to learn about how all this works, ta.

> The universe we see is just the alpha version. The final version will make a lot more sense.

Any chance of putting that on an inspirational poster?

Spiny Norman said:

mollwollfumble said:

Spiny Norman said:

Sure point noted over Saturn’s various moons and there’s certainly some orbital resonance going on, but oly one of Saturn’s Moons (Titan) is big enough to be close to being called a planet. There’s seven planet-sized bodies orbiting around Trappist-1.
It just seems odd to me that such (relatively) massive bodies can orbit so (relatively) closely and be fairly stable.

What seems seriously odd to me is the combinations of rings and moons in our own solar system. How are the waves in Saturn’s rings that are generated by moons such a Diane and Prometheus damped out so rapidly without introducing instabilities?

Why do we find moons and rings both inside and outside the Roche limit for each planet? Rings are only supposed to be formed within the Roche limit and moons outside.

Where do the spokes in Saturn’s rings come from?

Those are the stability questions that bother me.

My best theory is that the universe we see is just the alpha version. The final version will make a lot more sense.

But seriously, yes, there’s a lot to learn about how all this works, ta.

Thank you, Spiny Norman. I turned it into an inspirational poster.

I love that!

santa will be busy

https://en.wikipedia.org/wiki/TRAPPIST-1

“…A year on the closest planet passes in only 1.5 Earth days, while the sixth planet’s year passes in only 12.3 days…”

transition said:

santa will be busy

https://en.wikipedia.org/wiki/TRAPPIST-1

“…A year on the closest planet passes in only 1.5 Earth days, while the sixth planet’s year passes in only 12.3 days…”

Obviously not to scale, what is the point of these comparisons?

Witty Rejoinder said:

transition said:

santa will be busy

https://en.wikipedia.org/wiki/TRAPPIST-1

“…A year on the closest planet passes in only 1.5 Earth days, while the sixth planet’s year passes in only 12.3 days…”

Obviously not to scale, what is the point of these comparisons?

Seems harsh.

The first two images are to the same scale in terms of the size of the orbits, so it shows you that the innermost of these planets is about as far from Trappist-1 as Callisto is from Jupiter.

The third image is not to the same scale but there are lines clearly showing the connection between the scale of the Trappist-1 system and our inner solar system, and the Trappist-1 system is also redrawn within the image of the inner solar system.

I found this to be a very useful demonstration of the size of the Trappist-1 system.

>Obviously not to scale, what is the point of these comparisons?

comparison of solar system size (it’s in the middle where our sun’d be), and planets too

I just wanted some colour and pictures, to satisfy the 6yo astronomer in me

• I found this to be a very useful demonstration of the size of the Trappist-1 system.

I think this one shows it better:

furious said:

• I found this to be a very useful demonstration of the size of the Trappist-1 system.

I think this one shows it better:

I disagree, that one gives a completely incorrect idea of the distance of the planets from the sun

> Do they talk about orbital eccentricity?

Yes, they do, according to Wiki. The inner six have eccentricities below 0.085. And the inner six have masses below 1.38 earth masses. Smallest 0.41+-0.27 earth masses. All seven planets are likely to be tidally synchronized. Compare eccentricities with our solar system. Mercury and Pluto have similar eccentricities near 0.2. Mars 0.09. Earth near 0.02.

The planets of Trappist-1 have orbits nowhere near the closest hot Jupiters found on other solar systems.

What’s the smallest exoplanet found so far? Startlingly few with a mass below 0.41 Earth masses. Only 5 unreliable (because of mismatch between mass and radius) and 1 reliable exoplanets below that. KOI-1843 b has a claimed mass of 0.32 Earth masses.

dv said:

furious said:

• I found this to be a very useful demonstration of the size of the Trappist-1 system.

I think this one shows it better:

I disagree, that one gives a completely incorrect idea of the distance of the planets from the sun

dv can’t read a logarithmic scale?

exoplanet.eu gives the inclination of these planets as about 89.6° to about 89.8°, but I can’t find what that’s relative to.

mollwollfumble said:

dv can’t read a logarithmic scale?

ROFL

transition said:

>Obviously not to scale, what is the point of these comparisons?

comparison of solar system size (it’s in the middle where our sun’d be), and planets too

I just wanted some colour and pictures, to satisfy the 6yo astronomer in me

Yes. That’s the problem. I had a wild goose chase about planet diameters (colour is related to diameter) until I realised that the colours of the planets are totally wrong.

btm said:

exoplanet.eu gives the inclination of these planets as about 89.6° to about 89.8°, but I can’t find what that’s relative to.

That means that the spin axis of the star is very close to the orbital plane of the planets. The star is tipped on its side.

mollwollfumble said:

btm said:

exoplanet.eu gives the inclination of these planets as about 89.6° to about 89.8°, but I can’t find what that’s relative to.

That means that the spin axis of the star is very close to the orbital plane of the planets. The star is tipped on its side.

I’m going to go out on a limb and say that the Extrasolar.eu site is referring to something else when they say inclination. The reason I say this is that they have estimates of inclination for 615 planets, and most of those have inclinations between 88 degrees and 92 degrees. That would be very weird if they were referring to orbital inclination to stellar spin axis.

dv said:

mollwollfumble said:

btm said:

exoplanet.eu gives the inclination of these planets as about 89.6° to about 89.8°, but I can’t find what that’s relative to.

That means that the spin axis of the star is very close to the orbital plane of the planets. The star is tipped on its side.

I’m going to go out on a limb and say that the Extrasolar.eu site is referring to something else when they say inclination. The reason I say this is that they have estimates of inclination for 615 planets, and most of those have inclinations between 88 degrees and 92 degrees. That would be very weird if they were referring to orbital inclination to stellar spin axis.

Planet’s axial inclination relative to its orbital plane?

Michael V said:

dv said:

mollwollfumble said:

That means that the spin axis of the star is very close to the orbital plane of the planets. The star is tipped on its side.

I’m going to go out on a limb and say that the Extrasolar.eu site is referring to something else when they say inclination. The reason I say this is that they have estimates of inclination for 615 planets, and most of those have inclinations between 88 degrees and 92 degrees. That would be very weird if they were referring to orbital inclination to stellar spin axis.

Planet’s axial inclination relative to its orbital plane?

Unlikely…

Michael V said:

dv said:

mollwollfumble said:

That means that the spin axis of the star is very close to the orbital plane of the planets. The star is tipped on its side.

I’m going to go out on a limb and say that the Extrasolar.eu site is referring to something else when they say inclination. The reason I say this is that they have estimates of inclination for 615 planets, and most of those have inclinations between 88 degrees and 92 degrees. That would be very weird if they were referring to orbital inclination to stellar spin axis.

Planet’s axial inclination relative to its orbital plane?

TATE says it’s the inclination of the planet’s orbital plane relative to a reference plane. Given the quoted numbers, I’m guessing it might be relative to the star’s magnetic field, but it’d be a bit difficult to measure that at this distance, except by inference.

> I’m going to go out on a limb and say that the Extrasolar.eu site is referring to something else when they say inclination. The reason I say this is that they have estimates of inclination for 615 planets, and most of those have inclinations between 88 degrees and 92 degrees. That would be very weird if they were referring to orbital inclination to stellar spin axis.

Ooo. You have to be right there. I missed that.

mollwollfumble said:

> I’m going to go out on a limb and say that the Extrasolar.eu site is referring to something else when they say inclination. The reason I say this is that they have estimates of inclination for 615 planets, and most of those have inclinations between 88 degrees and 92 degrees. That would be very weird if they were referring to orbital inclination to stellar spin axis.

Ooo. You have to be right there. I missed that.

Possibly some kind of Sol centric measure, like inclination to a plane perpendicular to our view, which would make sense because we’d expect most star crossing planets to have orbits basically in line with our sight.

mollwollfumble said:

Thank you, Spiny Norman. I turned it into an inspirational poster.

Love it! Thanks. :D

Spiny Norman said:

mollwollfumble said:

Thank you, Spiny Norman. I turned it into an inspirational poster.

Love it! Thanks. :D

A retro space version of that would look great as well.