APOD: Seven Worlds for TRAPPIST-1 (2017 Feb 23)

APOD Robot · Post by **APOD Robot** » Thu Feb 23, 2017 5:16 am

Seven Worlds for TRAPPIST-1

Explanation: Seven worlds orbit the ultracool dwarf star TRAPPIST-1, a mere 40 light-years away. In May 2016 astronomers using the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) announced the discovery of three planets in the TRAPPIST-1 system. Just announced, additional confirmations and discoveries by the Spitzer Space Telescope and supporting ESO ground-based telescopes have increased the number of known planets to seven. The TRAPPIST-1 planets are likely all rocky and similar in size to Earth, the largest treasure trove of terrestrial planets ever detected around a single star. Because they orbit very close to their faint, tiny star they could also have regions where surface temperatures allow for the presence of liquid water, a key ingredient for life. Their tantalizing proximity to Earth makes them prime candidates for future telescopic explorations of the atmospheres of potentially habitable planets. All seven worlds appear in this artist's illustration, an imagined view from a fictionally powerful telescope near planet Earth. Planet sizes and relative positions are drawn to scale for the Spitzer observations. The system's inner planets are transiting their dim, red, nearly Jupiter-sized parent star.

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BillT · Post by **BillT** » Thu Feb 23, 2017 7:26 am

Anyone know the orbital period of each planet? I saw a range from 1.5 to 12 days mentioned but not the individual period of each planet. I'm wondering how stable the arrangement is.

Douglas · Post by **Douglas** » Thu Feb 23, 2017 11:27 am

TRAPPIST-1 is where we might find Medea's fuxes.
http://www.strandbooks.com/product/mede ... 9111862637

Because they're all tidally locked, life might be located near rings on each planet facing the star as the atmosphere will be most protective there from X-rays and ultraviolet. With 6 other planets in each's skies in orbits that tight that'll be a busy mind that regards that arrangement.

neufer · Post by **neufer** » Thu Feb 23, 2017 1:31 pm

BillT wrote:
Anyone know the orbital period of each planet? I saw a range from 1.5 to 12 days mentioned but not the individual period of each planet. I'm wondering how stable the arrangement is.

neufer wrote:
I noticed all the planets seem to be in a 3:2 resonance
with their neighboring planets a la Pluto/Neptune.

Does that mean that their elliptical
orbits are all set up such that:

each outer/inner planet is
near aphelion/perihelion
at inferior conjunction.

bystander · Post by **bystander** » Thu Feb 23, 2017 2:47 pm

http://asterisk.apod.com/viewtopic.php?t=36874#p267349

Fred the Cat · Post by **Fred the Cat** » Thu Feb 23, 2017 4:35 pm

Any chance they could be named after the seven dwarfs with the sun representative of Snow White's ruby lips?

BDanielMayfield · Post by **BDanielMayfield** » Thu Feb 23, 2017 5:25 pm

Fred the Cat wrote:Any chance they could be named after the seven dwarfs with the sun representative of Snow White's ruby lips?

please nooooo.

Respectfully, I must disagree. I just can't take it anymore! First came the calling of all main sequence, normal stars dwarfs. Then the demotion of Pluto to dwarf planet status. At least 4 of these newly discovered worlds are larger than the Earth. Please don't encourage the continuation of this trend toward deminishment.

Down with dwarfism in Astronomy!
Replanetize Pluto!
Dedwarf the Sun!

Bruce, the anti-dwarfite

Jim Armstrong · Post by **Jim Armstrong** » Thu Feb 23, 2017 5:34 pm

"in the Asterisk logo?"?
I hope I got that. (P.S.: Nope, missed it)
"they orbit very close to their faint, tiny star they could also have regions where surface temperatures allow for the presence of liquid water, a key ingredient for life."

I have suggested before that the life subject should be discussed here as "life as we know it" or "life as it exists on Earth."
I am not prepared to claim that I somehow know what is necessary for life.

This is an exciting discovery.

Ann · Post by **Ann** » Thu Feb 23, 2017 8:43 pm

Jim Armstrong wrote:"in the Asterisk logo?"?
I hope I got that. (P.S.: Nope, missed it)
"they orbit very close to their faint, tiny star they could also have regions where surface temperatures allow for the presence of liquid water, a key ingredient for life."

I have suggested before that the life subject should be discussed here as "life as we know it" or "life as it exists on Earth."
I am not prepared to claim that I somehow know what is necessary for life.

This is an exciting discovery.

Good point, but I think it is made clear that the APOD caption is indeed talking about life as we know it, namely the kind of life that is dependent on liquid water.

I think Chris Peterson pointed out somewhere here at Starship Asterisk* that even though there may well exist many kinds of life that are completely different from life as we know it, it might be very difficult for us to find such life. We might not know what to look for in order to search for such life, and we might not recognize the signs of such life even if it was right before our noses.

Ann

rstevenson · Post by **rstevenson** » Fri Feb 24, 2017 12:59 am

BDanielMayfield wrote:
Fred the Cat wrote:Any chance they could be named after the seven dwarfs with the sun representative of Snow White's ruby lips?
please nooooo.

Respectfully, I must disagree. I just can't take it anymore! First came the calling of all main sequence, normal stars dwarfs. Then the demotion of Pluto to dwarf planet status. At least 4 of these newly discovered worlds are larger than the Earth. Please don't encourage the continuation of this trend toward deminishment.

Down with dwarfism in Astronomy!
Replanetize Pluto!
Dedwarf the Sun!
Bruce, the anti-dwarfite

So Bruce, you're saying we should just toss the idea of dwarfism?

Rob

BDanielMayfield · Post by **BDanielMayfield** » Fri Feb 24, 2017 5:06 am

rstevenson wrote:So Bruce, you're saying we should just toss the idea of dwarfism?

Rob

Not entirely, and that was ment to be humorous. But seriously, isn't the term overused? Especially when it is applied to main sequence stars like the sun and all larger MS stars. The sun is in fact larger than most stars. I just think it would make more sense to just use it to label things that are actually small as compared to normal examples.

Bruce

Ann · Post by **Ann** » Fri Feb 24, 2017 6:46 am

: Click to view full size image

The seven dwarfs.
Source: https://50shadesofanimation.wordpress.c ... en-dwarfs/

Down with the seven dwarfs... I'm just saying!

: Click to view full size image

And seven!!!

Hey!!!! This was my 7777th post!!! Must be a lucky number!!

Ann

De58te · Post by **De58te** » Fri Feb 24, 2017 10:41 am

neufer wrote:I noticed all the planets seem to be in a 3:2 resonance
with their neighboring planets a la Pluto/Neptune.

Not really all of them. Venus and Earth are closer to a 3:2 resonance (not quite) than Trappist-1 c and d.
3.25:2 for Venus and Earth, to 3.35:2 for Trappist-1 c and Trappist-1 d.

eurorusty · Post by **eurorusty** » Fri Feb 24, 2017 8:55 pm

With such a tight packing, I would guess tidal forces would be significant. I think we could expect one or more planets to exhibit global volcanism like Io does in the Jovian system. Will see if I can write a simulator to confirm what the forces will be!

BDanielMayfield · Post by **BDanielMayfield** » Fri Feb 24, 2017 10:21 pm

eurorusty wrote:With such a tight packing, I would guess tidal forces would be significant. I think we could expect one or more planets to exhibit global volcanism like Io does in the Jovian system. Will see if I can write a simulator to confirm what the forces will be!

Very true. And if there are any large oceans in this system there should be big tides raised whenever adjacent planets have their frequent conjunctions. We have our highest tides here whenever the Earth, Moon and Sun line up. Imagine the tides that could be generated whenever all seven of these planets line up on the same side of their star. If there where to be a semi-water world here with both landmasses and large oceans its tidal zones should be very interesting places.

These worlds are young too, so some, most or all of their interiors could have more heat than the Earth's currently does for at least three reasons:

Strong interplanetary tides.
Leftover heat from relatively recent accretion.
More radioactive elements which haven't had enough time to decay yet.

To me this all suggests the likelihood of active volcanism, plate tectonics, mountain building, etc.

Bruce

neufer · Post by **neufer** » Fri Feb 24, 2017 10:21 pm

eurorusty wrote:
With such a tight packing, I would guess tidal forces would be significant. I think we could expect one or more planets to exhibit global volcanism like Io does in the Jovian system. Will see if I can write a simulator to confirm what the forces will be!

Io heats up pretty good with a period of 1.77 days (despite an eccentricity of just 0.0041).

Since tidal forces scale inversely with period squared
(and tidal heating probably scales inversely with period to the fifth power

)
one might assume that TRAPPIST-1b (with a period of just 1.51 days) heats up pretty good tidally.

Note, however, that tidal heating drops off very rapidly [R^-(15/2) maybe] with orbital distance.

BDanielMayfield · Post by **BDanielMayfield** » Fri Feb 24, 2017 11:43 pm

neufer wrote:Io heats up pretty good with a period of 1.77 days (despite an eccentricity of just 0.0041).

Since tidal forces scale inversely with period squared
(and tidal heating probably scales inversely with period to the fifth power )
one might assume that TRAPPIST-1b (with a period of just 1.51 days) heats up pretty good tidally.

Note, however, that tidal heating drops off very rapidly [R^-(15/2) maybe] with orbital distance.

Is Io's orbit eccentricity (small though it is) the main cause of its heating? How much of Io's heat is caused by the continuously changing distances between Jupiter's large moons?

Chris Peterson · Post by **Chris Peterson** » Fri Feb 24, 2017 11:47 pm

BDanielMayfield wrote:Is Io's orbit eccentricity (small though it is) the main cause of its heating? How much of Io's heat is caused by the continuously changing distances between Jupiter's large moons?

All of Io's tidal heating is the result of its changing distance from Jupiter over its orbit, because of its non-zero eccentricity. The only effect of the other moons is in preventing Io's orbit from becoming circularlized over time.

neufer · Post by **neufer** » Sat Feb 25, 2017 1:30 am

Chris Peterson wrote:
BDanielMayfield wrote:
Is Io's orbit eccentricity (small though it is) the main cause of its heating? How much of Io's heat is caused by the continuously changing distances between Jupiter's large moons?
All of Io's tidal heating is the result of its changing distance from Jupiter over its orbit, because of its non-zero eccentricity. The only effect of the other moons is in preventing Io's orbit from becoming circularlized over time.

A while back I ran the numbers on this and
(on my second attempt

) proved this to be the case.

BDanielMayfield · Post by **BDanielMayfield** » Sat Feb 25, 2017 4:33 am

neufer wrote:
Chris Peterson wrote:
BDanielMayfield wrote:
Is Io's orbit eccentricity (small though it is) the main cause of its heating? How much of Io's heat is caused by the continuously changing distances between Jupiter's large moons?
All of Io's tidal heating is the result of its changing distance from Jupiter over its orbit, because of its non-zero eccentricity. The only effect of the other moons is in preventing Io's orbit from becoming circularlized over time.
A while back I ran the numbers on this and
(on my second attempt ) proved this to be the case.

Thank you Chris & Art for helping to refine my understanding.

Bruce

geckzilla · Post by **geckzilla** » Sun Feb 26, 2017 1:08 am

Anyone know if orbital resonance prevents things like double stellar transits happening from the vantage point of, say, the third or fourth planets? I'm guessing the chance goes up by the fifth, six, and seventh, but I'm not sure.

neufer · Post by **neufer** » Sun Feb 26, 2017 5:15 pm

geckzilla wrote:
Anyone know if orbital resonance prevents things like double stellar transits happening from the vantage point of, say, the third or fourth planets? I'm guessing the chance goes up by the fifth, six, and seventh, but I'm not sure.

Using the orbital numbers at Wikipedia

I calculate that every 36.15 days:

c observes 9 transits of b
d observes 6 transits of c
e observes 3 transits of d
f observes 2 transits of e
g observes 1 transit of f

This is such a remarkable sequence (

) that one can only conclude:

1) that planets e through g regularly observe double stellar transits
2) or that things are so aligned that none of the planets ever observes a double stellar transit.

(I would doubt, however, that any of the planets d through g
ever observes a double stellar transit of it's two nearest neighbors.)

geckzilla · Post by **geckzilla** » Sun Feb 26, 2017 5:23 pm

I've been toying around with a reasonably accurate simulation I've got set up in Blender, and all I know is that each planet seems to be in the wrong place to make the observation each time two of the others form in syzygy with the star. My simulation is unfortunately keyframe animated and I doubt its accuracy after copy and pasting each orbit over and over. Rounding errors build up. It only runs for 100 Earth days currently.

neufer · Post by **neufer** » Sun Feb 26, 2017 7:49 pm

geckzilla wrote:
I've been toying around with a reasonably accurate simulation I've got set up in Blender, and all I know is that each planet seems to be in the wrong place to make the observation each time two of the others form in syzygy with the star. My simulation is unfortunately keyframe animated and I doubt its accuracy after copy and pasting each orbit over and over. Rounding errors build up. It only runs for 100 Earth days currently.

1) Do the planet's initial relative positions return after 36.15 days?

2) How do you set the planet's initial relative positions?

3) How do you set Blender?
(grate, blend, shred, grind, mash, liquefy, frappe, stir, beat, puree, chop, whip, pulse, ice crush?)

geckzilla · Post by **geckzilla** » Sun Feb 26, 2017 8:18 pm

1. Almost, but not quite. The dope sheet might interest you. Each diamond is a return to original position / 1 revolution. 100 frames = 1 day so 3615 is where the system stands after 36.15 days.

2. I used the chart on this page: http://www.trappist.one/#system => Direct link to chart

3. My GPU fan spins mightily

Starship Asterisk*

APOD: Seven Worlds for TRAPPIST-1 (2017 Feb 23)

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