TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by tesh90 on 21st February 2017, 4:23 am

NASAwatch suggests it might be to do with Alpha CentauriBb - the single observation of a longer period earth like planet rather than the (Hubble) "unconfirmed" shorter period planet.

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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Sirius_Alpha on 21st February 2017, 12:57 pm

Might want to check your source again...

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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Led_Zep on 21st February 2017, 12:58 pm

http://nasawatch.com/archives/2017/02/spitzer-discove.html

Four more planets for Trappist-1 ?? Shocked
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by tesh90 on 21st February 2017, 1:40 pm

my bad…

p.s. dont' really care as I was going on what I read at the time but any news in this field is good news as far as I'm concerned so I'm not put that I was wrong.

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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Led_Zep on 21st February 2017, 2:56 pm

http://spaceref.com/exoplanets/nearby-star-has-7-earth-sized-worlds---most-in-habitable-zone.html

Nearby Star Has 7 Earth-Sized Worlds - Most In Habitable Zone

It will be announced tomorrow by NASA that Michael Gillon et al have confirmed 4 more Earth-sized planets circling TRAPPIST-1 in addition to 3 already discovered.
It is possible that most of the planets confirmed thus circling far TRAPPIST-1 could be in the star's habitable zone. The inner 6 planets are probably rocky in composition and may be just the right temperature for liquid water to exist (between 0 - 100 degrees C) - if they have any water, that is. The outermost 7th planet still needs some more observations to nail down its orbit and composition.
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Led_Zep on 21st February 2017, 3:26 pm

Who said embargo ? Laughing

http://www.businessinsider.fr/us/earth-size-worlds-seven-trappist-1-2017-2/









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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Sirius_Alpha on 21st February 2017, 5:24 pm

TRAPPIST-1 was a campaign 12 target for Kepler-K2, which may explain how they discovered these planets and got their masses from TTV.
https://keplerscience.arc.nasa.gov/k2-approved-programs.html#campaign-12

Edit: Or maybe not. C12 data isn't out until May 2017.
https://keplerscience.arc.nasa.gov/k2-fields.html

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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Led_Zep on 21st February 2017, 5:36 pm

more probably 20 consecutive days of observation with SPITZER
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by tommi59 on 21st February 2017, 6:51 pm

Host star is small planets are very close  maybe RV masses?
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Led_Zep on 21st February 2017, 7:02 pm

I don't think.
From the discovery paper, last year :

"...The masses of the planets, and thus their compositions, remain unconstrained by these observations. The results of planetary thermal evolution models—and the intense extremeultraviolet (1−1,000 Å) emission of low-mass stars18 during their early lives—make it unlikely that such small planets would have thick envelopes of hydrogen and/or helium gases. Statistical analyses of sub-Neptune-sized planets detected by the Kepler spacecraft indicate that most Earth-sized planets in close orbit around solar-type stars are rocky. Nonetheless, the paucity of material in the inner region of the protoplanetary disk of an ultracool dwarf would seem to challenge the in situ formation of rocky planets the size of Earth6, favouring instead compositions dominated by ice-rich material originating from beyond the ice line7. Confirming this hypothesis will require precise mass measurements so as to break the degeneracy between the relative amounts of iron, silicates and ice. This should be made possible by next-generation, high-precision infrared velocimeters able to measure the low-amplitude Doppler signatures (of one-half to a few metres per second) of the planets. Alternatively, the planets’ masses could be constrained by measuring the transit timing variations (TTVs) caused by their mutual gravitational interactions , or by transit transmission spectroscopy..."
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Led_Zep on 22nd February 2017, 2:18 pm

Official press release (NASA) :
https://www.nasa.gov/press-release/nasa-telescope-reveals-largest-batch-of-earth-size-habitable-zone-planets-around

Paper preview (Nature)
the article is not free

http://www.nature.com/nature/journal/v542/n7642/full/nature21360.html
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Sirius_Alpha on 22nd February 2017, 3:53 pm

You can access the paper from here:
https://www.eso.org/public/news/eso1706/

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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Led_Zep on 22nd February 2017, 4:05 pm

https://www.cieletespace.fr/actualites/sept-planetes-de-la-taille-de-la-terre-autour-d-une-etoile-a-40-annees-lumiere

Automatic translation of an interesting article on the site of the french magazine Ciel et Espace :


Other strangeness: the orbital periods of planets are commensurable. For example, when Trappist-1 b (closest to the star) is a round, Trappist-1 e (fourth) in fact four. Or 'c' in fact ten when 'b' in fact six. Or 'g' in fact two when "e" is only one.
This isn't by chance, according to astrophysicist Franck Selsis, co-author of the study: "This is the expected behavior of planets that would be formed far from their stars and have migrated together more close to her, through their respective gravitational disturbances and also their interaction with a disk of initial gas."
If the planets formed beyond the "line of ice", at a sufficient distance from their central fire to make water, nitrogen and other volatile components are there are accumulated, then the planets are perhaps waterlogged today yet (it's almost certain to Trappist-1f, the fourth planet in the system). "It means increased the resemblance with the satellites of Jupiter, as some are also commensurable orbits", notes Franck Selsis. Trappist - 1 b, kneaded by the conflicting gravitational forces of its star and its sisters, would she be a volcanic planet similar to Io?
A thousand new targets
It is too early to tell, but there is a good chance to let us know it pretty quickly. «What's great, is that the planetary transits are very easy to measure on dwarf stars.» The atmosphere of these planets will be able to be examined without delay by the VLT, Hubble or Spitzer infrared satellite", explains Franck Selsis. These atmospheres will prove similar or different? Will they betray the presence of liquid water, or even a biological activity on one of the planets?
"We are currently in discussion with the teams who built the JWST to negotiate observing time. In an atmosphere that would be as compact that that of the Earth, we would have 500 to 1000 hours to observe elements such as carbon dioxide, ozone, methane or water', says Michaël Gillon.
Meanwhile the launch of the space of 6.5 m telescope expected in October 2018, the team was already pointing Hubble at planets of Trappist-1. "We want to know if one of them has an extended atmosphere, hydrogen, where perhaps we could detect water or methane steam. "But for the moment, at least for Trappist - 1 b and c, we have seen nothing", resumes the researcher
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Lazarus on 22nd February 2017, 6:59 pm

TRAPPIST-1d is dead.
The light curves obtained prior to 19 September 2016 allowed us to discard the eleven
possible periods of 'TRAPPIST-1d' 1 , indicating that the two observed transits originated from
different objects.

Long live the new TRAPPIST-1d!
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Lazarus on 23rd February 2017, 3:43 am

Study of the UV environment of the TRAPPIST-1 planets. An Earthlike atmosphere would result in similar levels of UV as those at the Earth, but anoxic and/or eroded atmospheres could make the environments on the TRAPPIST-1 planets very hostile.

O'Malley-James & Kaltenegger, "UV Surface Habitability of the TRAPPIST-1 System"
https://arxiv.org/abs/1702.06936
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by tommi59 on 23rd February 2017, 5:06 am

Very interesting   densities of the planets  b--3.64g/cm3  , c--6.45g/cm3  ,d--4.90g/cm3  ,e--4.41g/cm3 ,
f--3.31g/cm3  ,g--5.18g/cm3 .


Last edited by tommi59 on 23rd February 2017, 9:48 am; edited 1 time in total
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by tommi59 on 23rd February 2017, 5:35 am

Planet b  has  low density assessing distance to host star and size, likely water free (except night side) but with very small iron core.
Planet c  high density indicates it is  water free and  has larger than Earth iron content.
Planet d  composition similar to Earth with iron core and very small if any water  amount.
Planet e  bit smaller version of Earth density suggests water on surface and smaller than Earth iron core
Planet f   very likely water world  with large fraction of water between 15 and 25 %.
Planet g  Likely composition similar to Venus  may contain some water on surface or ice .Iron core likely smaller than Earth if water/ice free.
My opinions about planets composition assessing tentative mass measurement  by TTV   more measurement needed to measure masses more precisely.Masses by TTV are often underestimated comparing to RV.
I wonder if any of these planets could avoid tidal locking and are in 3:2 resonance like Mercury


Last edited by tommi59 on 23rd February 2017, 10:13 am; edited 1 time in total
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by tommi59 on 23rd February 2017, 8:34 am

http://www.eso.org/public/archives/releases/sciencepapers/eso1706/eso1706a.pdf
PDF paper about this amazing system ,how many more can we discover around this small star?
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Sirius_Alpha on 23rd February 2017, 5:05 pm

tommi59 wrote:I wonder if any of these planets could avoid tidal locking and are in 3:2 resonance like Mercury
Spin-orbit ratios other than unity require some eccentricity. Given how compact the TRAPPIST-1 system is, even a small amount of eccentricities in the orbits of the planets would cause a mess. Planets being tossed everywhere, etc.

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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Led_Zep on 23rd February 2017, 6:29 pm

Do you think that the planets can have satellites?
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Sirius_Alpha on 23rd February 2017, 9:30 pm

Any moon would have to orbit much, much closer than the synchronous orbit radius, which is not a long-term stable place for a moon because of tides dragging it into the planet (see: Phobos).

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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Stalker on 24th February 2017, 3:34 am

Also those planets are so close to each other you dont really need moons to make anything a moon does.

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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by tommi59 on 24th February 2017, 3:57 am

600 000 km the smallest distance between b and c planets ,both seen from each other twice larger than moon from Earth I can only guess how magnificent views are from all planets especially d and e
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by Led_Zep on 24th February 2017, 10:42 am

https://arxiv.org/abs/1702.07004

Reconnaissance of the TRAPPIST-1 exoplanet system in the Lyman-α line

The TRAPPIST-1 system offers the opportunity to characterize terrestrial, potentially habitable planets orbiting a nearby ultracool dwarf star. We performed a four-orbit reconnaissance with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope to study the stellar emission at Lyman-α , to assess the presence of hydrogen exospheres around the two inner planets, and to determine their UV irradiation. We detect the Lyman-α line of TRAPPIST-1, making it the coldest exoplanet host star for which this line has been measured. We reconstruct the intrinsic line profile, showing that it lacks broad wings and is much fainter than expected from the stellar X-ray emission. TRAPPIST-1 has a similar X-ray emission as Proxima Cen but a much lower Ly-α emission. This suggests that TRAPPIST-1 chromosphere is only moderately active compared to its transition region and corona. We estimated the atmospheric mass loss rates for all planets, and found that despite a moderate extreme UV emission the total XUV irradiation could be strong enough to strip the atmospheres of the inner planets in a few billions years. We detect marginal flux decreases at the times of TRAPPIST-1b and c transits, which might originate from stellar activity, but could also hint at the presence of extended hydrogen exospheres. Understanding the origin of these Lyman-α variations will be crucial in assessing the atmospheric stability and potential habitability of the TRAPPIST-1 planets.
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

Post by tommi59 on 24th February 2017, 2:37 pm

https://arxiv.org/pdf/1702.07327.pdf     Very interesting paper


If we take M⋆ = 0.08M⊙ and a = 0.03 AU, appropriate for the “habitable” planets around TRAPPIST-1 (Gillon et al. 2017), then the numerical factor in front of Eq. (57) becomes 1.4 × 1010 years, and that of Eq. (59) becomes 10−5 . This suggests that tidal dissipation cannot damp the planet’s eccentricity, and the planet can be sufficiently triaxial to allow for capture into the 3:2 resonance.
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Re: TRAPPIST-1 : Transiting Earth-Sized Planets Around a Nearby Ultracool Dwarf

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