Evidence for a large exomoon orbiting Kepler-1625b

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Evidence for a large exomoon orbiting Kepler-1625b

Post by Led_Zep on 3rd October 2018, 2:33 pm

http://advances.sciencemag.org/content/4/10/eaav1784

Abstract

Exomoons are the natural satellites of planets orbiting stars outside our solar system, of which there are currently no confirmed examples. We present new observations of a candidate exomoon associated with Kepler-1625b using the Hubble Space Telescope to validate or refute the moon’s presence. We find evidence in favor of the moon hypothesis, based on timing deviations and a flux decrement from the star consistent with a large transiting exomoon. Self-consistent photodynamical modeling suggests that the planet is likely several Jupiter masses, while the exomoon has a mass and radius similar to Neptune. Since our inference is dominated by a single but highly precise Hubble epoch, we advocate for future monitoring of the system to check model predictions and confirm repetition of the moon-like signal
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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Lazarus on 3rd October 2018, 3:16 pm

Definitely interesting if confirmed...

Cool Worlds YouTube has a couple of videos on the candidate:
EXOMOON SPECIAL | Evidence for an Exomoon around Kepler-1625b (presented by Alex Teachey)
EXOMOON SPECIAL | The Nature of our Exomoon Candidate (presented by David Kipping)

A sceptical take on it: https://twitter.com/exohugh/status/1047549905940750336

When's the next transit?
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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Sirius_Alpha on 3rd October 2018, 3:22 pm

Lazarus wrote:When's the next transit?
May of 2019, according to that first video.

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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Lazarus on 3rd October 2018, 5:21 pm

Thanks, serves me right for posting the link before watching the video Smile

Pretty sure there are going to be a bunch more analyses of the data in the meantime...
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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by siyul on 3rd October 2018, 10:59 pm

Teachey and Kipping’s transit data was gathered from Hubble observation during the October 29, 2017 transit of Kepler-1625b, and the latest transit of this planet just happened three weeks ago. Unfortunately, they did not schedule an observation for the latest transit but for the next transit on May 26, 2019. Considering the time of data processing, interpreting, writing, editing, peer-review, and publishing, the existence of Kepler-1625b-i will not be confirmed/discarded until the second half of 2020.

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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Edasich on 4th October 2018, 3:22 am

EPE is listing it as confirmed

http://exoplanet.eu/catalog/kepler-1625_b_i/

Nevertheless orbital period and parameters reported in EPE link are wrong. Latest research paper provides a 22-24 days period for the exomoon and orbital distance around 40 planet radii, i.e. around 0.019 or 0.033 AUs assuming a 10 MJup planetary host.
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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Lazarus on 4th October 2018, 1:29 pm

Yeap... https://twitter.com/aussiastronomer/status/1047580868221362176

Then again, most exoplanet catalogues aren't even set up to be able to represent binary and multiple stars in a reasonable manner and planets have been known in such systems for quite a while now.
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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Sirius_Alpha on 4th October 2018, 3:28 pm

Right? Maybe if more people were open to including the Solar System (should our planets count any less as planets?), this problem could have been avoided.

Edasich wrote:Nevertheless orbital period and parameters reported in EPE link are wrong. Latest research paper provides a 22-24 days period for the exomoon and orbital distance around 40 planet radii, i.e. around 0.019 or 0.033 AUs assuming a 10 MJup planetary host.
I think what they're doing is keeping the star-centric orbit for the moon, giving it literally the planet's orbit.

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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Led_Zep on 4th October 2018, 4:04 pm

https://twitter.com/NASAHubble/status/1047910639216340993

Hubble and @NASAKepler have found evidence of a potential exomoon! Join Hubble scientists live Friday, October 5th at 1 p.m. ET as they answer your questions about what this evidence could mean for the future of exploring new worlds outside our solar system. Use #AskNASA.
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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Sirius_Alpha on 7th October 2018, 8:25 pm

Now on arXiv, along with a paper about the habitability of moons around this planet.

Evidence for a Large Exomoon Orbiting Kepler-1625b
https://arxiv.org/abs/1810.02362

The habitable zone for Earthlike exomoons orbiting Kepler-1625b
https://arxiv.org/abs/1810.02712

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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Led_Zep on 7th October 2018, 9:46 pm

Sirius_Alpha wrote:Now on arXiv, along with a paper about the habitability of moons around this planet.

The habitable zone for Earthlike exomoons orbiting Kepler-1625b
https://arxiv.org/abs/1810.02712

Shocked
If Kepler-1625b-i is real, it is likely massive enough to possesses its own satellite (a \moon-moon"). If the said moon-moon was Earthlike, it could have resided in a moon- moon habitable zone during Kepler-1625's main sequence phase. The morphology of moon-moon habitable zones are not yet explored, but will share similarities with that of S-type binary star systems

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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Sirius_Alpha on 8th October 2018, 6:37 am

I'm highly skeptical of such a claim. Kepler-1625 b-i is likely tidally locked to its planet, making any orbits of such "moon-moons" below the synchronous orbit distance. Tides should work to lower the moon-moon's orbit until it merges with Kepler-1625b-i. This would be especially true if the moon-moon had a mass high enough to make it something more than a small Phobos-like rock.

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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Lazarus on 8th October 2018, 1:56 pm

I preferred the term "subsatellite" or "submoon" for these hypothetical objects. I'm in agreement with Sirius_Alpha that the tidal evolution of the system needs to be taken into account, for example Kepler-1625b-i may have been closer to the planet in the past and migrated outwards, which would reduce the region of stability when the system formed.

Hopefully Hubble's going to be in working order for the next transit...
http://nasawatch.com/archives/2018/10/hubble-space-te.html
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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Sirius_Alpha on 8th October 2018, 9:09 pm

A paper about the topic from tonight's arXiv postings.

Can Moons Have Moons?
https://arxiv.org/abs/1810.03304

Each of the giant planets within the Solar System has large moons but none of these moons have their own moons (which we call submoons). By analogy with studies of moons around short-period exoplanets, we investigate the dynamical stability of submoons. We find that 10 km-scale submoons can only survive around large (1000 km-scale) moons on wide-separation orbits. Tidal dissipation destabilizes the orbits of submoons around moons that are small or too close to their host planet; this is the case for most of the Solar System's moons. A handful of known moons are, however, capable of hosting long-lived submoons: Saturn's moons Titan and Iapetus, Jupiter's moon Callisto, and Earth's Moon. Based on its inferred mass and orbital separation, the newly-discovered exomoon candidate Kepler-1625b-I can, in principle, host submoons, although its large orbital inclination may pose a difficulty for dynamical stability. The existence, or lack thereof, of submoons, may yield important constraints on satellite formation and evolution in planetary systems.

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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Edasich on 9th October 2018, 4:07 am

We have seen Solar system moons with rings, so... why not? ;p
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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by tommi59 on 9th October 2018, 6:31 am

This is very unlikely there are any submoons elsewhere.There is discrepancy about star radius so we do not know for sure the moon is size of Neptune.
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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Sirius_Alpha on 9th October 2018, 12:05 pm

Edasich wrote:We have seen Solar system moons with rings, so... why not? ;p
Where? (Rhea's were disconfirmed)

Rings would be more tidally stable than moon-moons simply because rings don't raise an asymmetric tidal bulge on the moon to cause its orbit to drop.

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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Edasich on 9th October 2018, 12:18 pm

Sirius_Alpha wrote:
Edasich wrote:We have seen Solar system moons with rings, so... why not? ;p
Where? (Rhea's were disconfirmed)

Rings would be more tidally stable than moon-moons simply because rings don't raise an asymmetric tidal bulge on the moon to cause its orbit to drop.

Gotta have missed this piece of news. Embarassed

Anyway considering massive orbiting bodies like the alleged ones in Kepler-1625 system moon-submoon systems don't seem much unrealistic, especially at large separations close to Hill's sphere outer boundary.
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Re: Evidence for a large exomoon orbiting Kepler-1625b

Post by Lazarus on 9th October 2018, 4:36 pm

There was a suggestion that the equatorial ridge on Iapetus might be the result of evolution involving a submoon and rings around the moons, e.g. this paper.

tommi59 wrote:There is discrepancy about star radius
There was a substantial revision of the stellar parameters from Kepler DR24 to DR25 but this got confirmed with the Gaia DR2 results, no?
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Re: Evidence for a large exomoon orbiting Kepler-1625b

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