Kepler News and Results

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Re: Kepler News and Results

Post by Led_Zep on 8th January 2013, 6:09 am

« The false positive rate of Kepler and the occurrence of planets »

http://arxiv.org/abs/1301.0842

For the Kepler team, the average rate is 9.4 %
In particular 17.7 % for giant planets : OHP with SOPHIE found 35 %

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Re: Kepler News and Results

Post by Lazarus on 8th January 2013, 1:56 pm

So the false positive rate is lowest for "small Neptunes"? Causes a few revisions of some of the emerging trends of planet occurrence...
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Re: Kepler News and Results

Post by Led_Zep on 8th January 2013, 6:39 pm


http://spaceref.com/extrasolar-planets-1/earth-size-planets-are-common-in-our-galaxy.html#more

« …Petigura spent the past two years writing a software program called TERRA, for Transiting ExoEarth Robust Reduction Algorithm, which is very similar to Kepler's pipeline. The UC Berkeley/Hawaii team then fed TERRA simulated planets to test how efficiently the software detects Earth-size planets… »

The paper :
http://astro.berkeley.edu/~petigura/eta-earth.pdf
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Re: Kepler News and Results

Post by Sirius_Alpha on 9th January 2013, 9:41 pm


No evidence so far for exomoons. Unsurprising results.

We also derive precise transit times and durations for each candidate and find no evidence for dynamical variations in any of the KOIs. With just a few systems analyzed thus far in the in-going HEK project, projections on eta-moon would be premature, but a high frequency of large moons around Super-Earths/Mini-Neptunes would appear to be incommensurable with our results so far.

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Re: Kepler News and Results

Post by Lazarus on 10th January 2013, 2:52 am

Maybe worth splitting off the exomoons into their own thread?

---

Not entirely surprised that super-Earths and mini-Neptunes don't seem to have large moons. Pity though, would have been nice to have good prospects for Kepler-47c. Incidentally anyone know if searches for ring systems are going on?
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Re: Kepler News and Results

Post by AVBursch on 10th January 2013, 8:24 am

Any moons orbiting super-Earths and mini-Neptunes are likely to be dwarf planet size. For example, the four largest moons orbiting Uranus -- Titania, Oberon, Ariel, and Umbriel, range from 10% to 27% of the mass of Pluto. Neptune is likely an anomaly as its large moon Triton was captured from the Kuiper belt population.

Surveys for exo-moons so far appear to indicate that Jupiter, Saturn, and Uranus are representative of what a typical satellite system is expected to look like -- the moons form along with the planet.

Moons orbiting Kepler-47c, for example, are expected to be comparable to Haumea and Makemake in size, making them undetectable by Kepler.


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Re: Kepler News and Results

Post by jyril on 10th January 2013, 8:56 am

That is true, but moons could be detected indirectly through the gravitational effect on the parent planet.

Large moons should be directly detectable, and there are gas giants in the sample which could harbor large moons.

Of course, migrations of the planets or in situ formation near the star are probably very hostile to any satellites.

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Re: Kepler News and Results

Post by Daniel on 10th January 2013, 9:29 am

Still too premature for jump to a definitive conclusions about Earth-size exomoons around Jupiter-size planets,it's only been analyse 7 planet candidates by HEK,and they are Mini-Neptunes/Super-Earths


Last edited by Daniel on 10th January 2013, 1:18 pm; edited 1 time in total
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Re: Kepler News and Results

Post by Kodas on 10th January 2013, 10:16 am

AVBursch wrote:Any moons orbiting super-Earths and mini-Neptunes are likely to be dwarf planet size. For example, the four largest moons orbiting Uranus -- Titania, Oberon, Ariel, and Umbriel, range from 10% to 27% of the mass of Pluto. Neptune is likely an anomaly as its large moon Triton was captured from the Kuiper belt population.

Surveys for exo-moons so far appear to indicate that Jupiter, Saturn, and Uranus are representative of what a typical satellite system is expected to look like -- the moons form along with the planet.

The Kepler data is the first survey where it is even barely feasible to detect moons of any size, and the HEK team are the only ones so far to perform a serious analysis. It is entirely unknown whether in-situ formation (the HEK team calls them "regular" satellites) which produces relatively small moons in relation to their host like the Galileans is more common, or whether "irregular" formation is (through a variety of processes like planet capture e.g. Triton/Charon or impacts e.g. Moon). Indeed the funky dynamics of many systems discovered thus far implies "irregular" satellites probably have plenty of chances to occur.

Kepler could only feasibly detect "irregular" satellites as they can be larger, and even then in only a handful of systems from the entire Kepler target list with a suitable planet and low-enough noise. The problem here is the planets that HEK have looked at, while being in some ways suitable for observing exomoons, are entirely the wrong planets as far as we know for them to form in the first place.

As far as I can tell all of these have at least G and K dwarf stars, so not that small. The ones which are claimed to be smaller in the paper based on the KIC are actually not, the revised values being used by the Kepler team in the latest release show these were wildly inaccurate. None of the selected planets have periods above 90 days, and all but one are relatively tiny super-earths. In other words the Hill radius of these planets is going to be vanishingly small. It's no wonder these don't have large (irregular) moons, they could realistically never capture any or hold onto any blasted off their surface. There is a reason all the irregular moons in the Solar System are around planets with orbits much longer than 90 days...

So really this study doesn't tell us anything we didn't know already. What will be interesting to see is if irregular moons don't form where it is actually possible for them to. This is going to be difficult for Kepler to answer as it needs planets with relatively long periods, but with enough transits to tease out the exomoon signals.


PS: Saturn's Titan could be described as irregular too as it is probably the result of a cataclysmic event in a previously regular system, Saturn's moons are possibly "second generation". So actually there seem to be more irregular systems than there are regular.


Last edited by Kodas on 10th January 2013, 8:36 pm; edited 2 times in total

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Re: Kepler News and Results

Post by Lazarus on 10th January 2013, 2:16 pm

Kodas wrote:PS: Saturn's Titan could be described as irregular too as it is probably the result of a cataclysmic event in a previously regular system, Saturn's moons are possibly "second generation". So actually there are more irregular systems than there are regular.
On the other hand large collisions may be the rule rather than the exception in regular satellite systems (and formation of terrestrial/super-Earth systems for that matter). Miranda certainly seems to have had some interesting history...
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Re: Kepler News and Results

Post by Daniel on 12th January 2013, 2:59 pm

Look this interesting Article About exomoons habitability:

Exomoon habitability constrained by illumination and tidal heating

http://arxiv.org/ftp/arxiv/papers/1209/1209.5323.pdf

especially on the section 2.1 About formation of Earth-size around Jupiter-size planets:

2.1 Formation of massive satellites

The largest and most massive moon in the Solar System, Ganymede, has a radius of only " 0.4R! (R! being the radius of
the Earth) and a mass of " 0.025M!. The question whether much more massive moons could have formed around extrasolar
planets is an active area of research. Canup & Ward (2006) have shown that moons formed in the circum-planetary disk of
giant planets have masses ≲ 10-4
times that of the planet’s mass. Assuming satellites formed around Kepler-22b, their masses will thus be 2.5 & 10
-3M! at most and around KOI211.01 they will still weigh less than the Earth’s Moon. Massconstrained in-situ formation becomes critical for exomoons around planets in the IHZ of low-mass stars because of the observational lack of such giant planets. An excellent study on the formation of the Jovian and the Saturnian satellite systems is given by Sasaki et al. (2010), who showed that moons of sizes similar to Io, Europa, Ganymede, Callisto, and
Titan should build up around most gas giants. What is more, according to their Fig. 5 and private communication with
Takanori Sasaki, formation of Mars- or even Earth-mass moons around giant planets is possible. Depending on whether or
not a planet accretes enough mass to open up a gap in the protostellar disk, these satellite systems will likely be multiple and
resonant (as in the case of Jupiter), or contain only one major moon (see Saturn). Ogihara & Ida (2012) recently extended
these studies to explain the compositional gradient of the Jovian satellites. Their results explain why moons rich in water are
further away from their giant host planet and imply that capture in 2:1 orbital resonances should be common.
Ways to circumvent the impasse of insufficient satellite mass are the gravitational capture of massive moons (Debes &
Sigurdsson 2007; Porter & Grundy 2011; Quarles et al. 2012), which seems to have worked for Triton around Neptune
(Goldreich et al. 1989; Agnor & Hamilton 2006), capture of Trojans (Eberle et al. 2011), gas drag in primordial circumplanetary envelopes (Pollack et al. 1979), pull-down capture trapping temporary satellites or bodies near the Lagrangian
points into stable orbits (Heppenheimer & Porco 1977; Jewitt & Haghighipour 2007), the coalescence of moons (Mosqueira
& Estrada 2003), and impacts on terrestrial planets (Canup 2004; Withers & Barnes 2010; Elser et al. 2011). Such moons
would correspond to the irregular satellites in the Solar System, as opposed to regular satellites which form in situ. Irregular
satellites often follow distant, inclined, and often eccentric or even retrograde orbits about their planet (Carruba et al. 2002).
For now, we assume that Earth-mass extrasolar moons – be they regular or irregular – exist.

The Sasaki article:

http://sasakitakanori.com/wp-content/uploads/2010/04/apj_2010_satellite.pdf

So lets hope that Kepler with exomoons hunts projects like HEK confirm it by Observation


Last edited by Sirius_Alpha on 12th January 2013, 8:49 pm; edited 2 times in total (Reason for editing : Formatting - Sirius_Alpha)
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Re: Kepler News and Results

Post by Sirius_Alpha on 13th January 2013, 9:12 pm

Candidate Planets in the Habitable Zones of Kepler Stars
http://arxiv.org/abs/1301.2384

Kepler's Missing Planets
http://arxiv.org/abs/1301.2394

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Re: Kepler News and Results

Post by Lazarus on 14th January 2013, 3:21 pm

Sirius_Alpha wrote:Candidate Planets in the Habitable Zones of Kepler Stars
http://arxiv.org/abs/1301.2384
Going to have to rerun that for the newest dataset...
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Re: Kepler News and Results

Post by Kodas on 14th January 2013, 3:55 pm

Lazarus wrote:
On the other hand large collisions may be the rule rather than the exception in regular satellite systems (and formation of terrestrial/super-Earth systems for that matter). Miranda certainly seems to have had some interesting history...

True, though at that point we are getting into semantics. The point is there are many ways to build up larger moons than you might expect from pure in-situ models.

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Re: Kepler News and Results

Post by Kodas on 14th January 2013, 3:56 pm

Lazarus wrote:
Going to have to rerun that for the newest dataset...

It does use the latest dataset, but strangely not the updated Teff values so it's going to be wildly inaccurate.

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Re: Kepler News and Results

Post by Lazarus on 14th January 2013, 4:11 pm

Wait, what?

I'm confused now...

The paper talks of "A revised and expanded catalog of 2740 confirmed and candidate planets around 2036 Kepler stars was released on 7 January 2012."

However as far as I can tell the KOI catalogue from 26 February 2012 contained only 2321 candidates.

So is this a typo for 7 January 2013?

The table available here has 3540 candidates.

???

Edited to add: (Can you get 2740 by filtering on disposition?)
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Re: Kepler News and Results

Post by Kodas on 14th January 2013, 4:24 pm

Yes it's just a typo based on the rest of the statements, it's clearly referring to the latest release.

The new lists include false positives, this is why the press releases only claim 2740 candidates. Btw, use the cumulative list,
here, as for some reason the Q1-Q8 list doesn't seem to list everything. Question

Yes, you need to filter by "Candidate" and then by "Confirmed" and sum the results to get 2740.

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Re: Kepler News and Results

Post by Lazarus on 14th January 2013, 4:35 pm

Ah and also the dispositions are different between the two tables, hence my confusion. Thanks!
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Re: Kepler News and Results

Post by Lazarus on 14th January 2013, 5:34 pm

Kodas wrote:It does use the latest dataset, but strangely not the updated Teff values so it's going to be wildly inaccurate.
Looks like he's rederiving the temperatures and other stellar properties from the magnitudes using evolutionary models rather than using the published Teff values. I'm not sure that's necessarily going to result in "wildly inaccurate" conclusions.
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Re: Kepler News and Results

Post by Sirius_Alpha on 18th January 2013, 12:21 am

New Kepler mission update. More reaction wheel issues.

Earlier this month during a semi-weekly contact with the spacecraft, the team detected an increase in the amount of torque required to spin one of the three remaining reaction wheels. This increase in friction occurred before the Jan. 11, 2013 quarterly roll, and persisted after the spacecraft roll and several momentum desaturations of the reaction wheels. Increased friction over a prolonged period can lead to accumulated wear on the reaction wheel, and possible wheel failure. To minimize wheel friction, the team implemented several mitigations including increased operating temperatures, higher spin rates, and bi-directional operation following the failure of reaction wheel #2 in July 2012.
Given the persistence of this recent event in reaction wheel #4, the project team will place the Kepler spacecraft in a "wheel rest" safe mode for a period of ten days beginning today. Science data collection will be stopped during this period and the spacecraft solar panel orientation will be aligned with the sun to maintain positive power for Kepler. This is similar to a normal safe mode configuration, but with thrusters maintaining attitude instead of reaction wheels. Resting the wheels provides an opportunity to redistribute internal lubricant, potentially returning the friction to normal levels.
Once the 10-day rest period ends, the team will recover the spacecraft from this resting safe mode and return to science operations. That is expected to take approximately three days. An update will be posted after the wheel rest operation is complete.

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Re: Kepler News and Results

Post by Lazarus on 22nd January 2013, 4:50 pm

New observations of the hot Jupiter system HAT-P-7 (Kepler-2). The tidal bulge induced on the star may be detectable through gravity darkening (!).

Kepler's Optical Secondary Eclipse of HAT-P-7b and Probable Detection of Planet-Induced Stellar Gravity Darkening
http://arxiv.org/abs/1301.4503
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Re: Kepler News and Results

Post by Lazarus on 28th January 2013, 3:43 pm

Transit Timing Observations from Kepler. VIII Catalog of Transit Timing Measurements of the First Twelve Quarters
http://arxiv.org/abs/1301.5499

Transit timing variations (TTV), duration variations (TDV) and depth variations (TPV) for Kepler Objects of Interest.
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Re: Kepler News and Results

Post by Led_Zep on 29th January 2013, 6:04 pm

KEPLER is back in action :
http://www.space.com/19536-nasa-exoplanets-kepler-spacecraft-glitch.html

cheers
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Re: Kepler News and Results

Post by PlutonianEmpire on 4th February 2013, 11:48 pm

I think I recall that there was a brief mention a few months back, that based on results so far, there was not a single earth size planet in the habitable zone *anywhere* in the kepler sample, and that the teams working on kepler would have a meeting or conference about it during the month of January. Was this correct? If so, did any news or articles come out of it, considering January's over now?

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Re: Kepler News and Results

Post by Sirius_Alpha on 5th February 2013, 12:32 am

So said the rumours and unpublished abstracts. I saw no publications or anything really official about it.

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