Kepler-10: Kepler's first confirmed solid super-Earth in a 2-planet system

In any case, the main achievement - the first a detect of the secondary eclipse and phase curve a super-Earth.

http://www.nasa.gov/pdf/509370main_Batalha_N_Kepler-10b.pdf

Quote :

The phase curve amplitude of Kepler-10b is 7.6 ± 2.0 ppm (See Table 7). If due to scattered light alone, this corresponds to a Kepler bandpass effective geometric albedo of 0.68. The occultation depth is 5.8 ± 2.5 ppm which corresponds to an effective geometric albedo of 0.61 ± 0.17. This is an unusually high albedo. The only known solar system bodies that are so bright are Venus (due to photochemically induced hazes) and Saturns icy moon Enceladus (coated with fresh ice). Kepler-10b is likely too hot for any hazes and is certainly too hot for any ice. Another possibility is that Kepler-10b has silicate clouds, but they would have to be completely covering the planet’s day side and have a large particle size in order to provide the required reflectivity (see, for example, Seager, Whitney, & Sasselov (2000)).

Some of the presentations from the Rencontres du Vietnam conference are up. I'm going through them now. Cameron's paper describes a HARPS-N mass measurement for Kepler-10 c, it seems the planet is rather dense for its mass, the paper itself uses the term "rocky Neptune?"

Massive planetary core w. the gas stripped away?

-M-

Probably c is the densest planet with radius over 2 earth beyond significant mass loss zone.Atmosphere stripped away? Not necessary simply planet c has not accreted any hydrogen envelope.

Guess a mass of kepler 22b now  

It can simply be the rocky version of HD149026 b.

Not good comparison as kepler 10c is 2.3 earth radius and can be easily classified as large dense super earth still much smaller than neptune and HD149026 b. has a saturn size with 5 times smaller density.Kepler 10 c is similar to 55 cancri e

Except that 10c is a bit more massive than 55e. It is hard for me to think of a planet as massive as Uranus without a h/he envelope. I think 20b and 10c are a type of planet with a negligible envelope over a massive core. A stripped away atmosphere may explain that but then why haven't more examples been found?

Now on arXiv!

The Kepler-10 planetary system revisited by HARPS-N: A hot rocky world and a solid Neptune-mass planet
http://arxiv.org/abs/1405.7881

Quote :

Kepler-10b was the first rocky planet detected by the Kepler satellite and con- firmed with radial velocity follow-up observations from Keck-HIRES. The mass of the planet was measured with a precision of around 30%, which was insufficient to constrain models of its internal structure and composition in detail. In addition to Kepler-10b, a second planet transiting the same star with a period of 45 days was sta- tistically validated, but the radial velocities were only good enough to set an upper limit of 20 Mearth for the mass of Kepler-10c. To improve the precision on the mass for planet b, the HARPS-N Collaboration decided to observe Kepler-10 intensively with the HARPS-N spectrograph on the Telescopio Nazionale Galileo on La Palma. In to- tal, 148 high-quality radial-velocity measurements were obtained over two observing seasons. These new data allow us to improve the precision of the mass determina- tion for Kepler-10b to 15%. With a mass of 3.33 +/- 0.49 Mearth and an updated radius of 1.47 +0.03 -0.02 Rearth, Kepler-10b has a density of 5.8 +/- 0.8 g cm-3, very close to the value -0.02 predicted by models with the same internal structure and composition as the Earth. We were also able to determine a mass for the 45-day period planet Kepler-10c, with an even better precision of 11%. With a mass of 17.2 +/- 1.9 Mearth and radius of 2.35 +0.09 -0.04 Rearth, -0.04 Kepler-10c has a density of 7.1 +/- 1.0 g cm-3. Kepler-10c appears to be the first strong evidence of a class of more massive solid planets with longer orbital periods.

Wow. 3 times more gravity than Earth and 1.22 times than Jupiter.   

I wonder what it looks like. I think the geological activity must be extreme.

Here on arxiv the mass is even higher 17.2 than revealed recently 14.4.More examples of such planets will rarely appear example kepler 131b.However lack of planets between b and c in kepler 10 system can lead to conclusion that something happened in that system.What is interesting both planets k10c and k131b are around very similar stars and away from significant mass loss zone what a pity there is no more than 1 planets in both system

Guys, did you see this? It also went up today.

Top paragraph of page 5:

Quote :

If correct, this predicts the existence of more massive rocky exoplanets at longer orbital periods.

Then look at figure 2… Kepler-10c goes about here:



Look at the error bars on the bins. Maybe c isn't that surprising? Not many small transiting planets have had their masses measured at high precision beyond 10 days, so more examples could quite possibly verify this implication.

(What kind of strange universe have I walked into where science happens overnight?!)

tommi59 wrote:

Not good comparison as kepler 10c is 2.3 earth radius and can be easily classified as large dense super earth still much smaller than neptune  and HD149026 b. has a saturn size with 5 times smaller density.Kepler 10 c is similar to 55 cancri e

My apologies for the mistake, I used some old data about HD149026 b. I seriously need to get back at planet hunting.

You do not need to apologize   .HD 149026 is very dense for planets 5-9 earth radii despite only 1.25g/cm3 . Three regimes are just general and seems to be true ,but in many cases can not be so precise as we have some planets with extremely low density and very high density .I think metallicity of stars is not main factor of planet density as some different amount of material is available around various type of stars.Many systems can experience coliisional stripping itc.We have some freak cases like kepler 138 c and kepler10 c not mentioning about kepler 51 planets.

They suggest 5-20% by mass as ices. So perhaps high pressure ice overlain by a deep supercritical steam atmosphere?

BUT we know in Uranus and Neptune that the high-Z material is NOT solid, presumably because there's enough hydrogen mixed in down there that disrupts formation of the solid, leaving it as some kind of fluid state (presumably supercritical/superionic/?). So the question is whether the ice on Kepler-10c might also not be in the solid state despite being in temperature/pressure conditions that would solidify pure water. Could enough hydrogen remain dissolved in the interior to disrupt the formation of ice while simultaneously not contributing to the outer atmosphere?

In any case, to me it seems unlikely that it would look like the rocky planet depicted in the press release.

That does seem unlikely...are those oceans I saw?

-M-

Maybe there is no water at all if is no hydrogen? what is C/O ratio of the star may contain some carbon as planets could rise in poor oxygen and hydrogen environment,Does we know gravitational compression in this case?With low ratio mg/s to fe it is quite likely there is no water.I wait for precise mass measurement for kepler131 b it would be interesting case also

Caroline Terquem, "On the formation of the Kepler-10 planetary system"
http://arxiv.org/abs/1407.7682

Suggests that the two planets probably formed at a few AU from the star, and that the Kepler-10 system may not be particularly unusual, though probably the result of a rather massive protoplanetary disc.

Revised Masses and Densities of the Planets around Kepler-10
http://arxiv.org/abs/1601.06168

Quote :

Determining which small exoplanets have stony-iron compositions is necessary for quantifying the occurrence of such planets and for understanding the physics of planet formation. Kepler-10 hosts the stony-iron world Kepler-10b (K10b), and also contains what has been reported to be the largest solid silicate-ice planet, Kepler-10c (K10c). Using 220 radial velocities (RVs), including 72 precise RVs from Keck-HIRES of which 20 are new from 2014-2015, and 17 quarters of Kepler photometry, we obtain the most complete picture of the Kepler-10 system to date. We find that K10b (Rp=1.47 Re) has mass 3.72±0.42 Me and density 6.46±0.73 g/cc. Modeling the interior of K10b as an iron core overlaid with a silicate mantle, we find that the iron core constitutes 0.17±0.11 of the planet mass. For K10c (Rp=2.35 Re) we measure Mp=13.98±1.79 Me and ρ=5.94±0.76 g/cc, significantly lower than the mass computed in Dumusque et al. (2014, 17.2±1.9 Me). Internal compositional modeling reveals that at least 10% of the radius of Kepler-10c is a volatile envelope composed of hydrogen-helium (0.2% of the mass, 16% of the radius) or super-ionic water (28% of the mass, 29% of the radius). Analysis of only HIRES data yields a higher mass for K10b and a lower mass for K10c than does analysis of the HARPS-N data alone, with the mass estimates for K10c formally inconsistent by 3σ. Splitting the RVs from each instrument leads to inconsistent measurements for the mass of planet c in each data set. This suggests that time-correlated noise is present and that the uncertainties in the planet masses (especially K10c) exceed our formal estimates. Transit timing variations (TTVs) of K10c indicate the likely presence of a third planet in the system, KOI-72.X. The TTVs and RVs are consistent with KOI-72.X having an orbital period of 24, 71, or 101 days, and a mass from 1-7 Me.

Some work toward resolving the mass discrepancy for Kepler-10c

Pinning down the mass of Kepler-10c: the importance of sampling and model comparison
https://arxiv.org/abs/1707.06192

Quote :

Initial RV characterisation of the enigmatic planet Kepler-10c suggested a mass of ∼17 M⊕, which was remarkably high for a planet with radius 2.32 R⊕; further observations and subsequent analysis hinted at a (possibly much) lower mass, but masses derived using RVs from two different spectrographs (HARPS-N and HIRES) were incompatible at a 3σ-level. We demonstrate here how such mass discrepancies may readily arise from sub-optimal sampling and/or neglecting to model even a single coherent signal (stellar, planetary, or otherwise) that may be present in RVs. We then present a plausible resolution of the mass discrepancy, and ultimately characterise Kepler-10c as having mass 7.37+1.32−1.19 M⊕, and mean density 3.14+0.63−0.55 g cm−3.

They also consider the non-transiting candidate KOi-72.X, the combined HARPS+HIRES model gives a period of 102±1 days and a mass of 5.90^+1.70_-1.01 Earth masses.