Kepler-78 (KIC 8435766) - Transiting Earth-sized planet in 8.5 hr orbit

*edit* Very short-period hot Earth?

Transits and occultations of an Earth-sized planet in an 8.5-hour orbit

Quote :

We report the discovery of an Earth-sized planet ($1.1\pm 0.2 R_\oplus$) in an 8.5-hour orbit around a late G-type star (KIC 8435766). The object was identified in a search for short-period planets in the Kepler database and confirmed to be a transiting planet (as opposed to an eclipsing stellar system) through the absence of ellipsoidal light variations or radial-velocity variations. The unusually short orbital period and the relative brightness of the host star ($m_{\rm Kep}$ = 11.5) enable robust detections of the changing illumination of the visible hemisphere of the planet, as well as the occultations of the planet by the star. We interpret these signals as representing a combination of reflected and reprocessed light, with the highest planet dayside temperatures in the range of 2300 K to 3100 K, and corresponding albedos of 0.6 to 0.2. Follow-up spectroscopy combined with shorter-cadence Kepler data will further pin down the system parameters and may even yield the mass of the planet.

It's a Earth-size planet and not Super-Earth size planet,people in our days talk so much about "super-Earth planets" that forget about the Earth-size and Sub Earth-size planets exoplanets...

Page 1 :
« …Here we report the detection of an Earth-sized planet with
an orbital period of 8.5 hr, resulting from our FT-based survey
of Kepler data. This system does not appear among the
Kepler Objects of Interest, supporting the notion that the standard
pipeline has missed some of the shortest-period planets… »

Page 2
« …A list of 20 potentially new short-period planet candidates
passed all these tests, with orbital periods between 4
and 16 hours. As expected, this list is comprised entirely of
objects smaller than Neptune. We will report on the entire collection
in a separate paper. For this initial report we chose to
focus on KIC 8435766, because it has the brightest host star,
one of the shortest orbital periods, and the most significant
detection of the illumination curve and occultations… »

Listed at EPE:

http://exoplanet.eu/catalog/kic_8435766_b/

Wow, that sounds like quite a nasty place, nothing on the KOI-55 planets though!

I have real trouble visualising these planets, the substellar point is glowing like an incandescent light bulb, but that pales in comparison to the illumination shining on it from the star... all the artworks depicting worlds like CoRoT-7b and Kepler-10b just seem to me to be woefully inadequate at conveying what these worlds must look like. (Though I suspect burning out people's retinas in the illustration for the press release would not be well-received).

Mercury is at least comprehensible...


Edited to add:

Edasich wrote:

Listed at EPE:

detected by microlensing!?!

Makes me wonder what else I miss when checking arXiv.
I've moved the posts about KIC 8435766 b into a separate thread.

Quote :

detected by microlensing!?!

Hurry may play nasty tricks...

Yes, looks like a bit of a mis-categorisation there!

I really have to wonder about why we have such a large empty gap between Mercury and the Sun, while these systems seem to have planets all the way down.

Sorry, couldn't resist.

Judging by the photo, they must be real...

8.5 hrs?!?!?! Yowza. What would the estimated temp be?

-M-

Sunchaser wrote:

Judging by the photo, they must be real...

8.5 hrs?!?!?! Yowza. What would the estimated temp be?

-M-

Just browse the preprint:

Quote :

[...]with the highest planet dayside temperatures in the range of 2300 K to 3100 K, and corresponding albedos of 0.6 to 0.2. [...]

However the shortest period Kepler candidate seems to be KOI-1843 with P_orb = 4.5 hours.

This one I think it was already announced in Kepler thread but now it is labeled as Kepler-78:
 
Transits and Occultations of an Earth-Sized Planet in an 8.5-Hour Orbit
 

Quote :

We report the discovery of an Earth-sized planet ($1.16\pm 0.19 R_\oplus$) in an 8.5-hour orbit around a late G-type star (KIC 8435766, Kepler-78).

Good catch, Edasich. I've renamed the thread.

Sirius_Alpha wrote:

Good catch, Edasich. I've renamed the thread.

 
Thanks, Sirius. Just a serendipitous find.
 
Good idea to divide the thread.

This one and KOI-1843.03 have now had a news release about them. Space.com

I'm still not entirely convinced by these depictions of the planets as glowing red balls of lava, it looks from figure 5 that the reflected light should be brighter than the thermal emission.

Looks like the mass is now determined. ~1.7 times Earth's mass, two independent studies.

Nature news story: Exoplanet is built like Earth but much, much hotter

Pepe et al. (2013) "An Earth-sized planet with an Earth-like density"
Using HARPS-N: 1.82 Earth masses (99% confidence range 1.12 – 2.51 Earth masses)

Howard et al. (2013) "A rocky composition for an Earth-sized exoplanet"
Using HIRES: 1.69 ± 0.41 Earth masses.

arXiv versions of the Nature papers are now online:

Pepe et al. (2013) - http://arxiv.org/abs/1310.7987
Howard et al. (2013) - http://arxiv.org/abs/1310.7988

Hatzes (arXiv 2014) "The Detection of Earth-mass Planets around Active Stars: The Mass of Kepler-78b"
http://arxiv.org/abs/1407.0853

Correcting for stellar activity gives a lower mass estimate 1.31 ± 0.24 M_⊕, suggesting an iron-deficient composition more like the Moon than Mercury.

…Which is within 1σ of both previous values.

Densities are hard. (harharhar puns)

New mass measurement for 8hours period planet http://arxiv.org/abs/1501.00369