Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by Edasich on 22nd November 2011, 4:09 am

http://kepler.nasa.gov/Mission/discoveries/

Kepler-21 b - 1.6 Earth radii
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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by Lazarus on 22nd November 2011, 4:33 am

Brightest star with a Kepler-nn planet.

http://kepler.nasa.gov/Mission/discoveries/kepler21b/

Host star is bright enough to have been included in the Henry Draper catalogue: HD 179070
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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by Stalker on 22nd November 2011, 3:12 pm

WOW a super earth around a subgiant star, more massive, huge and hot thant sun! This planet seem to be even more roasted than 55 Cnc e!

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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by Sirius_Alpha on 22nd November 2011, 3:37 pm

Excellent news. This shows that there are transiting low-mass planets around bright stars, we've just got to find them (TESS advocation).

We've now got three super-Earths transiting decently bright (accessible) stars, 55 Cnc e, HD 97658 b, and now Kepler-21 b. I wonder if any of them are as easy to study as GJ 1214 b. It would be an issue of target brightness versus high Rpl/Rstar.

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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by Lazarus on 1st December 2011, 1:08 pm

Kepler-21b press release
Mission Manager's Update: Circumbinary planets! ...and Kepler Science Conference - still pushing the "Kepler-16b is the first known circumbinary planet" line I see...
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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by tommi59 on 1st December 2011, 3:55 pm

No mass kepler 21 b determined.Does anybody know any part of kepler conference can be watched in nasa tv or anywhere else?
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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by Daniel on 1st December 2011, 5:33 pm

what about Kepler-13 system?

I just saw kepler-13 in the Kepler field photos on the Kepler Science Conference schedule and abstracts, but they did say nothing about this system... Question

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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by Sirius_Alpha on 11th December 2011, 9:20 pm

Kepler-21b paper here on arXiv.

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Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by Sirius_Alpha on 26th February 2012, 9:18 pm

Validation of the Exoplanet Kepler-21b using PAVO/CHARA Long-Baseline Interferometry
http://arxiv.org/abs/1202.5307

We present long-baseline interferometry of the Kepler exoplanet host star HD179070 (Kepler-21) using the PAVO beam combiner at the CHARA Array. The visibility data are consistent with a single star and exclude stellar companions at separations ~1-1000 mas (~ 0.1-113 AU) and contrasts < 3.5 magnitudes. This result supports the validation of the 1.6 R_{earth} exoplanet Kepler-21b by Howell et al. (2012) and complements the constraints set by adaptive optics imaging, speckle interferometry, and radial velocity observations to rule out false-positives due to stellar companions. We conclude that long-baseline interferometry has strong potential to validate transiting extrasolar planets, particularly for future projects aimed at brighter stars and for host stars where radial velocity follow-up is not available.

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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by Sirius_Alpha on 26th September 2016, 8:39 pm

Kepler-21b: A rocky planet around a V = 8.25 magnitude star
http://arxiv.org/abs/1609.07617

HD 179070, aka Kepler-21, is a V = 8.25 F6IV star and the brightest exoplanet host discovered by Kepler. An early detailed analysis by Howell et al. (2012) of the first thirteen months (Q0 - Q5) of Kepler light curves revealed transits of a planetary companion, Kepler-21b, with a radius of about 1.60 +/- 0.04 R_earth and an orbital period of about 2.7857 days. However, they could not determine the mass of the planet from the initial radial velocity observations with Keck-HIRES, and were only able to impose a 2-sigma upper limit of 10 M_earth. Here we present results from the analysis of 82 new radial velocity observations of this system obtained with HARPS-N, together with the existing 14 HIRES data points. We detect the Doppler signal of Kepler-21b with a radial velocity semi-amplitude K = 2.00 +/- 0.65 m/s, which corresponds to a planetary mass of 5.1 +/- 1.7 M_earth. We also measure an improved radius for the planet of 1.639 (+0.019, -0.015) R_earth, in agreement with the radius reported by Howell et al. (2012). We conclude that Kepler-21b, with a density of 6.4 +/- 2.1 g/cm^3, belongs to the population of terrestrial planets with iron, magnesium silicate interiors, which have lost the majority of their envelope volatiles via stellar winds or gravitational escape. The radial velocity analysis presented in this paper serves as example of the type of analysis that will be necessary to confirm the masses of TESS small planet candidates.

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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by tommi59 on 27th September 2016, 6:19 am

Again planet straddling transition but with high incident flux -rather useless as we need planets with equilibrium temperature less than 750 K
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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by Lazarus on 27th September 2016, 5:07 pm

What's a useful exoplanet anyway, it looks pretty unlikely that we're ever going to get to any of them...
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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

Post by tommi59 on 28th September 2016, 4:05 am

I meant is less valuable as we do not know whether planet lost envelope due stellar proximity or never had and was already dense after the birth
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Re: Kepler-21 - Transiting super-Earth around a bright (V = 8.27) F-type Star

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