55 Cancri e -- Transits detected!!

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55 Cancri e -- Transits detected!!

Post by Sirius_Alpha on 28th April 2011, 9:13 pm

A Super-Earth Transiting a Naked-Eye Star
http://arxiv.org/abs/1104.5230

We have detected transits of the innermost planet "e" orbiting 55 Cnc (V=6.0), based on two weeks of precise photometric monitoring with the MOST space telescope. The transits of 55 Cnc e occur with the period (0.74 d) and phase that had been predicted by Dawson & Fabrycky, and with the expected duration and depth for the crossing of a Sun-like star by a hot super-Earth. Assuming the star's mass and radius to be 0.96 +/- 0.10 Msun and 1.10 +/- 0.10 Rsun, the planet's mass, radius, and mean density are 8.57 +/- 0.64 Me, 1.63 +/- 0.16 Re, and 10.9 +/- 3.1 g/cm^3. The high density suggests the planet has a rock-iron composition as opposed to hydrogen, water, or other light elements. This makes 55 Cnc e similar to the other transiting super-Earths in tight orbits around G stars (Kepler-10b and Corot-7b), and unlike the lower-density super-Earths that are less strongly irradiated (GJ 1214b and Kepler-11d,e,f). The host star of 55 Cnc e is far brighter than that of any other known transiting planet, which will facilitate further investigations.

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Re: 55 Cancri e -- Transits detected!!

Post by exoplanet on 28th April 2011, 10:12 pm

Awesome, a huge ball of metal !


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Re: 55 Cancri e -- Transits detected!!

Post by Lazarus on 29th April 2011, 12:43 am

So it looks like the shorter orbital period suggested by the research into the possibility of aliasing is the correct one. I guess 55 Cancri e falls into a similar category of planet as Kepler-10b and CoRoT-7b, with a lava ocean.

Looks like it will be necessary to get more astrometric measurements of the outer planets to determine coplanarity.
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Re: 55 Cancri e -- Transits detected!!

Post by Edasich on 29th April 2011, 3:56 am

This is a very interesting discovery Very Happy

But I wonder, iron and nickel densities are around 7,8 and 8,9 g/cc, right? So what makes the density increase? A significant fraction of heavy metals inside?
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Re: 55 Cancri e -- Transits detected!!

Post by exoplanet on 29th April 2011, 4:25 am

compression.

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Re: 55 Cancri e -- Transits detected!!

Post by lodp on 29th April 2011, 4:46 am

Noticed that the EPE entry still gives the old alias period of 2.81 .... days rather than the period in later literature & the transit paper

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Re: 55 Cancri e -- Transits detected!!

Post by tommi59 on 29th April 2011, 5:54 am

Might they are going to look for transit of planet b as well is quite close
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Re: 55 Cancri e -- Transits detected!!

Post by Stalker on 29th April 2011, 6:11 am

F***ing awesome!

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Re: 55 Cancri e -- Transits detected!!

Post by Sirius_Alpha on 29th April 2011, 3:11 pm

tommi59 wrote:Might they are going to look for transit of planet b as well is quite close
Transits of b and c were already ruled out a few years ago.

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Re: 55 Cancri e -- Transits detected!!

Post by Borislav on 30th April 2011, 2:19 am

Miraculous coincidence Smile
http://planetquest.jpl.nasa.gov/news/cancri.cfm

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Re: 55 Cancri e -- Transits detected!!

Post by tommi59 on 30th April 2011, 4:42 am

So we can tell cancri e was discovered 2 days ago and previous one was a ghost Evil or Very Mad
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Re: 55 Cancri e -- Transits detected!!

Post by Lazarus on 30th April 2011, 8:45 am

Well it might actually be worth looking for the transits of the outer planets (d and f) now that we know that the inner planet is sufficiently well aligned to the line-of-sight. If planet f is a transiting planet then it might be a good candidate to search for habitable moons.

Of course, the astrometric results for planet d suggested an inclination of 53 degrees, but that was based on a partial orbit. On the other hand, if the planets of 55 Cancri A have substantial mutual inclinations that will be tricky to explain given the low orbital eccentricities.
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Re: 55 Cancri e -- Transits detected!!

Post by Edasich on 30th April 2011, 3:45 pm

I wonder if transit will be observed also for HD 156668 b, since Dawson & Fabrycky (2010) claimed actual orbital period of 2.1 days (I think) and smaller mass and orbital separation (0.017 or 0.021 AUs).
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Re: 55 Cancri e -- Transits detected!!

Post by Sirius_Alpha on 30th April 2011, 4:40 pm

It's definitely worth a look. I think the innermost planet at HD 69830 is still awaiting a transit check, too, though it's geometric transit probability is a bit lower.

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Re: 55 Cancri e -- Transits detected!!

Post by Edasich on 30th April 2011, 5:43 pm

Sirius_Alpha wrote:It's definitely worth a look. I think the innermost planet at HD 69830 is still awaiting a transit check, too, though it's geometric transit probability is a bit lower.

Well, Watson or Simpson et al. (2010) inferred an inclination of 13 degrees, quite difficult indeed. Rolling Eyes
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Re: 55 Cancri e -- Transits detected!!

Post by Sirius_Alpha on 1st May 2011, 6:07 pm

lodp wrote:Noticed that the EPE entry still gives the old alias period of 2.81 .... days rather than the period in later literature & the transit paper

I sent Mr. Schneider an e-mail about it, while also mentioning CFBDS 1458 b's 40-day period, Ross 458 b's existence in both the confirmed imaging planets and the unconfirmed planets, and WASP-51 and HAT-P-30 being separate entries.

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Re: 55 Cancri e -- Transits detected!!

Post by Edasich on 2nd May 2011, 4:17 am

Something has been edited indeed Smile
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Re: 55 Cancri e -- Transits detected!!

Post by tommi59 on 2nd May 2011, 9:39 am

Transit any small planets outside the area of mass loss due stellar radiation would tell us more.Any check for transit in HD 40307 system?? Anybody knows how it look like(possibility of transit) in gliese 581,876??
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Re: 55 Cancri e -- Transits detected!!

Post by Lazarus on 2nd May 2011, 3:28 pm

HD 40307b is apparently non-transiting (Gillon et al. 2010).

Transits of Gliese 581 b and c have been searched for without success (Lopez-Morales et al. 2006, also a news release about search for transits of c with apparently no published paper associated with it). I'm not aware of results for planets d or e though.

Dynamical modelling of Gliese 876 suggests the inclination is around 50 degrees, too low for transits to occur. Transits have been searched for but came up negative (Rivera et al. 2005, Shankland et al. 2006).
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Re: 55 Cancri e -- Transits detected!!

Post by exoplanet on 2nd May 2011, 4:17 pm

Speaking of naked-eye stars with transiting planets, does anyone know if a thorough search for transits has been made for lambda-2 fornacis ?

http://arxiv.org/abs/0902.4024

Another interesting possibility is 51 Pegasi b for which there have been some suggestions that an extended atmosphere similar to that of HD209458b may partially eclipse the star. This would require observations in the UV to detect if indeed there is any substance to these claims. It would be interesting though ...

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Re: 55 Cancri e -- Transits detected!!

Post by Lazarus on 2nd May 2011, 5:41 pm

I sent Mr. Schneider an e-mail about it, while also mentioning CFBDS 1458 b's 40-day period, Ross 458 b's existence in both the confirmed imaging planets and the unconfirmed planets, and WASP-51 and HAT-P-30 being separate entries.
Stellar masses of CFBDS 1458 and DH Tauri are also highly suspect...

Oph 11 is wrong by a factor of 10 but it doesn't jump out quite as much.
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Re: 55 Cancri e -- Transits detected!!

Post by Sirius_Alpha on 2nd May 2011, 9:07 pm

Very different planetary properties from Spitzer, however:

Detection of a transit of the super-Earth 55 Cnc e with Warm Spitzer
http://arxiv.org/abs/1105.0415

We report on the detection of a transit of the super-Earth 55 Cnc e with Warm Spitzer in IRAC's 4.5-micron band. Our MCMC analysis includes an extensive modeling of the systematic effects affecting Warm Spitzer photometry, and yields a transit depth of 450 +- 50 ppm, which translates to a planetary radius of 2.13 +- 0.14 Earth Radii as measured in IRAC 4.5-micron channel. A planetary mass of 7.98 +- 0.69 Earth Masses is derived from an extensive set of radial-velocity data, yielding a planetary density of 0.83 +- 0.18 Earth density. Interestingly, the derived radius is 1.3 times larger than the one recently reported in the visible by Winn et al. Thanks to the brightness of its host star (V=6, K=4), 55 Cnc e is a unique target for the thorough characterization of a super-Earth orbiting around a solar-type star.

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Re: 55 Cancri e -- Transits detected!!

Post by Lazarus on 3rd May 2011, 2:19 am

Er, wow. And that's derived using a smaller assumed radius for the star.

Given the planet is strongly-irradiated by the star, I'd guess that a volatile-rich composition is less plausible than the rock/iron structure suggested by the optical transit, but I guess we have to wait for follow-up studies.
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Re: 55 Cancri e -- Transits detected!!

Post by Edasich on 3rd May 2011, 4:37 am

Lazarus wrote:Er, wow. And that's derived using a smaller assumed radius for the star.

Given the planet is strongly-irradiated by the star, I'd guess that a volatile-rich composition is less plausible than the rock/iron structure suggested by the optical transit, but I guess we have to wait for follow-up studies.

Authors indeed infer following composition to account for larger radius:

- 0.1% H2-He
- 20% H2O
- 79% Silicates and Iron (assuming "fifty-fifty" ratio as in Earth's case).
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Re: 55 Cancri e -- Transits detected!!

Post by Stalker on 3rd May 2011, 5:15 am

If i understand, we have a rocky planet with an extended atmosphere of H2O who block infrared radiations?

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