Transiting hot Uranus at GJ 3470

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Transiting hot Uranus at GJ 3470

Post by Sirius_Alpha on 25th June 2012, 8:20 pm

A hot Uranus transiting the nearby M dwarf GJ3470. Detected with HARPS velocimetry. Captured in transit with TRAPPIST photometry
http://arxiv.org/abs/1206.5307

We report on the discovery of GJ3470b, a transiting hot Uranus of mass m_p = 14.0+-1.8 Mearth, radius R_p = 4.2+-0.6 Rearth and period P=3.3371+-0.0002 day. Its host star is a nearby (d=25.2+-2.9pc) M1.5 dwarf of mass M_s=0.54+-0.07 Msol and radius R_s=0.50+-0.06 Rsol. The detection originates from a radial-velocity campaign with HARPS that focused on the search for short-period planets orbiting M dwarfs. Once the planet was discovered and the transit-search window narrowed to about 10% of an orbital period, a photometric search started with TRAPPIST and quickly detected the ingress of the planet. Additional observations with TRAPPIST, EulerCam and NITES definitely confirmed the transiting nature of GJ3470b and allow for the determination of its true mass and radius. The star's visible or infrared brightness (V=12.3, K=8.0 mag), together with a large eclipse depth D=0.57+-0.05%, ranks GJ3470b among the most favorable planets for follow-up characterizations.

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Re: Transiting hot Uranus at GJ 3470

Post by tommi59 on 26th June 2012, 2:07 am

Nice find quite close.Planets max equilibrum temp is 615 K so no significant mass loss had place
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Re: Transiting hot Uranus at GJ 3470

Post by Lazarus on 26th June 2012, 2:51 pm

Pity the assignment of this star as a member of the Hyades supercluster appears to be incorrect, would be interesting to have another cluster planet.
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Re: Transiting hot Uranus at GJ 3470

Post by Sunchaser on 27th June 2012, 10:01 pm

How would a hot Uranus differ from a hot Neptune? I know that sounds like a dumb question...would it appear different?

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Re: Transiting hot Uranus at GJ 3470

Post by tommi59 on 28th June 2012, 2:09 am

In appearance or density(composition) you ask?
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Re: Transiting hot Uranus at GJ 3470

Post by jyril on 28th June 2012, 3:22 am

Mass?

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Re: Transiting hot Uranus at GJ 3470

Post by Sunchaser on 28th June 2012, 7:00 am

Appearance. In the paper they have a density of approximately 1.07 g/cm3. Are they comparing it to Uranus because of the similar mass and density?

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Re: Transiting hot Uranus at GJ 3470

Post by Sirius_Alpha on 28th June 2012, 7:12 am

I'm almost sure it's just mass. A Neptune that is just under 1 MNeptune you might call a Uranus. Neptune has a mass of 17 ME, Uranus has a mass of 14 ME. GJ 3470 b's mass is clearly more similar to that of Uranus. That seems to be the only significant difference (temperature aside!). The planet's mass, radius and density are effectively indistinguishable from that of Uranus (the values for those of Uranus fall within the error margin of those of GJ 3470 b).

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Re: Transiting hot Uranus at GJ 3470

Post by Lazarus on 2nd July 2012, 5:06 pm

...and maybe because they are from countries which have languages other than English they aren't so concerned about that stupid joke.

I suspect that may be why we have the term sub-Neptunes rather than sub-Uranuses (and maybe the awkward plural).
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Re: Transiting hot Uranus at GJ 3470

Post by jyril on 3rd July 2012, 2:48 am

Or because Neptune is the more massive/dominant of the ice giants (cf. Jupiter vs. Saturn, Earth vs. Venus)?

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Re: Transiting hot Uranus at GJ 3470

Post by Lazarus on 29th January 2013, 2:00 am

Update: GJ 3470b is less dense than previously thought, may be an analogue for the Kepler-11 planets.

Spitzer Observations of GJ3470b: a Very Low-density Neptune-size Planet Orbiting a Metal-rich M dwarf
http://arxiv.org/abs/1301.6555
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Re: Transiting hot Uranus at GJ 3470

Post by tommi59 on 29th January 2013, 5:43 am

Even with larger radius due to assessing larger stellar radius planet R 4.83 is bigger than 4.5 for Kepler 11 e but 25% denser ,the same as k11 f despite almost twice larger R.It sseems to be that kepler 11 planets d,e,f,and maybe g are the least dense of all super earth - Neptune range excluding planets with significant mass loss.Examples kepler 20c,gj 1214b,kepler30b,corot 24 c
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Re: Transiting hot Uranus at GJ 3470

Post by Sirius_Alpha on 28th February 2013, 10:21 pm

An apparently cloudless atmosphere could make this planet an awesome transmission spectroscopy follow-up target.

Optical-to-Near-Infrared Simultaneous Observations for the Hot Uranus GJ3470b: A Hint for Cloud-free Atmosphere
http://arxiv.org/abs/1302.7257

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Re: Transiting hot Uranus at GJ 3470

Post by Led_Zep on 12th June 2013, 5:09 pm

http://beforeitsnews.com/space/2013/06/sunny-super-earth-2461246.html

A research team led by Akihiko Fukui (NAOJ), Norio Narita (NAOJ) and Kenji Kuroda (the University of Tokyo) observed the atmosphere of super-Earth “GJ3470b” in Cancer for the first time in the world using two telescopes at OAO (Okayama Astrophysical Observatory, NAOJ). This super-Earth is an exoplanet, having only about 14 times the mass of our home planet, and it is the second lightest one among already-surveyed exoplanets. The observational data revealed that this planet is highly likely to NOT be covered by thick clouds
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Re: Transiting hot Uranus at GJ 3470

Post by Sirius_Alpha on 1st September 2013, 8:21 pm

Warm Ice Giant GJ 3470b. I. A Flat Transmission Spectrum Indicates a Hazy, Low-methane, and/or Metal-rich Atmosphere
http://arxiv.org/abs/1308.6580

Thus, if the atmosphere is cloud-free its spectral features should be detectable with future observations. Transit observations at shorter wavelengths will provide the best opportunity to discriminate between plausible scenarios
And on arXiv tonight are observations just like that.

The blue sky of GJ3470b: the atmosphere of a low-mass planet unveiled by ground-based photometry
http://arxiv.org/abs/1308.6765

Simultaneous photometry in the ultraviolet (lambda_c = 357.5 nm) and optical infrared (lambda_c = 963.5 nm) allowed us to detect a significant change of the effective radius of GJ3470b as a function of wavelength. This can be interpreted as a signature of scattering processes occurring in the planetary atmosphere, which should be cloud-free and with a low mean molecular weight.

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Re: Transiting hot Uranus at GJ 3470

Post by zorro83 on 2nd September 2013, 5:54 am

other blue planet? Smile

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Re: Transiting hot Uranus at GJ 3470

Post by pochimax on 3rd September 2013, 3:25 am

So, it is not clear if the transmission spectrum is flat or not. Both papers seems to be not compatible, isn' t it? What a mess.
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Re: Transiting hot Uranus at GJ 3470

Post by Lazarus on 3rd September 2013, 1:55 pm

Well, making measurements of the atmospheres of planets orbiting stars many light years away is pretty difficult. Who would have guessed? Razz
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Re: Transiting hot Uranus at GJ 3470

Post by Shellface on 3rd September 2013, 4:33 pm

pochimax wrote:Both papers seems to be not compatible, isn't it?
Well… not really. The two papers observe different wavelengths of the emission spectrum, with Nascimbeni et al. observing shorter wavelengths than Crossfield et al. Because of that, Crossfield et al.'s data are consistent with a flat spectrum because they are observing part of it where the changes in transit depth are slight, whereas Nascimbeni et al. detect significant variation in transit depth as they observe part of the spectrum which shows considerably larger variation.

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Re: Transiting hot Uranus at GJ 3470

Post by Sirius_Alpha on 7th May 2014, 7:17 am

Near-infrared transmission spectrum of the warm-uranus GJ 3470b with the Wide Field Camera-3 on the Hubble Space Telescope
http://arxiv.org/abs/1405.1056

The atmospheric composition of low-mass exoplanets is the object of intense observational and theoretical investigations. GJ3470b is a warm uranus recently detected in transit across a bright late-type star. The transit of this planet has already been observed in several band passes from the ground and space, allowing observers to draw an intriguing yet incomplete transmission spectrum of the planet atmospheric limb. In particular, published data in the visible suggest the existence of a Rayleigh scattering slope, making GJ3470b a unique case among the known neptunes, while data obtained beyond 2 um are consistent with a flat infrared spectrum. The unexplored near-infrared spectral region between 1 and 2 um, is thus key to undertanding the atmospheric nature of GJ3470b. Here, we report on the first space-borne spectrum of GJ3470, obtained during one transit of the planet with WFC3 on board HST, operated in stare mode. The spectrum covers the 1.1--1.7-um region with a resolution of about 300. We retrieve the transmission spectrum of GJ3470b with a chromatic planet-to-star radius ratio precision of 0.15% (about one scale height) per 40-nm bins. At this precision, the spectrum appears featureless, in good agreement with ground-based and Spitzer infrared data at longer wavelengths, pointing to a flat transmission spectrum from 1 to 5 um. We present new simulations of transmission spectra for GJ3470b, which allow us to show that the HST/WFC3 observations rule out cloudless hydrogen-rich atmospheres (>10 sigma) as well as hydrogen-rich atmospheres with tholin haze (>5 sigma). Adding our near-infrared measurements to the full set of previously published data from 0.3 to 5 um, we find that a cloudy, hydrogen-rich atmosphere can explain the full transmission spectrum if, at the terminator, the clouds are located at low pressures (<1 mbar) or the water mixing ratio is extremely low (<1 ppm).

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Re: Transiting hot Uranus at GJ 3470

Post by Sirius_Alpha on 25th June 2014, 8:34 pm

Warm Ice Giant GJ 3470b. II Revised Planetary and Stellar Parameters from Optical to Near-infrared Transit Photometry
http://arxiv.org/abs/1406.6437

Looks like the data supports an H2-dominated atmosphere.

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Re: Transiting hot Uranus at GJ 3470

Post by tommi59 on 26th June 2014, 3:44 am

Big difference of planet radius 4.83 earth to 3.88?? Question 
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