The atmosphere of GJ 1214 b

New transits curve available on arxiv,possible another planet in the system feasible to detect even within hz

tommi59 wrote:

...on arxiv...

So why no link?

sorry open in pdf http://arxiv.org/abs/1207.3064

Measuring the various wavelengths at the same time to get around the stellar variability.

IRSF SIRIUS JHKs Simultaneous Transit Photometry of GJ1214b
Norio Narita, Takahiro Nagayama, Takuya Suenaga, Akihiko Fukui, Masahiro Ikoma, Yasushi Nakajima, Shogo Nishiyama, Motohide Tamura
http://arxiv.org/abs/1210.3169

Spitzer Transits of the Super-Earth GJ1214b and Implications for Its Atmosphere
http://arxiv.org/abs/1301.6763

Quote :

We observed the transiting super-Earth exoplanet GJ1214b using Warm Spitzer at 4.5 microns wavelength during a 20-day quasi-continuous sequence in May 2011. The goals of our long observation were to accurately define the infrared transit radius of this nearby super-Earth, to search for the secondary eclipse, and to search for other transiting planets in the habitable zone of GJ1214. We here report results from the transit monitoring of GJ1214b, including a re-analysis of previous transit observations by Desert et al. (2011). In total, we analyse 14 transits of GJ1214b at 4.5 microns, 3 transits at 3.6 microns, and 7 new ground-based transits in the I+z band. Our new Spitzer data by themselves eliminate cloudless solar composition atmospheres for GJ1214b, and methane-rich models from Howe & Burrows (2012). Using our new Spitzer measurements to anchor the observed transit radii of GJ1214b at long wavelengths, and adding new measurements in I+z, we evaluate models from Benneke & Seager (2012) and Howe & Burrows (2012) using a chi-squared analysis. We find that the best-fit model exhibits an increase in transit radius at short wavelengths due to Rayleigh scattering. Pure water atmospheres are also possible. However, a flat line (no atmosphere detected) remains among the best of the statistically acceptable models, and better than pure water atmospheres. We explore the effect of systematic differences among results from different observational groups, and we find that the Howe & Burrows (2012) tholin-haze model remains the best fit, even when systematic differences among observers are considered.

Optical Observations of the Transiting Exoplanet GJ 1214b
http://arxiv.org/abs/1302.3644

From the conclusion:

Quote :

We have recorded the first V-band observations of GJ 1214b (centered at 0.55 µm). These data point to a lower absorption more consistent with an H₂O-rich atmosphere or a mixture of H₂ and water; that is, an intermediate atmospheric structure. Such an atmosphere might be expected because any H₂O-rich atmosphere would necessarily produce hydrogen through photochemistry. We measure an R-band radius that is also consistent with either a H₂ or an intermediate water and H₂-based atmosphere. Taken together, our observations can be best interpreted with an atmosphere that is partly H₂ and partly water based. However, additional observations are needed from ground-based and space-based platforms to establish the optical continuum of GJ 1214b.

Quantitatively Assessing the Role of Clouds in the Transmission Spectrum of GJ 1214b
http://arxiv.org/abs/1305.4124

Clouds of ZnS and KCl high in the atmosphere may explain the transmission spectrum provided the sedimentation efficiency is low. Hydrocarbon hazes are another possibility.

http://arxiv.org/abs/1305.5544

Search for Rayleigh scattering in the atmosphere of GJ1214b

And more...

Multi-Color Transit Photometry of GJ 1214b through BJHKs-Bands and a Long-Term Monitoring of the Stellar Variability of GJ 1214
http://arxiv.org/abs/1305.6985

Certainly this planet is holding on to its secrets quite effectively.

Lazarus wrote:

Certainly this planet is holding on to its secrets quite effectively.

This planet show us the limitations of our current instruments. We need better ones and more time in current ones.

I recently read a paper (of which I unfortunately forgot to record the name or address) that speculated that GJ 1214b might be a carbon planet. The primary is known to have an unusually high C/O ratio, so a carbon planet would not be unexpected, and models of carbon planets indicate a similar mass as what is observed, for a solid planet of its diameter (since they are expected to be significantly less dense than oxygen-dominated planets).

So they suggested that we are looking at a carbon planet with an optically thin atmosphere, explaining the flat transmission spectrum.

How to Distinguish between Cloudy Mini-Neptunes and Water/Volatile-Dominated Super-Earths
http://arxiv.org/abs/1306.6325

While GJ 1214b is currently the best target for making this distinction, the cases of GJ 436b, 55 Cnc e and HD 97658b are also considered.

Quote :

In a numerical retrieval study, we show for GJ 1214b that an unambiguous distinction between a cloudy H2-dominated atmosphere and cloud-free H2 atmosphere will be possible if the uncertainties in the spectral transit depth measurements can be reduced by a factor of ~3 compared to the published HST WFC3 and VLT transit observations. We argue that the required precision for the distinction may be achievable with currently available instrumentation by stacking 10-15 transit observations.

More data...

Narrow-K-Band Observations of the GJ 1214 System
http://arxiv.org/abs/1308.4404

Quote :

While we find no evidence for deviation from a flat spectrum (slope s = 0.0016+/-0.0038), an H_2 dominated upper atmosphere (< 60 mbar) cannot be excluded. More precise observations at < 0.7 micron and in the K-band as well as a uniform analysis of all published data would be useful for establishing more robust limits on atmosphere models for GJ 1214b.

Blue Light Observations Indicate Water-Rich Atmosphere of a Super-Earth
Narita, N, et al.

The absence of strong Rayleigh scattering in shorter wavelengths argues against a cloudless, H-dominated model for the planetary atmosphere.

Link didn't work for me. This one does: http://www.nao.ac.jp/en/news/science/2013/20130904-subaru.html

Usefully, they also include the link to the paper associated with the press release (why isn't this done more often?) - this is one of the ones linked upthread.

NASA announced the same some time ago. The article appeared in arxiv in may, and it clearly says that an atmosphere of H2 with a lot of high clouds could be possible. So i do not understand this "no new" and maybe inaccurate press release.

Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b
http://www.nature.com/nature/journal/v505/n7481/full/nature12888.html

Cloudy skies on nearby super-Earth
http://www.nature.com/news/cloudy-skies-on-nearby-super-earth-1.14450

Ah ha, nice to see that the cloud possibility survives. This does make characterising the bulk composition of the atmosphere that much more difficult though.

Now on arXiv:

Kreidberg et al. "Clouds in the atmosphere of the super-Earth exoplanet GJ 1214b"
http://arxiv.org/abs/1401.0022

Laura Kreidberg is speaking about the last results :
https://www.youtube.com/watch?v=8x2DcgZiKTA&feature=youtu.be

The atmospheric circulation of the super Earth GJ 1214b: Dependence on composition and metallicity

We present three-dimensional atmospheric circulation models of GJ 1214b, a 2.7 Earth-radius, 6.5 Earth-mass super Earth detected by the MEarth survey. Here we explore the planet's circulation as a function of atmospheric metallicity and atmospheric composition, modeling atmospheres with a low mean-molecular weight (i.e., H2-dominated) and a high mean-molecular weight (i.e. water- and CO2-dominated). We find that atmospheres with a low mean-molecular weight have strong day-night temperature variations at pressures above the infrared photosphere that lead to equatorial superrotation. For these atmospheres, the enhancement of atmospheric opacities with increasing metallicity lead to shallower atmospheric heating, larger day-night temperature variations and hence stronger superrotation. In comparison, atmospheres with a high mean-molecular weight have larger day-night and equator-to-pole temperature variations than low mean-molecular weight atmospheres, but differences in opacity structure and energy budget lead to differences in jet structure. The circulation of a water-dominated atmosphere is dominated by equatorial superrotation, while the circulation of a CO2-dominated atmosphere is instead dominated by high-latitude jets. By comparing emergent flux spectra and lightcurves for 50x solar and water-dominated compositions, we show that observations in emission can break the degeneracy in determining the atmospheric composition of GJ 1214b. The variation in opacity with wavelength for the water-dominated atmosphere leads to large phase variations within water bands and small phase variations outside of water bands. The 50x solar atmosphere, however, yields small variations within water bands and large phase variations at other characteristic wavelengths. These observations would be much less sensitive to clouds, condensates, and hazes than transit observations.

X-ray emission from the super-Earth host GJ 1214
http://arxiv.org/abs/1407.2741

Quote :

Stellar activity can produce large amounts of high-energy radiation, which is absorbed by the planetary atmosphere leading to irradiation-driven mass-loss. We present the detection and an investigation of high-energy emission in a transiting super-Earth host system, GJ 1214, based on an XMM-Newton observation. We derive an X-ray luminosity LX=7.4E25 erg/s and a corresponding activity level of log(LX/Lbol)~ -5.3. Further, we determine a coronal temperature of about -3.5 MK, which is typical for coronal emission of moderately active low-mass stars. We estimate that GJ 1214 b evaporates at a rate of 1.3E10 g/s and has lost a total of ~2-5.6 MEarth.

With an original mass near the Neptune-regime, I would expect a H-dominated atmosphere.

Mallonn et al. "GJ1214: Rotation period, starspots, and uncertainty on the optical slope of the transmission spectrum"
https://arxiv.org/abs/1803.05677

Figuring out the transmission spectrum gets complicated because of the activity of the star. Previous inferences about the atmosphere might be influenced by spot occultations.

https://www.nasa.gov/feature/jpl/nasa-s-webb-takes-closest-look-yet-at-mysterious-planet

NASA’s James Webb Space Telescope has observed a distant planet outside our solar system – and unlike anything in it – to reveal what is likely a highly reflective world with a steamy atmosphere. It’s the closest look yet at the mysterious world, a “mini-Neptune” that was largely impenetrable to previous observations.

And while the planet, called GJ 1214 b, is too hot to harbor liquid-water oceans, water in vaporized form still could be a major part of its atmosphere.

(...)

“The ability to get a full orbit was really critical to understand how the planet distributes heat from the day side to the night side,” Kempton said. “There’s a lot of contrast between day and night. The night side is colder than the day side.” In fact, the temperatures shifted from 535 to 326 degrees Fahrenheit (from 279 to 165 degrees Celsius).

Such a big shift is only possible in an atmosphere made up of heavier molecules, such as water or methane, which appear similar when observed by MIRI. That means the atmosphere of GJ 1214 b is not composed mainly of lighter hydrogen molecules, Kempton said, which is a potentially important clue to the planet’s history and formation – and perhaps its watery start.

“This is not a primordial atmosphere,” she said. “It does not reflect the composition of the host star it formed around. Instead, it either lost a lot of hydrogen, if it started with a hydrogen-rich atmosphere, or it was formed from heavier elements to begin with – more icy, water-rich material.”