For the first time astronomers were able to analyse the atmosphere of an exoplanet in the class known as super-Earths. Using data gathered with the NASA/ESA Hubble Space Telescope and new analysis techniques, the exoplanet 55 Cancri e is revealed to have a dry atmosphere without any indications of water vapour. The results, to be published in the Astrophysical Journal, indicate that the atmosphere consists mainly of hydrogen and helium.
The international team, led by scientists from University College London (UCL) in the UK, took observations of the nearby exoplanet 55 Cancri e, a super-Earth with a mass of eight Earth-masses. It is located in the planetary system of 55 Cancri, a star about 40 light-years from Earth.
Using observations made with the Wide Field Camera 3 (WFC3) on board the NASA/ESA Hubble Space Telescope, the scientists were able to analyse the atmosphere of this exoplanet. This makes it the first detection of gases in the atmosphere of a super-Earth. The results allowed the team to examine the atmosphere of 55 Cancri e in detail and revealed the presence of hydrogen and helium, but no water vapour. These results were only made possible by exploiting a newly-developed processing technique.
"This is a very exciting result because it's the first time that we have been able to find the spectral fingerprints that show the gases present in the atmosphere of a super-Earth," explains Angelos Tsiaras, a PhD student at UCL, who developed the analysis technique along with his colleagues Ingo Waldmann and Marco Rocchetto. "The observations of 55 Cancri e's atmosphere suggest that the planet has managed to cling on to a significant amount of hydrogen and helium from the nebula from which it originally formed."
Super-Earths like 55 Cancri e are thought to be the most common type of planet in our galaxy. They acquired the name 'super-Earth' because they have a mass larger than that of the Earth but are still much smaller than the gas giants in the Solar System. The WFC3 instrument on Hubble has already been used to probe the atmospheres of two other super-Earths, but no spectral features were found in those previous studies.
55 Cancri e, however, is an unusual super-Earth as it orbits very close to its parent star. A year on the exoplanet lasts for only 18 hours and temperatures on the surface are thought to reach around 2000 degrees Celsius. Because the exoplanet is orbiting its bright parent star at such a small distance, the team was able to use new analysis techniques to extract information about the planet, during its transits in front of the host star.
Observations were made by scanning the WFC3 very quickly across the star to create a number of spectra. By combining these observations and processing them through analytic software, the researchers were able to retrieve the spectrum of 55 Cancri e embedded in the light of its parent star.
Intriguingly, the data also contain hints of the presence of hydrogen cyanide, a marker for carbon-rich atmospheres.
"Such an amount of hydrogen cyanide would indicate an atmosphere with a very high ratio of carbon to oxygen," said Olivia Venot, KU Leuven, who developed an atmospheric chemical model of 55 Cancri e that supported the analysis of the observations.
"If the presence of hydrogen cyanide and other molecules is confirmed in a few years time by the next generation of infrared telescopes, it would support the theory that this planet is indeed carbon rich and a very exotic place," concludes Jonathan Tennyson, UCL. "Although hydrogen cyanide, or prussic acid, is highly poisonous, so it is perhaps not a planet I would like to live on!"
The results were summarized by Tsiaras et al. in the paper "Detection of an atmosphere around the super-Earth 55 Cancri e" which is going to be published in the Astrophysical Journal.
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Astronomers find first evidence of changing conditions on a super Earth
wduckss
Here, one should always take the effects the dual (binary) system. In these the conditions the only, is possible density of 5.9 + 1.5 -1.1 g cm -3. Planet (if the data is partially credible) is molten body (1,700 ° C small?) is not gaseous.
The ultimate is time to stop with comparision, guesswork and accept, the already published legality of the formation of the body.
It seems ridiculous assertion that the gaseous planet has a density of 6 g cm -3.
big_hairy_jimbo
If that is the case, then this planet is SO CLOSE to it's star, surely any Hydrogen and Helium would have "boiled" away??? The only explanation I have for it staying, is that the atmosphere of this planet is from the STAR itself!!! Perhaps the planet is constantly getting it's atmosphere renewed from the Star.
I also think they need a better name than Super Earth. As this planet CLEARLY is NOTHING like Earth. Mass should not indicate "EARTH" like. Uranus is 14.5 times the Mass of Earth, should we call Uranus a "Super Earth"????
http://nssdc.gsfc...tio.html
gculpex
I would agree that this planet is way too close to the star. At those speeds, it's probably well inside the corona.
Captain Stumpy
perhaps you are right... but they call it "Super earth" because it takes to long to say "a planetary mass that is larger than the Earth but still much smaller than the gas giants in our Solar System that is orbiting a parent star"...
it is an adequate (for now) colloquial term that conveys a readily accessible image that is relevant as well as semi-accurate (as i am sure a "gas giant" would instantly make a person think of Jupiter and the outer gas giants of our own system, right?)
vlaaing peerd
antialias_physorg
Not really:
55 Cancri e, Semimajor axis: 2.3bn km
55 Cancri A (the star it revolves around): Radius 210mn km (0.3 times solar radius)
Even if the corona is as strong as our sun which is said to extend 'millions of kilometers' into space
https://en.wikipe...i/Corona
there's still quite a gap between the corona and this star.
Yes, it is very close. A lot closer than e.g. Mercury is to the Sun. But the star is also quite a bit smaller than the sun.
Mark Thomas
The artist's impression drawing above is a little misleading because most the planet would be glowing like the inside of a blast furnace.
Torbjorn_Larsson_OM
So the observed atmosphere composition confirms the statistical mass-radius observation.
Torbjorn_Larsson_OM
The terms are used differently by different authors, due to history. Early on we didn't know where planets with smaller mass than Neptune would stop looking like Earth (rocky) and start looking like Neptune (gassy). It was during 2015 that enough observations had been made that people started to see the 1.5 Earth radii limit. (At 1.6 Earth radii there is a ~ 50 % likelihood for a planet to be gassy.)
The newer descriptions are not written in rocks either, you can certainly say sub.Neptunian, but FWIW you tend to see Mini Neptune used for planets between 2 and 4 (= Neptune) Earth radii. And I am going to call Janssen a mini-Neptune as well, now that we know it is a gassy planet.
Torbjorn_Larsson_OM
In other words, these planets bring their atmospheres, and it is first when the initial atmosphere has gone that you can expect some sort of gas balance between star and planet.
Mark Thomas
Generally speaking, the bigger a planet is, the thicker its atmosphere is more likely to be. Beyond 1.6 Earth radii they are more likely to be gassy. While we can try to determine the precise correlation between planet size and atmosphere, the actual predictibility based on radius alone is probably poor for ~Earth-sized planets. Earth itself has sufficient gravity for a far larger atmosphere. For example, Saturn's gravity is comparable to Earth's and the planet is a gas giant. Venus has less gravity and a much more dense atmosphere.
Someday we may be able to answer this question:
The atmospheric pressure on Earth is in what percentile of similar Earth radius planets (+/- 2%) in this galaxy?
AGreatWhopper
Because "little Uranus" isn't as interesting as "super Earth". Unless you're talking about damned wduckss.
Wrong. 8 times bigger than the earth, or 8 times smaller than Uranus. The phrase is pure pandering to the public. You can't create a good reason for it.
chileastro
LOL wducksss is definitely a little Uranus. There are several super Uranus' posting on here as well.
chileastro
Testicle planets?