As part of the PlanetS National Centre of Competence in Research (NCCR), astronomers from the Universities of Geneva (UNIGE) and Bern, Switzerland, have come to measure the temperature of the atmosphere of an exoplanet with unequalled precision, by crossing two approaches. The first approach is based on the HARPS spectrometer and the second consists of a new way of interpreting sodium lines. From these two additional analyses, researchers have been able to conclude that the HD189733b exoplanet is showing infernal atmospheric conditions: wind speeds of more than 1000 kilometres per hour, and the temperature being 3000 degrees. These results open up perspectives to approach the study of exoplanet atmospheres. They were published in two journals, namely Astronomy & Astrophysics and Astrophysical Journal Letters.
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With a temperature of 3000 degrees and such winds blowing at several thousand kilometres per hour, the HD189733b exoplanet's atmosphere is truly turbulent. Measurements taken by a team of astronomers from the Universities of Geneva and Bern are given in the framework of the PlanetS NCCR; the figures come from observations made over sodium spectral lines. This element is contained in the exoplanet's atmosphere, and has been measured by the HARPS spectrometer, an instrument designed at the UNIGE Observatory, and installed on a telescope of the European Star Observatory (ESO) in Chile.
Following the sodium lines
When there is an atmosphere, sodium is the source of a clearly recognisable signal, whose intensity varies at the time when the planet passes before its star, an event called transit. This effect had been predicted in 2000, and highlighted two years later through Hubble space telescope observations. But, it had only been able to be detected since then from Earth, from giant telescopes, 8 to 10 metres in diameter.
At UNIGE, astronomers have had the idea of using observations already made by the HARPS spectrometer, to study sodium lines. By attentively scrutinising the data collected over many years, Aurélien Wyttenbach, a researcher at the UNIGE Faculty of Science, has been able to detect variations in sodium lines during several transits of HD189733b. Surprisingly, the analysis of HARPS data on Earth produces an equivalent detection, in terms of sensitivity, to that of the Hubble space telescope, but much better in terms of spectral resolution. It is this last aspect which has enabled an analysis to be achieved, which is a lot finer than previously, and this despite a telescope whose diameter remains modest. Alongside this, and in another study, Professor Kevin Heng, at Bern University, has developed a new technique of interpreting variations in sodium lines. Instead of using a sophisticated computer model, he resorts to a set of simple formulae, which enable variations in temperature, density and pressure to be expressed within an atmosphere
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It's only 3 million miles from the star and orbits in a tad over 2 days. Yeah, that makes Venus look like a tropical paradise. I'm surprised a planet can even form that close to a star in the first place. I wonder if maybe it formed in the outer solar system and migrated inward...
I doubt there would be much 'exploring' of such an actively hostile environment... You would have to consider virtually any probe you send there to be disposable, and would only be able to get a limited amount of information. Forget ever landing there unless you can develop magic forcefields.
Well the planet's atmosphere is so huge, a probe would have to orbit far out to avoid drag...and even then at that close to the star you'd need pretty heavy shielding.
Looks like the place has proven a mere 1000 F hotter but then winds rather slower then were being calculated back in 2013.
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Now that I think about it, I suppose you could build probes like you'd build something to resist a direct nuclear blast. You wouldn't be able to do much with them due to the thicknesses of material required, but I'm having the mental image of a concrete bunker with a camcorder stuck to the window being dropped through the atmosphere...
If we can make a window survive we can put a laser in that window and engage in chemical spectroscopy! Up link everything in real time to an orbiter. One of those aluminum transparent ceramics could probably already make a viable window for a short period of operation.
"This cult of special forces is as sensible as to form a Royal Corps of Tree Climbers and say that no soldier who does not wear its green hat with a bunch of oak leaves stuck in it should be expected to climb a tree"
— Field Marshal William Slim 1956
Melting point of most aluminum oxides is around 2,000 - better video fast!
A life is like a garden. Perfect moments can be had, but not preserved, except in memory.Leonard Nimoy.
Now I did a job. I got nothing but trouble since I did it, not to mention more than a few unkind words as regard to my character so let me make this abundantly clear. I do the job. And then I get paid.- Malcolm Reynolds, Captain of Serenity, which sums up my feelings regarding the lawsuit discussed here.
If a free society cannot help the many who are poor, it cannot save the few who are rich. - John F. Kennedy
Pure fused silica has a melting point of 2000 degrees (that's Celsius, not that Nancy-boy Fahrenheit), excellent resistance to thermal shock, extremely low thermal expansion, excellent clarity and is inert to most chemicals, including virtually all acids (except hydrofluoric, because hydrofluoric is a prick).
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Borgholio wrote:It's only 3 million miles from the star and orbits in a tad over 2 days. Yeah, that makes Venus look like a tropical paradise. I'm surprised a planet can even form that close to a star in the first place. I wonder if maybe it formed in the outer solar system and migrated inward...
Planets' orbits are a lot more flexible than you'd expect, especially fairly early on while they're still being formed. There's fairly convincing evidence that the gas giant planets, Jupiter, Saturn, Uranus and Neptune, weren't always in that order from the sun. Even nowadays, with a mature set of planets like ours, their orbits are only short-term stable — it's impossible to predict exact orbits more than a few million years into the future.
Incidentally, this is also how we get all the "Hot Jupiters" that have been discovered, gas giants form fairly far out (there's a "frost line" about where the main asteroid belt is now, beyond which various ices in the early solar system could stay solid) then migrate inwards.
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There's fairly convincing evidence that the gas giant planets, Jupiter, Saturn, Uranus and Neptune, weren't always in that order from the sun.
Yes the idea is that they all formed closer to the sun than they did now, and that an orbital resonance between Jupiter and Saturn pushed all the planets outward to where they are now. The theory is that large planets such as Uranus and Neptune could not grow as big as they did without being closer to the sun where there was more material and more energy. Even more interesting is that Neptune may have formed closer to the sun than Uranus...and they swapped places during the move!
Incidentally, this is also how we get all the "Hot Jupiters" that have been discovered, gas giants form fairly far out (there's a "frost line" about where the main asteroid belt is now, beyond which various ices in the early solar system could stay solid) then migrate inwards.
Yeah that's what I meant about migrating...it doesn't seem possible for an icy gas giant to form only 3 million miles from a star. There's a reason why we don't have any gas giants in our own solar system until you get out past the orbit of Mars.
Broomstick wrote:Melting point of most aluminum oxides is around 2,000 - better video fast!
I had in mind active cooling, the ceramic merely makes cooling plausibly effective. Such as blowing a sheet of bottled argon between two layers of it. Even if the craft were indestructable radio or laser data transmissions will rapidly become impossible as it falls down into such a dense atmosphere so we simply don't need the material to last past a plausible coolant supply time frame. Also depending on the entry speed the probe might get way stupider hotter then 3000 F. But we can deal with that for short periods. Keep in mind we only need maybe a dime sized window for the laser sensor. Not a huge area to cool.
The transparent ceramics are really valuable for this sort of extreme situation because while sure, none have the raw heat resistance to work unaided, the resistance to physical and chemical abrasion is colossal compared to glass (so the solid matter in the air wont simply etch away the polished surface instantly at such high velocity) and the gap only becomes greater as impact velocity rises. The ceramics also have much less thermal expansion and higher insulation value then glass which is really handy if you have to maintain a sealed probe against sudden 3000degree heat flux. Thermal expansion makes many materials unsuitable for super high temperature use even though they can maintain strength under heating.
Synthetic Sapphire is so good at this its now used to make small windows into artillery firing chambers, allowing them to use lasers for igniting the propellent. They dont have protective shields or anything, just straight up takes the heat and pressure. Which is not 3000 C, but it is really hot, and involves ~60,000psi levels of dynamic pressure.
"This cult of special forces is as sensible as to form a Royal Corps of Tree Climbers and say that no soldier who does not wear its green hat with a bunch of oak leaves stuck in it should be expected to climb a tree"
— Field Marshal William Slim 1956
And... sapphire (natural or artificial) is a form of aluminum oxide....
Glad to hear it's workable for such a system, at least for a short time frame.
A life is like a garden. Perfect moments can be had, but not preserved, except in memory.Leonard Nimoy.
Now I did a job. I got nothing but trouble since I did it, not to mention more than a few unkind words as regard to my character so let me make this abundantly clear. I do the job. And then I get paid.- Malcolm Reynolds, Captain of Serenity, which sums up my feelings regarding the lawsuit discussed here.
If a free society cannot help the many who are poor, it cannot save the few who are rich. - John F. Kennedy
