Automobile emissions research benefits the study of exoplanet atmospheres

From the ROYAL ASTRONOMICAL SOCIETY and the “hot gases in a galaxy far, far, away” department

Chemical models developed to help limit the emission of pollutants by car engines are being used to study the atmospheres of hot exoplanets orbiting close to their stars. The results of a collaboration between French astronomers and applied combustion experts will be presented by Dr Oliva Venot and Dr Eric Hébrard at the European Week of Astronomy and Space Science (EWASS) 2018 in Liverpool.

Large planets similar to Neptune or Jupiter, orbiting 50 times closer to their star than the Earth does from the Sun, are thought to be composed of hydrogen-rich gas at temperatures between one and three thousand degrees Celsius, circulating at enormous speeds of nearly 10,000 kilometres per hour. With these extreme conditions, the interplay of various physical processes, such as vertical transport, circulation or irradiation, can drive the atmospheres of these hot exoplanets out of chemical equilibrium, resulting in deviations that are difficult to explain through standard astrophysical models and observations.

This is an artist’s impression showing a Jupiter-like transiting planet around a solar-like host star. CREDIT
ESO/L. Calçada

Venot, of the Laboratoire Interuniversitaire des Systèmes Atmosphériques, explains: “The philosophy of our team in solving problems is to search for and import well-tried methods from any other field whenever they exist. Back in 2012, we first noticed the overlap of temperature and pressure conditions between the atmospheres of hot Jupiters and car engines. Chemical networks developed for car engines are very robust as a result of years of intense R&D, laboratory studies and validation through comparison with numerous measurements performed under various conditions. The car models are valid for temperatures up to over 2,000 degrees Celsius and a wide range of pressures, so are relevant to the study of a large diversity of warm and hot exoplanet atmospheres.”

The project grew out of an initial collaboration between the Laboratoire d’Astrophysique de Bordeaux and the Laboratoire Réactions et Génie des Procédés in Nancy. Over the past six years, the team has developed models of the chemical composition of hot Jupiter and warm Neptune atmospheres based on one or several networks of chemical reactions. These chemical networks have been made available through an open access database and are now widely used and recognised in the international astrophysics community.

“It is an important part of our team’s philosophy to make input data and tools available to the community,” says Hébrard, of the University of Exeter.

In addition to car testing, the team has also drawn on the expertise of researchers working on particle accelerators. Data on the ability of molecules to absorb ultraviolet light have, to date, been available mainly at room temperature. Experiments at synchrotron facilities at the Laboratoire Interuniversitaire des Systèmes Atmosphériques will enable measurements to be made at temperatures relevant for exoplanet atmospheres.

“Other fields of research have an important role to play in the characterisation of the fantastic diversity of worlds in the Universe and in our understanding of their physical and chemical nature,” says Venot.



21 thoughts on “Automobile emissions research benefits the study of exoplanet atmospheres

  1. If you look at the EWASS2018 programme on their website there’s a presentation by a UK Met Office employee on dealing with Earth’s clouds in climate models. The short summary admits they don’t have a clue including whether the sign for warming/cooling is positive or negative. So they’re still admitting to each other that they have no no clue while telling us the science is settled.

    I tried to download the abstract but the site is incredibly un-user friendly. Some others here may have more luck if they try.

    • Scute:

      I suggest the reason why they do not have a clue is that they are not engineers; so have little knowledge on the Rankine Cycle. Hence rely on primarily radiation factors to provide explanation.

      In simple terms this Cycle moves very large amounts of energy up through the atmosphere irrespective of the radiation process and the effect of GHGs. Without taking this into account it is small wonder that they haven’t a clue.

      Energy or Enthalpy manifests itself in many forms as we engineers are well aware. They should take note of that.

  2. The spectral output of the host star will be critical as the EUV/UV photochemistry of the upper layers will dictate what molecules can be present.

  3. I haven’t heard of any solar systems that have two hot Jupiters. Maybe if you get a hot Jupiter that means it has cleared out its solar system as it moved closer to its sun and the hot Jupiter is the only significant planet left after all this activity.

    In our solar system, Saturn supposedly pulled Jupiter back into the outer solar system when Jupiter started moving closer to the Sun in the solar system’s early history. Hot Jupiter solar systems may not have had a Saturn timely enough or near enough.

    • The orbital resonances of the planets must have been established early as it has kept their pacing (orbital period) constant (Venus-Earth/Moon barycenter, Jupiter-Saturn, Uranus-Neptune). And Orbital period determines distance from the sun.

      Part of the Rare Earth Hypothesis.

      • Yes, the Rare Earth Hypothesis is indeed interesting. Not just the Earth, but our particular solar system (including the characteristics of our particular sun).

      • Interesting that the “Rare Earth Hypothesis” has as a major tenant that key members of our solar system should have maintained their present orbital configurations for approximately 4 billion years in order for earth to provide a stable environment for life to develop and evolve. As the hypothesis’ title acknowledges, this would be a rare occurrence.
        A key element in the “Rare Earth Hypothesis” is the presence of our unusually large moon for over 4 billion years.
        Beautiful hypothesis. Ugly fact: calculating the lunar recession rate back in time gives the Earth-Moon system a maximum age of barely 1 billion years.


  4. I can’t figure out what “50 times closer to their star than the Earth does from the Sun” means.
    Is this 1/50th of the distance from Earth to our Sun? It seems like it should be, but it’s not clear that it is.
    Why don’t they just use Astronomical Units (AU) as a distance measure?

    • I too thought that was an awkward way to put the distance. If your interpretation is correct, that puts it at just a bit less than 2 million miles from their star. In contrast, Mercury is about 36 million miles from the sun and travels about 50 km/hour, quite a bit less than 10,000 km/hour! Can you imagine what this planet’s mass would do to the surface of the star, and vice versa? Seems like you’d have one continuous solar flare or CME.

      • I have seen exactly that on “how the Universe Works.” They show a plume of material being sucked from the plant to the star and then said in a few million years, the whole planet will end up being absorbed into the star.

  5. In the long list of interesting things we should be studying about these hot giant planets, apparently skimming the surface of their parent star, their similarity to the hot processes going on in closed system internal combustion engines comes a long way down my list of priorities. Perhaps even what prevents their atmosphere being sucked into the star in fairly short order? Or even how good would your sunburn factor cream have to be to visit. Or why at those temperatures and proximity doesn’t your hydrogen atmosphere ignite anyway?
    But I don’t doubt that evil carbon is at work somewhere.

    • Hydrogen atmosphere will not combust without oxygen but it’s hotter than propane torch. At 1/50 AU from sun-like star, the irradiance is 3.4 MW/m^2 and equilibrium temperature is around 2800 K!

      • Hydrogen atmosphere will not combust without presence of oxygen, or berillium, or boron, or carbon, or nitrogen, or fluorine,… well actually hydrogen is very reactive and will combust with nearly all elements.

        But pure hydrogen would indeed have nothing with which to combust.


    • I saw a tv program the other day where they think they have found a hot Jupiter with all its atmosphere blown away, leaving just a solid core.

  6. Isn’t it interesting to learn that astrophysicists are quite happy to learn from experiences in other branches of the exact sciences. This in contrast with climatologists who, when, for instance, dealing with sun-earth interactions, large pooh-poo the expertise of solar physicists an space scientists. Just a thought.

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