≡ Menu

Twinkle: Studying Exoplanet Atmospheres

A small satellite designed to study and characterize exoplanet atmospheres is being developed by University College London (UCL) and Surrey Satellite Technology Ltd (SSTL) in the UK. Given the engaging name Twinkle, the satellite is to be launched within four years into a polar low-Earth orbit for three years of observations, with the potential for an extended mission of another five years. SSTL, based in Guildford, Surrey and an experienced hand in satellite development, is to build the spacecraft, with scientific instrumentation in the hands of UCL.

The method here is transmission spectroscopy, which can be employed when planets transit in front of their star as seen from Earth. Starlight passing through the atmosphere of the transiting world as it moves in front of and then behind the star offers a spectrum that can carry the signatures of the various molecules there, a method that has been used on a variety of worlds like the Neptune-class HAT-P-11b and the hot Jupiter HD 189733b. The goal of the Twinkle mission is to analyze at least 100 planets ranging from super-Earths to hot Jupiters, producing temperatures and even cloud maps.

Hot Neptune

Image: This artist’s impression depicts a Neptune-class world grazing the limb of its star as seen from our vantage point. Analyzing starlight as transiting worlds pass in front of and then behind their star can tell us much about the constituents of the planet’s atmosphere. Credit: NASA/JPL-Caltech.

Giovanna Tinetti (UCL), lead scientist for the mission, describes it as the first mission dedicated to analyzing exoplanet atmospheres, adding that understanding the chemical composition of an atmosphere serves as a key to the planet’s background. Distance from the parent star, notes this UCL news release, affects the chemistry and physical processes driving an atmosphere, and the atmospheres of small, terrestrial-class worlds, like that of our own Earth, can evolve substantially from their initial state through impacts with other bodies, loss of light molecules, volcanic activity or the effect of life. The atmosphere, then, can help us trace a planet’s history as we learn whether it was born in its current orbit or migrated from another part of the system..

I should mention that Tinetti was deeply involved in the discovery of water and methane in the atmosphere of HD 189733b. From Tinetti’s website at University College London:

A key observable for planets is the chemical composition and state of their atmosphere. Knowing what atmospheres are made of is essential to clarify, for instance, whether a planet was born in the orbit it is observed in or whether it has migrated a long way; it is also critical to understand the role of stellar radiation on escape processes, chemical evolution and climate. The atmospheric composition is the only indicator able to discriminate an habitable/inhabited planet from a sterile one.

Twinkle was presented several days ago at an open meeting of the Royal Astronomical Society. Interestingly, the mission is being developed with a mixture of private and public sources, at a total cost of about £50 million, including launch. That number seems strikingly low to me, with mission designers claiming that Twinkle is a factor of ten times cheaper to build and operate than other spacecraft developed through international space agency programs. The low cost is being attributed to the use of off-the-shelf components and growing expertise in small mission development. These numbers will be worth remembering if Twinkle performs as expected.


Comments on this entry are closed.

  • Alex Tolley February 10, 2015, 15:11

    They could definitely do with a better website. I’m n0ot clear what “small” means in this context, but here is the image of the satellite:

    If they can do all this for £50 million ($75m) that is very impressive and reinforces a theme we have noted that miniaturization and standardized components is going to drive down costs of these instruments and missions. It would be interesting to know how much of the cost is launch and what a 10x reduction would offer in terms of mission cost.

  • Ashley Baldwin February 10, 2015, 16:15

    Thanks Paul . Desperately needed although a bigger mission would be better . The medium Explorer mission announcement of opportunity is out next year and is upped to near $300 million and a lot of U.S astronomers , and me , hope to use this to bid for a mission of this type . There have been a couple of ground breaking papers released on M dwarfs this week that favour transition photometry ,spectroscopy and life. Houdebine et al and Leconte et Al . I would strongly recommend them to readers as two very readable and exciting papers. The Exo-PAG SIG group is meeting today to hammer out the exoplanet strategy for the 2020 Decadel and will cover missions like this which are desperately needed and can achieve a lot for a low price.

  • Ashley Baldwin February 10, 2015, 16:16

    Twinkle has an aperture of 48cm by the way. That’s what $70 million dollars gets you .

  • Joy February 10, 2015, 18:21

    Great little mission. On the basis of the ongoing brilliance from astronomers, I confidently predict that convincing life signatures will be detected from the spectra of an extrasolar planet long before there is a clear result from solar system astrobiology. Seriously, which is easier, building telescopes with spectrometers or landing a drilling rig/biology lab on Europa?

  • Andrew Palfreyman February 10, 2015, 19:50

    “There have been a couple of ground breaking papers released on M dwarfs this week”
    Links please?

  • Paul Gilster February 10, 2015, 21:52

    We’ll be talking about one of these tomorrow.

  • ljk February 11, 2015, 9:52

    Planets orbiting red dwarfs may stay wet enough for life

    Feb 09, 2015 by Charles Q. Choi, Astrobiology Magazine


    And a Titan submarine plan thrown in for good measure:


  • ljk February 11, 2015, 9:55

    Alex Tolley, did you mean this Web site:


    And this page in particular:


    Small satellites, small blog? ;^)

  • John Fairweather February 12, 2015, 16:27

    Interesting project, hope it succeeds. It will be interesting to read the design papers.

    (Past British ideas have been – original design of the Apollo moon landers and the concept of the Daedalus Starship, not to mention Beagle 2.)

  • ljk February 20, 2015, 18:19

    Jupiter, as Aliens Might See It

    A view of the gas giant as if it were an exoplanet cross-checks methods for studying worlds outside our solar system

    February 17, 2015 |By Elizabeth Gibney and Nature magazine

    Astronomers have observed Jupiter for centuries. But a study that looks at the gas giant as if it were an exoplanet could help to make more reliable interpretations of the atmospheres of bodies orbiting stars hundreds of light years away. The results largely confirm the conventional picture of Jupiter, but also reveal some surprises—including clouds of ice crystals previously unheard of on the planet.

    The hundreds of planets now known to orbit stars other than our own are almost never directly visible in telescopes. In a handful of cases, however, astronomers have been able to learn about their make-ups, by interpreting how starlight filters through their atmospheres as it skirts the planets while they cross between their parent stars and Earth.

    But low resolution and experimental noise mean that such results, which are usually only possible for large planets orbiting bright stars, are often disputed. “The models give us answers, but we don’t always know if we can believe those answers or not,” says Tyler Robinson, an astronomer at NASA’s Ames Research Center near Mountain View, California.

    Now astrophysicist Pilar Montañés-Rodríguez at the Astrophysics Institute of the Canary Islands in Tenerife and her colleagues have devised a way to apply the idea to studying Jupiter. The technique used for exoplanet atmospheres does not immediately translate to Jupiter, because its orbit never takes it between Earth and the Sun. So, instead of looking directly at sunlight filtered through Jupiter’s atmosphere, the team analysed light reflected back from the Jovian moon Ganymede when Jupiter passed between it and the Sun—in other words, when the planet partially eclipsed the Sun as seen from Ganymede.

    Full article here: