The Next 10 Years of Exoplanets

By Julianne Dalcanton | August 19, 2010 11:51 am

The recent US Decadal Survey (Astro2010) contains a conundrum.

As part of the report, the Decadal Survey committee identified three key “scientific objectives” on which they felt the community should focus. These were:

  1. “Cosmic Dawn: Searching for the First Stars, Galaxies, and Black Holes”
  2. “New Worlds: Seeking Nearby, Habitable Planets”
  3. “Physics of the Universe: Understanding Scientific Principles

(For the record, I think this is a completely reasonable list, filled with the kinds of things that make splashy magazine covers. It’s arguably tilted a bit far from more traditional but critically important aspects of astronomy — for example, we don’t actually know how stars form, or how they explode, and yet the only bit of stellar physics that’s covered under this list is the fossil record of the absolute lowest metallicity stars. However, the committee had to narrow things down, and these are certainly the most “sellable” aspects of our field, as far as congressional committees and the general public is concerned.)

Now, these key questions are supposed to be partial guides to the project prioritization that the committee carried out. And yet, when you look at the list of recommended space- and ground-based investments, there really is precious little that is deeply connected to #2. As many have commented here and elsewhere, where is the investment in exoplanets?

While I agree it appears to be a glaring conflict, I think it’s actually completely sensible. The search for extrasolar planets is by far the hottest new area of astronomy. However, because it’s so new, the scientific landscape is wide open and barely explored. Is the most interesting question the mass function and radial distribution of planets? Are the subset of habitable planets the most compelling targets? Is the study of atmospheres and exoplanet weather the big breakthrough issue? What about the theory of stability of planetary systems? Do we know the physics controlling how all these planetary systems form? Every single one of these questions is awesome, but it would be nuts to take bets now on a billion dollar flagship facility dedicated to just one of these topics.

I’m guessing that what the committee did was essentially try to earmark some of the explorer-class space and ground missions for exoplanets. They made exoplanets an unambiguous scientific priority, and then they did their best to protect pots of money for faster timescale moderate-sized experiments (2nd ranked for both ground and space). Thus, when an exoplanet mission is proposed for an Explorer satellite, they get the huge boost of saying that their satellite will help answer one of the key questions from the Decadal Survey. (Edit: They also called out for investment in “New Worlds Technology” (i.e., things like a steerable sunshade) that would reduce the price of a mission to study habitable planets in the future, putting an exoplanet-optimized flagship mission at a fundable price point in time for the next decadal survey.) This strategy is smart — we’ve got Kepler up right now, JWST in the nearish future, and on-going ground-based work across the world. The field is evolving so rapidly, that it’s almost certainly better that the experimental response be kept as nimble as possible. So, reading the tea leaves, I think exoplanets did just fine in this report.

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  • Brian Siana

    I would argue that something very similar happened with “Cosmic Dawn” science. The final highly ranked programs will do little to study the “cosmic dawn”. And GSMT was actually demoted below LSST even though it is well suited for studying the first galaxies (and it was actually ranked higher by the Optical-IR committee).

  • Julianne

    With the “Cosmic Dawn” science, JWST should make a lot of progress, even without GSMT. NIR spectroscopy is what you want for most of the high-z stuff, and it’s just not competitive from the ground (as the WFC3/IR grism is demonstrating).

  • Pepper

    Excellent point on exoplanets. Right now the field is too immature to support a flagship mission in the next decade. We need to wait for the results of JWST, Kepler, improved RV instrumentation, and hopefully TESS. Only then will we have an idea of the overall planet demographics and know which are the optimal kinds of targets. By 2020 we will be ready for a TPF-size mission.

    For now, the priority should be to improve the RV precision of ground-based spectrographs, and to build more so that HARPS, Keck, and Coralie are not the only ones that can get the highest-precision measurements. That’s a perfect slot for the 2nd priority program for the ground-based section of the report. On the space side, TESS is the most important exoplanet priority, and should definitely be the next Explorer mission chosen.

  • spyder

    One thought on all of the posts regarding the Decadal Report: Where is all the private venture capital? The overt reliance on government funding for so much space science ignores the powerful contributions of those who traveled the frontiers before. The small group of researchers who founded JPL, also founded several other private companies to continue the efforts. Howard Hughes, certainly a serious nutcase in many regards, personally funded extremely large projects to move human understanding off this Earth and out into space. It seems to me that today’s TRW, Hughes, NorthAmericanRockwell, General Dynamics, Aerojet General, etc. are using their advantages of getting into space to stare down at us (especially in security modes) rather than looking into the deeper more cosmic realms. How do we get them, and others, to turn around?

  • Dave

    Pepper: TESS is a great mission concept, but it is unlikely to add much to Kepler’s information on planet demographics. This is what the WFIRST exoplanet program will do. It can find planets down to the mass of Mars (0.1 Earth masses) at all separations > 0.5 AU, including free-floating planets. Already, statistical calculations indicate that the cold Saturns and Neptunes seen by ground-based microlensing are intrinsically more common than the hot planets and cold Jupiters seen by other methods.

    The main selling point for TESS, I think, is to find the closest transiting planets that can be studied in detail by larger telescopes. An explorer AO is expected in the fall, so let’s hope that they make the cut this time.

  • olderwithmoreinsurance

    Exoplanet research is, or very soon will be, quite a mature field (where “very soon” means after about one more year of Kepler analysis), thus a New Worlds Explorer mission is actually ripe for funding NOW! In terms of technology risks, it’s actually less risky now than JWST was when hardware started being built for it (it’s considerably less risky than LISA, for example, where proof of concept has not yet been demonstrated). If NONE of the 30 meter plus class telescopes are finished on time, that will have a huge detrimental effect on the field though.

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  • Sheldon

    Comment 146 on the following post, which is closed to comments, asks about a
    particular function:

    Neal, here’s your function:

    Look at the alternate form and series expansion.

  • zankaon

    Our multi-stellar system?

    Most stars form in multiples. Where are our sister stars? All of such sisters should be of somewhat similar mass, main sequence; but empirically perhaps 1 supernova. Such sisters must not be so far off. Hence might they be detectable by looking for ‘cold’ Jupiters? Use a dedicated infrared telescope to evaluate the luminosity and size of such gas giants, and through comparison, see if any are close. Such star(s) should be much less than 1 light year away, and hence within the common Oort Cloud. Thus if such sister stars are within our Oort Cloud, would it seem then to be a distorted cloud, common to such multiple star systems? However such set of sister stars would have a center of mass, and in accordance with a central force, a spherical distributed common Oort cloud of cometary material. Hence overlapping gravitational fields for such set of sister stars. Also if terrestrials are detected, then perhaps spectroscopically look for the atmospheric oxygen signature of photosynthesis. Also perhaps radio attention might be of interest for such near by sister star systems.


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