Peering into the future

By Daniel Holz | August 18, 2010 10:14 am

The big news this week in astrophysics is not the discovery of a new planet. Nor is it the first glimpse of a galaxy on the other side of the Universe. It’s much more important: the arrival of the latest Decadal Report. It all started over a year ago, and fellow blogger Julianne has been a major participant.

0309157994The full report is an excellent description of the entire field, both where we are now, and where we’re likely to be headed. If 200+ pages is a bit much to swallow, the report contains a 5 page Executive Summary (with 5 tables laying out the project rankings and costs). Probably the best place to start, however, is Julianne’s discussion of the report: post 1, post 2, and post 3.

For those with no attention span whatsoever, here is my 6 bullet-point summary:
1. Surveys rule the roost. The next decade is about survey telescopes. The #1 space priority is an infrared survey telescope (WFIRST) (a successor of SNAP/JDEM). The #1 ground priority is a wide-field optical survey telescope (LSST).
2. Another golden decade of cosmology (and planets). Both the top space and ground priorities originated as dark energy/cosmology missions. They turn out to be excellent planet missions as well.
3. Bang for the buck. Smaller, diverse, rapid-response programs provide excellent science return. The “Explorer program” and the “Mid-scale Innovations Program” are the #2 priorities for space and ground, respectively. Specific missions within these programs are unspecified.
4. The birth of gravitational-wave astronomy. We are (hopefully) entering the decade of gravitational-wave astrophysics. The Laser Interferometer Space Antenna (LISA) is the 3rd ranked space mission. This is a big deal: gravitational-waves have yet to be seen, but the astronomical community nonetheless recognizes and prioritizes the role they have to play in exploring our Universe.
5. Clash of the Titans. The 3rd priority for ground-based astronomy is a huge (30 meter) optical/infrared telescope. There are two projects well underway (GMT and TMT). The report encourages the NSF to pick one for federal investment.
6. Etcetera. Other things that are discussed include an X-ray telescope (IXO), a high-energy gamma ray telescope (ACTA), a submillimeter telescope (CCAT), and a number of smaller missions and projects (including full funding for NASA’s Astrophysics Theory Program). Note that the Hubble Space Telescope’s successor, the James Webb Space Telescope (JWST), is not extensively discussed in this report, since it is already funded and is on track for launch in the next few years.

I’m excited about all of these facilities. I’ve written papers related to many of them (JDEM, LISA, and LSST), and I am convinced they will all profoundly deepen our understanding of our Universe. The Decadal report represents a tremendous investment by the astro community, involving hundreds of scientists making extremely painful and difficult choices. At the end of the day, a clear ranking has been produced, and a strong case has been articulated. Now the task it to convince the full astronomy community, Congress, and the taxpayers that we have done our homework, and that these missions are worthy of major public investment. We have an incredible decade ahead of us!

CATEGORIZED UNDER: Science, Science and Politics
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  • Nathan

    …if everything gets funded. Which is unlikely.

  • Jimbo

    Daniel, I hope you are right, & that these projects will pay real dividends in cosmology & astrophysics.
    An embarrassment to the community is LIGO. Sold to congress for a few percent of the price of the SSC, it has published null results & dismal science runs for the last decade, deferring any chance of direct detection of grav waves to advanced LIGO. Making ridiculous claims about sphericity limits on neutron binaries, based upon non-detection of grav waves, was the pinnacle of absurdity. Lets hope LISA can deliver the goods & leapfrog over LIGO in its first few years of operation.
    Also, I am wondering if the report recommends allocating any $$ for table-top expts. to detect dark energy ? Several papers have been published on ideas, that have been largely overlooked.

  • Dave

    Daniel, it is not really true to imply that WFIRST originated as a dark energy/cosmology mission. The exoplanet and cosmology mission concepts were developed in parallel. The first space-based microlensing planet search concept, the Galactic Exoplanet Survey Telescope (GEST) was proposed to NASA’s Discovery program in 2000. This predated all of the dark energy mission concepts except for SNAP, which at that point probably included only a supernova search. In 2001, a version of GEST was proposed to NASA’s Midex competition, and this included a microlensing planet search, a weak lensing program, and a modest supernova program (without a spectrograph). But this was not really affordable on a Midex budget.

    Anyway, the main reason why these missions have not been merged before now is the limits on the types of science that different programs fund. SNAP was originally proposed as a DOE program, and the DOE does not fund extrasolar planet research. In contrast, the microlensing planet search program was proposed to NASA’s Discovery program, which only supported the study of solar systems (ours or others). (Exoplanets have been dropped from this year’s Discovery proposals, however.)

  • bittergradstudent

    Jimbo:

    LIGO and LISA are looking for different things, and for waves in different wavelength regimes. Saying that one will ‘leapfrog’ the other is kind of ridiculous. They are two complimentary projects. Also, LISA, even if it gets funded, is still probably a decade off.

  • Martin E.

    All worthy missions, and the number is limited because astrophysics has hit the Funding Wall. But still it is interesting to compare the choices against the input received from the community, as shown in the Wordle at: http://www.wordle.net/show/wrdl/560560/Astro_2010_Science_White_Paper_Titles
    Try picking out where the recommended missions are located.

  • Shantanu

    Jimbo, I am not too sanguine about LISA. The one lesson we have learned
    from LIGO is that every new science run has shown up new sources of noise which we never anticipated. However because it is on the ground, those could be fixed. With LISA, there is no such hope.

  • Jimbo

    Bittter Grad….Now I understand why you are bitter !
    Of course LIGO & LISA are for 2 different spectral bands !…By “leapfrogging” I simply meant in terms of success. LISA should leave LIGO in the dust. Also, my understanding is that LISA is meant to liftoff on or about 5 yrs from now ?
    Shantanu: You are right about 2 things: LISA is non-repairable or tweakable, except via SW. If an alignment laser dies, LISA is S.O.L, & I don’t refer to the sun’s nickname ! Of course Gravity Probe-B was similarly `space-critical’, but it survived its mission & delivered data.
    More exciting is GEO, which has evidenced a noise source that Craig Hogan has predicted is traceable to Planck scale noise. It’s still being analyzed, but if it holds up, this will blow any detection of grav waves by LISA or LIGO out of the proverbial water. What Quantum Gravity phenomenologist would’ve ever expected to see its signature in a low-energy expt.?
    Exactly analogous to seeing the signature of the big bang in the microwave spectrum, but it happened, 45 yrs ago.

  • Brian137

    Hi Jimbo,
    I am really excited about the progress of and prospects for LIGO and its partners. Although I would enjoy a positive detection in the current run, I have been led to believe that such an event is unlikely, but that Advanced LIGO should see plenty of gravitational waves. These prospects are consistent with what we were all told over a decade ago. The required level of sensitivity is daunting, but the experiment seems to be proceeding as originally described.

  • Dave

    I’m afraid that LISA science is not 5 or 10 years off, but instead 15 or more. The decadal report says LISA could launch be 2025 if all goes well with the LISA pathfinder.

    As far a LIGO is concerned, they haven’t delivered any less than expected. The idea that they would see any astrophysical signal prior to advanced LIGO relied upon wishful thinking about gravity wave sources, and this is what they said when they sold the project. Let’s hope that they can get to the advanced LIGO sensitivity that they promised, because there will be many sources to observe if they do.

  • Dan C

    So with LISA at #3, what are its realistic chances for funding in the next 10 years?

  • JT

    It’s important to remember that LISA is about observing and studying gravitational waves, not just detecting them. In other words, it isn’t a yes/no experiment to test whether gravitational waves exist but a tool for studying the universe through gravitational waves. There are a number of ideas for how we can use LISA observations to study cosmology, structure formation, stellar evolution, etc. Many of these have been extensively studied and documented in the literature, quite remarkable considering we are at least 10-15 years away from launch. So I have to respectfully disagree with Jimbo that GEO is “more exciting” than LISA. It’s exciting because its real and there is a (small?) possibility that something interesting could be lurking there in the form of Planck scale noise. Even if this were to pan out, I would argue that we would still want LISA for the astrophysics potential alone.

  • Shantanu

    Jimbo : I am not sure how excited quantum gravity people are about GEO excess noise. Sean/Mark/Joanne : Am I right? I haven’t seen any string theorists or people working
    on beyond SM physics discuss this result much.
    Brian 137: There is no guaranteed source in the sky even for advanced LIGO. The hope is that
    we should see many NS-BH/NS-BH mergers.
    However the theoretical estimates of these very by several orders of magnitude.
    However people thought, from past experience in astronomy where there were plenty of surprises
    same thing would happen in grav. waves. But sometimes there are just no surprises.
    See this talk

  • Shantanu

    Jimbo : I am not sure how excited quantum gravity people are about GEO excess noise. Sean/Mark/Joanne : Am I right? I haven’t seen any string theorists or people working
    on beyond SM physics discuss this result much.
    Brian 137: There is no guaranteed source in the sky even for advanced LIGO. The hope is that
    we should see many NS-BH/NS-BH mergers.
    However the theoretical estimates of these very by several orders of magnitude.
    I agree with Dave. However people thought, from past experience in astronomy where there were plenty of surprises
    same thing would happen in grav. waves. But sometimes there are just no surprises.
    See this talk

  • Brian137

    Shantanu,
    Thank you for the link.

    There is no guaranteed source in the sky even for advanced LIGO. The hope is that
    we should see many NS-BH/NS-BH mergers.
    However the theoretical estimates of these very by several orders of magnitude.

    The projections I have seen seem pretty optimistic, but your remark may inspire me to do a better job of controlling my cholesterol.

  • Charon

    “the Hubble Space Telescope‚Äôs successor, the James Webb Space Telescope (JWST)”

    WTF? Seriously? You do realize that JWST has no UV or optical capabilities, right? “NGST”, the “Next Generation Space Telescope” was originally conceived as a successor to HST, and was portrayed that way in one of the first professional astro talks I went to, in 1998. But then NGST became JWST, and it is not a successor to HST. It’s IR-only.

    Which means that in a few years we might have nothing in space but IR telescopes. No gamma-ray, no x-ray, no UV, no optical, no microwave. And of course, with the exception of optical, we can’t do any of that from the ground. I sure hope some explorer-class missions in those regimes are launched…

  • Thomas

    X-ray community will have ASTRO-H and NuSTAR. WFIRST will have substrate removed NIR detectors with good QE down through 400 nm so you’ll have all sky visible imaging as well. FERMI won’t die anytime soon, I think, so they’ll go through a few more senior reviews for mission extension for the gamma ray community. And I am fairly sure that the UV community will look for opportunities in the Explorer AO out now (draft). And, of course, Herschel and Planck are still working in various regimes of the microwave spectrum. So, it doesn’t seem quite as dire as you said, to me at least.

  • Brian137

    Maybe this is a bit off the original topic, but it fits in with discussion of detectors for gravitational waves. Here is an update on the possibility of using using pulsars.

    http://www.physorg.com/news201883321.html

    Old news, perhaps, but an intriguing idea nonetheless.

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