• August 2, 2013

    CometCon Liveblog: Day 2

    by Josh Sokol

    This Thursday and Friday is the Comet ISON Observer’s Workshop: a meeting of comet scientists at the Johns Hopkins University Applied Physics Laboratory. We'll be liveblogging the meeting's presentations and discussion sessions here at ISONblog.

    Watch the proceedings live:

    Session 9: Wrapping Things Up

    5:07 PM The workshop has come to a close, and we at ISONblog are concluding our cable news-paced coverage. Every new beginning comes from some other beginning's end, y'all.

    4:59 PM Consensus: an informal "War Room" meeting will be held in mid-December, near the beginning of post-perihelion ISON observations.

    4:47 PM That inevitable phase of all meetings has arrived: it's time to plan the next meeting.

    4:41 PM There's already a Pinterest board for ISON images. So very Web 2.0 (2.1?) of the CIOC. This should get much more active when there are more images; once the comet is farther away from the Sun in the sky.

    4:32 PM Now Karl Battams is giving a broader review of that same CIOC (Comet ISON Observing Campaign) website, It's a great resource to learn about ISON observing plans, especially for those on the amateur/professional observing spectrum.

    4:18 PM Mike Kelley is presenting the ISON Observing Timeline, a place to record upcoming professional observations of ISON, at

    4:15 PM Though titled "Closure," that last part wasn’t the ending. That was the beginning of the ending, and this is the real ending. Maybe. It’s a lot like Lord of the Rings.

    Session 8: Closure

    4:13 PM Discussion has turned to the best ways to disseminate information about observing ISON. Twitter alerts? A static website?

    4:05 PM Meech is stressing the need for effective communication and emphasizing the role of amateurs. She ends with a note of caution: we'll need to be careful about coordinating all these exciting space-based assets and archiving our data. Most importantly, ISON observers will need to work together.

    4:00 PM There's a lot of potential in studying ISON, says Meech. "Much has changed since Kohoutek or Hale Bopp," so we'll have a huge amount of data to learn from.

    3:55 PM Does ISON's flat brightness curve mean it will be a dud? Not necessarily. It could have a shallow reserve of super-volatiles (not water) that has been mostly exhausted, with more waiting to be uncovered by continued activity.

    3:50 PM Meech's big ISON questions:

    • Is it rich or poor in volatiles?
    • What causes it to be active?
    • How big is the nucleus?
    • How fast is it rotating?
    • How much gas and dust will it produce?

    3:46 PM Meech is discussing changing paradigms of comet formation and volatiles in the solar nebula – current models hold that there was a lot of mixing during the formation of the giant planets.

    3:42 PM Via webcast, Karen Meech is zooming us out to see the big picture. She brings up two main NASA goals:

    • to understand solar system formation
    • to understand the primordial sources of organics and volatiles (because, you know, life)

    Session 7: Dust/Solids

    3:22 PM "Clear skies willing and good space weather willing, we'll have a good picture of the dust around this comet. It's just a matter of getting good synergy between our groups," says Mike Kelley.

    3:17 PM During discussion a question came up: many telescopes seems to be planning to observe ISON in January. Why not earlier, after perihelion in December? Well, ISON will still be very near the Sun. But some people will be looking at ISON in December – everyone has their own window, and will be gunning for the best possible views.

    3:04 PM Controversy! During open discussion, Mike Mumma thinks Diane Wooden overstated claims about the discovery of organic grains in comets.  At issue are a 1990s paper Wooden referenced, and the maybe-detection of PAHs.

    2:46 PM My boss Max Mutchler is speaking about how the Hubble Heritage team is working to engage the public with ISONblog. Hey, that's me! He's got a great page of Hubble's ISON data at

    2:41 PM Contributed talks on observing dust roll on, transforming the workshop into a dust bowl –  just with less Dorothea Lange and no manmade ecological catastrophe. Anyway, dust! We march forward.

    2:31 PM Takafumi Ootsubo is outlining what the Subaru Observatory plans to do with their mid-infrared COMICS instrument. They're going to look at dust, mostly to count up different types of silicate grains and crystals. At this point, it's news if someone's not observing ISON.

    2:24 PM Dean Hines just presented the results of polarized ISON observations done with Hubble in April. (Check ISONblog for an interview with Dean next week!) He's also got 12 more Hubble orbits to look at ISON this fall, and is looking for collaborators.

    2:12 PM According to Knight, measuring AF-rho is a great way for amateurs to participate.

    2:07 PM Now Mathew Knight is describing AF-rho, a quantity for measuring how much dust a comet produces. Let's break it down. "A" is for albedo, the amount of sunlight reflected by the comet. "F" is the filling factor, a measure of how many grains are in your line of sight. The Greek letter rho refers to the comet's size.

    2:04 PM Like finding other atoms or molecules, hunting down PAHs on comets is hard – but really cool. We know how to identify tons of carbon compounds in the lab, but on comets they're piled up on top of each other in rings and chains. It's all about matching distinct spectral lines to the molecules we think caused them.

    1:58 PM Diane Wooden is now discussing PAHs: complex organic compounds that may be found in comet dust.

    1:52 PM ISON likely has a thin skin. Sunlight only penetrates through about the top three centimeters of a comet's surface – this is where water ice is subliming and the dust is coming off. Wooden is showing this illustration of dust production:

    1:47 PM Wooden: we've observed that dust compostion and dust grain structure vary depending on where you look in a comet's coma. The question is: are the differences A) due to where the grains came from in the nucleus, or B) due to how they were processed on the comet's surface?

    1:34 PM We're back from lunch, and Diane Wooden is discussing what we'd like to learn about ISON's dust. What is its composition? Is it coming from a rime (an icy crust), the mantle, or the comet's interior?

    Session 6: Organics

    11:45 AM Group picture time!

    11:42 AM In the room, there's an ongoing discussion about isotopic ratios in comets, stemming from the question: have we ever seen a comet captured from another solar system? (Probably not). Meanwhile, the livestream chat seems to have fended off an attack from religious conspiracy theorists.

    11:28 AM Everyone's buddy-buddy here on the collaborations between typically competitive scientists that made all these coordinated ISON plans possible. It's adorable.

    11:26 AM Total Keck + IRTF commitment: 62 blocks of time over roughly 100 days between October and January. NASA is all in on this one.

    11:23 AM And of course the Keck Observatory, at the summit of Mauna Kea, is in on it too. Keck's goals are similar to IRTF, but with bigger telescopes that will zoom in on the question of volatile chemistry.

    11:17 AM IRTF ISON programs: study gas abundances, the mineralogy of ISON's dust grains, the polarization of coma dust as it's eroded and irradiated by the Sun, and the chemistry of volatiles. The point of all of these is to look at evolution over time; as ISON approaches and then recedes from the Sun.

    11:10 AM Now Neil Dello Russo is describing what NASA's IRTF (Infrared Telescope Facility) will do.

    11:05 AM Another goal is to measure "tracer" compounds like hydrogen cyanide, which are present in proportion to the amount of more volatile, harder-to-find materials on the comet.

    11:01 AM Stefanie Milam is walking through her plans to use radio observatories to study ISON's organics. One goal is to find the ratio of deuterium to hydrogen – this will help show what the materials making up ISON have been up to since the birth of the solar system.

    10:48 AM Mumma is wrapping up his comprehensive review of cometary organic chemistry. I speak for the uninitiated: it's like trying to drink from a fire hose – a fire hose filled with hydrocarbon sludge in which all the molecules have different masses or spin states.

    10:36 AM If ISON becomes super bright, Mumma says, we may be able to detect organic compounds that have never before been seen on a comet. Perhaps more importantly: we'll be able to measure the abundances of many previously-seen molecules and their isotopes .

    10:33 AM Mike Mumma is reviewing what we know of organic chemistry on comets. Since comet organics are left over from the protoplanetary disk, we need to measure the abundances of these compounds to choose between competing models of solar-system formation.

    Session 5: Comet-Sun Interaction

    9:52 AM Using the Isaac Newton Telescope in the Canary Islands, Yudish Ramanjooloo will be studying ISON's ion and sodium tails.

    9:47 AM Kimberley Birkett just finished introducing a predictive model of what ISON's sodium tail might look like – that's a fainter, rarer tail of sodium atoms torn away from a comet's coma.

    9:39 AM Geraint Jones is discussing how striations form as the dust tails of comets fragment. Does the solar wind play a role?

    9:27 AM So why do solar physicists care about ISON? "It's sort of a free solar probe, except it's a solar probe that can fly through a domain where no man-made probe could ever go." ISON will pass through a place scientists would like to better understand: the transitional area between the close solar environment and the start of the solar wind.

    9:21 AM Case in point: in 2011, Comet Lovejoy's tail "wiggled" near the Sun as ions from the comet got caught in the Sun's magnetic field – this helps show the (very complex) magnetism of the corona.

    9:05 AM Karel Schrijver is kicking off the day from a solar physics perspective. He's showing videos of sungrazing comets at closest approach. As they go, comets "drops tracers, breadcrumbs" that sample the physics of the corona.