Got a Telescope? Pluto Hunters Need Your Help

This week a fleet of astronomers, partly funded by National Geographic, has been in the Pacific region capturing the first of two occultations of Pluto and its moons. Now they need your help to get the second. Find out if you’re in the predicted path of the event, and let team member Leslie Young know if you’re willing and able to lend a hand!  -V


Most of our work today is logistical, trying to find places that are in the new Pluto and Charon shadows. For Pluto, we’ve made contact at a larger telescope in Japan.

To catch the Hydra track in Hawaii, we’ll be spreading ourselves to more sites rather than trying to compare lightcurves from two telescopes at the same sites. We’re looking into adding a telescope at one of the islands in the Kwajalein atoll. This is not trivial, because you can only get there by helicopter.

As you read here, we got the June 23 Pluto and Charon occultation, and we were able to update our prediction for the Hydra shadow. The new prediction for the Hydra path is now crossing areas in Southeast Asia. Are there any telescopes that can help with this observation?

We’re looking for 11-inch or larger telescopes in Indonesia, Thailand, and Malaysia too. Our host in Cebu City, Christopher Go, knows many of the amateur groups there, and we’re making good contacts.  Anyone who is interested in helping out can contact me at


Pluto has one large moon, Charon, and two small moons, Nix and Hydra.  Nix and Hydra were only discovered six years ago, and very little is known about their physical properties. An occultation would give us the first measurement of the size of Hydra. Also, because the four bodies pull on each other in subtle ways that depend on their masses, improving the orbit will help us measure the mass. Finally, we hope to measure the cross-section of Hydra from two different angles, one from occultations and one from the New Horizons spacecraft.


The newest prediction—good to maybe 300 kilometers—is here:

See in particular:


* located anywhere within 300 kilometers of the predicted shadow
* 20 minutes of continuous images taken June 27, 14:42 to 15:02 UT
* 11-inch or larger telescope
* camera with low dead time (less than 0.1 seconds between exposures)

Best is:

* larger telescopes, which will give higher signal
* pairs or clusters of sites where telescopes are spaced 2 to 50 kilometers apart (25 kilometers is ideal)
* wide field-of-view (20 arcseconds), to make finding this crowded field easier
* integrating CCDs that can observe at 0.5 seconds with little time between exposures
* some way of telling the time of the observations
* an additional 20 minutes of continuous images taken June 27, 14:08 to 14:28 UT, in case Pluto’s shadow is actually over Malaysia


Our planning pages (finder charts, stars for star hopping, etc) are at:

Read full news coverage on National Geographic:

Leslie Young

(The Pluto occultation research is supported by NASA’s Planetary Astronomy program, NASA’s New Horizons Mission, the National Geographic Society’s Committee for Research and Exploration, and the Southwest Research Institute.)

—An artist’s concept shows Pluto (largest disk near center), its largest moon Charon, and one of its two small moons, Nix and Hydra, as seen from the surface of the other small moon. Picture courtesy NASA, ESA and G. Bacon (STScI)

Changing Planet