Kagoshima University Observatory and the (20000) Varuna occultation of 2012

January 2, 2012

Like a number of research universities, Kagoshima University has its own observatory. Nestled in rolling hills reminding me of Marin County and surrounded by beef cattle fields* (also a university property), the observatory is home both radio and visible wavelength astronomy facilities. A large radio telescope downhill from the optical observatory faded into the evening light.

Our telescope was a 1-meter reflector, operated by a posse of graduate students.  How to change the mirror configuration?  Put one of said grad students on a ladder, then grab his belt loops so he doesn’t fall into the primary mirror.

Why travel several thousand miles by squeezing onto Shinkansen like sardines to visit this observatory? A minor planet, known by its number (20000) or its name Varuna after a Hindu god, was predicted to pass in front of a particular star, occulting the distant stellar object’s light. Varuna’s shadow as cast by the star would sweep across the Pacific Ocean that night, ostensibly visible from Japan, Hawaii, China, Thailand, and other neighboring countries.  The actual occultation only occurs for a few seconds.

(20000) Varuna's shadow predicted track across the Pacific

Measuring this dip in brightness helps inform better orbital models for Varuna, search for companion moons, and even probe the existence of an atmosphere around the tiny, icy world.

With the Kagoshima University Observatory 1-meter telescope perfectly situated to see this occultation event, the MIT Planetary Astronomy Laboratory sent a high speed camera, capable of reading out consistent low-noise images at a specific cadence using GPS timing. Know as the Portable Instrument for Capturing Occultations, PICO was designed to be easy to attach to any telescope around the world. I’d previously helped fit it to the Jet Propulsion Laboratory’s 24-inch telescope at their Table Mountain Observatory in the mountains above Wrightwood, California.

PICO travels in a carry-on suitcase with a red “MIT” sticker on it. The first time I flew with PICO, the TSA screener at Boston Logan Airport was curious as to what career path involved lugging a suitcase filled with a laptop, a boxy camera, a GPS timing unit, and perhaps a hundred feet of various USB and power cables through his security line. “I’m an astronomer,” I answered, struggling into my MIT hoodie which matched PICO’s sticker. “Did you have to go to school long for that?” I laughed.


No red lights illuminate the dome in Kagoshima, and one dons slippers when entering the building out of deference to the cleanliness of the instruments. Sliding everywhere on vinyl slippers, I teetered down the ladder from the telescope. How could this possibly be safe?

In western observatories, we at the very least dim the lights to preserve our night vision, and wearing slippers that neither keep your feet warm nor stay on while going up ladders would seem to be a hazard; yet, this is how astronomy happens in the Land of the Rising Sun. Cleanliness is more important than comfort. Well-illuminated working areas are more important than preserving night vision. Even the radio telescope remained lit up at night by sodium vapor lamps. How was this affecting imaging at our optical telescope?

Things are different here in Japan, not better or worse. I shivered while standing in the dark under the telescope and tried not to faceplant while navigating the ladder. We all have a love of stars and planets (or, as the Japanese say, “wandering stars”), and even though the ways we set about doing science on these objects differ, our goals are ultimately the same.  Just don’t faceplant on your way down the ladder.

Perhaps a “cultural differences for astronomers” course at Wellesley could count toward the humanities distribution requirement.

It was astoundingly cold in the dome, and because of the nature of the PICO system, I had to huddle under a blanket under the telescope to take images.

PICO is the black box in the upper right; the control netbook is in the lower right.  GPS timing systems are the boxes to the netbook’s left on the ground.

The sun set as dastardly clouds rolled in over the hills.

The time of the occultation came and went with the sky covered with a blanket of clouds. So goes science. Our hosts at Sendai Space Hall and Kagoshima University were generous and kind; perhaps they’d get the chance to use our facilities in exchange some day. I packed up PICO and went back to the hotel to sleep as much as I could as the clouds gathered and it began to rain. We’d tried, that was what was important.  Science sometimes is successful; sometimes it’s not.  Life goes on; there are always more photons to collect.

Many thanks to the MIT Planetary Astronomy Laboratory for sending me to 鹿児島県 for this occultation.  Next time I’ll pack a cloud-zapping laser.

* Kagoshima-ken is famous for its black pigs fed a diet of sweet potatoes. I assume these black cows followed a similar diet. Local sweet potatoes not fed to livestock were distilled into a strong clear local alcohol, apparently pure enough to cause no hangovers.

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