Mombu 2012-06-21 02:04:42
ARIZONA TELESCOPES WILL FOCUS ON PLUTO MARCH 18
(From Lori Stiles, University Communications, 520-626-4402)
— Wednesday, March 14, 2007
Contact information listed at the end
Telescopes from Wyoming to Mexico City and from California to central
will point at Pluto as the dwarf planet occults a star in the
constellation next Sunday.
University of Arizona astronomers will host colleagues from Paris
Observatory, the Massachusetts Institute of Technology and Lowell
Observatory at UA telescopes for the not-to-be-missed event.
Arizona has a special tie to Pluto: Astronomer Clyde Tombaugh was
for Lowell Observatory in Flagstaff when he discovered the ninth
1930. Tombaugh was the only American ever to discover a planet in our
system. The International Astronomical Union ignited public and
controversy last August when it downgraded Pluto’s status to a dwarf
known as number 134340.
But whatever you call it, the object interests planetary scientists.
“Occultations are the only way we can monitor the atmosphere of Pluto
the Earth,” said Professor William B. Hubbard of UA’s Lunar and
Laboratory, who is coordinating the UA campaign to observe the Pluto
Not only are the observations important to scientists studying Pluto’s
atmosphere, Hubbard said, they’re important to NASA’s $620 million New
Horizons spaceprobe, which just flew by Jupiter and is on target to
Pluto and the Kuiper belt in 2015. Previous observations of Pluto
occultations have yielded surprising findings about Pluto’s changing
pressure, for example, Hubbard said, “so it’s going to be important to
track of what Pluto is doing until the spacecraft gets there.”
An occultation is like an eclipse. Just as the moon casts its shadow
Earth when it passes directly in front of the sun, planets cast their
shadows onto Earth when they pass directly in front of a star.
Bruno Sicardy of the Paris Observatory and Faith Vilas, who is now
of the MMT Observatory, discovered Neptune’s rings in the 1980s,
Voyager detected them, from ground-based observations made during a
In past decades, astronomers could typically expect a Pluto
only every five to 10 years, Sicardy said. But now Pluto is moving in
of the Milky Way, and astronomers may see one or two Pluto
year because of the abundance of background stars.
“But even though there are now more than one of these events per year,
can’t count on seeing them all because of cloudy weather, or because
shadow falls on Earth where there are no observatories,” Sicardy said.
“This time, the event is observable by a region of the world populated
great telescopes — the southwestern United States,” Sicardy said. “To
observe this in Arizona is like closing a big loop after more than 70
It’s kind of like celebrating Pluto’s discovery,” he added.
Pluto has a diameter of 2,775 kilometers, or about 1,400 miles, and is
almost 40 times farther from the sun than the Earth is. It will pass
front of the star in Sagittarius at 4 a.m. Arizona time (11 Universal
on Sunday, March 18. The occultation will last six minutes — about 3
longer than typical Pluto occultations — giving telescopes as small
centimeters (20 inches) time to record the event.
If the telescope is aligned in the exact line of sight with the star
Pluto eclipses the starlight, its lucky astronomers might see the
flash” phenomenon. They would see a sudden brightening, a flash, while
entirely in Pluto’s shadow. That could give them important information
the shape of Pluto’s atmosphere or its winds, as well as a thrill.
All the visible light cameras are fast readout cameras with good time
resolution, said Lunar and Planetary Laboratory scientist Steve
He’ll observe with the 61-inch Kuiper Telescope in the Santa Catalina
Mountains north of Tucson. “This will help provide accurate timings of
ingress, egress and a central flash if we are situated right,” he
Participating UA astronomers and telescopes include:
o The UA/Smithsonian Institution’s 6.5-meter (260-inch) MMT on
Hopkins. Steward Observatory astronomers Donald W. McCarthy and Craig
will use a wide-field infrared camera called “PISCES” that may spot
or haze if they exist in Pluto’s atmosphere. At the same time, Susan
and Michael Person of MIT will use a “POETS” camera loaned by Lowell
Observatory to observe at optical wavelengths. POETS is an acronym for
Portable Occultation Eclipse and Transit System. http://www.mmto.org/
o Bruno Sicardy will use a camera from his Paris Observatory on
90-inch (2.3 meter) Bok Telescope on Kitt Peak. His visible light
takes 10 frames per second. The Bok Telescope is the largest operated
by the UA Steward Observatory.
o Catalina Sky Survey Director Steve Larson of UA’s Lunar and
Planetary Laboratory and Thomas Widemann of the Paris Observatory will
observe with Steward Observatory’s 61-inch (1.6 meter) Kuiper
the Santa Catalina Mountains north of Tucson.
o Rick Hill of UA’s Lunar and Planetary Laboratory and Henry
Lowell Observatory will use UA’s 60-inch (1.5 meter) telescope on
Observatory’s Mount Lemmon site.
William B. Hubbard 520-621-6942 firstname.lastname@example.org
Donald W. McCathy 520-621-4079 email@example.com
Steve Larson 520-621-4973 firstname.lastname@example.org
Richard Hill 520-621-4077 email@example.com
Bruno Sicardy http://www.lesia.obspm.fr/~sicardy/
Thomas Widemann http://www.lesia.obspm.fr/~widemann/
Related Web sites
6.5 meter MMT Observatory – http://www.mmto.org/
90-inch Bok – http://james.as.arizona.edu/%7Epsmith/90inch/90inch.html
61-inch Kuiper Telescope- http://james.as.arizona.edu/~psmith/61inch/
60-inch Mount Lemmon Telescope – http://james.as.arizona.edu/~psmith/60inch/