It's a neat trick. Every 48 days a recently discovered speck of light in the
night that astronomers call KH 15 D vanishes. Then, 20 days later
-- presto -- the star reappears. What's going on? As with any
disappearing act, it's most likely smoke and mirrors, or, in this
case, the cosmic equivalent.
Peter Garnavich, a Notre Dame associate professor of physics,
and colleagues from the Harvard-Smithsonian Center for Astrophysics
and Wesleyan University theorize that a large, swirling disk of
dust and gas, "leftovers" from the star's birth which eventually
will coalesce into a planet, is the cause of the star's periodic
winking.
Perhaps most significantly, Garnavich and his associates found
that KH 15 D's long, periodic eclipse is a new phenomenon; the
star didn't always wink. The physicists discovered no evidence
for the eclipse when they analyzed photographic plates from the
Harvard photographic plate archives of the night sky from the
first half of the 20th century.
"There are very few cases where astronomers can see a significant
change to a star over a single human lifetime," Harvard researcher
Joshua Winn says. "And if the eclipses are caused by material
in a protoplanetary disk, as suspected, then that would give us
the exciting opportunity to study planet formation on surprisingly
short time scales."
By studying when and how the eclipses begin the scientists hope
to learn more about KH 15 D and the planet forming around it.
(July 2004)
