Revision: Oversky for April 2003
- Please note the date and time for the launch of SIRFT
has been changed to Friday, April 18 at 4:32 Am. If
the article has not already been put to press, I would
appreciate the following revision. Thank you.
"Our view of Milky Way Galaxy is blocked, though, by
clouds of different type: intergalactic dust clouds.
The light and more importantly the heat from distant
suns are absorbed. Sensing that heat would allow
astronomers to detect discs around other stars where
planets may be forming, and provide valuable
information about the early life of the universe.
Nicknamed �the Old, the Cold, and the Dirty,�
(referring to the oldest, coldest and most
dust-obscured objects and processes in outer space)
these are the targets of the Space Infrared Telescope
Facility (SIRFT). Launch of SIRTF is scheduled for
Friday, April 18, 2003, at 4:32:49 AM EDT from Cape
Canaveral. SIRTF compliments the Hubble Space
Telescope. Both belong to NASA's Great Observatories
Program, each of which studies a different part of the
spectrum; Hubble shoots pictures in visible light,
Chandra takes X-ray images. Infrared light, invisible
to the human eye, is typically absorbed by Earth's
atmosphere and therefore ideal for an Earth-trailing
space telescope. More information about the mission is
Old, cold and dirty also describes comets. Comets are
interplanetary icebergs, and as a comet nears the Sun,
dust mixed in with the ice is released. A meteor
shower occurs as Earth transits through the tail of
dusty debris dispersed by a comet. Before dawn on
April 22nd the Lyrid meteor shower reaches its peak.
The meteor shower is associated with the orbit of
Comet Thatcher, which was first recorded in 687 B.C.
In April 1803, 700 meteors per hour were seen.
However, April 2003 is expect to be more modest, with
a maximum of 15 meteors per hour. Interested observers
should look northeast after midnight. The Lyrid
meteors are so named because they appear to emanate
from the constellation of Lyra the Harp, home to the
3rd brightest star of the sky. Unfortunately the last
quarter Moon rises at almost the same time as Lyra and
its light will interfere with this year's display."
Erich Landstrom, NASA JPL Solar System Educator
Solar System Educators Program http://www.ssep.org
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