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July
1, 2008: News Flash: On 4th of July weekend, NASA
forecasts lights in the sky.
No,
not those lights. Look beyond the fireworks. Almost
halfway up the western sky, just above the twilight glow of
sunset, a trio of worlds is gathering: Saturn, Mars and the
crescent Moon.
Above:
Fireworks over Jodrell Bank, England, on the 2008 summer solstice.
Photo credit: Andrew Greenwood.
The
show gets going on Friday, July 4th. Red
Mars and ringed Saturn converge just to the left of the bright
star Regulus. The three lights make a pretty 1st-magnitude
line in the heavens: sky
map.
But
that is just the beginning. On Saturday, July 5th,
with weekend fireworks at fever pitch, a lovely crescent Moon
joins the show. Saturn, Mars, and the Moon trace an even brighter
line than the night before: sky
map.
Scan a small telescope
along the line. You'll see Saturn's rings, the little red
disk of Mars, a grand sweep of lunar mountains and craters,
and just maybe—flash!—a manmade incendiary. How often do you
see fireworks through a telescope?
This is, however,
more than just a flashy gathering of planets—it is also a
gathering of spaceships and robots.
Each
of the three worlds is orbited or inhabited by probes from
Earth. Saturn has the Cassini spacecraft, studying the gas
giant's storms, moons and rings. The Moon has two probes in
orbit: Kaguya from Japan and Chang'e-1 from China. The pair,
operating independently, are mapping the Moon and scanning
for resources in advance of future human landings. NASA's
Lunar Reconnaissance Orbiter will join them later this year.
Right:
An artist's concept of Lunar Reconnaissance Orbiter slated
to launch later this year. [more]
Mars
has more probes than the others combined. Three active satellites
orbit the red planet: Europe's Mars Express and NASA's Mars
Odyssey and Mars Reconnaissance Orbiter. The three not only
study Mars with their own instruments, but also form a satellite
network in support of NASA's Mars rovers Spirit and Opportunity
and Mars lander Phoenix.
None
of these mechanical specks are visible in a backyard telescope,
but they are there, heralds of a growing human presence in
the solar system. Tell that to your buddy at the fireworks
show!
During
the short night of July 5th, the Moon glides past Mars and
Saturn so that nightfall on Sunday, July 6th,
brings a different arrangement—a scalene triangle. The triad
is easy to find in the hours after sunset. Look west and let
the Moon be your guide: sky
map.
In
the nights that follow, the Moon exits stage left, leaving
the others behind. Don't stop watching, though. Saturn and
Mars are converging for their closest encounter of the next
14 years. After nightfall on Thursday, July 10th,
the two planets will be just ¾ of a degree apart, snug enough
to fit behind the tip of your pinky finger held at arm's length:
sky map.
Now
that's spectacular—no fireworks required.
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Author: Dr.
Tony Phillips | Credit: Science@NASA
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