February 2005 Sky from the Keeble Observatory
After seven years hitching a ride on the Cassini spacecraft, the
Huygens probe took center stage and delivered a nearly flawless
performance. Omission of commands to activate one of the radio receivers
on Cassini meant that about half the data were irretrievably lost.
Even so, the remaining data are giving us our first close up look
at the atmosphere and surface of Titan. Saturn's largest moon is
the only satellite in the solar system with a substantial atmosphere.
Methane haze in that nitrogen atmosphere had kept the surface shrouded
in mystery ... until Huygens arrived.
One of the strangest places in the solar system, it was amazing
to see how familiar the surface looks. River channels carved through
low hills, leading to large lakes. Low lying fog clings to the shore
line in places. Islands poke out of the sea.
(Image courtesy of European Space Agency, National Aeronautics
and Space Administration, and the Lunar and Planetary Lab at the
University of Arizona.)
Huygens parachuted to a soft landing near one of the lakes, landing
on a surface the consistency of wet sand. Pictures from the surface
show small "boulders," which appear to have been tossed
and smoothed in flowing liquid. Researchers claim evidence that
it has "rained" recently.
But this is not familiar territory! The rain, rivers, and lakes
are liquid methane, at about 200 degrees below zero, and the fog
is also methane. There does not appear to be any standing liquid
at the moment, but the consistency of the surface suggests that
the liquid lies just below in the "sand." The boulders
and sand are most likely frozen water ice! We need to be cautious
about drawing too many conclusions - we've seen only a tiny fraction
Cassini continues it orbital examination of Saturn and her moons.
Huygens' batteries are long since expired, and it will be decades
(at best) before we can get another look at the surface of Titan.
Lost data notwithstanding, there will be much to learn from the
Lunar phases for February: Last Quarter on the 2nd, at 2:27 am;
New Moon at 5:28 pm, on the 8th; First Quarter on the 15th, at 7:16
pm; Full Moon on the 23rd, at 11:54 pm.
Evening planet watchers will have Saturn available all month. At
sunset early in the month, look for the ringed planet (and current
"home" of Cassini) emerging from the twilight in the constellation
Gemini, about 20 degrees above the eastern horizon. By month's end
it will be almost fifty degrees above the horizon at sunset. Jupiter
rises earlier as the month progresses, almost 5 hours after sunset
as we begin the month, only 3 hours after sunset by time we turn
our calendars to March.
By the end of February, Mercury will have moved back to the evening
sky. Early in the month Mercury and Venus are low on the eastern
horizon at sunrise. Their orbits will carry them into the Sun's
glare by the middle of the month, with swifter Mercury visible about
15 degrees above the setting Sun on the 28th.
Three hours after sunset at mid-month, the view directly overhead
will be bracketed by Castor, Pollux, and Saturn to the southeast
and Capella to the northwest in Auriga. At this time the Milky Way
will divide the sky, roughly northeast to southwest. To the east
you'll see bright Regulus in the constellation Leo. Approximately
midway between Leo and Gemini lies the open star cluster known as
the Beehive; it is also known as Praesepe, which means "the
manger." Binoculars or a small telescope will reveal several
hundred stars, spanning about 10 light years. This cluster is about
580 light years distant, and our models of stellar evolution tell
us that these stars are some 400 million years old ... much younger
than our own Sun and planets.
Orion is obvious to the south, trailed by the brightest star visible
in the night sky, brilliant Sirius in Canis Major. This bright blue
star has a small "white dwarf" companion, not visible
without a large telescope. This is the burned out remnant of a star
once much like our Sun. Sirius will eventually evolve into a red
giant, like Betelgeuse (visible in Orion). When this happens, hydrogen
from its outer atmosphere may accrete onto the white dwarf, eventually
erupting into a "nova" as the hydrogen reaches critical
temperature and density and triggers thermonuclear fusion into helium.
Turning to the north, we see the familiar inverted "big dipper"
of Ursa Major above and to the right of Polaris. Cassiopeia is to
the northwest, its familiar W shape tipped sideways to resemble
a Greek sigma.
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