January 2007 Sky from the Keeble Observatory
Some random notes:
NASA has announced preliminary plans for a permanent base on the Moon, possibly
by 2020. With the shuttle fleet to be retired in 2010, after completion (or not)
of the International Space Station, and the next generation of crewed vehicle not
planned for launch before 2014, I wouldn’t hold my breath anticipating that it will
really happen. Indeed, with three presidential and six congressional election cycles
between now and then, it’s likely to go the way of the first President Bush’s vision
to return to the Moon as a precursor to a Mars mission.
Last month’s adieu to the Mars Global Surveyor was not the end of important results
from that long-lived orbital probe. Researchers have published findings of recent
outflows of liquid water on Mars. That Mars was warmer and wetter in its distant
geological past is generally agreed. Most planetary scientists, however, were reasonably
certain that the remaining water should be found frozen in the polar caps. Atmospheric
pressure is so low that liquid water would simultaneously boil and freeze if released
onto the surface. Images of several craters, taken at five year intervals, show
what appear to be fresh deposits of light colored material in gullies. These deposits
appear to flow around obstacles and, in at least one case, out onto the floor of
the crater. The simplest explanation is that this was caused by a brief burst of
running water from some underground aquifer, which left behind surface deposits
of salt and possibly some ice. It’s not a landslide, since we’ve found that the
sub-surface material on Mars is actually darker than the undisturbed surface. For
what it’s worth, the entire 10-year Global Surveyor program cost less than a single
Lunar phases for January: Full Moon at 8:57 am, on the 3rd; Last Quarter on the
11th, at 7:45 am; New Moon on the 18th, at 11:01 pm, and First Quarter on the 25th,
at 6:01 pm.
Predawn planet watchers will have some good targets this month. Saturn, which rises
in early evening, is still visible to the west at sunrise. As January progresses,
look for it closer and closer to the horizon, beginning the month at about 35 degrees
altitude, settling to about 10 degrees by month’s end. Jupiter and Mars are visible
in the southeast at sunrise. Jupiter rises about 2 hours before the Sun on the first,
4 hours by month’s end. Mars is about an hour ahead of the Sun all month.
After a long autumn with almost no planets to be seen in the evening, sky watchers
will have more to see this month. Venus has moved back to the east of the Sun, so
it appears as an “evening star” to the west. Look about 10 degrees above the horizon
early in the month – it sets about an hour after the Sun. By month’s end it climbs
higher, setting about 2 hours later than the Sun. Also returning by late January
is Mercury, about halfway between Venus and the Sun in the western sky. Saturn rises
about 4 hours after sunset on the first, but earlier and earlier as the month advances.
On the 31st it will rise only an hour after the Sun goes down.
At mid-month, two hours after sunset, looking directly toward zenith finds the constellation
Perseus overhead. The most prominent constellation to be seen for the winter season
is Orion, to the southeast. Working towards Orion from zenith, we encounter the
Pleiades cluster. This is a so-called “galactic cluster” or “open cluster,” which
only means that it’s in the disk of the Galaxy rather than orbiting in the halo.
This cluster is about 400 light years distant, and a relatively young 10 million
years in age. Binoculars or a small telescope will reveal more than the familiar
“seven sisters” in the familiar shape of the Subaru logo.
Below and a bit to the right of the Pleiades lies the bright red star Aldebaran
in Taurus, from an Arabic word meaning “follower.” The Bull is following the Seven
Sisters across the sky. This star, about 65 light years distant, is a “red giant”
– a star of roughly solar mass but ballooned out to about 40 solar radii. It’s actually
a binary, with a faint red dwarf companion orbiting it.
We come to Orion, and note the red star on the upper left of this familiar constellation.
This is Betelgeuse, from another Arabic word meaning “hand of the Central One,”
a red supergiant. 1 AU is the average distance from Earth to Sun; this star’s radius
is on the order of 2.8 astronomical units! The distance to Betelgeuse is about 425
light years. Comparing its apparent brightness to Aldebaran, we can see that its
greater distance requires its intrinsic brightness must be much greater – about
60,000 times as luminous as the Sun.
Next month we’ll look in detail at some of the other bright stars in Orion.
For your own monthly star chart, you can direct your web browser to
http://www.skymaps.com. You will find extensive descriptions of what's worth
looking for, and you can download and print a single copy for your personal use.