May 2004 Sky from the Keeble Observatory
Southern hemisphere skywatchers are already seeing two comets which should grace
our early evening skies from mid-May into June. Both were discovered several years
ago, and are now passing through the inner solar system. They will be visible about
an hour after sunset, and may brighten to "naked eye" visibility.
The first of these, designated C/2001 Q4, is also known as Comet NEAT, since it
was discovered by the Near Earth Asteroid Tracking program. It will pass quickly
through the constellations Canis Major and Puppis, into Monoceros by May 10, getting
progressively higher above the western horizon at sunset. Look for it in Cancer,
below Jupiter, about 45 degrees above the horizon on the 15th, about an hour after
the sun sets. The tail should be stretching up and to the left. By the end of the
month, it should be above Venus, in the constellation Lynx, with its tail pointing
straight up from the horizon. Once you find it with binoculars (or naked eye, if
we're lucky) you should be able to track its motion from night to night. On the
25th it will be close to the Moon on the sky.
The second was also discovered by a research program actually designed to detect
and track near Earth asteroids, this one the Lincoln Laboratory Near Earth Asteroid
Research program. C/ 2002 T7 is thus known as Comet LINEAR. At month's end, you
should be able to find this one about 30 degrees off the western horizon at about
9:00 pm. It will be below Jupiter, in the constellation Hydra. By the end of June
it will move into Sextans.
Next month we'll discuss just what comets are.
Lunar phases for May: Full Moon on the 4th; Last Quarter on the 11th; New Moon on
the 19th; First Quarter on the 27th. The Full Moon will be accompanied by a total
lunar eclipse, but will not be visible from North America.
Evening planet watching is still possible in May. After the Sun sets, you'll see
four planets emerge from evening twilight. Closest to the horizon (and also the
brightest) is Venus. Next Mars, Saturn, and Jupiter high above and a bit south of
west. They are all moving closer to the Sun on the sky, but for different reasons.
Venus is closer to the Sun than Earth, and moves faster in its orbit than we do.
It's catching up, and will pass directly in front of the Sun in June. Mars, Jupiter,
and Saturn are all farther away. We're pulling around behind the Sun from their
perspectives. Venus, Mars, and Saturn lie on a straight line, which extends up to
Jupiter. They'll set earlier each evening, leaving Jupiter the lone visible planet
for a while. Enjoy them while they're still in the evening sky.
Mercury is in the morning sky, but very close (less than 10 degrees) to the horizon,
so it will be hard to see. Your best bet may be on the 16th, when the almost new
Moon will be just above and to the right of Mercury.
Looking overhead about two hours after sunset may seem disappointing. There are
no bright stars near zenith. However, there's still lots to see.
Towards the north we see the inverted dipper of Ursa Major almost at zenith. On
a clear night, your binoculars may enable you to see further than those stars. Almost
3 ½ degrees directly above Alkaid, the end star of the Dipper's handle, lies
M 51 - the "Whirlpool Galaxy." With binoculars, you'll likely see only
a faint smudge. In a modest telescope it will appear like a faint swirl, with spiral
arms spinning away from the center. You're seeing face-on a galaxy much like our
own Milky Way, though this spiral appears to be the result of a collision with a
smaller galaxy. Starting again at Alkaid, you'll see Mizar in the middle of the
"handle" about 6 degrees to the left. Imagine an inverted triangle with
these two stars at the top. At the bottom point lies another grand-design spiral
galaxy, this one known as M 101 - the "Pinwheel Galaxy." No sign of a
colliding companion here.
Jupiter is in the constellation Leo, about 10 degrees from Regulus at mid-month.
On a moonless, clear night you'll also find a number of galaxies within about 5
degrees of Jupiter. Imagine the line from Regulus to Jupiter, and move up at right
angles slowly with your binoculars. In about 3 degrees you'll encounter M 105, a
giant elliptical galaxy, showing no spiral structure.
To the south, about 40 degrees off the horizon, is Spica, the bright star in Virgo.
Higher and to the southeast you should find Arcturus, in the constellation Bootes.
Castor and Pollux are to the west-northwest, above Mars and Saturn. We bid them
farewell until lat fall, when they will reappear to the east. The plane of the Milky
Way nearly rings the horizon a few hours after sunset, crossing the plane of the
ecliptic near Venus.
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.