November 2002 Sky from the Keeble Observatory
Pluto, the embattled 9th planet, has more company. Recall that Pluto is the most
recently discovered of the nine planets, and that many astronomers would like to
downgrade its status. It doesn't fit the pattern of the outer solar system; it's
not a gas giant like Jupiter. Rather, it seems most closely to resemble the icy
moons found orbiting those gas giants. Triton, one of Neptune's moons imaged by
Voyager 2, is probably a close twin.
Yet, the nostalgic impulse says to let Pluto be considered a planet. It was discovered
72 years ago by Clyde Tombaugh, who was actually looking for a planet precisely
where he found Pluto. Of course, he was looking there because of a faulty calculation,
and Pluto is not anything like what he expected.
We now understand that there is a reservoir of short-period comets, nearly in the
plane of the ecliptic and lying at distances beyond that of Neptune. This so-called
Kuiper Belt was formed when the solar system was very young, as gravitational interactions
with Uranus and Neptune threw many planetesimals into orbits at distances comparable
to Pluto's current orbit. Similar gravitational slingshot events interacting with
Jupiter and Saturn are responsible for the larger, spherical reservoir of long-period
comets, known as the Oort Cloud.
Once only the stuff of theory, with the capabilities provided by Hubble Space Telescope,
the Kuiper Belt has been observed - or, at least, sampled. About 500 objects are
now identified. The largest denizen of the belt thus far is about half the diameter
of Pluto. Its official designation thus far is 2002 LM60. Its discoverers wish to
name it Quaoar (pronounced kwa-war) after a southern California native American
creation deity. Quaoar is about 800 miles in diameter, and is likely composed of
the same mix of ice and rock that we estimate for Pluto and Triton. It's actually
not dissimilar from the composition of comets. Another, known as Varuna, is almost
550 miles in diameter.
Maybe it's time we shift Pluto's designation from planet to Kuiper Belt Object and
let it be the largest known to date.
Lunar phases for November: New Moon at 3:34 pm EST on the 4th; First Quarter at
3:52 pm on the 11th; Full Moon on the 19th at 8:34 pm; Last quarter on the 27th
at 10:46 am.
Early evening planet watchers can take the month off! Saturn rises at least 3 hours
after sunset, Jupiter about an hour later. In the pre-dawn you'll be able to find
both of them; Jupiter is high to the SSE early in the month, moving to southwest
by the end of the month. Saturn is high to the WSW, moving towards the west by month's
end. Mars is visible low to the ESE.
The Leonid meteor shower should display two distinct peaks, one at about 11:00 pm
on the 18th, the second on the 19th at about 5:30 am. The first is the debris train
from the 1767 apparition of Comet Tempel-Tuttle, the second from its 1866 pass through
the inner solar system. Unfortunately, you'll be contending with a nearly-full moon,
so only the brightest meteors will be visible. For an update on the meteor shower,
check the web site of the International Meteor Organization at
An overhead view at mid-month finds the Andromeda Galaxy almost at zenith, with
little competition from a waxing crescent moon until about the 18th or 19th. To
find it, try averted vision so that the more sensitive part of your retina can see
the faint smudge light. This galaxy is similar in size and structure to our own
Milky Way, but it lies at a distance of 2 million light years. As such, it is the
most distant object which is directly visible without a telescope. The plane of
our own Galaxy makes an arc slightly north of zenith, crossing the horizon at east
and west. To the west Cygnus now shows itself as the Northern Cross, with the upright
marking the plane of the Milky Way. Deneb is the bright star at the top, the binary
Albireo marks the cross's base. To the east we see bright Capella in the constellation
Aurigae. Just clearing the horizon at this time we see Castor and Pollux in Gemini,
and the distinctive shape of Orion. These constellations will become more prominent
into the winter months.
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.