December Skies from Keeble Observatory.

December was supposed to be a busy month for space exploration. On the 3^rd, if all had gone as planned, the Mars Polar Lander was to touch down on the edge of the southern polar cap of the Red Planet. This was programmed as a soft landing – slowed by retro-rockets, rather than the air-bag cushioned "bounce and roll" of Mars Pathfinder. At the same time, two penetrator probes, dubbed "Deep Space Two" were to slam into the surface and hopefully stop several meters into the ice. These instruments should tell us a great deal about the nature and history of the ice. Are we correct in our belief that it’s water ice, or it frozen carbon dioxide, or some combination of the two? Is it uniform in composition, or are we correct in our expectation that it contains alternate layers of ice and dust laid down over the millennia? As of this writing (1999 December 6) no signals have been received from any of these probes.

Hubble Space Telescope is currently operating in "safe mode" – with the cover closed and no observations being made. The telescope requires a minimum of three out of six gyroscopes to be operating in order to safely control and point the instrument. Four of the six have now failed. A much-delayed repair mission is scheduled for launch on the 11^th, though the date has already slipped several times since its original target date in October. There have been continuing problems with worn insulation on electrical wiring, which has grounded the entire shuttle fleet since the last flight of Columbia last summer. There have also been problems with weather, and with one of the main engines. A possible late-November launch was delayed to avoid the Leonid meteor shower (which was a "bust" for our part of the world, but quite spectacular in Europe and northern Africa). Some in NASA are also expressing concern about the flight software, which may not be fully Y2K compliant – so they are nervous about launching too late in the month. We’ll update you in next month’s column.

Lunar phases for December: New Moon on the 7^th at 5:32 pm; First Quarter on the 15^th at 7:50 pm; Full Moon on the 22^nd at 12:31 pm; Last Quarter on the 29^th at 9:04 am.

Mars, Jupiter, and Saturn are all visible as the Sun sets – Mars is low to the southwest, with Jupiter and Saturn getting closer together in the southeast. Venus and Mercury are both visible at sunrise, with Venus high above the eastern horizon, Mercury very low and harder to see.

An overhead look at mid-month finds the Andromeda Galaxy almost directly above – it’s difficult to crane your neck that far back, but with a comfortable deck chair and some binoculars it is not hard to find. About halfway between the northern "W" shape of Casseiopeia, and the large almost empty Great Square of Pegassus you’ll find a faint smudge of light. This spiral galaxy, very similar to our own Milky Way, yet some 2 million light years distant is the most distant object visible to the unaided eye. The Moon, by contrast, is a mere light second away. The galaxy is best observed early in the month or near the end, so that glare from the Moon is not a problem. To the northwest and west we see the bright stars Vega, Deneb, and Altair. Cygnus is now more easily identified as the Northern Cross than a swan. To the east we can see the ascension of Orion, easily identified by the three bright stars in the belt of the Hunter, with the red giant Betelgeuse on one shoulder, and the blue-white Bellatrix on the other. Below the belt we find the Orion Nebula, a relatively nearby (about 1500 light years) star-forming region – well worth a look with binoculars or a small telescope. Just to the northeast we find Castor and Pollux rising in the constellation Gemini. Above Orion, in the constellation Taurus, we find the Pleiades cluster. This relatively young (10 million years or so) cluster lies about 400 light years from our Sun. The Milky Way traces a broad, luminous path from the southeast to the northwest.