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Turbulent cloud

Photo of the Week. A turbulent cloud coils across the sky; see another view.

Astronomy news for the week starting Friday, November 3, 2006.

The Moon begins the week in its late waxing gibbous stage as it heads toward full on the morning of Sunday, November 5, just about the time of Moonset, which takes place almost exactly at sunrise. A day before full, it passes perigee, where it is closest to the Earth, giving us slightly more full Moonlight than average. The Moon will thence wane in the gibbous phase over the rest of the week, sadly not visiting any of the planets, though it will make a fine sight as it plows through Taurus the nights of Monday the 6th (east of the Pleiades) and Tuesday the 7th.

What we do have is an excellent and rather rare visit between Mercury and the Sun. On Wednesday, November 8, the planet passes inferior conjunction with the Sun, where it is in between the Sun and us. Because of the tilt of the planetary orbit, Mercury is usually not QUITE aligned, but passes either above or below the solar disk. This time, however, the planet passes right across the Sun for a " transit." Transit seasons are early November and May. November events are separated by intervals of 7 or 14 years. May transits (which take place with the planet farther from the Sun) are rarer, and can, but don't have to, recur in 14 years. (Transits of Venus are far rarer. There were none in the twentieth century; the last one was in 2004, the next in 2012.) Transits of Mercury are NOT visible to the naked eye, even with appropriate filters, but are readily visible with the telescope. However, they should be viewed by projection only; do not even try without professional- level knowledge or help. The event begins at 1:12 PM CST (2:12 EST, 12:12 MST, 11:12 AM PST, 9:12 AM Hawaii), and lasts for about 5 hours as the planet slowly moves in orbit. Only the western US and Canada will witness the whole thing before sunset. The timings of such transits were once used in attempts to establish local times and thus longitudes.

Watch the transit in real time.

The only other bright planet visible to us now (the others lost in twilight) is Saturn, which makes a transition to evening this week, rising at or just before midnight local time. By dawn it is high in the southeast to the west of Regulus in Leo.

As autumn and evening roll on, we see more of the great constellations of the Perseus myth. Well to the north are the "W" of Cassiopeia and the star-streams of Perseus, while well to the south are the fainter stars of the villain of the story, Cetus, the Whale or Sea Monster, his tail now crossing the meridian around 10 PM marked by rather bright Deneb Kaitos, his circular head crossing two hours later. In the middle lies the prototype of the long-period Mira variables, Mira itself.
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