Astronomy news for the week starting Friday, June 23, 2000.

The Moon runs through its last quarter early in the week, on Saturday the 24th, around the time of sunset in North America, rather well before the Moon rises to be seen. The remainder of the week sees an ever-diminishing crescent that on the mornings of Wednesday the 28th and Thursday the 29th will make lovely configurations with Saturn and Jupiter, which are now rising nicely out of dawn's light. On Wednesday morning, the Moon will directly to the right of Saturn, while the next morning it will have fallen to down and a bit to the left of much brighter Jupiter and directly below the Pleiades of Taurus.

The only planets now around for viewing are four big ones in the outer Solar System, plus, if you have a large telescope, little Pluto. The two largest, Jupiter and Saturn, have recently moved into Taurus, which is now clearing the morning Sun. The more distant two, which are considerably smaller than Jupiter and Saturn and have quite different colors and constructions, are paired in Capricornus. The three terrestrial planets (discounting Earth, which we can see quite nicely) are all bunched near the Sun and are effectively invisible.

Even in these times of great scientific advances, Mercury is still notoriously difficult to study. Because of its proximity to the Sun, it can only be seen only in daylight or in twilight (and then only low in the sky through the murk of the Earth's atmosphere). Surface features have been nearly impossible to see. Nearly all we know about the planet has come from observations by radar and from imaging by the Mariner 10 spacecraft in 1974-75. The little planet has made the news by finally being observed effectively from the ground using the combination of a very large number of extremely short exposures taken with a high-quality video camera. These new observations show a part of Mercury never before observed with any detail and a possible large impact basin.

'Tis the season for the bright orange star Arcturus, which is now crossing the meridian to the south around 9 PM. If your sky is dark, look to the left of Arcturus for a faint "X" of stars, which represents the head of Serpens, the Serpent, the great snake that is wrapped around the body of Ophiuchus, the Serpent Bearer (and which now contains Pluto). Serpens is the only constellation in the sky that is broken into two parts, one for the head (Serpens Caput), one for the tail (Serpens Cauda), the two separated by Ophiuchus, the only constellation through which the Sun passes that is NOT in the classical Zodiac.
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