Astronomy news for the week starting Friday, May 18, 2001.

Our Moon passes through its new phase this week on Tuesday, the 22nd. Watch as the waning morning crescent, seen in eastern dawn, thins early in the week and then appears on the other side of the Sun to the west the evening of Thursday, the 24th. The morning of Saturday the 19th, the Moon will appear a few degrees to the south of brilliant Venus.

Saturn is now gone, lost to evening twilight, and Jupiter, just a little behind, is quite difficult to find, as it now sets just a bit over an hour after the Sun. The evening sky does present us with a fine apparition of Mercury, however. Only a day before the Moon passes new (on Monday the 21st), the little planet, the one closest to the Sun, passes its greatest eastern elongation, when it is 22 degrees to the east of the Sun and maximally visible. For those in North America, the Moon will provide a fine guide, as the lunar crescent will be just a few degrees to the right of the planet the night of Thursday, the 24th. Look in bright twilight and follow the Moon as it sets and the sky darkens to see Mercury emerge from the fading glow. The planet remains mysterious. Of the nine planets, only Pluto is smaller. Not quite 40 percent the size of Earth, Mercury has the largest iron core relative to its size of any of them. Dangerously close to the Sun, it has been visited by but one spacecraft (Mariner 10 passing it 3 times in 1974 and 1975), and only about half has been imaged. So close in angle to the Sun that it is visible only in the daytime or in twilight, surface features are nearly impossible to see from Earth.

Once Mercury sets, the evening sky awaits the rising of Mars, which climbs above the southwestern horizon around 10:30 PM Daylight Time. Now moving retrograde in far western Sagittarius, the red planet, fourth from the Sun, and the last of the "terrestrial planets" (those constructed like Earth), will be rising in evening twilight by the end of the month.

In the early evening, for those in mid-northern latitudes, look out perpendicular to the plane of our Galaxy. The Milky Way is about as absent as it can get, and lies around the horizon where it is invisible. Our view is unobstructed by the dust in the Galactic plane, allowing us to see outward as far as our instruments will carry us, to distant galaxies billions of light years away. From the southern hemisphere, however, the Milky Circle is high and spectacular as it passes through Centaurus and Crux, the Southern Cross.
Valid HTML 4.0!