Astronomy news for the week starting Friday, April 16, 1999.

Having just passed its new phase the night of Thursday, April 15, the Moon will be readily visible in western twilight by the night of Saturday, the 17th (just after it has passed perigee, its closest point to the Earth) and will spend nearly the whole week as a waxing crescent, reaching first quarter on Thursday, the 22nd, just about moonrise in North America. The night of Saturday the 17th will present us with a spectacular sight, a combination of the Moon appearing several degrees to the left of brilliant Venus and the Pleiades, while at the same time occulting the bright star Aldebaran in Taurus for much of western North America, the best view from the Rockies, Pacific Northwest, and central and western Canada. From the midwest the first magnitude orange star will appear to hang beautifully in front of and above the crescent, the occultation occurring very low in the sky just before moonset, while from the east the event takes place after moonset. Whether you can see the occultation or not, the sight will be well worth a look.

As the Moon leaves the planet's vicinity, Venus continues both to brighten and to set later, and is brilliantly visible in a fully dark western sky well after twilight. The two great planets of the Solar System, Jupiter and Saturn, are both too close to the Sun to be seen, but over in the east, bright Mars rises just after sunset. In the morning hours, Venus's companion Mercury passes through its greatest western elongation on Friday the 16th, when it is as far to the west of the Sun as it can get, the apparition unfortunately not very good as the ecliptic (the apparent solar path) lies flat to the horizon and the planet will be low in morning twilight.

In the evening, however, the ecliptic rises from the horizon at a steep angle, allowing for fine viewing of the "zodiacal light," a faint luminous band that runs through the constellations of the zodiac caused by sunlight scattering from interplanetary dust particles that come from comets and the debris of smashed asteroids. To see the zodiacal light you need a very dark moonless sky (which we will have early in the week) away from city lights. After the end of twilight, the zodiacal light then rises like a great cone from the horizon. Northern autumn affords the best morning view, the delicate light sometimes called the "false dawn."

Finally, if out in the early morning, watch for the Lyrid meteor shower, which peaks the morning of Wednesday, the 21st, the shower typically yielding 10 or so meteors per hour before dawn.
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