Comet Hale-Bopp Update

HALE-BOPP'S SPRING SPECTACLE

Sky & Telescope News Bulletin
March 28, 1997

Without doubt, Hale-Bopp (C/1995 O1) is an obvious sight in the evening sky for any viewer in the Northern Hemisphere. On April 1st it comes closest to the Sun, a point 137 million km (0.91 a.u.) away, while moving 44 km per second. The comet's coma has brightened to better than magnitude -0.5, and its pearly dust tail is much more evident now that moonlight is no longer in competition. Although Hale- Bopp can still be seen before dawn, it's really at its best in the evening sky. The comet's starlike inner coma can even be seen in twilight. But the tail, which points to the right, is most obvious at least 1-1/4 hours after sunset when the sky has become completely dark. Look about 20 degrees above the northwestern horizon.

Comet Hale-Bopp drew worldwide attention unexpectedly last week when a group in California committed mass suicide. Apparently its members believed the comet was a long-awaited "marker" signalling them into action. Historians note that comets have been associated with death, disease, and other calamities for thousands of years. Several such episodes are chronicled in "Comets That Changed the World," an article by astronomer Bradley E. Schaefer in SKY & TELESCOPE's May issue.

HALE-BOPP COMPOSITION CLUES

Astronomers have been using orbiting observatories to divine the comet's composition, and several results were reported this week. The March 28th issue of SCIENCE describes studies made with the Hubble Space Telescope and the International Ultraviolet Explorer. That work shows that water ice is escaping at a rate different from those of other frozen compounds, so these ices appear to be segregated from one another within the nucleus. Spectra obtained with Europe's Infrared Space Observatory show that Hale-Bopp's coma contains particles of olivine, a metal-rich silicate mineral common in Earth's mantle and in the dust cocoons that surround other stars.

MARCH 30 -- SUNDAY

Comet Hale-Bopp is at its best now and for the next two weeks! Look for it fairly low in the northwestern sky right after the end of twilight -- a bright, fuzzy "star" with a tail. The comet is glowing at about magnitude -1, as bright as the very brightest stars.

Any light pollution in your sky will diminish what you can see of the comet's tail. But its head is bright enough to show even through bad city light pollution. Binoculars will give a grand view under any conditions. A good amateur telescope shows a wealth of bright detail -- arcs and jets -- around the comet's nucleus. Don't miss this rare event!

The farther north you are, the higher the comet will appear. Observers in the Southern Hemisphere miss out until late April or May.

APRIL 1 -- TUESDAY

Comet Hale-Bopp is at perihelion, 85 million miles from the Sun.

APRIL 2 -- WEDNESDAY

Just below the head of Comet Hale-Bopp this evening and tomorrow evening is the 2nd-magnitude star Gamma Andromedae.

APRIL 3 -- THURSDAY

Mercury and Hale-Bopp are shining at about the same apparent magnitude, -0.3. Mercury is in the midst of its best evening apparition of the year; look for it about an hour after sunset, low in the west-northwest. The comet is off to Mercury's upper right. Its tail is best seen a bit later as the sky grows fully dark.

APRIL 5 -- SATURDAY

The eclipsing variable star Algol, a little to the upper left of Comet Hale-Bopp's head, should be at minimum light, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 10:14 p.m. Eastern Standard Time (convert this to your time zone). Algol takes several additional hours to fade and rebrighten.

Copyright 1997 Sky Publishing Corporation. S&T's Weekly News Bulletin is provided as a service to the astronomical community by the editors of SKY & TELESCOPE magazine. Widespread electronic distribution is encouraged as long as this paragraph is included. But the text of the bulletin and calendar may not be published in any other form without permission from Sky Publishing (contact permissions@skypub.com). S&T's Weekly News Bulletin and "Sky at a Glance" are available via SKY Online on the World Wide Web (http://www.skypub.com/). At present they are not available via electronic mailing list. Comet Hale-Bopp Home Page