****************************************************** Abrams Planetarium SKYWATCHER'S DIARY March 1997 ****************************************************** The Skywatcher's Diary for March 1997 has been prepared by Robert C. Victor. Credit to Abrams Planetarium, Department of Physics and Astronomy at Michigan State University, together with mention of our Sky Calendar, would be appreciated. A sample current issue of Sky Calendar is available over the Internet. It can be viewed via a World-Wide Web browser such as Netscape or Mosaic, directly at URL: http://www.pa.msu.edu/abrams/apr97skycal.html If you would like a printed sample of the March issue, send a long, self- addressed stamped envelope to: March Sky Calendar Abrams Planetarium Michigan State University East Lansing, MI 48824 Each month, the Department of Physics and Astronomy at Michigan State University also makes Skywatcher's Diary available over the Internet. It can be accessed via a World-Wide Web browser such as Netscape or Mosaic, directly at URL: http://www.pa.msu.edu/abrams/diary.html The Skywatcher's Diary is also available via anonymous ftp at: www.pa.msu.edu in the directory /pub/swd ****************************************************** Comet Hale-Bopp in March 1997 Comet Hale-Bopp in morning sky: In NE to lower left of the Summer Triangle 1-1/2 hours before sunrise, Comet Hale-Bopp already shines at zero magnitude in second week of March and is expected to brighten further. During March 7-20, there is no Moon in sky at all during comet's prime predawn viewing time. Comet Hale-Bopp in evening sky: On Feb. 23 the comet was spotted from mid-Michigan just above NW horizon for the first time in *evening* twilight. The comet becomes easier, climbing 5 degrees up in NW at nightfall by March 8 for observers at latitude 40 degrees north, and a week later as seen from latitude 30 degrees north. As the Moon brightens toward Full on March 23, viewing of the comet's faint extended tail will be compromised, but the compact bright head of the comet will remain in view. Dark moonless evenings, ideal for comet viewing, will return March 25 or 26, when the Moon rises after nightfall. Best dates for viewing the comet right at nightfall, with Moon absent, will be March 26-April 7. Nearly as good will be April 8-13, with the Moon only a crescent. By a happy coincidence for most of U.S., the comet reaches its peak altitude about 20-25 degrees up in NW to WNW at nightfall in first or second week of April. For more information, try some of our favorite Hale-Bopp Web sites: http://encke.jpl.nasa.gov/ http://newproducts.jpl.nasa.gov/comet/ http://medicine.wustl.edu/~kronkg/1995_O1.html http://cfa-www.harvard.edu/cfa/ps/HaleBopp.html http://www.skypub.com/comets/comets.shtml Our own H-B visibility site: http://www.pa.msu.edu/abrams/hbvis.html Obtain Comet Hale-Bopp positions at dawn's first light and at nightfall for your own location, calculated by the US Naval Observatory: http://aa.usno.navy.mil/AA/data/docs/HaleBoppProg.html To enhance your enjoyment of Comet Hale-Bopp, we recommend these engaging and very readable books: Comet of the Century: from Halley to Hale-Bopp, by Fred Schaaf, and Everybody's Comet: A Layman's Guide to Comet Hale-Bopp, by Alan Hale. For reviews of these and other books on Comet H-B, see February Sky & Telescope magazine or point your Web browser to: http://www.skypub.com/comets/hb10.html ****************************************************** March 1997 Highlights: What a month for skywatchers! Just after midmonth, Mars is brighter and closer than it will be again until April 1999; a deep partial lunar eclipse is visible throughout the U.S. on Sunday evening, March 23; and Comet Hale-Bopp moves into the evening sky, passes closest to Earth on March 22, closest to Sun on March 31, and attains greatest brilliance, very likely sometime between those dates. Keep in mind predictions of a comet's performance are very uncertain, but as of the end of February 1997, Comet Hale-Bopp already exceeds first magnitude in NE morning sky and seems very likely to shine brighter than zero magnitude in late March and early April. Comet experts believe that H-B will not disappoint anyone who arranges to see it in a clear dark sky. Late in March, the comet's tail, seen from dark sites, may grow to over 25 degrees long! ********* SKYWATCHER'S DIARY: MARCH 1997 ********* Saturday, March 1 On Sunday 1-1/2 hours before sunrise, before dawn brightens, the Last Quarter Moon is in SSE with first-magnitude Antares 9 degrees to its lower right. The Moon is half full, only one-tenth as bright as the Full Moon a week ago, so there is much less scattered moonlight in the sky to spoil viewing of Comet Hale-Bopp. By March 6, the Moon will be a thin crescent just rising at this hour, and from March 7 to 20, if you're far from man-made light sources, skies will be dark and moonless, ideal for viewing the exquisite tail of the comet. On Sunday morning, Comet Hale-Bopp is in ENE 14 degrees lower right of Deneb. The comet is 136 million miles from Earth, 98 million miles from Sun. These distances will close to 122 million miles from Earth on March 22, and 85 million miles from Sun on March 31, respectively. March through May issues of the Abrams Planetarium Sky Calendar feature dayboxes and evening star charts to help you enjoy following the progress of the comet. A subscription may be ordered for $9.00 per year, from Abrams Planetarium, Michigan State University, East Lansing, MI 48824. The March and April issues are now available. Sunday, March 2 Comet Hale-Bopp remains better placed in the morning sky through March 20. But beginning this week it will be seen increasingly in the evening by skywatchers in northern U.S. Look very low in NW within an hour after sunset. Observers in southern U.S.may have to wait another week or two. Monday, March 3 In the predawn hours of Tuesday, Comet Hale Bopp passes 97 million miles almost directly "above" the Sun, meaning that a line from Sun to Comet is most nearly perpendicular to the Earth's orbital plane on Tuesday morning. This can happen for Comet Hale-Bopp because the inclination of its orbit to Earth's orbital plane is 89.4 degrees. An observer on the Sun would see Hale-Bopp in the constellation Draco only 0.6 degree from the North Ecliptic Pole (pole of Earth's orbital plane). From here on Earth, we see H-B in the ENE, 15 degrees below Deneb, in predawn darkness hours. In late February 1996, for the first time since its last visit to the inner solar system 42 centuries ago, Comet Hale-Bopp crossed "above" or north of the Earth's orbital plane. Just over 14 months later, on May 6, 1997, Comet Hale-Bopp will cross back "below" or south of Earth's orbital plane, where it will remain until its next visit to the inner solar system 24 centuries from now. Tuesday, March 4 At dawn's first light on Wednesday, about 1-1/2 hours before sunrise, Comet Hale-Bopp is in ENE, 15 degrees below the first-magnitude star Deneb. Does the tail reach that far? The comet is 133 million miles from Earth and 96 million miles from Sun. Both those distance will decrease by 11 million miles later this month, on March 22 and 31, respectively. An hour before sunup on Wednesday, the crescent Moon is in SE, with Jupiter 15 degrees to its lower left. Bright Mars, nearly 64 million miles distant from Earth, is in WSW to W. Wednesday, March 5 From now through March 20, Comet Hale-Bopp is best enjoyed about 1-1/2 hours before sunrise, before dawn's first light brightens the sky. Look for the Summer Triangle well up in the eastern sky. Its brightest star, blue-white zero-magnitude Vega, is very high in east. Altair, of mag. +0.8, is in ESE 34 degrees lower right of Vega. Deneb, of mag. +1.3, is in ENE 24 degrees lower left of Vega. On Thursday morning Comet Hale-Bopp is 16 degrees below Deneb. Compare the comet's brightness to the three stars of the Summer Triangle. Just 1-1/4 hours before sunrise on Thursday, face ESE to see Jupiter rising 3 or 4 degrees to lower right of the waning crescent Moon. Thursday, March 6 One-and-a-half hours before sunup on Friday, Comet Hale-Bopp is in ENE to NE, 17 degrees below the first-magnitude star Deneb and nearly halfway from Deneb toward the 2.4-magnitude star Beta in Pegasus. The comet is bright enough so you won't need the stars to find it, but you can use the starry backdrop to follow the comet's changing position day-to- day. From March 7-12, it's shifting by about 1.6 degrees per day. Forty-five minutes before sunrise on Friday, the thin old crescent Moon is very low ESE, 15 degrees lower left of Jupiter. In Michigan the Moon will be about 38 hours before New. Friday, March 7 Have you seen Comet Hale-Bopp in the evening yet? About an hour after sunset, as sky darkens, look very low in NW, 28 degrees below the lower end star of the "W" of Cassiopeia. Although the comet's evening position is improving, getting nearly a degree higher daily, it remains higher and more impressive in the morning sky through March 20. Saturday, March 8 The Moon is New today at 8:15 p.m. EDT, and not visible. A total solar eclipse is visible from northern Mongolia and eastern Siberia, where the local date is March 9. Comet Hale-Bopp is bright enough to view with unaided eye during totality. By a happy coincidence, the comet appears farthest from the Sun, 46 degrees. You don't need to travel to Asia to attempt a daytime view of Comet Hale-Bopp. On the next morning when skies are very clear, locate the comet before sunrise and use a telescope to track it until after the Sun rises. Send your reports to comets@skypub.com. Sunday, March 9 Look for the young crescent Moon very low, just south of due west, within half an hour after sunset. The Moon's age, or time elapsed since conjunction with Sun (New Moon), is less than 23 hours from the eastern U.S. As the sky darkens, can you find Saturn 5 or 6 degrees to Moon's upper left? On Monday about 1-1/2 hours before sunrise, look for Comet Hale- Bopp gleaming in the northeast, 19 degrees lower left of first-magnitude Deneb and 25 degrees right of the "W" of Cassiopeia. Monday, March 10 Low in west about 45 minutes after sunset, look for Saturn about 9 degrees to the lower right of the beautiful 2-day-old crescent Moon.Owing to Earth's faster orbital motion around the Sun, Saturn appears lower each evening and will disappear around week's end. Saturn will be in conjunction, beyond the Sun, on March 30. An hour after sunset, Comet Hale-Bopp is very low in NW, 24 degrees below the ""W" of Cassiopeia and 23 degrees lower right of 2nd- magnitude Alpha in Andromeda. The comet is better seen in the morning: One-and-a-half hours before sunup on Tuesday, look in NE, 21 degrees lower left of Deneb and 24 degrees right of the "W" of Cassiopeia. Tuesday, March 11 Today Mercury is in superior conjunction, beyond the Sun. Within 10 days you can start seeing this planet very low, just north of west, about half an hour after sunset. Mercury will be in fine view in evening twilight in the last week of March and first 10 days of April. An hour after sunset this evening, the variable star Mira appears 13 degrees to the Moon's lower left. Comet Hale-Bopp then appears very low in NW, 23 degrees below the "W" of Cassiopeia. One-and-a-half hours before sunrise on Wednesday, Comet Hale-Bopp puts on a fine display in NE. Look 22 degrees lower left of Deneb and 22 degrees right of the "W" of Cassiopeia. See illustration at following url. (Credit to Abrams Planetarium, Michigan State University, would be appreciated.) http://www.pa.msu.edu/abrams/97mar12.html Wednesday, March 12 Tonight Comet Hale-Bopp is within 126 million miles from Earth, 91 million miles from Sun. Look for the comet within an hour after sunset, very low in NW. [As seen from south of lat. 30 degrees N -- Florida, Texas, and Hawaii, the comet still sets before nightfall, but will improve in coming nights.] Through March 20th, Comet Hale-Bopp is seen higher and better in the NE morning sky, at dawn's first light, about 1/1/2 hours before sunrise. Thursday, March 13 Reddish Aldebaran is upper left of the fat crescent Moon at dusk, while like-colored Mars gleams in the east. Tonight is the summer solstice in Mars' N hemisphere. The N polar cap of Mars is shrinking rapidly. Friday, March 14 Aldebaran is closely lower right of the Moon at dusk. Check with your local planetarium or astronomy club to see when they'll start public observing sessions to see Comet Hale-Bopp. Locally, a good place to view the comet tonight and Saturday would be from the top of the parking ramp behind Abrams Planetarium from 7:30 p.m. until the 8:00 p.m. showing of Comet: From Ice to Fire. Look very low in NW as twilight deepens. Saturday, March 15 Betelgeuse, shoulder of Orion, is to the lower left of the Moon at dusk. The two stars to Moon's upper right are the tips of the horns of Taurus, the Bull. To make sure you've got the right stars, a line connecting them extended to lower left points directly to Betelgeuse. For the next two weeks, Comet Hale-Bopp moves about 1-3/4 (one and three-quarters) degrees each day against the stars. Sunday, March 16 The gibbous (more than half full) Moon continues brightening each night until it's full a week from tonight. Comet Hale-Bopp is so bright that at least its head and bright inner tail will remain visible, even when the sky is flooded by full moonlight. Look low in NW at dusk. From now through Thursday, the best view of the comet remains in the dark moonless predawn. Look NE 1-1/2 hours before sunrise. Monday, March 17 Today, Sun-Earth-Mars are arranged, in that order, in a straight line in space. All night long, you can find bright reddish Mars at opposition to the Sun, low in east at dusk, high in south in the middle of the night, and low in west at dawn. Tuesday, March 18 In order of brightness at dusk are: Moon in ESE; Sirius in S; Mars in E; and Comet Hale-Bopp in NW. In the morning sky 1-1/2 hours before sunup, Comet Hale-Bopp in NE ranks second in brilliance after only Jupiter in SE. The Moon will join the scene on Friday morning, taking over first place in brightness. Wednesday, March 19 From now through Monday, Comet Hale-Bopp moves at its fastest among the stars, just over 1-3/4 degrees per day. That's because the comet will be at its closest to Earth this weekend. Thursday, March 20 Spring begins for Earth's northern hemisphere today at 8:55 a.m. EST. Mars is closest to Earth today. The red planet's distance from Earth is 61 million miles. Not until April 1999 will Mars be closer. Look for Mars in E at dusk . Comet Hale-Bopp tonight is twice as far away from us as Mars is. Compare their apparent sizes in the sky, and draw a conclusion about the actual size of Comet Hale-Bopp. Friday, March 21 From far northern U.S. Comet Hale-Bopp is up all night. Today it's equally high in morning and evening. For example, from lower Michigan, the comet is 18 degrees up in NE 1-1/4 hours before sunrise, and 18 degrees up in NW 1-1/4 hours after sunset. With each passing day, the comet sinks lower in NE morning sky, and ascends higher in NW evening sky. Best evening viewing starts March 26 when Moon rises after nightfall, and continues through April 13. With comet at its closest to Earth on March 22 and closest to Sun on March 31, it should be near peak brilliance in late March and early April. Saturday, March 22 Comet Hale-Bopp, at a distance of 122 million miles, is nearest to Earth today. Face NW at dusk and NE at dawn. By Wednesday the Moon will rise late enough to allow good comet viewing at nightfall. Have you ever seen surface details on Mars? Through a telescope, Syrtis Major, most prominent of Mars' dark markings, crosses center of disk at 7:30 p.m. EST tonight, and then 36 minutes later each night. Choose nights when Mars is high in the sky at these times, and see if you can observe that feature. Sunday, March 23 Here are times for tonight's lunar eclipse, which is expected to be very colorful (convert to your time zone): Moon enters umbra (dark central core of Earth's shadow) at 9:57 p.m. EST. Moon moves halfway into umbra at 10:37 p.m. Deepest eclipse occurs 11:39 p.m., as the shadow reaches 92 percent of the way across the Moon. The reddened Moon with its bright sunlit northern "cap" may then resemble a closeup view of Mars. The Moon is halfway out of the umbra at 12:42 a.m., and completely leaves the umbra at 1:21 a.m. EST early Monday morning. See the diagram on the Abrams Planetarium Sky Calendar at: http://www.pa.msu.edu/abrams/97eclipse.html At the time of deepest eclipse (and darkest skies of the night), Comet Hale-Bopp will touch horizon as seen along line from Halifax, Toronto, Detroit, Chicago, Albuquerque, to Phoenix. Seen from north and west of that line, comet will be higher, as high as 17 degrees up from Seattle. From south of that line, where comet's head will be below horizon, will any skywatchers notice the comet's tail poking above the horizon at mid- eclipse? Monday, March 24 Two hours after sunset, watch for Spica rising below the Moon. Tuesday, March 25 Tonight 1-1/4 hours after sunset, before the Moon rises and brightens the sky, look in NW for Comet Hale-Bopp. Binoculars give a fine view. Note Andromeda Galaxy 5 degrees lowr left of the comet. See illustration at: http://www.pa.msu.edu/abrams/97mar25.html Two hours after sunset the rising Moon is within a few degrees lower left of Spica. Wednesday, March 26 There's at least an hour of good comet viewing between nightfall and moonrise. Look in NW as sky darkens. For more on the visibility of Comet Hale-Bopp with links to other sites, point your Web browser to: http://www.pa.msu.edu/abrams/hbvis.html Thursday, March 27 In order of brightness at dusk: Sirius in S to SSW; Mars in E to ESE; Mercury very low just N of W; and Comet Hale-Bopp in NW. Friday, March 28 An hour before sunup on Saturday look for reddish first-magnitude Antares, heart of the Scorpion, 9 degrees below the Moon. Saturday, March 29 Tonight through April 10 Mercury is at its best in the evening sky for this year. The planet will shine at first magnitude or brighter and be 7 to 10 degrees up in W to WNW in mid-twilight, about 45 minutes after sunset. Sunday, March 30 Today Saturn is in conjunction, invisible on far side of Sun. At nightfall, look for Comet H-B in NW. Note 2nd mag star Gamma Andromedae 5 degrees to comet's upper left. On Wednesday, April 2, comet will pass within 1.5 degrees above this star, forming a sort of exclamation point! Look nightly and watch for changes in the position of the comet. Monday, March 31 Tonight at 10:14 p.m. EST, Comet Hale-Bopp reaches perihelion (closest to Sun) at a distance of 85 million miles from Sun. Comet H-B reaches its maximum orbital speed of 44 kilometers per second, or 198,500 miles per hour. Light from the Sun takes 7.6 minutes to reach the comet. Around 103 BC when the comet was at aphelion (farthest from Sun), it was nearly 570 times farther from the Sun, and sunlight took 3 days to reach the comet! Its orbital speed was then a "leisurely" 77 meters per second, or 173 miles per hour. Enjoy the comet in NW to WNW at nightfall for next 6 weeks. If you miss it this time, you have a long while to wait! Its next pass through the inner solar system will come around the year 4375 AD. ******** end of Skywatcher's Diary for March 1997 ********