****************************************************** Abrams Planetarium SKYWATCHER'S DIARY April 1996 (with info on Comet Hyakutake and lunar eclipse of April 3) ****************************************************** The Skywatcher's Diary for April 1996 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 Sky Calendar for May 1996 is available over the Internet. It can be viewed via a World-Wide Web browser such at Netscape or Mosiac, directly at URL: http://www.pa.msu.edu/abrams/may96skycal.html If you are hosting events for National Astronomy Day, Saturday, April 20, or other astronomy activities during this month, we encourage you to reprint and distribute the May Sky Calendar without charge to your participants. For a reprintable copy, send a long, self-addressed stamped envelope to: May 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 Mosiac, 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 ******* Lunar and Planetary Highlights for April ******* Don't miss the lunar eclipse on Wednesday, April 3 (unless you're too far west to see it). Details below. At dusk in April, brilliant Venus is well up in W to NW at dusk, and sets four hours after sundown early in month. This early spring appearance of Venus, placing the planet very high in the sky at sunset and making it visible for long afterward, won't be matched again until the year 2004. Venus passes within a degree north of the Pleiades on April 2 and 3 and within 10 degrees north of Aldebaran ten days later. Mercury can be seen for most of April, in its best evening appearance of the year, very low in WNW at dusk to the lower right of Venus. Comet Hyakutake may put on a good show in the NW at nightfall, until it sinks into bright twilight in the last few days of the month. Dawn skywatchers can't help but notice bright Jupiter in SSE to S while birds sing an hour before sunup. The Last Quarter (half) Moon is nearby on April 10. An hour after sunset on Astronomy Day, Saturday, April 20, the Moon is beautifully framed by Aldebaran and the Hyades cluster, with Venus, Mercury, and a possibly rebrightened Comet Hyakutake adding their lustre to the scene. A diagram is available below. ********* SKYWATCHER'S DIARY: APRIL 1996 ******** The Lunar Eclipse of Wednesday, April 3: What you can see depends on your location: The farther east you are in the U.S., the better; if you're too far west, you won't see it at all! The Moon on Wednesday, April 3 will rise in total eclipse from the Great Lakes, Southeast, Mississippi River, and Gulf Coast. But in these regions it would be well not to have high expectations of what might actually be seen: The disk of the Moon in total eclipse is too dim to be seen in bright twilight, and within the U.S. it's likely to be seen only from eastern states, after the sky has darkened. A total eclipse on September 26 will occur later in the evening and be more widely visible. What you'll see of the eclipse on April 3 depends on your location. From New England, New Jersey, and eastern New York state, Moon rises already in partial eclipse, and all later stages, including totality, happen with Moon above horizon. For rest of eastern and central U.S. westward to Minnesota and eastern third of Texas, the Moon rises invisibly in total eclipse. In mid-Michigan, for example, where the Moon rises in the middle of totality, the Moon isn't likely to be seen until it begins to emerge from Earth's shadow, at 7:53 p.m. EST. Still farther west, from the Dakotas and rest of Texas west to central Montana and western Arizona, Moon rises during the terminal partial stages of the eclipse. Still farther west, Moon rises after the umbral eclipse is all over. During the lunar eclipse on Wednesday, Apr. 3, the farther east you are, the more of the eclipse you'll see; the best places in U.S. to view totality are New England, New Jersey, eastern New York, and the Atlantic Coast down to North Carolina, after the sky has darkened enough to allow observation of the dimly lit eclipsed Moon. Depending on the darkness of Earth's shadow on the Moon, mid-totality at 7:10 p.m. EST may be visible only from eastern New England. If the Moon at mid- eclipse is uncharacteristically bright, it might be seen over more of northeastern U.S. Totality ends at 7:53 p.m. EST. By then evening twilight is over (the sky is dark) in eastern New England and the eastern tip of Long Island, and twilight is nearly over in North Carolina's Outer Banks and in southeast Florida. Along a line from eastern Ohio to the middle of the Florida panhandle, totality ends in the deep blue skies of nautical twilight, with the Sun 12 degrees down and the Moon 11 degrees up. Somewhere near that line and from all locations farther east, for a few minutes after 7:53 p.m., the Moon will display a narrow bright sliver at its lower edge, while the rest of the disk still in shadow appears a dim rusty-grey color, giving the Moon the appearance of a beautiful diamond ring, a term usually applied to a solar eclipse. The farther west you are as totality ends, the brighter the sky will be, and harder it will be to see the still-dimmed Moon. From mid-lower Michigan to the Mississippi-Alabama coast, totality ends in mid- twilight, with the Sun 9 degrees down and the Moon 8 degrees up; unless the eclipse is unusually bright, totality will be noted only by the Moon's absence. There and farther west to Minnesota and east Texas, the Moon probably won't be seen until it begins to emerge from the umbra at 7:53 p.m. EST (6:53 p.m. CST). Still farther west, from the Dakotas and rest of Texas west to central Montana and western Arizona, the Moon rises during the terminal partial stages of the eclipse. The Moon is completely out of the umbra by 8:59 p.m. EST (7:59 p.m. CST, 6:59 p.m. MST). If you're west of a line from central Montana to western Arizona, you're out of luck -- the umbral eclipse is completely over before moonrise! You'll have to wait for this year's second lunar eclipse, on Sept. 26. It will occur later in the evening, so will be in better view, higher in the sky for all skywatchers across the continental U.S. Enhancing the beauty of September's Harvest Moon total eclipse will be the presence of Saturn just two degrees away during totality. Tuesday, April 2 At nightfall, find spectacular Venus in the west. About a degree from this "evening star", to its upper right tonight, and to its lower right on Wednesday, find the compact Pleiades, or Seven Sisters, star cluster. Binoculars give the best view of this cluster of faint stars so close to the brilliant planet. Seen through a telescope these evenings, Venus is now about one-half illuminated. Note the bright star Capella very high in WNW 29 degrees upper right of Venus. At nightfall on April 2, Comet Hyakutake will be about 2 degrees lower right of the 2nd-magnitude star Mirfak, or Alpha in Perseus. Locate Mirfak in NW, 27 degrees upper right of Venus, and 19 degrees lower right of Capella. Starting Friday, April 5, moonlight won't interfere with comet viewing if you look when the comet is highest in a dark sky, right at nightfall. On Wednesday, the Moon has a rendezvous with Earth's shadow. If you're not too far west in the U.S., remember to observe the lunar eclipse. For details, see above. Wednesday, April 3 Here are our local plans to observe the lunar eclipse at Abrams Planetarium at Michigan State University. Viewing circumstances will be very similar from mid-lower Michigan along a line southward to the Mississippi-Alabama coast, except the times would be one hour earlier if you're on Central time. See above for more information about the visibility of the eclipse if you're viewing it from any other part of the country. At Abrams Planetarium, if skies are clear this evening, we are holding a public viewing session for tonight's total lunar eclipse. In Michigan, the Moon will rise in total eclipse right around sunset, but will probably remain invisible in twilight until it begins to emerge from Earth's shadow at 7:53 p.m. EST. Our session will begin at 7:30 p.m., at the east end of the top level of the parking ramp behind Abrams Planetarium (that's the end farther from the Planetarium and closer to the Moon). While we're waiting for the Moon to appear low in ESE, we'll watch early spring stars come out, enjoy telescopic views of Venus in its "half moon" phase, binocular views of Venus near the Pleiades star cluster, and of Comet Hyakutake in NW below the Alpha Persei cluster. The session will end with Moon's complete emergence from Earth's shadow at 8:59 p.m. EST. Thursday, April 4 The Moon, now just past Full, rises 10 to 15 degrees south of due east about an hour after sunset. Look for Spica about 6 degrees to Moon's upper right. At dawn on Friday, the Moon will be in SW to WSW, with Spica about 10 degrees to Moon's lower right. Friday, April 5 Dark skies return tonight for comet viewers. At nightfall, the Moon won't be up yet, and Comet Hyakutake is in northwest, 23 degrees right of Venus and 23 degrees lower right of Capella.Note the 2nd-magnitude star Algol within 4 degrees to the comet's lower left. Early next week, the comet will pass closely lower right of that star. The Moon rises just over 2 hours after sunset from northern U.S. tonight, 20 degrees lower left of Spica. Saturday, April 6 At sunset, Venus is over 40 degrees up in the west. Within half an hour, Mercury appears 35 degrees to Venus' lower right. Mercury is easy to see in a few evenings and remains in view for rest of April. At nightfall the Pleiades star cluster appears 3 or 4 degrees to Venus' lower right. Comet Hyakutake remains 22 degrees from Venus tonight through all next week, shifting from right to lower right of the planet. An hour before sunrise on Easter Sunday, Moon is in SSW with Antares, heart of Scorpion, 11 degrees to its lower left. Sunday, April 7 Mercury becomes an easy evening"star" this week, closing from 34 to 29 degrees to the lower right of brilliant Venus. Look about 45 minutes after sunset. An hour before sunrise on Monday, face S to SSW to see the waning gibbous Moon and the star Antares within 10 degrees to its lower right. Monday, April 8 As darkness falls, face west and note the star Aldebaran, eye of Taurus, 11 degrees left of brilliant Venus. A line from Aldebaran to Venus, extended to the right twice as far past Venus, ends at the 2nd-magnitude star Algol in NW. Tonight Comet Hyakutake is about one degree lower right of Algol. As it approaches the Sun, the comet may brighten during the next two weeks and develop a fine dust tail. Binoculars give the best view. An hour before sunup on Tuesday, the Moon is approaching due south. Note Antares in SSW and bright Jupiter in SSE. Follow Moon's progress Tuesday and next two mornings. Tuesday, April 9 With your arm fully extended, your fist covers about 10 degrees of sky. With that in mind, use your fist to measure angular distances between stars. About 45 minutes after sunset, find brilliant Venus in western sky, then look very low in WNW for Mercury 32 degrees (about three fists) to its lower right. Look very high 24 degrees upper right of Venus for Capella, brightest star in NW quarter of the sky, but not as bright as Venus. As sky darkens, Comet Hyakutake becomes visible within 22 degees right of Venus and 25 degrees lower right of Capella, the three bodies forming a nearly equilateral triangle. Note the comet has a fuzzy appearance, especially when viewed with binoculars. The 2nd- magnitude star just over a degree above the comet is Algol. An hour before sunup on Wednesday, the Moon is in SSE with bright Jupiter 5 degrees to its lower left. The Moon is approaching Last Quarter phase, half full, and 90 degrees or a quarter-circle west of the rising Sun. This lunar phase is ideal for study with binoculars and small telescopes; striking detail can be seen near the terminator (day-night boundary). Wednesday, April 10 In W to WNW at nightfall, Venus, Capella, and Comet Hyakutake form a large, nearly equilateral triangle 22 to 25 degrees on a side. Brilliant Venus marks the lower left corner of the triangle, Capella marks the top, and the comet the lower right corner. Tonight the star Algol may appear within the comet's tail or near its edge -- a beautiful sight for binoculars! In the predawn darkness of Thursday, about 1-3/4 hours before sunrise, the Moon is in SE, just under half full. Bright Jupiter is 11 degrees to Moon's right. Next year's bright Comet, Hale-Bopp, is now a distant telescopic object of magnitude 8, some 3 or 4 degrees lower right of the Moon, 8 degrees left of Jupiter, and one degree below the 5th- magnitude star 56 Sagittarii. The view improves in coming days as the Moon moves on. Thursday, April 11 Today, Comet Hyakutake passed 21.5 million miles from Venus, at a relative speed of nearly 172,000 miles per hour. Tonight as darkness falls, look for the comet in NW, 22 degrees lower right of the brilliant evening "star" Venus, and 2.5 degrees lower left of the 2nd-magnitude star Algol. Friday, April 12 Tonight and Saturday, Venus passes Aldebaran, eye of Taurus the Bull. This reddish first-magnitude star is within 10 degrees lower left of Venus at nightfall, while the Pleiades cluster is nearly as far to Venus' lower right. Aldebaran marks the top of the left arm of the V-shaped Hyades cluster. Both Hyades and Pleiades are beautiful fields for binoculars. Look for the Comet 22 degrees lower right of Venus and 3 degrees lower left of Algol. Saturday, April 13 Tonight, Comet Hyakutake is nearly 61 million miles from Earth and 55 million miles from the Sun. Although it is speeding away from Earth, the comet is rapidly closing in on the Sun. Watch for it to brighten noticeably in the next week. At nightfall look low in NW, 22 degrees lower right of Venus and 4 degrees lower left of the 2nd-magnitude star Algol. Sunday, April 14 Mercury is in excellent view this week; an hour after sunset, look in WNW, 28 degrees lower right of brilliant Venus. As the sky darkens further, look for Comet Hyakutake 23 degrees lower right of Venus and 20 degrees upper right of Mercury. With each passing day this week, the comet is over 2.3 million miles closer to the Sun. The comet should brighten and its tail develop nicely, in time for Astronomy Day, Saturday, April 20! Last easy chance to see the old Moon: 45 minutes before sunrise on Monday, look for the thin old crescent very low, nearly due east. Binoculars may show Saturn rising 7 degrees to Moon's lower left. Saturn is higher and easier from southern states. Monday, April 15 Let Venus, the brilliant evening "star", guide you to some beautiful fields for binoculars: Aldebaran and the Hyades star cluster 7 to 11 degrees to Venus' lower left; the Pleiades or Seven Sisters cluster 11 degrees to Venus' lower right; and Comet Hyakutake 16 degrees right of the Pleiades and 24 degrees lower right of Venus. Tuesday, April 16 An hour after sunset, Mercury is low in WNW, 26 degrees lower right of Venus. As the sky darkens, look for the Pleiades cluster between them and 12 degrees lower right of Venus. Look also for Comet Hyakutake 16 degrees right of the Pleiades, 24 degrees lower right of Venus, and 17 degrees upper right of Mercury. In next 10 days, the comet and the Pleiades sink lower each evening, remaining 16 degrees apart through April 26. Day by day the comet sinks faster than the cluster, and will disappear to the cluster's lower right. For the latest predictions and reports on Comet Hyakutake, check the following Websites: http://www.skypub.com/comets/hyaku3.html#top http://www.jpl.nasa.gov/comet/hyakutake/ Wednesday, April 17 The Moon is New today at 6:49 p.m. EDT (3:49 p.m. PDT) and is not visible. If you can spot the Moon shortly after sunset on Thursday, note the time, and calculate the Moon's age (time elapsed since New). Tonight Comet Hyakutake appears 25 degrees to Venus' lower right at nightfall. Thursday, April 18 Within half an hour after sunset, try for the young Moon very low, 10 to 15 degrees N of due west. Before spotting Moon, you'll probably see Venus, about 40 degrees up in W at sunset. Mercury appears 25 degrees to Venus's lower right, and the thin sliver of a crescent Moon is 8 degrees to Mercury's lower left. The Moon's age is 25 hours from eastern New England, 26 hours from lower Michigan, and over 28 hours from the West coast. This Saturday is National Astronomy Day, and this weekend many planetariums and astronomy clubs are holding special events to celebrate the occasion. Contact your local group and join in! At Abrams Planetarium, we'll offer "Spring and Summer Skies", this weekend only, on Friday and Saturday at 8 p.m., and Sunday at 4 p.m. After the evening shows if skies are clear, the Michigan State University Observatory will be open for viewing of the beautiful gathering of the Moon, Mercury, Venus, and Comet Hyakutake before the comet departs from our evening skies. Friday, April 19 A very pretty sight for naked eye and binoculars awaits us tonight and Saturday, about an hour after sunset: The crescent Moon is low in W to WNW, with earthshine filling out the disk where no direct sunlight reaches. Tonight Venus shines 21 degrees above the Moon, and Mercury twinkles 8 degrees to Moon's lower right. Aldebaran and the Hyades cluster glow to Moon's upper left and Venus' lower right. The compact dipper-shaped Pleiades glitter about 10 degrees above Mercury and the Moon. As the sky darkens further, Comet Hyakutake is 27 degrees lower right of Venus and 14 degrees uppper right of Mercury. Saturday, April 20 Skywatchers gathering tonight for Astronomy Day will have some especially wonderful sights for binoculars. Begin about an hour after sunset with the two brightest objects in the night sky, low in W to WNW: Venus 12 degrees to upper right of the crescent Moon. Next find Mercury 24 degrees to Venus' lower right, and the star Aldebaran some 2 or 3 degrees to Moon's upper left. Direct your binoculars at the Moon, and you'll see it is beautifully framed by the "V" of Aldebaran and the Hyades cluster of stars. Next, find the Pleaides compact cluster of stars about 3/5 of the way from Venus toward Mercury. Finally, as the sky darkens, look for Comet Hyakutake: A line from the Moon to the Pleiades, 11 degrees long, extended 16 degrees past the Pleiades, ends near the Comet, low in NW. Three bodies give clues to the Sun's location below the horizon this evening. The Moon's bright crescent is illuminated by the Sun. If you examine Venus through a telescope, you'll see it also displays a crescent, about 3/8 full, with its bright side also toward the Sun. What is the third clue? It's the comet, with its tail pointing away from the Sun! For a rendering of this gathering, set Web Browser to: http://www.pa.msu.edu/abrams/ Sunday, April 21 An hour after sunset, Venus is 10 degrees to Moon's upper right, Aldebaran 10 degrees to Moon's lower right. Mercury is 24 degrees lower right of Venus. The Pleiades cluster is 8 degrees from Mercury and 1/3 of the way toward Venus. As the sky gets darker, look for Comet Hyakutake 13 degrees upper right of Mercury and 29 degrees lower right of Venus. The comet passes 19.5 million miles from Mercury today, and will pass 21.4 million miles from the Sun on May 1. Monday, April 22 From Earth's vantage point tonight, Mercury appears farthest from the Sun in its current evening appearance, 20 degrees. An hour after sunset, locate Mercury 24 degrees to the lower right of brilliant Venus. To help you estimate that distance, tonight Venus appears 18 degrees to the Moon's lower right, and Betelgeuse, shoulder of Orion, appears 11 degrees to Moon's lower left. Aldebaran, eye of Taurus, appears 12 degrees lower left of Venus. As twilight deepens, look for the Pleiades upper left of Mercury. A line from Aldebaran to the Pleiades, 14 degrees long, extended 16 degrees, ends near Comet Hyakutake, in NW. Tuesday, April 23 An hour after sunset, Procyon, Little Dog Star, is 15 degrees left of the Moon. The twins, Pollux and Castor, are a similar distance above the Moon. As twilight deepens, but before sky darkens completely, a line from the Moon to Venus, nearly 30 degrees long, extended about as far past Venus to NW horizon, locates the soon-to-depart Comet Hyakutake. Wednesday, April 24 An hour after sunset Procyon is 10 degrees to Moon's lower left. Pollux and Castor are to Moon's upper right. From northern U.S. tonight, Comet Hyakutake still sets in a dark sky, barely after the end of twilight. The best time to look may be about 1-1/4 hours after sunset, depending on the comet's brightness. Look very low in NW, 32 degrees lower right of Venus and 13 degrees right of Mercury. If the comet brightens sharply on its approach to the Sun, it may be visible for a few more evenings, in bright twilight. Thursday, April 25 The Moon, near First Quarter phase, is about 90 degrees east of the Sun in the afternoon and evening sky. Note the Moon's shape is half full, ideal for using binoculars to see surface features near the terminator (day-night boundary). Tonight, Comet Hyakutake is only 16 degrees from the Sun, and so can be seen only in twilight, and only if it's bright enough. From a site with an unobstructed view toward NW, look 1 to 1-1/4 hours after sunset, 33 degrees lower right of Venus and 14 degrees lower right of Mercury. It's possible the comet's tail could extend above the horizon after dark. Friday, April 26 One hour after sunset, the Moon is high in SSW. Regulus, heart of Leo, is 11 degrees to its upper left. From lower Michigan, Comet Hyakutake sets in NW only 1 hour 20 minutes after sunset. Try about an hour after sunset, 14 degrees lower right of Mercury. Saturday, April 27 The Moon is high in S at dusk, with Regulus 5 degrees to upper right. Mercury is of first magnitude, but fading fast. Aiming binoculars low in WNW within an hour after sunset, can you still see Mercury with the Pleiades 3 degrees above? Try also for the comet 15 degrees to Mercury's lower right. Sunday, April 28 Have you seen Saturn yet since it was beyond the Sun in mid-March? An hour before sunrise on Monday, look barely above eastern horizon. With Saturn so low, viewing conditions are poor for telescopic viewing of the rings, now tipped 4 degrees from edgewise with their illuminated south face visible. The view will improve in coming months as Saturn rises earlier. Monday, April 29 Brilliant Venus is still well up in W to WNW at dusk, but it will rapidly get lower next month. Venus will also show striking changes when seen through a telescope. Next month, Venus will get close enough to Earth so that its crescent phase will be observable even through 7-power binoculars. The key is to observe Venus in the daytime, or shortly after sunset, to avoid its brilliant glare against a darkened sky. On Tuesday and Wednesday Venus will pass within a degree of the northern horn of Taurus the Bull. Look nightly. Tuesday, April 30 The Moon is in SE at dusk with the first-magnitude star Spica 13 degrees to its lower left. Spica marks the spike of wheat in the hand of Virgo. Look again Wednesday evening, and you'll find Spica just 2 degrees to the Moon's south (lower right). On Wednesday morning, May 1, Comet Hyakutake passes only 21.4 million miles from the Sun, and begins its estimated 9,000-year journey to the dark, cold outer reaches of the solar system some 35 times as far out as Pluto's average distance from the Sun. What will Earth be like when the Comet returns some 18,000 years in the future? From lower Michigan on Wednesday, Comet Hyakutake will rise 31 degrees north of due east about 35 minutes before sunrise. The comet will be within 7 degrees upper left of the Sun, but if it's much brighter than predicted, it could still be visible in bright twilight, shortly before sunrise. On Thursday, the comet will rise barely 30 minutes before sunup, less than 6 degrees directly above the Sun. To avoid the hazards of looking at the Sun through optical equipment, look *before* sunrise. For the latest predictions and reports on Comet Hyakutake, check the following Websites: http://www.skypub.com/comets/hyaku3.html#top http://www.jpl.nasa.gov/comet/hyakutake/ ********** end of Skywatcher's Diary for April 1996 **********