JAMESTOWN, N.D. (NewsDakota.com) – The following is an article written and provided by Dr. Timothy Bratton, U.J. Prof. Emeritus of History and Amateur Astronomer
Venus is the only “evening star” this month; the remaining naked-eye planets rise after midnight. There is one decent meteor shower in April, the Lyrids, which will appear on the morning of April 22.
April 2 (Mon.): At 6 a.m. CDST [Central Daylight Savings Time], just before the onset of nautical twilight, two bright planets will be close together in the SSE sky. Ruddy Mars (magnitude 0.25) will be elevated 16.7 degrees, 8.54 seconds of arc in apparent diameter (still too tiny to show much detail in small telescopes), 87.93% illuminated, 101,777,315 miles from the Earth, and 142,482,660 miles from the Sun. Only 1.27 degrees above it, slightly to its left, and a little fainter will be yellow Saturn (mag. 0.5). The gas giant will be then 16.6 arc-seconds across (its famous rings, now tilted 25½ degrees toward Earth, have a span of 37.57 arc-seconds), 99.8% lighted, 925,077,600 miles from our world, and 935,658,510 miles from the Sun. Although you’ll need a telescope to see its rings clearly, Saturn still displays an elongated appearance in binoculars or field glasses. Watch Mars brighten until the Earth overtakes it in late July.
April 3 (Tues.): At 6 a.m. the Moon will be 23.9 degrees above the SSW-SW skyline, 30.72 arc-minutes in apparent span, 90.4% sunlit, and 243,235 miles distant. 4.1 degrees to its lower left will be bright beige Jupiter (mag. –2.4). At that hour the largest world of the solar system will be 42.78 arc-seconds across (even with modest optical aid it will show a disk), 99.7% lit, 427,522,350 miles from the Earth, and 503,485,835 miles from the Sun.
April 7 (Sat.): The waning gibbous Moon joins Mars and Saturn in the predawn SSE sky this morning. At 6 a.m. the Moon will be 20.23 degrees above ground level, 29¾ arc-minutes across, 58.1% sunlit, and 250,880 miles away. 1¼ degree to its lower left will be golden Saturn (mag. 0.5), then 16¾ arc-seconds in apparent diameter (its rings span 37.9 arc-seconds), 99.8% illumined, and 917,655,405 miles from Earth. Like Mars, Saturn is gradually becoming larger and brighter as the Earth overtakes it. 2.87 degrees to the lower left of Saturn is Mars (mag. 0.15), now 8.92 arc-seconds across, 87.87% lighted, 97,547,825 miles from Earth, and 141,692,535 miles from the Sun.
April 8 (Sun.): The Moon attains both apogee (its farthest distance from the Earth this month) and its Last Quarter phase this morning. The former occurs at 12:31 a.m., when Luna will be 251,123 miles distant but 27 2/3 degrees under the eastern horizon. The latter takes place at 2:18 a.m., when the Moon still will be 10.4 degrees below our city’s ESE horizon.
April 15 (Sun.): New Moon occurs at 8:57 p.m., when it will be 9½ degrees beneath Jamestown’s WNW horizon. As it is passing well to the south of the Sun this month, no kind of solar eclipse will be possible.
April 17 (Tues.): Saturn, the sixth planet from the Sun (and the farthest naked-eye planet observed in antiquity), takes 29.46 years to complete each orbit around the star. Today Saturn reaches aphelion, its greatest distance from the Sun, when the two bodies are 935,660,220 miles apart. Because Saturn and the Earth are on the same side of the Sun, with the faster Earth gaining on the ringed world, Saturn will continue to swell in size and brightness until they are closest together in late June. At 9 p.m. the young crescent Moon will be 13 degrees above the western horizon, 32.28 arc-minutes across, only 5.27% illumined, and 230,765 miles distant. The dazzling white “star” 5.8 degrees to its upper right is Venus (mag. –3.9); the second planet from the Sun will be then 11.2 arc-seconds in span, 91.2% lighted, 140,446,930 miles from Earth, and 66,913,310 miles from the solar disk.
April 18 (Wed.): At 9 p.m. the crescent Moon will be 24.43 degrees above the western horizon, 33.12 arc-minutes in apparent diameter, 11½% lit, and 229,690 miles away. It is passing through the Hyades, a loose cluster of old yelloworange suns, which lies 151 light years from Earth. About 2½ degrees to the Moon’s upper left lies red Aldebaran (Alpha Tauri, mag. 0.85), the fiery “eye” of the V-shaped constellation of Taurus the Bull. The Moon will pass only 1.1 degree north of Aldebaran around midnight, but both objects will have set by then.
April 20 (Fri.): The Moon attains perigee (its closest approach to the Earth this month) at 9:41 a.m., when it will be 229,108 miles away but 4.9 degrees under the NE-ENE skyline.
April 22 (Sun.): After the Moon sets around 2 a.m., its light will not interfere with the annual Lyrid meteor shower. These meteors are debris from Comet C/1861 G1 Thatcher, which was discovered by A.E. Thatcher on April 4, 1861. This is a long-period comet, returning to the Sun every 415 years. However, the Lyrids have been observed since 687 B.C., when the Chinese duke Zguang of Lu noted that “stars fell like rain,” also in April. Usually there are 18-20 Lyrids visible per hour, but there have been outbreaks where 250 to 600 meteors were seen per hour. The best guess is that the nucleus of Comet Thatcher fractured during one of its previous visits, and the orbit of the richest debris field has been modified by the meteors’ passage past the outer solar system’s planets. This probably will be a “normal” year for the Lyrids, but in any event they should be worth watching. Choose a site far away from light pollution. These fairly bright meteors (most attain third to second magnitude) enter the Earth’s atmosphere at an average speed of 30.4 miles per second, burning up within half a second; perhaps 20-25% will leave glowing trains behind them that persist for several more seconds. Most Lyrids burn up while still 54 to 66½ miles high in the Earth’s atmosphere. The radiant (point from which the meteors appear to originate) lies roughly 8.2 degrees to the upper right of brilliant bluewhite Vega (Alpha Lyrae, magnitude 0.03), the dominant sun in Lyra the Lyre. At 4 a.m. this star will have risen 64 11/12 degrees above the eastern horizon. A little over twelve hours later First Quarter Moon will occur at 4:46 p.m., when it will be 42.45 degrees above the ESE horizon, 33¼ arc-minutes across, and 230,155 miles distant.
April 24 (Tues.): At 9 p.m. the waxing gibbous Moon will be 53 1/3 degrees over the SSE horizon, 32.4 arc-minutes across, 73.73% lighted, and 232,585 miles from Earth. 3.43 degrees to its upper right will be blue-white Regulus (Alpha Leonis, mag. 1.35), the bright star that marks the bottom of the “Sickle” or reversed “Question Mark” of the constellation of Leo the Lion.
April 27 (Fri.): At 9:26 p.m., 45 minutes after sunset, dazzling white Venus (mag. –3.9) will be sandwiched between two other celestial objects. At that time the cloud-shrouded world will be 14½ degrees above the WNW horizon, 11.38 arc-minutes across, 89.2% illuminated, 136,236,235 miles from the Earth, and 66,838,638 miles from the Sun. 8.55 degrees to its upper left will be red-orange Aldebaran, described in the entry for April 18. 5.13 degrees to its lower right will be M45, the 45th item in the list of fuzzy objects compiled by comet hunter Charles Messier (1730-1817); it is known better as the Pleiades or “Seven Sisters” open star cluster. Some people think that it looks like an extremely tiny version of the “Big Dipper” to the naked eye. M45 reveals dozens of suns in binoculars, and hundreds in a telescope. The many suns of this cluster, which are spread over 1.83 degrees of arc, give M45 a cumulative magnitude of 1.2, although its brightest star, blue-white Alcyone (Eta Tauri), attains a magnitude of just 2.87. While the distance of each Pleiad from our solar system varies considerably, as a whole the cluster lies 410 light-years away.
April 29 (Sun.): Mercury, which has returned as a “morning star” before dawn, will attain its maximum western elongation of 27 degrees from the Sun today. Unfortunately, the ecliptic (the apparent path of most planets around the Sun) runs almost parallel to the eastern horizon this time of year, so that Mercury’s elongation does not translate into much elevation before sunrise. When civil twilight begins at 5:49 a.m., the innermost planet of the solar system will have struggled merely 1.13 degrees above the eastern horizon. At that moment yellowish Mercury (mag. 0.5) will be 8.08 arc-seconds in apparent span, 42.9% illumined, 42,947,155 miles from the Sun, and 77,337,885 miles from Earth. Even with optical aid, you would need exceptionally clear skies to spot this elusive little world in the twilight glare before the Sun rises at 6:22 a.m. Full Moon takes place tonight at 7:58 p.m., when Luna will be 4.85 degrees below the E-ESE skyline, 30.6 arc-minutes in apparent diameter, and 242,100 miles away.
April 30 (Mon.): For the second time this month, the Moon has returned to the vicinity of mighty off-white Jupiter (mag. –2.5). At midnight Sunday/Monday the Moon will be 19.2 degrees above the SE horizon, 30.48 arc-minutes across, 98.39% lit, and 244,650 miles distant. 6.47 degrees to its upper right will be glowering Jupiter, then in its full phase, 44.61 arc-seconds in span, 410,253,240 miles from Earth, and 502,984,885 miles from the Sun. Jupiter is fun to observe; even in binoculars, it displays a tiny disk, and usually you can see one to four of its large “Galilean” satellites spotted by that great Italian astronomer in 1609-10.
Best wishes to U.J. students as you head into your final exams early in May!