Night_skies_may07

Jeff Green | Apr 27, 2006

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TheNightSkies of May, 2006:Jupiter at its Brightest, and a Bright Comet

by Leo Enright

In this area, on May 1, sunset is just after 8:00 p.m. EDT, and by the end of the month, it is at 8:40 p.m., an average difference of over one minute per day. Over the same period, the end of evening astronomical twilight moves from 10:00 p.m. to about 11:00 p.m. an average difference of about 2 minutes per evening. In the morning, on May 1, astronomical twilight begins at 4:00 a.m., with sunrise at 6:00 a.m., but by the end of May twilight begins just after 3:00 a.m., and sunrise is at 5:30 a.m. Complete darkness in this area on the last day of the month is from 11:00 p.m. to 3:00 a.m., that is, for only 4 hours.

The long evening twilights of May give us a great opportunity to observe the bright stars of the spring constellations. As twilight slowly darkens, try to take note of the easily-seen pattern of Leo, the Great Lion of ancient mythology, high in the southern sky, and Virgo, the young lady of the ancient tales, at mid-height in the southeastern sky. In Leo, the distinctive pattern is twofold: a ‘backwards question mark’ above the very bright star Regulus, and a right-angled triangle to its left with Denebola as the brightest star in the triangle. In this pattern, our ancestors saw the outline of a crouching lion facing westward in the sky. To its left, in the middle of the reclining outline of Virgo is the brilliant white star Spica, seen by the ancient Romans as the ear of corn or wheat held by Astraea, the goddess of justice, though many ancient cultures saw it as the central star in the outline of another one of their important female deities. These three bright stars are at vastly different distances from our Earth. Regulus is 69 light years away. Denebola is 40 light years away. Spica, though easily seen to be much brighter than Denebola, is actually six times farther away, at a distance of 275 light years. Spica’s INTRINSIC brightness is incredibly great, actually 2300 times that of our sun! The brightest planet to be seen in the evening sky is Jupiter, and even at the beginning of evening twilight it is easily seen low in the southeastern sky and to the left of Spica, and in the constellation Libra which is also the constellation to the left of Virgo. To the unaided eye, Jupiter this month appears brighter than at any other time this year; in binoculars or a telescope it is larger and more defined than usual, with its four moons and the dark belts and features in its swirling atmosphere more distinct than usual. Saturn and Mars emerge into view in the western sky during twilight. Saturn is the brighter of the two planets, and appears to the left of the twin stars of Gemini, Castor and Pollux, and separated from them by twice the distance between them. Reddish Mars is much fainter, and at the beginning of the month, is about the same distance below the Twin Stars as Saturn is to their left, but the orbital motion of Mars around the Sun appears to carry the planet upward until by month’s end it appears almost midway between Saturn and the Twin Stars. This Martian movement is very easy to notice, but Saturn’s movement will be noticed probably only by those who use binoculars to see that it is now moving back toward M44, the large, rich cluster of stars just to its left. Its retrograde movement of the past several months ended in early April, and Saturn is now moving forward (eastward) across the sky, but with its far greater distance from both Sun and Earth, its movement appears much slower and harder to detect than that of Mars. The planet Mercury will appear only in the last week of May, and it will be very low in the west-northwestern sky for a short time beginning about 45 minutes after sunset. Binoculars will help locate it in the twilight just above the horizon. Throughout the month, brilliant Venus rises in the eastern morning sky about 90 minutes before sunrise. With its brilliance it dominates the entire eastern sky throughout morning twilight.

The young crescent moon passes by two planets in the western evening sky both in early May and in late May. On May 1 and 2, the thin crescent marches past Mars, and on the 3rd and 4th it struts past Saturn. During the evenings of May 11 and 12, the Full Moon will be seen near Jupiter. At dawn on May 24, the waning crescent moon appears to the left of the radiant Venus. On the evening of May 27, observers with a good view of the western horizon and using binoculars, may be able to spot an extremely thin crescent moon just to the right of Mercury, between 30 and 45 minutes after sunset. On the 28th, the thin crescent will appear just above Mercury, at the same time. The next evening, it will be below the stars Castor and Pollux, and on May 30, it will be between the Twin Stars and Mars. On the following evening, the crescent moon will appear just above Saturn, very close to where it was on May 4. Try not to miss any of these chances to observe, and possibly photograph, the thin crescent moon going past three planets in the evening twilight. As the ads used to say: “Kodak moments!”

This month brings us a good chance of seeing a bright, probably naked-eye, comet, though readers should not expect a repeat of the 1997 views of Comet Hale-Bopp. This latest one I have been observing for a while in binoculars as its distinctive tail has grown in brightness and as it has moved northward in the sky. It has the name Comet 73P (Shwassmann-Wachmann 3). It was photographically discovered in Hamburg, Germany on May 2, 1930 by Arnold Schwassmann and Arno Arthur Wachmann. It is a “short period” comet – with a period of only 5.36 years. On some of its passes through the inner solar system it has come close to Earth. That happened in 1979. Recently it has been observed as a comet that has split into over 20 parts. On the current 2006 pass, it will pass less than 12 billion km from Earth, one of the closest of any comet in recorded history. On moonless nights, it may well be visible to the naked eye from a site without light pollution, but binoculars are suggested. Look well up in the eastern sky between 10:00 and 11:00 p.m. From May 1 to 5, look in the constellation Hercules, in the star-pattern called “The Keystone”. From May 6 to 9, look in Lyra to the right of the brilliant star Vega. From May 10 to 15, look in Cygnus, to the right of the star Deneb. From May 16 to 21, look in Pegasus to the right of the Great Square. I hope all readers obtain a good view of this very interesting comet.

A famous meteor shower known as the Eta Aquarids reaches its annual peak in early May. The best time to see a good number of bright “shooting stars” is in the early morning hours of May 4, 5, and 6, beginning about 3:00 a.m. Look in a generally eastward direction.

International Astronomy Day will be marked on Saturday, May 6. In the afternoon, everyone is invited to join RASC - Kingston Centre members for solar observing and viewing of displays at the Isabel Turner Library beside Cataraqui Town Centre parking lot. In the evening, after 8:30 p.m. observing with binoculars and telescopes will be held at Little Cataraqui Creek Conservation Area off Division Street, 2 km north of Hwy 401.

Information about the spring and summer sky, including the constellations through which the comet will pass, may be found in The Beginner’s Observing Guide, available at Sharbot Lake Pharmacy.