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Skywatch July 2005by Julene M Packer-JohnsonJuly opens with Mercury, Venus & Jupiter becoming visible as the skies darken at sunset. Mars rises after midnight. Saturn conjuncts the Sun this month and is not visible. The Delta Aquarid meteor shower peaks in late July. Earth reaches aphelion and Mars reaches perihelion this month. On the 4th of July, NASA will blast a hole in comet Tempel 1, and give us something different to try to locate as we wait for the fireworks to begin. Northern Hemisphere Observation Dance of Mercury & Venus As twilight encroaches on the 1st, watch for Mercury & Venus to appear low along the western horizon. They are traveling through the constellation Cancer of the sidereal zodiac. Venus will be very bright and easy to spot, but Mercury is growing dimmer and will be a bit harder to locate. Use Venus as your guide. Mercury will be on her left. The two remain side by side for a few days before Venus starts to pull away from Mercury. On the 8th at 11:00 p.m. EDT, Mercury reaches greatest eastern elongation, meaning he will be as far east of the sun he can possibly travel. By this night Venus will have climbed slightly higher in the sky than Mercury. Also on the 8th, the Moon joins the evening duo. The planets will hang below a sliver of a 2.5 day old moon. The second week of July you can watch Venus pull away from Mercury as she travels farther east from the sun than Mercury is able to. Mercury is also slowing down in preparation for his retrograde station on the 22nd. After about midmonth, Mercury will become more and more difficult to locate as he descends into the sunset. Venus, however, will continue to climb upwards out of the sunset as she moves east through the zodiac. By the 15th Venus will have moved into the constellation Leo. Leo’s alpha star, Regulus, will be above her and to her left. On the 20th and 21st, she will lie next to Regulus. The alpha star will still be on her left. Watch as she passes the fixed star. By month’s end, Regulus will be below and to the right of Venus. Jupiter in the Evening Sky (North) Looking to the southwest sky at sunset, you can find Jupiter. Venus is almost 2 magnitudes brighter than Jupiter, yet Jupiter is brighter than any stars around. This means that if you begin watching the heavens as soon as twilight begins to descend upon earth, Venus will be the first ‘star’ you see pop into view and Jupiter will be the second. As the skies darken, watch for Arcturus of Bootes to appear high above Jupiter. Then watch for Spica of Virgo to pop into view to the left of Jupiter followed by Regulus of Leo between the two bright planets. This is the order of magnitude of the three brightest stars in the area and they should appear accordingly. Jupiter is traveling through the constellation Virgo. He begins the month in mid-constellation beneath the star Porrima. He will set around 1:00 a.m. By month’s end, he will have moved about one quarter of the way from Porrima to Spica and will set around 11:15 p.m. See if you can notice the Jovial Giant’s movement against the backdrop of the fixed stars of Virgo this month. Mars in the Midnight Sky (North) Mars is moving east through the constellation Pisces and heading toward Aries this month. The dim stars of Pisces will not help you to notice his movement against their hard to see backdrop. However if you keep your eye on the fixed stars Hamal and Sheratan of Aries, you will notice Mars move east toward those fixed stars as well as moving below them. On July 1st, Mars rises nearly due east around 1:30 a.m. among the dim stars of the constellation Pisces. The two stars of Aries rise at nearly the same time in the east-northeast. By midmonth, Mars will rise around 1:00 a.m., about 15 minutes after Hamal and Sheratan of Aries rise. Mars is also moving left of the due east rising position he had at the end of June. On the 31st Mars will rise around 12:30 a.m. below and to the right of the Aries’ stars that rise around 11:40 p.m. The Moon Dances with the Planets in the Northern Hemisphere On the evening of July 8th, a slender sliver of a recently new moon hangs above Mercury and Venus in the evening sky between the fixed stars of Cancer and Leo. The Moon travels east through the constellations of the zodiac and nears Jupiter in Virgo on the 12th. Jupiter will be to the left of the moon. On the night of the 13th, Jupiter will be to the right of the moon who will have danced on by Jupiter. On the 22nd the moon nears Mars who will lie to the right. By the 23rd, the moon will have danced on past Mars to lie on his left. Southern Hemisphere Observation Dance of Mercury & Venus As the sunset darkens the skies on July 1st, watch for Venus and Mercury to appear low along the western horizon among the stars of Cancer of the sidereal zodiac. Venus is much brighter and easier to locate. Mercury will be slightly above Venus. The Moon will join the pair on the evening of the 9th. As the month progresses, watch Venus gain on Mercury. By the 12th, Venus will be to the left of Mercury. By the time Mercury stations retrograde, Venus will be sufficiently above the Messenger and lie just below the fixed star Regulus of Leo. By month’s end Venus will have moved well into the constellation Leo to lie above Regulus. Due to longer night time hours, you will be able to observe Mercury later into the month than those in the northern hemisphere. You can locate him up until the 25th if you have dark skies along the western horizon and are far from city lights. Jupiter in the Evening Sky (South) Jupiter will be visible high above the western horizon as twilight darkens the skies. The easiest way to locate planets is to watch them become visible at the very beginning of sunset as they pop into view according to their magnitude. Venus will be the first to become visible since she is the brightest followed by Jupiter. Mercury will then pop into view, then Spica of Virgo followed by Regulus of Leo. Jupiter sets around 1:15 a.m. at the beginning of July and 11:45 p.m. by month’s end. Watch Jupiter against the backdrop of the fixed stars of Virgo, particularly Porrima. You will notice Jupiter to the left and slightly above Porrima of Virgo on the 1st. By month’s end you will notice that Jupiter has pulled east of this fixed star and find the distance between the two has increased. Mars in the Midnight Sky (South) Mars rises nearly due east around 1:45 a.m. at the beginning of July. As the month progresses his rising position moves slightly east-northeast. By month’s end he will rise around 1:20 a.m. Mars is traveling through the dim stars of the constellation Pisces. While he makes good progress this month, those stars are not likely to be bright enough for you to track his movement. Probably the best way for you to notice the eastward movement of Mars is to use the two bright stars that lie above Mars on his left and right when he rises. The bright star above and to the left of Mars is Markab of Pegasus. Markab will be located in the east-northeast when Mars rises. The bright star above and to the right of Mars is Deneb Kaitos in the constellation Cetus. Deneb Kaitos will be located in the east when Mars rises. If you are observing in the early morning before sunrise, Deneb Kaitos will be above Markab and Mars will be to their right. Watch as Mars increases his distance from these two stars as the month of July marches on. The Moon Dances with the Planets in the Southern Hemisphere On the evening of the 9th, a slender sliver of a recently new moon will hang above Mercury and Venus along the western horizon. On the evening of the 13th, the Moon will lie beneath Jupiter. She will dance on by the Jovial Giant by the next night to lie above. In the wee hours of the morning of the 29th, the Moon will rise with Mars on her right. If you look north just before sunrise, you will locate Mars above the Moon. Earth’s Aphelion & Mars’ Perihelion On July 5th at 1:00 am. EDT, Earth reaches aphelion to the Sun. Aphelion is the furthest distance a planet reaches from the Sun in its elliptical orbit. Earth will be 94.5 million miles from the Sun. On the 17th at 12:00 p.m. EDT, Mars reaches perihelion to the Sun. Perihelion is the closest distance to the Sun a planet reaches in its elliptical orbit. Mars will be 128.4 million miles from the Sun. Aphelion and perihelion are similar to apogee and perigee, only the first two terms are used to describe a planets proximity to the Sun and the latter two are describing the moons proximity to Earth. A trick to remember which word is the term for farthest or closest is to think “if it begins with ‘A’, it is further ‘A’-way.” Both aphelion and apogee are the terms used when the maximum distance is reached. That makes it easy, right?! The Delta Aquarid Meteor Shower The Delta Aquarid Meteor Shower occurs between July 14 – August 18 and peaks on the 27th of July. The radiants stem from the constellation Aquarius. The brightest star in the area, however, is Formalhaut of Pisces Austrinus. This constellation lies below Aquarius, so look above Formalhaut if you are in the northern hemisphere. If you are in the southern hemisphere, look to the right of Formalhaut for the constellation Aquarius and the shower radiants. This shower is better observed in the southern hemisphere. Aquarius does not gain near as much height in the northern hemisphere as it does in the southern hemisphere this time of year. Your best bet in the north is to look after midnight near the peak activity of the shower at the end of July. Southern hemisphere observers might be able to see 15 meteors per hour, while northern hemisphere observers may see about 10 per hour. NASA’s July 4th Event NASA’s Deep Impact spacecraft that was launched on January 12, 2005 will hit the comet Tempel 1 in the early morning hours of July 4th. Comet Tempel 1 is in the constellation Virgo near the planet Jupiter. While you are awaiting the fireworks in the United States and planet watching anywhere, try to see if you can find this comet. It is likely the impact will increase its magnitude. The OCA Public Library holds a sky map depicting the location of this comet to help you find it. For more information about this NASA mission, visit NASA's website. Moon Data The New Moon occurs on the 6th at 8:02 a.m. EDT. On the 8th the moon reaches apogee at 1:39 p.m. and will be 252,502 miles from Earth. On the 14th at 11:20 a.m. EDT the moon perfects waxing square to the sun resulting a First Quarter Moon. The moon opposes the sun on the 21st at 7:00 a.m. EDT resulting in a Full Moon. Also on the 21st, the moon reaches perigee at 3:44 p.m. EDT. The distance between Earth and Moon will be 221,928 miles. A Full Moon at the time of perigee will make the moon appear larger. On the 27th at 11:19 p.m. EDT the moon perfects waning square to the sun resulting in the Last Quarter Moon. Sky Maps Available in the OCA Main Public Library Sky Maps of July 4th depicting Mercury, Venus, Jupiter and the location of comet Tempel 1 are available in the OCA Public Library. The map of the northern hemisphere is for 10:00 pm and for the southern hemisphere at 7:30 p.m. Also available are sky maps of the July 28th depicting the position of Mars, Moon and the location of the Delta Aquarids. Maps are drawn for 2:00 a.m. in both hemispheres. Happy Star Gazing! Julene Packer-Johnson, Dipl.O.C.A., NCGR-III |
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