June 16, 2000
Contact: Barbara Anthony-Twarog, (785) 864-3910 or anthony@kubarb.phsx.ku.edu
1. We've had a string of lineups in the solar system over the past months. Another is scheduled for today, centered on a partial eclipse of the sun at the moment of new moon, about 2:20 p.m. Unfortunately, the eclipse will only be visible from the Southern Hemisphere. A solar eclipse happens because the moon does a nearly perfect job of lining up between the Earth and sun; it's partial this time because the moon is a bit too distant to adequately cover the sun's disk as seen from Earth. Not visible today is Mars, on the far side of the sun from Earth.
4. If you woke on the morning of July 4, 1054, what would you see? You might yawn, stretch and admire the predawn sky in the East. As is true in July of 2000, Mercury led the sun above the eastern horizon by barely an hour and in that year, too, Mars was in conjunction with the sun. Saturn would have been well above the waning moon. The shock you might have had, if you were well acquainted with the constellation Taurus where the moon was hanging out, would have been a new and stunningly bright star. Even if you missed this new star in its earliest days, as the summer waned the young Crab supernova would have dominated the predawn sky.
6. The inner solar system is still showing a lot of linear structure this month, with Venus and Mars on the far side of the sun, while Mercury is on the same side of the sun as Earth. As seen from Earth, Mercury slips between Earth and sun at 7 a.m. It will emerge as a morning planet before the end of this month.
8. We think of a full moon as the prettiest lunar phase, but unless you're a night owl, you probably notice and appreciate the first quarter phase even more. First quarter phase occurs today at 7:53 a.m., at which time the moon has completed the first quarter of its Earth-centered orbit. At this phase, the moon lags behind the sun by 90 degrees and rises about 6 hours after the sun. That places the quarter moon high above the southern sky in early evening. Tonight's full moon graces the constellation Virgo. The moon is pretty near Virgo's brightest star, Spica, one of the brightest stars in the sky.
10. A new comet was discovered last year by the Lincoln Laboratory Near Earth Asteroid Research collaboration (LINEAR) when it was still five times as far from the sun as Earth is. One of the nice surprises for this summer is that Comet LINEAR will be fairly bright and well-positioned for northern hemisphere observers. Comets, especially newcomers to the inner solar system, are notoriously unpredictable but this one is predicted to be nearly visible to the naked eye from July 21 to 25. That's also the week that LINEAR will cross just under the cup of the Big Dipper.
13. If you look straight up in the early evening, the constellation you see should be Hercules. Hercules is best recognized for the boxy shape that corresponds to the hero's body. Another hero, Bootes the hunter, is headed for the western horizon. Two constellations in the east will bring the best of the summer Milky Way to the zenith in a couple of hours, Lyra and Cygnus. Lyra, or the harp, is a small parallelogram-shaped constellation with one of the brightest blue stars in the sky, lovely Vega. Cygnus, the swan, also is called the northern cross.
16. Twice during the year, the moon crosses Earth's orbital plane while it is at new and full phase, so that two or three eclipses are usually clustered within a lunar month. The moon will pass through full phase and Earth's shadow at 8:55 a.m. We are several time zones away from the locations in Hawaii and Asia that will have the best view of this total lunar eclipse.
20. Today is Space Day, marking the anniversaries of several tremendously successful events in U.S. space program history. We should all remember July 20, 1969, when Neil Armstrong and Buzz Aldrin landed the Eagle module of their Apollo 11 spacecraft near the moon's Sea of Tranquillity. Eight years later, the unmanned Viking I spacecraft landed on the surface of Mars. Viking sent back images of a rusty soil and pink sky later that day. Finally, in 1997, the Mars Pathfinder landed and dispatched its rover, Sojourner Truth, to image and sample its Martian surroundings.
24. What is the sky like at 6 a.m.? Pretty bright, unfortunately. The sun should be just ready to cross the horizon. Mars is uncomfortably close to the sun's position but you might be able to spot Mercury a hand's breadth above the eastern horizon. Jupiter and Saturn are much more comfortably placed. The moon is at last quarter phase at 6:02 a.m., right about the time when it crosses the constellation border between Pisces and Cetus. By tomorrow, the moon will be nearer one of the brighter stars of Cetus, the whale or sea-monster constellation. Menkar is fairly bright and rather red; its name refers to the nose of the monster.
26. If you want to see bright, beautiful planets this month, you pretty much have to get up early. At 5 a.m., the sun is still well below the horizon so you can easily see Jupiter, the waning moon and Saturn fairly well above the eastern horizon. This is a pretty gorgeous conjunction of objects, made even more enjoyable by the recognizable backdrop provided by the constellation Taurus. The the Pleiades star cluster should be quite near this tight trio.
27. Mercury is a tough planet to observe, as it is always near the sun and bathed in twilight. Today, Mercury is as far from the sun as it will get for a while, and that's not terribly far. Mercury rises at about 5 a.m., only 80 minutes ahead of the sun. Saturn, Jupiter and the waning moon are to Mercury's upper right as you look east. If you're not sure you've spotted Mercury, you might try again on the morning of July 29 when the waning crescent moon will be very close to it.
30. The moon will be at new phase for the second time this month at 9:25 p.m. Although the moon has nearly moved out of the range of conditions that permit eclipses, there will be a modest partial eclipse visible in the northwestern states of the U.S., all of Alaska and well into arctic Canada.