Skylights featured on Astronomy Picture of the Day

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Skylights featured five times on Earth Science Picture of the Day:
1 , 2 , 3 , 4 , 5

Venus and Moon

Photo of the Week.. The waxing crescent Moon (Earthlight on the nighttime side faintly visible) made a fine passage above Venus the night of July TK, 2005. Mercury is faintly visible down and to the left of Venus. Mercury was seen better earlier in the week.

Astronomy news for the week starting Friday, August 5, 2005.

The Moon, having passed its new phase on Thursday, August 4, completely spans the week in its waxing crescent phase (see the photo of the week above), the first quarter not reached until Friday the 12th about the time the sky darkens. While it is technically possible to see the slim crescent in western twilight the evening of Friday the 5th, first visibility is not really reached until the evening of Saturday the 6th. As the crescent grow over successive nights and the Moon climbs higher in the darkening evening sky we first begin to see the Earthlight on the lunar nighttime side and then watch it fade away.

The waxing crescent will provide a pair of treats as it passes the two brightest planets. On the evening of Sunday the 7th, watch in bright western twilight for a classic and spectacular pairing of the crescent with brilliant Venus, the Moon immediately to the right of the planet. As seen from Alaska and northwestern Canada, the Moon actually occults, or passes over, Venus. The following night you will see the Moon between Venus and Jupiter, which in twilight lies in the southwest and much higher than Venus. Then the evening of Tuesday the 9th, the fattening crescent takes on Jupiter, the planet seen above and to the left of the northern lunar horn. Note the nice triangle with Porrima, Gamma Virginis, the star lying up and to the right of the Moon. Again, the Moon will occult the planet, but as seen only from the southern Indian Ocean and parts of Antarctica. (Such occultations are not seen all over the globe because of the lunar "parallax." The Moon is so close to us, just over a quarter million miles away, that its position against the more distant sky depends on the location on Earth: as you move in one direction, the Moon appears to move in the other, much as an outstretched finger shifts when seen with one eye and then the other.)

Venus sets in twilight, and Jupiter (still to the west of Spica) goes down around 10:30 PM Daylight Time, while Mars does the reverse, and rises brightly an hour later south of the classic figure of Aries. Additional planetary news involves opposing events. On Monday the 8th, Neptune, in Capricornus, passes opposition with the Sun, while on Friday the 5th, Mercury passes inferior conjunction with the Sun, when it is more or less between us and the Sun and thereafter becomes a morning object.

August is "meteor month," when we celebrate the famed Perseid meteor shower, which will be at its best for North America the mornings of Friday the 12th and Saturday the 13th. The shower results from the shed debris of Comet Swift-Tuttle hitting the Earth's upper atmosphere. With the Moon out of the way, under a dark sky we should have a nice show, the meteors tyically coming at a rate of about one a minute.

If you want to see the newly discovered "tenth planet," which seems to be slightly larger than Pluto, you will need a good-sized telescope, as at nearly magnitude 19 it is over 90,000 times fainter than the human eye can see. At a current distance of 96.6 AU, 2003 UB313 (no proper name yet) is the most distant Solar System object ever observed. Near its aphelion point, the body has an orbital period of 557 years, averages 67.7 AU from the Sun, and on its looping, eccentric orbit, comes as close as 37.7 AU, closer than Pluto. Like Pluto, it seems to be a large "Kuiper Belt" object (part of a debris ring outside the orbit of Neptune) that was kicked into its big and highly inclined orbit (it is now in central Cetus, well off the ecliptic) by Neptune in the early days of the Solar System. Pluto, and Triton, the large moon of Neptune, are similar.

The season features the southern sky, with Scorpius riding the meridian to the south as the sky darkens, and Sagittarius with its brilliant (at least in a dark sky) Milky Way transiting the meridian a bit later. Look for the red supergiant Antares, which lies at the Scorpion's heart, for the trio of stars up and to the right of it that marks the beast's head, and then the graceful curve of stars that (for northerners) descends to the horizon and mark the body.
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