Skylights featured on Astronomy Picture of the Day

Scout Report Selection Webivore Selection SpaceCareers Selection

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

Cloud Shadows

Photo of the Week.. A high cloud throws yet more glorious shadows into the daytime sky.

Astronomy news for the week starting Friday, August 29, 2003.

The Moon moves through its waxing crescent phase the first part of the week, and reaches its first quarter, where it is 90 degrees to the east of the Sun, on Wednesday, September 3, well before Moonrise in the Americas. With the Sun slowly nearing the autumnal equinox in Virgo, the quarter Moon is nearing the winter solstice in Sagittarius, and will be quite low in the sky for mid-northern latitudes, rising in the southeast after noon and setting in the southwest before midnight. The next first quarter, on October 2, will be slightly more southerly yet.

Following last week's Mars Madness, we now have little Pluto, far out of sight to the naked eye, ceasing its retrograde motion well to the north of the ecliptic in Ophiuchus. Mars of course, despite having passed opposition to the Sun, is still glorious within southern Aquarius, as September begins rising just a hair after sunset and crossing the meridian to the south at local midnight (about 1 AM Daylight Time). The most earthlike of all other planets, Mars has a rotation period just slightly greater than that of Earth, and an obliquity to its ecliptic very similar to ours, resulting in similar seasons, just twice as long, since it takes the planet (half again as far from the Sun as we are) 1.9 Earth- years to make a full circuit of the Sun. Under the summer zenith Sun, the temperature of the thin Martian air (which is mostly carbon dioxide with a little nitrogen thrown in) can hit the freezing point of water.

The only other planet available for viewing is Saturn, which, now rising just before 2 AM, will shortly be making an impact on the night sky. Taking 29.5 years to orbit the Sun, the ringed planet (glorious in even a small telescope) moves slowly against the stellar background, on the average taking some two years to traverse a zodiacal constellation. Having spent the last viewing season wandering through eastern Taurus, Saturn is now beautifully set within the confines of Gemini.

Evening viewing finds the summer stars at their best. Look for the Summer Triangle of Vega, Deneb, and Altair, respectively in Lyra, Cygnus, and Aquila, and if under a dark sky admire the Milky Way plunging down through Cygnus into Sagittarius, which for mid- northerners lies low in the south around 9 PM, the handle of its famed asterism, the upside-down "Little Milk Dipper," sticking into the Milky Stream. From mid-southern latitudes, South America and Australia, Sagittarius and the center of the Galaxy shine gloriously overhead.
Valid HTML 4.0!