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 .


Photo of the Week.. Evening falls quietly as we wait for the stars.

Astronomy news for the week starting Friday, June 27, 2003.

The week begins almost at the new Moon, as the phase occurs Sunday, June 29, just about noon in North America. When the Sun is near its highest point in the sky, the Moon will be just above (to the north of) it, and just missing making a solar eclipse. By the evening of Monday the 30th, our lunar companion will be visible low in the northwest at twilight. The night of Wednesday, July 2 finds the growing crescent just to the northeast of bright Jupiter, the planet that still -- once the Moon is out of the way -- dominates evening skies. Though not for long, as Jupiter is now setting just at the end of evening twilight, and will be getting ever-harder too see.

At midnight Central Standard Time the night of Thursday, July 3 (1 AM CDT the morning of Friday, July 4, 2 AM EDT, 0600 Greenwich Time, 11 PM CDT July 3), the Earth passes the aphelion of its orbit, where it is farthest from the Sun, at a distance 1.7 percent farther than average, 94.5 million miles, 152.1 million kilometers. That we are farthest from the Sun in the middle of summer is a clear indication that the seasons are not caused by variation in solar distance, but instead by the tilt of the Earth's axis relative to the orbital perpendicular, allowing the Sun to shine high first in the northern hemisphere (bringing spring and summer to the north) and then high in the southern hemisphere (bringing spring and summer there, autumn and winter in the north). Since we are farthest to the Sun in southern hemisphere winter and nearest in southern summer (reversed in the north), southern hemisphere seasons are -- all things equal -- more extreme than those in the north, but the effect is lost in that the southern hemisphere is dominated by oceans, which moderate them.

Mars, on the other hand, has no liquid water. Its orbit is eccentric, but otherwise the planet is configured much like Earth. There the southern hemisphere seasons are notably more extreme than the northern (the "snow," frost really, being dry ice rather than water ice). That is something to ponder when watching the brightening planet rise. Now about as bright as the sky's brightest star, Sirius, and moving through southern Aquarius, Mars lofts itself above the southeastern horizon around midnight Daylight Time, and thereafter dominates the morning (brighter Venus rising less than an hour before the Sun and difficult to see).

Find bright reddish Antares of Scorpius beautifully visible low in the south around 11 PM. Look upward to see two heroic figures, first pentagon-shaped Ophiuchus, the Serpent Bearer (wrapped with Serpens), and then Hercules, the strong man of ancient times. Binoculars pointed to northern Hercules will reveal a fuzzy patch, one of the great sights of the northern sky, the globular star cluster M 13, which contains the order of a million stars.
Valid HTML 4.0!