This is the Skywatch Line for Monday, Labor Day, and Tuesday, September fifth and sixth.
The Sun sets at 7:22 PM; night falls at 9 PM. Dawn breaks at 4:47 AM and ends with the Sun rising at 6:26.
The four-day-old Moon rose in Virgo during Monday morning; civil twilight finds it moderately low in the southwest sky. It blazes at minus 7 magnitude, appears about 20 percent illuminated and sets at 9:38 PM. Tuesday sees the Moon in Libra, closer to the South, brighter and larger; it sets at 10:10 PM.
Venus and Jupiter, also in Virgo, form a widely spaced pair also in the southwestern sky. Venus is the brightest at magnitude minus 3.9 and appears almost “full” in telescopes. Jupiter, nine degrees below Venus, is bright, but very close to the horizon. Both set by 8:19 PM.
The celestial triangle of Saturn, Mars and Antares is temporarily reinstated. Moderately high in the southwest, Saturn forms the western part of the triangle. It glows at zero magnitude and still remains a dramatic sight in a telescope. Mars, which lies about eight degrees east of Saturn, is a bit brighter at minus 0.2 magnitude and appears about 85 percent illuminated. Soon, the triangle will evaporate. Both planets are moving eastward, with Mars being the fastest. The red star Antares lies stationary about seven degrees below both planets. The triangle sets by 11:13 PM.
While the bright planets in the southwest were distracting us, eighth magnitude Neptune rose in Aquarius at about 7:11 PM. It is still near the brighter star Hydor, also called Lambda Aquarii. Uranus also rose in Pisces at 8:43 PM. Although brighter and slightly larger than Neptune, Uranus is still difficult to locate. Sky charts from astronomical magazines and websites are necessary. Neptune is best seen at 12:42 AM; Uranus is best observed at 3:21 AM. Both remain up the rest of the night.
The past week witnessed four tropical storms threaten the US – two hurricanes in the Pacific, hurricane Hermine and a tropical depression in the Atlantic. As bad as these tempests were, they are small compared to storms on other solar system members. The most famous example is the Great Red Spot on Jupiter. This tempest has been continuously observed for three hundred years, and is probably older. The Great Red Spot is actually a high-pressure hurricane, larger than the Earth. Recently, astronomers discovered that the Great Red Spot is gradually shrinking; the cause is unknown. Jupiter experiences ordinary thunderstorms that radio amateurs can pick up on their ham radios. Saturn also periodically displays cyclones. In 2010, amateur astronomers discovered the Great White Spot, a thunderstorm over 100 times larger than earthly ones. Uranus displayed an outburst, with 500 miles-per-hour winds, that lasted five years. Neptune also periodically displays severe weather; the Hubble Telescope saw a storm last year and again this May. Finally, our Sun is constantly flaring and sending out clouds of charged particles. Major corporations and governments retain solar scientists to predict Space Weather, so that satellites, communications and astronauts are protected.