August 13, 1999
4. We tend to think of the identity of constellations as an immutable heritage, passed down from classical times. Some of the heritage of Egypt, Greece, Babylon and Rome persists in the names we give to regions of the sky, but names, boundaries and even identities of star groups are as fluid as any other human activity. Southern constellations were "discovered" and named as European explorers first saw the southern sky. Birds did fairly well in those days (constellations Pavo and Tucana) as well as contemporary instruments (Telescopium, Microscopium and Octans).
8. A conjunction refers to a close coincidence in the apparent positions of two celestial objects. We realize that these objects (the moon and a bright star, for instance) are typically at vastly different distances, so "coincidence" is the appropriate word. Because these near-lineups occur at a particular moment in time, some parts of the world will be more lucky than others. The bright star Regulus is near the moon this morning, but both are so close to the sun that safe observation of this conjunction in Leo is inadvisable from all locations.
9. The moon shares the sun's patch of the sky today, arriving at new phase at 5:02 this afternoon. A new moon means a new month for many traditional calendar systems; the new moon of September signals the beginning of the Jewish New Year. Your calendar may list September 11 as the date of Rosh Hashana, but its celebration and the new lunar month actually begin at dusk the evening before.
12. President Kennedy's bold commitment in 1961 to a manned landing on the moon by the end of the decade was indeed an audacious goal. The U.S. space program had been plagued by crashes and failures while the Soviet space program followed its 1957 Sputnik success with a number of triumphs. The Soviet spacecraft Luna 2 became the very first manmade object to hit the moon on this date in 1959.
14. If you look southward in the mid-evening, you should be able to see Mars, the only bright evening planet this month. You'll also see Mars' stellar "alter-ego," the bright star Antares. Antares is the brightest star in the zodiac constellation Scorpius. It has a similar color to Mars and although not as bright as Mars is at present, it is certainly competitive. Antares' name ("not Ares") warns us not to confuse it with the red planet whose Greek name is Ares.
17. Earth's moon is at first quarter phase at 3:06 this afternoon. There are many other moons in the solar system and William Herschel seems to have discovered a fair share of them. The great astronomer, who first gazed on Uranus in 1781, found one of Saturn's larger moons on this date in 1789. Herschel's telescope was not strong enough to see one of Mimas' oddest features, revealed in the stunning images sent back by the Voyager II spacecraft - a crater covering one-fifth the diameter of the moon.
22. Tomorrow brings the autumnal equinox at 6:31 a.m. It is a prejudice of the northern hemisphere to accord more importance to the March equinox than the September event; astronomically, these events are mirror images of each other. The moment of equinox describes a time when a line from the Earth's center to the sun's would pass exactly through Earth's equator. The hours of day and night are evenly divided everywhere on the globe today.
23. If you look toward the south in the mid-evening, the zodiac constellations Aquarius, Capricornus and Sagittarius arc above the southern horizon. With the aid of a small telescope and good charts, you would find the planet Neptune on the western border of Capricornus. The eighth planet was first seen on this date in 1846 by astronomers Johann Galle and Heinrich d'Arrest at the Berlin Observatory. Other astronomers had predicted Neptune's position, but the honor goes to these two scientists who had the best charts.
24. This summer has provided a great opportunity to remember the highlights of the manned lunar missions of the late 1960s and early 1970s. One issue of great concern at the time was the possibility of contamination of Earth life by returning astronauts or lunar materials. Some famous germ-free research facilities were developed to prevent any possible "immigration" of extraterrestrial microbes, as well as to keep lunar samples free of Earthly contamination. The very first lunar material was returned on this date in 1970 by a Soviet craft, the Luna 16.
25. The full moon nearest the equinox of autumn is still called the harvest moon even if farmers don't need its mellow light as much as they used to. You can catch the harvest moon as it arrives at full phase at 5:51 this morning. It should be a lovely sight, with Jupiter and Saturn following the moon toward the western horizon while Venus lights up the eastern sky in advance of the sun.
26. Always beautiful, Venus will reach its greatest brilliancy today. This greater brightness results from Venus being very close to Earth, bringing it nearly between the Earth and sun. This also means that Venus has a crescent shape when it is its most brilliant. At its brightest, Venus outshines a hundred bright stars.
27.Even as late as 7 a.m., the sun is still patiently below the eastern horizon and the west presents the terrific trio of Jupiter, Saturn and the nearly-full moon. You can observe the moon's progress through the zodiac constellations of Pisces this morning as it nears Jupiter, past Saturn in Aries tomorrow morning and on into Taurus on September 29.
30. We think of Orion as a winter constellation, meaning that it is conveniently positioned in the winter evening sky, but this very recognizable constellation rises several hours before sunrise at this time of year. Henry Draper must have stayed up all night to obtain the first photograph of the Orion Nebula on this date in 1880; Draper, a physician in suburban Boston, was also a fine amateur astronomer and possessed one of the world's largest telescopes.