Astronomy news for the week starting Friday, May 4, 2001.
The Moon approaches full the early part of the week, passing that
brilliant phase on Monday May 7th among the dim stars of Libra,
thereafter waning through gibbous, rising after sunset. Sending so
much sunlight back to Earth, the full (or near-full) Moon is so
bright that the surrounding stars are all but invisible.
In eastern dawn, Venus also passes through its greatest possible
brightness, on Friday the 4th, the planet shining brightly amidst
the equally dim stars of Pisces and very close to the vernal
equinox, the point on the celestial equator passed by the Sun on
the first day of spring. A view through the telescope shows Venus
as a large crescent. Though we see only a small section of Venus's
daylight side, its proximity to us still throws a maximum amount of
sunlight in our direction. The observations of Venus's phases was
one of the key proofs to Galileo that Copernicus was right, that
the Earth really does go about the Sun.
Western twilight holds the disappearing treasure of bright Jupiter,
Saturn, an hour to the west and in a bright sky, difficult to view.
If you can find it, perhaps you can also find Mercury down and to
the right early in the week. Jupiter will soon follow into near-
invisibility. Brightening Mars, however, makes up the difference,
as it now rises in Sagittarius around 11:30 PM Daylight Time.
Mimicking Venus as a celestial marker, Mars lies only a couple
degrees above the center of the Galaxy, the center of the Milky
The range of celestial brightness is astonishing. As bright as
Venus may appear to us, the full Moon is 1000 times brighter, and
the Sun a million times brighter yet (so bright as to be able to
damage the eyes). Venus, however, is at maximum 15 times brighter
than the brightest star, Sirius, and a remarkable 25,000 times
brighter than the faintest star we can see without optical aid.
With telescopes the range is even more astonishing: the Hubble
Space Telescope can go another 2.5 billion times fainter!
Two other items of note include Neptune, which begins retrograde
motion in Capricornus on Thursday the 10th. The most distant large
planet, Neptune is now 90,000 times fainter than Venus, and
requires a telescope to see. The bright Moon will unfortunately
wash out one of the year's better meteor showers, the "Eta
Aquarids," which will peak the morning of Sunday, May 5. The
debris of Halley's Comet, the shower typically produces some 30
meteors per hour in a dark sky.
In spite of the Moon's brightness, look to the south in late
twilight to find the great figure of northern spring, Leo the Lion,
the bright star Regulus at the end of the "Sickle" that makes the
great beast's head.