Skylights featured five times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
, 5
Photo of the Week.. A brilliant "subsun," caused by
reflection of sunlight from invisible ice crystals below a high-
flying airplane, appears to float in clear air above a river gorge
in California, the river's waters also reflecting sunlight. This
picture was featured on the Earth
Science Picture of the Day
Astronomy news for the week starting Friday, May 20, 2005.
The Moon rolls through its glorious full phase on Monday the 23rd,
shortly before moonrise in North America, meaning that the full
Moon will rise just after sunset. Lovely as it is, the full Moon,
or near-full-Moon, is the bane of both amateur and professional
astronomers. It is so bright that it washes out fainter starlight.
Professional observatories in fact are divided into "dark runs"
between third and first quarters and "Moon runs" between first and
third (where full Moon is second base...), during which time one
can observe only brighter objects, and then usually
spectroscopically. Even if one is into lunar studies, at full
Moon, crater shadows are hidden such that little geological
(selenological?) relief is seen. The beauty of the lunar disk is
nevertheless there. The early part of the week then sees the last
of the
waxing gibbous phase, while the later part sees the beginning
of the waning
gibbous.
The Moon
makes two passages of note. On the night of Friday May 20,
the waxing gibbous will appear just to the east of first magnitude
Spica in Virgo, the Moon, the star, and the planet Jupiter (well to the west of Spica) making a fine sight.
Then the morning of Tuesday the 24th, only half a day past full
Moon, the Moon will not only pass, but will occult (cover over),
first magnitude Antares in Scorpius for most of North America.
Times vary, depending on location. "Ingress," or disappearance,
ranges from about 4:20 AM EDT in the east (in twilight) through 3
AM CDT in the midwest, 1:20 AM MDT in mountain country, to 11:50 or
so PM PDT on the west coast. "Egress," re-appearance, in the east
is rendered mostly invisible because of the bright sky. For the
three other regions it will take place about 4 AM CDT, 2:30 AM MDT,
and 1:05 AM PDT. Because of the very bright Moon, the event will
require a telescope or larger binoculars. Knowing the rate of
motion of the Moon, astronomers can measure the angular diameters
(and with distances the physical diameters) of stars by how long
they take to disappear behind (or reappear from behind) the lunar
edge.
Saturn and Jupiter still dominate the evening sky, Saturn (in
Gemini) to the northeast and
setting at midnight, Jupiter (in Virgo) to the south, setting at
3:30 AM just an hour after Mars (in Aquarius, below the "Circlet" of Pisces) rises. Though
Venus
is beginning to make its appearance in the west northwest, it is
still very low and hard to find.
Virgo, crossing the meridian
between about 9 and 10 PM, is among the largest constellations of
the Zodiac (if not of the whole
sky) and contains one of the hottest of first magnitude stars, the
close double star Spica, The star
lies at the center of a loose ring of other constellations, Corvus (the Crow) to the west, the
tail of Hydra (the Water Serpent)
due south, Libra (the Scales) to
the east, and Bootes (the
Herdsman) with Arcturus rather
well to the north.
