Photo of the Week. The top of the 22-degree halo around the Sun, caused by refraction of sunlight in
high ice-crystal clouds.
Astronomy news for the week starting Friday, July 18, 2008.
The Moon spends
the entire week in the waning gibbous
phase following full, which it passed
the morning of Friday, July 18, the gibbous ending at the third quarter, which it will hit on Friday
the 25th about the time of Moonset in North America. The entire
week is also spent with the Moon climbing northeasterly along (or very close to)
the ecliptic, starting out
east of Sagittarius and ending in
eastern Pisces to the northeast
of the Vernal Equinox. As it
travels along, the Moon passes just to the north of Neptune on
Sunday the 20th, while two days later it similarly runs well north
of Uranus, both events out of sight.
For some time now, the lunar orbit has been tilted just right such
that the Moon regularly occults (passes in front of)
Neptune, and this week's passage is no exception, the event
occurring in east Asia and Alaska (during daylight). The farther
out from the Sun, the slower the
planet. Neptune has been stuck in easTern Capricornus to the north of Deneb Algedi (Delta Capricorni)
for some time now, while somewhat faster-moving
Uranus, steadily pulling to the east of Neptune, lies in
eastern Aquarius just barely south
of the border with Pisces.
The sky is becoming bereft of bright planets.
Mars and
Saturn (Mars now well to the east of the ringed planet, both
east of Regulus) now set just
after the end of evening twilight, and are harder and harder to
find.
Venus is not yet high enough for western evening viewing, while
in the morning, Mercury rises far too late in twilight to see. That
leaves us with the King of the Planets, Jupiter, which -- except for dim Uranus and Neptune -- has
the sky to himself. Already well up the southeast at the end of
twilight, the giant planet transits the meridian low to the south (for mid-
northern latitudes) in northeastern Sagittarius around midnight
Daylight Time, and does not set until twilight brightens the
eastern sky.
The Season of the Dragon is upon us, as in early evening Draco stands high in the northern
sky, most of the huge constellation circumpolar and perpetually
visible from mid-northern latitudes. While the Big Dipper's front bowl stars
famously point at the North Star
(Polaris) at the end of the Little Dipper's handle, on the way
they also more or less point to Giausar (Lambda Draconis) at the end
of the Dragon's Tail, while Draco's squarish head falls between the
Pole and Hercules, which lies just
to the west of brilliant Vega.
