Photo of the Week.Sirius and Canis Major. Shining through light clouds, Sirius is
surrounded by a rare sight for a star, a diffraction corona of the
kind normally seen around the vastly brighter Moon. See it at full resolution.
Astronomy news for the three-week period starting Friday, May
29, 2009.
The next Skylights will appear Friday, June 19. Thanks for your
patience.
During our extended Skylights period, the Moon runs through
a good fraction of its phases, beginning with first
quarter the night of Saturday, May 30 (preceded by one night of
a fat waxing crescent). After almost a
week waxing in the gibbous phase, the Moon
then passes through full
during the day on Sunday, June 7 (thus appearing a bit after full
by Moonrise that night). The waning
gibbous is then followed by third
quarter on Monday the 15th. We finally finish the interval
with the Moon in the waning crescent as
it heads toward new on Monday the 22nd. The Moon passes apogee, where it
is farthest from Earth, on Wednesday the 10th.
As it makes its lunar rounds, the Moon puts on an especially nice
display with stars and planets. It all starts with a bracketing of
Saturn,
wherein the night of Saturday, May 30, the Moon will be seen to the
southwest of the planet and the following night to the southeast of
it. In the "big event," the Moon will then not only pass the bright
star Antares in Scorpius the night of Saturday, June
6, but actually occult it for much of North America, though the
brightness of the near-full Moon and twilight will make it tough to
see and it will really require binoculars or a
telescope. The timing depends on
location. For the eastern two-thirds or so of the US and southern
Canada, the star disappears behind the Moon's leading edge roughly
between 9 and 10 PM Daylight time. Reappearance, visible
everywhere except the far northwestern corner of the US, takes
place about an hour later.
The Moon then takes on the gang of planets that are now hugging the
morning hours and dawn. As the Moon bracketed Saturn the beginning
of our period, it then brackets Jupiter, but lying to the NORTHwest of the
giant planet the morning of Saturday the 13th (the night of the
12th), then to the northeast the following morning/night. Our
three-week journey continues the morning of Friday the 19th with
the Moon making a fine appearance just above Venus and Mars, Mars up
and to the left of its much more brilliant neighbor. More quietly,
Neptune and
Uranus get
passed on the Saturday the 13th and Tuesday the 16th.
Then it's the planets themselves that are on display. The big
event here is the fine conjunction between Venus and Mars that
takes place the morning of Friday the 19th, Mars just two degrees
to the north of Venus, the two rising together around 3 AM. Not to
be entirely outdone, on Monday the 15th, giant Jupiter halts its
eastern motion against the stars that lie along the border between
northeastern Capricornus and
southwestern Aquarius, and begins
its
retrograde trek to the west. As May ends, Jupiter also
formally becomes an evening planet, rising at local midnight (1 AM
daylight), then rising after midnight Daylight Time around Sunday
the 14th.
On Friday, June 5, Venus passes its greatest elongation 46 degrees
west of the Sun.
Then it's Mercury's
turn, the little planet going through its greatest western
elongation on Saturday the 13th. Rising in mid-dawn shortly before
sunrise, the view of Mercury, while never good, improves some as the month
proceeds. Finally, it's back to the evening, when we see Saturn in
the southwest as the sky darkens, the planet still in southeastern
Leo to the east of Regulus. The ringed planet makes
something of a transition when as of around Sunday the 14th, it
begins to set after local midnight, about an hour after Jupiter
rises.
In early evening, the Big Dipper
of Ursa Major rides high,
dominating the sky. It makes a fine transition to Bootes, the Herdsman, which lies to
the southeast of it. Just follow the curve of the Dipper's handle
to bright, orange-colored Arcturus, the northern hemisphere's
brightest star. Then continue the curve down to blue-white Spica in Virgo. To the southwest of Spica you can admire the
small box of stars that makes Corvus, the Crow, while to the southeast of Spica lies
another distorted box that makes most of Libra, the Scales. Then, its off farther into the
southeast to Antares of Scorpius, the star that will be occulted by
the Moon the night of Saturday the 6th.
