Photo of the Week. Sunset through a tunnel of
clouds.
Astronomy news for the two-week period week beginning Friday,
March 9, 2007.
Skylights is presented two days early; that for Friday, March 2 is still available.
Skylights will resume its normal weekly schedule on March 23.
We begin the fortnight with the Moon almost to the last quarter, that
phase reached on the night of Sunday, March 11, a date that also
marks the new beginning of Daylight
Savings Time in the US. The Moon will also then make a fine
sight in Scorpius just to the east
of Antares, with bright Jupiter
to the northeast of it.
Then the Moon wanes in its crescent
phase towards new, which is passed during the night of Sunday
the 18th. The morning of Monday the 12th finds it to the southeast
of Jupiter, while the following morning it will be within the
"Teapot" of Sagittarius. Then the
morning of Thursday the 15th, the crescent will appear to the west
of Mars, while the
following morning it will have shifted to the other side, the
pairings visible in twilight, which makes Mars still difficult to find.
The morning of Friday the 16th, the Moon will be to the west of Mercury, while the
following morning it will be to the east. Look then the evening of
Tuesday the 20th to see the waxing
crescent Moon in western twilight below (to the west of)
brilliant Venus
. By the following evening, the relation will be reversed,
with the growing crescent now to the east of the planet.
Eclipses often come in pairs. Lunar
eclipses are preceded or followed by solar eclipses (if
conditions are right for one, they are right for the other). The
past full Moon saw an eclipse, and so will this new Moon as it
passes against the Sun. But this solar eclipse is only partial (the Moon never
fully covering the Sun), and unfortunately for North America
visible only throughout Asia.
But don't be sad, since there is another big event. On the evening
of Tuesday the 20th, at 7:07 PM Central Daylight Time (8:07 EDT,
6:07 MDT, 5:07 PDT), the Sun will cross the Vernal Equinox in Pisces and
spring will begin in the northern hemisphere, fall in the
southern. On that date (barring the effects of the Sun's finite
angular diameter, refraction in the Earth's atmosphere, and
twilight), days and nights will be equal at 12 hours each, the Sun
will rise due east and set due west, will rise at the north pole,
set at the south pole, and be overhead along the Earth's equator.
Back to the planetary sky, Venus sets ever later, by the middle of
our fortnight not until 10 PM Daylight Time. Saturn (to the west of
Regulus) transits the meridian to the south only half an hour
later, while Jupiter rises just before midnight Daylight Time. As
the giant planet fades into dawn, it finally makes it to the
southern meridian. Mars's rising still tracks the onset of twilight.
Mercury then takes the morning stage, passing greatest western
elongation (28 degrees to the west of the Sun) on Wednesday, the
21st, giving us a fine opportunity to see the elusive
planet.
As winter turns to spring, Orion
and his gang shift well into western skies. Look for the great
stack of them that starts with Auriga (the Charioteer) far to the north. Then plunge
south through Orion himself, Lepus (the Hare), and triangular Columba the Dove. To the west, Eridanus (the River) winds into twilight, while down
and to the left of him sparkles Sirius, the Dog Star.
