Astronomy news for the week starting Friday, March 4, 2011.
We begin the week with the beginning of the
lunar phase cycle, as the Moon
passes through its new phase, more or less between us and the Sun, on Friday, March 4. At
that time, the near side (that always facing the Earth) is in darkness (and
invisible), and the far side, which
never faces Earth, is in full sunlight. The Moon then spends the
whole of Skylights' week climbing out of western evening twilight
as a waxing crescent, first quarter not reached until the night of
Saturday the 12th. With a clear sky and a flat horizon, you might
get your first glimpse of it in bright twilight the evening of
Saturday the 5th. By the next evening, that of Sunday the 6th, it
will not only be obvious, but will make a fine sight to the right
of Jupiter,
which is going the other way and night-by-night is sinking toward
the Sun. One more evening along sees the growing crescent well
above the giant planet. In the last of lunar news, the Moon passes
its apogee,
where it is farthest from the Earth, on the night of Saturday the
5th.
As noted above, Jupiter is rapidly disappearing from the evening
western sky. By the end of our week, it will be setting by 7:30
PM, just as twilight ends and the sky becomes fully dark. With
Jupiter now moving more rapidly to the east against the stars on
the Pisces-Cetus border, the delay between Jupiter setting and
Saturn rising (still to the northwest of Spica) is squeezing to under half an
hour. The ringed planet is then with us the rest of the night,
crossing the meridian to the south
around 2 AM. Two and a half hours later, up comes
Venus, still well into the southeast. While its rising time
has remained fairly steady at 4:30 AM, twilight has been getting
notably earlier as the Sun moves to the north, such that the
brilliant planet is not as high by the time it disappears into the
brightening dawn. By next week, it will be rising just as twilight
begins to light the sky.
If you love the winter stars, you need look ever earlier. Orion is now crossing the meridian
just before 7 PM, followed by the star Sirius (brightest in the sky) an hour
or so later, with Gemini, far to
the north, doing about the same. Coming up are the stars of
spring, which include that great harbinger of warmer times, Leo, following behind Gemini (Cancer in between) well to the west of
Saturn.
