Photo of the Week. Yet another summer rose framed by
the blue sky.
Astronomy news for the week starting Friday, April 23, 2010.
The Moon
brightens the evening sky in its waxing
gibbous phase as it heads toward full, that phase reached the
morning of Wednesday, April 28, just about the time of Moonset in
North America, when it will set almost exactly at sunrise. That
night it will rise a bit after the
Sun goes down. Following full, we get a couple days of the waning gibbous, the perpetual tale to be
picked up again next week. On Saturday the 24th, the Moon passes
perigee,
where it is closet to the Earth.
The night of Sunday the 25th, the Moon passes eight degrees south
of Saturn,
which will provide a great way of identifying the ringed planet.
The rather large separation between the two is caused by orbital
tilts. Saturn is close to its maximum angular distance almost
three degrees north of the ecliptic (the apparent path of
the Sun), while the Moon will be near its maximum five-degree angle
south of it.
Placement of the planets allows us to proceed pretty much from
inside out. Mercury,
now gone from the visible sky, passes inferior conjunction with the
Sun, on the near side, on Wednesday the 28th. Venus, on the
other hand, picks up steam. Climbing ever higher into the west-
northwestern evening sky, the brilliant planet is now setting after
the end of twilight, around 10 PM Daylight Time. Which brings us
to Mars.
At twilight's end a bit past
the meridian into the southwest, the
red planet (really more of an orange flavor) is beautifully placed
between Gemini's Castor-Pollux pair and Regulus in Leo and, though fading, is brighter than any of the
three stars. Compare its color to orange Pollux, the left-hand
star of the pair. It finally sets around 3 AM Daylight
Time
Then we go a bit out of order and back to Saturn, which is being
visited by the Moon. Almost exactly between Regulus and Virgo's Spica and on its
retrograde trek against the stars, it passes 2.75 degrees due
north of the Autumnal Equinox on
Saturday the 24th. Transiting the meridian near 10:30 PM, Saturn
does not set until mid-twilight, about the time that Jupiter -- still
a tough find -- rises.
The sky made news the evening of Wednesday, April 14, with a
splashy fireball
meteor. It was most likely a small, uncatalogued visitor from
the asteroid belt a meter or two in diameter. Moving
at ten or more kilometers per second, the meteoroid carved a hot
bright path through the Earth's atmosphere 100 kilometers up,
exploded, then sent a shower of stones to the ground as meteorites.
Such events are completely unpredictable.
As April turns to May, Ursa Major's
Big Dipper circles high overhead
in the late evening. For a minimal test of vision, see if you can
find little Alcor, which is nearly
hidden next to Mizar, the second
star in from the end of the handle. To the south and west of the
Dipper, find three pretty pairs of stars that the Arab's called the
"leaps of the gazelle."
