August 2006 Sky from the Keeble Observatory
Last month we told you about a pair of storm systems on Jupiter
that were about to “collide.” The Red Spot, a southern
hemisphere storm which is three times the size of Earth and which
has persisted for at least 350 years, was to pass near a smaller
storm known jokingly as “Red Jr.” This storm is only
the size of Earth, but was of interest because it recently changed
color from white to red, matching whatever peculiar chemistry is
going on in its bigger brother. Speculation of what would happen
ranged from the storms merging, with the Red Spot essentially cannibalizing
the smaller spot and absorbing its atmospheric energy, to nothing
at all happening. It appears that nothing has happened, at least
The accompanying false color image is in the infrared, taken with
the Gemini North Telescope on Mauna Kea in Hawaii. The two “red”
spots appear white here because the cloud tops in the storms are
higher and cooler than the surrounding cloud deck.
Image courtesy AURA/Gemini.
The Gemini observatories deploy a matched pair of large telescopes.
They are an international project, managed by the Associated Universities
for Research in Astronomy (AURA) and partially funded by the National
Science Foundation. Governments involved include the US, UK, Canada,
Chile, Australia, Argentina, and Brazil. Astronomy is truly an international
endeavor, and rightly so. Gemini North is in Hawaii, while Gemini
South is high in the Chilean Andes at Cerro Panchon. Each telescope
has a primary mirror 8.1 meters in diameter, capable of capturing
nearly a million times as much light as the unaided eye. The mirrors’
precise shape is controlled by computer, flexing the mirror to adjust
for atmospheric turbulence which otherwise would tend to smear out
the image. As a result of this technique of “adaptive optics,”
these ground based telescopes are capable of images which match
the sharpness of those obtained by Hubble Space Telescope, which
orbits above virtually all of Earth’s atmosphere.
Speaking of Hubble, observers had a scare last month when the main
instrument, the Advanced Camera for Surveys, shut down because of
a failure in its power supply. Fortunately, within a week ground
controllers were able to restart the camera using a backup power
supply. One of the remaining Shuttle missions before retiring the
fleet in 2010 is tentatively scheduled to visit the space telescope
for a final round or repairs and instrument upgrades. If subsequent
flights go as smoothly as last month’s Discovery mission to
the International Space Station, the Hubble repair mission may actually
Lunar phases for August: First Quarter on the 2nd, at 4:46 am;
Full Moon at 6:54 am, on the 9th; Last Quarter on the 15th, at 9:51
pm; New Moon on the 23rd, at 3:10 pm, and a second First Quarter
on the 31st, at 6:56 pm.
Mercury returns to the predawn skies, though it starts the month
very low to the horizon at sunrise. Venus is brighter, and rises
about an hour before the Sun graces the horizon. By the 12th, rapidly
moving Mercury will nearly catch up to Venus, which is beginning
to move back towards the Sun; they’ll appear less than 2 degrees
apart on that morning. Then both will drift back into the Sun’s
glare by the end of the month. Saturn also returns at mid-month.
It will pass Mercury on the 20th, then Venus on the 26th.
Jupiter remains visible in the evening, beginning the month about
35 degrees above the horizon to the south southwest right at twilight.
That bright star to the right of Jupiter is Spica. The Moon will
pass Jupiter – look for it below and to the right of Jupiter
on the 1st, then below and to the left on the 2nd. Recall that the
Moon orbits Earth once each month, so it drifts to the east (relative
to the background stars) almost 13 degrees per day. Jupiter takes
12 years to return to the same position relative to the stars. Mars
starts the month low to the west at sunset, but it may be hard to
pick out against haze and ground clutter. The Sun’s eastward
drift across the background stars will bring it closer to Mars as
the month progresses – Mars’ general eastward drift
is at about half the speed of the Sun’s.
Our overhead look at mid-month, about two hours after sunset, finds
the bright star Vega near zenith, and the Milky Way dividing the
sky roughly NNE to SSW, with a slight bow to the east. Starting
at its northern point, we see the familiar crooked W of Cassiopeia
about 25 degrees above the horizon. Following the Milky Way, we
turn towards the east northeast to find Cygnus at about 65 degrees
above the horizon. In this orientation, it’s clear why this
constellation has been named the Swan. The bright star at the “tail”
is Deneb, the fainter star at the head is Albireo. Cygnus lies in
the direction towards which the Sun is orbiting in the plane of
the Galaxy. Turning to the southeast, still along the Milky Way,
the next bright star we encounter is Altair, in the constellation
Aquila – the Eagle (this one’s not so obvious!). Near
the southern end of the Milky Way’s arc across our sky, we
find Sagittarius low to the horizon. This constellation marks the
direction towards the actual center of the Galaxy, 90 degrees from
Cygnus. Above Sagittarius and to the south southwest we find bright
red Antares, in the constellation Scorpio – the Scorpion.
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