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 not yet!
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.
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
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 happen!
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.
For your own monthly star chart, you can direct your web browser to
http://www.skymaps.com. You will find extensive descriptions of what's worth
looking for, and you can download and print a single copy for your personal use.