You are here: Home USNO News, Tours & Events Sky This Week The Sky This Week, 2011 August 30 - September 6
The USNO websites,,,,,, and are undergoing modernization efforts. The expected completion of the work and the estimated return of service is Fall 2020, subject to change due to potential impacts of COVID-19.

The Sky This Week, 2011 August 30 - September 6

Intruders in the night...
 Comet 2009P1 Garradd's motion over 118 minutes is shown in this image taken at Burleith Observatory, Washington, DC by Richard Schmidt on the morning of August 24, 2011.  The telescope was a 32-cm Planewave astrograph.  A Kron-cousins I-band filter was used. The comet is seen moving from SE to NW (left to right).

The Moon returns to the evening sky this week, waxing through her crescent phases as she skirts the southern horizon among the summer’s signature constellations. First Quarter occurs on September 4th at 1:39 pm Eastern daylight Time. Look for Luna about 10 degrees east of the bright star Spica low in the west in the deepening evening twilight on the 1st. On the 3rd she lies among the stars forming the "head" of Scorpius, the Scorpion, about eight degrees west of the ruddy star Antares. On the following night the Moon may be found six east of the reddish star. She ends the week passing above the "teapot" asterism of Sagittarius.

Two celestial interlopers are well worth trying to chase down this week before the light of the waxing Moon brightens the background sky. Both require a visit to a dark location, but many of us will be visiting the shore or the mountains for the summer’s last hurrah. The first object should be visible in a pair of binoculars, while the second will require a small telescope to snare. First up is a comet, known by the prosaic name C/2009 P1 Garradd. Discovered on August 13, 2009 by Australian Gordon Garradd during the course of an all-sky telescopic survey, this cosmic iceball is now passing through the inner solar system. Shining at 8th magnitude it’s too faint to be seen with the naked eye, but it is an easy sight in binoculars, provided you know when and where to look. I watched it over the course of several nights while on vacation as it passed through the stars of the constellation Delphinus. Currently it is moving westward through the stars of the Summer Triangle, which are overhead during the late night hours. A finder chart showing its location over the next two weeks may be found here.

The second interloper requires a bit more skill to find, but doing so will admit you to a small cadre of observers who have seen an individual star in a distant galaxy. This object is a supernova that erupted in the nearby galaxy Messier 101 on August 24th. M101 is a large, "face-on" spiral system located just above and to the left of the bend in the "handle" of the Big Dipper. The supernova, officially known as SN 2011fe, was discovered well before its peak brightness; currently it is at 11th magnitude and brightening, which means it should be visible in telescopes as small as three inches aperture. A finder chart for M101 may be found here, while up-to-date information on SN 2011fe may be found here.

As August melds into September we bid a fond farewell to Saturn, which has entertained us for the past several months. The ringed planet now sets at the end of evening twilight, effectively squelching any useful observations. He will return for another season next year in the spring as his rings continue to open to our line of sight.

In the meantime Jupiter continues his steady march into the evening sky. The giant planet rises at around 10:00 pm by the end of the week, and by midnight he’s high enough to train the telescope on his bright striped cloud tops. The best time to view him is still before dawn when he’s very high in the south. I had my first good view of him while on vacation two weeks ago, and his overall appearance is more like the "Old Jove" I’ve been used to for the last decade or so. Both of his equatorial cloud belts are prominent once again and should be easy to spot in any telescope. Jupiter reaches opposition at the end of October, so we can look forward to a nice long jovian observing season this fall and winter.

USNO Master Clock Time
Javascript must be Enabled