September 2011

Jupiter graces Eastern Sky after Nightfall

The casual observer will notice a brilliant “star” rising above the eastern horizon around 11:00 p.m. at the beginning of September. This bright yellow object is not a star but the planet Jupiter. Its glow at magnitude -2.7 makes it easy to spot amongst the faint stars in the constellation of Aries. As Jupiter approaches opposition the end of next month it will continue to brighten even more. A telescope reveals several features of the Giant Planet. The Galilean moons (Io, Europa, Ganymede and Callisto) can be seen, even with steadily supported binoculars, as they move around the planet. Jupiter’s rapid rate of rotation (under ten hours) gives it a squashed appearance when seen in a telescope. The massive Jovian atmosphere displays two dark bands parallel to a brighter equatorial band readily visible in small telescopes. Use of a 6 inch or larger scope will reveal details within these bands. The Great Red Spot, a storm in Jupiter’s atmosphere, is subtle and is usually difficult to see unless it is facing directly towards Earth. This feature is often on the far side or near the limb (edge) of the planet.

Mars rises around 3:00 a.m. at the beginning of September and can be found in the constellation of Gemini. The two stars of Gemini, Castor and Pollux, are around the 1st magnitude in brightness with Mars being of similar brightness this month. The two stars and Mars will appear to form a straight line about 12 degrees long (about a fist width at arm length) during the nights around midmonth. These three offer a nice colour contrast with Castor a pure white, Pollux as yellowish and Mars reddish-orange. Mars will continue to brighten as it approaches an opposition in early March of 2012.

I have been keeping an eye on Comet C/2009 P1 (Garradd) as it slowly brightens. At this point it can be seen with a small telescope under a dark and clear sky glowing with a modest brightness of seventh magnitude. A dark night sky is essential to see this celestial fuzzball as haze or bright moonlight will tend to mask it from view. On the nights of August 31 to September 3 the comet will pass by the Coathanger Cluster (Collendar 399).

The Coathanger Cluster is a group of ten stars, as its name suggests, is shaped like a coathanger. To find it locate the bright stars of the asterism of the Summer Triangle. An asterism is made up of a pattern of stars that is not a recognized constellation but is a part of one or more constellations. The Summer Triangle contains the brightest stars from the constellations of Cygnus (the Swan), Lyra (the Lyre) and Aquila (the Eagle). A basic star map will make finding these constellations easy. The Coathanger Cluster is located about half way between the stars Vega and Altair in the Summer Triangle.

The first quarter moon can be found to the upper left of the reddish-orange coloured star Antares in Scorpio after sunset on the evening of September 4. A waning gibbous moon resides near Jupiter on the nights of September 15 and 16. A waning lunar crescent moon can be found below and to the right of Mars before sunrise on September 23.

The fall or autumnal equinox this year occurs on September 23 at 5:05 a.m. EDT. This event denotes the first day of autumn for us in the northern hemisphere. Those in the southern hemisphere will celebrate the end of the winter season and welcome the arrival of spring.

To assist amateur stargazers in their quest to navigate the night skies, discover the wonders of the universe, and become familiar with some of the instruments amateur astronomers use I am offering my course Backyard Astronomy – Stargazing for Everyone this fall. It begins September 15 at Confederation College. For more information contact Confederation College.

The Thunder Bay Centre of the Astronomy Society holds monthly meetings at the Shuniah Building of Confederation College. They are held on the second Tuesday of each month (except July and August) at 7:00 p.m. (the room number will be displayed on the monitor inside the building). Interested non-members are always welcome to attend these meetings. For more information visit our website at or call 475-3406.

Clear Skies

Ted Bronson