June 2011

Stargazing a challenge during long summer days

Those who enjoy daytime outdoor recreational activities such as camping, hiking and baseball look forward to the long days of the summer season. Stargazers, however, must wait until darkness finally descends later at night in order to pursue their hobby. Here in the Thunder Bay area darkness comes even later due to our location at the western edge of the Eastern Time Zone. Having to move the clocks forward one hour last March to Daylight Savings Time also delays the onset of the darkness of night even later. To do any observing this time of year you must wait at least 1 1/2 hours after sunset to allow the background sky to become sufficiently dark to do any worthwhile stargazing for faint objects (deep sky) such as star clusters, nebulae and galaxies.

Most planets are brighter than deep sky objects so it is usual to start observing them about an hour after sunset. The only planet favourably placed in the evening sky presently is Saturn. At the beginning of June Saturn can be seen well up in the south once the sky has darkened. Its yellowish glow at magnitude 0.8 makes it stand out amongst the stars in the constellation of Virgo. It is slightly brighter than Virgo’s brightest star, blue-white Spica (magnitude 1.0).

The motion of Saturn is easily seen as it moves slowly amongst the background stars. Observers have watched Saturn over the past few months as it moved slowly westward (retrograde) towards the fainter star Porrima (magnitude 2.7). The Ringed Planet will be a mere 1/4 degree (half the width of the Full Moon’s apparent diameter in the sky) from this star on the night of June 10. By June 14 the planet ceases its westward trek amongst the stars and resumes its normal (direct) eastward motion.

Porrima, or Gamma Virginis, is the second brightest star in Virgo shining at magnitude 2.7. This star is actually a double star system. In this system there are two yellowish stars revolving around each other with a period of 171 years. The star system is close to us at a distance of only 39 light years. A light year is the distance light travels in one year (almost 9.5 trillion kilometers). The orbit of the companion star around the primary star is very elliptical. They were closest together in 2005 when even larger telescopes could not resolve the two stars. Now as they move farther apart it is easier for smaller scopes to split the pair. When the pair is furthest apart (around 2087) even a set of binoculars will be able to separate the two stars.

Comet C/2009 P1 (Garradd) continues to brighten as predicted. Last month it was a very dim object glowing at magnitude 12. Latest observations have the comet brightening slightly to around the ninth magnitude. At this rate the comet is predicted to reach the sixth magnitude later this year. Magnitude six objects can be seen with the unaided eye under clear and dark sky locations away from urban light pollution sources. I will update observers as to the comet’s progress over the next few months.
The waxing crescent moon can be seen to the left of the stars of Castor and Pollux in Gemini on June 5 after sunset. On the night of June 7 the moon will be to the lower left of the star Regulus in the constellation of Leo. The waxing gibbous moon will be situated just below Saturn and the star Spica in Virgo after sundown on June 10. Look for the near full moon to the left of the reddish star Antares in Scorpio around midnight June 14.

The astronomical marker for the beginning of summer season in the northern hemisphere is the summer solstice. This event marks the beginning of summer in the northern hemisphere and the start of the winter season for those who live in the countries south of the equator. The summer solstice marks the longest days (and shortest nights!) of the year. This year the summer solstice occurs on June 21 at 1:16 pm EDT.

Clear Skies
Ted Bronson