Summer solstice, the longest daylight of the year, occurs on June 21. This is also the shortest night of the year, a sadness for us northerly star gazers. Still, the weather is warm, the lightning bugs twinkle in the trees and bushes, and the summer starscape is quietly beautiful.

A few minutes past 6 PM EDT on 5 June 2012, there will be an astronomical event which will not happen again until 10-11 December 2117. This rare event is a transit of Venus across the Solar disk. A transit is a type of eclipse. But unlike a typical eclipse, where the eclipsing object can block the entire Sun, a transit blocks only a small fraction of the Sun. To learn more about transits in general, and this transit in particular, come to the talk at the Venus Transit Party, or check some of these Venus Transit resources.

Evening Sky: Mars and Saturn are still high in the sky towards the south-west. At magnitude +0.5, they both outshine the nearby bright star Spica in Virgo. Towards the middle of the month, Mercury starts a month-long evening apparition. In the last half of June, Mercury sets about 1.5 hours after sunset, towards the West-Northwest.

Pre-dawn Sky: For those who out before dawn, the morning sky holds some treats. Jupiter has emerged from behind the sun, and will rise about 45 minutes before sunrise at the start of the month. By the end of the month, Jupiter will rise 2 hours before sunrise. Looking East-Northeast about half an hour before sunrise on the 17th, the waning crescent moon will be just to the left and slightly below Jupiter.

That’s all for this month. And, as the great Jack Horkhemier used to say, Keep Looking Up!

Helen Hart, 1 June 2012; references: Joe Spargo’s June Skies article; the Astronomical Calendar, Starry Night planetarium program, USNO Astronomical Data Services.

As we spin towards summer, the length of the day continues to increase, but more slowly. Early in May the sun rises about 6 am and sets about 8:10 pm; near the end of May it rises about 5:45 am and sets about 8:25 pm. (All times are EDT.)

Phases of the Moon: Full on the evening of May 5; 3rd quarter on May 12, New on May 20; and 1st quarter on May 28. On May 20 the Moon will partially cover the Sun in what is called an annular eclipse. The eclipse will not be visible from Maryland, but if you are planning to be anywhere north-west of a line from central Texas through central Wisconsin, you might be able to see it in the late afternoon before sunset. Be sure to use safe viewing techniques (eg. Observing Solar Eclipses Safely).

Evening Sky: Auriga (the Charioteer), with its bright star Capella, and Gemini (the Twins) (bright stars Castor and Pollux) dominate the western sky after sunset. At this time of year in the evening, the Big Dipper very high in the sky, making it quite easy to use the Pointer Stars to find the North Star, aka Polaris. Bootes (the Herdsman) with its bright star Arcturus is well up in the north-east. Mars is high in the sky towards the south-west, still near the bright star Regulus in Leo (the Lion). Saturn is high in the sky towards the south-east, near the bright star Spica in Virgo (the Young Woman). Venus is at it most brilliant in early May, gleaming high above the western horizon, poised for its plunge back towards the Sun and its Transit of the Sun on June 5th. Early in May Venus sets more than 3 hours after sunset. As the month progresses, Venus appears lower and lower in the sky, until by the end of May it will set a mere 30 minutes after sunset. Viewed with good binoculars or a small telescope, the sunlit disk appears as a fat crescent early in the month; during the month, the crescent will grow in length while it thins to a sliver, as Venus “catches up with” the Earth as the two planets move in their orbits around the Sun. The crescent phases of Venus were one of the key observations that lead Galileo to conclude that the Earth is not the center of motion for the solar system.

Pre-dawn Sky: For those who start the day early, or are just getting off the 6pm-3am shift, the pre-dawn sky holds some treats. Early in May, Sagittarius (the Archer) is rising in the south-east, and Scorpius (the Scorpion), harbinger of summer, with its bright red star Antares, is well up towards the south. The name “Antares” is of Greek origin, and means “not Mars”. If you are out between 1 am and 2 am in the morning early in May, take a moment to compare Antares with Mars, which is low on the western horizon, and you may understand why that star received such a name. In addition, Saturn is still high in the sky towards the south-west, and does not set until around sun rise. If the sky is dark enough in your area, you may see the faint glow of the Milky Way rising up from Scorpius and Sagittarius and arcing above the eastern horizon through Aquilla (the Eagle) and Cygnus (the Swan).

That’s all for this month.   And, as the great Jack Horkhemier used to say, Keep Looking Up!

Helen Hart, 30 April 2012; references:  the Astronomical Calendar, Starry Night planetarium program, USNO Astronomical Data Services.

Daylight hours continue to increase in April, as the Earth spins through spring towards summer. Early in the month (about April 4th) the sun will rise at 6:45 am EDT, and set by 7:36 pm.  Towards the end of the month (about April 20th) the sun will rise at 6:20 am, and set by 7:50 pm.   The moon will be at Full phase on April 4, 3rd quarter on April 13, New on April 21 (a happy circumstance for the Lyrid meteor shower), and 1st quarter on April 29.

On April 2-4 Venus glides past the Pleiades (the Seven Sisters and their parents).  The stars of the Pleiades cluster are only moderately bright (third and fourth magnitude), and brilliant Venus will outshine them by 8 magnitudes.  Closest approach will be April 2nd, when Venus passes less than half a degree the brightest sister Alcyone (for comparison, our Moon is about half a degree wide).  Venus remains the brightest object in the evening sky (barring the Moon), and will be visible for at least 3 hours after sunset every clear evening.   By the end of the month, Venus will appear as a fat crescent, as it moves around the Sun towards inferior conjunction (and transit!) on June 5th.

Mars is the second brightest planet in the evening sky, high over the south-eastern horizon at sunset.  Mars is still in the retrograde phase of it’s dance with Earth, and will spend the entire month hanging out in the constellation Leo near the bright first magnitude star Regulus. Mars is about 3 magnitudes brighter than Regulus, and will be obviously reddish to most people.   The Big Dipper can be used to find Leo and Regulus: first use the Big Dipper’s pointer stars to find Polaris (the North Star), then trace back the opposite direction, across the zenith of the sky (you’ll want to spin around to face South at this point, or you’ll fall over backwards 😉 to the first bright star you come to – that’ll be Regulus – and this year Mars will be right there, too.

Jupiter gradually disappears into the western sunset as the month progresses, while Saturn moves into the evening sky.  Saturn reaches opposition on April 15th, and will be zeroth magnitude.  The rings continue opening from their edge-on appearance in 2009, and this year will be tipped towards Earthly viewers by a full 15 degrees; the maximum  opening of 27 degrees will occur 13 years from now, in 2025.

The Lyrid meteor shower is predicted to peak on April 21, the same date as the New Moon, so there will be no moonlight to wash out the meteor trails.   City lights can definitely wash out meteor trails, so if you’d like a really good view plan to spend your pre-dawn hours as far from street lights and dark-phobic neighbors and car dealerships as you can get.   This shower is usually not too spectacular, with average Zenith rates of only 18 per hour, but the meteors are relatively swift, owing to the Lyrid orbit relative to Earth’s orbit, some can be spectacularly bright, and about 1 in 5 leave a train that persists for several seconds.

That’s all for this month.   And, as the great Jack Horkhemier used to say, Keep Looking Up!

Helen Hart, 19 March 2012; references:  the Astronomical Calendar, Starry Night planetarium program, USNO Astronomical Data Services.

Daylight Savings Time starts March 11.  Spring Equinox occurs March 20 at 05:14 UT (1:14 am EDT).  The Moon is Full on March 8, and New on March 22.

The evening sky is dominated by the constellations Orion and Canis Major (the Big Dog) towards the south, and by planets Venus and Jupiter, shining high and bright above the south western horizon at sunset; Venus is the brighter of the two.  Early in the month, Jupiter is higher above the horizon than Venus; on March 12, the two will be only 3 degrees apart, and will set at the same time, about 11 pm;  after the 12th, Jupiter and Venus appear to move apart, and Venus is higher in the sky than Jupiter.  On March 25-26 the young Moon passes near both planets, which should be a pretty sight.

Mars rises in the east around sunset and will be visible all night, shining almost as brightly as the star Sirius in the constellation Canis Major.  Mars reaches opposition on March 3; because Mars is near aphelion, its apparent size is relatively small, less than 14 arc-seconds at best.  Mars is in the middle of its northern hemisphere summer, so the North polar cap will be visible through a moderately sized telescope.

Saturn rises after 10 pm by the end of the month, and isn’t well placed for viewing until midnight.  Early in the month both Saturn and Mars are visible above the western horizon in the morning before sun rise.

Helen Hart, 17 Feb. 2012;  references:  Starry Night planetarium program, USNO Astronomical Data Services.