Planetarium

AUGUST 2012 NIGHT SKY CALENDAR

Heat shimmers; hazy days of bronze sky over boundless ocean.

(We're trying to rip through the pseudo-poetic adjectives quickly so we can get to the delicious night sky part)

Majestic flaggers like sculptures; laughing children pointing at car lines; furious tourists breathing brimstone; Grandmother brings preserves to the bottom of the cellar, so the Red Sox have something to snack on.

August: the late summer core.

And we can enjoy the gradually longer nights, continued warm weather; and, hopefully, crystal clear skies.

WEDNESDAY, AUGUST 1

LAMMAS: How splendid to begin a night sky calendar with an event one cannot observe in the night sky! Lammas is astronomically significant because it is a cross quarter day, which is a day approximately mid way between two seasonal points. Lammas is the cross quarter day between the summer solstice and the autumnal equinox; the next cross quarter day is Samhain, or Halloween, the CQ day between the autumnal equinox and winter solstice; February 2 is Candlemas or Ground Hog's Day: the cross quarter day between the winter solstice and vernal equinox. Finally, May 1, or May Day, is between the vernal equinox and summer solstice.

WEDNESDAY, AUGUST 1

FULL MOON: Every full moon has a special name, depending on the month in which it occurs. The August full moon is called the Sturgeon Moon or the Green Corn Moon. However, this year's August full moon is special because this month we'll have two full moons. The second full moon (see August 31) is the famous blue moon.

TUESDAY, AUGUST 7

MERCURY STATIONARY: The closest planet appears to halt in place before changing direction. The planets never change direction, of course. All the planets move in the same direction around the Sun. This motion follows the same spin of the nebular cloud from which the planets formed billions of years ago. Planets generally move west to east in the sky. Occasionally, though, they'll seem to change direction and move westward. Mercury appears to change direction because we're watching it from a position outside its orbit. So, just as people watching cars racing around a circular track see them move in one direction when the cars are in the foreground and in another direction when they are on the track's far side, we see Mercury shift motion directions as it moves in its orbit.

THURSDAY, AUGUST 9

LAST QUARTER MOON

FRIDAY, AUGUST 10

SUN ENTERS LEO THE LION: We encounter this issue every month. The Sun appears to travel through thirteen different constellations throughout the year. These constellations are always the same - Pisces the Fish; Aries the Ram; Taurus the Bull; Gemini the Twins; Cancer the Crab; LEO THE LION; Virgo the Maiden; Libra the Scales; Scorpius the Scorpion; Ophiuchus the Serpent Charmer; Sagittarius the Archer; Capricornus the Seagoat; Aquarius the Water Bearer.

Today, Earth moves to the far side of the Sun relative to the stars comprising the Leo constellation. From our perspective, it appears as though the Sun has actually "moved" into Leo the Lion.

SATURDAY, AUGUST 11

MOON 0.68 DEGREES EAST OF JUPITER: A brilliant sight for late night observers See the waning crescent moon and Jupiter in the post midnight eastern sky. As we'll learn in the planet watch section, Jupiter is now growing brighter as it rises earlier in the evening. Jupiter will soon be a prominent planet once again. Tonight, see the giant world close to the crescent moon.

SUNDAY, AUGUST 12

PERSEID METEOR SHOWER PEAKS (PICK EVENT!): Why do we like meteor showers? Well, they are visual spectacles and they occur because our planet is moving through a stream of comet particles. Even though this meteor shower peaks on August 12th, its duration is between July 17 and August 24th: the time period Earth requires to completely traverse the vast region the Comet Swift Tuttle particles occupy. Today, our planet passes through the densest area within this region. Consequently, the frequency of meteors should be at its highest.

Astronomers use a term called Zenith Hourly Rate (ZHR) to esttimate this frequency. ZHR refers to the number of meteors a seasoned observer would see were the radiant (the point from which the meteors appear to originate) at the zenith (point directly overhead) in a completely dark sky.

The Perseid ZHR is 100. However, we cannot expect to see 100 meteors an hour because the radiant is not at the zenith and most skies are not completely dark. Tonight one can expect to see, perhaps, about 40 - 55 meteors an hour. The best time to view if after midnight, when our part of the planet turns into the direction of the meteoroid stream.

MONDAY, AUGUST 13

MOON 0.90 ENE OF VENUS: We would have chosen this appulse as the pick event if it had been an occultation: a passage of the Moon in front of the planet. We here in the northeastern part of the US won't see an occultation, but viewers in Asia will. (This occultation will occur in the daytime for the western North America) Here, we'll see the Moon and Venus together in the pre-dawn eastern sky.

WEDNESDAY, AUGUST 15

MARS 2.7 DEGREES SSW OF SATURN: See these two superior planets in the evening western sky. Mars will the slightly dimmer than Saturn, but the former's red color is distinct. Both worlds will remain in the western sky for a couple of hours after sunset.

WEDNESDAY, AUGUST 15

VENUS AT GREATEST WESTERN ELONGATION: Remember earlier this summer when Venus passed directly across the Sun? Well, since this time, Venus moved into the early morning sky where we'll find it this month. Today, the planet reaches its greatest angle relative to the Sun, a value known as "elongation." This greatest elongation angle is 45.8 degrees. Note: When at western elongation, the planet is in the eastern pre-dawn sky; when at eastern elongation, the planet is in the western evening sky.

WEDNESDAY, AUGUST 15

MOON 3.4 DEGREES SSW OF MERCURY: An observer might see the Moon and Mercury low in the pre-dawn eastern sky tonight. The Moon will be at the last stages of the waning crescent phase and will appear as a thin sliver. One might see Mercury and the thin Moon against the brightening twilight.

THURSDAY, AUGUST 16

MERCURY AT GREATEST WESTERN ELONGATION: Hey, try not to notice that we cut and pasted some lines from the Venus elongation paragraph and used them here. Today, the planet reaches its greatest angle relative to the Sun, a value known as "elongation." This greatest elongation angle is 18.7 degrees. Note: When at western elongation, the planet is in the eastern pre-dawn sky; when at eastern elongation, the planet is in the western evening sky.

FRIDAY, AUGUST 17

MARS AND JUPITER AND HELIOCENTRIC OPPOSITION: This one is for those who just cannot get enough astronomy. Today, Mars and Jupiter will be in opposition relative to the Sun. Jupiter is currently in Taurus the Bull and Mars is passing from Virgo into Libra.

FRIDAY, AUGUST 17

NEW MOON: Beginning of lunation cycle 1109.

TUESDAY, AUGUST 21

MOON 1.1 DEGREES SSE OF SPICA: Spica is Virgo the Maiden's brightest star. As we approach early autumn, Virgo will draw ever closer to the setting sun. Now is a splendid time to observe this bright summer star before it annual hiatus. The waxing crescent moon is just to the south of it tonight.

TUESDAY, AUGUST 21

MOON 5.2 DEGREES SSW OF SATURN: Hey, if you have a telescope or even binoculars, tonight would be a splendid time to use them to observe the Moon and the ringed planet.

Even with binoculars one can see moon features such as craters and rays and Saturn's rings, if not actually resolved, will appear as knobs on either side of the planet.

WEDNESDAY, AUGUST 22

MOON 2.4 DEGREES SW OF MARS: Since Mars and Saturn are close together in the sky, it makes sense that the Moon would pass close to Saturn one night and then Mars the next. The advantage of these passages is that one can find two different planets by watching the sky on two consecutive nights.

FRIDAY, AUGUST 24

FIRST QUARTER MOON

FRIDAY, AUGUST 31

FULL MOON: Well, it's as though August burned through its trick bag so quickly that it spent the last part of its act just staring nervously at the audience without anything else to do. August's second full moon is tonight! The second full moon is one month is called a "blue moon." This origin of this term is quite a mystery. Some claim the term derives from, of all accursed things, an early 20th century Maine farmer's almanac. Others claim its first usage was in 19th century France, with the word "blue" moon being a mistranslation of the French word for 'double moon.'

PLANET WATCH

MERCURY: Not much to see at month's beginning, but becomes a bright early morning sight by mid month. Remains visible for the rest of August, although its difficult to find by month's end. VERDICT: Mercury admirers are well advised to look around the third week of August in the pre-dawn sky. After all, Mercury will not be visible at all in September.

VENUS (PICK PLANET!) Venus is a brilliant morning sight this month. Yes, we made a big deal out of Venus in June and so it has received the lion's share of our attention. VERDICT: Though not conveniently located for late risers, Venus is a beautiful pre-dawn planet that will rise a couple of hours before the Sun. Definitely worth a look if you're up anyway.

EARTH: Look down

MARS: Though Mars was brighter earlier this year, it is still a conspicuous sight in the western evening sky. Mars plays with Saturn throughout the month, producing a beguiling pair just after dark. VERDICT: A lovely ruddy planet one can easily see in the western early evening sky. Good to find it now as it will grow dimmer throughout the rest of the year.

JUPITER: Even if Mars is growing dimmer and Saturn is soon destined for the backstage dressing room, Jupiter is rising earlier and quickly becoming brighter. Jupiter will be a gorgeous autumn and winter planet. Even now it is cute as a button and has an engaging personality. VERDICT: Still a late riser, Jupiter is best seen by those who venture out quite late or early. If you give it a miss this month, you'll have plenty of time to see it later this year.

SATURN: Saturn is not long for the night sky. Having been a prominent feature throughout the summer, Saturn will set with the Sun by early October, only to return to the morning sky by mid November. As summer winds down, Saturn draws closer to the setting Sun. VERDICT: If you love Saturn, you'll want to find it sooner rather than later in the early evening western sky.