SKY HAPPENINGS

The Sky for June 2012
By Faylene Roth

SUMMER SOLSTICE
The sun’s northward movement in the sky slows to a halt this month as the earth rounds the far end of its elliptical orbit. The length of the day increases by only 10 minutes from June 1 to June 20 and then loses three minutes during the remaining 10 days of the month. The solstice point arrives June 20 at 5:09pm MDT. Earliest twilight begins around 4:00am and evening skies do not completely darken until after 10:30pm.

PARTIAL LUNAR ECLIPSE
This month’s lunar eclipse on the morning of June 4 is the counterpart to last month’s annular eclipse of the sun. They occur in pairs. The initial penumbral shadow begins to cover the moon a little before 3:00am. The dark umbral shadow touches the moon at 4:00am and continues to spread across the moon for the next two hours. The moon sets about the time the umbral period ends. Actual viewing time depends upon the surrounding landscape.

METEOR EVENTS
No major meteor showers this month, but minor activity is present throughout the month from a variety of radiants. In the early morning hours of June 16 look for a radiant from Lyra. Best viewing occurs as the radiant moves overhead.

TRANSIT OF VENUS
If you still have eclipse viewing equipment available from last month’s solar eclipse, then you will be ready to view the transit of Venus across the sun on June 5. For those who didn’t observe the transit of Venus in 2004, don’t miss this once in a lifetime chance. It doesn’t recur until 2117. Only planetary transits of the interior planets, Venus and Mercury, are visible from Earth. Historically, transits enabled astronomers to measure the size of the solar system during the 18th and 19th centuries. Currently, astronomers look for transits across distant stars in their search for planets outside our solar system.

The transit begins at 4:05pm and continues for the next four and one-half hours. Venus exits a few minutes before the sun sets at the horizon. With proper eye protection, the planet will be visible as a small black dot moving across the sun.

As with the recent eclipse, it is never safe to look directly at the sun. Salt Lake City’s Clark Planetarium provides information on safe viewing methods on their website at: http://clarkplanetarium.org. They warn that viewing the sun without proper eye protection can permanently damage your vision. Only—AND I STRESS ONLY—Grade 14 welder goggles designed specifically for arc welding or specially-designed eclipse shades are safe. Viewing aids to AVOID are: polarized sunglasses, doubled-up sunglasses, smoked glass, mylar wraps, and exposed camera film. See their website for further details.

MOON HAPPENINGS
June 4 – Full Moon occurs at 5:12am and rises at 9:12pm (8:08pm on June 3).
June 11 – Last Quarter Moon rises about two hours after midnight.
June 19 – New Moon occurs at 9:02am.
June 27 – First Quarter Moon sets soon after midnight.

(The time of moonrise and moonset assumes a flat horizon. Actual time may vary.)

Note: Hold your hand at arm’s length to measure apparent distances in the sky. The width of the little finger approximates 1.5 degrees. Middle, ring, and little finger touching represent about 5 degrees. The width of a fist is about 10 degrees. The fist with the thumb extended at a right angle equals 15 degrees. The hand stretched from thumb to little finger approximates 20-25 degrees. The diameter of both the full moon and the sun spans only 0.5 degree. Adjust for the size of your hand.

Primary Sources: USGS; U.S. Naval Observatory;
Your Sky at http://www.fourmilab.ch/yoursky/

To find out when the space shuttle and International Space Station are visible
from your location, go to: http://spaceflight.nasa.gov/realdata/sightings/index.html and click on Sighting Opportunities.

VISIBLE PLANETS
Jupiter - Bright Jupiter claims the early dawn sky in the early days of the month, but ever more brilliant Venus upstages it by midmonth. (Magnitude -2.0)

Mars - The red planet lingers below Regulus (Leo) in the evening sky. It moves slowly southward towards Spica (Virgo) throughout the month. (Magnitude +0.7)

Mercury - A great chance to view Mercury with the naked eye occurs the evening of June 21. Look for it around 9:30pm-10:00pm in the western sky with Gemini about five degrees above and a very thin crescent moon almost six degrees below. The moon will be much farther away the next night. (Magnitude -0.7)

Saturn - Yellow-lit Saturn hovers above and barely outshines blue-white Spica (Virgo) just a few degrees below. (Magnitude +0.6)

Venus - A few days after its transit across the sun, brilliant Venus reappears in the morning sky, edging out Jupiter, as the true “morning star.” By month’s end, both Venus and Jupiter are huddling around Taurus’s major red star Aldebaran. (Magnitude -3.9)

Note: Apparent magnitude values range from -4 to +6 for most planets and visible stars. The lower the value the brighter the object. A decrease of 1.0 magnitude is 2.5 times brighter.

Bright stellar objects zigzag across the night sky. From east to west: Deneb (Cygnus), Vega (Lyra), Arcturus (Bootes), southward to Saturn and Spica (Virgo), northwestward to Mars, Regulus (Leo), twin stars of Gemini, and little dog star Procyon (Canis Minor) to the south. Cygnus anchors to the Milky Way which swings westward as the earth rotates towards a morning sky which reveals Jupiter, then Venus, as the month progresses.

Hold the star chart high above your head and match the compass directions to the direction you are facing. Adjust the star chart by orienting Ursa Major (Big Dipper) to match its position in the sky.

The star chart approximates the sky from astronomical twilight to midnight. As the night and month progresses, the constellations shift toward the northwest. The celestial equator is measured in hours (h).
The ecliptic is measured in degrees.