SKY HAPPENINGS

The Sky for March 2013
By Faylene Roth

DAYLIGHT SAVING TIME
On March 10 we exchange an hour of morning light for an hour of evening light. DST begins on the second Sunday in March at 2:00am when time springs forward to 3:00am. Fyi...the proper phrase for DST is “daylight saving time” rather than “daylight savings time.” It’s a grammar issue about adjectives and nouns. The United States Naval Observatory currently uses the phrase “daylight time” to parallel “standard time.”

DAYLENGTH
March favors light. Not only does the period of daylight increase by one hour 15 minutes (largest increase during any one month), but the balance of daylight hours versus hours of darkness tips in favor of daylight with the vernal equinox. Note, however, that the first 12-hour day occurs four days before the equinox. That anomaly results from refraction of light through the atmosphere around the curvature of the earth.

Track the change in light at each end of the day through three stages of twilight. Civil twilight marks the well-lit 30-minute period immediately before sunrise and after sunset. Nautical twilight begins about one hour before sunrise and one-half hour after sunset. This period charts a change in the quality of light during which colors and shapes define the morning landscape or dissolve from the evening landscape. Astronomical twilight begins with the earliest hint of light in the eastern dawn sky around one and one-half hours before sunrise. In the evening sky, it follows the 30-minute period of fading light of nautical twilight. By the end of evening, astronomical twilight—one and one-half hours after sunset—darkens the western horizon and night begins.

VERNAL EQUINOX
By the time the sun rises on March 20, springtime will be official. March 20 at 5:02am MDT the sun’s position in the sky passes the celestial equator and makes way for warmer temperatures in the northern hemisphere. (The celestial equator traces a line across the sky directly above the earth’s equator.) Take note of the positions of due east and due west from your location as the sun rises at 7:21am and sets at 7:30pm.

MOON HAPPENINGS
Mar 4 – Last Quarter Moon rises soon after midnight.
Mar 11 – New Moon occurs at 1:51pm.
Mar 19 – First Quarter Moon sets after midnight.
Mar 26/27 – Full Moon rises 3/26 at 7:16pm and becomes full 3/27 at 3:27 am.
(The time of moonrise and moonset assumes a flat horizon. Actual time may vary.)

COMET VIEWING
Astronomers have been tracking Comet PANSTARRS (c/2011 L4) since mid-2011. Currently visible in the southern hemisphere, it comes into visible naked-eye range for northern hemisphere viewers in early March. Comets often do not live up to their predicted grandeur; but, if true in this case, expect a 0-magnitude object at least as bright as all the brightest objects in the night sky (Sirius in Canis Major and Jupiter in Taurus excepted).

Find a high vantage point with a clear view of the western skies because the comet appears low on the horizon. Look almost due west below brilliant Jupiter, which should be visible high in the western sky as nautical twilight begins (see Daylength paragraph). Don’t expect a starlike point of light. Comets can be differentiated from surrounding stars because they appear as a more diffuse ball of light. Binoculars and small telescopes will help refine the shape and reveal the comet’s tail.

The arrival of Comet PANSTARRS in our skies marks a trip measured in millions of years from the Oort Cloud of comets circling our solar system. It passes nearest to earth on March 5 and nearest to the sun on March 10. Another 110,00 years will pass before it returns. Best viewing in the northern hemisphere is March 8-12. PANSTARRS continues to be visible into April but may require magnification. On March 12/13 a waxing crescent moon returns to the western evening sky. Look for the comet first to its left then to its right on subsequent days. Throughout March it moves northward from Pisces into Andromeda where it passes the Andromeda Galaxy in early April.

METEOR EVENTS
Some striking fireballs streaked through the February skies and commonly continue through March and April as random events. No major meteor showers occur in March.

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.

VISIBLE PLANETS
Jupiter – Locate the brightest object in the evening sky on a moonless night, and you have found Jupiter (high in the west) in Taurus. On March 17 a near-quarter moon squeezes between Jupiter and Taurus’s red star Aldebaran—Jupiter 1.5 degrees to the west and Aldebaran 3.5 degrees to its east. Jupiter sets soon after midnight. (Magnitude -2.2)

Saturn – Around midnight on March 1 look for a waning gibbous moon rising about 3.5 degrees to the right of Saturn with blue-white Spica (Virgo) to the moon’s far right. The golden planet (in Libra) lingers in the sky through morning twilight. On March 28 a waning full moon again positions itself between Spica and Saturn. (Magnitude +0.3)

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.

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.

Use the stars of the Big Dipper in Ursa Major to identify bright stars in the evening sky. Follow the arc of the handle away from the dipper to Arcturus (Bootes). Continue the arc to Spica (Virgo). Trace the two stars of the dipper that attach to the handle downward to Regulus (Leo). The two outer stars of the dipper lead northward to Polaris (Ursa Minor/Little Dipper).

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.