SKY HAPPENINGS

The Sky for February 2015
By Faylene Roth

The Big Dipper, an asterism in the constellation Ursa Major, hangs in the eastern sky with its handle downward during early evenings. Follow the two outer stars of the cup southward to Regulus (Leo). On February 4, a one-day old gibbous moon hangs below hot, blue Regulus. On the night of February 8/9 the waning gibbous moon rises soon after midnight and travels across the sky ahead of bright, blue Spica (Virgo). Between February 24 and 25 the quarter moon sidles up to and passes red supergiant Aldebaran (Taurus) and moves across Orion by the next night. On February 27 the Moon sits in the middle of six bright stars forming the Winter Circle. By the following night a waxing gibbous moon has moved north of Procyon.

Twilight extends the period of daylight in three stages at each end of the day. Morning twilight begins with astronomical twilight—about 1-1/2 hours (nearly 2 during summer months) before sunrise—as the eastern horizon brightens. Nautical twilight continues—as the overhead sky turns blue and color returns to the surrounding landscape—for another 30-40 minutes. The final stage—civil twilight—provides adequate light for most outdoor activities for the half hour before the sun crests the horizon. The opposite progression occurs after sunset.

DAYLENGTH
Days lengthen as the sun’s apparent position in the sky moves higher—or northward. However; it is the Earth’s orbital movement—not the sun’s—that causes this apparent change in the sun’s position. Since the direction of tilt of the Earth’s axis is relatively fixed, the Earth’s progression through its orbit continually presents a new face towards the sun. As Earth approaches the March equinox, the line of the equator becomes more perpendicular to the rays of the sun. From the northern hemisphere, the sun appears to move from a position low in the sky below the equator to a position higher in the sky. By March 20 the sun will be directly above the equator.

CELESTIAL EVENTS
No major meteor showers occur during February, although fireballs—mega-meteors as bright as Jupiter and Venus—often occur. Best chances for viewing are between 3:00am and dawn. Viewing the zodiacal light associated with the spring equinox is more predictable. The best chance to see this cone-shaped beam of light is on moonless evenings between February 7 and 17. Once the golds, reds, and residual glimmers of evening twilight have faded from the western sky, look for a broad beam of white light shooting nearly straight up from the point where the sun had set. The zodiacal light occurs near both equinoxes when sunrise and sunset are nearly vertical to the horizon. It occurs when sunrays from below the horizon reflect off dust particles within the open spaces of our solar system..


MOON HAPPENINGS
February 3– Bright skies all night after the full moon (4:09pm) rises at 5:51pm.
February 11– Dark evening skies until after midnight when the waning last quarter moon rises.
February 18– Dark sky period for several days before and after the new moon at 4:47pm.
February 25– Bright evening skies until after midnight when the waxing first quarter moon sets.
(The moon rises later each day—as little as 30 minutes to as much as one hour. Time of moonrise and moonset may also be delayed in mountainous terrain.)

VISIBLE PLANETS
Jupiter – The brilliance of Jupiter reigns in the night sky from dusk until dawn. Look for it on the eastern horizon at evening twilight. On the nights of February 2 and 3 Jupiter appears near the full moon. Jupiter reaches opposition (opposite side of Earth from sun) on February 6 which brings it in for a close view with binoculars and small telescopes. (Magnitude -2.3)
Mars – Red-hued Mars continues to diminish in size and brilliance as it moves towards the far side of the sun. Look for it low on the western horizon hovering above Venus. Mars and Venus reach a close conjunction within 0.5 ̊ on February 21 during astronomical twilight. Mars sets about one hour after astronomical twilight ends.(Magnitude +1. 2)
Saturn – Look for Saturn high in the southeastern sky at dawn. It rises after midnight near the head of Scorpius. On February 14 a waning crescent moon passes within 2 ̊ of Saturn. (Magnitude +1.2)
Venus – At evening twilight Venus dominates the western horizon. In early February it sets about one hour before Mars. By February 21, they set together at about 8:20pm, after which Venus sets after Mars. (Magnitude -3.9)

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.

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

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