SKY HAPPENINGS

The Sky for January 2014
By Faylene Roth

Every star within the Milky Way Galaxy orbits the galaxy’s center. To determine the direction that the Sun is moving, find the three stars of Orion’s belt. Follow the line of stars downward to brilliant blue-white Sirius (Canis Major) in the southeastern sky. With your back to Sirius, turn to face Vega (Lyra) low in the northwestern sky (line of sight passes a little south of the North Star). This is the direction that the Sun travels through the Milky Way at about 140 miles per second. The Sun’s trip around the galaxy takes about 230 million years.

DAYLENGTH
Daylength depends upon a complex interplay of conditions, such as the Earth’s tilt, location in its orbit, its rotation, its current speed, and latitude. Due to these interactions the shortest day of the year does not coincide with the times of latest sunrise and earliest sunset. Earliest sunset at our latitude occurred around December 8. Latest sunrise will not occur until January 5 at 7:36am. It then rises a few seconds earlier each day, but it will be January 12 before it rises early enough to register as 7:35am.
Twilight also contributes to the length of usable daylight. Civil twilight provides an additional 30 minutes of adequate light for outdoor activity after sunset. Nautical twilight continues another half hour during which the skies darken overhead and color and detail fade in the surrounding landscape. In the final half hour of astronomical twilight, the light on the western horizon fades to darkness. The reverse progression occurs at dawn.

PERIHELION
On January 4 the Earth reaches perihelion with the Sun—that is the closest point (in the Earth’s slightly elliptical orbit) to the Sun. Perihelion cannot overcome the wintery effects of the northern hemisphere’s tilt away from the Sun, but it does shorten the length of the winter season. The Earth speeds up as it approaches perihelion which makes the winter season in the northern hemisphere about 5 days shorter than its summer season. In the southern hemisphere the summer season is shorter than winter.

MOON HAPPENINGS
January 1 – New Moon occurs at 4:14am.
January 8 – First Quarter Moon brightens western sky until after midnight.
January 15 – Full Moon rises at 5:21pm and occurs at 9:52pm.
January 23 – Last Quarter Moon rises several hours after midnight.
January 30 –New Moon occurs at 2:38pm.
(The time of moonrise and moonset assumes a flat horizon. Actual time may vary.)

If January’s full moon appears small, it is because it occurs at lunar apogee. The moon makes a complete orbit around the Earth every month. Each orbit has an apogee point (farthest point to Earth in the lunar orbit) and a perigee point (nearest point to Earth). The size of the lunar orbit expands and contracts during its orbital year (about 13 ½ months) which produces a “micromoon” at farthest apogee and a “supermoon” at nearest perigee. This month’s full moon is the micromoon of the current year. January’s expanded lunar orbit also produces the 2nd and 3rd largest supermoons of the current lunar year on January 1 and January 30. Supermoons occur when the moon is within 90% of lunar perigee. Even though we don’t see new moons, they can produce tidal effects that rival those of a full moon.

METEOR EVENTS
A new moon period provides excellent viewing conditions for the Quadrantid Meteor Shower which runs January 1-5. The Quadrantids average about 40 meteors per hour at its peak which lasts for just a few hours on the night of January 2/3. The radiant for this meteor event is in the region where the tail of Ursa Major dips towards Hercules and Boötes. Best viewing spans the hours between midnight and early twilight. The name of this meteor shower refers to a constellation called Quadrans Muralis. The name refers to an instrument used by 18th century astronomers to measure the altitude of stars. Quadrans Muralis lost its status as a constellation in 1930 when the International Astronomical Union adopted 88 constellations to delineate specific regions for its official map of the night sky.

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.

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- Jupiter is visible throughout the night below Pollux and Castor (Gemini). Look in the eastern sky at evening twilight, overhead at midnight, and in the western sky at morning twilight. On January 5/6 Jupiter reaches opposition (opposite side of Earth from Sun) and its closest point to Earth until 2020. (Magnitude -2.7)

Mars- Its steady red glow is unmistakable, but Mars presents a very small disk visually, because it is very near aphelion (farthest distance from Sun in its two-year orbit). Look for it after midnight a few degrees above blue-ish Spica (Virgo). By morning twilight it is high in the southern sky. (Magnitude +0.4)

Mercury- During the last week of the month Mercury rivals Sirius (brightest visible star in the night sky) in brightness and climbs high enough above the horizon to be more easily seen than usual. Look for it about 15°-20° above the west-southwest horizon at nautical twilight while Sirius rises in the southeastern sky. Binoculars may help distinguish it in the lingering solar glare. (Magnitude -1.1)

Saturn- Saturn rises (with Libra) several hours after midnight in a faintly-starred region of the eastern sky. Its golden light forms a triangle with orange-hued Arcturus (Boötes) to the north and blue-tinged Spica to the east. It is high in the eastern sky by morning twilight. (Magnitude +1.2)

Venus- Venus is lost in the glare of the Sun for most of the month. On January 11 it reaches inferior solar conjunction as its orbit passes between Sun and Earth. Venus reappears in the morning twilight during the last week of January. Look for it in the south-southeastern sky about 60-90 minutes before Sunrise. (Magnitude -3.7)

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.

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.