and Sunset Times for
January provides an additional 43 minutes of daylight as the Earth’s orbit swings away from its solstice position. Civil twilight provides an additional 30 minutes of adequate daylight for outdoor activity. Nautical twilight continues another half hour and is defined by the disappearance of color and detail in the surrounding landscape. During astronomical twilight—a final half hour—the reflected light of the sun on the western sky fades to black. (The time of sunrise and sunset assumes a flat horizon. Actual time may vary depending upon the landscape.)
January begins with a waning gibbous moon. On January 2 the moon rises with Mars soon after 8:00pm on the eastern horizon. On January 6 it rises one hour after Saturn. The last quarter moon occurs January 7. In the early morning hours of January 8 a waning moon rises around 2:00am (about 30 minutes after Spica). On January 11 a waning crescent moon appears to the left of Antares (Scorpius) about one hour before sunrise. A new moon occurs January 15. On January 17 a thin waxing crescent appears in the southwestern sky below Jupiter. The next night the moon is almost 15 degrees above Jupiter. The first quarter moon occurs January 23. On January 24 a waxing gibbous moon appears below the Pleiades as twilight fades. A full moon rises on January 29 at 5:19pm. It becomes full at 11:18pm as it moves across the sky below Gemini’s twin stars. Mars and Saturn trail behind its eastern side. On January 30 a waning moon hangs below Mars. On January 31 it sits with Mars on its right and Saturn on its left.
On Saturday, January 2, at 5:00pm, the Earth makes its closest approach to the Sun. This point is called perihelion. Since Earth’s orbit around the Sun is an ellipse, the Sun is offset slightly from the center point of the orbit. The variation in distance between perihelion and aphelion (farthest point from the sun) is less than three percent. It is a coincidence that perihelion occurs during our winter season when the Earth’s axis is tilted away from the Sun. The date of perihelion regresses by about 25 minutes every year (one day every 58 years). Within a 21,000 year cycle, perihelion will pass through every season.
Both Saturn and Mars exhibit retrograde motion this month. The orbital direction of the planets causes them to move eastward each night against the background stars. However, the Earth orbits the Sun faster than do the outer planets. When the Earth moves past an outer planet, the outer planet’s motion appears to drift westward against the background stars. Retrograde motion reverses to normal once the Earth has passed the outer planet.
The Quadrantids peak on the night of January 3/4 with sightings possible January 1-5. The radiant for this meteor shower is the region between Bootes and Ursa Major. The Quadrantids are known to produce abundant meteors, but they are faint. A waning gibbous moon shines throughout the night during this year’s event so expect most of the activity to be obscured. If you do see meteors after midnight during this meteor shower, trace their trail backwards to see if they originated from the Quandrantid region.
NASA SIGHTING OPPORTUNITIES
To find out when the Space Shuttle and International Space Station are visible from your location, go to the following website and click on Sighting Opportunities: http://spaceflight.nasa.gov/realdata/sightings/index.html
Note: Hold your hand at arm’s length to measure apparent distances in the sky. Adjust for the size of your hand. 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 hand stretched from thumb to little finger equals 20 degrees. The diameter of both the full moon and the sun spans only 0.5 degree.
Jupiter - Look for Jupiter’s brilliant beacon in the early evening twilight low in the southwestern sky. It outshines all the stars, including Sirius (Canis Major) which has a magnitude of -1.6. By January 6 Jupiter has moved from Capricornus into Aquarius. At month’s end, it sinks below the horizon as astronomical twilight ends. (Magnitude -1.9)
Mars - Now that Venus is lost in the sun’s glow and once Jupiter has set below the horizon, the night sky belongs to Mars. It is second in brilliance only to the bright blue light of Sirius (Canis Major). At the beginning of the month it rises in the eastern sky soon after 8:00pm. By month’s end it rises before sunset. It is visible throughout the night and its red orb appears to guide Leo toward the western horizon each morning. Mars reaches its closest approach to Earth on January 27. On January 29 it presents its full face to Earth when it is directly opposite the sun. Mars continues retrograde motion this month as it appears to move westward from Leo towards Cancer. (Magnitude -1.2)
Saturn - Identify Saturn by its steady yellow light because it is no brighter now than an average first magnitude star. It rises before midnight and is located on the celestial equator halfway between Spica (Virgo) and Denebola (Leo’s tail). By month’s end it rises about 10:00pm. Saturn can be seen high in the sky in early morning twilight. It begins retrograde motion on January 15. It appears to drift westward, moving farther away from Spica over the next five months. (Magnitude +1.1)
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,
CONSTELLATIONS this MONTH
Six bright stars outline the Winter Hexagon—Capella in Auriga, Aldebaran in Taurus, Rigel in Orion, Sirius in Canis Major, Procyon in Canis Minor, and Pollux in Gemini.
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
night sky from astronomical twilight to midnight. As the night
and the month progress, the constellations will shift toward