The Sky This Week, 2015 December 29 – 2016 January 5
2015 ends with the Moon waning in the early morning sky. First Quarter occurs on January 2nd at 12:30 am Eastern Standard Time. During the early morning hours Luna drifts past the bright planets that are strung out along the Ecliptic. Look for bright Jupiter near the Moon on the morning of the 31st. On the morning of January 3rd Luna forms a nice triangle with ruddy Mars and the bright blue-tinted star Spica. She ends the week closing in on dazzling Venus in the brightening morning twilight.
The latest sunrise of the year occurs on January 5th, when Old Sol crests the horizon at 7:27 am EST here in Washington, DC. On that same evening sunset occurs at 5:00 pm, 14 minutes later than its earliest sunset back on December 7th. The total length of daylight on New Year’s Day will be 9 hours 30 minutes, four minutes longer than it was on the day of the solstice, and the days will steadily increase in length until the summer solstice, which will fall on June 20.
January 2nd marks the date of Earth’s perihelion, its closest distance to the Sun. On this date we’ll be a mere 147 million kilometers (91.4 million miles) from the fierce surface of the “day star”.
New Year’s Eve is perhaps the one night of the year when almost everybody stays up late to send the old year packing and welcome the new. It’s also a great time to go out and look at the stars. Face toward the south and you’ll be presented with the magnificent Great Winter Circle asterism, centered on the bright of the constellation Orion, the Hunter. Draw an imaginary line through Orion’s “belt” stars and extend it to the southeast and you’ll run into Sirius, the brightest star in the entire sky. By a curious coincidence of timing and the 26,000-year precession cycle, Sirius crosses the meridian at local midnight on New Year’s Eve, a fitting astronomical marker for this annual event. Sirius also marked the beginning of the New Year for the ancient Egyptians. In their timekeeping system the new year began with the annual inundation of the Nile River, which usually began in mid to late July. Around 2800 BCE Egyptian astronomers noticed that Sirius rose just before sunrise on July 21, just as the flood was getting underway. Since their civil calendar only had 365 days in it, the annual cycle of heliacal risings of Sirius and soon became out of synch with their civil day-count. However, after 1461 of their calendar years the heliacal rise once again corresponded with the beginning of the civil calendar year. A testament to the duration of the Egyptian civilization is the fact that they observed this coincidence three times during the civilization’s lifetime.
Midnight revelers might notice a bright object cresting the horizon in the east. This is the giant planet Jupiter, gradually making his way into the evening sky. Jupiter lords over the morning sky and is still very well-placed for skywatchers who rise with morning twilight. Old Jove gets a visit from the Moon on the last morning of 2015, offering two great targets for any telescopes that appeared under the Christmas tree.
Ruddy Mars spends the week drifting eastward from the bright star Spica and also gets a visit from the Moon on the morning of the 3rd. Mars is gradually beginning to increase in brightness and in the apparent size of his distant disc. 2016 will be a banner year for observing Mars. When he reaches opposition in late May he’ll be almost as bright as Jupiter.
Venus is now dropping toward the Sun, but she is still easy to find if you have an open eastern horizon. Her dazzling glow is prominent in the southeast as morning twilight gathers, and on very clear mornings you should be able to follow her for a while after the Sun has risen. She will pass close to golden Saturn on the morning of the 9th.
