‘Leap second’ gives ’08 a jump on atomic clock

Posted Dec. 31, 2008, at 8:43 p.m.

If 2008 seemed to drag on a bit, the reason may be due to the fact that it had one more second than most years. The U.S. Naval Observatory Master Clock facility added a “leap second” at the end of the year to bring traditional time in sync with much more accurate atomic clocks.

Time normally is computed by using the mean rotation of Earth against celestial bodies as reference points. The atomic clock is based on the frequency of radiation emitted by vibrating atoms. Its accuracy is needed for GPS measurements and calculating the paths of space vehicles among many other uses. The Earth’s rotation gradually is slowing so insertion of a leap second occasionally is used to keep the two time systems within one second of each other. There have been 24 leap seconds added since 1972.

Focus on the planets

Mercury is situated well up on the southwestern horizon at dusk for the first week of January, but then begins to fade from view as the month wears on.

Venus blazes high in the southwest about 40 minutes after sunset where it dominates the horizon throughout the month.

Mars is on the far side of the sun from Earth and is lost to view all month.

Jupiter celebrates New Year’s Day just to the lower right of Mercury, but then continues to sink and fade making the giant planet increasingly difficult to view.

Saturn rises above the eastern horizon around midnight as January opens, but is visible by 8:30 p.m. at month’s end. The fabled ring system of Saturn currently appears as little more than a thin line of light across the face of the planet.

Uranus will require a telescope to be visible and is best seen on Jan. 22 when it lies just to the lower left of Venus and both appear in the same optical field.

Neptune lies far to the lower right of Venus where its blue-gray disk may be spotted during the first few days of the month just above the horizon.

January events

1 Sunrise, 7:13 a.m.; sunset, 4:05 p.m. Celebrate the new year by checking out Mercury and Jupiter low in the southwest at dusk. Both — Jupiter first — gradually will disappear into the sun’s glow. Venus is high above them and remains in view all month.

3 Peak night for the Quadrantid meteor shower that will come from the northeast out of the constellation of Bootes. Between midnight and dawn intensities of up to 120 meteors per hour may be reached with little interference from the moon that has just set.

4 The Earth is at perihelion or its closest approach to the sun for the year. Brr. Moon in first quarter, 6:55 a.m.

10 The moon is at perigee or nearest approach to Earth. With the full moon occurring less than 24 hours later, astronomically high tides can be expected.

11 Full moon, 10:27 p.m. The full moon of January is known as the Wolf Moon, Old Moon or the Moon After Yule.

12 Regulus, the “heart” of Leo the Lion, is to the lower left of the moon as the heavenly bodies rise this evening.

14 Saturn is to the left of the moon looking to the east around 10:30 p.m. Venus is the brilliant “star” in the southwest at sunset.

18 Moon in last quarter, 9:46 p.m.

19 The sun is entering Capricornus on the ecliptic but, due to precession, astrologically is just entering Aquarius.

23 The moon is at apogee or greatest distance from Earth.

24 Jupiter undergoes conjunction with the sun and passes into the morning sky.

26 New moon, 2:55 a.m.

29 Look to the southwestern horizon at sunset to see the new crescent moon with Venus to its immediate upper left.

31 Sunrise, 6:56 a.m.; sunset, 4:42 p.m.

Send astronomical queries to Clair Wood at cgmewood@aol.com or care of the Bangor Daily News, Style Desk, P.O. Box 1329, Bangor 04402.

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