One of the most interesting celestial phenomenon takes place this month (actually as you are reading this article). Earth is at its closest approach to the sun for the year, referred to as perihelion, today.
Some readers may be scratching their heads right now, and asking themselves, “If we’re at our closest approach to the sun for the year right now, why isn’t the weather warmer?”
Well, the answer is that although Earth itself is closer to the sun (by approximately 5 million km) this month than it is in July when it is at aphelion or its farthest point from the sun, the northern hemisphere is actually tilted away from the sun at this time of the year. This reduces significantly the amount of direct sunlight striking the northern hemisphere, thereby inducing our winter weather.
It all has to do with celestial mechanics and Earth’s position in its annual, elliptical orbit around the sun. For people in the southern hemisphere (which is now tilted towards the sun), who are now experiencing summer, the weather there is just a bit hotter than our summers in the north. It is one of the strange, but amazing, quirks of our universe. Google perihelion and aphelion to learn more about these amazing phenomena.
Venus, our evening star, first appears in the southwest sky this month just after the sun sets. As darkness falls (about 45 minutes after sunset), it shines brilliantly well above the horizon. As January progresses, Venus will appear higher in the evening sky on successive nights. Watch the waxing, crescent moon slide passed Venus on the evenings of Jan. 25-26.
The other brilliant planet in the early evening sky is Jupiter, sitting high in the southeast sky as darkness falls. Jupiter is well placed for viewing through telescopes this month. Watch through the course of the month (and the next two months), as Jupiter and Venus move slowly towards each other in the night sky. They will cross paths in mid-March.
Mars makes his appearance in the late evening sky around 10 p.m. as January opens and earlier as the month progresses. The red planet nearly doubles in brightness and increases slightly in apparent size this month and is at its highest point in the southern sky by around 3-4 a.m. Though still too small to discern any surface or atmospheric features in anything but large telescopes, Mars is still an interesting planet to observe. Look for the waning, gibbous moon to the lower left of Mars on the morning of Jan. 14.
Majestic Saturn joins Mars in the night sky, rising in the east around 1:30 a.m. as January opens and about 11:30 p.m. by month’s end. Saturn’s ring system is tilted favourably towards Earth this month and is best observed when the planet is at its highest point in the pre-twilight of the southern sky. A decent-sized telescope should easily discern the Cassini Division between the two major rings.
Mercury, ever a challenge to see, makes a brief appearance low above the eastern horizon just before dawn (about a half hour before sunrise) during the first week of January. By the second week of the month, however, it is lost to view in the glow of the rising sun.
January’s full moon on Jan. 9 was referred to as the wolf moon by the native people of North America, as the wolves could often be heard howling clearly on the cold, crisp nights at this time of the year.
Until next month, clear skies and good hunting.
And a happy new year.
Events (AST)
Jan. 9 – Full (wolf) moon (3:30 a.m.)
Jan. 16 – Last quarter moon (5:08 a.m.)
Jan. 22 – New moon (3:39 a.m.)
Jan. 31 – First quarter moon (12:10 a.m.)
Glenn K. Roberts is a member of the Charlottetown Centre of the Royal Astronomical Society of Canada (RASC). His column appears in The Guardian once a month. He welcomes comments from readers. Anyone who would like to comment on his column is encouraged to email him at glennkroberts@gmail.com.
Article source: http://www.theguardian.pe.ca/Arts/2012-01-05/article-2855581/Bright-planets-usher-in-the-new-year/1
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