December 22nd 2010, I was at my home wearing a sweater, covering myself with a blanket standing on the terrace of my house gazing at zillions of stars over my head trying to solve three celestial puzzles that looked to be posed by GOD over the next 25 days.
DECEMBER 22nd 2010
December 22nd, a special day of astronomical significance generally not known to many except if you have some interest in astronomy or sky gazing. It is the day when the people in the higher latitudes (Europe, Russia, North China, North America, Canada etc. ) experience the shortest day and the longest night. This day is referred to as the winter solstice. If you are thinking why will there be a shortest day, then you have landed on the right page to understand that.
Earth has an axial tilt of 23.45 degrees. The winter solstice occurs when the earth's axial tilt is farthest away from the sun. It is because of this axial tilt, the northern hemisphere will have winter and the southern hemisphere has summer and vice versa. The same axial tilt will cause the shortest day and longest night in northern hemisphere AND longest day and shortest night in southern hemisphere on this day.
One interesting question that might arise in your mind is why is it called Winter solstice even though southern hemisphere is enjoying its summer! Astronomical events are recorded w.r.t Coordinated Universal Time(UTC) which in essence is Greenwich Mean Time(GMT). Since Greenwich is in northern hemisphere, winter/summer solstice is named after the season that occurs in northern hemisphere.
JANUARY 4th 2011
Ten days after the solstice, into the new decade on January 4th 2011, partial solar eclipse was observed in Middle East countries like Dubai, Abu Dhabi, Muscat, UAE (United Arab Emirates), Qatar, Bahrain, Riyadh, etc. We have studied since school days that a solar eclipse occurs, when moon comes in between the sun and the earth i.e. All the three heavenly bodies stand in a single line. I want to share couple of interesting facts about eclipses which most people might not know. The orbit of the moon around the earth is tilted at an angle of 5.14 degrees from the plane of earth's rotation around the sun. The orbit of the moon intersects the earth's orbital plane at two points called the ascending node and descending node. When the moon is at either of these two points, the eclipse(solar/lunar) will occur. In Indian astronomy the ascending node is the all famous RAHU and the descending node is the all famous KETU.
Another interesting fact is that these nodes(rahu/ketu) are not static. They are regressing in the clockwise direction. This is because the oribit of the moon around the Earth is wobbling. It is because of the regressing, the eclipses do not occur periodically at a particular date every year.
JANUARY 15th 2011
Mostly known in India as Makara Sankranthi, Pongal, Bhogi etc, this day has been celebrated from the past 6000 years. It marks the beginning of the Uttarayana(travel to north).
Throughout the year if you keep recording the position of the sun w.r.t distant constellations which generally is the zodiac constellations, we can observe that the sun keeps moving from one zodiacal constellation to another which is seen as sun's background. The day when sun enters a new constellation, it is called a sankramana. Similarly on January 15th the sun enters the constellation of capricorn(makara), hence it is called the makara sankramana or sankranthi.
In this screen captured from stellarium, we can see the sun entering the Capricornus(makara) constellation
The zodiac belt which consists of 12 constellations circling the earth, through which the sun takes its yearly path appears to be tilted at an angle of 23.45 degrees because of the earths axial tilt as said in the beginning of the article.
(left)The zodiac symbols, (right)the zodiac belt tilted at an angle of 23.45 degrees from the orbital plane of the earth
The sun as it moves across the zodiac will have to take an ascending path and then the descending path. It is on January 15th the Sun starts its ascending path with respect to the zodiac i.e. its travel towards north and hence called the beginning of Uttarayana.
Next time when you look up at the sky, hope you will not miss anymore puzzles...
