..by Anura Guruge
I assume that most of you remember or realize that all of the planets in our Solar System have elongated, i.e., elliptical, orbits, as opposed to those that are perfectly circular — with the Sun in the middle.
Planetary orbits, as with the orbits of most celestial bodies, thus have a perihelion and aphelion, i.e., ‘periapsis‘ & ‘apoapsis‘, the nearest and furthest points from the body being orbited; in the case of the planets, this being the Sun.
Given the length of the year, i.e., the time taken for Earth to complete a full orbit of the year, viz. ~365.25 days, the perihelion and aphelion days change from year to year, and contrary to what you would expect they are not related to the two solstices.
This diagram, from Wikipedia, illustrates all the relationships quite nicely:
The 2013 perihelion occurs at 5 am UTC/GMT on January 2, 2013. Since U.S. Eastern time is -5 hours from UTC/GMT, it means that perihelion occurs at midnight, as January 1, 2013 turns into January 2. I think that it is neat.
For those in other U.S. time zones, even Central, the perihelion will occur on New Year’s Day, January 1, 2013.
Yes, the Sun, if you look at it (taking the mandatory precautions) tomorrow, will be bigger. It will continue to be big for a couple of months.
Here is a list of the key Solar dates for 2013, relative to what they were in other years.