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Happy Perihelion

JamesF

By JamesF
in The Astro Lounge

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JamesF

JamesF

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Tomorrow morning at 5am the Earth reaches its nearest point to the Sun. From then on we'll be getting further away from it until early July. Not that there's a huge amount in it. A fair bit less than the radius of the planet, if I recall correctly.

James

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JamesF

JamesF

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The difference between apehelion and perihelion is 5 million kilometres, so a bit more than the radius of the planet... ;)

Ah, fair enough. For some reason I had it in my head that it was only about 5,000km.

James

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claire1985

claire1985

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nearest point to the sun in January and farthest point from the sun in July is not very great. Earth is about 147.1 million kilometers from the sun in early January, in contrast to about 152.1 million kilometers in early July.

That's quoted from the tinterweb so sorry if it's wrong x

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J_M_Franklin

J_M_Franklin

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James, I am curious as to why you think the Solstice took place this morning. The Solstice occurs between December 20th and December 23rd each year, the majority occur on the 21st, with a few on the 22nd, rarely on either the 20th or the 23rd.

The Solstice (Winter North of the equator and Summer South of the equator) on December 21st 2012 was the point in the earth's orbit when it was closest to the Sun, this occurred at 11:12hrs UTC. This was when the shadows were longest in the North and shortest in the south, it is also the shortest and longest days (North or South of the equator respectively) of the year. The Summer/Winter solstice for the North and South will be on June 22nd 2013 at around 0103:hrs UTC.

People often get the idea that the Gregorian Calender is in sync with the motion of the planet, but this could not be further from the truth, it is out by a considerable amount, and if we did not introduce leap years every 4 years it would get even more out of sync due to the irregular period that the Earth takes to orbit the Sun and return to the same point in the orbit, the so called tropical year (365.242199 days)

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JamesF

JamesF

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James, I am curious as to why you think the Solstice took place this morning. The Solstice occurs between December 20th and December 23rd each year, the majority occur on the 21st, with a few on the 22nd, rarely on either the 20th or the 23rd.

The Solstice (Winter North of the equator and Summer South of the equator) on December 21st 2012 was the point in the earth's orbit when it was closest to the Sun, this occurred at 11:12hrs UTC. This was when the shadows were longest in the North and shortest in the south, it is also the shortest and longest days (North or South of the equator respectively) of the year. The Summer/Winter solstice for the North and South will be on June 22nd 2013 at around 0103:hrs UTC.

I think it because it is so :) For example:

http://www.space.com/19090-earth-closest-sun-perihelion-2013.html

The solstices are not when the Earth is at its closest or furthest from the Sun. They are when the Sun reachest its greatest (or lowest, depending on how you look at it) altitude above the horizon and the other stuff you mention, but that does not coincide with the planet coming closest to nor furthest away from the Sun.

James

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JamesF

JamesF

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Sorry James. Wasn't posting that to contradict what you said, just to clear up any dispute. I agree though it is perihelion not solstice. Completely different things x

No problem. I was completely wrong about the difference in distance from the Sun anyhow :)

James

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