Tag Archives: aphelion

Earth At Its Closest to Sun For ALL Of 2017 — Evening Of Wednesday, January 4.

by Anura Guruge


Click to ENLARGE.

perihelion


This happens, like clockwork, each and every year.

It has to do with the Earth’s orbit, around the Sun, being an ellipse (as is nearly all orbital paths in the Solar System). With any and all elliptical orbits you always have a closest and furthest point from the object being orbited. These are known (by the Latin) Perihelion & Aphelion.

Earth’s Perihelion with the Sun occurs in January. The Aphelion in July. In each case it is about 2 weeks after the last Solstice. This is how things are right now. Kind of a coincidence.

But it means that the Southern Hemisphere ALWAYS gets a bit closer to the Sun than the Northern. In other words, when the Northern Hemisphere is tilted towards the Sun, the Earth is at its furthest. C’est la vie.

Anywho. In 2017, Perihelion was on January 4th.


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by Anura Guruge

This Weekends Much Hyped ‘Super Moon’ Is ‘Special’, But Not Earth Shattering. We Actually Have ‘3’, Yes ‘3’, In A Row!

Anura Guruge, June 8, 2013.

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by
Anura Guruge


Related post:
>> March 2013 ‘Worm’ Full Moon over
>> Alton — Mar. 30, 2013.

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The deal with a ‘Super Moon’ is that it is close to full (if not at full) and very close to Earth (if not at its closest).

Obviously we get a full moon each month, or to be precise each Lunar Month which is 27.322 days — rounded up to the ’28’ days that determine women’s cycles etc. So full moons, especially to Buddhists, are always ‘special’, but are really common or garden.

Being closest to Earth also happens each and every month — without fail. If it didn’t we would all be in a heap of trouble! Nearly all, if not all, solar system objects have non-circular orbits. Rather than circular the orbits that nearly everything falls into is an elliptical orbit — i.e., an elongated orbit. The degree of this elongation is referred to as Orbital Eccentricity, ‘0’ denoting a perfect circle and ‘1’ a parabolic (i.e., football shaped) orbit. Closer to ‘0’, the more circular, closer to ‘1’ the more elongated. Most of the planets have near-circular orbits, though they are not circular. Earth’s eccentricity is 0.0167. Mercury has the most elongated orbit at 0.2056, with Pluto, now a dwarf planet, having one of 0.248. Comets, which originate at the furthest edges of the solar system have very high eccentricity, Comet ISON, C/2012 S1 (ISON), having an eccentricity close to ‘1’!

The Moon’s eccentricity is 0.054906.

Here are some cute diagrams from ‘Google’ that will explain this whole notion of elliptical orbits, perigee and apogee. [When talking of orbits around the Sun the comparable terms used are ‘perihelion’ (closest) and ‘aphelion’ (furthest).

How the orbits of comets, in this case periodics which are NOT as elongated as long-term comets, compare in terms of the gas giants.

The Moon’s distance at perigee (which varies slightly from month to month due to some complicated precession motions) varies between 221,324.4 miles to 230,018.4 miles, the average 225,670 miles.

The apogee, on average, is at 252,088 miles.

So this weekend we get both a full moon and one that is at apogee — these two events happening very close together tomorrow morning between 7:11 am and 7:33 am in the Southern sky (very close to the horizon) over New Hampshire. I will be asleep. It will be quite spectacular tonight too. 

But, to be fair we had a Super Moon in May and another one in July — those the in both those cases the perigee was within 90% of closest as opposed to 100%. That is why tomorrow’s is more ‘special’ than most.

On AVERAGE we get 2 to 3 Super Moons each year — keyword here being ‘average’.

This weekend the brightness of the moon, measured per the confusing apparent magnitude scale which goes backwards [i.e., less NEGATIVE the brighter], will be ~ ‘-12.xx’. The maximum brightness of the full moon is -12.92; the average -12.74.

A real picture of the Moon orbiting the Earth taken by NASA robotic spacecraft ‘Deep Impact’, in 2005, from 30 million miles away.

 

Asteroid 2012 DA14 That Will Harmlessly Fly By Earth At A Distance Of 21,200 Miles On Friday, February 15, 2013.

Dec2013x125

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by
Anura Guruge


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Though many don’t realize this I spent quite a bit of time working on astronomy, these days even at the expense of Popes and cardinals.


Artistic rendition of 2012 DA14 passing by Earth on February 15, 2013.


Orbital diagram of the flyby.


This is Way Cool.

A dynamic orbit tracker from NASA’s JPL.
Try it out if you have Java installed.
Click to access JPL. [Orbit diagram], collapsed, will be at the top. You need Java.

Click to access JPL. [Orbit diagram], collapsed, will be at the top. You need Java.


It was discovered last year, on February 23, 2012, by a Spanish observatory.

It is an Earth-crosser asteroid that orbits the Sun every 366.2 days. Since it furthest point from the Sun, aphelion is beyond Earth’s orbit, crosses Earth’s orbital path twice a year. It has been probably been doing this for millions of years, though we now have precise data going back to August 1913.

It is not very big, about 160 ft across and weighing about 180,000 tons. It would do a fair amount of damage if it were to hit the Earth. It will not do so this year! But this is a record close approach. So much so that Earth’s gravity will perturb its orbital path reducing its orbital period by 51 days. That is a big deal.

There is an increasing chance that it might actually get around to hitting the Earth post 2080 — so 67 years from now. So our kids will have to keep an eye out. Asteroids of this size do hit the Earth every 1200 years or so. We are due. DA14 would not be the end of the World. It is too small. It could destroy a city. There was smaller asteroid that entered Earth’s atmosphere, above Russia, in 1908 and exploded in the sky before hitting the ground. It destroyed about 80 million trees over a 830 square mile area,

Earth At Its Closest To The Sun For All Of 2013 At Midnight (Eastern) On January 2, 2013. How Cool Is That?

Anura Guruge, laughing, picture November 16, 2011.

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..by Anura Guruge


Related post:
>>
Rejoice! Jump For Joy. The Winter Solstice Is Upon Us …
>>Dec. 20, 2012.


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 Earth’s orbit around the Sun and the key events. Click to access Wikipedia, the source of this diagram.


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.


These dates and times are from the U.S. Naval Observatory. Click to access. Enjoy.

These dates and times are from the U.S. Naval Observatory. Click to access. Enjoy.