Aphelion Day! Now it will slowly start to get warmer!

Wondering why it was so cold last night and at present?

It was Aphelion Day. The exact time of Aphelion here in Coonabarabran was 9:54pm last night. At that time distance from the centre of the Earth to the centre of the Sun was 152,095,295kms.

Earth orbits the Sun in an elliptical path, which means that there is exactly 1 point in time in the path when the Sun is at its closest to the Earth and another single point when it is furthest away. This latter was last night.

The winter solstice for us was 2 weeks ago

The Earth is closest to the Sun – at its Perihelion – about 2 weeks after the December Solstice and farthest from the Sun – at its Aphelion – about 2 weeks after the June Solstice. The perihelion will occur on January 3, 2021 at 12:50am when we will be only 147,093,163 km apart. Next July we will be slightly further away.

The words Perihelion and Aphelion come from ancient Greek, where peri means close, apo means far, and Helios means the Sun?

They are used in astronomy to refer to the closest and farthest points of the orbits of any object revolving around the Sun.

Together, they are called apsides – the points of least or greatest distance of a celestial object in orbit around another astronomical body.

The shape of the earths path or orbit has some variation due to the gravitational influences of other planetary objects, most particularly the Moon.

Approximately every 100,000 years, Earth’s orbital path changes from being nearly circular to elliptical. The difference of the Earth’s orbital shape from a perfect circle is known as it’s eccentricity.

An eccentricity value of 0 is a circular orbit, while values between 0 and 1 describe an elliptical orbit.

The actual date and times that the Earth reaches these maximum points on its orbit are not fixed. This is due to the variations in its eccentricity.

In 1246, the December Solstice was on the same day as the Earth reached its Perihelion. Since then, the Perihelion and Aphelion dates have drifted by a day every 58 years. In the short-term, the dates can vary up to 2 days from one year to another.

Mathematicians and astronomers estimate that in the year 6430, over 4000 years from now, the timing of the Perihelion and the March Equinox will coincide.

Donna the Astronomer

I am a keen astronomer lucky enough to live and work in Coonabarabran the Astronomy Capital of Australia! I am a ‘Drover’s Brat’ and discoverer of a couple of comets and asteroids. I operate Milroy Observatory and can show you how to best integrate dark sky experiences into your tourism, farm stay or AirBnB business.

This Post Has One Comment

  1. Ggreybeard

    I didn’t know the Earth’s orbital shape changes over time and progresses through the seasons. Very interesting, Donna, thanks!

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