The Earth has just completed another revolution around our star- the sun, which takes around 365.25 solar days. The extra 0.25 of a day results in a leap year every four years.

 

Today, 4th January 2023, at around 16:17 GMT, the Earth will be at perihelion for its solar orbit. This means that the Earth is at the closest point to the sun for this years orbit, which is 0.983295578 AU, or 147,098,925 km. AU, or astronomical units, is a way to determine distances in a near-range, relative to other astronomical distances such as light years or parsecs. AU is based on the mean distance from Earth to the sun, which is approximately 1 AU, or 150,000,000 km.

 

Because there is a closest point, there must also be a furthest point. In this case, the opposite to perihelion is aphelion, which is the furthest the Earth will be from the sun for that solar year. This year, it will occur on 6th july, at around 20:07 GMT, where Earth will be 1.016680584 AU, or 152,093,251 km from the sun. It is also important to note that the terms perihelion and apheleion is not just used to describe Earths orbits at a given time, but can be used for any planet, asteroid, or comet orbiting its star.

 

These two terms are important for understanding how orbits work, as we know orbits are elliptical, they suggest that every planet has points in their orbit where they are farthest or closest to their star. Like most celestial objects, Earths orbit isnt circular, which means it too has points in its orbit when it is farthest and closest to the sun.

 

When the sun was formed 4.6 billion years ago, it was surrounded by a chaotic, protoplanetary disc consisting of mainly hydrogen (75%) and helium (23%). 2% of this contained oxygen, carbon, silicon and nickel. These came together to form the planets cores. The gas planets were larger than the terrestrial planets, due to the large amount of ice present, as it was beyond the frost line. The gravitational forces of these collected more substances, and formed the planets we know today, which orbit the sun in an elliptical shape.

 

The sun is incredibly important in providing the right conditions to support life. Earth is in what we call the goldilocks zone, which, in our solar system, is between 0.95and 1.67 AU since temperature decreases the further away from the star you go. For this reason, Earth is close enough to the sun for water not to evaporate, and far enough so it doesnt freeze. Liquid water is excellent for life, as it is a good solvent and acts as a transport system for many nutrients.

 

However, the sun does prevent manned space exploration, due to the vast amount of solar radiation, which is not safe for astronauts- we are protected from it on Earth thanks to our atmosphere. For example, future missions to mars have to find a way around this, becaue of the thin atmosphere on mars.