The size of the sun varies as seen from the Earth due to the variance in the Earth’s distance from it throughout the year. These two photos of the sun were shot by Leonard Ellul-Mercer from his observatory in Attard.

Make hay while the sun shines, they say. But contrary to what may seem logical, the summer heat is on not when the earth is closest to the sun, but rather, when it is furthest away!

In fact, the phenomenon of the seasons has very little to do with the distance between the earth and the sun. The seasons result mostly as a consequence of the fact that the earth’s axis is tilted (at an angle of about 24°), and so, during the summer months we get to face the sun for a much longer period of time, giving us early sunrises and late sunsets. The opposite thing happens during winter at this same period of time in the southern hemisphere.

On July 6, the earth reached its farthest point from the sun along its orbit, called aphelion. Six months earlier, on January 4 the earth was one-half orbit away, its closest to the sun, a position known as perihelion. The difference in both positions has been photographed by amateur astronomer Leonard Ellul-Mercer from his observatory in Attard. The composite image shows the two halves of the sun, at the same scale, one in January and the other last month.

The earth’s orbit is not a circle but an ellipse, so sometimes we are farther from the sun and sometimes closer. The same thing happens with the moon, on a much lesser scale, when it reaches its ‘apogee’ and ‘perigee’ positions once a month.

If the orbits of the earth and the moon were perfectly circular the sun or the moon would always appear to be the same size. But all planets follow elliptical orbits, as theorised by Johannes Kepler in the early 1600s. Kepler based his theories on the voluminous data about the positions of the planets as observed by Tycho Brahe, who did not use a telescope himself. Some say Kepler went ahead and stole the data after Brahe’s death.

Venus and Jupiter continue to be clearly visible in the west after sunset, however they will now get lower and lower. Look for them in the fading glow of sunset, about half an hour after the sun has set, just above the western horizon.

Ringed planet Saturn is still shining bright in the south, to the right of the upper part of the constellation Scorpius. Fiery orange Antares, the brightest star in Scorpius, shines brightly – but slightly fainter than Saturn – to the planet’s lower left.

The Perseid meteor shower will peak on the night of August 12. Remember to look for meteors in the darkest possible place – coastal areas are ideal as one can look out towards the sea. Keep in mind, however, that most meteors will only be visible after 2am as the earth rotates directly into the path of the meteoroids.

Further out in the solar system we find dwarf planet Pluto, which made the headlines in the past weeks as it was visited by a space probe for the first time since its discovery in 1930.

The latest images from the New Horizons probe suggest that Pluto has glaciers of nitrogen ice, as scientists believe they are seeing evidence of surface material having flowed around the mountains and even created lakes inside craters. Such activity may even be occuring right now, on a planet many thought was a geologically-dead object.

Astronomical events taking place this month

Alexei Pace is president of the Astronomical Society of Malta.