Month's planets

Venus blazes in the dawn sky from July through to August, while Mercury, Mars, Uranus and Neptune also take the morning watch

Venus blazes brightly in the morning sky from July through to August

Between mid-July and mid-August many summer sky-watchers will be able to see all seven of Earth’s sister worlds strewn across the sky. However, one planet will dominate the pre-sunrise sky, the world that many people know as the ‘morning star’ or ‘evening star’ and is often – very misleadingly – called ‘Earth’s Twin’. That planet is Venus, the closest planet to Earth.

Venus is the second planet out from the Sun, and earned its stellar nicknames from the way that it sometimes blazes in the west after sunset and at other times blazes in the east before sunrise. As for that other nickname, it couldn’t be less of a twin to Earth if it tried. Yes, it’s roughly the same size as our planet, so there is a similarity there, but its carbon-dioxide atmosphere would be poisonous to us, its acid rain would burn us and its furnace-hot surface temperatures would be lethal to us long before the crushing atmospheric pressure on its flat, rocky plains killed us. All of these inhospitable conditions are down to its thick, curdled atmosphere, which traps the Sun’s heat and pushes the temperature on its surface to over 400 degrees Celsius (752 degrees Fahrenheit).

Ironically it’s the same ugly, inhospitable atmosphere that makes Venus shine so brightly in our sky: the clouds in Venus’ atmosphere reflect the Sun’s light back into space like a mirror, making it shine brilliantly in our sky.

This month Venus will be visible in the east before dawn, looking like a brilliant electric bluewhite spark in the sky, far brighter than any other planet or star in the sky at that time. Venus will already be a very striking sight in mid-July, but as the mornings pass will become even more so. It will be at its best at the end of our observing period, when it will be rising at around 02:00 and visible right through until sunrise.

Venus won’t just be kept company by Mercury in the sky before sunrise this month. Look out for the waning Moon approaching and then passing Venus in mid-July. On the morning of 16 July the Moon will be shining just to Venus’ upper right. The following morning, on 17 July, the Moon will be shining directly above Venus, the two making a striking pair. On the next morning the Moon will have moved eastwards along its track and will be found to the lower left of Venus.