By Clive Jackson
Welcome to the July night sky. This is the month with some of the warmest nights in the northern hemisphere and when the sky is fully dark, the summer Milky Way can be seen rising up from the southern horizon and passing practically overhead.
The Milky Way is, of course, our own galaxy seen from the inside and the centre of the galaxy is deep in the constellation of Sagittarius that can now be seen due south on July evenings.
On July 5, our planet Earth is at aphelion and that means it is in the part of its orbit most distant from the Sun, and this moderates slightly our northern hemisphere summer temperatures.
The bright planet Venus is visible low on the western horizon, soon after sunset in July, and on the 10th the two-day-old crescent Moon will be seen close to this planet.
Still looking to the west and high up in the early evening sky, the ringed planet Saturn can still be seen in the constellation of Virgo and on the night of the 16th the first quarter Moon will be close to this planet.
July is not so good for meteor showers, as the Moon is bright during the latter part of the month when the showers of shooting stars are most active. But from the last week of the month, the Capricornids are normally visible and these meteors are often bright yellow and may be visible through strong Moon light.
Almost directly overhead on summer evenings are the two constellations of Cygnus and Lyra. Between these two is an area of the Milky Way that the NASA space telescope called Kepler is searching for exoplanets.
Launched in 2009, this instrument has, up until now, found 132 planets in 76 star systems and more than 3,000 suspected planets are being investigated. On May 11, the instrument had a failure in its pointing mechanism that may finish the mission. But by any standards it has already been a dramatic success, with astronomers now being able to say, with confidence, that our galaxy contains at least as many planets as it does stars, resulting in up to 400 billion exoplanets. It is entirely possible that at least a billion of these could be habitable for humans.
The new Moon is on July 8, first quarter on the 16th, full Moon on the 22nd and last quarter on July 29.
Download the Algarve Skies Chart by clicking on the link below to download a PDF of the chart.
Clive Jackson is the Director of the Camera Obscura (next to the Castle in Tavira), specialising in education and public outreach.
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