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Later in the evening the Summer Triangle is overhead. This is a prominent triangle formed by the bright stars Altair, to the South of the triangle, Vega, closest to the Western horizon, and Deneb, to the East. Deneb forms the tail of the cross-shaped constellation Cygnus, the Swan. From our perspective the 3 stars have similar brightness. However they lie at different distances from Earth. Deneb is an extremely luminous star at 1400 light years from Earth whilst Vega and Altair are less luminous and are both much closer to Earth at a distance of about 20 light years. The familiar seven stars of Ursa Major, the Great Bear or Plough, are to be seen in the north-west, with the “W” of Cassiopeia climbing into the north-eastern sky. The brilliant planet Venus dominates the evening sky to the West. Although a beautiful sight as viewed from Earth, Venus is not a very inviting place to visit. With a surface temperature of over 400 degrees C, hot enough for rocks to glow, and a thick sulphurous atmosphere, it won’t be appearing on the travel web-sites just yet! In the middle of the month the crescent moon is a useful pointer to the planets. In the evening twilight of the 14th, 15th and 16th the Moon is just below Venus, Mars and Saturn respectively. At the end of the month, the 3 planets are close together, with Saturn just above Mars. On the 31st the Moon sits above the planet Jupiter to the south in the dawn sky. Dave Thomas | Home Page | |