This is the Dudley Observatory Skywatch Line for Wednesday, June 3rd, and Thursday, June 4th, written by Louis Suarato.
The 95% illuminated, waxing gibbous Moon rises at 6:15 p.m. Wednesday. The star below the Moon Thursday night is the constellation Scorpius’ brightest, Antares. Antares, meaning “rival of Mars” because of its reddish color, is a variable star with its brightness ranging from magnitude +0.6 to +1.6, making it the 15th brightest star in our sky. Look for Mercury low over the west-northwestern horizon after dusk. As the sky darkens, you’ll be able to see the Gemini twins, Castor and Pollux, above Mercury. Mercury reaches its greatest eastern elongation at 24 degrees beyond the Sun at 9 a.m., Thursday. Venus is in inferior conjunction at 2 p.m., Wednesday, when the planet is between Earth and the Sun. Jupiter rises at 11:17p.m., followed by Saturn 16 minutes later and 4 degrees away from Jupiter. Both gas giants occupy Sagittarius. Look for the Great Red Spot to begin its transit of Jupiter beginning 14 minutes past midnight Thursday. Mars rises at 1:40 Thursday morning in Aquarius.
On June 3, 1769. James Cook, aboard the ship, The Endeavour, sailed to Tahiti to witness the Transit of Venus across the face of the Sun. Cook, and his team of naturalists, and scientists, along with others around the globe, would use a process known as parallax, to determine the size of Venus, and by comparison, other planets. Transits of Venus occur in pairs, eight years apart, and separated by 120 years. This would be the last opportunity for these scientists to view the Transit. That transit of Venus was followed five hours later by a total eclipse of the Sun. It was the shortest interval between a Transit of Venus and Total Eclipse of the Sun in history. Our last Transit of Venus took place in 2012. The next one will occur on December 10th and 11th, 2117.