This is the Dudley Observatory Skywatch Line for Wednesday, September 16th, and Thursday, September 17th, written by Louis Suarato.
The New Moon occurs at 7:00 a.m. Thursday. This is only about 26 hours before the Moon reaches perigee, it closest distance to Earth during this lunar cycle. Tides may be significantly higher, or lower, during this time. The Moon has little gravitational effect on water directly, because of water’s low mass. But, during the times of New Moons and Full Moons, the Moon’s gravitational pull causes the Earth to bulge underneath the oceans on the side facing the Moon, and also on the opposite side. As Earth rotates under those areas, we experience low tides. The sides of the Earth perpendicular to the Moon become elongated. As Earth rotates under those areas, we experience high tides.
Mars rises at 8:30 Wednesday night. The red planet continues to brighten as it approaches opposition on October 15th. Look about 13 degrees to the left of Mars to see the seventh planet from thew Sun, Uranus. You may be able to spot Uranus with the naked eye under optimal conditions, but a pair of binoculars offer better viewing. The distance between Earth and Uranus can be as close as 1.6 billion miles and as far as 1.98 billion miles. When you look at Uranus this week, it will be 1.77 billion miles away. Saturn and Jupiter shine 24 degrees over the southern horizon at astronomical twilight, when the Sun is 12 to 18 degrees below the horizon, and most stars can be seen. Astronomical twilight occurs at 8:36 p.m. Wednesday. The two gas giants set 40 minutes apart. Jupiter sets first at 58 minutes past midnight, and Saturn sets 1:38 a.m. Thursday. Take advantage of these moonless nights to observe the two planets before they get too low in the sky. There will be a bright International Space Station pass by the two large planets this Wednesday night. Look to the south-southwestern horizon at 8:13 p.m. Wednesday. Watch as the -2.8 magnitude ISS makes its way through Scorpius and Sagittarius before flying close by Jupiter and Saturn. The Space Station will then cross Capricornus before disappearing into Earth’s shadow in Aquarius. Venus rises at 2:59 Thursday morning. Look for M44, the Beehive Cluster, 13 degrees above Venus.