Deep Southern Skies #309
Welcome to a monthly description of our northern NSW night sky for August.
Mercury close to Jupiter and Regulus.
Mars crosses the Beehive Cluster.
Comet Catalina in the southern evening sky (only visible in telescopes).
2nd Moon at perigee (closest to Earth at 362,139 km).
7th Last Quarter.
15th New Moon.
18th Moon at apogee (farthest from Earth at 405,848 km).
23rd First Quarter.
30th Full Moon.
31st Moon at perigee (closest to Earth at 358,290 km).
Mercury emerges into the western evening twilight this month, joining the two brightest planets, Venus and Jupiter. The planet moves up ever closer to Jupiter and on the 7th will be just 0.6° north (right) of the gas giant with the 1st magnitude star Regulus 1° above the pair and forming a triangle. On the 16th, the young 2-day old slim crescent Moon appears near the planet. This also marks the best time to observe Mercury in the evening sky.
Venus is visible in early August to the south (left) of Mercury and Jupiter, easily outshining both of them. After disappearing into the Sun’s glare and inferior conjunction on the 16th, it reappears in the eastern dawn sky as the Morning Star in the last week of August.
Mars reappears in the eastern dawn sky this month. On the 13th, the slender crescent waning Moon appears above the red planet. On the 20th and 21st, Mars traverses M44, The Beehive Cluster. Visible to the unaided eye under dark skies, the Beehive has been known for thousands of years and Hipparchus catalogued it as the little cloud in 130 BCE. Galileo was the first to realise its true nature when he observed over 40 stars in the cluster in 1609. Today, a good pair of binoculars will reveal at least 75 stars.
Jupiter follows Venus into solar conjunction this month but can still be glimpsed early in the month as it moves through Leo in the western early evening twilight. On the 7th, Jupiter and Mercury appear 0.6° apart forming a triangle with the 1st magnitude star Regulus, with Jupiter being the brighter of the two. After Mercury moves on, Jupiter moves ever closer to Regulus coming within 0.4° of the star on the 11th. Thereafter, the planet gets lost in the dusk sky as it travels towards the Sun and conjunction on the 27th, reappearing in the morning sky late September.
Saturn, moving slowly through Libra, is visible in the early evening northern sky. The planet appears stationary on the 3rd as it comes to the end of its 4.5 month long retrograde loop; it then resumes its west to east motion across the sky as it heads towards Scorpius. On the 22nd, Saturn will be at its highest altitude in the sky and the near First Quarter Moon appears close to the planet.
Uranus rises in the late evening sky in Pisces. The planet, with a greenish hue, remains close to the 5th magnitude double star, Zeta Piscium, making for a fine sight in small telescopes.
Neptune rises in the east at the end of dusk mid-month. At opposition on 1 September, the planet is at its brightest at 7.8 magnitude and though dimmer than Uranus, is still easily identified in a telescope with its bluish disc.
Comet C/2013 US10 (Catalina) begins August deep in the south in Tucana at 8th magnitude. Visible throughout the night, Catalina rapidly moves through the constellations Indus, Pavo and Apus before finishing the month somewhat brighter in Triangulum Australe. With New Moon on the 15th, mid-month is a good time to observe comet Catalina through binoculars or a small telescope.
New Moon favours the peak of the two showers described below but are, unfortunately, not easily observable as the radiant will be below the horizon.
The famous Perseids are the most dependable of the showers and their duration is from 17th July through to 24th August with a maximum predicted for the 13th. The hourly rate in 2005 was 90 meteors per hour and this year could be no exception.
The kappa-Cygnids are not as well known and are active from 3rd to 25th August with a maximum rate predicted for the 25th, infrequent and faint but sometimes producing white/bluish fireballs.
Astronomy 2015 Australia. Quasar Publishing 2014.
Sky & Telescope July 2015.
The SkyX Professional Edition