Deep Southern Skies for July 2015
Welcome to a monthly description of our northern NSW night sky for July.
Venus and Jupiter approach each other while Saturn is alone.
Venus and Jupiter very close.
Occultation of Venus by the Moon.
Blue Moon (two Full Moons in one calendar month).
2nd Full Moon.
6th Moon at perigee (closest to Earth at 367,093 km).
9th Last Quarter.
16th New Moon.
19th Occultation of Venus by the Moon, visible from NE Australia.
21st Moon at apogee (farthest from Earth at 404,835 km).
24th First Quarter.
31st Full Moon.
Mercury, in the eastern dawn sky, is only visible early this month as it descends towards the Sun and superior conjunction (Earth and Mercury on opposite sides of the Sun) on the 24th. Subsequently, this speedy little planet moves into the evening dusk sky joining the brightest planets Venus and Jupiter in early August.
Venus and Jupiter make a dazzling pair when they are just 0.4° apart on the 1st. They quickly separate but remain within 6° of each other for July in the early western evening sky within the boundaries of Leo. The 2-day old crescent Moon forms a triangle with the two brightest planets on the 18th. Venus reaches its greatest brilliancy on the 10th at -4.7 magnitude.
The Earth is at aphelion on the 7th, the furthest point in its orbit from the Sun (152,093,462 km).
Mars, now past conjunction, remains too close to the Sun to be seen till next month.
Jupiter begins the month just 0.4° from the brighter Venus in the early western evening sky - a spectacular sight! At this time Jupiter is -1.8 magnitude compared to -4.6 for Venus. On the 18th, the 2-day old slender crescent Moon forms a triangle with Jupiter and Venus. Jupiter’s motion across Leo takes it directly towards Leo’s brightest star, Regulus, and at month end the pair are 2.5° apart and even closer next month.
Saturn, in Libra, is visible high in the northeastern sky at the end of dusk. On the 26th, the 9-day old waxing gibbous Moon will be nearby the planet.
Uranus rises around midnight in Pisces mid-month. On the 27th, the planet appears stationary against the background stars and thereafter is in retrograde motion until late December. Whilst it is moving very slowly at this time it will be close to the 5th magnitude double star Zeta Piscium and will remain within 0.5° of this star through to early September.Zeta is a fine double star and the best in the constellation of Pisces for small telescopes.
Neptune rises in the mid-eastern sky in Aquarius.
Dwarf planet Pluto, is at opposition on the 7th, and above the horizon the entire night. It is presently 4,770 million km from Earth, with its light taking four hours and twenty-five minutes to reach us, but at 14th magnitude only large telescopes have a chance of seeing it.
Pluto at Last. New Horizon’s Historic Flyby
Long time coming. No one knows what NASA’s New Horizons spacecraft will find when it views Pluto and its moons up close for the first time, but the July 14th flyby is certain to be exciting. Beyond any planet that has been explored before lies the frozen “Third Zone” of the solar system: the Kuiper Belt. It’s dark, cold, and sluggish, a place so remote that its small icy inhabitants take hundreds of years to complete a single orbit of the distant, dim Sun. Only a handful of Kuiper Belt objects have ever been seen from Earth and none of those as anything but vague smudges. But after nearly a decade of interplanetary travel, NASA’s New Horizons spacecraft will see, up close, the region’s most famous member: Pluto. New Horizons is a flyby mission. At 11:50 Universal Time on July 14, it will zip past Pluto at nearly 14 kilometres per second, never to return. The mission’s highest priority goals are to map the global geology of Pluto and its moon Charon, to determine their surface composition, and to study Pluto’s wispy atmosphere.
Astronomy 2015 Australia. Quasar Publishing 2014.
Sky & Telescope July 2015.