Description

Northern Hemisphere

Ian Morison tells us what we can see in the Northern Hemisphere night sky during June 2018.

The Planets

• Jupiter.Jupiter reached opposition on May 8th, so will be visible during the evening after darkness has fallen. It shines at magnitude -2.5 (falling to -2.3 during the month) and has a disk some 44 (falling to 41.5) arc seconds across. Jupiter's equatorial bands and sometimes the Great Red Spot (see 'highlights' for the times when it crosses Jupiter's central meridian) and up to four of its Galilean moons will be visible in a small telescope. Sadly, moving slowly westwards in Libra during the month, Jupiter is heading towards the southern part of the ecliptic and will only have an elevation of ~20 degrees when crossing the meridian. Atmospheric dispersion will thus hinder our view and it might be worth considering purchasing the ZWO Atmospheric Dispersion Corrector to counteract its effects.
  
• Saturn.Saturn, comes into opposition on the 27th of June and so will be visible during all the (few) hours of darkness. Its disk has an angular size of 18.2 arc seconds increasing to 18.4 during the month. Its brightness increases from +0.2 to +0.0 magnitudes as the month progresses. The rings were at their widest some months ago and are still, at 25.7 degrees to the line of sight, well open and spanning ~2.5 times the size of Saturn's globe. Saturn, lying in Sagittarius, is close to the topmost star of the 'teapot'. Sadly, it will only reach an elevation of just over 15 degrees above the horizon when crossing the meridian. Atmospheric dispersion will thus greatly hinder our view.
  
• Mercury.Mercury passes behind the Sun (superior conjunction) on the 5th/6th June but will become visible (at around magnitude -0.7) low in the west after sunset by mid-month. By month's end its magnitude will have dropped to -0.2 and it will set some one and a half hours after the Sun when it will have an angular diameter of 6.5 arc seconds. Greatest elongation west of the Sun is on July 12th.
  
• Mars.Mars, in Capricornus, beings its retrograde motion westwards on the 28th June as it moves towards its closest approach to Earth since 2003 in two months time. Mars rises at around midnight BST at the start of the month and around 10:30 pm by month's end. During the month Mars has a magnitude which increases from -1.2 to -2.1 and has an angular size of 15.3 increasing to 20.7 arc seconds so, with a small telescope, it will be possible to spot details, such as Syrtis Major, on its salmon-pink surface. It will only reach an elevation of ~14 degrees before dawn so, sadly, again the atmosphere will hinder our view.
  
• Venus.Venus dominates the western sky after sunset, shining brightly at magnitude -3.9 (increasing to -4.1 during month) with an angular size of 13 arc seconds increasing to 15 arc seconds as the month progresses. Venus rises a little higher in the sky during June, initially setting around two and a half hours after the Sun but a little less by month's end as its elevation at sunset stays at around 20 degrees. Venus starts the month in Gemini, not far below and to the left of Pollux, but passes into Cancer on the 11th when, on the 19th and 20th, it lies close to the M44, the Beehive Cluster.
  

Highlights

• June - a great month to view Jupiter.The features seen in the Jovian atmosphere have been changing quite significantly over the last few years - for a while the South Equatorial Belt vanished completely but has now returned to its normal wide state.
  
• June 1st ~2 am: Saturn close to a waning gibbous Moon.In the early hours of the 1st, the waning gibbous Moon will lie just up to the left of Saturn as they cross the meridian. [A good photo opportunity.]
  
• June 3rd ~2:30 am: Mars and a waning gibbous Moon.In the early morning of the 3rd, Mars will be seen down to the lower left of the gibbous Moon.
  
• June 8th, after sunset: Venus to the lower left of Pollux in Gemini.After sunset on the 8th and given a low western horizon Venus will be seen to lie in Gemini down to the lower left of Pollux.
  
• June 16th after sunset: Venus and a very thin crescent MoonAfter sunset, if clear, you may be able to spot a very thin crescent Moon lying over to the left of Venus. With binoculars or a telescope you might be able to see the 'Earthshine' which faintly illuminates the dark part of the lunar disk.
  
• June 28th ~2:30 am: Saturn and the Full Moon.In the early morning of the 28th, Saturn will be seen down to the lower left of the Full Moon - a nice photo opportunity.
  
• January 22nd/23rdth: Two Great Lunar Craters. These are two great nights (late evening on the 22nd) to observe two of the greatest craters on the Moon, Tycho and Copernicus, as the terminator is nearby. Tycho is towards the bottom of Moon in a densely cratered area called the Southern Lunar Highlands. It is a relatively young crater which is about 108 million years old. It is interesting in that it is thought to have been formed by the impact of one of the remnents of an asteroid that gave rise to the asteroid Baptistina. Another asteroid originating from the same breakup may well have caused the Chicxulub crater 65 million years ago. It has a diameter of 85 km and is nearly 5 km deep. At full Moon the rays of material that were ejected when it was formed can be see arcing across the surface. Copernicus is about 800 million years old and lies in the eastern Oceanus Procellarum beyond the end of the Apennine Mountains. It is 93 km wide and nearly 4 km deep and is a classic "terraced" crater. Both can be seen with binoculars.
  

Gaby Perez from the Carter Observatory in New Zealand speaks about the Southern Hemisphere night sky during June 2018.

• Introduction.Kia Ora, Gabriela Perez here from Space Place at the Carter Observatory in Wellington, New Zealand. It’s certainly getting colder down here as we approach the winter but the good news is that we have plenty of opportunities to look at our southern skies with all the extra dark hours. June is an incredible month for viewing the visible planets.
  
• Solstice.Mid month brings on the winter solstice on the 21st of June which in turn brings the longest night and the shortest day. It will also mean the Sun will be at its lowest elevation for the year.
  
• Summer Constellations.The beginning of the month will see the last of our summer constellations low in the western sky along with Sirius, the brightest true star, which will twinkle as in the early evening being found closer to the horizon. This twinkling occurs as the star's light will be dispersed as the atmosphere is denser nearing the horizon and we will see a bit of separation of colour. Rising in the East are some of our winter constellations such as Scorpius and Sagittarius. We don't have scorpions here in New Zealand so Scorpius is seen as the fish hook of Maui, with it's bloody bait, the red giant star Antares. Following Scorpius is Saggitarius and the zone between them, Sag A, marks the heart of our Milky Way. Winter in the Southern Hemisphere is a great time to see this 'bulge' of the Milky Way and in this zone astronomers believe to be a supermassive black hole helping to hold our galaxy together.
  
• The Planets.The first planet that will be visible in the sky before the sun has fully set is our 'evening star' Venus, it will be visible in the northwest in the constellation of Gemini and it will set about an hour after the sun. The next bright planet will be Jupiter in the east in the constellation of Libra which will remain in our skies until dawn. At about 9pm Saturn will rise in the southeast in the beginning of the month but will appear earlier and earlier each day in the constellation of Sagittarius. Following that will be the final planet to appear in our night sky which is the red planet Mars and we can find him in the constellation of Capricornus.
  
• Winter Constellations.The Southern Cross (Crux) will be at its highest point for the year and Achenar, marking the end of the constellation of Eridanus, the river, will be visible just above the horizon. The mid-point of these two objects marks the South Celestial Pole centre which you can use to find South. You can use Achenar to locate the faint constellation of Tucana, and within it a stunning and visible globular star cluster 47 Tucanae. The second brightest globular cluster out of the 150 that exist in the halo of our Milky Way. The brightest can be spotted using the pointer stars (Alpha Cen and Beta Cen) in the constellation of Centaurus, Omega Centauri.
  
• Pleiades.In mid June we will also have a sighting of the Pleiades star cluster in our dawn sky which has special significance in New Zealand as the heliacal rising of this cluster marks the time of the Maori New Year. It is found in the shoulder of the bull in the constellation of Taurus. It is a young star cluster, only 100 million years old, mostly consisting of giant hot blue stars. It is a rare sight to be able to pick out so many stars in an individual cluster in our night sky with the naked eye.
  

Hope everyone keeps warm and enjoys the extra hours of dark skies in the evening for some star gazing.