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THE NIGHT SKY FOR AUGUST 2016

Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during August 2016.

Highlights of the month


August - Find the globular cluster in Hercules and spot the "Double-double" in Lyra

There are two very nice objects to spot with binoculars high in the sky after dark this month. Two thirds of the way up the right hand side of the 4 stars that make up the "keystone" in the constellation Hercules is M13, the best globular cluster visible in the northern sky.

Just to the left of the bright star Vega in Lyra is the multiple star system Epsilon Lyrae often called the double-double. With binoculars a binary star is seen but, when observed with a telescope, each of these two stars is revealed to be a double star - hence the name.

August - A good month to observe Neptune with a small telescope.

Neptune comes into opposition - when it is nearest the Earth - on the 2nd of September, so will be well placed both this month and next. Its magnitude is +7.9, so Neptune, with a disk just 3.7 arcseconds across, is easily spotted in binoculars lying in the constellation Aquarius, as shown on the chart. It rises to an elevation of ~27 degrees when due south. Given a telescope of 8 inches or greater aperture and a dark tranparent night it should even be possible to spot its moon Triton.

August 1st after sunset: Jupiter, Mercury, Regulus and Venus form a line in the Western Sky.

Given a clear sky and a very low western horizon you may be able to spot a line of Jupiter, Mercury and Venus along with Regulus in Leo. Binoculars may well be needed, but please do not use them until the Sun has set.

August 5th after sunset: Jupiter and a thin waxing crescent Moon

As Jupiter slowly sinks into the Sun's glare, given clear skies and a low western horizon it should be possible to spot Jupiter up and to the left of a thin waxing crescent Moon.

August 23rd - after sunset: Saturn and Mars lie above Antares in Scorpius

Looking South-Southwest after sunset and given a low horizon in this direction you should be able to spot Saturn (+0.4) lying above Mars (-0.3) (both in Ophiuchus) close to Antares in Scorpius.

August 27th - after sunset: Venus and Jupiter less than half a degree apart.

Looking west after sunset and given a very low horizon in this direction, binoculars may help you spot Jupiter and Venus less than half a degree apart. But please do not use binocluars until after the Sun has set.

August 11th and 25th: The Straight Wall

The Straight Wall is best observed either 1 or 2 days after First Quarter (evening of the 11th August best) or a day or so before Third Quarter (evening of the 25th August best). To honest, it is not really a wall but a gentle scarp - as Sir Patrick Moore has said, "Neither is it a wall nor is it straight."

Observe the International Space Station
Use the link below to find when the space station will be visible in the next few days. In general, the space station can be seen either in the hour or so before dawn or the hour or so after sunset - this is because it is dark and yet the Sun is not too far below the horizon so that it can light up the space station. As the orbit only just gets up the the latitude of the UK it will usually be seen to the south, and is only visible for a minute or so at each sighting. Note that as it is in low-earth orbit the sighting details vary quite considerably across the UK. The NASA website linked to below gives details for several cities in the UK and across the world.

Find details of sighting possibilities from your location from the location index. See where the space station is now using the tracking page.

The Planets

  • Jupiter
    Jupiter can be seen low above the western horizon after sunset but throughout the month is sinking slowly into the Sun's glare. However as it does so, it makes some groupings with the crescent Moon, Mercury and Venus as highlighted above. It remains at magnitude -1.7 throughout August whilst its angular diameter reduces slightly from 32.1 to 30.9 arcseconds. Its low elevation will hinder our view of the giant planet but a small telescope should still show its equatorial bands and the Gallilean moons as they weave their way around it.
  • Saturn
    Saturn has its rings as nearly open as they can be and so still makes a great sight through a small telescope even though its elevation never gets above ~20 degrees. It dims slightly from magnitude +0.3 to +0.5 during August as its angular size falls slightly from 17.5 to 16.7 arcseconds. Saturn transits at sunset and so can be seen low in the south-western sky during the evening. With a small telescope one should also be able to spot its largest moon, Titan. As described in the highlights, towards the end of the month Saturn, Mars and Antares make a close grouping.
  • Mercury
    Mercury reaches greatest elongation from the Sun on August 16th but, sadly, never gets that high above the horizon in the western sky. It magnitude falls throughout August from -0.2 to +1.1 whilst its angular size increases from 6 to 9.5 arcseconds.
  • Mars
    As August begins, Mars, shining at magnitude -0.8, transits around sunset and so will be seen in the south-western sky during the evening as it moves first from Libra into Scorpius and then towards the end of the month into Ophiuchus. Its magnitude drops from -0.8 to -0.3 during the month as its angular size falls from 13 to 10.5 arcseconds. Sadly, its low elevation will hinder our view but it may still be possible to see some features on the surface with a small telescope if the atmospheric 'seeing' is good.
  • Venus
    Venus can be seen very low in the western sky after sunset so, despite its brilliant magnitude of -3.8, will still be hard to spot. Its angular diameter increases from 10.1 to 10.9 arcseconds during the month. On August 1st, it sets about 45 minutes after the Sun lying very close to the star Regulus in Leo. An interesting, but difficult observation due to its very low elevation on the 27th will find it less than half a degree away from Jupiter as both fall into the Sun's glare.

Haritina Mogosanu from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during August 2016.

Haritina Mogosanu from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during August 2016.

In the Southern Hemisphere, winter is the time when the galactic center goes right all the up at Zenith. All you have to do from here in Wellington, New Zealand is to lift up your gaze and it will be right there. From there, if there is a really dark night, you can see the Milky Way Kiwi, which I spoke about in last month's jodcast. It is a dark patch at the center of our galaxy, the Milky Way, that looks just like a Kiwi bird, one of the native birds of New Zealand, and a national icon for us. It is truly remarkable how the kiwibird in the sky resembles to the one on the earth. But since you need a really dark sky, I would suggest that the best thing you can do to try spot the Milky Way Kiwi is to start looking for it in long exposed pictures of the night sky. The only place in New Zealand where I could see it with the naked eye was at Lake Tekapo's Earth and Sky. Whereas the Milky Way Kiwi is in the Scorpius Sagittarius region, holding the center of the galaxy on its head like a crown, the other famous dark patch is the Coalsack, near the Southern Cross. The coalsack is also known as the flounder, which is the Maori name for it. In deed, again if you find a truly dark sky, you will see the resemblance. However, talking about naming objects in the sky, the coalsack is also very appropriate as the dark patch, made of interstellar dust matter holds inside it a jewelbox, or the Kappa Crucis Cluster, NGC 4755. This is an open cluster in the constellation Crux, originally discovered byNicolas Louis de Lacaille during 1751-1752 and named the Jewell box by Sir John Herschel. He described its telescopic appearance as "...a superb piece of fancy jewellery". Jewel box is easily visible to the naked eye as a hazy star about 1.0 degrees southeast of the first-magnitude star Beta Crucis.

In August, after sunset, the Southern Cross, Crux, and the two pointers, Alpha and Beta Centauri, are slowly starting their descent on the south celestial carousel, our special part of the sky that is not visible from Northern latitudes above 30 degrees. They are midway down the southwest sky. The pointers point down and rightward to Crux the Southern Cross. Alpha Centauri is the third brightest star and the closest naked eye star-neighbour, 4.3 light years* away. Beta Centauri, like most of the stars in Crux, is a blue-giant star hundreds of light years away and thousands of times brighter than the sun.

There is a part of the sky here in Wellington that seems to rotate around the South Celestial Pole, the extension of the South Pole in the sky, located here at 41 degrees above the horizon. This coincides with Wellington's latitude, 41 degrees South. You can almost make the South Celestial Circle from the two pointers, Alpha and Beta Centauri, the Southern Cross, the Diamond Cross, the False Cross, then lower down on the south-western horizon Canopus, the second brightest star in the sky, and Achernar, which is easily found if you exend a line from the southern cross all the way to the southeastern horizon. The South Celestial Circle makes an entire rotation in 23 hours, 56 minutes and just about 4 seconds, which is a sidereal day. This is a "time scale that is based on Earth's rate of rotation measured relative to the fixed stars" rather than the Sun. The south celestial circle is home to the Large and Small Clouds of Magellan LMC and SMC that look like two misty patches of light low in the south, easily seen by eye on a dark moonless night. They are galaxies like our Milky Way but much smaller. The LMC is about 160000 light years away; the SMC about 200000 light years away. My two favourite objects inside the south celestial circle are the globular cluster 47 Tucanae (rival of Omega Centauri) and the Tarantula Nebula, a spectacular cloud which is one of the most active starburst region known in the Local Group of galaxies. To give you an comparison, the Tarantula Nebula is about 160 000 light years away from us. Its luminosity is so great that if it were as close to Earth as the Orion Nebula, the Tarantula Nebula would cast shadows. The South Celestial Circle never ceases to amaze me and I watch it as it rotates with the seasons and througout the night when I can. For me, the southern part of the sky, is the best and I am extremely happy that i had the chance to see it, let alone now teach about it.

Back to the ecliptic, which is visible from everywhere where people can see the Sun and the Moon, as it is defined as the path of Sun but also as the plane of our Solar System, all five naked-eye planets are visible in the early evening sky. Mercury, Venus and Jupiter are low in the west and shuffle around through the month. Mars and Saturn are north of overhead near Antares.

Venus, the brilliant silver 'evening star', sets in the west an hour after the sun at the beginning of the month, extending to nearly two hours by the end. Jupiter, higher in the west and golden-coloured, sets steadily earlier through the month: at 9 pm at the start of August and before 8 pm at the end. Mercury makes its best evening sky appearance of the year. It is roughly midway between Jupiter and Venus at the beginning of the month. Around the 20th Mercury will be left of Jupiter but much fainter. It begins to sink back into the twilight at the end of the month. On August 27-28, Jupiter and Venus will be close together, easily included in the same view in a telescope. At the beginning of August, Mars, Saturn and Antares make an isosceles triangle north of the zenith. Mars is the brightest of the three and the same colour as Antares. Saturn is cream-coloured. Saturn stays put against the background stars. Mars moves steadily eastward. On the 25th Mars will be two degrees, four full-moon diameters, from Antares making a striking pairing of orange stars.

Bright stars are widely scattered. Vega on the north skyline is balanced by Canopus low in the south. Orange Arcturus is in the northwest. The Southern Cross, Crux, and the Pointers are midway down the southwest sky. The Milky Way spans the sky from northeast to southwest. Canopus, the second brightest star, is near the south skyline at dusk. It swings upward into the southeast sky through the morning hours. On the opposite horizon is Vega, one of the brightest northern stars. It is due north in mid-evening and sets around midnight. Arcturus, Hokulea, the Zenith star of Hawaii is in the northwest at dusk. The fourth brightest star, Arcturus is currently the brightest in the northern hemisphere. It is 120 times the sun's brightness and 37 light years away. When low in the sky Arcturus twinkles red and green as the air splits up its orange light. It sets in the northwest around 10 pm. Antares marks the heart of the Scorpion. The Scorpion's tail hooks around the zenith like a back-to-front question mark. Antares and the tail make the 'fish-hook of Maui' in Maori star lore. The fishing hook drags at this time of hte year the Milky Way down from the heavens. Antares is a red giant star 600 light years away and 19000 times brighter than the sun. Below or right of the Scorpion's tail is 'the teapot' made by the brightest stars of Sagittarius. It is upside down in our southern hemisphere view.

The Milky Way is brightest and broadest overhead in Scorpius and Sagittarius. In a dark sky, it can be traced down past the Pointers and Crux into the southwest. To the northeast it passes Altair, meeting the skyline right of Vega. The Milky Way is our edgewise view of the galaxy. The thick hub of the galaxy is in Sagittarius 30000 light years away. The actual centre is hidden by dust clouds in space. The nearer dust clouds appear as gaps and slots in the Milky Way. Binoculars show many clusters of stars and some glowing gas clouds in the Milky Way.

According to Karen W. Pierce who made an excellent list of binocular objects that you can find on the site astrogeek.com, in Ophiuchus, you can find M9, M10, M12, M14, M19, and M6, which provide examples of different concentrations of stars. Also visible is IC 4665, a big but often overlooked open cluster located near Beta Ophiuchi. On a dark night, it is visible to the naked eye as a hazy splotch nearly I degree across.

Sagittarius contains more Messier objects than any other constellation. The best way to identify them is to take them one by one. The main stars of Sagittarius form the famous "Teapot" asterism, which here in Wellington looks upside down. It is said that for the Norhtenlings, the brightest part of the Milky Way seems to emerge from the Teapot's spout like a puff of steam. In Sagittarius, M22, the Great Sagittarius star cluster is a very large globular — the best of the constellation's many globulars. At magnitude 5.1 it is an easy binocular object. M23 is another one of the many clusters in Sagittarius. M23 presents over 100 stars in an area about the size of the Moon. The Lagoon Nebula, M8, is visible with the naked eye in dark nights just north of the richest part of the Sagittarius Milky Way. The Trifid Nebula, M20, is found only 1 1/2 degrees northwest of the Lagoon Nebula. Ideal conditions and sharp eyes might detect M21, which is located just 1/2 degree northeast of M20, although it is rather faint by binocular standards. Omega Nebula, also called M17 or the Swan, the Horseshoe or the Checkmark, can be seen clearly in binoculars. In Scorpius, Antares, or Rehua in Maori, is the Heart of the Scorpion. A red giant star about 10000 times more luminous than the Sun is a good binocular object. M4 is a globular cluster that in binculars looks like a fuzzy patch. M6, the Butterfly Cluster, is a large open cluster of about 50 stars resembles a butterfly. M7 is a large, bright open cluster that lies southeast of M6 but needs to be seen through binoculars to be fully appreciated. NGC 6231 is a bright open cluster that lies in a rich region of the Milky Way. It is best surveyed in binoculars or at very low power in a telescope. In this same area of the scorpion's tail are several other binocular-visible objects but I will let you discover these, as that region of the sky comes about and remember that you don't need fancy telescopes to enjoy the night sky but a pair of good bionculars a good sky atlas and lots of hot chocolate. It's winter time here in the Souther Hemisphere and the nights are crisp but cold. Keep warm and look up.

Compiled by Ian Morison