Description

Northern Hemisphere

Ian Morison tells us what we can see in the Northern Hemisphere night sky during August 2020.

The Planets

• Jupiter. Visible throughout the hours of darkness and lying up to the left of the 'teapot' in Sagittarius, Jupiter reached opposition on July 14. It is now visible in the south-southeast as darkness falls and crosses the meridian, so highest in elevation, at 11:30pm BST at the start of the month and by 9:30pm by month's end. Its magnitude dims slightly from -2.7 to -2.6 during the month whilst its angular diameter falls from 47 to 44 arc seconds. Sadly, even when due south, it will only have an elevation of ~16 degrees above the horizon so the atmosphere will limit our views. A 'highlight' gives the times when the Great Red Spot faces the Earth.
  
• Saturn. Following Jupiter into the sky, some 8 degrees behind Jupiter as August begins, Saturn reached opposition on the 20th of July so, again, is visible throughout the hours of darkness - along with Jupiter dominating the southern sky in the late evening. Its magnitude drops slightly during the month from +0.1 to + 0.3 whilst its angular size decreases from 18.4 to 18 arc seconds. The rings span some 42 arc seconds across and, at 22 degrees to the line of sight, have opened out very slightly from previous months. Saturn lies in Sagittarius close to the boarder of Capricornus. Sadly again, its low elevation of ~16 degrees when crossing the meridian will somewhat limit our views of this most beautiful planet.
  
• Mercury is barely visible in the pre-dawn sky as August begins with a magnitude of -0.9 and a 6.1 arc second disk but, moving away from the Earth, passes behind the Sun on August 17th.
  
• Mars, in Pisces, can be seen towards the southeast at the start of the month rising 3 hours after sunset as August begins and 2 hours by its end. Its magnitude will rise from -1.1 to -1.8 during the month as its angular size increases from 14.6 to 18.7 arc seconds. It reaches an elevation of ~40 degrees as dawn approaches so amateur telescopes will enable one to see features, such as Syrtis Major, on its surface when the seeing conditions are good.
  
• Venus rises about 2am in the north north-east throughout the month but, as the Sun rises later as the days pass, the interval between Venus-rise and Sunrise increases by about 20 minutes. It shines at magnitude -4.5 as August begins, dropping to -4.3 by month's end whilst its angular size shrinks from 27 to 20 arc seconds. During the same time its phase (the illuminated percentage of the disk) increases from 43% to 59% which is why the fall in magnitude is not that great. Venus reaches greatest elongation west on August 12th, some 46 degrees away from the Sun. In Taurus as August begins, it passes into the upper left of Orion on the 5th before moving into Gemini on the 13th ending the month some 9 degrees below Pollux, the head of one of the 'twins'.
  

Highlights

• August - a great month to view Jupiter. This is a great month to observe Jupiter which will be visible during all the hours of darkness. It lies in the southernmost part of the ecliptic in Sagittarius and, sadly, will only reach an elevations of ~16 degrees when crossing the meridian. An interesting observation is that the Great Red Spot appears to be diminishing in size. At the beginning of the last century it spanned 40,000 km across but now appears to be only ~16,500 km across - less than half the size. It used to be said that 3 Earths could fit within it, but now it is only one. The shrinking rate appears to be accelerating and observations indicate that it is now reducing in size by ~580 miles per year. Will it eventually disappear?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.
  
• August: Look for the Great Red Spot on Jupiter. A list on the 'Night Sky' page gives the best late evening times during August to observe the Great Red Spot which should then lie on the central meridian of the planet and so face the Earth. The times are in UT.
  
• August 1st - late evening: Jupiter, Saturn and a waxing gibbous Moon. In the late evening should it be clear, Jupiter will be seen towards the south above a waxing gibbous Moon with Saturn over to its left.
  
• August 9th - late evening: Mars above a waning Moon. Looking towards the south-east in the late evening, Mars will be seen up to the left of the Moon, 1 day before 3rd quarter.
  
• The mornings of August 12th and 13th - midnight to dawn: look out for the Perseid meteor shower. If clear, these mornings should give us a chance of observing the Perseid meteor shower - produced by debris from the comet Swift-Tuttle. The early morning of the 12th August will give us the best chance, if clear, of viewing the shower, but the peak is quite broad and so it is well worth observing on the nights before and after. Most meteors are seen looking about 50 degrees from the "radiant" which lies between Perseus and Cassipeia. On the 11th, the Moon, at third quarter, rises just after midnight so its light will begin to hide the fainter meteors. On the 12th and 13th it rises later and its phase will have reduced so its effects will be less. NB: As we need to view a very wide area of sky, normal binoculars would be of no use but the Vixen SG 2.1 x 42 that I have reviewed in the Astronomy Digest could be useful albeit over the smaller field of view of ~27 degrees.
  
• August 15th - before dawn : Venus below a very thin crescent Moon. Just before dawn on the 15th, and given a low horizon between the east and northeast, it might be possible to spot Venus below a very thin crescent Moon. Binoculars may well be needed, but please do not use them after the Sun has risen.
  
• August 31st - six minutes past 5am BST: Mars and the International Space Station. If it is clear before dawn on the 31st of the month, you could see (assuming Stellarium is right) the International Space Station pass very close to Mars at around 05:06:45 BST. Just under 30 seconds later it will pass the Pleiades Cluster.
  
• August 9th and 25th - evening: The Hyginus Rille. These evenings, should it be clear, are a superb time to view the Hyginus Rill as it will lie close to the terminator. For some time a debate raged as to whether the craters on the Moon were caused by impacts or volcanic activity. We now know that virtually all were caused by impact, but it is thought that the Hyginus crater that lies at the centre of the Hyginus Rille may well be volcanic in origin. It is an 11 km wide rimless pit - in contrast to impact craters which have raised rims - and its close association with the rille of the same name associates it with internal lunar events. It can quite easily be seen to be surrounded by dark material. It is thought that an explosive release of dust and gas created a vacant space below so that the overlying surface collapsed into it so forming the crater.
  

Haritina Mogosanu and Samuel Leske from the Carter Science Centre in New Zealand speaks about the Southern Hemisphere night sky during August 2020.

In August 2020 we have a couple of spectacular planets in the evening sky, Jupiter and Saturn, the centre of our galaxy climbs at zenith and with it all the beautiful deep sky objects that we are so looking forward to seeing every year. Unfortunately for us, although there are many meteor showers in the northern part of the sky, they are quite low on the horizon for us to enjoy them as northern hemispherians do. Here is what’s in the sky in August.

Planets

• Mars. With the launch of NASA’s Perseverance as well as the UAE’s and China’s Mars missions, all eyes are on Mars for the next few months. Our eyes will be on Mars as well because from now until October Mars is only going to get better and better in the night sky. At the start of the month it rises at just after 11pm in Pisces and is about 95 million kilometres away. At that distance it is 14.6 arcseconds in size, which is not much smaller than Saturn, less the rings.By the end of the month the red planet is still in Pisces and rising at just before 10pm and has got about 20 million kilometres closer to us. This will put Mars at a size of nearly 19 arcseconds in the eyepiece, bigger than Saturn and just under half the size of Jupiter. By early October it will be just over 60 million kilometres away and nearly 23 arcseconds in size. You’ve got two months to get used to observing the red planet and improving your imaging skills to capture the stunning details of the planet as it reaches opposition.When it is so close to Earth, you can even draw Mars as you look at it through a telescope. And the best thing about that is that the main feature that we see through the telescope, the top / or bottom of Syrtis Major is where Perseverance is headed to.
  
• Saturn. The two gas giants that are dominating the evening sky are also a great sight to see over August. Saturn rises between Capricornus and Sagittarius before sunset at around 4:20pm and by sunset is nearly 15 degrees above the horizon. At the end of the month it is rising two hours earlier so it is in a very favourable position for observing in the early evening. Opposition for Saturn is on 2 Aug 2021 so we’ve got a year to wait, though at 1.4 billion kilometres it is not going to look a lot different throughout the months.
  
• Jupiter rises about 40 minutes before Saturn in Sagittarius throughout the month and joins Saturn in a very favourable viewing position in the early evening, great for the astronomer who likes to get to bed early. A great feature of Jupiter is that you can witness an eclipse many times a month. One of these is from 9:18pm on 7th of August when you watch Europa disappear into the brightness of Jupiter followed by the shadow appearing on the planet’s disk at 10:25pm.
  
• Venus tracks its way closer and closer to the Sun in our early morning sky throughout the month. The brightest of the planets is visible just below Orion and ends the month near Procyon in Canis Minor. Mercury is heading behind the Sun as the month progresses so is not going to be visible except at the very start of the month, and then with some difficulty.
  

Constellations

• Scorpius has been dominating the night sky so far in Winter as it occupies the zenith in the evening. Now we are seeing Sagittarius rising higher and higher each night and dragging with it the constellation of Capricornus.
  
• We have some good news for the people who like golf. From New Zealand, the Capricorn, which is supposed to be a goat (capri) with one horn (corn), alluding to the legend of the horn of plenty, looks in fact exactly like a golf flag, yet a gigantic one.
  
• On the other side of Scorpius, Libra the scale is on a descending path onto the horizon and Virgo’s star, Spica is even closer to the horizon.
  
• In the morning, we are seeing the return to our skies of Orion, rising earlier and earlier each night. The season of Matariki is closed now and the Pleiades is also becoming more and more visible in the morning sky, rising at 3am.
  

Deep Sky

• Deep Sky objects are fantastic at this time of the year as the centre of the Milky Way reaches the zenith it brings up the amazing nebulae of Omega, Eagle, Triffid and Lagoon. Lagoon is an amazing nebula to view in a telescope with the large open cluster NGC 6530 next to the bright nebula. A short distance away in the Trifid Nebula or M20. It is easy to spot the distinctive shape that led to its common name.
  
• Heading down the Milky Way Way towards Scutum you’ll find the Omega Nebula, or M17, this is a bright nebula, easily visible in even modest telescopes. Not far from Omega you’ll find the much fainter Eagle Nebula, M16, which is home to the pillars of creation from the famous Hubble Space Telescope image of this nebula.