Northern Hemisphere

Ian Morison tells us what we can see in the Northern Hemisphere night sky during July 2019.

The Planets

• Jupiter, shining initially at magnitude -2.6 and falling to -2.4, reached opposition on June 10th and is thus visible towards the south as darkness falls. Its angular size drops slightly from 45.5 to 43 arc seconds as the month progresses. Jupiter, in the southern part of Ophiuchus, is moving westwards in retrograde motion so moving towards Antares in Scorpius and will lie some 7 degrees up and to its left by month's end. A highlight gives the times when the Great Red Spot faces the Earth. Sadly it is heading towards the southernmost part of the ecliptic so, as it crosses the meridian, it will only have an elevation of ~14 degrees (From central UK). Atmospheric dispersion will thus take its toll and an atmospheric dispersion corrector would greatly help to improve our views of the giant planet.
  
  
• Saturn comes into oppositions on July 9th shining at magnitude +0.1 during the month so crosses the meridian around 1 am BST. Its disk is ~18 arc seconds across and its rings - which are still nicely tilted from the line of sight - spanning some 42 arc seconds across. Sadly, now in Sagittarius and lying on the southern side of the milky way, it is at the lowest point of the ecliptic and will only reach an elevation of ~14 degrees. As with Jupiter, an atmospheric dispersion corrector will help improve our view.
  
  
• Mercury might just be seen low in the west-northwest after sunset in the first few days of the month with a magnitude of 1.1 and an angular size of 9.4 arc seconds. To spot it, one will need a very low horizon and binoculars could well be needed to reduce the Sun's background glare, but please do not use them until after the Sun has set.
  
  
• Mars remains at magnitude +1.8 all month and is still just visible low in the west-northwest after sunset. Mars crosses Cancer during the month and passes into Leo on the 29th. Mars sets some one hour after the Sun at the start of July (with an elevation at sunset of ~9 degrees) but less than half an hour by month's end - when it will be very difficult to spot. Its angular size falls from 3.7 to 3.5 arc seconds during the month so one will not be able to spot any details on its salmon-pink surface. Binoculars could well be needed to reduce the Sun's background glare, but please do not use them until after the Sun has set.
  
  
• Venus with a magnitude of -3.9 rises less than one hour before the Sun at the start of the month with an angular size of 9.7 arc seconds but will be lost from our view around the 18th. Its elevation is only ~4 degrees at sunrise so a very low horizon just north of east is required and binoculars may well be needed to spot it through the Sun's glare - but please do not use them after the Sun has risen.
  
  

Highlights

• Early July: A very good time to spot Noctilucent Clouds! Noctilucent clouds, also known as polar mesospheric clouds, are most commonly seen in the deep twilight towards the north from our latitude. They are the highest clouds in the atmosphere at heights of around 80 km or 50 miles. Normally too faint to be seen, they are visible when illuminated by sunlight from below the northern horizon whilst the lower parts of the atmosphere are in shadow. They are not fully understood and are increasing in frequency, brightness and extent; some think that this might be due to climate change! So on a clear dark night as light is draining from the north western sky long after sunset take a look towards the north and you might just spot them!
  
  
• July - Find the globular cluster in Hercules and spot the "Double-double" in Lyra. There are two very nice objects to spot with binoculars in the south-eastern sky well 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!
  
  
• July 1st - before dawn: Venus and a crescent Moon. Given a very low horizon looking towards the northeast before dawn one should, if clear, be able to spot Venus lying over to the left of a very thin waning crescent Moon.
  
  
• July 13th - late evening: Jupiter near the Moon. In the late evening towards the south, Jupiter will be seen down to the lower right of the Moon, two days before full.
  
  
• July 15th - around midnight: Saturn and the Moon. Looking south around midnight, Saturn will be seen over to the left of the Moon one day before full.
  
  
• July 16th - after sunset: a partial eclipse of the Moon. Looking low in the southeast after sunset we might, if clear, be able to observe a partially eclipsed Moon. The partial eclipse will end around midnight BST.
  
  
• July 28th - before dawn: a crescent waning Moon and the Hyades Cluster. Before dawn on the 28th, a very thin crescent Moon will be seen to the left of the Hyades Cluster.
  
  

Haritina Mogosanu and Samuel Leske from the Carter Science Centre in New Zealand speaks about the Southern Hemisphere night sky during July 2019.

• A bit about July

  Welcome to our Latin section, which I am a big fan of as it's about the only thing that I can pronounce properly and without having to twist my tongue.

  July was the month when the Roman general and leader Julius Caesar was born and after he died the Roman Senate renamed Quintilis, the fifth month of the 10-month calendar into what today is July but of course it was not pronounced July but Iulius.

  July is the second month of winter in the Southern Hemisphere and obviously the second month of summer in the Northern Hemisphere. It's also the month where traditionally the government's financial year starts here in New Zealand. Not just the government experiences new beginnings but also we must add that end of June or July is when we observe the Maori New Year - Matariki.

  This is observed according to a lunar calendar, called Maramataka during the last quarter of the Moon that occurs after the solstice. We have a special guest today, Katie Paul from Rotorua who is a great friend of ours for all celestial events happening in Rotorua as well as for astrobiology. Katie is going to tell us a little bit about what Matariki as a New Year observance means for her and her people.

  We also get fireworks here in Wellington during Matariki. We wrote more in depth about when is Matariki or where to find Matariki/the Pleiades in the sky during this time of the year so check out our other posts. This time of the year is significant both in the evening/night and in the morning - usually we only discuss the evening or night sky.

• What's the Sun up to?

  The Sun rises around 7:50AM at the beginning of the month and 7:30AM at the end and sets from around 5:00PM at the beginning of the month to 5:20PM towards the end of it. The beautiful and long nights continue to enthrall us in July and the view to the Milky Way is the best. In July, the Sun transits the zodiacal constellations of the Gemini, switching to Cancer on the 22nd of July.

• The Milky Way

  This must be the best month of the year here in New Zealand in terms of stargazing as we can see the centre of our galaxy, all night long. Starting from the evening, when is rising in the south-east, the core of the Milky Way reaches meridian around 10PM and then sets in the west just before sunrise. With the centre of the galaxy come more stars, as we are looking towards the rotational centre of the Milky Way. The centre of our galaxy is in the direction of Sagittarius, Ophiuchus and Scorpius and lies at about 26,500 light years away from us. It is spectacular to think that we are actually looking in the direction of the radios ource Sagittarius A, which is in lay words the name for the supermassive black hole at the centre of our galaxy. At 4 million times more massive than our Sun, Sagittarius A is not visible to the naked eye and what we know about it comes from observations in gamma rays, infrared and radio wavelengths.

  In fact, most of the centre of the galaxy line of sight is covered in dust which is visible in the form of dark bands - they show up best in wide field photographs of the Milky Way. There's one tiny opening through this dust, of about one degree, which is known as Baade's Window, named after astronomer Walter Baade who observed it in the 1940s from Mount Wilson taking advantage of the city blackout during the war.

  The dust makes interesting shapes against the light that comes from the stars in the disk of the Milky Way and people around the world and throughout times imagined many creatures that inhabit our galaxy. A great example is the Emu that our neighbours, the Aboriginal Australians placed across the Milky Way, that is as big as the galaxy.

  Another example of dark creatures in the sky but on a smaller scale is the famous Prancing Horse nebula, which observed from the Northern Hemisphere does look like a horse. It also looks like a pipe or a donkey and of course, taking a huge leap all the way to the Southern Hemisphere, where everything in the sky looks upside down to what we see in the northern hemisphere, we have here a kiwi bird checking out the centre of the Galaxy.

  Kiwis are nocturnal birds, endemic to New Zealand, they feed with insects in the forest and they are an endangered species. The closest relative of the Kiwibird is the elephant bird from Madagascar. Warm blooded mammals such as cats, dogs, possums, all that was introduced in New Zealand are main predators for the kiwibird but they can also die from the loss of the habitat and worse of all, you're not going to like this, humans were the worst threat. I'm saying 'were' because there are now continuous efforts from the department of conservation to bring back the numbers. But one thing is certain, the kiwibird is one of the symbols of New Zealand and is the most loved bird here. And how amazing that is even embedded in the night sky - this bird that can only be seen active at night, how fitting that there's a kiwi bird at the centre of our galaxy.

  The Milky Way Kiwi

  A matter of perspective and of course coincidences, as you have to know what a kiwi bird is, led to the realisation that if you turn the horse upside-down you get a kiwibird. Ian Cooper, one of the first New Zealand's film astrophotographers told us how twenty five years ago, someone came up with the name. "It was during the height of film in astrophotography and before the rise of the internet, so it was a 'slow burner' as they say. It is thought that some 'independently' discovered the little bird more recently and got all excited understandably. It is a pity that we don't know who first coined the name "Milky Way Kiwi," but that is how it was in the olden days when I was young."

  Milky Way Kiwi is useful for when explaining where is Sagittarius A, as it's visually somehow on top of its head, just like a diamond on a crown.

  Other birds in July

  The birds in the sky this month are: The Milky Way Kiwi obviously, but also some proper constellations such as Corvus, Cygnus the swan also known as the Northern Cross, in the sky around midnight. Another northern flying bird is Aquila the eagle, rising just after 8PM . On the southern horizon is the Dove, Columba inbetween the Dog star, Sirius and the Cat star, Canopus. Delicate and rich in optical double stars that we can see with the naked eye, Grus the Crane, is another bird-constellation laying now on the South Eastern Horizon. And as much as I don't like them, Musca, the Fly also qualifies for a flying constellation. Near the southern cross, Musca looks like a small polygon. Near Musca, Apus, the bird of paradise's name literally means "no feet" in Greek, as it was once wrongly believed that the birds of paradise lack feet. Apus is pointing straight at Pavo the peacock, that is flaunting its feathers all over the south celestial circle. Next to Pavo, is Toucana, near the Small Magellanic Cloud (NGC 292). Toucana is neighbouring Grus on one side and the Phoenix, on the other side. Since Herodotus, the Greek historian, the bird of Phoenix was associated with the Sun, a phoenix obtains new life by arising from the ashes of its predecessor and it can live for 1400 years at the time. And there is also a flying fish: Volans. It's tail is pointing at the Large Magellanic Cloud and it's head is half way through between Miaplacidus and Avior in Carina. And last but not least, I don't know for sure if Unicorns can fly but I'm mentioning here just in case: the elusive Monoceros, the unicorn, just in case. It is between Sirius and Orion and its stars are so faint that I have always just barely made the shape of it. Monoceros is visible on the morning sky.

• Bright stars in the Milky Way

  Starting from the West and looking south after sunset is Sirius very low on the horizon then Canopus (which is not really in the Milky Way but is not far from it either) then following the Milky Way to the south are Suhail al Muhlif and Avior in Vela. High in the sky is the Southern Cross, which around mid-July and after sunset is at its highest position on the circumpolar zone. Alpha and Beta Centauri are to the left of the Southern Cross and on the south eastern horizon close to the centre of the Milky Way are Antares and Shaula in Scorpius, Nunki in Sagittarius and last but not least, after 10PM, Altair and Vega are just grazing the northern horizon.

• Orion and Scorpius

  Orion is both on the western horizon at sunset, the three stars of its belt plunging vertically into the ocean, Rigel to the left and Betelgeuse to the right touch down almost at the same time and Saiph is the last to sink. Then in the morning sky, will rise around 6AM, Rigel first, which here is known as Puanga or Puaka then the belt and last to appear is Betelgeuse. The heliacal rising of Puanga is the alternative to observing the Maori New Year as due to the mountain ridge to the east in the Taranaki region the Pleiades are too low in the sky.

• Bright stars on the ecliptic

  Nothing changed from last month, the same bright stars are on the ecliptic: Regulus from Leo (which is extremely close to the ecliptic) then Spica, the blue giant in Virgo, Zubenelgenubi, another star grazing the ecliptic and Zubeneschamali just beneath it. Zubenelgenubi means the northern claw and Zubeneschamali the southern claw, alluding to these two stars that have been the claws of Scorpius before they were chopped off and turned into the current constellation of Libra. They are followed by Antares in Scorpius which is both on the ecliptic and in the Milky Way, this is roughly where the planes of the two intersect.

• Circumpolar Objects to New Zealand

  The beautiful Southern Cross and the pointers are high in the sky. Gacrux and Acrux are crossing the meridian around 10 PM at the beginning of the month and just after 8PM at the end of it. Omega Centauri is in a great position to observe, as well as Musca, Vela, Carina and their Diamond Cross, and False Cross and the Large Magellanic Cloud and its Tarantula Nebula.

• Deep Sky Objects in July

  Close to the area south of the triangle that marks Leo's hips…M65, M66 and NGC 3628, which will be visible depending on the size of your binoculars they are also known as the "Leo Triplet". Also in Leo, M105 is an elliptical galaxy. Last but not least M96 another galaxy in Leo lies at about 35 million light years away.

  Notable deep sky objects in Virgo include the bright galaxies Messier 49, Messier 58, Messier 59, Messier 60, and Messier 87, the Sombrero Galaxy (M104), the Eyes Galaxies, the Siamese Twins, and the quasar 3C 273.

  Virgo has 11 Messier objects so you are in for a treat with this constellation. You can get a map and look for all these objects. Or, if everything else fails, simply take your binoculars and swipe the Milky Way from one edge to the other. You might not figure out exactly which objects you are looking at but you would definitely find amazing sights, especially in the region close to Carina. You will find there IC2602, NGC3114, NGC353, NGC2516 that are all open clusters then in Crux NGC4755 which is another open cluster, NGC2451 in Puppis and IC2391 in Vela.

  Lower down, Omega Centauri, is a globular cluster in Centaurus. In Scorpius there are the Butterfly Cluster, M7 open cluster and NGC6231 open cluster.

• Planets

  Jupiter is in the sky just after sunset followed by Saturn two hours later and they are regal to watch so sharpen your telescopes.