The Night Sky This Month

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Ian Morison tells you what can be seen in the night sky this month.
Updated: 7 hours 28 min ago

The night sky for August 2017

Fri, 11/08/2017 - 14:00
Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during August 2017.

The Planets
  • Jupiter Now four months after opposition, Jupiter can still be seen low in the southwestern sky after nightfall. It sets at about 1 am BST as July begin. As the month progresses its brightness falls from -1.9 to -1.7 magnitudes as its angular size falls from 34 to 32 arc seconds. It lies in Virgo, initially some 8 degrees to the west of Spica, reducing to 4 degrees as the month progresses and will pass Spica on September 11th on its journey towards the lower parts of the ecliptic. Next year it will only reach an elevation of some 25 degrees when due south and, in the following two years, just 18 degrees before it moves back towards the more northerly parts of the ecliptic. Even so, with a small telescope one should easily be able to see the equatorial bands in the atmosphere, sometimes the Great Red Spot and up to four of the Gallilean moons as they weave their way around it.

  • Saturn came into opposition on June 11th and so will be at its highest elevation due south as darkness falls. It shines initially at magnitude +0.3 falling to +0.4 during the month and has an angular size of ~17 arc seconds. With an angle of 26.8 degrees inclination to the line of sight, the rings are virtually as open as they ever can be. Their maximum tilt, at 27 degrees, will come in October - the first time since 2002. Saturn ceases its westwards, retrograde, motion on August 25th. It is sad that Saturn, now lying in the southern part of Ophiuchus between Sagittarius and Scorpius, only reaches an elevation of ~17 degrees above the horizon when due south so hindering our view of this most beautiful planet. If imaging Saturn (or Jupiter), Registax 6 has a tool to align the red, green and blue colour images to largely remove atmospheric dispersion from the image. At somewhat over £100 one can purchase the ZWO atmospheric dispersion corrector which uses two, contra rotating, prisms to carry out an even better correction - and which can also be used for visual observing.

  • Mercury Given a very low western horizon, Mercury, showing an 8 arc second disk and shining at magnitude +0.4 might just be seen after sunset at the beginning of August. Binoculars may well be needed but please do not use them until after the Sun has set. It passes between the Earth and the Sun (inferior conjunction) on August 26th.

  • Mars passed behind the Sun in July, but will be hidden in the Sun's glare all month so cannot be observed.

  • Venus is visible in the east before dawn this month, rising around 3 hours before sunrise. Its magnitude dims slightly during the month from -4 to -3.9 as its angular diameter shrinks from 14.5 to 12.5 arc seconds. However, at the same time, its illuminated phase increases from 74 to 83% which explains why the magnitude does not drop too much. Its elevation before sunrise is greatest on August 2nd when Venus lies close to the open cluster M35 in Gemini.

  • Highlights of the Month

    August - Find the globular cluster in Hercules and spot the 'Double-double' in Lyra. 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 arc seconds 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 transparent night it should even be possible to spot its moon Triton. (This is my objective around the end of the month!)

    The Moon and Saturn - Late evening on the 2nd of August, the waxing Moon will be seen to the upper right of Saturn. Antares lies down to its lower right.

    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 Cassiopeia. This year a gibbous Moon rises before midnight so will be low in the sky for some time the early hours of the 12th so it will be best to observe them as soon as it is really dark. Moonlight will hinder our view, but it should still be possible to spot many meteors. 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 just reviewed in the Astronomy Digest, could be useful as they will darken skylight from the Moon somewhat and enable fainter meteors to be seen - albeit over a smaller field of view.

    16th August 07:40 - 08:40 BST: A daylight Occultation of Aldebaran - In the early morning of the 16th, Aldebaran will be occulted by the Moon - visible with a telescope (but keep it well away from the Sun). The times are for London and will vary somewhat across the country. In a line from Leverburgh on the Isle of Harris across to Wick, a grazing occultation will be seen at 8:01 BST.

    19th August - before dawn: Venus and a thin crescent Moon - Before dawn on the 19th, if clear, Venus will be seen just 2 degrees above a very thin waning crescent Moon.

    25th August - after sunset: Jupiter below a thin crescent Moon - After sunset on the 25th, if clear, Venus will be seen below a thin waxing crescent Moon.

    August 14th and 30th: The Straight Wall - The Straight Wall, or Rupes Recta, is best observed either 1 or 2 days after First Quarter (30th August: evening best) or a day or so before Third Quarter (evening of the 14th August best). To honest, it is not really a wall but a gentle scarp - as Sir Patrick has said "neither is it a wall nor is it straight"!

    Claire Bretherton tells us what we can see in the southern hemisphere night sky during August 2017.

    Kia ora and welcome to the August Jodcast from Space Place at Carter Observatory in Wellington, New Zealand.

    The Planets
    • Mercury finishes its best evening appearance of the year this month. At the beginning of August it sits low in the west after dark, just above Regulus, the brightest star in Leo, setting around 7:45. By mid month it will disappear from view, lost in the evening twilight as it heads back towards the Sun in our skies. Jupiter is a little further north, midway up our northwestern skies. It is slowly moving below and towards the right of Spica over the course of the month. Both are quickly dropping down our evening skies, with Jupiter setting at around 11pm at the beginning of August, but by around 9:30 at the end.

    • Saturn - Further around still, Saturn is high in the northeast after dark, with Antares above and to the left, and remains in our sky for most of the night. A waxing gibbous moon passes close to Saturn on the 3rd and 31st of the month, whilst on the evening of the 25th, a thin 3 day old crescent Moon will sit just below Jupiter.

    • The Moon - On the 22nd of August the Moon will pass directly between the Earth and the Sun, causing a total Solar eclipse. The eclipse path will run across the United States, but unfortunately no part of it will be visible from New Zealand. The next total Solar eclipse visible from our shores won't be until July 2028.

    • Constellations

      Last month we looked at some of the amazing objects in Scorpius and Sagittarius, towards the centre of the Milky Way. This month we'll move along a little from our Galaxy's bright centre to where it passes overhead through Centaurus, Crux, the Southern Cross, and the constellations of Carina, Vela and Puppis that make up the great ship Argo Navis.

      Crux - Crux, the Southern Cross lies on its side after sunset in the south western sky, with the Diamond Cross and false cross below. Above Crux are Alpha and Beta Centauri, the brightest stars in the constellation of Centaurus. Known as the pointers, they guide our eye to Gamma Crucis, the star at the top of Crux, and help us identify the true Southern Cross.

      Omega Centauri - To the right of the pointers, and just outside the main band of the Milky Way is the spectacular globular cluster Omega Centauri. This is by far the largest and brightest globular cluster in the Milky Way appearing as a fuzzy star to the naked eye. With binoculars it is an even more stunning sight, spanning almost a full degree of the sky, twice that of the full moon, whilst a small telescope will show a shimmering ball of stars, with many individual stars visible towards the outskirts.

      The Jewel Box - Close to Beta Crucis, in the Southern Cross, is a different type of star cluster. NGC 4755, also known the "Jewel Box", is an open cluster about 6,500 light years away. It is rich and bright with the stars showing an array of different colours, highlighted by an orange-red supergiant. At magnitude 4.2, the Jewel Box can easily be seen with the naked eye. It is dominated by an A-shaped asterism of bright stars, which is observable with binoculars, whilst even a small telescope will reveal a stunning sight. The name comes from Sir John Herschel's vivid description of the cluster as a "casket of variously coloured precious stones".

      The colours of these stars tell us how hot they are. The red stars are the coolest, with temperatures around 3000K, yellow stars like our Sun are closer to 6000K, whilst the hottest, bluest stars reach temperatures of 30,000 Kelvin or more. In order to get this hot these stars have to use a huge amount of fuel very quickly, so they don't live very long - they live fast and die young. The most massive live for just a few million years. The fact that NGC4755 still contains a number of these hot blue stars tells us that it is relatively young, in fact it is one of the youngest star clusters known, with an estimated age of just 14 million years.

      Coal Sack - Just to the left is a dark patch known as the Coal Sack nebula. This is a huge cloud of interstellar dust and gas some 700 light years away. It is so thick and dense that it obscures the light from more distant stars, appearing as a darkened area against the bright backdrop of the Milky Way. Aboriginal astronomers have observed the Coalsack for at least 40,000 years, whilst to Māori here in New Zealand it is known as te Patiki or the flounder.

      Carinae Cluster - Below the Coalsack, at the tip of the Diamond Cross asterism in Carina is the Theta Carinae cluster, or IC 2602, an open cluster containing around 60 individual stars. At magnitude 1.9 it is the third brightest open cluster in the sky and is often known as the Southern Pleiades, although it is still much fainter than its northern counterpart. The cluster spans around 50 arcminutes, over 1.5 full moon diameters, so it is best viewed with binoculars or a low powered telescope giving a wide field of view.

      Carinae Nebula - Around 4 degrees to the right of Theta Carinae is the famous NGC 3372, the Eta Carina nebula, a huge cloud of glowing gas estimated to be around 7500 ly away. At 4 times the size of the Orion Nebula, it is one of the largest nebulae of its type in our skies. With the naked eye you'll be able to pick out the brightest central areas, but with binoculars you should be able to see Eta Carinae itself as a golden star within the nebula. Eta Carinae is actually a system of at least two stars, which combined are around 5 million times more luminous than our Sun. The largest has around 90 times the Sun's mass and is so bright that the radiation pressure it produces is almost too strong for the gravity holding it together, causing a constant stream of material out into space.

      Highlights of the Month

      Venus - In the morning skies, Venus is now rising around 5am. The Moon will pass nearby on the 19th, sitting just above Venus in the north east at sunrise. The two will move towards the north by midmorning, providing a perfect opportunity to try and spot Venus in the daylight, with Venus sat just to the right of a thin waning crescent Moon.

      Wishing you clear skies from the team here at Space Place at Carter Observatory.

The night sky for July 2017

Wed, 05/07/2017 - 19:00
Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during July 2017.

The Planets

  • Jupiter - Now three months after opposition, Jupiter still dominates the low southwestern sky after nightfall. It sets at about 1 am BST as July begins. As the month progresses its brightness falls from -2.0 to -1.9 magnitudes as its angular size falls from 37 to 34 arc seconds. It lies in Virgo some 10.5 degrees to the west of Spica, now moving eastwards again after its period of retrograde motion. It will pass Spica on September 11th on its journey towards the lower parts of the ecliptic. Next year it will only reach an elevation of some 25 degrees when due south and, in the following two years, just 18 degrees before it moves back towards the more northerly parts of the ecliptic. Even so, with a small telescope one should easily be able to see the equatorial bands in the atmosphere, sometimes the Great Red Spot and up to four of the Galilean moons as they weave their way around it.
  • Saturn - Saturn came into opposition on June 11th and so will be at its highest elevation due south at around midnight BST as July begins but by ~10 pm BST at its end. It will be visible throughout most of the short night. It shines initially at magnitude 0.1 falling to +0.2 during the month and has an angular size of ~18 arc seconds. With an angle of 26.7 degrees inclination to the line of sight, the rings are virtually as open as they ever can be. It is sad that Saturn, now lying in the southern part of Ophiuchus between Sagittarius and Scorpius, only reaches an elevation of ~17 degrees above the horizon when due south so hindering our view of this most beautiful planet. If imaging Saturn (or Jupiter), Registax 6 has a tool to align the red, green and blue colour images to largely remove atmospheric dispersion from the image. At somewhat over 100 GBP one can purchase the ZWO atmospheric dispersion corrector which uses two, contra rotating, prisms to carry out an even better correction - and which can also be used for visual observing.
  • Mercury - Mercury reaches greatest elongation east, some 27 degrees from the Sun, on July 30th. It can be seen low in the west-northwest around 30 minutes after sunset. Binoculars may well be needed but please do not use them until after the Sun has set. It fades slightly during the month from -1.0 to +0.4 magnitudes whilst its angular size increases from 5.3 to 7.8 arc seconds. No surface details will, of course, be seen.
  • Mars - Mars is hidden in the Sun's glare all month so cannot be observed.
  • Venus - Venus is visible in the east before dawn this month rising around 2.5 hours before sunrise increasing to 3 hours as the month progresses. It magnitude dims slightly during the month from -4.2 to -4.0 as its angular diameter shrinks from 18.2 to 14.6 arc seconds. However, at the same time, its illuminated phase increases from 63 to 74% which explains why the magnitude does not drop too much. Even though it will be moving back towards the Sun, as the angle of the ecliptic to the horizon increases at this time of the year, it elevation before sunrise will continue to increase until August. Venus passes the Pleiades Cluster on the 5th, the Hyades on the 13/14th and ends the month close to M35 in Gemini.
  • Highlights

    June - The best month to observe Saturn - Saturn reached opposition on the 14th of June, so is now due south and highest in the sky in the late evening. It lies in the southern part of Ophiuchus some 16 degrees up and to the left of the orange star Antares in Scorpius. Held steady, binoculars should enable you to see Saturn's brightest moon, Titan, at magnitude 8.2. A small telescope will show the rings with magnifications of x25 or more and one of 6-8 inches aperture with a magnification of ~x200 coupled with a night of good 'seeing' (when the atmosphere is calm) will show Saturn and its beautiful ring system in its full glory.Due to the orientation of Saturn's rotation axis of 27 degrees with respect to the plane of the solar system, the orientation of the rings as seen by us changes as it orbits the Sun and twice each orbit they lie edge on to us and so can hardly be seen. This last happened in 2009 and they are now fully opened out, currently at an angle of 26.5 degrees to the line of sight. From this month the ring's orientation will begin to narrow until March 2025 when they will appear edge-on again.

    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 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. The 15 minute exposure image on right was taken by the author using a 127 mm APO refractor and SBIG 8.3 megapixel CCD camera. 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!

    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 7th/8th - midnight: The Moon and SaturnLate evening on the 7th July, the waxing Moon will be seen to the upper right of Saturn.

    20th July - before dawn: Venus, Aldebaran and a thin crescent Moon - Before dawn on the 20th, Venus will be seen over to the left of a very thin waning crescent Moon. Aldebaran, lying in front of the Hyades Cluster, will also be seen to the upper right of the Moon.

    July 25th - after sunset: The Moon and Mercury - After sunset on the 25th July, given a low western horizon and clear skies, there is a chance of spotting Mercury down to the right of a very thin crescent Moon. Binoculars may well be needed but please do not use them until after the Sun has set.

    July 1st and 15th: The Alpine Valley - These are two good nights to observe an interesting feature on the Moon if you have a small telescope. Close to the terminator is the Appenine mountain chain that marks the edge of Mare Imbrium. Towards the upper end you should see the cleft across them called the Alpine valley. It is about 7 miles wide and 79 miles long. As shown in the image a thin rill runs along its length which is quite a challenge to observe. Over the next two nights the dark crater Plato and the young crater Copernicus will come into view. This is a very interesting region of the Moon!

    Claire Bretherton from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during July 2017.

    Kia ora and welcome to the July Jodcast from Space Place at Carter Observatory in Wellington, New Zealand.
    Jupiter is still high in our evening skies this month, midway up the northwestern sky after sunset. Shining at magnitude -2.1, with its bright golden glow, Jupiter will be the first star-like object you'll see as the sky begins to darken. Just above is bluish Spica, representing the "ear of wheat" held by Virgo. The waxing crescent moon will pass close to Jupiter on both the 1st and 29th of the month.
    Lower in the west, Mercury is making an appearance in the evening sky. At the start of the month it sets just an hour after the Sun, but by the end of July, when it reaches its greatest elongation from the Sun, it will remain in our skies until 8pm. On the 25th Mercury will form a close group with Regulus, in Leo, and a thin crescent Moon.
    Saturn is high in the northeast and is a great target for a telescope of any size, with its rings still at almost maximum tilt. Look out for Saturn's largest moon Titan looking like a star at around 4 times the ring diameter from the planet. Saturn continues to sit just below Antares in Scorpius, with the claws of the scorpion to the left and his tail curling around to the right. In New Zealand we see this as the fish hook of Māui, Te Matau a Maui.
    Below Scorpius is an upside down teapot formed from the brightest stars in the constellation of Sagittarius. The bright centre of the Milky Way runs through Scorpius and sagitarrius, so there are many stunning objects to explore in this part of the sky.
    Lying along the tail of the scorpion, close to the orange 3rd magnitude star Zeta Scorpii, is NGC 6231, a bright cluster of stars which looks like a small comet. At magnitude 2.6 this is easily visible to the naked eye. Estimated to be only 3.2 million years old and nearly 6000 light-years away, NGC6231 covers an area of the sky similar in size to the Pleiades, but its stars are much more luminous. If the cluster was placed at the same distance as the Pleiades then some of its stars would be amongst the brightest in the night time sky. With a good pair of binoculars, from a dark sight, NGC 6231 appears in an area of nebulosity and intermingled with open clusters Trumpler 24 and Collinder 316 to form a lovely complex sometimes known as the Scorpius Lizard. Also nearby is NGC 2642. With binoculars its three brightest stars stand out from a faint background glow.
    A little above, NGC 6193 is also visible to the naked eye at magnitude 5.2, and nearby NGC 6167 is worth a look in binoculars or a small telescope.
    Below, about halfway between the scorpion's sting and the spout of the teapot is M7. This is another open cluster of stars easily visible to the naked eye at magnitude 3.3, and a lovely sight through a good pair of binoculars. It contains about 80 stars brighter than 10th magnitude and covers an area of 1.3 degrees diameter. Current estimates suggest a distance of 980 light years and an age of 220 million years old – still pretty young in astronomical terms. M7 has been known since ancient times and was first recorded by Ptolomy in 130 AD, who described it as a "nebula following the sting of Scorpius", because of this it is also sometimes referred to as the Ptolomy cluster. Nearby and somewhat fainter, the Butterfly cluster, or M6 is also a nice sight in binoculars. The stars will all appear to be at around the same brightness, and the open winged shape that gives the cluster its name should be easy to pick out.
    To the left of the teapot's spout, and just about visible to the naked eye, is another lovely Messier object, the Lagoon Nebula, or M8. This is a huge cloud of interstellar gas and dust where new stars are being formed. M8 is a great example of an HII region, where the UV radiation from hot young stars is ionizing the leftover hydrogen gas and causing is to glow. These emission nebulae often appear pink in colour photographs and the Lagoon Nebula is a good target for binoculars or a small telescope.
    Another good target is the Trifid nebula, discovered by Charles Messier in 1764, and famed for the three-lobed appearance, which earned it it’s name. It is an interesting object to observe as it combines both an emission and reflection nebula along with an open cluster of stars.
    There are also a number of globular clusters in this part of the sky. The brightest is M4, and this is also one of the easiest to find, lying just 1.3 degrees west of Antares. Appearing as a small fuzzy ball in binoculars or small telescopes, a slightly larger telescope will begin to pick out individual stars.
    Also in this region, near the top of the teapot, is M22, one of the first globular clusters ever discovered in 1665, and one of the closest at just 10,600 light-years.
    From its bright centre the Milky Way stretches overhead through Crux, the Southern Cross, and on to Carina, Vela and Puppis above the southwestern horizon. Together these three constellations make up the great ship Argo Navis, famous in Greek mythology as that used by Jason and the Argonauts in their quest for the Golden Fleece.
    Just to the left of the Milky Way is Carina’s brightest star Canopus, or Alpha Carinae, the second brightest in the nighttime sky. Its Maori name is Atu tahi or Au tahi, which means to stand alone, because of its position just outside the main band of our Galaxy. In the other direction , the Milky Way drops down to the eastern horizon and the bright star Altair in the constellation of Aquila, the Eagle, which rises around 9pm at the start of the month.
    In the morning skies our last visible planet, brilliant Venus, rises after 4am. Venus is so bright that you can really only mistake it with the headlights of an airplane and provides a useful pointer to help find Matariki/the Pleiades as the cluster rises before dawn. Venus sits just above Matariki at the beginning of the month, but slowly moves down between Matariki and Taurus' brightest star Aldebaran as the month progresses, sitting just below Aldebaran on the morning of the 18th.
    Wishing you clear skies from the team her at Space Place at Carter Observatory.

The night sky for June 2017

Sat, 10/06/2017 - 20:00
Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during June 2017.

The Planets
  • Jupiter - Now two months after opposition, Jupiter still dominates the late evening sky shining in the south to southwest after nightfall. It sets about 3 am BST as June begins and by about 1 am at its end. As the month progresses its brightness falls from -2.3 to -2 .0 magnitudes as its angular size falls from 41 to 37 arc seconds. It lies in Virgo some 11 degrees to the west of Spica, Alpha Virginis, and halts its westwards retrograde motion on the 11th as it begins its initially slow eastwards march back towards Spica. It will pass Spica on September 11th on its journey towards the lower parts of the ecliptic. Next year it will only reach an elevation of some 25 degrees when due south and, in the following two years, just 18 degrees before it moves back towards the more northerly parts of the ecliptic. Even so, with a small telescope one should easily be able to see the equatorial bands in the atmosphere, sometimes the Great Red Spot and up to four of the Gallilean moons as they weave their way around it.
  • Saturn - Saturn comes into opposition on June 11th and so, then, will be at its highest elevation due south at around 1 am BST and will be visible throughout the short night. It shines at magnitude 0.1 all month and has an angular size of 18.3 arc seconds. With an angle of 26.5 degrees inclination to the line of sight the rings are virtually as open as they ever can be. It is sad that Saturn, now lying in the southern part of Ophiuchus between Sagittarius and Scorpius, only reaches an elevation of ~17 degrees above the horizon when due south so hindering our view of this most beautiful planet. If imaging Saturn (or Jupiter), Registax 6 has a tool to align the red, green and blue colour images to largely remove atmospheric dispersion from the image. At somewhat over £100 one can purchase the ZWO atmospheric dispersion corrector which uses two, contra rotating, prisms to carry out an even better correction.
  • Mercury - Mercury is lost in the glare of the Sun for most of the month before it makes a modest evening apparition in July. It might just be spotted with binoculars very low in the west after sunset at the very end of the month. But please do not use them until after the Sun has set.
  • Mars - Following a two year long apparition, Mars finally slips into the Sun's glare in the first week of June when its salmon-pink disk might just be picked out in the west-northwest.
  • Venus - Venus is visible in the east before dawn this month reaching its greatest elongation (46 degrees west of the Sun) on the 3rd of June. It magnitude dims slightly during the month from -4.5 to -4.2 as its angular diameter shrinks from ~24 to 18 arc seconds. However, at the same time, its phase increases from 48 to 62 percent which explains why the magnitude does not drop too much. Even though it will be moving back towards the Sun, as the angle of the ecliptic to the horizon increases at this time of the year, it elevation before sunrise will continue to increase until August.
  • Highlights

    Early June - still worth viewing 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 - The best month to observe Saturn. .The thing that makes Saturn stand out is, of course, its ring system. The two outermost rings, A and B, are separated by a gap called Cassini's Division which should be visible in a telescope of 4 or more inches aperture if seeing conditions are good. Lying within the B ring, but far less bright and difficult to spot, is the C or Crepe Ring. Due to the orientation of Saturn's rotation axis of 27 degrees with respect to the plane of the solar system, the orientation of the rings as seen by us changes as it orbits the Sun and twice each orbit they lie edge on to us and so can hardly be seen. This last happened in 2009 and they are now opening out, currently at an angle of 26.5 degrees to the line of sight. From this month the ring's orientation will begin to narrow until March 2025 when they will appear edge-on again.

    June - Find the globular cluster in Hercules and spot the 'Double-double' in Lyra.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!

    Late June: 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!

    June 3rd - evening: The Moon and Jupiter.During the evening of the 3rd June, the waxing Moon will lie less than 2 degrees up and to the right of Jupiter.

    8th/9th June - around midnight: Observe the Galilean Satellites. .If clear around midnight the 8th/9th, and using a small telescope, one could observe the 4 Gallilean Moons lined up on one side of the giant planet.

    Night of June 15 to 16th when fully dark: The Lyrid Meteor Shower.The June Lyrid meteor shower reaches its peak on the night of the 15th/16th with a rate at the zenith of ~8 meteors per hour. This is not many and, as the Moon is close to third quarter it may be hard to spot one. The radiant is very close to the star Vega. Many more meteors were seen from the shower in the late 1960's but the peak hourly rate has dropped off markedly since then. If clear, it may still be worth aiming to see if you can spot one.

    21st June - before dawn: Venus and a thin crescent Moon.Before dawn on the 22st, Venus will be seen some 4 degrees above a very thin waning crescent Moon.

    Late June - around midnight: Observe Comet 2015 V2 (Johnson) .On the 12 June but, sadly, close to Full Moon, Comet Johnson is at perihelion lying at a distance of 1.64 AU from the Sun. On the 1st of June it will lie over to the left of Arcturus in Bootes but passes into Virgo on the 14th. In the latter part of the month with no moonlight to hinder our view, binoculars or a small telescope could be used to spot Comet Johnson as it move across Virgo. It is expected to reach magnitude +6 so should be easily visible with binoculars. The chart shows its position during the month.

    June 3rd and 16th: The Alpine Valley.These are two good nights to observe an interesting feature on the Moon if you have a small telescope. Close to the terminator is the Appenine mountain chain that marks the edge of Mare Imbrium. Towards the upper end you should see the cleft across them called the Alpine valley. It is about 7 miles wide and 79 miles long. As shown in the image a thin rill runs along its length which is quite a challenge to observe. Over the next two nights the dark crater Plato and the young crater Copernicus will come into view. This is a very interesting region of the Moon!

    Southern Hemisphere

    Claire Bretherton tells us what we can see in the southern hemisphere night sky during June 2017.

    The Planets
    • Introduction

      Kia ora and welcome to the June Jodcast from Space Place at Carter Observatory in Wellington, New Zealand.

      This month, we reach our winter solstice here in the southern hemisphere, when the south pole of the Earth is at its greatest tilt away from the Sun. This means that the Sun appears much lower in the sky, our days are shorter and colder, and our nights are longer.

      This year the solstice falls on the 21st June NZST. Whilst always around this time, the actual date of the winter solstice can sometimes fall on the 22nd. This is because it takes the Earth approximately 365 and a quarter days to go around the Sun, but we don't count that extra quarter day in our calendars every year, we save them up for a leap year. So the timing of the solstice slips around 6 hours later each year until we add an extra day and it jumps back to the beginning again.

      The word solstice means "Sun stopped" or "Sun still", because the Sun rises and sets at it most northerly points of the year. As we move back towards the summer, the Sun will gradually rise and set further and further south until it stops again at the summer solstice in December, and begins the long journey back north.

    • HighlightsStars

      Whilst the cold weather at this time of year may not be so welcome, the long, dark nights provide a perfect opportunity to observe our beautiful southern skies.

      We are very lucky here in the southern hemisphere, that we have a perfect view towards the central bulge of our Milky Way galaxy, so it appears broader and brighter across our sky. The center lies towards the constellations of Sagittarius, the archer, and Scorpius, the Scorpion, which is now midway up our eastern evening skies. Scorpius is our winter constellation, and together with Sagittarius, a little below, will be dominating our skies over the next few months.

      At the heart of the Scorpion is the bright orange tinged star Antares, a red supergiant with a radius nearly 900 times that of the Sun. The name Antares means "rival of Mars" because of its distinctive colour, which tells us that it is a cooler star, at around 3 and a half thousand degrees. Antares lies around 550ly away and is amongst the 20 brightest stars in the nighttime sky.

      To the left of Antares is a line of stars now forming the Scorpion's claws, and further left still the faint zodiac constellation of Libra, the scales. Libra's two brightest stars form an almost vertical line in our evening sky, and have perhaps the best names of any I have seen, Zubenelgenubi and Zubeneschamali.

      Zubenelgenubi, the higher of the two, is half way between Antares and Spica at a distance of around 77 light years. At magnitude 2.7 it enjoys the alpha designation, despite being slightly fainter than its beta counterpart below, probably because it lies just a third of a degree from the ecliptic.

      Using binoculars you'll see that Zubenelgenubi is in fact a double star with two components separated by around 5400 AU (a little under 4' on the sky), and which appear to be co-moving through space. Strictly speaking, the name Zubenelgenubi now only refers to the brighter of the two. Both components are spectroscopic binary stars in their own right, and there may be also be a fifth component to the system, KU Librae, located 2.6 degrees away.

      Below Alpha Librae is the slightly brighter Beta Librae, or Zubeneschamali, at magnitude 2.6, which lies 185 lightyears away. Zubeneschamali is a hot blue main sequence star some 130 times more luminous than the Sun, and with twice the surface temperature. Whilst stars of this type are often seen as white or bluish in colour, Zubeneschamali has often been described as greenish by observers, the only green star visible to the naked eye. Whilst theoretically this is not possible, scientists are still unsure why so many observers claim to see it this way.

      Constellations

      Whilst today these stars are part of Libra, the names Zubenelgenubi and Zubeneschamali derive from the Arabic for the southern claw and northern claw of the scorpion, referring back to the ancient Greeks who saw these stars as part of the constellation of Scorpius.

      The idea of scales or a balance can be traced back to the ancient Babylonians though, some 4,000 years ago, at a time when the northern hemisphere autumnal equinox (where the Sun crosses the equator from the northern to southern hemisphere) appeared in that part of the sky. The choice of scales likely relates to the balance between light and dark, with equal hours of day and night experienced at the equinox, as well as the change of seasons from summer to winter, and therefore hot to cold.

      The romans revived the idea, seeing Libra as the Scales of Justice held by Astraea, the Starry Goddess, represented by the neighboring zodiac constellation of Virgo. Virgo is currently home to bright Jupiter, sat a little to the left of the constellations brightest star Spica, high in the northeast after dark.

      Below Scorpius is our second evening planet, cream-coloured Saturn, shining at magnitude 0 this month. Saturn reaches opposition on the 15th, when it will be directly opposite the Sun in the sky and overhead at midnight. Saturn will also be at its closest to Earth around this time making it appear at its largest and brightest, although in practice any difference will be hard to spot with the naked eye. Do take a look through a small telescope if you get a chance though. This opposition its rings will be almost at maximum tilt, so should be a wonderful sight.

      Here in New Zealand, we don't have Scorpions, so we see Scorpius as something a little more familiar in the Southern Pacific. To Maori this group of stars is known as Te Matau a Maui, the fishhook of Maui, which he used to pull a great fish out of the ocean that became the north island of New Zealand, te Ika a Maui. Antares is known as Rehua, and represents a drop of blood that Maui took from his nose to use as bait.

      This constellation was an important aid for ancient pacific navigators as it travels directly overhead from our latitude. Once te Matau a Maui was right overhead it was simply a case of travelling east or west to find Aotearoa/New Zealand.

      By just before sunrise Scorpius or Te Matau a Maui has moved to the west south western horizon, with the hook pointing upwards.

      The morning skies at this time of year are particularly important here in New Zealand as this is the time we celebrate Matariki, or Maori New Year. The timing of this celebration is based on the heliacal rising of the small group of stars known as Matariki or the Pleiades.

      Opposite Scorpius in the morning sky is his arch enemy, Orion the hunter, rising directly east, with the three bright stars of his belt lying along the horizon. These are also known as Tautoru here in New Zealand.

      If you follow these stars along the horizon to the right they point to Sirius or Takurua, the brightest star in the night time sky. Follow them to the left and you first come to a v shape forming the head of Taurus the bull, with the bright star Aldebaran marking his eye, and then to Matariki rising in the east north east.

      The Pleiades is, in fact, visible throughout most of the year, but is only known as Matariki around this time. It disappears from our evening skies around April each year before reappearing in the morning in early June. It is this reappearance, or heliacal rising, that tells us that the old year is coming to an end. The next new moon (or for some iwi the next full moon) marks the beginning of the New Year. This year the new moon falls on the 24th of June, and may be visible a day or two after this, so Matariki will officially be celebrated on the 25th of the month.

      Maori mythology

      In Maori mythology Matariki, Tautoru, Takurua and Rehua form four pou, or pillars that hold Ranginui, the sky father, in the sky. Matariki supported one of Rangi's shoulders and marks the rising point of the Sun at the winter solstice. Takurua (Sirius) supports the other shoulder and is the closest bright star to the Sun's rising point at the summer solstice. These two stars represent the extent of the Sun's movement throughout the year.

      Tautoru held Rangi's neck and marks the celestial equator which runs along the length of Ranginui's backbone. Poutu-te-rangi or the star Altair, marks the other end. Over in the west Rehua, or Antares, supports Ranginui's lower torso. A line drawn from Matariki to Rehua marks the ecliptic; the pathway of the Sun, Moon and planets through the sky.

      These four pou form the basis of a celestial compass, a map of the night sky that was used to navigate the Pacific Ocean and bring our ancestors to Aotearoa. Today Matariki is a chance for all New Zealanders to unite in celebration of this great land we all call home: its a chance to reflect on the state of the planet we live on and the bounty that we receive from Mother Earth, to celebrate our shared history and to reflect on our very unique place in the Universe.

      Nga mihi o Te Tau Hou ki a koutou katoa

      Wishing you all a very Happy New Year from the team here at Space Place.

The night sky for May 2017

Sun, 14/05/2017 - 19:00
Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during May 2017.

The Stars and GalaxiesThe Planets
  • Jupiter
    came into opposition on April 7th so, this month, transits in the late evening and is visible rising in the east at dusk. It is moving in retrograde motion lying in Virgo initially some 9 degrees over to the right of its brightest star, Spica. This increases to ~11 degrees as May progresses. The size of Jupiter's disk decreases slightly from 43.5. to 40.8 arc seconds during May with its magnitude reducing very slightly from -2.4 to -2.3. With a small telescope one should be easily able to see the equatorial bands in the atmosphere, sometimes the Great Red Spot and up to four of the Galilean moons as they weave their way around it.
  • Saturn
    rises around 11:30pm BST as may begins and will be highest in the pre-dawn sky at ~4am BST. By the end of May it will rise at ~9:30pm BST and transit at around 2am BST. Lying in the western part of Sagittarius, its diameter increases from 17.8 to 18.3 arc seconds during the month as it brightness increases slightly from magnitude +0.3 to +0.1. It will be high enough in the south-east in the hours before dawn to make out the beautiful ring system which, at over 26 degrees to the line of sight, are nearly as open as they ever become. If only it were higher in the ecliptic; its elevation this year never gets above ~18 degrees and so the atmosphere will hinder our view of this most beautiful planet. [Note: I have acquired a ZWO Atmospheric Dispersion Corrector which uses two contra-rotating prisms to combat the dispersion of the atmosphere at low elevations. If imaging Saturn (or Jupiter), Registax 6 has a tool to align the red, green and blue colour images to largely remove the dispersion from the image.]
  • Mercury
    is lost in the glare of the Sun this month so cannot be observed.
  • Mars
    lies in Taurus initially making a shallow triangle with Aldabaran to its lower left and the Pleiades cluster to its lower right. In early May, Mars has an elevation of ~11 degrees above the western horizon at sunset, but this reduces to ~5 degrees by month's end when Mars will be lost in the Sun's glare. It will then be lost from view all summer as it passes behind the Sun. By month's end it will lie some 6.5 degrees over to the left of Alnath, Beta Tauri. Its brightness falls slightly during the month from magnitude +1.6 to +1.7 whilst its angular diameter falls from 3.9 to 3.7 arc seconds. No details would be expected to be seen on its salmon-pink surface.
  • Venus
    rises in the east in the morning twilight on the first of the month and then climbs a little higher each morning as May progresses. On May 1st, the disk, forming a crescent 38 arc seconds high, is just 27% lit shining with a magnitude of -4.7 - its maximum brightness. By the end of the month, Venus shines at magnitude -4.5 with its angular size reduced to 25 arc seconds and its illuminated fraction increased to 48%. It is then close to its greatest elongation from the Sun of 46 degrees which it will reach on June 3rd. But, due to the shallow angle that the ecliptic makes to the horizon at this time of the year, it will then only have an elevation of ~16 degrees at sunrise.
Highlights

JupiterThis is a great month to observe Jupiter which came into opposition on April 7th so, during May, will be visible in the south during the evening. It is moving down the ecliptic and lies in Virgo. It now reaches an elevation of ~36 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?

May: Look for the Great Red Spot on JupiterA list gives some of the best evening times during May to observe the Great Red Spot which should then lie on the central meridian of the planet. The times are in UT.

May 4/5th - after midnight: The Moon occults the double star 49 LeonisJust after 00:20 BST, the dark limb of the Moon will occult the double star 49 Leonis (magnitudes +5.8 and +7.9 separated by 2 arc seconds). As a result, the starlight will take longer to be extinguished than from a single star. If the seeing were good, it might be possible to split the pair using a high magnification and see each component disappear.

May 5th and 6th before dawn: The Eta Aquarid Meteor ShowerThe Eta Aquarids are one of the finest meteor showers that can be seen from the southern hemisphere, but, in the northern hemisphere, may be glimpsed in the pre-dawn sky in the south-east around 90 minutes before dawn. Sadly, this year the peak is when the Moon is coming towards full - but happily low on the western horizon - so there will be some moonlight to hinder our view.

May 7th - evening: The Moon and JupiterThis evening the Moon, three days before full, will pass just 1.5 degrees above Jupiter.

15th May - evening: Observe the Galilean Satellites.If clear on the evening of the 15th and using a small telescope, one could observe the 4 Galilean Moons lined up on one side of the giant planet.

22nd May - dawn: Venus and a thin crescent MoonBefore dawn on the 22nd, Venus will be seen over to the left of a very thin waning crescent Moon.

22nd to 31st May - all night: Observe Comet 2015 V2 (Johnson)During the last 10 days of May, with no Moonlight to hinder our view, binoculars or a small telescope could be used to spot Comet Johnson as it moves down through the constellation Bootes closing in on the bright star Arcturus. It might reach magnitude +6 so should be easily visible with binoculars. The chart shows its position during this time.

27th May - ~23:20 BST: a shadow transit of Jupiter.After sunset on the last three day of the month, one can observe, if clear, a thin waxing crescent Moon passing the Beehive cluster (M44) as it moves up to pass Regulus, in Leo, on the 31st.

May 3rd and 16th, evening: The Hyginus RilleThese 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.

Southern Hemisphere

Claire Bretherton from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during May 2017.

Kia ora and welcome to the May Jodcast from Space Place at Carter Observatory in Wellington, New Zealand.

Our evening skies this month are dominated by Jupiter and Saturn, along with some of our brightest stars. Jupiter will be one of the first objects to appear, visible in the north east shortly after the Sun has set. A bright waxing gibbous moon will pass within 2 degrees of the planet on the evening of May 8th, that’s 4 moon diameters apart. Both will be visible within the same binocular field of view.Just to the right of Jupiter is Spica, the brightest star in the constellation of Virgo, and below, just above the horizon is orange coloured Arcturus, which at magnitude −0.05 is the brightest star in the northern celestial hemisphere and the 4th brightest in the night sky.

Arcturus has a similar mass to the Sun, but it is further along in its lifespan and has already expanded to become a red giant, with 25 times the diameter and 170 times the luminosity of our own star. When close to the horizon it often appears to twinkle red and green as its light is broken up by our atmosphere.

All three of the brighter stars are in the southern hemisphere, and are also visible in our evening skies this month. The brightest, Sirius , sits halfway up the western sky at the beginning of the month, with Orion’s belt, now almost vertical, below. Rigel and Betelguese , the seventh and ninth brightest stars sit to either side of the belt. Both Orion and Sirius will soon be disappearing from our evening skies, before reappearing before the Sun in the morning skies over the coming months.

The second brightest star Canopus is circumpolar here in New Zealand, never dropping below the horizon. This month it sits a little higher than Sirius, further around towards the south west. To complete the trio, the third brightest star, Alpha Centauri is high in the southeast, pointing the way to the Southern Cross.

Below Alpha Centauri, rising in the twilight sky is the curve of stars making the body of Scorpius, the scorpion. Its brightest star Antares is a variable star, which ranges in brightness from magnitude 0.6 to 1.6, and is on average the 15th brightest in the night sky. Antares is a red supergiant, , one of the largest stars known, almost 900 times the diameter of the Sun. If it were placed at the centre of the Solar System, its surface would extend to the middle of the asteroid belt. The name Antares means rival of Mars, because of its striking red colour. To Māori the star is known as Rehua and represents a drop of blood Maui pulled from his nose to bait his fishhook. In Aotearoa, the constellation of Scorpius in seen as Maui’s hook, te Matau a Maui, which was used to pull up a great fish which became the north island of New Zealand.

Scorpius/te Matau a Maui is our winter constellation and will be dominating our skies over the coming months, visible throughout the night.

Sitting just 1.3 degrees to the west of Antares, and visible in the same wide field telescope view, is the 5.9 magnitude globular cluster Messier 4, just about visible to the naked eye in a clear, dark sky. M4 is one of the nearest globular clusters in the sky, at just 7,200 lightyears away and is the only globular cluster that Messier was able to resolve with the modest equipment he was using, 20 years before William Herschel was able to resolve all of the Messier globular clusters with his much larger telescopes.

M4 is one of the loosest, most open globular clusters and features a central bar of 11th magnitude stars, which can be resolved in a 10cm telescope. Through binoculars the cluster is seen as a round hazy patch.

Messier 4 contains some of the oldest stars known in our galaxy, with an estimated age of 13 billion years. Discovered by the Hubble Space Telescope in 1995, these White Dwarf stars are the remnants of ancient solar like stars that have already shed their outer layers into space.

In 2003 a planet was discovered orbiting one of these White Dwarfs and its Pulsar companion, the first circumbinary (ie orbiting both stars)”planet ever found, and the first planet detected in a globular cluster. With a mass of around 2.5 Jupiters and an estimated age of 12.7 billion years, it is also one of the oldest known extrasolar planets, earning it the unofficial nicknames “Methuselah” and “The Genesis Planet”.

A little over half way from Antares to Arcturus is another globular cluster, M5, or NGC 5904, in the constellation of Serpens. At almost 6th magnitude it is also tough to spot with the naked eye in anything but the darkest conditions, but with binoculars it is easy to find, although you will need a small telescope to begin to resolve it and start to pick out a slightly elongated shape and a few edge stars.

With a calculated age of around 13 billion years, M5 is one of the oldest globular clusters known, and at 165 light years in diameter and containing hundreds of thousands of stars, it is also one of the largest. It also contains 105 known variable stars, with the brightest and most easily observed, Variable 42, changing from magnitude 10.6 to 12.1 in just under 26.5 days.

To find M5 you can star hop from the faint star 109 Virginis to 110 Virginis and then around twice the distance again to find 5 Serpentis, and M5 is just 20' to the North West.

Below Antares, and rising a little later in the evening, is bright, cream coloured Saturn. It’s a great time to observe Saturn through a small telescope at the moment with its rings at close to maximum tilt. Saturns largest moon , Titan, can be spotted orbiting around for ring diameters from the planet, with several smaller, closer moons also visible in larger telescopes.

In the morning sky Venus rises in the east around 4am and is joined by Mercury around an hour and a half before sunrise. Mercury reaches its greatest elongation west on the 18th of May and is making its best morning appearance of the year, rising before twilight begins throughout the month.

If you’re out planet spotting in the early hours then take a look for the eta aquarids meteor shower, which peaks around the 6th of May. This shower is caused by the Earth passing through the trail of debris left behind by the famous comet Halley. The shower appears to radiate from a point near the fourth magnitude star Eta Aquarii, one of the brightest in the zodiac constellation of Aquarius, representing the water bearer.

The radiant won’t rise in the eastern sky until around 2am here in New Zealand, so the best time to go meteor spotting is in the few hours before sunrise. At the shower’s peak you may be able to spot up to a meteor a minute, many of them fast and bright and leaving glowing trails behind them. Viewing conditions this year will be much better than last, with the Moon setting on the other side of the sky in the early hours of the morning, giving you a good few hours of observing time before the Sun rises just after 7 am.

You may also have a chance for some binocular comet hunting this month as Comet PanSTARRS (C/2015 ER61) heads towards Perihelion (its closest approach to the Sun) on the 10th of May. At the start of the month it will be moving from Aquarius through to Pisces and may be visible with binoculars in our morning skies. On 4th April the comet experienced an outburst, brightening from 8th to 6th magnitude almost overnight, and whilst it is always hard to predict how bright a comet is going to get, this one is definitely worth keeping an eye on.Wishing you clear skies from the team here at Space Place at Carter Observatory.