The Night Sky This Month

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Ian Morison tells you what can be seen in the night sky this month.
Updated: 1 day 11 min ago

The night sky for November 2017

Tue, 07/11/2017 - 11:00
Northern Hemisphere

Ian Morison tells us what we can see in the Northern Hemisphere night sky during November 2017.

The Planets

  • Jupiter

    Jupiter passed behind the Sun on October 26th and so will become visible again in the pre-dawn sky after the first week or so November. It will then lie down to the lower left of Venus. However, by the end of November it will rise some two hours before the Sun allowing its 31 arcsecond disk, shining at a magnitude of -1.7, to be observed under clear skies. The low elevation will, of course, hinder our view.

  • Saturn

    Saturn can be seen low in the southwest during twilight this month dropping down towards the horizon a little more each week. Shining at magnitude +0.5, it sets around 2 hours after the Sun on the 1st but little more than one hour by month end. It starts the month moving slowly eastwards in Ophiuchus but reaches the boundary of Sagittarius on the 18th. Last month, Saturn's rings reached their maximum tilt to the line of sight of 27 degrees and it is a real pity that Saturn is so low in the sky. Sadly, this will not improve for quite a few years as Saturn moves slowly through the lowest part of the ecliptic. Towards the end of the month Saturn edges closer to Mercury, but with both so low above the horizon after sunset, will be difficult to spot.

  • Mercury

    Mercury passed between us and the Sun (Superior conjunction) on October 8th and will become visible again after sunset in the latter part of the month. From around the 17th, it might be glimpsed with binoculars low in the southwest 20 minutes after sunset shining at magnitude -0.4. It reaches greatest elongation, 22 degrees east of the Sun on November 23rd but, due to the shallow angle of the ecliptic to the horizon, never lies far above the horizon. In the last few days of the month its magnitude falls to -0.2 and it only lies ~5 degrees above the horizon 30 minutes after sunset.

  • Mars

    Mars, lying in Virgo, has now become a morning object at the start of its new apparition and rises three to four hours earlier than the Sun. During the month, Mars has a magnitude of 1.7 and an angular size of just 3.9 (increasing to 4.2) arc seconds so no details will be seen on its salmon-pink surface. On the 4th, Mars is just three degrees to the upper right of Porrima, Gamma Virginis. This closes to two degrees by the 6th whilst, at the end of the month, it will lie just 3 degrees to the upper left of Spica, Alpha Virginis.

  • Venus

    Venus, now moving back towards the Sun, rises some 90 minutes before dawn at the start of the month but this falls to 45 minutes by month's end. Its magnitude remains at -3.9 during the month as its angular diameter shrinks from 10.4 to 10 arc seconds. However, at the same time, its illuminated phase increases from 96% to 99% - which explains why its magnitude does not change. At the beginning of the month, it lies close to Spica, Alpha Virginis, with Venus some 100 times (5 magnitudes) brighter than Spica. By month's end, binoculars might be needed to spot it low above the eastern horizon. But please do not use them after the Sun has risen.

    HIGHLIGHTS
  • November - a good month to observe Neptune and Uranus with a small telescope.

    Neptune came into opposition - when it is nearest the Earth - on the 2nd of September, so will be well placed to spot this month. 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 charts. 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. Uranus reached opposition on October 19th and so is visible all night. It will be highest in the sky in the south around 1 am BST shining at magnitude 5.7 and with a disk 3.7 arc seconds across. It lies in Pisces, one degree and 18 arc minutes up to the right of Omicron Pisces as shown in the accompanying chart. Its turquoise green colour should be seen in a small telescope and it will be easily spotted in binoculars.

  • Around the 18th of November (with no Moon in the sky): find M31 - The Andromeda Galaxy - and perhaps M33 in Triangulum

    In the evening, the galaxy M31 in Andromeda is visible in the south. The chart provides two ways of finding it:

    1. Find the square of Pegasus. Start at the top left star of the square - Alpha Andromedae - and move two stars to the left and up a bit. Then turn 90 degrees to the right, move up to one reasonably bright star and continue a similar distance in the same direction. You should easily spot M31 with binoculars and, if there is a dark sky, you can even see it with your unaided eye. The photons that are falling on your retina left Andromeda well over two million years ago!
    2. You can also find M31 by following the "arrow" made by the three rightmost bright stars of Cassiopeia down to the lower right as shown on the chart.

    Around new Moon (18th November) - and away from towns and cities - you may also be able to spot M33, the third largest galaxy after M31 and our own galaxy in our Local Group of galaxies. It is a face on spiral and its surface brightness is pretty low so a dark, transparent sky will be needed to spot it using binoculars (8x40 or, preferably, 10x50). Follow the two stars back from M31 and continue in the same direction sweeping slowly as you go. It looks like a piece of tissue paper stuck on the sky just a bit brighter than the sky background. Good Hunting.

  • November early mornings: November Meteors.

    In the hours before dawn, November gives us a chance to observe meteors from two showers. The first that it is thought might produce some bright events is the Northern Taurids shower which has a broad peak of around 10 days but normally gives relatively few meteors per hour. The peak is around the 10th of November but then the Moon is close to third quarter so its light will intrude. The meteors arise from comet 2P/Encke. Its tail is especially rich in large particles and, this year, we may pass through a relatively rich band so it is possible that a number of fireballs might be observed!

    The better known November shower is the Leonids which peak on the night of the 17th/18th of the month. Happily, the Moon is new so will not hinder our view. As one might expect, the shower's radiant lies within the sickle of Leo and meteors could be spotted from the 15th to the 20th of the month. The Leonids enter the atmosphere at ~71 km/sec and this makes them somewhat challenging to photograph but it is worth trying as one might just capture a bright fireball. Up to 15 meteors an hour could be observed if near the zenith. The Leonids are famous because every 33 years a meteor storm might be observed when the parent comet, 55P/Temple-Tuttle passes close to the Sun. In 1999, 3,000 meteors were observed per hour but we are now halfway between these impressive events hence with a far lower expected rate.

  • November late night: Comet 2107 O1 (ASASSN).

    Throughout November, with binoculars or a small telescope, it should be possible to spot Comet 2107 O1 (ASASSN) as it nears the Pole Star. It was discovered in July by the 'All Sky Automated Survey for Supernovae' and brightened rapidly. Its brightness is now falling but, at magnitude +8 or +9, should be visible near the Pole Star this month.

  • November 6th - very early morning: The Moon occults Aldebaran and the Hyades Cluster

    In the early hours of the 6th November, a near full Moon, passing across the Hyades Cluster (at a distance of 153 light years) will occult the red giant star Aldebaran which lies at a distance of 65 light years in front of the Hyades Cluster.

  • November 15th - 1 hour before dawn: Mars and a crescent Moon

    In the hour or so before dawn, Mars will be seen to the right of a thin Crescent Moon.

  • November 16th - before dawn: three planets and a crescent Moon

    Just before dawn, Mars, a very thin Crescent Moon, Jupiter and Venus will form a lineup along the ecliptic. In the dawn glare, binoculars and a very low eastern horizon will be needed to spot them all but please do not use the binoculars after the Sun has risen.

    Claire Bretherton from the Carter Observatory in New Zealand speaks about the Southern Hemisphere night sky during November 2017.

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

    The Planets

      Mercury now joins Saturn in our western evening skies. Unfortunately it won't be as easy to spot as its last evening appearance in July-August, as it sets before twilight ends. At the start of the month orange Antares, the brightest star in Scorpius or Te Matau a Maui, will sit between the two planets, but as the stars and Saturn slowly sink closer to the horizon from night to night Mercury climbs higher, sitting level with Antares on the 14th and with Saturn on the 24th, when it also reaches its greatest elongation east.

    Constellations

      Scorpius/Te Matau a Maui has been dominating our evening skies over the winter months, but is now disappearing from view, ready to reappear in the morning over the coming months. As Scorpius sets in the west, his arch enemy, and our summer constellation, Orion rises towards the east along with Taurus and Canis Major. Antares, which marks the heart of the Scorpion, is also known as Rehua to Maori. It represents one of the four Pou, or pillars, that hold Ranginui, the sky father up in the sky. It sits just above the south western horizon at around 11pm at the beginning of the month. These four pou form the basis of a celestial compass, a map of the night sky that was used to navigate the vast pacific oceans and bring our Polynesian ancestors to Aotearoa/New Zealand.

      The other three pou are marked by Matariki (the Pleiades), Tautoru (the belt of Orion) and Takurua (Sirius), which line up along the eastern horizon. Matariki supports 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. In between, rising directly east, is Tautoru, or the belt of Orion, marking the rising point of the Sun at the time of the equinox.

      Stretching from Scorpius around to Orion is Te Waka o Tamareriti, or Tamarereti's canoe, which lines up along the southern horizon in our evening sky. The front of the canoe is marked by the tail of Scorpius, with the sting representing the beautifully carved wood that adorns the prow. The star at the end of the Scorpion's curving tail marks the place where the bow meets the water, whilst Rehua or Antares, marks the crest of a wave as the great waka glides through the waters of the Milky Way.

      The Southern cross marks the anchor, Te Punga and the pointers Alpha and Beta Centauri are the anchor line, Te Taura.

      Orion marks the stern of the canoe, with the elaborately carved stern post rising all the way up from red Betelgeuse to bluish Rigel. A tall mast rises from the waka all the way to Achernar, high in the south, the brightest star in the southern constellation of Eridanus, the river, which we explored last month. A little below Achernar, the two small fuzzy patches of light that make up the Large and Small Magellanic Clouds mark the waka\92s sails.

    • Mythology

      One story tells of Tamarereti sailing across the sky in his waka with all the stars in kete or baskets. He places the key seasonal and navigational stars in their correct positions in the sky, but he finds he has lots of smaller stars left over. So he capsizes his waka spilling all the smaller stars into the sky forming Te Ika Roa, or the Milky Way. Another story tells of Tamareriti scattering bright pebbles in the dark, lightless sky to help guide his way home. The pebbles became the stars and the wake of his waka formed the Milky Way. The sky we see in the mid-evening in October/November each year is, in fact, the same sky we see just before sunrise around June, the time we celebrate Matariki, or Maori New Year. It is said that the bright star Canopus, or Atutahi (the ariki or high chief of the heavens), pulls up the anchor at the start of the year starting the waka in motion. During the year you can track the progress of Tamarereti's waka as it moves across the sky, one day at a time.

    • Pegasus

      On the opposite side of the sky is the Great Square of Pegasus, the flying horse, leaping over the northern horizon. Last month we talked a little about this wonderful constellation, its brightest star Enif, marking the horse's muzzle, and the beautiful globular cluster, M15. But we can also use Pegasus to help us find some of our nearest galactic neighbours.

    • Alpheratz and M31

      The star at the bottom right of the Great Square of Pegasus is in fact Alpha Andromodae, or Alpheratz, the brightest star in the constellation of Andromeda. Located some 97 light years from Earth it is a spectroscopic binary star whose two components orbit each other in just 100 days. M31 is approaching the Milky Way at 110 km/s and is expected to collide and merge with our own Galaxy in around 4 billion years.

    • M33

      A little higher and towards the east, the Triangulum galaxy or M33 is better placed in our skies. At around 3 million light years from Earth and shining at magnitude 5.7 it is just at the limit of naked eye visibility under excellent conditions, making it one of the most distant objects able to be glimpsed unaided. To find M33, head back from Andromeda towards Mirach and then continue a similar distance to the other side. Whilst spotting it with the naked eye is a real challenge, it is easily observable in a pair of binoculars. With the mass of 10s of billions of Suns, M33 is also approaching us, at around 100,000 kilometres per hour. The most striking feature of the Triangulum Galaxy is a massive region of star formation, known as NGC604, which can be seen with a small telescope. NGC604 is 100 times larger than the Orion Nebula and contains over 200 hot, massive blue stars formed just 3 million years ago. In fact, if it were at the same distance as the Orion Nebula, it would be second brightest to only the Moon in the night time sky.

    • Leonids Meteor Shower

      Look out for the Leonid meteor shower, which peaks around the 17th -18thof the month, when the Earth passes through the trail of dust and debris left behind by the comet Temple-Tuttle. Whilst normally a reliable but fairly quiet meteor shower, observers have noticed that roughly every 33 years the number of meteors observed during the shower shows a marked increase as the Earth passes through the denser parts of the cometary debris trail. The radiant of the shower, from which the meteors appear to originate, is located in the constellation of Leo, which rises only a couple of hours before the Sun in our morning sky. The best time to observe the Leonids is about 2-3 hours before sunrise on the mornings around the peak. Look around 20 degrees away from the radiant point for the best chance of meteor spotting.

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

The night sky for October 2017

Thu, 05/10/2017 - 03:10
Northern Hemisphere

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

The Planets

  • Jupiter

    Jupiter might just be visible for the first few days of October very low above the west-southwestern horizon after sunset. It passes behind the Sun on October 26th to become visible again in the pre-dawn sky in mid November.

  • Saturn

    Saturn can be seen low in the southwest during twilight this month dropping down towards the horizon a little more each week. Shining at magnitude +0.5, it sets around 3 hours after the Sun on the 1st but nearer 2 hours by month end. It is moving slowly eastwards in Ophiuchus moving closer to the boundary of Sagittarius which it will reach on the 18th of November. This month, Saturn's rings reach their maximum tilt to the line of sight of 27 degrees and it is a real pity that Saturn is so low in the sky. Sadly, this will not improve for quite a few years as Saturn moves slowly through the lowest part of the ecliptic.

  • Mercury

    Mercury passes between us and the Sun (Superior conjunction) on October 8th so will not be visible this month.

  • Mars

    Mars has now become a morning object at the start of its new apparition. Initially lying in Leo, it moves into Virgo on the 12th of the month and is still not easily seen in the pre-dawn sky. During the month, Mars has a magnitude of 1.8 and an angular size of just 3.7 (increasing to 3.9) arc seconds so no details will be seen on its salmon-pink surface. As the month progresses Mars rises higher in the sky before dawn and, as described in the highlights, flirts with Venus at the beginning of the month.

  • Venus

    Venus, now moving back towards the Sun, is visible in the east before dawn this month, rising around 2 hours before sunrise at the start of the month and close to Mars. Its magnitude remains at -3.9 during the month as its angular diameter shrinks from 11.2 to 10.6 arc seconds. However, at the same time, its illuminated phase increases from 91% to 96% - which explains why its magnitude does not change. By month's end, Venus rises just an hour and a half before the Sun and binoculars might be needed to spot it low above the eastern horizon. But please do not use them after the Sun has risen.

    HIGHLIGHTS
  • October - a good month to observe Neptune and Uranus with a small telescope.

    Neptune came into opposition - when it is nearest the Earth - on the 2nd of September, so will be well placed to spot this month. 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 charts. 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. Uranus reaches opposition (when it is nearest the Earth) on October 19th and so is visible all night. It will be highest in the sky in the south around 1 am BST shining at magnitude 5.7 and with a disk 3.7 arc seconds across. It lies in Pisces, one degree and 18 arc minutes up to the right of Omicron Pisces as shown in the accompanying chart. Its turquoise green colour should be seen in a small telescope and it will be easily spotted in binoculars.

  • October 5th - before dawn: Venus and Mars close in the East.

    Before dawn on the 5th, Venus and Mars will lie just a quarter of a degree apart in the eastern sky.

  • October 1st- 14th - evening: Saturn in the Southwest

    After dark in the evenings of the first part of the month we will have our last good views of Saturn this apparition. Its rings are at their widest, inclined at 27 degrees to the line of sight.

  • October 9th - late evening: The Moon and the Hyades Cluster

    Late evening on the 9th, rising in the East will be the Hyades Cluster along with a waning Moon.

  • October 17th - before dawn: Venus and Mars below a thin crescent Moon.

    Looking Eastwards before dawn on the 17th, a thin crescent Moon will be seen high above Venus and Mars.

  • October 24th - after sunset: Saturn below a thin waxing crescent Moon

    After sunset on the 24th, Saturn will be seen lying below a thin waxing crescent Moon.

  • October 11th: Mons Piton and Cassini

    Best seen just before Third Quarter, Mons Piton is an isolated lunar mountain located in the eastern part of Mare Imbrium, south-east of the crater Plato and west of the crater Cassini. It has a diameter of 25 km and a height of 2.3 km. Its height was determined by the length of the shadow it casts. Cassini is a 57km crater that has been flooded with lava. The crater floor has then been impacted many times and holds within its borders two significant craters, Cassini A, the larger and Cassini B.

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

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

    The Planets

      We're really noticing the lighter mornings and evenings now as the Earth continues its orbit around the Sun and we move closer to our southern hemisphere summer. By the end of October the Sun won't set until around 8pm here in Wellington. As we leave Jupiter behind on its outer orbit it is slowly disappearing from our skies, it still sits low in the west at the beginning of the month, setting as twilight ends, but by mid month will be lost in the sunset.

    • Saturn

      Saturn is now our best bet for evening planet viewing, sitting midway up the western sky after dark. A little below and to the left of the planet is Antares or Rehua, marking the heart of Scorpius, which we call te Matau a Maui, the fish hook of Maui here in New Zealand.

    • Zodiacal Light

      October is a good time to look out for the zodiacal light, a triangular glow visible in the west after sunset in a clear, dark sky, tilting up towards Antares. The zodiacal light is caused by sunlight reflecting off dust along the plane of our solar system. This plane is marked by the ecliptic, the apparent path of the Sun across the sky, which runs through the constellations of the zodiac. At this time of year the ecliptic makes a steep angle with the horizon, making the zodiacal light easier to observe.

    • Neptune and Uranus

      Whilst not easily seen with the naked eye, Neptune and Uranus are also in our evenings skies, with Neptune in the constellation of Aquarius and Uranus is in neighbouring Pisces. Uranus reaches opposition on the 20th of the month, when it will be directly opposite the Sun in the sky and overhead at around 1am now that we are observing daylight saving. At magnitude 5.7 it is just on the edge of naked eye visibility, but with binoculars should be easy to spot. A small telescope may reveal it as a disk, with a greenish hue.

    Constellations

      Just to the north of Pisces is the constellation of Pegasus, the winged horse, which appears to leap across the northern horizon in our late evening sky. Pegasus is easy to spot by the ''Great Square'' of stars that makes up his body.The brightest star in the constellation is the reddish star Epsilon Pegasi, marking the horse's muzzle. This star is commonly known as Enif, deriving from the Arabic word for nose. Epsilon Pegasi is an orange supergiant, around 12 times the mass of the Sun, and with a radius some 185 times larger.

      Nearby, to the bottom left of Enif, (and visible in the same binocular field of view) is the globular cluster M15, one of the oldest and best know star clusters in the sky, with an estimated age of around 12 billion years. The cluster is located around 34,000 light years away and measures 175 light years across. M15 is probably the most densely packed globular cluster in our galaxy, with half of its mass concentrated within 10 light years of the centre. It has been suggested that this massive concentration of stars may be caused by a rare type of supermassive Black Hole in the clusters core.M15 also contains the planetary nebula Pease 1, the first to be found within a globular cluster. At magnitude 15.5, this is a faint object, and a telescope with an aperture of at least 300mm would be needed to observe it.

      On the opposite side of the sky, the Southern Cross, or Te Punga sits low in the south south west, its long arm pointing up across the sky to Achernar in the south east. Achernar is at the tip of the constellation of Eridanus, the river, and is also known as Alpha Eridani. It is the brightest star in the constellation, and the 9th brightest in the night sky. It is a hot, blue main sequence star around 7 times the mass and over 3000 times the luminosity of the Sun. The traditional name, Achernar, derives from the Arabic phrase ''Al Ahir al Nahr'' meaning the end of the river, although interestingly this name was once given to Theta Eridani, now known as Acamar, which was the brightest star in the constellation visible from Ancient Greece.Achernar spins on its axis extremely quickly, completing one rotation in just over 2 days. This high rotation speed gives the star a flattened shape, with the diameter of its equator over 50% greater than that of its poles. Infrared observations from the Very Large Telescope in Chile have also identified a smaller companion star, with around twice the mass of the Sun. The two are extremely close, with a separation of just over 12 AU, slightly larger than the distance from the Sun to Saturn, and orbit once every 14-15 years, although the highly distorted shape of the primary makes these numbers hard to determine.

      Below Achernar, just above the south south east horizon, our second brightest night time star, Canopus, twinkles colourfully. The two make an almost equilateral triangle with the southern celestial pole, the point in the sky directly above the south pole of the Earth, about which the whole sky appears to rotate. Another easy way to find this is to but one hand an Achernar and a second hand on Gamma Crucis at the top of the Southern Cross and clap them together in the middle.

    • Magellanic Clouds

      Between the southern celestial pole and Achernar, and above Canopus, you may be able to spot two small fuzzy patches of light, easily seen with the naked eye on a dark, moonless night. These are the Large and Small Magellanic Clouds, two small irregular dwarf galaxies that neighbour our own. Whilst these galaxies are much smaller than the Milky Way, they still contain billions of stars. To the top-right of the SMC you may spot a faint fuzzy 'star'. This object is not actually associated with the SMC but is a beautiful globular cluster called 47 Tucanae, or NGC 104 located just a tenth of the distance away on the outskirts of our own galaxy. At around magnitude 4.1 it is the second brightest globular cluster in the sky, after Omega Centauri, and can be easily seen with the naked eye. With a binoculars or a small telescope it is a wonderful sight, revealing a densely packed central core, whilst a larger telescope will start to resolve some of its millions of ancient stars.

    • Orion

      At the far end of the long winding river of Eridanus is our summer constellation of Orion, the hunter, with bright, blue Rigel the first star to rise after around 11pm mid-month. Below, and following around and hour and a half later is stunning red Betelgeuse, marking the hunter's shoulder or armpit. We'll be exploring this part of the heavens in much more detail over the next few months as it moves into our evening skies, but this month we turn our attention to the constellation in the morning skies, the best time to see the Orionid meteor shower, the radiant of which lies a little below and to the right of Betelgeuse. The Orionids peak on the 21st-22nd of October when the Earth passes through the trail of dust and debris left behind by Comet Halley. The shower can reach rates of 25 meteors per hour, but from the latitude of New Zealand around 10 per hour is more likely with the radiant below the horizon until the early hours of the morning. The best time to look is in the hours before dawn. Try looking around 20 degrees away from the radiant, so the areas from Taurus around through the top of Orion to Canis Major are probably your best bet. Whilst the meteors may be few and far between they also tend to travel quite long distances on the sky and sometimes leave persistent trails of ionized gas behind them that can last for several seconds. With a new moon on the 20th, just before the peak, leaving us with nice dark skies, you should have a good chance of Orionid spotting this year.

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

The night sky for September 2017

Fri, 15/09/2017 - 14:30
The Night Sky

Northern Hemisphere

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

The Planets
  • Jupiter: Now five months after opposition, Jupiter can still just be seen very low in the southwestern sky after nightfall, lying at an elevation of some 10 degrees 45 minutes after sunset. By month's end it will be at an elevation of just 4 degrees at dusk. With a magnitude of -1.7 and an angular size of ~31 arc seconds it will be at its dimmest and smallest during this year's apparition and is too low for any reasonable telescopic views. At the start of September, Spica, Alpha Virginis, lies some 4 degrees to its lower left. Jupiter, moving eastwards passes 3 degrees to the upper right of Spica on September 11th. Now moving down towards the lower part of the ecliptic, next year it will only have an elevation of 25 degrees when due south whilst for the following two years an elevation of just 18 degrees.

  • Saturn came into opposition back on June 11th and so will be seen in the southwest as darkness falls and sets late evening. It shines initially at magnitude +0.4 falling to +0.5 during the month and has an angular size of ~16.5 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. It is sad that Saturn, now lying in the southern part of Ophiuchus between Sagittarius and Scorpius, only reached 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. has now become a morning object and will form a very tight grouping with Mars and Regulus, in Leo on the morning of the 5th. They will lie about 15 degrees below Venus. Binoculars will be needed to observe them in the bright twilight but please do not use them after the Sun has risen. Rising in elevation during the first part of the month, by the 10th it will have brightened to zero magnitude and lie just half a degree to lower right of Regulus. Mercury reaches greatest elongation, some 18 degrees from the Sun on the 12th - its best morning apparition this year. On the 14th, it lies 11 degrees to the lower left of Venus whilst, before dawn on the 16th, it closes to just 0.3 degrees from Mars. In the final week of September, moving back towards the Sun, it will be lost in the Sun's glare. .

  • Mars has now become a morning object at the start of its new apparition. Lying in Leo, and still not easily seen in the pre-dawn sky, it forms a tight grouping with Mercury and Regulus on the 5th some 15 degrees to the lower left of Venus. During the month, Mars has a magnitude of 1.8 and an angular size of just 3.6 arc seconds so no details will be seen on its salmon-pink surface. As the month progresses Mars rises higher in the sky before dawn and moves closer to Venus which is now moving back towards the Sun

  • Venus is visible in the east before dawn this month, rising around 2 hours before sunrise. Its magnitude remains at -3.9 during the month as its angular diameter shrinks from 12.4 to 11.2 arc seconds. However, at the same time, its illuminated phase increases from 84 percent to 91 percent - which explains why its magnitude does not change.

  • Highlights of the Month

    September - 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!

    September - 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 to spot this month. 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 charts. 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.

    September 5th - before dawn: Mars Mercury and Regulus. Before dawn on the 5th, Mercury and Mars will be seen in a close grouping with Regulus in Leo. A very low eastern horizon will be needed to spot them with the use of Binoculars - but please do not use them after the Sun has risen. [The magnification given by the binoculars reduces the effective brightness of the pre-dawn light.]

    September 12th - before dawn: the Moon closes on the Hyades Cluster. Before dawn on the 12th, the Moon will be seen closing onto the Hyades Cluster in Taurus.

    September 16th - before dawn: three planets below the Moon. Before dawn on the 16th, a thin crescent Moon will be seen high above Venus, Mars and Mercury. Regulus lies between Venus and Mercury.

    September 26th - after sunset: Saturn below the crescent Moon. After sunset on the 26th, Saturn will be seen lying below the Moon.

    September: 12th and 28th: the Alpine Valley. These are good nights to observe an interesting feature on the Moon if you have a small telescope. Close to the limb 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 following the 28th 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 September 2017.

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

    The Planets
    • Saturn: After what felt like a long, cold, wet winter here in Wellington, September marks the start of spring in the southern hemisphere. As we head towards the equinox on the 23rd of the month we see a rapid change in our daylight hours, with our days getting longer and our nights shorter. Equinox means "equal night" because we have the same number of hours of daylight and the same number of hours of darkness at this time of year. By the end of September the Sun won't be setting until nearly half past 7.The mission has revealed the complexity of Saturn's ring system, identified numerous new moons, and provided some of the most stunning images of the solar system that we have ever seen. It has found liquid oceans and a thick atmosphere on Titan, with conditions that may be similar to early Earth, and exploration of the icy moon Enceladus has revealed a hot spot at the southern pole, icy jets spewing out from the surface and a vast ocean below the ice.

    • Neptune: Whilst there are only two evening planets you can see with your own eyes, Neptune is also in our evening skies, with Uranus joining it before 10pm. Both can be picked out with binoculars, and you may even notice a greenish colour to Uranus, but Neptune will be indistinguishable from a faint star.Now is the best time to look for the eighth planet though, as it reaches opposition on the fifth of the month, when it will be directly opposite the Sun in the sky and at its highest in the north at midnight. At around this time the planet will also be at its closest and brightest, shining at magnitude 7.8, and is sat less than a degree just below and to the right of the 3.8 magnitude star lambda aquarii, but you'll still probably need a detailed finder chart to spot it. Unfortunately, the full moon passes close to Neptune just after opposition, so it may be easier to find a week or two later.

    • Stars

      The bright stars Vega and Canopus mark north-south around dusk this month, guiding our eye to the bright band of the Milky Way passing high overhead. Along with the nearby bright stars of Deneb, in Cygnus the swan, and Altair, in Aquila the eagle, Vega forms part of the "winter triangle" as seen here in the southern hemisphere.

      To the south-east of Capricornus is the faint constellation of Piscis Austrinus, the southern fish, with its only bright star, Fomalhaut, marking the mouth of the fish. Fomalhaut is the 18th brightest star in the night sky, and the only, lonely bright star in its vicinity.Follow up observations, however, failed to confirm the planet and left many doubting its existence. It took until 2012 before Fomalhaut b was independently detected and confirmed. Its controversial past has earned it the nickname "the zombie planet", a planet resurrected from the dead.

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

The night sky for August 2017

Fri, 11/08/2017 - 13:00
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.