The Night Sky This Month

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Ian Morison tells you what can be seen in the night sky this month.
Updated: 2 hours 42 min ago

The night sky for March 2017

Wed, 01/03/2017 - 10:00
Northern Hemisphere

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

Highlights of the Month

1st-4th March - after sunset: Three planets and (on the 1st) a very thin crescent Moon. On these nights, Venus is 12 degrees down to the lower right of Mars, both in the southwest, and between them lies Uranus. On the 1st of March, they will be joined by a very thin waxing crescent Moon.

March 4th, following 10pm: The Full Moon occults Gamma Tauri in the Hyades cluster. During the late evening, the first quarter Moon will occult the star Gamma Tauri, which forms the peak of the triangular shaped Hyades Cluster. In North America, the Moon can be seen occulting Aldebaran.

10th March - all evening: The Moon, two days before full, passes just below Regulus in Leo.

March 15th - before dawn: The Moon lies close to Jupiter and Spica. Before dawn, Jupiter appears between the Moon to its upper left and Spica, Alpha Virginis, down to its lower left.

March 20th - before dawn: Saturn near the third quarter Moon. Before dawn on the 20th and looking South, Saturn will be seen over to the right of the third quarter Moon.

March 6th and 19th: The Alpine Valley. These are two good nights to observe an interesting feature on the Moon with a small telescope. Close to the limb is the Appenine mountain chain that marks the edge of Mare Imbrium. Towards the upper end is a cleft called the Alpine Valley. The dark crater Plato will also be visible nearby.

The Planets
  • Jupiter, moving towards opposition on April 7th, lies in Virgo initially some 4 degrees above its brightest star, Spica. With a small telescope, it should be easy to see the equatorial bands in the atmosphere, sometimes the Great Red Spot, and up to four of the Gallilean moons.

  • Saturn rises well after midnight and will be highest in the pre-dawn sky. It will be high enough to make out the beautiful ring system which, at over 26 degrees to the line of sight, are as open as they ever become. Its elevation this year never gets above 18 degrees, so the atmosphere will hinder our view of this planet.

  • Mercury passes through superior conjunction on March 7th and becomes visible around the 15th in bright twilight just above the western horizon. On the 19th, on its way up, it passes Venus, on its way down, some 9 degrees to its right.

  • At the beginning of March, Mars can be found in Pisces up and to the left of Venus. As the month progresses, Mars continues to move eastwards (moving into Aries on the 8th) whilst Venus falls back towards the western horizon.

  • Venus starts the month dominating the western sky, shining virtually at its brightest with a magnitude -4.8. It lies due south in mid-afternoon and can even by seen with the unaided eye. After dark in a very dark location, it can even form shadows. On the 1st of February, it has its highest elevation at sunset during the month at ~30 degrees. But then, as the month progresses, it falls back towards the Sun and passes in front of it on the 25th. Very unusually, Venus is far enough north of the Sun that it will start rising before dawn on March 15th, some 10 days before inferior conjunction. Thus it could be seen both at nightfall and at dawn for a few days.


Southern Hemisphere

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

As we approach the autumn equinox on the 20th of March, our evenings are quickly drawing in, we have more time to get outside observing our beautiful Southern skies. The Milky Way, or te Ika Roa arches high across the sky from north-northwest to south-southeast after dark.

Canopus, the second brightest star in our night time sky, is just to the southwest of overhead. Canopus is circumpolar from our position here and is considered to be a tapu, or sacred to Maori. Around halfway from Canopus to the southwest horizon is Achernar, a blue main sequence star around 7 times more massive than the Sun but over 3000 times more luminous. Achernar is part of a binary system, with a fainter, less massive A type companion. Achernar and Canopus form a roughly equilateral triangle with the Southern Celestial Pole. Unlike the northern hemisphere, we have no nearby bright star to mark this point, so we have to estimate it from the surrounding stars.

Not far from the southern celestial pole towards Achernar, 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, combined they still contain billions of stars. The best time to look out for these galaxies is around the new moon on the 28th of the month, when they will be high in the south after dark.

Alpha and Beta Centauri are the first and second brightest stars in the constellation of Centaurus. The constellation, which is currently the 9th largest in the sky, once incorporated the constellations of Lupus and Crux. The globular cluster Omega Centauri, sits just to the east of the bright band of our Galaxy. This is by far the largest and brightest globular cluster in the Milky Way. The cluster is relatively easy to find even with the naked eye, appearing as a fuzzy star around 13 degrees northeast of Gamma Crucis at the top of the Southern Cross. With a small telescope the cluster becomes a glowing, shimmering ball of stars.

Further east and low on the horizon after dark is the constellation of Virgo, with its brightest star Spica rising just as twilight ends at the start of the month. Spica is actually a particular type of binary system called a rotating ellipsoidal variable, where its two components orbit so close together that they become egg-shaped rather than spherical. Virgo is also home to the Virgo Cluster of galaxies, containing perhaps as many as 2000 members. Just below and to the left of Spica this month is bright, golden Jupiter. With a decent pair of binoculars, you should be able to pick out Jupiter's four largest moons. The nearly full moon will pass close by on the 14th and 15th of the month.

The night sky for February 2017

Sat, 11/02/2017 - 09:00
Northern Hemisphere

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

The Planets
  • Jupiter lies in Virgo some 3 and a half degrees above its brightest star, Spica. At the start of February it rises in the east at ~00:30 but by month's end by ~22:45. It will be due south at an elevation of 34 degrees at ~06:00 at the start and at ~04:00 by the end of February. The size of Jupiter's disk increases slightly from 39 to 42 arc seconds as February progresses with its magnitude increasing very slightly from -2.1 to -2.3. On February 6th, Jupiter halts its eastwards movement across the heavens and begins to move westwards in retrograde motion for several months. 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 is now a morning object, rising in the south-east at ~08:00 UT as the month begin but by about 06:30 UT at its end. Lying in the southern part of Ophiuchus, its diameter increases from 15.6 to 16.1 arc seconds during the month as it shines at magnitude +0.5. Towards the end of the month it will be high enough in the south-east before dawn to make out the beautiful ring system which, at over 26 degrees to the line of sight, are as open as they ever become. If only it were higher in the ecliptic; its elevation this year will never gets above ~18 degrees in elevation and so the atmosphere will hinder our view of this most beautiful planet. [Note: I have just acquired a ZWO Atmospheric Dispersion Corrector which uses two contra-rotating prisms to combat the dispersion of the atmosphere at low elevations.]
  • Mercury lies low in the southeast just before dawn down to the lower left of Saturn. It brightens from -0.2 to -1.2 during the month. It will be best seen around mid-month but no details would be expected to be seen on its disk which spans around 5 arc seconds across.
  • Mars is easy to find this month lying in Pisces up and to the left of Venus. They are closest on February 1st with a separation of 5.4 degrees. By month's end, as Mars continues to move eastwards and Venus begins to fall back towards the western horizon, their separation increases to just over 12 degrees. Its brightness falls slightly from magnitude +1.1 to +1.3 whilst its angular diameter falls from 5.1 to 4.6 arc seconds. No details would be expected to be seen on its salmon-pink surface.
  • Venus is dominating the western sky this month shining virtually at its brightest with a magnitude -4.8. Its close proximity to a crescent Moon last month was given a lot of attention! It lies due south in mid-afternoon and can even by seen with the unaided eye. After dark in a very dark location it can even form shadows! On the 4th of February it reaches its highest elevation of 33 degrees at sunset. Its angular size increases from 31 to 46 arc seconds during the month but at the same time the phase reduces from 40 percent to 18 percent illuminated. These two effects compensate each other which is why the brightness stays so constant. In visible light no details are seen on its brilliant white surface but cloud details can be seen or imaged in the ultra-violet. In daytime when still high in the sky it can be imaged in the infrared as the blue light from the sky is filtered out. This month's astronomy digest article on imaging the Moon and planets in the infrared shows how Venus looked on the 5th of January 2017.
  • 31st January to 5th February - after sunset: Venus approaches within 6 degrees of Mars If clear on the evenings of the 31st of January to the 5th of February and looking southwest one could not fail to spot Venus. But, on these nights Venus comes to within 5 degrees 23 arc seconds of Mars lying up to its left. On the 31st of January and the 1st of February, they will be joined by a thin waxing crescent Moon.
  • 5th February - all evening: The first quarter Moon occults stars within the Hyades Cluster. If clear on the evening of the 5th and looking first to the south-southeast, one will see the first quarter Moon passing in front of the Hyades cluster in Taurus. At around 18:42 its dark limb will occult the pair of stars Theta 1 and Theta 2 Tauri and at ~20:32, the magnitude 2.73 star 85 Tauri. Then at 23:27 it will lie very close to magnitude -0.7 star Aldebaran - a red giant star that lies between us and the cluster.
  • February 11th - just before dawn: The Full Moon below Regulus in Leo Just before dawn and, given clear skies and a very low horizon towards the west, you should easily see the Full Moon lying below the magnitude 1.35 star, Regulus, Alpha Leonis.
  • February 15th - before dawn: The Moon lies close to Jupiter If clear before dawn on the 15th and looking southwest, one will see Jupiter lying between the Moon to its upper right and Spica, Alpha Virginis, down to its lower left.
  • February 21st: Saturn near a waning crescent Moon Before dawn on the 21st and looking south-southeast, Saturn will be seen down to the lower right of a thin waning crescent Moon.
  • February 26th - after sunset: Uranus close to Mars with both up to the left of Venus This is an excellent chance to find Uranus - perhaps for the first time - shining at magnitude 5.9 just to the lower left of Mars at magnitude 1.3. They will be just 35 arc minutes apart so Uranus will be easily spotted with Binoculars. The turquoise disk with an angular size of just over 3 arc seconds may just be seen as such using a small telescope.
Southern Hemisphere

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

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

This month we'll start to see some changes in our evening skies. Bright Venus, which has been dominating in the west for some months, is now beginning its journey back towards the Sun. Whilst still visible in the dusk skies, it will be setting as twilight ends, around an hour and a half after the Sun, at the beginning of the February, but by the end of the month it will be dropping below the horizon just 30 minutes after sunset. Fainter red Mars is a little above, holding its position well as it moves through the constellation of Pisces. At the end of the month, Mars will pass within 34 arcminutes of faint Uranus, with both visible in the same binocular field of view, and well worth a look, particularly as this also coincides with the new moon on the 27th, although by the time it gets fully dark from our location the pair will right on the horizon.

On the opposite side of the sky, golden Jupiter is now moving into our evening skies, rising just before midnight at the start of the month and by around 10pm, as twilight ends, at the end.

Orion is now high in the north after dark, with Sirius, or Takurua, the brightest star in our night-time sky, even higher.

Below and to the right, and forming a triangle with Sirius and Betelgeuse, is Procyon, the brighter of the two main stars that form the constellation of Canis Minor, Orion's small hunting dog. Procyon is the eighth brightest star in the night-time sky and, like Sirius (at ~9 ly distant), is one of our Sun's nearest neighbours at just 11 light years away. Also like Sirius, it is in fact a binary system, with a 1.5 solar mass primary and a faint white dwarf companion.

Just over a third of the way between Sirius and Procyon, in the constellation of Monoceros, is M50, a pretty, heart-shaped open cluster of stars, visible in binoculars.

Around a third of the way from Betelgeuse to Procyon is NGC2244, a rectangular cluster of stars that is embedded in a faint nebula called the Rosette. Whilst the cluster is visible in binoculars and small telescopes, the nebula is more of a challenge and is best seen photographically.

Below Canis Minor sit another pair of stars, Castor and Pollux, marking the heads of Gemini, the twins. Pollux, the higher and brighter of the two stars, is the 17th brightest star in our night sky. It is about 35 light years away from us, whilst Castor is in fact a sextuple star system located 52 light years from Earth.

Nearby to Eta Geminorum, at the foot of the twin of Castor, is the open star cluster M35, covering an area almost the size of the full moon. Under good conditions it can be seen with the unaided eye as a hazy star, but binoculars or a wide-field telescope will reveal more detail and are the best way to view this lovely cluster.

Next to Gemini is the faint zodiac constellation of Cancer, the crab. At the centre of Cancer is a lovely open cluster of stars known as M44, Praesepe (the Manger) or the Beehive. At magnitude 3.7, the cluster is visible to the naked eye as a hazy nebula, and has been know since ancient times. It was one of the first objects Galileo studied when he turned his telescope to the skies in 1609.

Galileo was able to pick out around 40 stars, but today we know that Praesepe contains over 1000 individual members, with a combined mass of between 500 and 600 times that of the Sun. As one of the closest open star clusters to our Solar System, M44 is a great target for binoculars or small telescopes, which will easily reveal a number of individual stars within it.

Higher, and to the east of Canis Major is Puppis, representing the Poop deck of the great ship Argo, which we explored last month. Inside Puppis are two lesser known Messier Objects, M46 and M47.

Messier 46 (also known as M 46 or NGC 2437) is a rich open cluster at a distance of about 5,500 light-years away. M46 is estimated to contain around 500 stars, of which around 150 of magnitude 10-13. Estimated to be only 300 million years old, this is a young cluster, and a lovely sight in binoculars or a small telescope. Astronomer John Herschel described it in his General Catalogue of Nebulae and Clusters of Stars as 'Remarkable, cluster, very bright, very rich, very large, involving a planetary nebula'. This planetary nebula, located near the cluster's northern edge, is NGC 2438.

A planetary nebula is formed when a low or intermediate mass star comes to the end of its life, ejecting its outer layers into space as a glowing shell of ionized gas.

Whilst NGC 2438 appears to lie within the cluster, it is probably just a chance line of sight effect as the vadial velocities are quite different. NCG 2438 is estimated to lie somewhat closer than M46 at around 2900 ly away.

Located around 1 degree west is another open cluster, M47. The two fit easily within one binocular field of view, and are often referred to as sisters.

Messier 47 or NGC 2422 has actually been discovered several times. The first was some time before 1654 by Giovanni Batista Hodierna and then independently by Charles Messier on February 19, 1771. William Herschel also independently rediscovered it on February 4, 1785, and it was included as GC 1594 in John Herschel's General Catalogue of Nebulae and Clusters of Stars (the precursor to Dreyer's New General Catalogue) in 1864.

Due to a sign error by Messier, the cluster was considered a 'lost Messier Object' for many years, as no cluster could be found at the position of Messiers original coordinates. It wasn't until 1959 that Canadian astronomer T. F. Morris identified that the cluster was in fact NGC2422, and realized Messier's mistake.

M47 lies at a distance of around 1,600 light-years from Earth with an estimated age of about 78 million years. M47 is described as a course, bright cluster containing around 50 stars, scattered over an area around the same size as the full moon in the sky. It is bright enough to be glimpsed with the naked eye under good observing conditions, but best viewed with binoculars or a small telescope.

There are a couple of other excellent binocular targets in Puppis, including open cluster NGC2477 - a wonderful, rich cluster of over 300 stars, described by American Astronomer Robert Burnham as 'probably the finest of the galactic clusters in Puppis' along with its neighbor NGC 2451, both located close to the second magnitude star Zeta Puppis.

Also known as Naos, this blue supergiant is one of the hottest, most luminous stars visible to the naked eye. It has a bolometric (total) luminosity of at least 500,000 times that of the Sun, but with most of its radiation emitted in the ultraviolet it is visually around 10,000 times brighter. It is also one of the closest stars of its kind to our Sun, at a distance of around 1,080 ly.

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

The night sky for December 2016

Fri, 02/12/2016 - 11:00
Northern Hemisphere

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

  • Venus below a thin crescent Moon

    After sunset on December 3rd, looking low towards the south-southwest, Venus shining at magnitude -4.2, will be seen, if clear, below a very thin crescent Moon.

  • December 4th after sunset: Venus, Mars and a crescent Moon

    If clear after sunset on the 4th, looking low towards the south-southwest it should be possible to see a thin crescent Moon to the upper left of Mars with Venus well down to its right.

  • December 13 before dawn: The Moon Occults Aldebaran in the Hyades Cluster

    During the night of the 12th/13th December, the Full Moon will pass throught the Hyades Cluster and occult many of its stars. At around 6:15 UT on the 13th, it will occult -0.7 magnitude Aldabaran which lies between us and the cluster. This may be a grazing occultation from parts of the UK.

  • December 14th and 15th after midnight: the Geminid Meteor Shower

    The early mornings of December 14th and 15th will give us the chance, if clear, of observing the peak of the Geminid meteor shower. Sadly, this is not a good a year as these nights are just after the Full Moon and the fainter meteors will not be seen. However, as I saw last year, the Geminids can often produce near-fireballs and so the shower is still well worth observing. An observing location well away from towns or cities will pay dividends. The relatively slow moving meteors arise from debris released from the asteroid 3200 Phaethon. This is unusual, as most meteor showers come from comets. The radiant - where the meteors appear to come from - is close to the bright star Castor in the constellation Gemini as shown on the chart. If it is clear it will be cold - so wrap up well, wear a woolly hat and have some hot drinks with you.

  • December 22nd/23rd - late evenings: the Ursid Meteor Shower

    The late evenings of the 22nd and 23rd of December are when the Ursid meteor shower will be at its best - though the peak rate of ~10-15 meteors per hour is not that great. Pleasingly, the Moon will not affect our view during much of the night. The radiant lies close to the star Kochab in Ursa Minor (hence their name), so look northwards at a high elevation. Occasionally, there can be a far higher rate so its worth having a look should it be clear.

  • December 30th/ 31st after sunset: Venus closes on Mars

    After sunset at the end of the month, Mars, in Aquarius will be seen to the upper right of Venus low in the south-southwest.

  • December 6th and 20th: 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 6th the dark crater Plato and the young crater Copernicus will come into view. This is a very interesting region of the Moon!

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

  • We'll start our tour in Orion, sitting high in the east after dark. Orion lies along the celestial equator, and can be seen (at least partially) throughout the world. As he was invented in the Northern hemisphere, in New Zealand we see him upside down. Orion contains a number of interesting objects to observe with both binoculars or telescopes. If you look carefully you may see the middle star of Orion's sword has a fuzzy appearance. This is the Orion Nebula, which is a stellar nursery, a huge cloud of gas and dust in which new stars are being born. In the heart of the Orion nebula is a small group of bright stars known as the Trapezium Cluster. The ultraviolet radiation from these stars is lighting up the surrounding gas.
  • Following Orion's belt to the left we come to an upturned V shape of stars marking the head of Taurus the bull. At the bottom of this V is the bright orange star Aldebaran, at around 65ly away, representing the eye of the bull. The other stars in the V are part of the more distant Hyades cluster. At 153 ly away, the Hyades is the closest, and one of the best studied, open clusters to Earth. It is estimated to be around 625 million years old. Over time the cluster will continue to spread out and disperse into space, with some of the largest and brightest members already coming towards the ends of their lives.
  • Following Orion's belt to the right, you can follow the band of the Milky Way around the sky, through the False and Diamond Crosses to Crux, the Southern Cross, low in the south. Sat beside the Southern Cross is a dark patch called the Coal Sack Nebula. Known as a dark nebula, the gas and dust in this cloud is blocking the light from more distant stars, obscuring them from our view. To Maori the Coal Sack Nebula is known as Te Patiki, or the Flounder.
  • In our western skies, we see a trio of planets this month. Mercury is low on the southwestern horizon for the first half of the month, setting around an hour and a half after the sun, before sinking into the evening twilight after the 15th. Venus is higher in the west, the first thing you'll see as the sky begins to darken, and sets close to midnight. Mars is much fainter and to the top right of Venus, moving through Capricorn and into Aquarius over the course of the month
  • The Phoenicids reach their peak on 6th December and are thought to be associated with the comet D/1819 W1 (Blanpain). With the radiant in the constellation of Phoenix, not far from Achernar, this shower is well placed for southern hemisphere observers throughout the hours of darkness. The minor Puppid-Velids meteor shower also reaches its peak at around the same time with a zenithal hourly rate of around 10.
  • The Geminids are peaking on the 15th of the month. This is one of the best meteor showers of the year, but we are not well placed for viewing in New Zealand, with the radiant in the constellation of Gemini and well north of the equator. The constellation is at its highest around 3 am, but still appears low in our northern sky. Due to this low height we only see around half of the meteors visible to those in the northern hemisphere.