- The Society
- Astronomy Resources
The Night Sky This Month
Ian Morison tells you what can be seen in the night sky this month.
Updated: 16 hours 29 min ago
Ian Morison tells us what we can see in the northern hemisphere night sky during April 2017.The Stars and GalaxiesConstellations and Stars
Orion setting in the west, with upper part of Taurus and the Pleiades still visible. Also above Orion Gemini is visible with the stars Caster above and Pollux below. Also below Gemini is Procyon the only bright star in Canis Minor. Leo is visible in the south with a wonderful region called the Realm of the Galaxies just behind the tail. Between Leo's tail and the bright star Arcturus (in Bootes) is Virgo and Coma Berenices with many Messier objects in that region. High overhead is Ursa Major with the Plough. The central star of the handle, Mizar, is a double star (with Alcor) and observable in a telescope is faint red star up to the right of the pair.The Planets
comes into opposition on April 7th, lying in Virgo initially some 6 degrees above its brightest star, Spica. Visible all night, It will be due south at an elevation of 34 degrees at around midnight UT. The size of Jupiter's disk decreases slightly from 44.2 to 43.6 arc seconds as February progresses with its magnitude reducing very slightly from -2.5 to -2.4. 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.
rises around midnight (UT) and will be highest in the pre-dawn sky. Lying in the western part of Sagittarius, its diameter increases from 17 to 18 arc seconds during the month as it brightness increases slightly from magnitude +0.4 to +0.3. 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 just acquired a ZWO Atmospheric Dispersion Corrector which uses two contra-rotating prisms to combat the dispersion of the atmosphere at low elevations.]
passed through superior conjunction on March 7th and, on April 1st, will lie ~14 degrees above the western horizon at nightfall when it is at its greatest elongation, some 19 degrees, from the Sun. Then at magnitude -0.2, it brightness drops to magnitude +3 by the 18th of the month as it falls back towards the Sun. Mercury passes through inferior conjunction on the 20th and will reappear in the predawn sky by the end of the month. With an angular size of to 7.5 arc seconds on the 1st, increasing to 11 arc seconds on the 18th, no details would be expected to be seen on its disk.
As April begins, Mars lies in Aries but moves into Taurus on the 12th of the month. In early April, Mars has an elevation of ~20 degrees above the western horizon at sunset, but this reduces to ~11 degrees by month's end. On the 16th, it lies 4 degrees below the Pleaides cluster and then passes between the Pleiades and Hyades clusters on the 25th when it lies some 9 degrees to the right of Aldebaran. Its brightness falls slightly during the month from magnitude +1.5 to +1.6 whilst its angular diameter falls from 4.2 to 3.9 arc seconds. No details would be expected to be seen on its salmon-pink surface.
rises in the east about an hour before sunrise on the first of the month and then climbs a little higher each morning as April progresses. On April 1st, the disk, forming a slender crescent nearly one arc minute tall, is just 2 percent lit shining with a magnitude of -4.2. By the end of the month, Venus has its maximum brightness of magnitude -4.7 with its angular size reduced to 39 arc seconds and its illuminated fraction increased to 26 percent. It will then have an elevation of ~13 degrees at sunrise. 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.
April - a great month to view Jupiter.This is a great month to observe Jupiter which comes into opposition on April 7th. It is moving down the ecliptic and, at the start of April, lies in Virgo some 6 degrees above Spica (Alpha Virginis). It now reaches an elevations 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? 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.
April: Look for the Great Red Spot on JupiterThe night sky page gives a list of some of the best evening times during April to observe the Great Red Spot which should then lie on the central meridian of the planet. The times are in UT.
1st to 7th April - early evening after dusk: Mercury at its highest in the skyIf clear on the evenings of the first week of April, Mercury will be seen above the western horizon after sunset. Then it will have an elevation of some 18 degrees - so an excellent week to observe a somewhat elusive planet.
April 7/8th - all night: The waxing Moon closes on Regulus in LeoDuring the darkness hours of the night of the 7/8th of April, a waxing Moon closes on Regulus and is within 2 degrees as dawn approaches on the 8th.
10th April - all night: The Moon, one day before full, passes Jupiter in Virgo. If clear on the evening of the 10th and looking first to the south-east, one will see the Moon, one day before full, passing just 2 degrees above Jupiter in Virgo.
22nd April - after midnight: The peak of the Lyrid Meteors. Without any moonlight to hinder our view and from a dark rural location one, if clear, would have a chance of observing the peak of the Lyrid meteor shower with up to 10 meteors visible each hour. As one might expect, the shower's radiant is close to Vega in Lyra.
25th April - 1 hour after sunset: Mars passes between the Hyades and Pleiades Clusters. Looking low in the west after sunset on the evening of the 25th, Mars will be seen to lie directly between the Hyades (to its left) and Pleiades clusters - if clear, a nice photographic opportunity.
April 28th - a daylight occultation of AldebaranBefore dusk on the evening of the 28th, Aldebaran is occulted by a very thin crescent Moon. It will disappear behind the Moon's dark limb at 19:11 BST as seen from London and 19:07 BST as seen from Edinburgh and reappear at the bright limb at 20:07 BST as seen from London and 19:57 BST from Edinburgh. As darkness falls, Aldebaran will be seen to lie just below the Moon.
March 5th and 18th: An interesting valley on the Moon: The Alpine ValleyThese are two 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 is a thin rill runs along its length which is quite a challenge to observe. The dark crater Plato will also be visible nearby. You may also see the shadow cast by the mountain Mons Piton lying not far away in Mare Imbrium. This is a very interesting region of the Moon!Southern Hemisphere
Claire Bretherton from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during April 2017.
Kia ora and welcome to the April Jodcast from Space Place at Carter Observatory in Wellington, New Zealand.
New Zealand daylight saving ends the first weekend of the month, bringing our southern hemisphere summer abruptly to an end. On the bright side, the lighter mornings and darker nights will make it much easier to get out and do some observing.
One of the first objects you'll see in the evening twilight is bright golden Jupiter, rising in the east soon after the sun sets at the beginning of the month. It slowly crosses the sky through the course of the night, before disappearing in the west at sunrise. By the end of the month it will be rising well before dusk. Jupiter reaches opposition on April the 8th, meaning it will lie directly opposite the Sun in the sky and be overhead at midnight. At this time Jupiter is also at its closest to Earth, but the difference in angular size and brightness is not really noticeable to the naked eye.
Jupiter is always worth a look through a small telescope or good binoculars, revealing up to four of its large Galilean moons. The full Moon passes close to Jupiter on the 10th/11th of the month.
Jupiter sits in the constellation of Virgo, just to the left of the brightest star Spica. Last month I mentioned that Virgo is home to the Virgo Cluster of Galaxies, containing up to 2000 members. This month we'll take a closer look at some of those galaxies in more detail.
The cluster's centre lies around 54 Million light years away and it extends nearly 8 degrees across the sky. Many of the brighter galaxies are included in Messier's catalogue of non-cometary fuzzy objects and are easily visible with a small telescope. Perhaps the most famous member is the giant elliptical galaxy Messier 87, located close to the cluster centre. The second brightest galaxy in the northern part of the cluster, with an apparent magnitude of 9.59, M87 is easily observed with a modest 60mm telescope, and is in reach of a good pair of binoculars under excellent conditions, visible as a faint, hazy patch of light. Small telescopes may reveal the galaxy's elliptical shape, brightening towards the centre.
M87 is one of the most massive and luminous galaxies in the local Universe, estimated to contain the mass of around 2.7 trillion Suns, some 200 times that of the Milky Way, but only around one sixth of this mass is in the form of an estimated 1 trillion stars. It is also distinctive for its large number of globular clusters, with over 6 times as many as our own Galaxy. Close to its core is a 3.5 billion solar mass black hole, one of the most massive known, orbited by a fast moving disk of ionized gas, which is a strong source of radiation, particularly at radio wavelengths. In fact M87 is one of the brightest radio sources in the sky.
In 1918 American astronomer Heber Curtis detected a "curious straight ray" extending from the galaxy's centre, which we now know is a jet of energetic plasma blasted out from the nucleus of M87 at relativistic speeds. The central black hole of M87 is actually offset from the core by around 25 parsecs in the direction opposite to the jet, suggesting that the jet may be responsible for accelerating the black hole away from the galaxy's centre. An alternative theory suggesst that the displacement my have been caused by a merger with another galaxy.
To find M87, draw a line from Denebola at the tail of Leo to Vindemiatrix (or Epsilon Virginis), and the galaxy can be found just over half way along, close to Virgo's border with the Coma Berenices constellation.
Around 1.5 degrees back towards Leo is the M84/M86 galaxy pair, located just 17 arcminutes apart. Whilst M86 can be seen in 10x50 binoculars under good conditions, larger binoculars or a small telescope will be needed to pick up its companion easily. The two are visible in the same field of view, and in a 20cm or larger telescope a number of fainter galaxies can be seen nearby, including NGC 4435, NGC 4388, NGC 4402 and NGC 4438.
M86 and M87 are thought to be moving towards each other for their first galactic encounter.
The brightest galaxy in the cluster is the 9.4 magnitude Messier 49, located a little above M87 in our evening skies. M49 was the first member of the Virgo cluster to be found, and only the second galaxy to be discovered outside our local group. Messier 49 is interacting with the nearby dwarf irregular galaxy UGC 7636, which has a trail of debris covering 1 x 5 arcminutes of the sky.
M49 can be seen in large binoculars and small telescopes, with slightly larger telescopes picking up a bright core and large halo, but an otherwise featureless view.
Further around to the north in our evening sky, to the other side of Denebola is the main body of Leo, with the constellations brightest star Regulus or Alpha Leonis marking the lion's heart. Regulus is at the top of an upside down question mark as we see it here in New Zealand, which marks the head and mane of the Lion. With an apparent magnitude of 1.35, the star is the 21st brightest in the night sky, but it is in fact a system of four individual stars arranged in two pairs.
Regulus A is a spectroscopic binary comprising of a hot, young, blue-white main sequence star with a tiny companion of less than 0.3 solar masses, which is probably a white dwarf. Regulus B and C make a second pairing located 177 arc-seconds away from Regulus A. Resolving the BC pair from Regulus A is a good challenge for binocular observers, and certainly achievable with a small telescope.
A little below Regulus is another well known double star called Algieba or the Mane. First discovered by William Herschel in 1782, Algieba comprises a yellow-orange giant primary and a yellow-white giant secondary at magnitudes 2.3 and 3.5 respectively. The pair have an angular separation of around 4 arcseconds, so you won't be able to resolve them in binoculars, but with a telescope of aperture around 8cm or greater you should be able to split them.
Like its neighbouring Virgo, Leo is also home to a number of bright galaxies including the Leo Triplet, a small group of interacting galaxies consisting of spiral galaxies M65, M66 and NGC 3628. Often known as the M66 group, the Leo Triplet is located around 35 million light years away, and provides a fantastic opportunity to study galaxy interaction in our local Universe. Each of the three main members show signs of tidal disturbance with NGC 3628 exhibiting an impressive tidal tail extending for over 300,000 light years.
The triplet is located fairly close to Denebola, or Beta Leonis and around half way between Chertan, or Theta Leonis and Iota Leonis. Most small telescopes should be able to pick up the group, but M66, the brightest of the three, and M65, the second brightest, should also be visible in large binoculars.
This month the new moon falls on the 27th, so around this time will be the best opportunity for galaxy spotting.
Moving around towards the southeast, our winter constellation of Scorpius is rising in our evening skies at the beginning of the month and by around 11pm is joined by cream-coloured Saturn, sat a little below. By the end of the month Saturn will be rising shortly after 8pm. The Moon will be just to the left of Saturn on the night of the 16th.
Venus is moving quickly into our morning skies, rising a little over an hour before the Sun at the start of the month and 3 hours before at the end, when it will be joined in the dawn skies by faint Mercury sat lower and to the right of bright Venus.
Wishing you clear skies, and happy galaxy hunting, from the team here at Space Place at Carter Observatory.
Ian Morison tells us what we can see in the northern hemisphere night sky during March 2017.Highlights of the Month
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
Ian Morison tells us what we can see in the northern hemisphere night sky during March 2017.
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.
- 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.
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.
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.
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.