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Telescope House April Sky Guide

Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

Telescope House April 2018 Sky Guide

 

For those of us in the Northern Hemisphere, with the Sun now in the northern part of the ecliptic, the hours of light are now longer than those of darkness.  Given that the Vernal Equinox has only just occurred, for those of us "Northerners" there isn't a huge change in observing conditions straight away.  But by the end of April, for those at mid-northern latitiudes, hours of astronomical darkness have decreased by three, from just over seven on the 1st, to just over four on the 30th - quite a difference.  Naturally, the opposite will be the case for those readers in the Southern Hemisphere, who are now headed towards their winter, with darkness encroching day-by-day.  Wherever you find yourself in the world, as ever, there's plenty to see in the skies above us...

 

The Solar System

 

The Moon

 

The Moon starts April in Virgo, just past Full. Being so close to Full Moon, naturally, this is not the best time for deep sky observations, or imaging faint objects without significantly narrowband filtration.

 

The Moon reaches Last Quarter on the 8th, while residing in Sagittarius and can be found in loose conjunction with Saturn and Mars in the early morning sky. 

 

The Moon reaches New as it joins the Sun in Pisces on the 16th, after which it becomes an evening target. The following evening, it may be possible to pick out the tiny sliver of the very slim Crescent Moon alongside Venus, just after sundown, with the two bodies separated by around 6 degrees. The next evening, the Moon makes one of its regular jaunts through the Hyades. This occurs as the Moon sets over Europe. 

 

Moon and Venus, early evening 18th April (51 degrees N).  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.


The Moon then begins rising through a very steep part of the ecliptic from a temperate northern hemisphere perspective, gaining altitude night by night as it moves through the constellations of Taurus and Orion, until it reaches First Quarter high in the northern ecliptic on the Gemini/Cancer borders on the 22nd. This month's evening lunar cycle is one of the "High Spring Crescents" for which this time of year is notable and provides excellent opportunities for observation and imaging from temperate northern climes. 

 

The Moon reaches Full early in the morning of the 30th and can be found alongside Jupiter in Libra the following evening. Again, as was the case in early April, this is not the ideal time for deep sky observations and imaging. 

 

The Planets

 

Mercury

 

On the first of the month, Mercury is at inferior conjunction with the Sun, sitting between us and our parent star - and as such is unobservable. After this, it will reemerge on the morning side of the sky, though will be too faint and close to the Sun for observation until much later in the month. 

 

Merury at Inferior Conjunction 1st April 2018.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

Even by the 15th, Mercury sits at a disappointing +1.7 mag, even though it is in double figures in terms of angular size - now being 10.4 arc seconds diameter. The innermost planet also sits in a very shallow rising part of the ecliptic (in Pisces) from a temperate northern hemisphere perspective, which means it is under 4 degrees high at sunrise on the 15th (from latitude 51 degrees N) - although this figure will be much higher for equatorial and southern hemisphere observers. 

 

By the 29th, Mercury reaches its greatest western elongation, separated from the Sun by 27 degrees - though is still a rather disappointing +0.4 mag, 8.1 arc second diameter target, showing a 43% phase. Sitting in Cetus, Mercury is still low at sunrise from a northern temperate perspective - a little over 4 degrees high (from latitude 51 degrees N). 

 

Venus

 

Venus begins the month, in Aries, at -3.9 mag, separated from the horizon by just over 16 degrees (from latitude 51 degrees N). Venus presents a 10.6 arc second, 94% illuminated disk. 

 

By mid-month, Venus has increased its separation from the Sun to 23 1/3 degrees and now stands 19 degrees high in the west at sunset (from latitude 51 degrees N). Although it has slightly increased its angular size to 11 arc seconds, its phase has decreased to 91.7%, which means it has grown no brighter. 

 

On the 19th, Venus crosses the border into Taurus, approaching its highest northern point in the ecliptic. This means that it is approaching its greatest separation from the horizon at sunset from a northern hemisphere perspective. 

 

By the end of the month, Venus stands over 21 degrees high in the west at sundown, shining at -3.9 and presenting an 11.5 arc second diameter, 88% illuminated disk. Venus is separated from the Sun by 27 degrees - but is still some way from maximum solar elongation, which it will reach in mid-August. Crucially, however, for observers in the northern hemisphere, maximum eastern elongation of Venus will occur when the Sun is in a much more northerly part of the ecliptic. This will mean Venus standing under half the height above the horizon at sunset than it does now, when observed from the temperate northern hemisphere (those in the equatorial and southern regions of the planet will fare much better though). Now, up to mid-May, Venus will still be gaining altitude within the northern ecliptic, so this is the best time to observe our planetary neighbour from northern parts of the world. 

   

Venus, Sunset 30th April.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.


Mars

 

At the beginning of April, Mars can be found in Sagittarius and now shines at +0.3 mag, presenting an 8.5 arc second angular diameter. The planet can be found standing just under 15 degrees high in the south at sunrise (from latitude 51 degrees N). Mars joins Saturn in reasonably close conjunction during early April - the Ringed Planet being found under 1 1/2 degrees to the north on the mornings of the 1st-3rd. 

 

Mars and Saturn, Sunrise April 3rd.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

By mid-month, Mars has brightened up to -0.0 mag - noticeably brighter than Saturn and any other star which shares this area of sky. The planet has swelled to 9.6 arc seconds diameter and stands just over 15 degrees high in the south at daybreak (from latitude 51 degrees N). 

 

By the end of the month, Mars has brightened still further to -0.4 mag and grown to 11 arc seconds in diameter. During the next couple of months in the run up to opposition in late July, we will see Mars transformed in angular size and concurrently, brightness, as we draw alongside this fascinating world. Mars has now passed through its most southerly point in the ecliptic and while still low in the sky from a northern hemisphere observer's point of view, gently begins to climb in the sky for observers in these parts of the world. Southern hemisphere observers and those in the equatorial regions of Earth will still have the superior views of Mars in terms of angular separation from the horizon, but those of us in the northern hemisphere will take any advantage we can at present, as the major planets are all very much southern celestial hemisphere occupants at this point. Mars stands 15 1/2 degrees high at sunrise on the 30th (from latitude 51 degrees N).

 

 

Jupiter

 

April 1st finds Jupiter in Libra at -2.4 mag, 42.6 arc seconds diameter and standing 21 1/2 degrees high (from 51 degrees N) at transit point, which it reaches at 3.44am (BST). In early April we are a little over a month from Jovian opposition on May 9th, so now is the chance to observe the King of the Planet's approaching its annual best. 

 

The 15th sees Jupiter having expanded a fraction to 43.9 arc seconds across, but won't be noticeably brighter. The planet now rises at just after 10pm (BST) and transits at 2.44am, when it will stand just under 22 degrees high in the south (from 51 degrees N).

 

Jupiter, April 15th 04.21am BST, with Io and GRS Transit.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

At the end of the month, Jupiter has brightened a tad to -2.5 mag and is now 44.6 arc seconds diameter. It now rises at just before 9pm (from 51 degrees N) and stands 22 1/3 degrees high in the south. We are only nine days from opposition as the month ends, so don't miss the best observing opportunity of Jupiter you'll have all year. Naturally, being in the southern part of the ecliptic, this opposition will favour southern observers, but Jupiter is always a pleasing sight in a telescope or binoculars, no matter where in the world you are. 

 

 

Saturn

 

Saturn is a morning target in Sagittarius during April, rising at a little after 3.00am (BST, from 51 degrees N) and stands a little under 16 1/4 degrees high in the S at sunrise. At +0.5 mag, Saturn isn't especially prominent, but still brighter than any star in its resident constellation. It is separated from the Sun by just over 92 1/2 degrees on the 1st. 

 

Satrun and Moons, 1st April 2018.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

As previously mentioned, Saturn and the brighter Mars are in close conjunction in the first few days of April, separated by just over 1 1/4 degrees on the 2nd/3rd. Although Mars is still relatively poor in comparison with its spectacular showing later in the year, this should be an interesting sight to see for the early risers amongst us. 

 

The latter half of the month sees Saturn's path through the ecliptic go retrograde (east to west), and the planet brighten a little to +0.4 mag. 

 

The end of April finds Saturn still at  +0.4 mag and is now 17.5 arc seconds across. The planet now stands just over 16 degrees high at sunrise (from 51 degrees N), having transited around half an hour before.

 

 

Uranus & Neptune

 

April is not a great time for the observation of the outer gas giants. Neptune is reemerging from last month's superior conjunction in the morning skies and Uranus reaches its own superior conjunction on April 18th. In late April, Uranus will cross over the border from Pisces into Aries. Considering the slow pace that the outer planets move around the sky, this is a fairly rare event, but will only be until early December 2018, when the retrograde Uranus will cross back over the border into Pisces again, where it will remain until February 2019. 

 

 Uranus at Superior Conjunction, April 18th 2018.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

 

Comets

 

Comet PanSTARRS (2016 M1) is observable in the early morning, throughout April, in southern Aquila.  At a magnitude of +10.5, it won’t be especially bright, but will be visible in telescopes and larger binoculars.  It will be best seen in the early morning in mid April when the Moon is new. 2016 M1 will be heading leisurely south as the month progresses, brightening as it goes.   The comet may brighten to a peak of +7.5 mag in July/August, by which time it will only be observable from the southern hemisphere.

 

 Comet PanSTARRS (2016 M1) - path April 2018 (comet position shown 15th April).  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

Meteors

 

The Lyrid Meteor Shower

 

Peaking on the night of the 22nd-23rd April, the Lyrids are a regular, reliable shower.  While not as spectacular as the major showers such as the Perseids and Geminids, they are nonetheless worthwhile looking out for.  As the Moon will be at First Quarter on the 22nd on the Gemini/Cancer borders, it will hang around until the small hours of the morning, but will have set by around 3am.  

 

Lyris Radiant, 3am 23rd April.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com.

The Lyrids are fed by their parent comet, C/1861 G1 (Thatcher), a medium period comet which will return in 2276 (or thereabouts).  The particles left over by this comet hit the Earth’s atmosphere at a relatively leisurely 48 km per second, which means the kinetic energy of the meteors produced is relatively modest. This, coupled with small grain sizes means that the Lyrics aren’t especially bright as a mean average - around +2.0 mag.  Every 30-60 years, the Earth meets a relatively dense area of Comet Thatcher’s debris field when zenith hourly rates can hit several hundred.  As it stands, ordinary years normally peak at a ZHR of around 20 - not all of which will necessarily be seen.  However, timed exposures with wide field DSLRs or USB imagers with All Sky Lenses will doubtless pick up a few Lyrids, should the weather in your area be clear.  

 

Deep Sky Delights in Cancer and Leo

 

Leo and Cancer. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp., skysafariastronomy.com

 

These two neighbouring members of the Zodiac are quite a contrast - whereas Cancer is small and rather faint, containing no really bright stars, Leo on the other hand is bright and prominent and easily identified, even from a light polluted environment.

 

Cancer, as mentioned, is not a particularly prominent constellation, comprising as it does of stars no brighter than the 3rd magnitude.  Of its principle stars, Iota Cancri is probably the most interesting for amateur observers.  This star marks the most Northerly point of the main constellation and is a double star  of +4.01 and +6.57 mags.  The primary star is a yellow G-type star, the secondary a white A-type main sequence star.  Separated by 30 seconds of arc, these are an easy and attractive pair for small telescopes.  The angular separation of the two has not changed radically for over a century but it has been established the two are related.  It is estimated their orbital period is over 65000 years.

 

Nine degrees to the south of Iota Cancri lies one of the jewels of the night sky, the bright, expansive open cluster of M44, The Beehive or Praesepe.  At +3.09 mag this cluster is an easy naked eye object from a reasonable observing site and at over a degree in size, is pretty unmissable.  Known since antiquity, M44 was known as Phatne - "The Manger" to the ancient Greeks (Praesepe being the Latinised translation of this title), though its first datable mention in literature came in 260 BC, when the Greek poet Aratos called it the "Little Mist". M44 was also contained in Hipparchus' star catalogue of 130 BC.  The Beehive as a name seems apt, as the core of M44 could be argued to resemble a natural hive, with outlying stars being "the Bees" hovering around it.

 

Praesepe (M44-NGC2632), Comet Lovejoy and Meteor (w marking) by Eddie Yip. Reproduced under Creative Commons License.  Follow Eddie on FLICKR here.

Containing over 1000 individual stars (over 75 of which are observable to the smallest amateur telescopes), M44 seems to share a proper motion with the Hyades in neighbouring Taurus, which seems to suggest a common point of origin.- both clusters seem to be of a similar age too (around 600-730 million years).  The Beehive lies 570-610 light years away from us and is estimated to be about 12 light years in diameter (though its tidal influence reaches much further).  This cluster should be seen by everyone - it is easy enough in a modestly-sized pair of binoculars.  The mix of stellar components make for a lovely imaging opportunity too.

 

Eight degrees to the southeast of the Beehive, another open cluster, M67, is to be found.  Although fainter and more compact that M44 at +6.90 mag and 25 arc minutes, it is in its way, as attractive a target as its neighbour.  Discovered by Johann Koelner in the late 1770s, M67 was catalogued by Messier in 1780.

 

M67 by Thomas Jäger. Reproduced under Creative Commons License.  Visit Thomas' Website here.

Comprising of about 100-or-so observable members (out of a total of over 500 stars), many of which are similar it class to the Sun, M67 is one of the oldest clusters in our galaxy.  It is thought to be around 4 billion years old - nearly as old as our own Sun and lies 3000 light years away.  M67 does also contain some "blue stragglers" - stars that technically speaking it should not contain.  Whether these have been swept up by M67 during its journey around our galaxy (or not), is a question that, to date, remains unanswered.  Observers using higher power magnifications will resolve some spectacular chains of stars in M67.  It truly is a lovely object.

 

Further southeast (by just under 7 degrees) from the delights of M67 is a much more challenging target, the beautiful spiral galaxy NGC2775.  Though not intrinsically conspicuous at +10.10 mag, it is a compact target at 4.3 x 3.3 minutes of arc and has a comparatively bright core.  Lying some 60 million light years away, NGC2775 is an exotic blend of a spiral structure and large elliptical core, which itself is ringed by pronounced hydrogen regions.  The arms of the outlying spiral sections are very finely structured, though this is only really visible in long duration images.  Visually, NGC2775 is visible with a reasonable-sized instrument, though a larger scope may on occasion show interactive stream of material from NGC2777, which is tidally interacting with its larger neighbour.  Whilst a challenge, NGC2775 has been the site of some 5 Supernovae since the mid-1980s, so who knows what you may find there?

 

NGC2775, Copyright Adam Block/Mount Lemmon SkyCenter/University of Arizona.  Image reproduced under Creative Commons License. 


Cancer contains many galaxies between the +12-14 mag range. Being located so close to the Leo, Leo Minor and Hydra galaxy clusters, it would seem a fairly safe assumption that Cancer's galaxies are gravitationally clustered.  Studies of proper motion based on spectral shift have confirmed, however, that these galaxies are not related.  Still, there is much for owners of large telescopes and astrophotographers to enjoy galaxy-wise in Cancer.  Although many of these objects are challenging and are not as easily-observed as those in the adjacent constellation of Leo.

 

When gazing towards Leo, there can be little doubt we are now in the part of the year known as "Galaxy Season", as this area of sky is littered with them.  Galaxy hunting is not solely the preserve of those with the supposedly prerequisite "Big Dob".  Although to see much in the way of detail in many of the objects mentioned this month, aperture will certainly help, a good deal of these can be seen with smaller telescopes and large binoculars from decent, dark observing sites.  However, patience and care will be needed to pick the faint glow of these fantastically distant objects from the background sky.  However, to discern structure in many of the galaxies we'll cover requires one of two things: a large telescope of at least 10-inches of aperture (preferably more), or reliance on accurate, autoguided long-duration exposure astrophotography.  To appreciate the true beauty of these massive, yet seemingly delicate structures, you need one or the other - though their location and observation (yet again), will largely be down to sky conditions - with galaxies, the darker the better!  Careful, gentle filtration will help with galaxy observation from more light polluted environments, but narrowband filters like the OIII, H-Alpha and others will rarely help as much for galaxy observation as they do for nebulous objects (except when a galaxy has particular emission regions, peculiar to these wavelengths of light).  A good Skyglow, CLS or broader "Deep Sky" filter will help increase the contrast of an object against the background sky, without cutting off many of the useful wavelengths that the galaxy is transmitting on.  A galaxy's spectral output is much broader than typical nebulosity, so gentle filtration produces the best results.

 

The first object on the list for observation is one of the most difficult to see, but probably one of the simplest to locate and the closest, galaxy-wise - the Leo I galaxy.  Leo I sits a third of a degree north of Regulus, Alpha Leonis - the principle star of Leo (though some publications rate it as closer).  Leo I is an elliptical galaxy of reasonable angular size (12 x 8.5 arc minutes) and of photographic magnitude +11.15. Leo I is a one of its furthest satellite galaxies of our own Milky Way, lying just over 800,000 light years from us.  Leo I was first detected in the Palomar Sky Survey, taken with the observatory's 48-inch Schmidt Camera in 1950.  Leo I's visual magnitude is deemed to be around +9.8 mag, which should put it easily within the reach of amateur instruments.  However, Leo I's easy-to-find location is also its potential downfall from a visual perspective: it lies so close to Regulus that the neighbouring galaxy is almost drowned out by its glare.  There are reports of the galaxy being found in 10-12-inch class telescopes, but it is very likely that an observer would have to place Regulus just outside of the field of view, using appropriate magnification, in order to see our galaxy's most distant satellite at all.  Leo I will appear as a misty oval of light, with no great discernible structure even in large telescopes.The galaxy appears to have no attendant globular clusters and contains few stars of advanced metallicity, meaning the stellar population is comparatively young - probably little over twice the age of the Sun.  The galaxy is surrounded by a halo of attendant gas, which it may (or may not) have formed from.

This unusual object will be a challenge, but if found, you will be witnessing the furthest reaches of our own galaxy's orbital sphere of influence and in all likelihood its youngest attendant.

 

Roughly nine degrees east of Leo I lie a spectacular grouping of galaxies: the Messier objects M95, 96 and 105 (and its attendant galaxies NGC 3377 and NGC3384).  This group occupies a compact area of sky (about 3 x 1.5 degrees of sky) and can be found halfway on a line drawn between Regulus and Iota Leonis - one of the rear legs of Leo.  Of the three galaxies, the beautiful M95 is the most Westerly.  M95 is a barred spiral galaxy, placed almost face-on from our perspective. M95 was discovered - along with the nearby M96 - in 1781, by Pierre Mechain.  Messier catalogued both objects less than a week after Mechain found them.  At +9.69 mag, M95 is a relatively easy, compact object at 7.4 x 5 arc minutes in dimension.  Lying 31 million light years away from us, it is the closest of its group by a million light years.  As M95 is a barred spiral, it is likely that most observers with decent-sized telescopes will see the galaxy's central core region as a slightly elongated object, surrounded by a fainter haze of its arms.  Long duration images of the system reveal its structure in all its glory - the two massive spiral arms shedding stars into further outlying feathered lesser arms.  If, as it has been suggested, our own galaxy is a barred spiral, it could look much akin to M95 to outside observers, though our galaxy may have more in the way of outlying spiral structure in its arms.

 

M95 and M96 by Mark Blundell.  Image reproduced by kind permission.

Next door to M95 by a mere two-thirds of a degree is another lovely spiral, M96.  A similar angular size to its neighbour, it is slightly brighter at +9.3 mag.  In contrast to M95, M96 appears to be dustier, but has a more compact core.  It is often listed as a double barred spiral.  This double barring, along with the wide spread of its arms and the galaxy's dusty nature make its spiral structure less well-defined than its neighbour M95's.  Similar in angular size to M95, at 7.8 x 5.2 arc minutes, M96 appears as a more compact 3 x 5 arc minute object in a 10-12-inch-class telescope, its bright central core surrounded by a fainter ring of starlight which make up its arms.  The reason it also appears slightly brighter than M95 in some listings is that the galaxy is considerably foreshortened in comparison to its neighbour.  Some listings incline it as much as 53 degrees to our line of site, whereas M96 is also recorded as being at a less extreme 35 degrees!  Whichever listing is correct, M96 is a great target for visual and photographic observations.

 

Just under a degree to the north of M96 sits the grouping of M105 and the nearby NGC 3384 and 3389.  Of the three, M105 is the dominant and brightest at +9.3 mag.  It is often described as the analogue of Elliptical galaxies - and as such is much studied.  M105 is a later addition to the Messier list (added by 20th Century Astronomer Helen Sawyer Hogg), though discovered in 1781 by Mechain, Charles Messier did not confirm its discovery at the time and it was left out of his original listing.  It's difficult to understand why Messier chose not to include M105, as it is prominent enough - a misty patch of light in small telescopes and a condensed glow, with a healthy-size core in larger instruments.  Elliptical galaxies, but their nature are not generally thought to be as beautiful or as characterful as their spiral counterparts, but this should not put observers off trying to locate M105.  Indeed, many Astronomers now consider Elliptical galaxies to be the ultimate evolution of galaxial structure after two spirals merge - the end result of the Milky Way's potential meeting with M31 may well result in a similar structure to M105.  A clue to M105's past is that it contains few areas of star formation and a reasonably elderly stellar population, suggesting it is a more advanced galaxy in terms of age.

 

The second Elliptical in this close trio, NGC 3384, 7 arc minutes to the NE of M105, is almost as conspicuous as its neighbour at +9.89 mag, but is presented to us at a much more oblique angle.  Appearing elongated, even in small telescopes, larger instruments can reveal a clear, bright core and the misty halo of NGC 3384's outer regions.  So easy is it in comparison and proximity to M105, it is difficult to believe that it was overlooked by Mechain and Messier.  William Herschel discovered it in 1784.  Although listed as the catch-all description of an elliptical galaxy, the more precise description of NGC 3384 should be as a Lenticular.  The galaxy has revealed a central bar structure in long duration astrophotography and like M105 shows an older star population than the mean average.

 

NGC 3389 is the most challenging of this trio to observe - whereas the two previously-mentioned ellipticals are bright and their structure obvious, NGC3389 is a whole two magnitudes fainter than either at +11.89 mag and much more the visual preserve of larger telescopes.  NGC 3389 is a spiral galaxy and shows a much more blue, energetic cast in long duration images (maybe somewhat reminiscent of a mini M33).  This is largely due to its disassociation with the group - although close in angular proximity to M105 and NGC 3384, NGC 3389 actually lies round 64 million light years distance, roughly twice that of its neighbours and has no connection to them. Instruments of the 10-inch+ range will show it, though it will be a struggle to observe in less powerful scopes. It appears as a pale misty patch to the SE of NGC 3384 and little detail is to be expected in most telescopes, though those owning larger instruments have reported a certain textured "lumpiness" to its appearance in the eyepiece.

 

At low power (sub x40) it is possible to squeeze M96, M105 and NGC3384 in the same eyepiece, as it is also possible to do with M95 and M96 - though owners of low focal ratio reflectors should be advised that it is often inadvisable to attempt to use such low magnifications, lest the shadow of the secondary mirror interfere with the view!

 

Leaving this group of galaxies aside, we return to the aforementioned Iota Leonis and trace a line back up one of the rear "legs" of Leo, until we come across the +3.34 mag star Chertan or Theta Leonis (sometimes known as Chort or Coxa).  Tracing the line back to Iota Leonis, stop approximately halfway: here is location of the next group of galaxies, the M65 Triplet, more commonly known simply as the Leo Triplet.  This triplet contains the Messier objects M65 and 66 and the elongated NGC 3628.  All three objects are spiral structures, though unsurprisingly they present themselves to us in differing aspects.  

 

M65 and 66 were discovered by Charles Messier in 1780, though often misattributed to Mechain.  Of the two, M65 is slightly smaller and fainter at + 9.30 mag. It has a bright central bulge and pretty luminous arms.  Presented at a significant incline to our perspective, occupying an area of 9.8 x 2.9 arc minutes, M64 also features noticeable dusky lanes within its arms, though these may well be made more prominent by foreshortening.  M66, on the other hand, is a broader barred spiral, brighter than its neighbour at +8.9 mag and taking up more area in the sky at 9.1 x 4.1 arc minutes. M66's spiral arms are not as regular as M65's, which seems to suggest total interactions with neighbouring NGC 3628 in the past, as does a displaced cloud of hydrogen which has moved outwards from its arms and now sits, motionless, around its galactic halo.

 

M65, M66 and NGC3628, by Mark Blundell.  Image reproduced by kind permission.

NGC 3628 is the faintest of the three at +9.50 mag and the longest at 13.1 x 3.1 arc minutes in dimensions.  This is a fascinating spiral, which is presented edge on to us and is bisected through its centre by a long, dark dust lane.  This is difficult in smaller telescopes, but becomes extremely prominent in larger telescopes.  10-12-inches of aperture will show it well, but in a telescope of 14-16-inches of aperture it is unmistakable (in a similar way to NGC 891).  Discovered by William Herschel in 1784, NGC 3628 is pretty obvious in relation to its neighbours, so again, it is mysterious why it wasn't discovered earlier.  NGC 3628 has tidally interacted with M66 which has lead to a huge stream of stars breaking away in a staggering 300,000 light year long trail.  This feature is only apparent in very long and well-processed astrophotographs, but is amongst the most spectacular and extreme pieces of evidence for gravitational interaction amongst galaxies in the sky.

 

All three galaxies can sit within the field of view of a low power eyepiece in a rich field instrument, but large binoculars will show them well as a triplet too.  Sadly, NGC 3628's dark lanes won't be revealed by binoculars, but the Leo Triplet is well worth your attention, regardless of whatever optical aid you deploy.

 

All the galaxies mentioned so far, bar the outlying NGC 3384 and (confusingly) the much more local Leo I, are all members of the extended Leo I group of galaxies.  For clarification, Leo I the galaxy and the Leo I group of galaxies are completely unrelated!  The next group of galaxies we shall come to belong to the Leo II population, an associated, but separate group.

 

Moving Northwards from the M65 Triplet, we come to another compact triplet of galaxies, the spiral NGC 3632 and a close pairing of elliptical galaxies NGC 3607 and 3608.   2 1/2 degrees S from Zosma, Delta Leonis, (the base of the Lion's tale), the pairing of NGC 3607 (+ 9.89 mag) and NGC 3608 (+ 10.80 mag) can be found.  Separated by just 5 arc minutes, the pair are easily located in small instruments, though it is the brighter (4.6 x 4.0 arc minutes) 3607 that is the more conspicuous. NGC 3632 is to be found three quarters of a degree to the east of this pairing.  At+10.6 mag NGC 3632 was discovered by Herschel, again in 1784.  It is a lovely, if compact, spiral and is also listed at number 40 on Patrick Moore's Caldwell Catalogue.  Although recorded as an 11th magnitude object, it appears brighter due to the concentration of this light over its compact 2.7 x 1.9 arc minute area.  Larger telescopes are needed to bring out any detail in its outlying spiral arms.

 

Finally, we come to a rather brighter galaxy, NGC 2903.  This is a wonderful spiral structure and at magnitude 8.9, it is easily visible with a small telescope.  With dimensions of 12.6 x 6.6 arcminutes the galaxy is seen from a rrather oblique angle, which contributes to its relatively high surface brightness.  NGC 2903 is pretty easy to find, located as it is around 1 1/2 degrees below Leo's "chin" or "mouth" star, Lambda Leonis.

Sitting at a distance of 20.5 million light years, it is still fairly easy to see the dust lanes and emission nebulae. NGC 2905 is a prominent brightarea in NGC 2903. NGC 2903 is thought to be about 80% as large as our own Milky Way Galaxy.  The similarities continue with NGC2905's spiral structure and noticable central bar. Hubble images show that NGC 2903's globular clusters seem somewhat brighter and more noticable than our Milky Way's globulars would be if viewed at a similar distance.  This suggests they and their parent galaxy may be somewhat yonger than our own.

NGC 2903 also appears very efficient in terms of star formation - its notable ring of material around its core being particularly rich in new stars.  It is thought that the central bar's tidal forces are compressing this material and this is the driving mechanism behind this formation.

 NGC 2903 by Mark Blundell.   Image reproduced by kind permission.

 

Original text: Kerin Smith