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Telescope House April Sky Guide

We have a Nova in Cassiopeia to observe at present.  Novae are more common than the much more powerful (and rarer) Supernovae, but nonetheless are worth finding, as these are some of the more energetic events to observe in the night sky.  Novae occur when gas from a larger star spirals into an accretion disk around a companion white dwarf and is heated up to the point fusion occurs, which sets off a huge burst of energy, which can significantly outshine the stars in the system for a brief period.  This current Move has been classed V1405 Cas and can be found in telescopes or binoculars, but is not visible to the naked eye as some can be.  A map to the location of this Nova can be found below.  This event seems to be around 7.5-8th magnitude - so not bright, but will be interesting to watch over the next few weeks.  Novae oftener-occur as further accretion events occur, so we may see more from duo of stars.


The Solar System


The Moon


The Moon begins April at an 83% Waning Gibbous phase on the Libra-Scorpius borders, having risen just before 12am (BST). Subsequently, this time of the month will not be the most opportune time for observations of deep sky objects, or astrophotography (without use of narrowband filters), beyond the latter part of the evening.  There will still be a window for earlier evening observing in true darkness before the Moon rises, but the striking hours of darkness in the northern hemisphere, following late March’s Vernal Equinox, will slowly encroach on this period of darkness.


Last Quarter occurs on the 4th, with the Moon in Sagittarius. Rising at just past 3.30am (BST).  The Moon then climes up the ecliptic to meet the Sun over the next week, meeting our parent star on the 8th in Pisces.


For those of us in the northern hemisphere, we continue our series of lunar evening apparitions known as the “High Spring Crescents”.  These phases are one of the best times of the year to observe the Moon from the northern hemisphere, as it is at these times that angular separation from the horizon is at its most extreme, for those of us in these parts of the world.  On the evening of the 15th, the 11% illuminated Crescent Moon slides between the Pleiades and the Hyades star clusters in Taurus, which will make for a very pretty sight with the naked eye and in low power binoculars - and will afford those with telescopes a grand view of the sunward side of the Moon.  Sadly, at the present time lunar libration does not afford the telescopic observer a great view of the minor Mare on the Moon’s eastern limb.  Though the large circular bullseye of the Mare Crisium is always very prominent at this time of year, especially at high spring crescent phase, the minor “seas” - Undarum, Marginus, Hublodtainum, Smythii - which occupy the limb are listed in order of observing challenge.  Mare Smythii is not visible at all at this point and we will have to wait until later in the year, when libration is more favourable, to observe it at all.


First Quarter is reached on the 20th, in Cancer, with the Moon high in the northern ecliptic, sitting juts to the north of the beehive cluster as the Sun sets.  The great walled crater Plato will be emerging from terminator on this evening and the high ramparts of the easterly side of the crater will be casting long shadows on the smooth floor, which sits some 2km above.  The 101km-wide Plato is thought to have formed around 3.8 billion years ago, a comparatively short time after the Mare Imbrium, which lies just to the south.  Plato’s dark basalt floor is noticeable in having a low albedo factor and the crater has been commented to have had more than its fair share of TLPs (Transient Lunar Phenomena) observed over the years.  TLPs are still reasonably controversial and it is thought that many of these observations are simply down to contrast effects caused by lighting conditions when the Sun is at an oblique angle to the crater - such as this evening.  If the weather is clear and you have a telescope, we encourage you to have a look at this interesting part of the Moon - though can’t guarantee any TLPs will be observed.


From First Quarter, the Moon gently glides down the southern decline of the ecliptic until it reaches Full phase on the 27th in Virgo.  This Full moon will be a perigee-syzygy event - a so-called “Supermoon”, caused when the Moon is at maximum illumination at its closest part of its slightly elongated orbit of Earth.  At these times the Moon can appear up to 30% larger than when Full at apogee - the furthest point from Earth.  This effect can be amplified somewhat by atmospheric refraction, which makes the Moon appear slightly larger when low in the sky, but apart from that has little real scientific significance.  The Full Moon is actually one of the most disappointing times to observe the Moon (unless you’re looking round the extreme limb), as the effect of having the Sun directly behind us bleaches out much of the detail visible of lunar features, which are actually seen much better during Crescent and Gibbous phases.  


The Moon ends April four days later, at a 87% illuminated Waning Gibbous phase, while resident of Ophiuchius. 


Mercury 


Mercury begins the month as a morning object in Aquarius.  At -0.5 magnitude, the planet is reasonably bright, but will only sit just under 2 degrees high at sunrise on the 1st (from 51 degrees N).  Mercury will be descending towards the Sun and as such will be practically impossible to observe from mis-northern latitudes, though those in the equatorial regions of the planet and further south will fare better.  As the month progresses, Mercury dips further south and the angular separation from the Sun decreases until in reaches Superior Conjunction on April 19th.


Beyond this, Mercury then becomes an evening target in Aries and rises in a much more favourable position in the sky for those of us in the northern hemisphere.  The Solar System’s plane appears to set in the evening at an angle much more inclined towards the vertical, than the horizontal, at this time of year when observed from northern hemisphere.  As such, this evening apparition of Mercury will be very favourable.  Mercury appears to rocket northwards during the rest of the month, passing the much brighter Venus on the evenings of the 24th and 25th, when the planet will appear to be -1.7 mag (not quite the brightest Mercury ever appears, but close) and will stand 5 degrees high at sunset (from 51 degrees N).    Over the next few days, the planet gains around a degree in altitude a day, making it progressively easier to find the planet at dusk.  The planet ends the month at -1.2 magnitude brightness and just under 84% illumination, sitting just under 10 1/2 degrees in altitude (from 51 degrees N) at sunset.  Make the most of this evening apparition, as this is arguably the best one of the year, as observed from the northern hemisphere.  

Venus 


Venus is emerging from Superior Conjunction on 26th March.  As with Mercury, Venus is emerging on the eastern evening side of the Sun, though the planet moves in a much more sedate pace than its neighbour.  On the 1st, Venus is just 2 degrees from the Sun and unobservable.  We have to wait until the tail end of the month to see it at all.  As previously reported, Venus comes into conjunction with the Sun not he evening of the 24th and 25th, but this will be difficult to observe at best.  By the time the month ends, Venus will sit 6 1/2 degrees high at sunset (from 51 degrees N), shining at -3.9 magnitude.




Mars


Mars is still observations in Taurus in the evening, being found between the “Horns” of the Bull for much of the month. Transiting at just after 5.30pm on the evening of the 1st, Mars is just 5.3 arc seconds across and is +1.3 magnitude.   As we have mentioned in previous Sky Guides, Mars is a comparatively small planet in relation to the Earth, the planet’s disk appears to shrink quite rapidly once we begin to pull away from it on our faster interior orbit. The planet is well past its best now and it will be a real challenge to pick up any detail from observations of its tiny disk, even at high power in a large telescope. 


By the 15th, Mars’ disk has shrunk to a 4.9 arc second diameter target, shining at +1.4 magnitude. The planet still appears to be climbing northward in the Ecliptic from our perspective and is a very reasonable height from the horizon at transit point - just over 64 degrees (from 51 degrees N), which it reaches at just after 5pm (BST). 


By the end of April, Mars will present a 4.6 arc second disk. By this point, the planet will be +1.6 mag brightness. As previously mentioned, while Mars is still observable with reasonable magnification in a telescope, it is now so small that it is unlikely any real detail will be able to be discerned.  


Jupiter


Jupiter emerged from Superior Conjunction on 29th January and while it is now 48 degrees from the  the Sun’s glare as a morning target, the planet is still very low in the sky from northern hemisphere at the month’s beginning, so it won’t appear at its best in telescopes.  Jupiter appears at -2.1 mag at the month’s beginning and is just under 35 arc seconds in diameter and stands just over 10 1/2 degrees above the horizon at sunrise (from 51 degrees N).  


By mid-month, nothing much has changed.  The planet is still -2.1 mag, but has increased its diameter fractionally to 35.9 arc seconds across.  Jupiter is now just overt 13 1/4 degrees high (from 51 degrees N) at sunrise.


The latter part of the month seems Jupiter move into Aquarius from Capricornus and the 30th sees Jupiter sitting at 16 1/4 degrees elevation in the SE at sunrise.  By this point it will be shining at -2.2 magnitude, presenting a 37.3 arc second diameter disk and while Jupiter is always an interesting slight in a telescope, we will have to wait until the Summer before it is higher in the sky and in an significantly better position to observe.


Saturn 


Sitting in a similar part of the sky to Jupiter, Saturn’s found just under 12 degrees from its neighbour in the middle of Capricornus.  At +0.8 magnitude, at the month’s beginning, the Ringed Planet will stand 13 degrees high (from 51 degrees N) at sunrise.  As with Jupiter, Saturn’s position is not great for telescopic observations, but as the month progresses becomes easier find in the morning twilight, as it slowly climbs in the sky.  Ending the month at +0.7 mag, Saturn stands a little over 17 1/2 degrees high in the SE as the day begins.




Uranus and Neptune 


The two outer gas giants are both sides of Superior Conjunction this month. The fainter Neptune is further west within the Ecliptic than Uranus and is slowly emerging from March’s Superior Conjunction, but due to its intrinsically faint magnitude will be lost in the morning twilight, making it unobservable until considerably greater separation from the Sun occurs.


Uranus is in Aries at +5.9 mag and presenting a 3.4 arc second diameter disk on the 1st.  By the time Astronomical Dusk has occurred on the 1st, Uranus is s just over 4 degrees high above the horizon (from 51 degrees N) - so effectively will be unobservable.  As the month progresses, the planet appears to dip sunward with some rapidity.  Uranus reaches Superior Conjunction (the opposing side of the Sun, as it appears from our perspective here on Earth) on April, 30th and it will be some time before both the outer planets will be observable again.


Comets


C/2020 R4 Atlas is visible in the morning sky as it emerges from solar conjunction.  Those with telescopes or large binoculars may wish to hunt out comet as it is making a steady trek through Aquila and Hercules  during the first part of April, though it will be fading as it does.  From the 15th, C/2020 R4 Atlas appears to accelerate as it passes its closest point to Earth and shoots through Hercules, Corona Borealis and Bootes.


As reported in earlier sky guides, C/2021 A1 Leonard looks like it will be a comet to look forward to, as it passes Earth by 0.23 AU in December 2021, just prior to perihelion.  It is predicted that it may reach around the 4th magnitude, so could well be a good binocular and telescopic sight.  We’ll keep you posted on developments of this comet as clearer picture emerges.  It will emphatically not be another Comet Neowise, unfortunately, but does look like being something to look forward to.



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 Gibbous Phase on the 22nd in Leo, it will hang around until the small hours of the morning, setting at just after 4.30am and sadly interrupt the shower.  


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, even with the Moon’s negative influence, short timed exposures with wide field DSLRs or USB imagers with All Sky Lenses will doubtless pick up the brightest of Lyrids, should the weather in your area be clear.


Deep Sky Delights: Galaxy Season Continues in Coma Berenices


Last month we have covered a vast area of the heavens - and a particularly Galaxy-rich one - the constellations of Ursa Major and neighbouring Canes Venatici.  The saga continues this month as we examine the contents of Coma Berenices.  Seeing this constellation in the evening time really gives one a feeling that Summer is just around the corner, though for those in higher Northern latitudes, this has to be balanced with the rapidly diminishing hours of true darkness in which to observe.


Coma Berenices is a rather poor constellation, containing three major stars of the 4th magnitude.  However, what it lacks in brightness, it more than makes up for in deep sky objects.  This first of these is not a galaxy, it's actually an open star cluster - Melotte 111.  This collection of around 40 stars is loosely gathered over a 4 1/2 degree area and was first noted by Ptolemy in around 138CE.  This hazy collection is visible to the naked eye from a good site, and although once represented as the tail of neighbouring Leo, was re-classified by Ptolemy as a constellation in its own right, representing the legend of the Egyptian Queen Berenice's hair which was sacrificed to the goddess Aphrodite in return for the safe return  of the Queen's husband Euergetes.  Legend has it that Aphrodite was so pleased by the gift that she placed it in the sky for all to see - hence the constellation's title, Coma Berenices - or Berenice's Hair.  


In reality, Melotte 111 lies around 300 light years away from us, making it the third closest star cluster to us, after the asterism of the Plough or Big Dipper in Ursa Major and the Hyades in Taurus.  Somewhat curiously, Meotte 111 is neither receding or approaching us, rather keeping pace with our position in our mutual journey around the Milky Way galaxy.


Due to its large size, Melotte 111 is best seen in low power binoculars or by the naked eye.  However, wide field images of the area reveal it well.


Just under a degree and a half from the Eastern edge of Melotte 111, sits the elliptical galaxy NGC4494.  This 4.8 x 3.5 arc minute object is +9.80 mag and t is somewhat bland in appearance, though can be seen in instruments of many sizes.


The same cannot be said of NGC4494's neighbour, the spectacular NGC4565, otherwise known as the Needle Galaxy.  This +9.60 mag, 15.8 x 2.1 arc minute edge on spiral is a delight in larger instruments and has surface brightness high enough to be seen in many smaller instruments.  Discovered by William Herschel in 1785, NGC4565 is much beloved of astronomers, and is often considered the Springtime equivalent of the Autumnal NGC891 in Andromeda.  A large dust lane intersects the galaxy right down its major axis - this lane can clearly be seen in telescopes of 8-inch aperture and above in notable relief against the glow of the galaxy's centre.  However, this galaxy is well worth seeking out no matter what size your telescope is.


Three and 3/4 degrees to the N of NGC4494, sit a pretty, if rather fainter (at +10 mag) spiral galaxy - NGC 4559.  This spiral is 10.7 x 4.4 arc minutes in size and rather lower in surface brightness than its better-known neighbour.  It is thought to lie some 35 million light years away from us.


NGCs 4278 and 4414 lie to the NW and N of NGC4494, both equidistant by about 3 3/4 degrees.  An elliptical and a spiral galaxy respectively, these are rather compact targets and worth seeking out if you have a larger telescope.  Though part of the greater Coma cluster of galaxies, they lie further away from us at around 55 and 58 million light years distance.


Moving down diagonally SE through NGC4494, by about 4 degrees, we come to the pretty spiral galaxy NGC4725.  This 10.7 x 7.6 arc minute object sits at +9.39 mag  and displays a prominent central bar, around which loops a bright halo.  NGC4725 is somewhat of an oddity, having just one enormous continuous spiral arm, which appears to loop round itself 3 1/2 times.  Most spiral galaxies display at least two arms, so NGC4725 is a rarity.  It lies some 40 million light years from us.


Another 4 degrees SE of NGC4725 lies one of Coma's highlights, and much beloved of imagers and visual observers alike - the marvellous M64 - otherwise known, for reasons that will be obvious to all those who see it, as the Black Eye Galaxy.


First discovered in 1779, by astronomer Edward Pigott, M64 was independently found by Messier the following year.  This +8.5 mag, 10 x 5.4 arc minute object can be found in small telescopes and even powerful binoculars from a good site.  The reasons for its nickname will become apparent to all those who glimpse it through a more powerful scope: M64 has a large dark dust lane encircling its core, which stands out in stark contrast to the soft glow of its interior.  It does indeed look somewhat like a black eye - albeit a rather large one on the cosmic scale..  M64 lies relatively close to us - some 17 million light years - but is a rather diminutive spiral galaxy , which is wreathed in a larger out halo of stars, thought to be the remnants of an absorbed satellite galaxy.  This halo appears to rotate in the opposite direction to the main body of M64 and may be responsible for the compression of the dark black eye feature, making it more prominent to outside observers than it would be otherwise.  M64 is a very rewarding target for astrophotographers as Mark Blundell's photo shows.  Don't miss this rewarding target, whatever optical aid you employ.


Just over 5 degrees further SE from M64, lies a lovely globular cluster, M53.  Discovered in 1775 by Bode and catalogued by Messier 2 years later, M53 is 2.6 arc minutes in diameter and +7.6 mag in brightness.  While not quite as prominent as other major globulars, this is easily seen in telescopes of any size and also shows up in binoculars.  Larger telescope will resolve its core well, but M53 is really a victim of its distance from us - some 58,000 light years away.  When compared to M13 in Hercules, at 25,000 light years distance, M53 seems quite distant.  


Next door, by a degree to the E, is a much slightly larger and poorer globular, NGC5053.  At +9.47 mag brightness and 5.2 arc minutes diameter, this is a much more difficult object than its more illustrious neighbour, though is fairly easy to find due to its proximity.  Both globulars are approaching us at around 79 km per second.


11 degrees to the W of M64, sits the large lentinicular galaxy M85.  At +9.1mag and 7.1 x 5.5 arc minutes in angular size, M85 has a bright, compact core, surrounded by a rather uniform ring of stars.  Shining at +9.10 mag it is easy visible, but unlike the Spindle Galaxy, NGC 3115, the lentinicular galaxy we reviewed last month, M85 is presented much more face on and is thus fainter.  However, the two galaxies are similar in their rather elderly stellar population.  M85 was discovered in 1781 by the prolific Pierre Mechain and added to the Messier list by Charles Messier later that year. 


2 and a half degrees to the South of M85 is the fabulous M100 - one of the best Spiral Galaxies in the sky.  Discovered in the same year as M85, by the same man (Mechain), M100 is often described as a "Grand Design Spiral" - a very well defined galaxy with particularly prominent arms.  Of this definition, as far as M100 is concerned, there can be no doubt: at +9.39 mag and 7.5 x 6. arc minutes of size, it is easily within reach of small telescopes and its spiral arms will begin to be glimpsed by small telescopes under good conditions.  Observers will note M100's elongated oval core being surrounded by a fainter halo of stars.  Larger instruments will begin to resolve the finer details of this beautiful galaxy's spiral structure.  M100 is to be found 47 million light years distance from us and has also been noted for its star bursting nature.  Rapid star formation is occurring within the galaxy, with energetic bright blue stars being in abundance.  Though it is not only for star formation that M100 is notable: during the 20th Century, four supernovae were witnessed to take place within the galaxy.  The only supernova of this century to be observed in m100 occurred in 2006.  M100 is one of the jewels of this area of sky and should not be missed.

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