Night Sky Notes for April 2017 Geoff Mitchell
The April night sky now shows the spring constellations but with daylight saving time (BST) and the Sun moving north of the celestial equator , twilight skies mean later observing hours as we head into the summer months. The spring night sky contains many fine objects to view with both binocular and small telescopes and this month has a few notable events of special interest. The bright planet Jupiter is well placed high in the south by late evening. The red planet Mars is visible in the western twilight below the Seven Sisters star cluster (M45). Look to the west early evening (8pm BST) to see the elusive planet Mercury low in twilight during early April. Telescopes shows a tiny disk, Mercury also has phases (like our Moon). Two comets also feature in the eastern evening sky , a short period comet 41P ( Tuttle-Giacobini-Kresak ) passes within 21 million km of Earth on April 1st prior to reaching perihelion on April 12th , making this apparition one of the most favourable for many returns , The second is comet 2015 V2 Johnson which is due to reach perihelion in June and is visible in binoculars / telescope in the constellation of Hercules . Comet 41P has an apparent size of around 0.5° (same as The Moon), but its low surface brightness makes it difficult to see in light polluted skies.
Galaxy hunting season is now `open` the constellations of Leo and Virgo contain a number of Galaxies. The brighter member galaxies of the Virgo Super cluster, are visible as small, faint misty patches in moderate sized telescopes on moonless clear evenings from a dark observing site. Use the star Vindemiatrix as a starting point, to view the chain of brighter galaxies including M87 which are visible as tiny `smudges`.
Our own Milky Way galaxy stretches from the constellation of Auriga , marked by the bright star Capella overhead through the constellations of Perseus and Cassiopeia and down into the north west . This faint band of stars is best seen on clear dark moonless evenings from darker locations outside the town.
The familiar asterism of the plough in the constellation of Ursa Major, The Great Bear is seen high in the north east with its handle or tail pointing towards the horizon mid evening. Use the right hand pair of stars Dubhe and Merak (The pointers) to find the faint pole star Polaris and the position of North.
The spring constellation of Leo rises early evening, the brightest star Regulus and the `reversed question mark ` shaped star asterism of `The Sickle` makes this an easily recognisable constellation. Leo stretches eastward and is marked at the tail end by the star Denebola. Leo contains some moderately bright galaxy pairs visible in moderate sized telescopes on moonless evenings. M65/M66 and NGC 3628 form the famous galaxy triplet, all three galaxies being visible in the same telescopic field of view.
Jupiter currently in the constellation of Virgo just above the bright star Spica . Jupiter reaches opposition on April 7th but is low in the south as seen from the UK , small telescopes show the four bright moons discovered by Galileo in 1610 and the famous cloud belts. The Great Red Spot is currently more subtle and straw coloured and has been fading recently. Jupiter’s Galilean moons show shadow transits and go into eclipse behind the planet and with the current favourable orbital plane alignment which occurs every six years some moons can eclipse each other as seen from Earth. A 21cm aperture or larger telescope is recommended to see the tiny dark shadow disks of the Galilean moons cast onto the cloud tops of Jupiter turbulent atmosphere.
The galaxy rich constellations of Virgo and Coma Berenices can now be seen rising by mid evening. Mars is located in the constellation of Scorpius, rising low in the south east late evening in late April, opposition is in late May. The `red` planet is easy to spot and is placed near to the head of the Scorpius. From the UK we only get to see the top part of Scorpius, but its still an constellation worth looking at with binoculars. Antares is the brightest star, a red giant star. Just close to Antares, binoculars or telescope show the globular cluster M4.
Saturn positioned low in the constellation of Sagittarius now rises in the early hours in late April, but will be an evening object at opposition in early June. It is however rather low as seen from the UK, but has its ring system wide open, a classic view of this gem of the solar system. Small telescopes will show the rings and the brightest moon Titan. Larger telescopes show up to six or so fainter moons and any white oval features on the planets disk.
Low in the north east Lyra is the radiant for the April Lyrids meteor shower, best seen in the early hours but with a rather low zenith hourly rate (ZHR) of just 18 meteors per hour. Lyra heralds the approach of summer skies.
Planets in April 2017
Mercury is better placed low after sunset in our evening twilight skies early in the month, with greatest elongation on April 1st (19°)
Venus is poorly placed in the dawn skies, reaching maximum brilliance (-4.4m) on April 26th.
Mars is visible low in the west early evening in April showing a tiny (4 arc second) disk telescopically
Jupiter shines brightly low in the east in Virgo early evening reaching opposition on April 12th see www.lutonastrolink.org.uk for details of forthcoming observing evenings)
Saturn now rises by after midnight during April but will be at opposition in early June in our evening skies.
Uranus is placed in our daytime skies – best views in autumn skies.
Neptune is placed in our daytime skies – best seen in autumn skies
Moons phases in April
New Moon April 26th Moonless, best time for deep sky observing and comet observing.
First Quarter April 3rd Best days to see shadow details in lunar craters (early evening)
Full Moon April 11th Best days to see bright ray craters like Copernicus / Tycho.
Last Quarter April 19th Moon visible in daytime skies. Do not look directly at the Sun.
Meteor showers April Lyrids, rather low rates, best in early morning April 18th to 25th.
The Highlights of the Month
- Mercury in twilight evening skies during early April – best seeing conditions April 1st to April 10th .
- April skies, Milky Way visible high overhead on moonless evenings in darker skies.
- Jupiter dominates our late evening skies, cloud belts and four of Jupiter’s moons visible in a small telescope.
- Double cluster, on the Perseus / Cassiopeia border high overhead, nice pair of star clusters.
- Pleiades (Seven Sister’s) star cluster (M45) and Hyades cluster in Taurus (lunar occultation April 10th)
- Beehive cluster (M44) visible to the unaided eye but best seen with binoculars.
- Comet 41P close approach April 1st (see notes) visible in binoculars / telescope in dark skies
- Comet 2015 V2 (Johnson), binocular / telescopic in Hercules low in the east late evening (see notes)
- Telescopic triplet of galaxies M65/M66/NGC3628 in the constellation of Leo
- Virgo cluster of Galaxies, brighter members of the cluster can be seen with small telescopes or binoculars.
- International Dark Skies Week 2017 – Refer to LAS website home page for details.
- ISS Visibility – Early evening / mid evening passes during the first week in April – see web site for link / details.
- 2.8% waxing crescent Moon is visible low in the west after sunset , Earthshine faintly illuminates.
More detailed sky notes and LAS Newsletters, Finder charts are available to LAS members via the Members` page on the LAS Website www.lutonastrolink.org.uk