Night Sky Guide for April 2020

Night Sky Guide for April 2020

April 1 - Moon at First Quarter - 10:21 UTC. The Moon will be prominent in the evening sky. At this time in its monthly cycle of phases, it appears almost exactly half illuminated.

April 2 - M104 well placed for observation. The sombrero galaxy (M104, NGC 4594) will be well placed for observation. It will reach its highest point in the sky at around midnight local time. At a declination of -11°37', it is easiest to see from the southern hemisphere; it can be seen at latitudes between 58°N and 81°S. At magnitude 8.0, M104 is quite faint, and certainly not visible to the naked eye, but can be viewed through a pair of binoculars or a small telescope.

April 3 - Asteroid 3 Juno at opposition - 02:22 UTC. Asteroid 3 Juno will be well placed for observation, lying in the constellation Virgo, well above the horizon for much of the night. Regardless of your location on the Earth, 3 Juno will reach its highest point in the sky around midnight local time. This optimal positioning occurs when it makes its closest approach to the point in the sky directly opposite to the Sun – an event termed opposition. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is highest in the sky at the same time. At around the same time that 3 Juno passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest in the night sky. This happens because when 3 Juno lies opposite to the Sun in the night sky, the solar system is lined up so that 3 Juno, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as 3 Juno. On this occasion, 3 Juno will pass within 2.06 AU of us, reaching a peak brightness of magnitude 9.7. Nonetheless, even at its brightest, 3 Juno is a faint object beyond the reach of the naked eye; binoculars or a telescope of moderate aperture are needed.

April 3 - Conjunction of Mercury and Neptune - 15:17 UTC. Mercury and Neptune will share the same right ascension, with Mercury passing 1°24' to the south of Neptune. Mercury will be at mag -0.0, and Neptune at mag 8.0, both in the constellation Aquarius. The pair will be too widely separated to fit within the field of view of a telescope but will be visible through a pair of binoculars.

April 4 - Close approach of Venus and M45 - 00:53 UTC. Venus and M45 will make a close approach, passing within 0°15' of each other. Venus will be at mag -4.4, and M45 at mag 1.3. Both objects will lie in the constellation Taurus. They will be close enough to fit within the field of view of a telescope, but will also be visible to the naked eye or through a pair of binoculars.

April 5 - M94 well placed for observation. M94, a spiral galaxy in Canes Venatici will be well placed for observation. It will reach its highest point in the sky at around midnight local time. At a declination of +41°07', it is easiest to see from the northern hemisphere but cannot be seen from latitudes much south of 28°S. At magnitude 8.2, M94 is quite faint, and certainly not visible to the naked eye, but can be viewed through a pair of binoculars or a small telescope.

April 5 - NGC 4655 well placed for observation. Across much of the world, the jewel box open star cluster (NGC 4755, also known as the Kappa Crucis cluster) in Crux will be well placed for observation. It will reach its highest point in the sky at around midnight local time. At a declination of -60°21', it is easiest to see from the southern hemisphere but cannot be seen from latitudes much north of 9°N. At magnitude 4.2, NGC4755 is tricky to make out with the naked eye except from a dark site but is visible through a pair of binoculars or a small telescope.

April 8 - Full Moon - 02:35 UTC. The Moon will reach full phase on April 8. At this time in its monthly cycle of phases, the Moon lies almost directly opposite the Sun in the sky, placing it high above the horizon for much of the night. This month's full moon will take place unusually close to the time of the month when the Moon also makes its closest approach to the Earth – called its perigee. This means the moon will appear slightly larger and brighter than at other times, though any difference is imperceptible to the unaided eye. Perigee full moons such as this occur roughly once every 13 months. The sequence of full moons through the year are often assigned names according to the seasons in which they fall. This month's will be the first to fall in spring 2020 – the Egg Moon. Over the nights following April 8, the Moon will rise around an hour later each day, becoming prominent later in the night. Within a few days, it will only be visible in the pre-dawn and early-morning sky. By the time it reaches the last quarter, a week after the full moon, it will rise at around midnight and set at around noon. At the exact moment when the Moon reaches full phase, it will lie at a declination of -02°46' in the constellation Virgo, and so will appear high in the sky at all but the most extreme latitudes. It will be visible at all latitudes between 77°N and 82°S. Its distance from the Earth will be 357 000 km (221 800 miles).

April 9 - Conjunction of Jupiter and Pluto - 07:02 UTC. Jupiter and 134340 Pluto will share the same right ascension, with Jupiter passing 0°44' to the north of 134340 Pluto. Jupiter will be at mag -2.2, and 134340 Pluto at mag 15.1, both in the constellation Sagittarius. The pair will be a little too widely separated to fit comfortably within the field of view of a telescope but will be visible through a pair of binoculars.

April 13 - Eris at solar conjunction. 136199 Eris will pass very close to the Sun in the sky as its orbit carries it around the far side of the solar system from the Earth. At the closest approach, 136199 Eris will appear at a separation of only 11° from the Sun, making it totally unobservable for several weeks while it is lost in the Sun's glare. At around the same time, 136199 Eris will also be at its most distant from the Earth – receding to a distance of 96.97 AU – since the two planets will lie on opposite sides of the solar system. If 136199 Eris could be observed at this time, it would appear at its smallest and faintest on account of its large distance. It would measure 0.0 arcsec in diameter. Over the following weeks and months, 136199 Eris will re-emerge to the west of the Sun, gradually becoming visible for ever-longer periods in the pre-dawn sky. After around six months, it will reach opposition, when it will be visible for virtually the whole night.

April 14 - NGC 5128 well placed for observation. Across much of the world, Centaurus A (NGC 5128) will be well placed for observation. It will reach its highest point in the sky at around midnight local time. At a declination of -43°01', it is easiest to see from the southern hemisphere but cannot be seen from latitudes much north of 26°N. At magnitude 7.0, NGC5128 is quite faint, and certainly not visible to the naked eye, but can be viewed through a pair of binoculars or a small telescope.

April 14 - Omega-Cen well placed for observation. Across much of the world the brightest globular cluster in the sky, Omega Centauri will be well placed for observation. It will reach its highest point in the sky at around midnight local time. At a declination of -47°28', it is easiest to see from the southern hemisphere but cannot be seen from latitudes much north of 22°N. At magnitude 3.7, Omega-Cen is tricky to make out with the naked eye except from a dark site but is visible through a pair of binoculars or a small telescope.

April 15 - Moon at Last Quarter - 22:56 UTC. The Moon will be prominent in the dawn sky, rising at around midnight.

April 15 - Conjunction of the Moon and Jupiter - 23:05 UTC. The Moon and Jupiter will share the same right ascension, with the Moon passing 1°59' to the south of Jupiter. The Moon will be 21 days old. At around the same time, the two objects will also make a close approach, technically called an appulse. The Moon will be at mag -11.9, and Jupiter at mag -2.3, both in the constellation Sagittarius. The pair will be too widely separated to fit within the field of view of a telescope but will be visible to the naked eye or through a pair of binoculars.

April 15 - Close approach of the Moon, Jupiter, and Pluto - 23:29 UTC. The Moon, Jupiter, and 134340 Pluto will make a close approach, passing within 1°59' of each other. The Moon will be at mag -11.9; Jupiter will be at mag -2.3, and 134340 Pluto will be at mag 15.1. The trio will lie in the constellation of Sagittarius. They will be too widely separated to fit within the field of view of a telescope but will be visible to the naked eye or through a pair of binoculars. At around the same time, the trio will also share the same right ascension – called conjunction.

April 15 - M51 well placed for observation. The whirlpool galaxy (M51, NGC 5194) will be well placed for observation. It will reach its highest point in the sky at around midnight local time. At a declination of +47°11', it is easiest to see from the northern hemisphere but cannot be seen from latitudes much south of 22°S. At magnitude 8.4, M51 is quite faint, and certainly not visible to the naked eye, but can be viewed through a pair of binoculars or a small telescope.

April 15 - Conjunction of the Moon and Saturn - 09:18 UTC. The Moon and Saturn will share the same right ascension, with the Moon passing 2°27' to the south of Saturn. The Moon will be 22 days old. At around the same time, the two objects will also make a close approach, technically called an appulse. The Moon will be at mag -11.7, and Saturn at mag 0.4, both in the constellation Capricornus. The pair will be too widely separated to fit within the field of view of a telescope but will be visible to the naked eye or through a pair of binoculars.

April 15 - Close approach of the Moon and Saturn - 09:59 UTC. The Moon and Saturn will make a close approach, passing within 2°26' of each other. The Moon will be at mag -11.7, and Saturn will be at mag 0.4. Both objects will lie in the constellation Capricornus. They will be too widely separated to fit within the field of view of a telescope but will be visible to the naked eye or through a pair of binoculars. At around the same time, the pair will also share the same right ascension – called conjunction.

April 16 - M83 well placed for observation. Across much of the world the southern pinwheel galaxy (M83, NGC 5236), a face-on spiral galaxy in Hydra will be well placed for observation. It will reach its highest point in the sky at around midnight local time. At a declination of -29°51', it is easiest to see from the southern hemisphere but cannot be seen from latitudes much north of 40°N. At magnitude 7.5, M83 is quite faint, and certainly not visible to the naked eye, but can be viewed through a pair of binoculars or a small telescope.

April 16 - Conjunction of the Moon and Mars - 04:33 UTC. The Moon and Mars will share the same right ascension, with the Moon passing 2°00' to the south of Mars. The Moon will be 23 days old. At around the same time, the two objects will also make a close approach, technically called an appulse. The Moon will be at mag -11.5, and Mars at mag 0.6, both in the constellation Capricornus. The pair will be too widely separated to fit within the field of view of a telescope but will be visible to the naked eye or through a pair of binoculars.

April 16 - Close approach of the Moon and Mars - 05:25 UTC. The Moon and Mars will make a close approach, passing within 1°57' of each other. The Moon will be 23 days old. The Moon will be at mag -11.5, and Mars will be at mag 0.6. Both objects will lie in the constellation Capricornus. They will be too widely separated to fit within the field of view of a telescope but will be visible to the naked eye or through a pair of binoculars. At around the same time, the pair will also share the same right ascension – called conjunction.

April 16 - Haumea at opposition - 16:01 UTC. 136108 Haumea will be well placed for observation, in the constellation Bootes. It will be visible for much of the night, reaching its highest point in the sky around midnight local time. This optimal positioning occurs when 136108 Haumea is almost directly opposite the Sun in the sky. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is highest in the sky at the same time. At around the same time that 136108 Haumea passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest and largest. This happens because when 136108 Haumea lies opposite the Sun in the sky, the solar system is lined up so that 136108 Haumea, the Earth and the Sun form a straight line with the Earth in the middle, on the same side of the Sun as 136108 Haumea. In practice, however, 136108 Haumea orbits much further out in the solar system than the Earth – at an average distance from the Sun of 43.21 times that of the Earth, and so its angular size does not vary much as it cycles between opposition and solar conjunction.

April 18 - M3 well placed for observation. The globular cluster M3 (NGC 5272) in Canes Venatici will be well placed for observation. It will reach its highest point in the sky at around midnight local time. At a declination of +28°22', it is easiest to see from the northern hemisphere but cannot be seen from latitudes much south of 41°S.

April 21 - Conjunction of the Moon and Mercury - 17:17 UTC. The Moon and Mercury will share the same right ascension, with the Moon passing 3°06' to the south of Mercury. The Moon will be 28 days old. The Moon will be at mag -8.2 in the constellation Cetus and Mercury at mag -0.8 in the neighboring constellation of Pisces. The pair will be too widely separated to fit within the field of view of a telescope but will be visible to the naked eye or through a pair of binoculars.

April 22 - Lyrid Meteor Shower. The Lyrid meteor shower will be active from April 16 to 25, producing its peak rate of meteors around April 22. Over this period, there will be a chance of seeing Lyrid meteors whenever the shower's radiant point – in the constellation Hercules – is above the horizon. The shower is expected to reach peak activity at around 07:00 UTC on April 22, and so the best displays might be seen before dawn.

April 23 - M101 well placed for observation. The pinwheel galaxy (M101, NGC 5457) will be well placed for observation. It will reach its highest point in the sky at around midnight local time. At a declination of +54°20', it is easiest to see from the northern hemisphere but cannot be seen from latitudes much south of 15°S. At magnitude 7.9, M101 is quite faint, and certainly not visible to the naked eye, but can be viewed through a pair of binoculars or a small telescope.

April 23 - New Moon - 02:26 UTC. The Moon will pass close to the Sun and become lost in the Sun's glare for a few days. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere. The Moon's orbital motion carries it around the Earth once every four weeks, and as a result, its phases cycle from the new moon, through the first quarter, full moon and last quarter, back to new moon once every 29.5 days. This motion also means that the Moon travels more than 12° across the sky from one night to the next, causing it to rise and set nearly an hour later each day. At the new moon, the Earth, Moon, and Sun all lie in a roughly straight line, with the Moon in the middle, appearing in front of the Sun's glare. In this configuration, we see almost exactly the opposite half of the Moon to that which is illuminated by the Sun, making it doubly unobservable because the side we see is unilluminated. Over the coming days, the Moon will rise and set an hour later each day, becoming visible in the late afternoon and dusk sky as a waxing crescent which sets soon after the Sun. By the first quarter, in a week's time, it will be visible until around midnight.

April 23 - π-Puppid meteor shower. The π-Puppid meteor shower will be active from April 15 to 28, producing its peak rate of meteors around April 23. Over this period, there will be a chance of seeing π-Puppid meteors from anywhere where the shower's radiant point – in the constellation Puppis – is above the horizon.

April 26 - Uranus at solar conjunction - 09:02 UTC. Uranus will pass very close to the Sun in the sky as its orbit carries it around the far side of the solar system from the Earth. At the closest approach, Uranus will appear at a separation of only 0°26' from the Sun, making it totally unobservable for several weeks while it is lost in the Sun's glare. At around the same time, Uranus will also be at its most distant from the Earth – receding to a distance of 20.81 AU – since the two planets will lie on opposite sides of the solar system. If Uranus could be observed at this time, it would appear at its smallest and faintest on account of its large distance. It would measure 3.4 arcsec in diameter. Over the following weeks and months, Uranus will re-emerge to the west of the Sun, gradually becoming visible for ever-longer periods in the pre-dawn sky. After around six months, it will reach opposition, when it will be visible for virtually the whole night.

April 26 - Conjunction of the Moon and Venus - 15:23 UTC. The Moon and Venus will share the same right ascension, with the Moon passing 6°03' to the south of Venus. The Moon will be 3 days old. The Moon will be at mag -10.2, and Venus at mag -4.5, both in the constellation Taurus. The pair will be too widely separated to fit within the field of view of a telescope or pair of binoculars but will be visible to the naked eye.

April 28 - Venus at greatest brightness - 14:24 UTC. Venus will reach its greatest brightness in its 2019–2020 evening apparition. It will be shining brightly at mag -4.5.

April 30 - Moon at First Quarter - 20:38 UTC. The Moon will be prominent in the evening sky, setting around midnight. At this time in its monthly cycle of phases, it appears almost exactly half illuminated. Over the coming days, the Moon will set later each day, becoming visible for more of the night. Within a few days, it will not make it very far above the eastern horizon before nightfall. By the time it reaches full phase, it will be visible for much of the night, rising at around dusk and setting at around dawn.

Video courtesy Hubble Space Telescope

Sources: In The Sky by Dominic Ford, NASA

Featured image credit: Hubble Space Telescope

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