Night sky guide for April 2017

Night sky guide for April 2017

April brings us three meteor showers - Virginids on April 12th, Lyrids on the 22nd and 23rd and Alpha Schorpiids on the 28th. The Moon will present minimal interference for Lyrids and Alpha Scorpiids.

On April 1, Comet 41P/Tuttle-Giacobini-Kresák is making its closest flyby of Earth since its discovery in 1858. It is expected to reach its brightest on April 4 and make the closest approach to the Sun on the 12th, passing at a distance of 1.05 AU.

Jupiter will be at its closest approach to Earth and its face will be fully illuminated by the Sun on April 7. It will be brighter than any other time of the year and will be visible all night long. This is the best time to view and photograph Jupiter and its moons. 

This month's Full Moon is on April 11. At the exact moment when the Moon reaches full phase - 06:10 UTC, it will lie at a declination of -04°43' in the constellation Virgo, and so will appear high in the sky at all but the most extreme latitudes.

The Moon will be located on the same side of the Earth as the Sun and will not be visible in the night sky - New Moon - on April 26. 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. Over 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.

April is Global Astronomy Month (GAM). Organized each April by Astronomers Without Borders, GAM is the largest global celebration of astronomy and features activities that are open to all. Every year GAM brings new ideas and new opportunities, bringing enthusiasts together worldwide to celebrate Astronomers Without Borders' motto 'One People, One Sky.'

  • April 1 - Comet 41P/Tuttle-Giacobini-Kresák makes closest flyby since discovery. Comet 41P/Tuttle-Giacobini-Kresák will make a close approach to our planet on April 1, passing at a safe distance of 0.142 AU / 55.4 LD (21 200 000 km / 13 200 000 miles) from the Earth. This will be its closest flyby of Earth since its discovery in 1858. 41P/Tuttle–Giacobini–Kresák is a periodic comet, a member of the Jupiter family of comets, discovered on May 3, 1858 by an American astronomer Horace Parnell Tuttle. Its nucleus is estimated to be some 1.4 km (0.86 miles) in diameter and it orbits the Sun every ~5.4 years. The comet was recovered on November 10, 2016 at apparent magnitude 21 by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) in Hawaii.

  • April 1 - 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 magnitude 8.3, 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 1 - Mercury at greatest elongation east - 05:52 UTC. Mercury will be well placed for observation in the evening sky, shining brightly at mag -0.2.  Mercury's orbit lies closer to the Sun than the Earth's, meaning that it always appears close to the Sun and is very difficult to observe most of the time. It is observable only for a few days each time it reaches greatest separation from the Sun – moments referred to as greatest elongation. These apparitions take place alternately in the morning and evening skies, depending whether Mercury lies to the east of the Sun or to the west. When it lies to the east, it rises and sets a short time after the Sun and is visible in early evening twilight. When it lies to the west of the Sun, it rises and sets a short time before the Sun and is visible shortly before sunrise. On this occasion, it lies 18° to the Sun's east. This is the best time to view Mercury since it will be at its highest point above the horizon in the evening sky. Look for the planet low in the western sky just after sunset.

  • April 3 - Moon at First Quarter - 18:41 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 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.

  • April 4 - 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 4 - NGC 4755 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°19', 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 4 - Comet 41P/Tuttle-Giacobini-Kresák reaches its brightest. Comet 41P/Tuttle-Giacobini-Kresák is forecast to reach its brightest, at around mag 8.0. It will lie at a distance of 1.06 AU from the Sun, and at a distance of 0.14 AU from the Earth.

  • April 7 - Jupiter at opposition - 21:28 UTC. The giant planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. It will be brighter than any other time of the year and will be visible all night long. This is the best time to view and photograph Jupiter and its moons. A medium-sized telescope should be able to show you some of the details in Jupiter's cloud bands. A good pair of binoculars should allow you to see Jupiter's four largest moons, appearing as bright dots on either side of the planet. Over the weeks following its opposition, Jupiter will reach its highest point in the sky four minutes earlier each night, gradually receding from the pre-dawn morning sky while remaining visible in the evening sky for a few months.

Video courtesy NASA/JPL

  • April 10 - Conjunction of the Moon and Makemake - 16:16 UTC. The Moon and 136472 Makemake will share the same right ascension, with the Moon passing 27°48' to the south of 136472 Makemake. The Moon will be 13 days old. The Moon will be at mag -12.6 in the constellation Virgo, and 136472 Makemake at mag 17.0 in the neighboring constellation of Coma Berenices.

  • April 11 - Close approach of the Moon and Jupiter - 22:43 UTC. The Moon and Jupiter will make a close approach, passing within 2°03' of each other. The Moon will be 13 days old. The Moon will be at mag -12.6, and Jupiter at mag -2.5, both in the constellation Virgo. 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 11 - Full Moon - 06:10 UTC. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. At the exact moment when the Moon reaches full phase, it will lie at a declination of -04°43' 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 75°N and 84°S. Its distance from the Earth will be 398 000 km (247 305 miles). This full moon was known by early Native American tribes as the Full Pink Moon because it marked the appearance of the moss pink, or wild ground phlox, which is one of the first spring flowers. This moon has also been known as the Sprouting Grass Moon, the Growing Moon, and the Egg Moon. Many coastal tribes called it the Full Fish Moon because this was the time that the shad swam upstream to spawn.

  • April 12 - Virginid meteor shower. The Virginid meteor shower will reach its maximum rate of activity on April 12, 2017, but ome shooting stars associated with the shower are expected to be visible each night from April 7 to 18. The maximum rate of meteors expected to be visible is around 5 per hour (ZHR). However, this assumes a perfectly dark sky and that the radiant of the meteor shower is directly overhead. In practice, the number of meteors you are likely to see is lower than this. The radiant of the Virginid meteor shower is at around right ascension 14h00m, declination -09°, as shown by the green cross on the planetarium above. All of the meteors will appear to be traveling directly outward from this point, as indicated by the white lines drawn above. The Moon will be 15 days old at the time of peak activity, and being so close to Full Moon will severely limit the observations that will be possible. To see the most meteors, the best place to look is not directly at the radiant itself, but at any dark patch of sky which is around 30–40° away from it. It is at a distance of around this distance from the radiant that meteors will show reasonably long trails without being too spread out.

  • April 12 - Comet 41P/Tuttle-Giacobini-Kresák at perihelion. Comet 41P/Tuttle-Giacobini-Kresák will make its closest approach to the Sun, at a distance of 1.05 AU.

  • April 12 - Conjunction of the Moon and Haumea - 05:09 UTC. The Moon and 136108 Haumea will share the same right ascension, with the Moon passing 25°40' to the south of 136108 Haumea. The Moon will be 15 days old. The Moon will be at mag -12.5 in the constellation Virgo, and 136108 Haumea at mag 17.3 in the neighboring constellation of Bootes.

  • April 12 - Conjunction of Mars and Ceres - 17:21 UTC. Mars and 1 Ceres will share the same right ascension, with Mars passing 2°58' to the north of 1 Ceres. Mars will be at mag 1.5, and 1 Ceres at mag 9.0, both in the constellation Taurus. 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 13 - Eris at solar conjunction - 22:12 UTC. 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 closest approach, 136199 Eris will appear at a separation of only 12° 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 97.18 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 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 13 - 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 small telescope.

  • April 13 - 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 small telescope.

  • April 13 - Haumea at opposition - 10:27 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 at 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 43.34 times that of the Earth, and so its angular size does not vary much as it cycles between opposition and solar conjunction. On this occasion, 136108 Haumea will lie at a distance of 49.70 AU, and reach a peak brightness of magnitude 17.3. Even at its closest approach to the Earth, however, 136108 Haumea is so distant from the Earth that it is not possible to distinguish it as more than a star-like point of light.

  • April 14 - 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°12', 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 small telescope.

  • April 14 - Uranus at solar conjunction - 05:33 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 closest approach, Uranus will appear at a separation of only 0°33' 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 20.93 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 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 15 - 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°52', it is easiest to see from the southern hemisphere but cannot be seen from latitudes much north of 40°N. At magnitude 7.6, 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 - Close approach of the Moon and Saturn - 18:42 UTC. The Moon and Saturn will make a close approach, passing within 3°13' of each other. The Moon will be 19 days old. The Moon will be at mag -12.2, and Saturn at mag 0.1, 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 17 - 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. At magnitude 6.4, M3 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 18 - Conjunction of the Moon and Pluto - 14:40 UTC. 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. At magnitude 6.4, M3 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 19 - Moon at Last Quarter - 09:58 UTC. The Moon will be prominent in the dawn sky, rising at around midnight. Over coming days, the Moon will rise later each day, so that it is visible for less time before sunrise and it less far above the eastern horizon before dawn. By the time it reaches New Moon, it will rise at around dawn and set at around dusk, making it visible only during the daytime.

  • April 20 - Mercury at inferior solar conjunction - 05:48 UTC. Mercury will pass very close to the Sun in the sky as its orbit carries it between the Sun and Earth. This occurs once in every synodic cycle of the planet (116 days), and marks the end of Mercury's apparition in the evening sky and its transition to become a morning object over the next few weeks. At closest approach, Mercury will appear at a separation of only 1°38' from the Sun, making it totally unobservable for several weeks while it is lost in the Sun's glare. Mercury will also pass perigee – the time when it is closest to the Earth – at around the same time, since it will lie on exactly the same side of the Sun as the Earth in the Solar System. It will move to within a distance of 0.57 AU from the Earth, making it appear with its largest angular size. If it could be observed, it would measure 11.7 arcsec in diameter, whilst appearing completely unilluminated.

  • April 22 - 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°21', it is easiest to see from the northern hemisphere but cannot be seen from latitudes much south of 15°S. At magnitude 7.7, 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 22 - Close approach of the Moon and Neptune - 19:57 UTC. The Moon and Neptune will make a close approach, passing within 0°11' of each other. The Moon will be 25 days old. The Moon will be at mag -10.8, and Neptune at mag 7.9, both in the constellation Aquarius. The pair will be close enough to fit within the field of view of a telescope, but will also be visible through a pair of binoculars.

  • April 22 / 23 - Lyrid meteor shower. The Lyrid meteor shower will reach its maximum rate of activity on April 22 and 23, 2017, but some shooting stars associated with the shower are expected to be visible each night from April 19 to 25. The maximum rate of meteors expected to be visible is around 10 per hour (ZHR). However, this assumes a perfectly dark sky and that the radiant of the meteor shower is directly overhead. In practice, the number of meteors you are likely to see is lower than this. The radiant of the Lyrid meteor shower is at around right ascension 18h10m, declination +32°, as shown by the green cross on the planetarium above. All of the meteors will appear to be traveling directly outward from this point, as indicated by the white lines drawn above. The Moon will be 26 days old at the time of peak activity, presenting minimal interference. To see the most meteors, the best place to look is not directly at the radiant itself, but at any dark patch of sky which is around 30–40° away from it. It is at a distance of around this distance from the radiant that meteors will show reasonably long trails without being too spread out.

  • April 23 - Conjunction of Mercury and Eris - 01:28 UTC. Mercury and 136199 Eris will share the same right ascension, with Mercury passing 13°58' to the north of 136199 Eris. Mercury will be at mag 5.5 in the constellation Pisces, and 136199 Eris at mag 18.8 in the neighboring constellation of Cetus.

  • April 23 - Conjunction of the Moon and Venus - 18:00 UTC. The Moon and Venus will share the same right ascension, with the Moon passing 5°10' to the south of Venus. The Moon will be 26 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 -10.3 in the constellation Aquarius, and Venus at mag -4.5 in the neighboring constellation of Pisces. 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 23 - Close approach of the Moon and Venus - 21:01 UTC. The Moon and Venus will make a close approach, passing within 4°52' of each other. The Moon will be 26 days old. The Moon will be at mag -10.2, and Venus at mag -4.5, both in the constellation 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. At around the same time, the two objects will also share the same right ascension – called a conjunction.

  • April 25 - Conjunction of the Moon and Mercury - 17:57 UTC. The Moon and Mercury will share the same right ascension, with the Moon passing 4°30' to the south of Mercury. The Moon will be 28 days old. The Moon will be at mag -7.8, and Mercury at mag 4.2, both in the constellation Pisces. 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 25 - Conjunction of the Moon and Eris - 20:15 UTC. The Moon and 136199 Eris will share the same right ascension, with the Moon passing 8°34' to the north of 136199 Eris. The Moon will be 28 days old. The Moon will be at mag -7.5 in the constellation Pisces, and 136199 Eris at mag 18.8 in the neighboring constellation of Cetus.

  • April 26 - New Moon - 12:17 UTC. The Moon will be located on the same side of the Earth as the Sun and will not be visible in the night sky. 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. Over 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 first quarter, in a week's time, it will be visible until around midnight.

  • April 26 - Venus at greatest brightness - 18:36 UTC. Venus will be well placed for observation in the dawn sky, shining brightly at mag -4.5. Venus's orbit lies closer to the Sun than the Earth's, meaning that it always appears close to the Sun and is very difficult to observe most of the time. It is observable only for a few weeks each time it reaches greatest separation from the Sun – moments referred to as greatest elongation. On these occasions, however, Venus is so bright and conspicuous that it becomes the third brightest object in the sky after the Sun and Moon. It is often called the morning or evening star.

  • April 28 - Conjunction of the Moon and Ceres - 23:30 UTC. The Moon and 1 Ceres will share the same right ascension, with the Moon passing 3°14' to the south of 1 Ceres. The Moon will be 1 days old. The Moon will be at mag -9.1, and 1 Ceres at mag 8.9, both in the constellation Taurus. 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 28 - Alpha Scorpiid meteor shower. The α–Scorpiid meteor shower will reach its maximum rate of activity on April 28, 2017. Some shooting stars associated with the shower are expected to be visible each night from April 20 to May 19. The maximum rate of meteors expected to be visible is around 5 per hour (ZHR). However, this assumes a perfectly dark sky and that the radiant of the meteor shower is directly overhead. In practice, the number of meteors you are likely to see is lower than this. The Moon will be 2 days old at the time of peak activity, presenting minimal interference. To see the most meteors, the best place to look is not directly at the radiant itself, but at any dark patch of sky which is around 30–40° away from it. It is at a distance of around this distance from the radiant that meteors will show reasonably long trails without being too spread out.

  • April 28 - Conjunction of Mercury and Uranus - 17.17 UTC. Mercury and Uranus will share the same right ascension, with Mercury passing 0°08' to the south of Uranus. Mercury will be at mag 3.2, and Uranus at mag 5.9, both in the constellation Pisces. The pair will be close enough to fit within the field of view of a telescope, but will also be visible through a pair of binoculars.

  • April 29 - International Astronomy Day. Astronomy Day is an annual event intended to provide a means of interaction between the general public and various astronomy enthusiasts, groups and professionals. The theme of Astronomy Day is "Bringing Astronomy to the People," and on this day astronomy and stargazing clubs and other organizations around the world will plan special events. You can find out about special local events by contacting your local astronomy club or planetarium.

Video courtesy Hubble Space Telescope

Sources: InTheSky by Dominic Ford, NASA, SeaSky, TW archive

Featured image: The Eta Carinae Nebula (NGC 3372). The Carina Nebula (also known as the Great Nebula in Carina, the Eta Carinae Nebula, NGC 3372, as well as the Grand Nebula) is a large complex area of bright and dark nebulosity in the constellation of Carina, and is located in the Carina–Sagittarius Arm. The nebula lies at an estimated distance between 6,500 and 10,000 light years from Earth. The nebula is one of the largest diffuse nebulae in our skies. Although it is some four times as large and even brighter than the famous Orion Nebula, the Carina Nebula is much less well known, due to its location in the southern sky. It was discovered by Nicolas Louis de Lacaille in 1751–52 from the Cape of Good Hope. Image credit: Damian Peach

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