Night sky guide for May 2017

Night sky guide for May 2017

May 2017 brings us Eta Aquarids, an above average meteor shower capable of producing up to 60 meteors per hour at its peak, in the southern hemisphere. The waxing gibbous moon, however, will block out many of the fainter meteors this year.

The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated on May 10. This full moon was known by early Native American tribes as the Full Flower Moon because this was the time of year when spring flowers appeared in abundance.

The Moon will pass close to the Sun on May 25 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.

  • May 1 - C/2015 ER61 (PANSTARRS) reaches its brightest. Comet C/2015 ER61 (PANSTARRS) is forecast to reach its brightest, at around mag 7.1. It will lie at a distance of 1.06 AU from the Sun, and at a distance of 1.20 AU from the Earth.

  • May 3 - Moon at First Quarter - 02:48 UTC. The Moon will be prominent in the evening sky, setting around midnight. 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.

  • May 6, 7 - Eta Aquarids Meteor Shower. The Eta Aquarids is an above average shower, capable of producing up to 60 meteors per hour at its peak. It runs annually from April 19 to May 28. Most of the activity is seen in the Southern Hemisphere. In the Northern Hemisphere, the rate can reach about 30 meteors per hour. It is produced by dust particles left behind by comet Halley, which has known and observed since ancient times. It peaks this year on the night of May 6 and the morning of the May 7. The Moon will be 10 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.

  • May 7 - Conjunction of the Moon and Makemake - 21:22 UTC. The Moon and 136472 Makemake will share the same right ascension, with the Moon passing 27°37' to the south of 136472 Makemake. The Moon will be 11 days old. The Moon will be at mag -12.5 in the constellation Virgo, and 136472 Makemake at mag 17.0 in the neighboring constellation of Coma Berenices.

  • May 8 - Close approach of the Moon and Jupiter - 22:47 UTC. The Moon and Jupiter will make a close approach, passing within 1°59' of each other. The Moon will be at mag -12.5, and Jupiter at mag -2.4, 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.

  • May 8 - Conjunction of Mercury and Uranus - 23:42 UTC. Mercury and Uranus will share the same right ascension, with Mercury passing 2°13' to the south of Uranus. Mercury will be at mag 1.3, and Uranus at mag 5.9, 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.

  • May 8 - Conjunction of Jupiter and Makemake - 11:12 UTC. Jupiter and 136472 Makemake will share the same right ascension, with Jupiter passing 29°43' to the south of 136472 Makemake. Jupiter will be at mag -2.4 in the constellation Virgo, and 136472 Makemake at mag 17.0 in the neighboring constellation of Coma Berenices.

  • May 9 - Conjunction of the Moon and Haumea - 10:34 UTC. The Moon and 136108 Haumea will share the same right ascension, with the Moon passing 25°39' to the south of 136108 Haumea. The Moon will be 13 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.

  • May 10 - Full Moon - 21:44 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. This full moon was known by early Native American tribes as the Full Flower Moon because this was the time of year when spring flowers appeared in abundance. This moon has also been known as the Full Corn Planting Moon and the Milk Moon.

  • May 10 - C/2015 ER61 (PANSTARRS) at perihelion. Comet C/2015 ER61 (PANSTARRS) will make its closest approach to the Sun, at a distance of 1.04 AU.

  • May 11 - M5 well placed for observation. The globular cluster M5 (NGC 5904) in Serpens will be well placed for observation. It will reach its highest point in the sky at around midnight local time. At a declination of +02°04', it is visible across much of the world; it can be seen at latitudes between 72°N and 67°S. At magnitude 5.8, M5 is quite faint, and certainly not visible to the naked eye, but can be viewed through a pair of binoculars or a small telescope.

  • May 12 - Conjunction of Mercury and Eris - 04:56 UTC. Mercury and 136199 Eris will share the same right ascension, with Mercury passing 9°41' to the north of 136199 Eris. Mercury will be at mag 0.8 in the constellation Pisces, and 136199 Eris at mag 18.8 in the neighboring constellation of Cetus.

  • May 13 - α–Scorpiid meteor shower. The α–Scorpiid meteor shower will reach its maximum rate of activity on May 13, but 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. The radiant of the α–Scorpiid meteor shower is at around right ascension 16h50m, declination -24°, 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 17 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.

  • May 14 - Close approach of the Moon and Saturn - 23:11 UTC. The Moon and Saturn will make a close approach, passing within 3°04' of each other. The Moon will be 17 days old. The Moon will be at mag -12.4, 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.

  • May 15 - Conjunction of the Moon and Pluto - 21:03 UTC. The Moon and 134340 Pluto will share the same right ascension, with the Moon passing 2°21' to the north of 134340 Pluto. The Moon will be 19 days old. The Moon will be at mag -12.3, and 134340 Pluto at mag 15.0, 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 through a pair of binoculars.

  • May 18 - Mercury at greatest elongation west - 22:58 UTC. In the southern hemisphere Mercury will be well placed for observation in the dawn sky, shining brightly at mag 0.4. 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.

  • May 19 - Moon at Last Quarter - 00:34 UTC. The Moon will be prominent in the dawn sky, rising at around midnight.

  • May 20 - Close approach of the Moon and Neptune - 05:47 UTC. The Moon, 24 days old, and Neptune will make a close approach, passing within 0°26' of each other. The Moon will be at mag -11.6, 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.

  • May 22 - Conjunction of the Moon and Venus - 12:32 UTC. The Moon and Venus will share the same right ascension, with the Moon passing 2°23' to the south of Venus. At around the same time, the two objects will also make a close approach, technically called an appulse. The Moon will be at mag -10.7 in the constellation Cetus, and Venus at mag -4.4 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.

  • May 22 - Close approach of the Moon and Venus - 13:57 UTC. The Moon and Venus will make a close approach, passing within 2°15' of each other. The Moon will be 26 days old. The Moon will be at mag -10.7, and Venus at mag -4.4, 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.

  • May 23 - Conjunction of the Moon and Eris - 07:10 UTC. The Moon, 27 days old, and 136199 Eris will share the same right ascension, with the Moon passing 8°27' to the north of 136199 Eris. The Moon will be at mag -10.2 in the constellation Pisces, and 136199 Eris at mag 18.8 in the neighboring constellation of Cetus.

  • May 23 - Mercury at dichotomy - 14:35 UTC. In the southern hemisphere Mercury will be well placed for observation in the dawn sky, shining brightly at mag 0.1. 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. Mercury's phase varies depending on its position relative to the Earth. When it passes between the Earth and Sun, for example, the side that is turned towards the Earth is entirely unilluminated, like a new moon. Conversely, when it lies opposite to the Earth in its orbit, passing almost behind the Sun, it appears fully illuminated, like a full moon. However, at this time it is also at its most distant from the Earth, so it is actually fainter than at other times.

  • May 24 - Conjunction of the Moon and Mercury - 01:20 UTC. The Moon and Mercury will share the same right ascension, with the Moon passing 1°36' to the south of Mercury. The Moon will be 28 days old. The Moon will be at mag -9.5 in the constellation Cetus, and Mercury at mag 0.1 in the neighbouring constellation of Aries. 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.

  • May 25 - New Moon - 19:46 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. At 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.

  • Conjunction of the Moon and Ceres - 04:38 UTC. The Moon and 1 Ceres will share the same right ascension, with the Moon passing 3°55' to the south of 1 Ceres. The Moon will be 1 days old. The Moon will be at mag -6.8, and 1 Ceres at mag 8.6, 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.

  • M4 well placed for observation. Across much of the world the globular cluster M4 (NGC 6121) in Scorpius will be well placed for observation. It will reach its highest point in the sky at around midnight local time. At a declination of -26°31', it is easiest to see from the southern hemisphere but cannot be seen from latitudes much north of 43°N. At magnitude 5.9, M4 is quite faint, and certainly not visible to the naked eye, but can be viewed through a pair of binoculars or small telescope.

Video courtesy Hubble Space Telescope

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

Featured image background: Hubble Space Telescope.

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