Night Sky, May 2018: What You Can See This Month [Maps]
The night sky tonight and on any clear night offers an ever-changing display of fascinating objects you can see, from stars and constellations to bright planets, often the moon, and sometimes special events like meteor showers. Observing the night sky can be done with no special equipment, although a sky map can be very useful, and a good beginner telescope or binoculars will enhance some experiences and bring some otherwise invisible objects into view. You can also use astronomy accessories to make your observing easier, and use our Satellite Tracker page powered by N2YO.com to find out when to see the International Space Station and other satellites. Below, find out what’s up in the night sky tonight (Planets Visible Now, Moon Phases, Observing Highlights This Month) plus other resources (Skywatching Terms, Night Sky Observing Tips and Further Reading).
Monthly skywatching information is provided to Space.com by Chris Vaughan of Starry Night Education, the leader in space science curriculum solutions. Follow Starry Night on Twitter @StarryNightEdu.
Editor’s note: If you have an amazing skywatching photo you’d like to share for a possible story or image gallery, please contact managing editor Tariq Malik firstname.lastname@example.org.
Yearly Night Sky Guides:
Calendar of Observing Highlights
Friday, May 4 pre-dawn — Moon Hops over Saturn
In the southwestern pre-dawn sky of Friday, May 4, the waning gibbous moon will be positioned about 6 degrees to the right of Saturn. A half-day later, skywatchers in parts of Asia will see the moon pass only one degree to the north of the ringed planet. On Saturday morning, the moon’s orbit (green line) will carry it to a position to the left of Saturn. Look for the stars forming the large Teapot asterism of Sagittarius below Saturn all year.
Saturday, May 5 pre-dawn — Eta-Aquariid Meteor Shower Peak
The annual Eta Aquariid Meteor Shower, produced by material from Halley’s Comet, runs from Apr 19 to May 26 and peaks before dawn on Sat., May 6. True Aquariids will travel away from a radiant point in Aquarius, near the eastern horizon. Watch for up to a few dozen meteors per hour, including some fireballs, near the peak. The waning last quarter moon will degrade the sky for this shower.
Sunday, May 6 pre-dawn — Moon Meets Mars
In the pre-dawn sky of Sunday, May 6, the last quarter moon will sit 2 degrees above Mars. Both objects will fit into the field of view of binoculars (orange circle). The binocular field will also include the globular cluster Messier 75, which will be positioned 3 degrees to the left of Mars.
Monday, May 7 at 10:09 p.m. EDT — Last Quarter Moon
At its last quarter phase, the moon rises around midnight and remains visible in the southern sky all morning. At this phase, the moon is illuminated on its western side, towards the pre-dawn sun. Last quarter moons are positioned ahead of the Earth in our trip around the sun. About 3½ hours later, Earth will occupy that same location in space. After this phase, the waning moon traverses the last quarter of its orbit around the earth, on the way to new moon.
Tuesday, May 8 midnight to dawn — Vesta Reverses Direction
On Tuesday, May 8, the major asteroid (4) Vesta will cease its regular eastward orbital motion (red path) and begin a retrograde loop that lasts until late summer. At this time, look for the magnitude 5.5 object sitting 6 degrees to the upper right of Saturn.
Tuesday, May 8 evening — Jupiter at Opposition
On Tuesday, May 8 at 9 p.m. EDT, Jupiter will be exactly opposite the sun in the sky, and visible all night long. The planet’s disk will be the brightest and largest for the year. Around opposition, Jupiter and its four large satellites frequently eclipse and occult one another, and the moons cast round black shadows on the planet, as shown here.
Saturday, May 12 before sunrise — Mercury and Uranus Pairing
Just before sunrise on Saturday, May 12, Mercury and much dimmer Uranus will sit only 3 degrees apart, and very low in the eastern sky. Both objects will fit into the field of view of binoculars (orange circle), with Uranus to the upper left of Mercury.
Monday, May 14 pre-dawn — Mars meets Messier 75
In the pre-dawn sky on the morning of Monday, May 14, Mars’ eastward orbital motion (brown line) will carry it to a position only 18 arc-minutes (or 2/3 of the full moon’s diameter) below the small globular star cluster designated Messier 75. Both objects will appear together in the field of view of a high power telescope (yellow circle).
Monday, May 14 pre-dawn — Saturn passes Messier 22
In the pre-dawn southern sky during the mornings surrounding Monday, May 14, Saturn’s retrograde orbital motion westward will carry it past the bright star cluster designated Messier 22, also known as the Sagittarius Cluster. Closest approach of 1.6 degrees occurs around May 14, when Saturn will be positioned directly above the cluster. Both objects will appear together in the field of view of a low power telescope (orange circle) or binoculars.
Tuesday, May 15 at 7:48 a.m. EDT — New Moon
At its new phase, the moon is travelling between Earth and the sun. Since sunlight is only reaching the far side of the moon, and the moon is in the same region of the sky as the sun, the moon will be completely hidden from view. A day or two after new moon, look for the slender sliver of the young crescent moon to re-appear just above the western horizon after sunset.
Thursday, May 17 evening — Venus and the Young Moon
In the northwestern sky during early evening on Thursday, May 17, the young crescent moon will be situated 6 degrees to the left of Venus. The pair of objects will set together about 10:30 p.m. local time. Look for the open star cluster Messier 35 sitting above and between them in the same binocular field of view (orange circle).
Saturday, May 19 late evening — Moon Approaches the Beehive
Low in the western sky during late evening on Saturday, May 19, the waxing crescent moon will be situated about 6 degrees below the large open star cluster in Cancer known as the Beehive. Other names are Praesepe and Messier 44. Binoculars will show both the moon and the cluster in the same field of view (orange circle). Observers in western North America will see the moon move to within 4 degrees of the cluster before moonset.
Sunday, May 20 evening — Venus meets Messier 35
In the northwestern evening sky of Sunday, May 30, Venus’ orbital motion will carry it within a degree to the right of the bright open star cluster designated Messier 35 in Gemini. Both objects will appear together in the field of view of a low power telescope (orange circle) or binoculars.
Monday, May 21 late evening — Moon Skims Regulus
In late evening on Monday, May 21, the first quarter moon will be situated just above Regulus. At magnitude 1.3, it is the brightest star in Leo. Both objects will fit into the field of view of a small telescope at low power (orange circle). By observing the relative positions of the two objects between dusk and moonset several hours later, the moon’s eastward orbital motion will be made apparent. Minimum separation occurs about 11:15 p.m. EDT.
Monday, May 21 at 11:49 p.m. EDT — First Quarter Moon
After the moon has completed the first quarter of its orbit around Earth, the relative positions of the Earth, sun, and moon cause us to see it half illuminated – on its eastern side. A first quarter moon always rises around noon and sets around midnight, so it is also visible in the afternoon daytime sky. The evenings around first quarter are the best times to see the lunar terrain while it is dramatically lit by low-angled sunlight.
Sunday, May 27 all night — Gibbous Moon near Jupiter
In the southeastern sky on the evening of Sunday, May 27, the nearly full moon and Jupiter will be separated by less than 5 degrees. The two objects will cross the sky together during the night, but the moon’s separation from the bright planet will increase as the moon slides eastwards in its orbit.
Tuesday, May 29 at 10:20 a.m. EDT — Full Milk Moon
The May full moon, known as the Full Milk Moon, Full Flower Moon, or Full Corn Planting Moon, always shines in or near the stars of Libra. Full moons always rise in the east as the sun sets, and set in the west at sunrise. Since no shadows are cast by the vertically impinging sunlight on a full moon, all of the brightness differences are generated by the reflectivity, or albedo, of the surface rocks.
Wednesday, May 30 – Saturn and the Moon meet Messiers (late evening)
In late evening on Wednesday, May 31, the waning gibbous moon will rise in the east with Saturn. The moon will sit only two degrees east of the ringed planet and both objects will fit easily within the field of view of binoculars (orange circle). If you place the naked-eye star Kaus Borealis (Lambda Sagittarii) on the lower right edge of the field, the Messier objects M25, M22, and M28 will be in the same field, at upper left, bottom centre, and lower right respectively.
Mercury will open May among the stars of Pisces – just a few days after its greatest western elongation, and still nearly 27 degrees west of the Sun. For observers in the Northern Hemisphere, the elusive planet will be visible with difficulty in the eastern pre-dawn sky. For most of May, the planet will creep northwards through Aries and into Taurus while hugging the horizon. As it swings towards the sun, the increasing tilt of the morning ecliptic will keep it in view by lifting it higher. During this period of time, Mercury will brighten steadily and shrink in apparent diameter while it waxes from a half-illuminated phase to nearly full. The planet will become lost in the sun’s glare by month’s end. The May apparition will be a very good one for Southern Hemisphere observers.
During May, Venus continues a long and very good apparition that lasts into early autumn. Each evening through the month, our extremely bright sister planet will climb the western early evening sky – moving between the horns of Taurus in mid-month and passing into Gemini on May 19th. On May 1st, Venus will set about 10:45 p.m. local time. On May 31st, it will set after 11:30 p.m. local time. Venus will continually brighten throughout May, reaching magnitude -3.94 at month’s end. Meanwhile, its apparent disk size will increase slightly and its illuminated phase will drop slightly, to 88%. After sunset on May 17, a very young crescent moon will be visible sitting six degrees to the left of the planet. On May 20, Venus will pass only a degree to the north of the bright open cluster designated Messier 35. The pair will fit within the field of view of binoculars.
Mars will spend May in the southeastern pre-dawn sky. Its prograde motion will carry it out of the stars of Sagittarius and into Capricornus on May 15th. During the course of May, Earth’s orbital motion will continue to reduce our distance from the Red Planet. As a result, Mars will double in brightness (from visual magnitude -0.38 to -1.2) and its apparent disk diameter will dramatically increase from 11 to 15 arc-seconds. The last quarter moon will sit 2 degrees above Mars on May 6th. On May 14th, Mars will pass only 18 arc-minutes (or 2/3 of the full moon’s diameter) below the small globular star cluster designated Messier 75. Both objects will appear together in the field of view of a high power telescope.
During May, very bright Jupiter (visual magnitude -2.5) will be an all-night target in central Libra, slowly moving westward in a retrograde loop that will last until July. The planet will reach opposition on May 9th, when it will exhibit a large 43.8 arc-second disk and be located 37 light-minutes from Earth. This will also be a fine time to observe Jupiter’s four Galilean moons. In the southern sky on the evening of May 27th, the nearly full moon and Jupiter will be separated by less than 5 degrees. The two objects will cross the sky together during the night, but the moon’s separation from the bright planet will increase as the moon slides eastwards in its orbit. Jupiter will end May sitting less than a degree north of the bright double star Zubenelgenubi.
Saturn will spend May as a medium bright (magnitude 0.35) yellowish object moving retrograde through the northern part of Sagittarius, on the eastern side of the Milky Way. In early May, the ringed planet will rise in the east shortly after midnight and remain visible until dawn, when it will be 23 degrees above the southern horizon. On May 4th, the waning gibbous moon will be positioned about 6 degrees to the right of Saturn. The following morning, the moon will jump to the planet’s left. On the mornings surrounding May 14th, Saturn will move past the bright star cluster designated Messier 22, also known as the Sagittarius Cluster. Closest approach of 1.6 degrees occurs around May 14th, when Saturn will be positioned directly above the cluster. Both objects will appear together in the field of view of a low power telescope or binoculars.
During May, blue-green Uranus will be in the pre-dawn sky among the stars of southwestern Aries, but it will not be observable until late in the month when it will begin to rise in a dark sky, at about 4 a.m. local time.
Blue-tinted Neptune will spend May in the eastern pre-dawn sky among the stars of Aquarius – sitting about 4 degrees to the east of the naked eye star Hydor. As the month wears on, the planet will rise earlier, increasing the window of time for observing it in telescopes before morning twilight.
Gibbous: Used to describe a planet or moon that is more than 50 percent illuminated.
Asterism: A noteworthy or striking pattern of stars within a larger constellation.
Degrees (measuring the sky): The sky is 360 degrees all the way around, which means roughly 180 degrees from horizon to horizon. It’s easy to measure distances between objects: Your fist on an outstretched arm covers about 10 degrees of sky, while a finger covers about one degree.
Visual Magnitude: This is the astronomer’s scale for measuring the brightness of objects in the sky. The dimmest object visible in the night sky under perfectly dark conditions is about magnitude 6.5. Brighter stars are magnitude 2 or 1. The brightest objects get negative numbers. Venus can be as bright as magnitude minus 4.9. The full moon is minus 12.7 and the sun is minus 26.8.
Terminator: The boundary on the moon between sunlight and shadow.
Zenith: The point in the sky directly overhead.
Night Sky Observing Tips
- Adjust to the dark: If you wish to observe faint objects, such as meteors or dim stars, give your eyes at least 15 minutes to adjust to the darkness.
- Light Pollution: Even from a big city, one can see the moon, a handful of bright stars and sometimes the brightest planets. But to fully enjoy the heavens — especially a meteor shower, the constellations, or to see the amazing swath across the sky that represents our view toward the center of the Milky Way Galaxy — rural areas are best for night sky viewing. If you’re stuck in a city or suburban area, a building can be used to block ambient light (or moonlight) to help reveal fainter objects. If you’re in the suburbs, simply turning off outdoor lights can help.
- Prepare for skywatching: If you plan to be out for more than a few minutes, and it’s not a warm summer evening, dress warmer than you think necessary. An hour of observing a winter meteor shower can chill you to the bone. A blanket or lounge chair will prove much more comfortable than standing or sitting in a chair and craning your neck to see overhead.
- Daytime skywatching: When Venus is visible (that is, not in front of or behind the sun) it can often be spotted during the day. But you’ll need to know where to look. A sky map is helpful. When the sun has large sunspots, they can be seen without a telescope. However, it’s unsafe to look at the sun without protective eyewear. See our video on how to safely observe the sun, or our safe sunwatching infographic.