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Night Sky Guides:
Calendar of observing highlights
Sunday, May 1 – Venus Kisses Jupiter (before sunrise)
As May begins, the rapid sunward swing of Venus will be carrying it past Jupiter in a very close conjunction, visible in the eastern sky before sunrise. The two planets will be close enough to share the view in binoculars until May 6. During their close approach on Sunday, May 1, Venus and Jupiter will appear together in the eyepiece of a backyard telescope (inset), where six times brighter Venus will exhibit a 68%-illuminated disk, and Jupiter will be accompanied by its four Galilean moons. The two planets will rise by about 4:30 a.m. in your local time zone, and then remain visible until the sky brightens enough to hide them about 90 minutes later. Observers at lower latitudes will see the pair of planets shining higher and in a darker sky.
Sunday, May 1 – Mercury Passes the Pleiades (after dusk)
On Sunday, May 1, look low in the western sky after dusk to see Mercury shining just to the left of the bright Pleiades star cluster, also known as Messier 45 and the Seven Sisters, in Taurus. Binoculars (green circle) will work well to see their meet-up. The cluster’s stars will become more easily visible as the sky darkens towards 9 p.m. By that time, however, you’ll be viewing them less clearly, through a greater thickness of Earth’s atmosphere. Mercury will stay near the cluster for several evenings beyond Sunday.
Monday, May 2 – Young Moon near Mercury (after dusk)
On Monday, May 2, the freshly-minted young crescent moon will shine above the west-northwestern horizon after sunset. The bright, magnitude 0.75 dot of Mercury will shine four finger widths to the moon’s lower right (or 4 degrees to the celestial northwest) – close enough to share the view in binoculars (green circle). Keep an eye out for the Pleiades star cluster positioned just to Mercury’s lower right.
Wednesday, May 4 – Moon Meets Messier 35 (evening)
In the western sky after dusk on Wednesday evening, May 4, the waxing crescent moon will shine several finger widths to the right (or 3 degrees to the celestial northwest) of the large open star cluster in Gemini known as Messier 35 (or the Shoe-Buckle Cluster and NGC 2168). For observers west of the Eastern Time Zone the moon will appear a little closer to the cluster. The moon and Messier 35 will share the view in binoculars (green circle). To better see the cluster, which is almost as wide as the moon, hide the moon just beyond the right side of your binoculars field of view. The medium-bright stars Tejat Posterior and Tejat Prior (Mu and Nu Geminorum, respectively) form Castor’s toes. They can help you find the cluster even when the moon has moved away.
Friday, May 6 – Eta-Aquariids Meteor Shower Peak (pre-dawn)
The annual Eta-Aquariids Meteor Shower is produced by particles of material left behind by repeated passages of Halley’s Comet. The shower, which runs from April 19 to May 28, will peak in intensity before dawn on Friday, May 6, when up to a few dozen meteors per hour are predicted to appear, including some fireballs. Skywatchers can also watch for meteors starting after dusk on Thursday evening, but a 23%-illuminated moon will hide the fainter streaks until it sets around midnight. Eta-Aquariids meteors will appear to be travelling away from a radiant point in Aquarius, which will rise above the southeastern horizon after 2:30 a.m. local time. This year, the planets Jupiter, Mars, and Saturn will be positioned below the radiant. This shower is better for observers at low latitudes.
Saturday, May 7 – Bright Moon Buzzes the Beehive (evening)
On Saturday night, May 7, the easterly orbital motion of the waxing gibbous moon will carry past the huge open star cluster in Cancer known as the Beehive, Praesepe, and Messier 44. After dusk, the moon will shine several finger widths to the upper right (or 3.5 degrees to the celestial north of) the cluster. Towards midnight, the moon will move a little closer to the Beehive. The moon and the cluster will be close enough to share the field of binoculars (green circle), but you’ll see more of the “bees” if you hide the moon just outside of your field of view.
Sunday, May 8 – First Quarter Moon (at 00:21 GMT on May 9)
When the moon completes the first quarter of its orbit around Earth at 8:21 p.m. EDT on Sunday, May 8 (or 00:21 GMT on Monday, May 9), the relative positions of the Earth, sun, and moon will cause us to see our natural satellite half-illuminated – on its eastern side. While at first quarter, the moon always rises around noon and sets around midnight, allowing it to be seen in the afternoon daytime sky, too. The evenings surrounding the first quarter phase are the best ones for viewing the lunar terrain when it is dramatically lit by low-angled sunlight. Observers in parts of Asia and the Pacific Ocean will be able to see the Lunar X and V features for several hours centered on 10:30 GMT.
Wednesday, May 11 – Major Mare Imbrium (evening)
On Wednesday, May 11, the lunar terminator will reach the western rim of Mare Imbrium, the Sea of Rains. That dark, circular feature dominates the northwestern quadrant of the moon’s Earth-facing hemisphere. The mare is the moon’s largest impact basin, measuring more than 715 miles (1145 km) in diameter. It was formed during the late heavy bombardment period approximately 3.94 billion years ago. Telescope views of Mare Imbrium at this phase will reveal ejecta blankets around its major craters (Aristillus and Archimedes), several nearly-submerged ghost craters (Cassini and Wallace), and numerous subtle wrinkle ridges (Heim, Sille).
Thursday, May 12 – Mare Imbrium Mountains (evening)
Thursday, May 12 will offer a fine opportunity to view the spectacular, mountain chains, actually segments of the old basin rim, that encircle the rim of Mare Imbrium. The most northerly arc of mountains is the Lunar Alps, or Montes Alpes. Binoculars or a telescope will reveal a slash cutting through them called the Alpine Valley, or Vallis Alpes, where the moon’s crust has dropped between parallel faults. To the lower right (lunar southeast) of the Alps are the Caucasus Mountains, or Montes Caucasus. That mountain range disappears under a lava-flooded zone connecting Mare Imbrium with Mare Serenitatis to the southeast. The southeastern edge of Mare Imbrium is bordered by the lengthy Apennine Mountains, or Montes Apenninus. They sink out of sight near the prominent crater Eratosthenes. The Montes Carpatus ring the south, near crater Copernicus. On the opposite side of the mare is the distinctive, round Sinus Iridum, the Bay of Rainbows.
Sunday, May 15 – Deep Total Lunar Eclipse (03:29 to 04:53 GMT on May 16)
Starting in late evening on Sunday, May 15, a total lunar eclipse will be observable in eastern North America, Central America, and South America. For the rest of North America, Hawaii, and the eastern Pacific Ocean, the eclipse will be in progress as the moon rises at dusk. Western Europe and Africa will see only the later stages before the moon sets at dawn. This is a very deep and lengthy total eclipse. First contact with the umbra occurs at 10:28 p.m. EDT and 9:28 p.m. PDT (or 02:28 GMT on May 16). Totality will last from 11:29 p.m. EDT and 8:29 p.m. PDT (or 03:29 GMT on May 16) until 12:54 a.m. EDT and 9:54 p.m. PDT (or 04:54 GMT on May 16), for a total duration of 85 minutes. During the eclipse, watch for the upper (northern) limb to be darkest, and for the surrounding stars of Libra and brighter deep sky objects in Scorpius to return to view. Lunar eclipses are completely safe to observe unfiltered with your unaided eyes, binoculars, and telescopes.
Monday, May 16 – Full Milk Blood Moon (at 04:14 GMT)
The moon will reach its full phase at 12:14 a.m. EDT (or 04:14 GMT) on Monday, May 16. May’s full moon always shines in or near the stars of Libra or Scorpius. Every culture around the world has developed its own stories about the full moon, and has assigned special names to each full moon. The indigenous Ojibwe groups of the Great Lakes region call the May full moon Zaagibagaa-giizis “Budding Moon” or Namebine-giizis, the “Sucker Moon”. For them it signifies a time when Mother Earth again provides healing medicines. The Cree of North America call it Athikipisim, the “the Frog Moon” – the time when frogs become active in ponds and swamps. The Cherokee call it Ahnisguti, the “the Planting Moon”, when the fields are plowed and sown. In European cultures, the moon is commonly called the Full Milk Moon, Full Flower Moon, or Full Corn Planting Moon. When fully illuminated, the moon’s geology is enhanced – especially the contrast between the bright, ancient, cratered highlands and the darker, younger, smoother maria. The moon will be in full eclipse, a so-called “blood moon”, when precisely full.
Wednesday, May 18 – Mars Passes Neptune (pre-dawn)
Low in the southeastern sky before dawn on the mornings surrounding Wednesday, May 18, the faster motion of magnitude 0.76 reddish planet Mars will carry it closely past the much fainter blue planet Neptune. They’ll be close enough to share the view in a backyard telescope from May 16 to May 20, with Mars approaching Neptune from celestial west. At closest approach on Wednesday, look for Neptune positioned 32 arc-minutes (slightly more than the moon’s diameter) to the south of 730 times fainter Neptune. (Your telescope may flip and/or mirror-image the arrangement shown here.) The conjunction will be more easily seen by observers at southerly latitudes, where the planets will sit higher in a darker sky.
Sunday, May 22 – Half Moon Meets Saturn (pre-dawn)
In the southeastern sky before dawn on Sunday, May 22, the waning half-illuminated moon will commence its monthly trip past the bright planets gathered there. On Sunday, Saturn will appear as a yellowish dot shining a slim palm’s width above (or 5 degrees to the celestial north) of the moon. Mars and the much brighter planets Venus and Jupiter will be arrayed well off to their left (celestial east), making a terrific photo opportunity when composed with some interesting scenery.
Sunday, May 22 – Third Quarter Moon (at 18:43 GMT)
The moon will officially reach its third quarter phase at 2:43 p.m. EDT or 18:43 GMT on Sunday, May 22. At third (or last) quarter the moon is half-illuminated, on its western, sunward side. It will rise around midnight, and then remain visible until it sets in the western daytime sky in late morning. Third 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. The week of dark, moonless evening skies that follow this phase are the best ones for observing deep sky targets.
Tuesday, May 24 – Crescent Moon Meets Mars (pre-dawn)
wo days after the moon’s visit with Saturn, its waning crescent will hop east to shine a generous palm’s width to the lower right (or 7 degrees to the celestial southwest) of Mars. With brighter Jupiter and Venus gleaming to their left (celestial east), the grouping will be a pretty sight once they clear the treetops after about 4 am local time. The scene will also make a terrific photo opportunity when composed with some interesting scenery. For observers in western North America, the moon will be somewhat closer below Mars.
Wednesday, May 25 – Crescent Moon near Jupiter and Mars (pre-dawn)
In the southeastern sky on Wednesday morning, May 25 during the hours before dawn, the waning crescent moon will appear a palm’s width to the lower left (or 5 degrees to the celestial southeast) of bright Jupiter and fainter reddish Mars. Venus will shine brilliantly to the lower left of the trio, making yet another fine photo opportunity.
Friday, May 27 – Old Moon and Venus (before sunrise)
A pretty sight will greet early risers in the eastern sky before sunrise on Friday, May 26 when the very slim crescent of the old moon will shine just to the lower left (celestial east) of the extremely bright planet Venus. Mars and Jupiter will accompany them, off to their upper right. Unlike the moon, a telescope view of Venus will show a 76%-illuminated disk. That’s because Venus will be farther from Earth than the sun is, while the moon will be closer than the sun. (Point optics away from the eastern horizon before the sun rises.) Hours earlier, observers in southern Madagascar, most of Southeast Asia, southeastern China, and most of Micronesia can see the moon occult Venus in daytime around 04:00 GMT.
Sunday, May 29 – Mars Passes Jupiter (pre-dawn)
In the eastern pre-dawn sky on the morning of Sunday, May 29, the faster motion of Mars will carry it past much brighter Jupiter in a very tight conjunction. Both planets will share the view in a telescope (inset, green circle) from Friday to Tuesday, with Mars approaching from the right (celestial west). At closest approach on Sunday morning, Mars will sit 0.6 degrees (about the moon’s diameter) below Jupiter, although your telescope may flip and/or mirror-image the arrangement shown here. The optimal viewing time will be 4-5 a.m. local time.
Monday, May 30 – New Moon (at 11:30 GMT)
On Monday, May 30 at 7:30 a.m. EDT or 11:30 GMT, the moon will officially reach its new moon phase. At that time our natural satellite will be located in Taurus, and less than 1 degree north of the sun. While at its new phase, the moon is travelling between Earth and the sun. Since sunlight can only shine on the far side of the moon, and the moon is in the same region of the sky as the sun, it becomes completely hidden from view from anywhere on Earth for about a day. After the new moon phase Earth’s celestial night-light will return to shine as a crescent in the western evening sky.
Mercury will open May shining at magnitude 0.59 in the northwestern sky after sunset – completing its best evening appearance of the year for mid-northern latitude observers. On May 1, the planet will be positioned only 1 degree to the upper left (or celestial southeast) of the Pleiades Star Cluster. The following evening, the young crescent moon will join them, shining several degrees to their upper left. The optimal observing time then will be 8:30 to 9 p.m. local time. Telescope views of Mercury will display a waning crescent phase and an apparent disk diameter greater than 8.5 arc-seconds. Mercury will fade in brightness and sink deeper into the evening twilight every night, rendering it unobservable from mid-month onward. The planet will pass the sun at inferior conjunction on May 21.
Venus will continue to dominate the eastern pre-dawn sky during May. On May 1, the extremely bright, magnitude -4.1 planet will be passing one-sixth as bright Jupiter in a very close conjunction best seen before 5:30 a.m. local time. Earlier risers can see the string of fainter planets Mars and Saturn extending 33 degrees to their west. On each subsequent morning Venus’ rapid eastward motion through Pisces will increase its distance from Jupiter. That sunward swing will also drop the planet closer to the horizon. By month’s end, Venus will have diminished slightly in brightness to magnitude -3.95. Viewed in a telescope during early May, Venus will exhibit a 67%-illuminated gibbous phase and a disk 16.7 arc-seconds across. At month’s end, the planet will show a 13.7 arc-seconds-wide, 78%-illuminated disk. On May 27, the old crescent moon will shine several degrees to Venus’ lower left (or celestial east). Hours earlier, observers in southern Madagascar, most of Southeast Asia, southeastern China, and most of Micronesia can see the moon occult Venus in daytime around 04:00 GMT.
Red-tinted Mars will continue to increase its angle from the sun in the eastern sky during May, rising around 3:40 a.m. local time on May 1 and an hour earlier at month’s end. The ruddy planet will begin the month in Aquarius, with yellowish Saturn 18 degrees to its west and the close-together pair of much brighter Jupiter and Venus shining 15 degrees to its east. Mars’ faster orbital motion will carry it steadily away from Saturn and towards Jupiter. After passing half a degree south of magnitude 7.9 Neptune on May 18, Mars will cross into Pisces for a close conjunction 0.6 degrees south of 15 times brighter Jupiter on May 29. Over the month, Mars will brighten from magnitude 0.87 to 0.67. Its apparent disk size will grow from 5.8 to 6.4 arc-seconds. The waning crescent moon will hop past Mars and Jupiter on May 24 and 25, offering two nice photo opportunities.
Jupiter will begin May in a picturesque close conjunction with six times brighter Venus. The duo will be best seen, shining very low in the eastern sky, before 5:30 a.m. local time. Earlier risers can look for the line of fainter planets Mars and Saturn extending 33 degrees to their west. Jupiter will spend the entire month in western Pisces, but it won’t stretch far enough west of the sun to see those stars until after mid-month. The faster motions of Venus and Mars will cause the former to leave Jupiter behind and the latter to overtake Jupiter in another close conjunction on May 29. Jupiter will remain rather low in the sky for clear telescopic views at mid-northern latitudes during May. Jupiter’s four Galilean moons will dance to the east and west of its 34.8 arc-seconds-wide, banded disk. The Great Red Spot will appear every second or third morning. Occasionally, the small, round, black shadows of its four Galilean moons will transit. The waning crescent moon will hop past Jupiter and Mars on May 24 and 25, making a pair of nice photo opportunities.
During May Saturn will rise in the wee hours of the night, shining at magnitude 0.8 as it moves slowly prograde eastward among the stars of eastern Capricornus. It will remain visible in the southeastern sky until dawn. The planets Mars, Neptune, Jupiter, and Venus will be strung along the ecliptic to its lower left (or celestial east). Viewed in a telescope during May, Saturn’s 17 arc-seconds-wide globe, adorned with its 40 arc-seconds-wide ring system, will be surrounded by a number of its brightest moons. With the planet’s tilt diminishing until 2025, a good deal of Saturn’s southern hemisphere will extend below its ring plane this year. On May 22, the waning crescent moon will pass 5 degrees below (or celestial south) of Saturn.
Uranus will pass solar conjunction on May 5, but it will be the end of May before the magnitude 5.9 planet returns to visibility from mid-northern latitudes, where it will sit very low in the eastern pre-dawn twilight among the stars of southern Aries. On May 28, the waning crescent moon will shine a short distance to Uranus’ left (or celestial northeast). The same day, the moon will occult Uranus around 14:00 GMT for Easter Island, most of South America, the Cape Verde Islands, and most of W Africa – the fourth of 15 consecutive monthly lunar occultations of the seventh planet.
Throughout May, the magnitude 7.9 planet Neptune will be parked near the border between Aquarius and Pisces. It will be observable in the dark southeastern sky for an hour or so after it rises, during the wee hours. On May 1, the planet will be positioned just 3.5 degrees west of Jupiter’s close conjunction with Venus. While Venus races east on the following mornings, Jupiter will pull away from Neptune at a slower rate. At the same time, Mars will approach Neptune rapidly from the west. At their closest approach on May 17-18, Neptune will be 0.5 degrees above (or celestial north) of Mars, allowing them to share the view in a backyard telescope over several mornings. Mars’ reddish disk will appear several times larger than blue Neptune’s 2.25 arc-seconds-wide disk.
Gibbous: Used to describe a planet or moon that is more than 50% 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 fainter objects, such as meteors, dim stars, nebulas, and galaxies, give your eyes at least 15 minutes to adjust to the darkness. Avoid looking at your phone’s bright screen by keeping it tucked away. If you must use it, set the brightness to minimum – or cover it with clingy red film.
Light Pollution: Even from a big city, one can see the moon, a handful of bright stars, and the brightest planets – if they are above the horizon. But to fully enjoy the heavens — especially a meteor shower, the fainter constellations, or to see the amazing swath across the sky that is the disk of our home galaxy, the Milky Way — rural areas are best for night sky viewing. If you’re stuck in a city or suburban area, use a tree or dark building to block ambient light (or moonlight) and help reveal fainter sky objects. If you’re in the suburbs, simply turning off outdoor lights can help.
Prepare for skywatching: If you plan to be outside for more than a few minutes, and it’s not a warm summer evening, dress more warmly than you think is necessary. An hour of winter observing can chill you to the bone. For meteor showers, a blanket or lounge chair will prove to be much more comfortable than standing, or sitting in a chair and craning your neck to see overhead.
Daytime skywatching: On the days surrounding first quarter, the moon is visible in the afternoon daytime sky. At last quarter, the moon rises before sunrise and lingers into the morning daytime sky. When Venus is at a significant angle away from the sun it can often be spotted during the day as a brilliant point of light – but you’ll need to consult an astronomy app to know when and where to look for it. When large sunspots develop on the sun, they can be seen without a telescope – as long as you use proper solar filters, such as eclipse glasses. Permanent eye damage can occur if you look at the sun for any length of time without protective eyewear.
Originally published at www.space.com