Night sky, July 2021: What you can see this month [maps], ,
A clear night sky offers an ever-changing display of fascinating objects to see — stars, constellations, and 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. Binoculars or a good beginner telescope will enhance some experiences and bring some otherwise invisible objects into view. You can also use astronomy apps and software 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).
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The night sky is more than just the moon and stars, if you know when and where to look. (Image credit: Karl Tate/SPACE.com)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 and Chris at @Astrogeoguy.
Editor’s note: If you have an amazing skywatching photo you’d like to share for a possible story or image gallery, you can send images and comments in to spacephotos@futurenet.com.
Night Sky Guides:
Calendar of Observing HighlightsThursday, July 1 – Third Quarter Moon (at 21:10 GMT)[image error]
(Image credit: Starry Night)The moon will officially reach its third quarter phase at 5:10 p.m. EDT (or 21:10 GMT) on Thursday, July 1. At third quarter our natural satellite always appears half-illuminated, on its western side – towards the pre-dawn sun. It rises in the middle of the night and remains visible in the southern sky all morning. The name for this phase reflects the fact that the moon has completed three quarters of its orbit around Earth, measuring from the previous new moon. The ensuing week of moonless evening skies will be ideal for observing deep sky targets.
Sunday, July 4 – Old Moon near Uranus (pre-dawn)[image error]
(Image credit: Starry Night)When the waning crescent moon rises in the east at about 2 a.m. local time on Sunday, July 4, it will be positioned a slim palm’s width to the right (or 5 degrees to the celestial southwest) of the magnitude 5.8 planet Uranus – close enough for them to share the view in binoculars (red circle). Try to find the planet before about 4:30 a.m. local time. After that, the brightening dawn sky will overwhelm it, but will leave the moon visible.
Sunday, July 4 – Mercury at Greatest Western Elongation (pre-dawn)[image error]
(Image credit: Starry Night)During much of July Mercury will be visible in the pre-dawn sky. On Sunday, July 4, the swiftly-moving planet will reach a maximum angle of 22 degrees west of the sun, and peak visibility for its morning apparition. The best time to see the planet will come just before 5 a.m. in your local time zone, when Mercury will sit very low in the east-northeastern sky. In a telescope (inset) the planet will show a 36%-illuminated, waxing crescent phase. Mercury’s position well below the morning ecliptic (green line) will make this apparition a poor one for Northern Hemisphere observers, but a good showing for those located near the Equator, and farther south.
Monday, July 5 – Earth at Aphelion (at 22:00 GMT)[image error]
(Image credit: Starry Night)On Monday, July 5 at 6 p.m. EDT, or 22:00 GMT, Earth will reach aphelion, its farthest position from the sun for this year. The aphelion distance of 94,511,180 miles (152.1 million km) is 1.67% farther from the sun than the mean Earth-sun separation of 92,955,807.3 miles (149,597,870.7 km), which is also defined to be 1 Astronomical Unit (1 AU). Earth’s minimum distance from the sun, or perihelion, will occur on January 4.
Thursday, July 8 – Crescent Moon with Mercury (pre-dawn)[image error]
(Image credit: Starry Night)For a brief period before sunrise on Thursday, July 8, the slim crescent of the old, waning moon will be positioned several finger widths to the left (or 4 degrees to the celestial northeast) of the bright dot of Mercury. Look for the pair sitting very low over the east-northeastern horizon from the time they rise at about 4:20 a.m. local time until about 5 a.m. The moon and Mercury will be close enough to see them together through binoculars (red circle) – but turn your optics away before the sun rises.
Friday, July 9 – New Moon (at 9:16 p.m. EDT)[image error]
(Image credit: Starry Night)The moon will officially reach its new phase on Friday, July 9 at 9:16 p.m. EDT (or 01:16 GMT on Saturday, July 10). While new, the moon is travelling between Earth and the sun. Since sunlight can only reach the far side of the moon, and the moon is in the same region of the sky as the sun, the moon becomes unobservable from anywhere on Earth for about a day (except during a solar eclipse). After the new moon phase Earth’s celestial night-light will return to shine in the western evening sky
Sunday, July 11 – Crescent Moon Passes Venus and Mars (after sunset)[image error]
(Image credit: Starry Night)Low in the west-northwestern sky after sunset on Sunday, July 11, the young crescent moon will shine a generous palm’s width to the right (or 6.5 degrees to the celestial northwest) of two planets – bright Venus and much fainter Mars. Before they set at about 10 p.m. local time, the trio will make a nice wide-field photo when composed with some interesting scenery. On the following evening, the moon’s orbital motion will lift it to sit a similar distance above those two planets.
Monday, July 12 – Venus Kisses Mars (after sunset)[image error]
(Image credit: Starry Night)On the evenings surrounding Monday, July 12, extremely bright Venus and much fainter Mars will meet in a very close conjunction quite low in the west-northwestern sky. While both planets have been traveling eastward in their orbits (red tracks with labelled dates:times), the faster motion of inner planet Venus will cause it to catch up to and pass slower-moving Mars from tonight to tomorrow. Look closely! Magnitude +1.84 Mars will be nearly 200 times fainter than magnitude -3.87 Venus, and positioned just 34 arc-minutes (equal to about the full moon’s diameter) to the lower left of Venus. From a location with an unobstructed horizon, start to look for the planets after about 9 p.m. local time, when they’ll sit a fist’s diameter above the horizon. They’ll set by 10 p.m. local time. Binoculars (red circle) will help – but use them only after the sun has completely set. The two planets will share the view in binoculars from about July 4 to 21, but they’ll only be telescope-close (yellow circle) from July 11 to 14.
Friday, July 16 – Lunar X in Early Evening (peaks at 9 p.m. EDT)[image error]
(Image credit: Starry Night)Several times a year, for a few hours near its first quarter phase, a feature on the moon called the Lunar X becomes visible in strong binoculars and backyard telescopes. When the rims of the craters Purbach, la Caille, and Blanchinus are illuminated from a particular angle of sunlight, they form a small, bright X-shape. The Lunar X is located on the terminator, about one third of the way up from the southern pole of the Moon (at 2? East, 24? South). On Friday, July 16 the ‘X’ is predicted to start developing by about 7 p.m. EDT (or 23:00 GMT), peak in intensity at around 9 p.m. EDT (or 01:00 GMT on July 17), and then gradually fade out. The peak will be during waning daylight for observers in the eastern Americas – but you can observe the moon in a telescope during daytime, as long as you take care to avoid the sun. The Lunar X will be visible anywhere on Earth where the moon is shining, especially in a dark sky, between 23:00 and 03:00 GMT on July 17.
Saturday, July 17 – First Quarter Moon (at 10:10 GMT)[image error]
(Image credit: Starry Night)When the moon completes the first quarter of its orbit around Earth at 6:10 a.m. EDT on Saturday, July 17 (or 10:10 GMT) its 90 degree angle away from the sun will cause us to see the moon half-illuminated – on its eastern side. At first quarter, the moon always rises around mid-day and sets around midnight, so it is also visible in the afternoon daytime sky. The evenings surrounding first quarter are the best ones for seeing the lunar terrain when it is dramatically lit by low-angled sunlight, especially along the terminator, the pole-to-pole boundary between the lit and dark hemispheres.
Saturday, July 17 – Pluto at Opposition (all night)[image error]
(Image credit: Starry Night)On Saturday, July 17, the dim and distant dwarf planet designated (134340) Pluto will reach opposition for 2021. On that date, the Earth will be positioned between Pluto and the sun, minimizing our distance from that outer world. While at opposition, Pluto will be located 3.10 billion miles, 4.98 billion km, or 277 light-minutes from Earth – and it will shine with an extremely faint visual magnitude of +14.3. That’s far too dim for visual observing through backyard telescopes. Pluto will be located in the sky about midway between Saturn and the bright star Nunki in Sagittarius’ Teapot asterism. Telescope-owners (inset, yellow circle) can focus on a magnitude 7.8 star named HIP97602, which will be sitting 9.3 arc-minutes directly below Pluto on opposition night. Even if you can’t see Pluto directly, you will know that it is there.
Sunday, July 18 – Asteroid Pallas Pauses (overnight)[image error]
(Image credit: Starry Night)On Sunday, July 18, the main belt asteroid designated (2) Pallas will halt its regular eastward motion in front of the distant stars, and begin a retrograde loop that will last until early November (red path). Pallas’ visual magnitude of 9.7 will allow it to be seen in amateur telescopes starting in late evening. On July 18 Pallas will be positioned in the eastern sky, less than half a degree to the right (or celestial south) of the magnitude 6.65 star HIP116417 and the magnitude 7.35 star HIP116431, which sit near the ring of stars that forms the western fish in Pisces. The asteroid and those stars will appear together in the eyepiece of your telescope.
Tuesday, July 20 – View the Apollo Sites (all night)[image error]
(Image credit: Starry Night)It’s the 52nd Anniversary of humankind’s first steps on another world! The six crewed Apollo Missions were sent to different regions of the moon in order to carry out experiments and to bring back rock samples that help us determine the age and composition of the moon’s surface. For safety reasons, Apollo 11 was sent to the flat and relatively featureless terrain of Mare Tranquillitatis “Sea of Tranquility”. Later missions landed in more rugged regions with complex geology. When the moon approaches the full phase, all of the regions where the astronauts explored are illuminated by sunlight, including the most westerly site, Apollo 12 in Oceanus Procellarum.
Wednesday, July 21 – Venus Passes Regulus (after sunset)[image error]
(Image credit: Starry Night)For about an hour after sunset on Wednesday, July 21, and very low in the west-northwestern sky, the very bright planet Venus will gleam above the prominent double star Regulus in Leo. The orbital motion of Venus will carry it within a finger’s width to the upper right of (or 1 degree to the celestial north) of Regulus on Wednesday – close enough for them to be viewed together in a backyard telescope. Magnitude -3.93 Venus will outshine magnitude +1.34 Regulus by about 130 times. The duo will be observable in binoculars (red circle), with Mars to their lower right, for the entire week. (Ensure that the sun has set fully before pointing optics towards the western horizon.)
Friday, July 23 – Full Thunder Moon (at 2:37 GMT)[image error]
(Image credit: Starry Night)The moon will reach its full phase on Friday, July 23 at 10:37 p.m. EDT (or 02:37 GMT on Saturday, July 24). The July full moon, commonly called the Buck Moon, Thunder Moon, or Hay Moon, always shines in or near the stars of Sagittarius or Capricornus. The indigenous Ojibwe people of the Great Lakes region call this moon Abitaa-niibini Giizis, the Halfway Summer Moon, or Mskomini Giizis, the Raspberry Moon. The Cherokees call it Guyegwoni, the Corn in Tassel Moon. The Cree Nation of central Canada calls the June full moon Opaskowipisim, the Feather Moulting Moon (referring to wild water-fowl habits), and the Mohawks call it Ohiarihko:wa, the Fruits are Ripened Moon. Because the moon is full when it is opposite the sun in the sky, full moons always rise in the east as the sun is setting, and set in the west at sunrise. Since sunlight is striking the moon vertically at that time, no shadows are cast; all of the variations in brightness you see arise from differences in the reflectivity, or albedo, of the lunar surface rocks.
Saturday, July 24 – Bright Moon below Saturn and Jupiter (all night)[image error]
(Image credit: Starry Night)While the moon’s monthly visit with the gas giant planets will begin with Saturn on the previous evening, skywatchers who are outside on Saturday night, July 24 will find our slightly-less-than-full natural satellite shining very brightly below and between bright Jupiter on the left (or celestial northeast) and Saturn on the right (celestial northwest). After they finish rising around 9:30 p.m. local time the trio will make a nice wide-field photo opportunity when composed with some interesting scenery.
Sunday, July 25 – Gibbous Moon and Jupiter (all night)[image error]
(Image credit: Starry Night)After 24 hours, the moon’s eastward orbital motion will move it to a slim palm’s width below (or 4.75 degrees to the celestial south) of Jupiter on Sunday night, July 25. The pair will be visible together in binoculars all night long after they rise in the east-southeast at about 10 p.m. local time. The scene will make another nice wide-field photo opportunity by adding Saturn well off to their right.
Thursday, July 29 – Southern Delta-Aquariids Meteors Peak (at 5:00 GMT)[image error]
(Image credit: Starry Night)The annual Southern Delta Aquariids meteor shower lasts from July 21 to August 23. It will peak before dawn on Thursday, July 29, but it is quite active for a week surrounding that date. This shower, produced by debris dropped from periodic Comet 96P/Machholz, commonly generates 15-20 meteors per hour at the peak. It is best enjoyed from the southern tropics, where the shower’s radiant, in southern Aquarius, climbs higher in the sky. Unfortunately, the bright gibbous moon shining in the night-time sky on the peak date will severely reduce the number of meteors seen – so continue your meteor-watching on the following few nights, when the moon will wane and rise later.
Thursday, July 29 – Mars meets Regulus (after Sunset)[image error]
(Image credit: Starry Night)On Thursday, July 29, Mars will follow in Venus’ footsteps and pass only 38 arc-minutes (less than a finger’s width) above Leo’s brightest star Regulus. They’ll be visible just above the west-northwestern horizon after sunset, with Venus shining brightly to their upper left (or celestial east). White-colored Regulus will shine slightly brighter than reddish Mars. The pair will be close enough to be seen together in a backyard telescope (red circle) for a night or two on either side of Thursday, too; but objects observed that low in the sky will be blurred by Earth’s atmosphere. Observers viewing from equatorial and Southern Hemisphere latitudes will see them higher, and in a darker sky.
Thursday, July 29 – Double Shadow Transit on Jupiter (from 20:05 to 20:41 GMT)[image error]
(Image credit: Starry Night)From time to time, the small round black shadows cast by Jupiter’s four Galilean moons become visible in amateur telescopes as they cross (or transit) the planet’s disk. On Thursday, July 29, observers with telescopes in Central Europe, the Middle East, and most of Asia can see two shadows crossing Jupiter at the same time. At 11:05 p.m. IDT (or 20:05 GMT) Io’s small shadow will join Callisto’s larger shadow already in transit. About 35 minutes later, at 11:41 p.m. IDT (or 20:41 GMT), Callisto’s shadow will move off the planet, leaving Io’s shadow to complete its crossing almost two hours later.
Saturday, July 31 – Third Quarter Moon Again (at 13:16 GMT)[image error]
(Image credit: Starry Night)When a lunar phase occurs in the first few days of a calendar month, it can repeat at month’s end. For the second time in July, the moon will officially reach its third quarter phase – at 9:16 a.m. EDT (or 13:16 GMT) on Saturday, July 31. The ensuing week of moonless evening skies will be ideal for observing deep sky targets.
Planets[image error]
(Image credit: Starry Night)Mercury will spend all of July in the eastern pre-dawn sky – but it won’t be easily observable during the final week. Mercury’s position south of the dawn ecliptic will prevent the planet from rising very long before the sun – making this apparition a poor one for Northern Hemisphere observers, but a good one for those viewing the planet from south of the equator. Mercury will reach greatest elongation and peak visibility on July 4, when it will stretch to 21.6? west of the sun. At mid-northern latitudes, the best time to see Mercury will then be at about 4:45 a.m. local time. Mercury will brighten from magnitude 0.8 to -2.1 during July. Viewed in a telescope, the speedy planet will wax in illuminated phase from 28% on July 1 to fully-illuminated at month’s end. Meanwhile, the planet’s apparent disk diameter will decrease from 8.7 to 5 arc-seconds. The old crescent moon will shine a few finger widths to the northeast of Mercury on July 8.
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(Image credit: Starry Night)Extremely bright Venus will increase its angle east of the sun from 25.5? to 33? during July. The very shallow evening ecliptic will prevent the magnitude -3.87 planet from climbing very high over the western horizon after sunset, so you’ll need an unobstructed view toward the west to see it. During the month, Venus’ easterly orbital motion will counteract the westerly shift of the sky due to our orbit around the sun – so the planet will set at about 10 p.m. local time all month long. The earlier sunsets in late July will surround Venus with a darker sky. Viewed through a telescope in July, Venus will exhibit an 85%-illuminated waning gibbous phase and a slowly increasing apparent disk diameter of about 12 arc-seconds. (As always, ensure that the sun has completely disappeared below the horizon before using binoculars or telescopes to view Venus.) On July 11, Venus will depart Cancer for Leo. Meanwhile, faster-moving Venus will catch up to and pass slower-moving Mars in a close conjunction – with Venus outshining Mars by nearly 200 times! The two planets will share the view in binoculars from about July 4 to 21, but they’ll only be telescope-close from July 11 to 14. The young crescent moon will hop past the close-together planets on July 11-12, offering a nice photo opportunity.
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(Image credit: Starry Night)After spending many months parked halfway up the western evening sky, magnitude 1.8 Mars will spend July descending into the western post-sunset twilight while it reduces its angular separation east of the sun from 32? to 22?. On July 1 Mars will set at about 10:30 p.m. local time; and at 9:15 p.m. on July 31. Telescope views of Mars during July will show a shrinking, only 3.8 arc-seconds-wide disk. Mars’ slow easterly prograde motion will carry it from Cancer into Leo on July 10, just days before faster-moving and 200 times brighter Venus will overtake and pass just 0.5? to the north of Mars, on July 12-13. On the same evenings, the young crescent moon will hop past the duo. Venus will appear with Mars in binoculars from about July 4 to 21, and the pair will be telescope-close from July 11 to 14.
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(Image credit: Starry Night)Throughout July, bright, white Jupiter will be travelling retrograde westward across the faint stars of western Aquarius – with yellowish Saturn shining 19? to its right (or celestial east). As the month opens, Jupiter will rise shortly after 11 p.m. local time. By July 31, the planet will be observable from dusk to dawn, and it will have brightened slightly from magnitude -2.65 to -2.83. Unfortunately, the low summertime ecliptic will prevent Jupiter from climbing more than one-third of the way up the southern sky. Telescope views of Jupiter during July will show its large, banded disk increasing in apparent diameter from 45.3 to 48.4 arc-seconds. The Great Red Spot will be visible crossing Jupiter every second or third night. Single transits across Jupiter by the round, black shadows of its Galilean moons will be commonplace. A double shadow transit event will be visible across Eurasia on July 29. The waning gibbous moon will shine less than 5 degrees below (to the celestial south of) Jupiter from dusk to dawn on July 25.
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(Image credit: Starry Night)Saturn will be ideally positioned for viewing in evening during July as it approaches opposition in early August. On July 1, the ringed planet will rise shortly after 10 p.m. local time. That will advance to 8:45 p.m. at month-end. All month long, Saturn will be travelling retrograde west across the surrounding stars of central Capricornus. But while Saturn’s magnitude 0.4 will outshine all of the stars of that constellation, it can’t compete with 16 times brighter Jupiter shining 19? to its left (or celestial east). The low summertime ecliptic will keep Saturn from ever climbing more than one-third of the way up the southern sky. When viewed through a backyard telescope, Saturn will exhibit its majestic rings, a number of its moons, and a mean apparent disk size of 18.5 arc-seconds. The waning gibbous moon will hop past Saturn on July 23-24.
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(Image credit: Starry Night)During July, blue-green Uranus will be available for observing in the eastern pre-dawn sky – especially near the end of the month, when it will rise around midnight and reach more than 37? altitude before the dawn twilight arrives. The magnitude 5.8 planet will be slowly travelling eastward across the stars of southern Aries, roughly between two stars of comparable brightness, Omicron and Rho Arietis. The waning crescent moon will pass several finger widths below (or 4.5 degrees to the celestial south) of Uranus on July 4-5.
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(Image credit: Starry Night)During July the distant and slow-moving planet Neptune will be travelling retrograde westward through northeastern Aquarius – approximately a palm’s width to the left (or 6 degrees to the east) of the 4th-magnitude stars Psi, Xi, and Phi Aquarii. The blue, magnitude 7.9 planet will be rising just after midnight on July 1 and by 10:30 pm on July 31.
Skywatching TermsGibbous: 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 TipsAdjust 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.
Further Reading[image error]
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