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Venus is joined by Mars in the July twilight. Watch them come closer each evening, culminating with a super-close pairing on July 12. And ’tis the season for enjoying the Milky Way core!
- July 2: As evening twilight ends, if you have a clear view of the horizon in the west-northwest, look for the bright planet Venus just above the horizon. With clear skies and a telescope or good binoculars, you may be able to see the stars of the Beehive Cluster mostly to the left of Venus.
- July 12: Venus and Mars will appear only a finger’s width apart.
- July 23: The next full Moon is called the Buck Moon.
Sunsets in July come with an added bonus: a brilliant gem low in the western sky, calling to us to come and explore its many mysteries. This is the planet Venus. It’s our cosmic next-door neighbor – that is, the planet with the closest orbit to the orbit of Earth.
It’s also often thought of as Earth’s sister planet, given that it’s also a rocky world of the same size, though Venus developed into a hellishly hot world, where Earth became the cool, blue planet we know and love.
Venus is sometimes referred to as “the Morning Star,” or “the Evening Star,” depending on whether it’s visible around sunrise or sunset. This month, it’s the latter, and you’ll find Venus low in the west together with a faint planet Mars beginning about half an hour after sunset. In fact, you can watch each evening as Venus and Mars get closer, culminating with a close conjunction on July 12th, when they’ll be only a finger’s width apart. Look for them together with a slim, crescent Moon that’s only 10% illuminated.
In June, NASA announced that two new space missions would be heading to Venus beginning later in the decade. VERITAS and DAVINCI+ will investigate the planet’s surface and atmosphere, returning incredible images, maps, and other data, likely rewriting our understanding of how Earth’s sister planet became so inhospitable, along with how it might still be active today. They’ll be joined by the European spacecraft EnVision, for what’s sure to be an exciting new chapter in solar system exploration.
July is one of the best times of year to enjoy the magical sight that is the Milky Way. This is our view of our spiral galaxy, seen edge on, from within. Now, some part of the Milky Way is visible in the night sky any time of year, but the galaxy’s bright, complex core is only observable during certain months. Earlier in the season, you have to wait until the wee hours of the morning for the core to rise in the sky. But in June and July, the core has already risen by the time it’s fully dark, and can be seen fairly well until around 2 a.m. when it starts to set.
Now, the Milky Way is faint, and to see it, you’ll need to find your way out to fairly dark skies, but as long as you’re below about 55 degrees north latitude, you should be able to observe the Milky Way core under dark skies. (Southern Hemisphere observers have it even better, as the core appears much higher overhead there.)
One super important tip is to avoid the full moon and the days close to it since a bright Moon overwhelms the faint glow of the Milky Way. The three or four nights around the new moon are best, but the week before and after is also okay – you just have to note when the Moon will be rising or setting. There are a variety of great apps and websites to help you find dark skies and figure out when and where to look. So here’s hoping you get out there and experience one of the most fantastic sights the sky has to offer.
On Friday evening, July 2, 2021, as evening twilight ends, if you have a clear view of the horizon in the west-northwest, look for the bright planet Venus about 4 degrees above the horizon. With clear skies and a telescope or good binoculars, you should be able to see the stars of the Beehive Cluster mostly to the left of Venus. The Beehive Cluster is an open cluster of over 1,000 stars gravitationally bound together in a relatively small volume, appearing from Earth about 1.5 degrees across.
Sometime in late June through late July (2021-Jul-03 19:54 UTC with 9 days, 35 minutes uncertainty), Near-Earth Object (2015 BY3), between 28 to 62 feet (8 and 19 meters) across, will pass the Earth at between 0.2 and 120.9 lunar distances (nominally 51.9), traveling at (45,800 miles per hour (20.48 kilometers per second).
Early Sunday morning, July 4, 2021, sometime around 2:45 a.m. EDT (2021-Jul-04 06:45 UTC with 1 hour, 27 minutes uncertainty), Near-Earth Object (2020 AD1) between 48 to 107 feet (15 and 33 meters) across, will pass the Moon at between 3.3 and 3.8 lunar distances (nominally 3.6), traveling at 2,800 miles per hour (5.72 kilometers per second).
Sunday, July 4, 2021, will be when the planet Mercury reaches its greatest angular separation from the Sun as seen from the Earth for this apparition (called greatest elongation), appearing half-lit through a large enough telescope. Because the angle of the line between the Sun and Mercury and the horizon changes with the seasons, the date when Mercury and the Sun appear farthest apart as seen from the Earth is not the same as when Mercury appears at its highest above the east-northeastern horizon as morning twilight begins, which occurs on July 10 and 11.
Monday morning, July 5, 2021, at 10:47 a.m. EDT, the Moon will be at apogee, its farthest from the Earth for this orbit.
Monday evening, July 5, 2021, at 6:27 p.m. EDT, the Earth will be at aphelion, its farthest away from the Sun in its orbit, 3.4% farther away than when it was at perihelion in early January. Since the intensity of light drops off as the square of the distance from the source, the sunlight reaching the Earth at aphelion will be about 6.5% less bright than sunlight reaching the Earth at perihelion.
Sometime Monday night into Tuesday morning, July 5 to 6, 2021 (2021-Jul-06 06:30 UTC with 8 hours, 4 minutes uncertainty), Near-Earth Object (2021 MC), between 55 to 123 feet (17 and 38 meters) across, will pass the Earth at between 2.9 and 3.0 lunar distances (nominally 2.9), traveling at 16,000 miles per hour (7.15 kilometers per second).
On the morning of Tuesday, July 6, 2021, the bright star Aldebaran will appear about 8 degrees below the waning crescent Moon. Aldebaran will rise after the Moon in the east-northeast at 3:48 a.m. EDT.
On the morning of Wednesday, July 7, 2021, the planet Mercury will appear about 9 degrees below the waning crescent Moon. Mercury will rise after the Moon in the east-northeast at 4:27 a.m. EDT, just 12 minutes before morning twilight begins.
By the morning of Thursday, July 8, 2021, the Moon will have shifted such that the planet Mercury will appear 4 degrees to the right of the waning crescent Moon low on the horizon in the east-northeast. Mercury will rise in the east-northeast at 4:27 a.m. EDT, just 5 minutes after moonrise and 12 minutes before morning twilight begins.
Friday evening, July 9, 2021, at 9:17 p.m. EDT, will be the new Moon, when the Moon passes between the Earth and the Sun and will not be visible from the Earth.
The day of – or the day after – the New Moon marks the start of the new month for most lunisolar calendars:
- Sundown on Friday, July 9, 2021, marks the start of Av in the Hebrew calendar.
- The sixth month of the Chinese calendar starts on Saturday, July 10, 2021 (at midnight in China’s time zone, which is 12 hours ahead of EDT).
- In the Islamic calendar, the months traditionally start with the first sighting of the waxing crescent Moon. Many Muslim communities now follow the Umm al-Qura Calendar of Saudi Arabia, which uses astronomical calculations to start months in a more predictable way. Using this calendar, sundown on Saturday evening, July 10, 2021, will probably mark the beginning of Dhu al-Hijjah. Dhu al-Hijjah is the 12th and final month of the Islamic year. It is one of the four sacred months during which fighting is forbidden. Dhu al-Hijjah is the month of the Hajj and the Festival of the Sacrifice. Making the Hajj or pilgrimage to Mecca at least once in your life is one of the Five Pillars of Islam. (In 2021, because of the COVID-19 pandemic, Saudi Arabia is limiting the total number of pilgrims, and is requiring they be fully vaccinated to protect the health and safety of all involved.)
Saturday and Sunday morning, July 10 and 11, 2021, will be the two mornings when the planet Mercury will appear at its highest above the east-northeastern horizon (2 degrees) at the time morning twilight begins.
Beginning the evening of Saturday, July 10, 2021, the planet Saturn will begin appearing above the horizon in the east-southeast as evening twilight ends.
On the evening of Sunday, July 11, 2021, low on the west-northwestern horizon, the waxing crescent Moon will appear to the right of the bright planet Venus with the planet Mars appearing about a degree to the left of Venus. They will only be about 4 degrees above the horizon as evening twilight ends and the Moon will set first about 25 minutes later.
The next evening, Monday, July 12, 2021, the waxing crescent Moon will have shifted to appear to the upper left of the planet Venus with the planet Mars about a half degree to the lower left of Venus and the bright star Regulus appearing about 6 degrees to the left of the Moon.
Sometime late Monday night into Tuesday morning, July 12 to 13, 2021 (2021-Jul-13 07:34 UTC with 4 hours, 6 minutes uncertainty), Near-Earth Object (2019 AT6), between 26 to 59 feet (8 and 18 meters) across, will pass the Earth at between 3.7 and 4.9 lunar distances (nominally 4.2), traveling at 11,500 miles per hour (5.15 kilometers per second).
Tuesday evening, July 13, 2021, will be when the planets Venus and Mars will appear nearest to each other, with Mars appearing a half degree below Venus. The pair will only be about 4 degrees above the west-northwestern horizon as evening twilight ends at 9:44 p.m. EDT, and Mars will set first about 23 minutes later at 10:07 p.m. After this evening Venus will continue to shift to the left each evening, away from Mars and toward the bright star Regulus.
On the evening of Friday, July 16, 2021, the bright star Spica will appear about 7 degrees to the lower left of the waxing half Moon. They will appear in the southwest as evening twilight ends at 9:41 p.m. EDT, and Spica will set first 2 hours, 39 minutes later (early Saturday at 12:20 a.m.).
On Saturday morning, July 17, 2021, the Moon will appear half-full as it reaches its first quarter at 6:11 a.m. EDT.
Sometime in mid-to-late July 2021 (2021-Jul-17 19:03 UTC with 4 days, 20 hours, 30 minutes uncertainty), Near-Earth Object (2019 NB7), between 29 to 65 feet (9 and 20 meters) across, will pass the Earth at between 1.7 and 39.3 lunar distances (nominally 15.2), traveling at 30,800 miles per hour (13.76 kilometers per second).
Sunday morning, July 18, 2021, will be the last morning for this apparition when the planet Mercury will appear above the horizon in the east-northeast at the time morning twilight begins.
On Monday evening into Tuesday morning, July 19 to 20, 2021, the bright star Antares will appear about 8 degrees to the lower left of the waxing gibbous Moon. They will appear in the south as evening twilight ends at 9:39 p.m. EDT, and will set in the west-southwest at about the same time on Tuesday morning around 2:15 a.m.
By Tuesday evening into Wednesday morning, July 20 to 21, 2021, the Moon will have shifted such that Antares will appear about 8 degrees to the right of the Moon, with Antares setting first Wednesday morning at 2:10 a.m.
During the week of July 21, 2021 (2021-Jul-21 09:48 UTC with 3 days, 1 hour, 6 minutes uncertainty), Near-Earth Object (2014 BP43), between 44 to 98 feet (13 and 30 meters) across, will pass the Earth at between 4.3 and 35.3 lunar distances (nominally 16.9), traveling at 18,900 miles per hour (8.46 kilometers per second).
Wednesday morning, July 21, 2021, at 6:25 a.m. EDT, the Moon will be at perigee, its closest to the Earth for this orbit.
Wednesday evening, July 21, 2021, will be when the bright planet Venus and the bright star Regulus will appear nearest each other, with Regulus 1 degree to the lower left of Venus. As evening twilight ends at 9:37 p.m. EDT Venus will appear about 5 degrees above the west-northwestern horizon. The planet Mars will appear farther to the lower right at only 2 degrees above the horizon. Mars will set first at 9:49 p.m., Regulus next at 10 p.m., and Venus last at 10:04 p.m. After this Venus will appear to continue toward the left and away from Regulus and Mars.
The next full Moon will be Friday night, July 23, 2021, at 10:37 p.m. EDT. It’s known by many names, including the Buck Moon because early summer is normally when the new antlers of buck deer push out of their foreheads in coatings of velvety fur. The Moon will appear full for about 3 days around this time, from Thursday night through Sunday morning.