What’s Up: Skywatching Tips from NASA For July

ABOVE VIDEO: What are some skywatching highlights you can see in July 2020? Enjoy the giant planets Jupiter and Saturn with their moons, stay up late to spot Mars rising. Plus: what would you see stargazing on the Red Planet?

More about observing the moons of Jupiter and Saturn

No matter how many times you see them, it’s always kind of amazing that you can easily observe distant moons orbiting another planet with your own eyes.

With an inexpensive pair of binoculars, it’s quite easy to spy Jupiter’s four largest moons: Io, Europa, Ganymede, and Callisto.

These four moons are often referred to as the Galilean moons as they were first observed using a telescope by astronomer Galileo Galilei in 1610. You can repeat Galileo’s own discovery process by observing Jupiter over several nights, and drawing the positions of the moons, noting how they move about from night to night. Even observing them just a few hours apart on the same night can reveal their movement to you.

Saturn’s largest moon, Titan, was first observed by Christiaan Huygens in 1655, so it’s fitting the ESA probe that landed there in 2005 was named for him.

Titan is about the size of the planet Mercury, but much, much farther away, making it a bit too faint to see without a telescope. But in general, with even an entry level telescope (2-inches or larger), if you can make out the rings of Saturn, you can likely see Titan too.

Daily Guide

July 2

On Thursday night, July 2, 2020, the bright star Antares will appear to the lower right of the waxing nearly-full Moon.

July 4

Saturday morning, July 4, 2020, the Earth will be at aphelion, its farthest from the Sun in its year-long orbit. The Earth will be 3.4% farther from the Sun than it was at perihelion in early January. Since light intensity drops off as the square of the distance from the light source, the sunlight reaching the Earth at aphelion will be about 6.5% less bright than sunlight reaching the Earth at perihelion.

July 5

As mentioned above, the next full Moon will be early Sunday morning, July 5, 2020, appearing opposite the Sun at 12:44 a.m. EDT. This will be a partial penumbral eclipse of the Moon, visible from most of North America, but the slight reduction in brightness on part of the Moon will be difficult to notice with the human eye. The Moon will start to enter the partial shadow on Saturday night, July 4, 2020, at 11:07 p.m. EDT. On Sunday morning at 12:30 a.m. (the peak of the eclipse) about 35 percent of the Moon will be in the partial shadow. The Moon will finish exiting the partial shadow of the Earth at 1:52 a.m.

On Sunday night into Monday morning, July 5 to 6, 2020, the full Moon and the planets Jupiter and Saturn will form a triangle. The Moon will appear in the southeast at about 3 degrees above the horizon as evening twilight ends, with Jupiter above the Moon and Saturn to the left of the Moon. The Moon will reach its highest in the sky for the night on Monday morning (at 2:11 a.m. EDT for the Washington, D.C. area), with Jupiter to the right and Saturn above, and the Moon will be about 19 degrees above the horizon in the southwest as morning twilight begins (at 4:38 a.m. EDT).

July 8

Wednesday morning, July 8, 2020, will be when the brightest of the planets, Venus, will reach its greatest brilliancy (a geometric approximation of its greatest brightness) for this apparition. The bright star appearing to the lower left of Venus will be Aldebaran. For the Washington, D.C. area, Venus will rise in the east-northeast at 3:29 a.m. EDT, Aldebaran will rise around 3:40 a.m., morning twilight will begin around 4:40 a.m., but Venus should be bright enough to remain visible well into dawn. Since Venus will be near aphelion (its farthest from the Sun in its orbit), Venus will not be as bright this apparition as it can be in other apparitions.

Also Wednesday morning (depending upon viewing conditions), the planet Mercury should begin emerging from the glow of dawn about 30 minutes before sunrise, appearing low on the horizon in the east-northeast (rising at 5:21 a.m. EDT for the Washington, D.C. area). Mercury passed between the Earth and the Sun on June 30, 2020.

July 11

On Saturday morning, July 11, 2020, the planet Mars will appear to the left of the waning gibbous Moon. For the Washington, D.C. area, Mars will rise about 8 degrees to the left of the Moon at 12:21 a.m. EDT and they will appear to move closer together until Mars is lost in morning twilight, which will begin at 4:42 a.m.

July 12

By Sunday morning, July 12, 2020, the waning gibbous Moon will appear to have shifted to the other side of the planet Mars. For the Washington, D.C. area, the Moon will rise in the east at 12:38 a.m. EDT with Mars appearing about 5 degrees to the upper right of the Moon, and morning twilight will begin at 4:43 a.m.

Also Sunday morning, Venus and Aldebaran will appear at their closest to each other, about 1 degree apart. For the Washington, D.C. area, Aldebaran will rise to the lower right of Venus in the east-northeast at 3:24 a.m. EDT and they will appear about 15 degrees above the horizon at the time morning twilight begins (at 4:43 a.m.).

Sunday afternoon, at 3:27 p.m. EDT, the Moon will be at apogee, its farthest from the Earth for this orbit. Sunday evening, the waning Moon will appear half-full as it reaches its last quarter at 7:29 p.m. EDT.

July 14

On Tuesday morning, July 14, 2020, the planet Jupiter will appear opposite the Sun as seen from the Earth (called “opposition”). Jupiter will be at its closest and brightest for this apparition, effectively a “full Jupiter,” rising around sunset and setting around sunrise.

July 16

Starting the morning of Thursday, July 16, 2020, the planet Mercury will be above the horizon at the time morning twilight begins (at least for the Washington, D.C. area). This will make all five of the naked eye planets visible (if you have a clear view of Mercury on the horizon in the east-northeast and Jupiter and Saturn on the horizon in the southwest).

July 17

On Friday morning, July 17, 2020, the brightest of the planets, Venus, will appear near the waning crescent Moon and the bright star Aldebaran. For the Washington, D.C. area, Venus will rise in the east-northeast at 3:11 a.m. EDT, with the crescent Moon to the upper left and the bright star Aldebaran to the upper right. By the time morning twilight begins (at 4:48 a.m.) Venus will be about 18 degrees above the horizon in the east, after which it will become harder to see Aldebaran and the crescent Moon as the sky lightens with dawn.

July 19

Sometime around Sunday, July 19, 2020 (2020-Jul-19 05:32 UTC with 1 day, 12 hours, 59 minutes uncertainty), Near Earth Object (2016 DY30), between 2 and 5 meters (7 to 15 feet) across, will pass the Earth at between 2.0 and 34.7 lunar distances (nominally 9.0), traveling at 15.09 kilometers per second (33,760 miles per hour).

Also Sunday morning, if you have a very clear view of the horizon in the east-northeast, you might be able to see the waning crescent Moon to the left of the planet Mercury. For the Washington, D.C. area, the pair will rise a few minutes before morning twilight begins, and will become more difficult to see as they rise farther and the sky brightens with dawn. If you use binoculars to look for the pair, be sure to stop looking well before sunrise!

July 20

Monday afternoon, July 20, 2020, at 1:33 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.

The planet Saturn will appear opposite the Sun as seen from the Earth (called “opposition”). Saturn will be at its closest and brightest for this apparition, effectively a “full Saturn,” rising around sunset and setting around sunrise.

July 21

The sixth month of the Chinese calendar starts on Tuesday, July 21, 2020 (at midnight in China’s time zone, which is 12 hours ahead of EDT).

Sundown on Tuesday, July 21, 2020, will mark the start of Av in the Hebrew calendar. In the Islamic calendar the months traditionally start with the first sighting of the waxing crescent Moon after the New Moon, although 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.

Sunset on Tuesday evening will probably mark the beginning of Dhu al-Hijjah, the twelfth and final month of the Islamic year, a sacred month that is the month of the Hajj. Making the Hajj or pilgrimage to Mecca in Saudi Arabia at least once in your life is one of the Five Pillars of Islam. This year, because of the COVID-19 pandemic, Saudi Arabia has imposed considerable restrictions on the Hajj to protect the health and safety of all involved.

July 22

On Wednesday morning, July 22, 2020, the planet Mercury will reach its greatest westward separation from the Sun as seen from the Earth, called greatest western elongation. Because the angle of the Sun-Mercury line and the horizon is becoming more perpendicular, the date when Mercury appears highest above the horizon as morning twilight begins will be after when Mercury and the Sun appear farthest apart as seen from the Earth.

On Wednesday evening, if you have a clear view of the horizon in the west-northwest, you might be able to see the thin, waxing crescent Moon above the bright star Regulus. For the Washington, D.C. area, evening twilight will end around 9:36 p.m. EDT, Regulus will set about 18 minutes later at around 9:54 p.m., and the Moon will set around 10:14 p.m.

July 23

Keep an eye on the news, as this may change, but we might have a naked eye comet visible in the evenings in July 2020. Comet C/2020 F3 (NEOWISE) was discovered on March 27, 2020, and will make its closest approach to the Sun on July 3, 2020, passing closer to the Sun than Mercury. If (and this is a big if) it does not break up as it passes close to the Sun, in its current orbit it will pass its closest to the Earth on July 23, 2020. For the Washington, D.C. area, on Wednesday evening, July 22, 2020, we may be able to see this comet near its closest between moonset at 10:14 p.m. EDT when it will be in the northwest about 20 degrees above the horizon (and the light of the Moon will no longer interfere with comet viewing) and around 1 a.m. on July 23, 2020, when the comet will set in the north-northwest.

July 25

Early Saturday morning, July 25, 2020, at about 1 a.m. EDT, the Moon will be at perigee, its closest to the Earth for this orbit.

July 26

On Sunday morning, July 26, 2020, Mercury will appear at its highest above the horizon at the time morning twilight begins (3.5 degrees above the east-northeast horizon for the Washington, D.C. area), after which Mercury will begin shifting towards the glow of dawn again. Because the angle of the Sun-Mercury line and the horizon is becoming more perpendicular, Mercury will appear highest above the horizon as morning twilight begins four days after Mercury appeared farthest apart from the Sun as seen from the Earth.

On Sunday evening, the bright star Spica will appear about 7 degrees below the waxing, nearly half-full Moon. They will appear in the southwest as evening twilight ends and Spica will set first in the west-southwest (at 11:38 p.m. EDT for the Washington, D.C. area).

July 27

Monday morning, July 27, 2020, will be the last morning when Jupiter will be above the horizon at the time morning twilight begins (for the D.C. area, at least). The Moon will appear half-full as it reaches its first quarter at 8:33 a.m. EDT.

The Southern Delta-Aquariids are expected to be active from around July 12 to Aug. 23, peaking on Monday, July 27, 2020. At the peak, under ideal conditions (a clear, dark night in the southern hemisphere) you might be able to see 25 meteors per hour, although fewer meteors will be visible for us in the northern hemisphere. If the weather is clear with no clouds or high hazes, you find in a place with a clear view of a wide expanse of the sky (especially towards the south) that is far from any light sources or urban light pollution, the best time to look should be on Monday morning, July 27, 2020, between moonset (after 12:20 a.m. EDT for the Washington, D.C. area) and any first signs of dawn (before about 4:17 a.m.).

July 29

On Wednesday night into early Thursday morning, July 29 to 30, 2020, the bright star Antares will appear about 5 degrees below the waxing gibbous Moon. For the Washington, D.C. area, evening twilight will end around 9:28 p.m. EDT when the Moon will be 30 degrees above the horizon in the south. Antares will set before the Moon in the southwest Thursday morning at about 1:34 a.m.

August 1

On Saturday morning, Aug. 1, 2020, if you have a clear view of the horizon in the east-northeast, you might be able to see the bright star Pollux about 7 degrees to the upper left of the planet Mercury. For the Washington, D.C. area, Mercury will rise at about 4:49 a.m. EDT and will be only about 2 degrees above the horizon at the time morning twilight begins at 5:04 a.m.

Saturday also is Lammas Day, a Christian holiday celebrated in some English-speaking countries that may have derived from earlier pagan celebrations. We currently divide the year into four seasons based upon the solstices and equinoxes, with summer ending on the autumnal equinox in September. This approximates summer as the quarter of the year with the warmest temperatures. The Celts and other pre-Christian Europeans celebrated “cross-quarter days” halfway between the solstices and equinoxes, and divided the seasons on these days. Using this definition, summer was approximately the quarter of the year with the longest daily periods of daylight, with summer traditionally ending August 1st (the middle of our summer). Names for this end of summer and start of fall harvest season include Lughnasadh, Lughnasa, Lúnasa, Lùnastal, and Luanistyn.

August 2

On Saturday night into Sunday morning, Aug. 1 to 2, 2020, the bright planet Jupiter will appear above the waxing gibbous Moon with Saturn appearing to the left to form a triangle. For the Washington, D.C. area, the Moon will be about 17 degrees above the horizon in the southeast as evening twilight ends at 9:24 p.m. EDT. The Moon will reach its highest in the sky for the night just after midnight on Sunday morning (at 12:01 a.m.), and Jupiter will set first in the west-southwest at 4:35 a.m., followed by the Moon (at 4:49 a.m) and Saturn (at 5:14 a.m.).

August 3

Monday morning, Aug. 3, 2020, will be the last morning that Saturn will be above the horizon at the time morning twilight begins (for the Washington, D.C. area, at least).

Sometime around Monday, Aug. 3, 2020 (2020-Aug-03 23:36 UTC with 1 day, 14 hours, 25 minutes uncertainty), Near Earth Object (2018 BD), between 3 and 6 meters (8 to 19 feet) across, will pass the Earth at between 3.8 and 24.4 lunar distances (nominally 7.5), traveling at 9.41 kilometers per second (21,060 miles per hour).

The full Moon after next will be mid-day on Monday, Aug. 3, 2020, appearing opposite the Sun in Earth-based longitude at 11:59 a.m. EDT.

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