The new moon occurs Monday, July 20, at 1:33 p.m. EDT (1733 GMT), on the same day that Saturn reaches opposition. Shining at its brightest of the year, the ringed planet will be visible all night long.
New moons happen approximately every 29.5 days when the moon is directly between the Earth and sun. The two bodies share the same celestial longitude, an alignment also called a conjunction. (Celestial longitude is a projection of the Earth's own longitude lines on the celestial sphere.)
Because no sunlight reflects off the moon's surface during this lunar phase, and because the new moon rises and sets close to the sun, the new moon is not visible in the night sky. However, sunlight reflected off the Earth's surface can faintly illuminate the moon's dark surface before and after the new moon, a phenomenon known as "Earthshine." While you may not be able to observe the new moon, the absence of moonlight can make other night-sky objects easier to see in the dark night sky.
Related: The brightest planets in July's night sky
New moons are significant to religious Muslims and Jews: they mark the beginnings and ends of the months for their respective calendars.
The July new moon happens to be the start of Dhu al-Hijjah, the 12th month of the Islamic calendar year, and one in which the pilgrimage to Mecca traditionally takes place. For Jews it's the first day of Av, when according to the Biblical book of Ezra, Jewish people returned to Israel after exile in Babylon.
The best time to see Saturn
According to NASA's Skycal, Saturn will be in opposition at 5:33 p.m. EDT (2133 GMT) on the night of the new moon. Opposition means the planet is almost exactly on the opposite side of Earth's sky as the sun. In New York City, for example, Saturn rises at 8:17 p.m. and the sun sets at 8:22 p.m. local time. Not only will Saturn be well-placed for viewing all night long, but the planet will also be at its biggest and brightest of the year.
As Earth passes directly between Saturn and the sun, our planet will also make its closest approach to Saturn of 2020. That closest approach will occur about five hours after opposition, according to EarthSky.org. At that time, Saturn will be 8.99 astronomical units (AU), or 8.99 times the average Earth-sun distance, away from our planet. At its farthest, Saturn's distance from Earth is about 11 AU.
Located in the constellation Sagittarius, Saturn will be at its highest at 1 a.m. local time, when it crosses the meridian, and it will be about 29 degrees above the southern horizon, according to Heavens-Above.com calculations. The planet will be shining at magnitude 0.1, or about as bright as Rigel, the brightest star in the constellation of Orion, the hunter. (Magnitude is a measure of brightness used by astronomers, with smaller numbers indicating brighter objects.)
More visible planets
On the day of the new moon, Venus and Mercury will both be "morning stars." In New York City, Venus rises at 2:52 a.m. local time, followed by Mercury at 4:22 a.m. local time. That puts Venus in an easy position to see ahead of sunrise, which is at 5:42 a.m. local time. By 5 a.m. Venus will be a good 23 degrees above the eastern horizon in the constellation of Taurus, the bull, and bright enough that it's easy to spot.
Mercury will be a harder target; at 5 a.m. it is only 6 degrees above the horizon. If you have a clear and flat view eastwards, one way to track Mercury is to look for Venus, a bright white star-like object, and then for Aldebaran, the brightest star in Taurus, which will be to the right and slightly upwards.
Aldebaran is recognizable because it will look distinctly yellow-orange next to Venus. Draw a line between Aldebaran and Venus to the left; you should hit Mercury, which will be shining at magnitude 0.7, about as bright Aldebaran.
Mars will also be a predawn object on July 20, as it rises at 11:45 p.m. and sets about six hours after sunrise. Since it is in the constellation Cetus, which is relatively faint, Mars will be obvious to viewers as it will appear to be the brightest "star" and have a distinct red hue.
Jupiter will also be visible almost all night; it appears to the right and above Saturn as the latter rises. Jupiter rises at 7:53 p.m. local time in New York, and becomes visible after the sun sets. By around 10 p.m. local time the two will be visible as a pair to the left of the main stars of Sagittarius.
Visible constellations
On the night of the new moon, observers in mid-northern latitudes will see the true summer sky. High in the east, by 10 p.m. local time, the constellations of Lyra, Cygnus and Aquila will show the asterism the Summer Triangle, consisting of Vega (Alpha Lyrae), Deneb (Alpha Cygni) and Altair (Alpha Aquilae). Vega, one of the brightest Northern Hemisphere stars, reaches near the zenith — the point in the sky directly overhead — near the midnight hours. The Milky Way, marking the edge of our galaxy, runs right through the middle of the Summer Triangle and is visible from any site that lacks city lights, and one can see it stretch from Sagittarius in the south to Cassiopeia in the north.
Also at about 10 p.m. local time one can see the constellations of Pegasus and Andromeda rising in the east. Andromeda was the legendary daughter of Cassiopeia, the "W"-shaped constellation that will be exactly on the other side of Polaris, the North Star, from the Big Dipper (which between 10 p.m. and 2 a.m. will be on the left side of Polaris, while Cassiopeia is on the right.)
According to Greek mythology, Andromeda was to be sacrificed to Cetus, the whale, but Perseus — whose constellation will be rising in the northeast by 10 p.m. and be fully visible by about midnight — rode in to the rescue on Pegasus, the winged horse. Cepheus, Cassiopeia's husband, is just to the east of Cassiopeia, and both are visible in the sky together for most of the year in the Northern Hemisphere.
On the night of the new moon, since the sky will be free of any interfering moonlight, by midnight the Andromeda constellation offers a naked-eye view of the Andromeda galaxy, which can be spotted away from city lights as a smudge of light in Andromeda. Find it by finding the "Great Square" of Pegasus and looking for the star on the right corner; Andromeda is two trailing curves of stars with the Andromeda galaxy appearing as a smudge above the uppermost line.
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