A Fantastic First Quarter Moon, Mars Attacks Already, and mid-July Deep Sky Delights!
Some mid-July Sights
Here is a sampling of some celestial sights available in mid-July when the young moon is also in the sky.
Ophiuchus (the Serpent-Bearer) is a large constellation located just west (to the right) of the Milky Way and north of the ecliptic. His large body, nearly three fists diameters high and 1.5 fists wide, features a flat bottom, tapered sides, and pointed top — just like a Dalek from Doctor Who. He even has a disrupter extending eastward (to the right) from the bright star Cebalrai! After dusk, the constellation is positioned halfway up the southern sky, above Scorpius (the Scorpion), and tilted slightly to the left (east).
One of the serpent-bearer’s legs extends down to the lower left, as if he’s dipping a toe into the Milky Way. His leg also crosses the ecliptic, making Ophiuchus the 13th constellation that the sun passes through during the year (in December, annually). He should be part of the Zodiac! This constellation, especially its lower (more southerly) region, is loaded with more than a dozen globular clusters, the spherical collections of old, tightly packed stars that orbit our galaxy. The brighter globular clusters are Messier 9, Messier 10, Messier 12, Messier 14, and Messier 107. From a dark sky location, you can see them in binoculars, where they will appear as a small fuzzy patch — very comet-like. (That’s why Charles Messier included them in his list of nuisance objects that aren’t comets.) In a backyard telescope, each globular cluster resembles a pile of salt spilled on a black cloth.
The False Comet, also known as NGC6231 and Caldwell 76, is a large and bright open cluster of young blue stars in the constellation of Scorpius (the Scorpion). The pretty cluster reaches a maximum elevation just above the southern horizon at around 10:30 pm local time in mid-July. Under dark skies the cluster will appear to unaided eyes as a grouping of bright stars centered less than a finger’s width above the wide double star designated Zeta Scorpii, where the scorpion’s tail bends sharply eastward (to the left). Look above the cluster for an elongated, comet-like stream of stars extending northward for up to a palm’s width. To see it, you’ll need a very low southern horizon free of lights. Observers in more southerly latitudes will have the advantage of seeing the object much higher in the sky.
Mid-July evenings bring us one of my favorite asterism in the night sky, the Teapot in Sagittarius (the Archer). This informal star pattern, visible with unaided eyes, features a flat bottom formed by the stars Ascella on the east and Kaus Australis on the west. It has a triangular, pointed spout on its west side, marked by the star Al Nasl, and a pointed lid marked by the star Kaus Borealis. (This summer, yellowish Saturn is sitting about three finger widths directly above Kaus Borealis.) The stars Nunki (higher) and Tau Sagitarii (lower) make up its’ handle. Nunki is a hot blue star with a surface temperature of 20,000 K located 225 light-years from us.
You can look for the Teapot low in the southeastern sky as soon as it’s dark. The asterism reaches maximum height above the southern horizon around midnight, when it will look as if it’s serving its hot beverage — with the Milky Way’s “steam” rising above the spout. The star names Kaus Borealis and Kaus Australis come from Arabic phrases that mean “northern bow” and “southern bow”, referring to the Archer’s weapon.
The very first stars to pop into view in mid-July evenings are the bright, white stars of the Summer Triangle asterism. Vega is the higher up, in Lyra (the Harp). Deneb sits to its lower left in Cygnus (the Swan), and Altair sits to its lower right in Aquila (the Eagle). The trio is already halfway up the eastern sky by nightfall and pass the zenith after midnight. This annual feature of the summer sky will remain visible all the way until the end of December! At magnitude +0.03, Vega is the brightest star in the summer sky, mainly due to its relative proximity to the sun of only 25 light-years. Altair is only 17 light-years from the sun, but Deneb is a staggering 2,600 light-years away; but still very bright because of its greater luminosity. Once it’s fully dark, notice that Milky Way passes through Deneb.
The Moon and Planets
The Moon begins this week as a gorgeous waxing young crescent visible over the western horizon after sunset. Tonight (Sunday) the moon will take up a position between Venus and Regulus, the brightest star in Leo (the Lion). The moon will sit 1.5 finger widths west (to the right) of Venus and four degrees east (to the upper left) of the naked-eye star. As soon as you spot the moon in the bright early evening sky, try and find Venus and Regulus on either side of it using binoculars. But take care to avoid the sun!
For the rest of the week, have your binoculars and telescope handy — because this is the week of the moon’s monthly cycle when the sun slowly rises to its near-side surface, painting the lunar terrain with dramatic black shadows and brightly lit mountains and crater rims. The shallow-angled sunlight along and near the terminator (the diving line between the lit and dark sides) will also enhance subtle features on crater floors — ridges and cracks that tell the moon’s geological history. And new regions get this treatment every night as the moon waxes fuller.
As the week rolls on, the moon will wax fuller and pass through the dim constellation of Virgo (the Maiden). It will reach its First Quarter phase on Thursday afternoon. At that time it will be positioned at an angle of about 90° from the sun and will appear as a half illuminated orb. The next night, the moon will pass three finger widths above bright Jupiter. The two objects will cross the sky together until Jupiter sets around 1 am local time. Finally, on the coming weekend, the gibbous moon will land above the claws of Scorpius (the Scorpion).
This week, speedy Mercury will finish up a medium-quality visit for Northern Hemisphere observers. The planet can be spotted sitting low over the northwestern horizon for a brief period after sunset. Binoculars will be needed to pull it out of the evening twilight. Scan the sky about a fist’s diameter to the left of where the sun went down. The best time to look is between 9:30 and 10 pm local time. You’ll need a low open horizon because the planet will be only a few finger widths above the horizon (or less). Viewed in a telescope, the planet will exhibit a waning illuminated crescent that is only 30% full.
Venus continues to gleam in the western evening sky this week until 11 pm local time, although the descending evening ecliptic is now pulling Venus lower each night. Venus is continuing to swing away from the sun and increase in brightness! In a small telescope, the planet’s disk will exhibit a waning gibbous (62% illuminated) phase.
Jupiter continues to be the object you will see shining very brightly in the southern sky after dusk this week. During the evening it will move west and descend — setting in the west-southwest after 1 am local time. The bright star sitting just to the lower left of Jupiter is Zubenelgenubi, the brightest star in Libra (the Scales). In binoculars, the star splits into a pair of stars. In your binoculars can you also see Jupiter’s four Galilean moons flanking the planet?
On Sunday, July 15, the little, round, black shadow of Jupiter’s moon Io will complete a crossing (transit) of Jupiter’s disk at 10:24 pm that starting at 8:10 pm (in twilight). On Sunday, July 22, Europa’s shadow will begin a transit at 10:46 pm that ends when Jupiter sets at about 1 am. A reasonable backyard telescope will show the black shadows, but a very good telescope is needed to see the moons themselves. More shadow transits are available in other time zones around the world.
The Great Red Spot (or GRS, for short) takes about three hours to cross Jupiter’s disk. But the planet’s 10-hour rotation period (i.e., its day) means that the spot is only observable from Earth every 2–3 nights. If you’d like to see the GRS, use a medium-sized telescope (or larger). You’ll have your best luck on evenings with steady air — when the stars are not twinkling too much. The best times to see it this week are: Monday, July 16 at 11:33 pm, Thursday, July 19 at 9:03 pm (in twilight), and Saturday, July 21 at 10:43 pm. All times are given in Eastern Daylight Time (EDT), so adjust for your local time zone. Try to look within an hour before or after the times I’ve given.
Yellowish Saturn is visible nearly all night long this week — and it’s only recently past its brightest and largest appearance for the year. Look for Saturn as a medium-bright yellowish object shining over the southeastern horizon once the sky has darkened. The ringed planet spends the summer of 2018 just east (to the left of) the Milky Way, and just above the Teapot-shaped stars that form Sagittarius (the Archer). Saturn will reach the highest point over the southern horizon at just after midnight local time. It will remain visible until it sets in the southwest just before 4:30 am local time.
Mars alert! Mars is that crazy-bright red object shining over the southeastern horizon after it rises in the late evening. It will reach its highest position, over the southern horizon, around 2:30 am local time (the best time to view the planet in a telescope because it will be shining through a bit less of the Earth’s distorting atmosphere). A small telescope should already be able to reveal some variations in brightness on its disk, although a global dust storm has enveloped the planet — hiding all but the major features. We’re hoping that the storm abates soon. But don’t wait to begin your viewing of Mars — it’s already fairly close.
Mars will be rising about 5 minutes earlier every night for the next couple of weeks because the Earth is starting to pass the planet on the “inside track”. Closest approach to the Earth occurs on July 31, when it will be only 0.385 astronomical units (35.79 million miles or 57.6 million km) from the Earth. That translates to only 3 minutes and 18 seconds for radio signals to reach the planet. It won’t be this close again until 2035! At closest approach, the red planet will shine with a visual magnitude of -2.8, and even a modest telescope should reveal its 24.2 arc-minute diameter disk.
Blue-green colored Uranus is visible in binoculars and telescopes for a few hours each morning, if you know where to look. You’ll find it in the eastern sky between 1 am local time, when it rises, and the onset of morning twilight. The planet is located about four finger widths to the left of the modestly bright star Torcular (Omega Piscium), which is above the “V” where the two cords of Pisces (the Fishes) meet. The major asteroid Juno is about a palm’s width below Uranus, in the same region of sky.
Distant blue Neptune, among the modestly-bright stars of Aquarius (the Water-bearer), is observable in telescopes in the eastern sky after it rises after 11:15 pm local time. This week, look for the planet with magnitude 7.9 sitting one finger width to the right of the naked eye star Phi (φ) Aquarii and about 4.5 finger widths to the left of brighter Hydor (Lambda Aquarii).
Astronomy Skylights for this week (from July 15th, 2018) by Chris Vaughan.
Keep looking up to enjoy the sky! I love getting questions so, if you have any, send me a note.