At any moment of the day, countless awe-inspiring celestial events are unfolding in the sky. With a universe of options, it can be hard to pin down what to observe. The purpose of this calendar is to provide a peek into what’s happening in the sky and in the world of astronomy in general and provide a quick list of highlights that can jump start your own explorations.
All Month Long: Summer Triangle
Northern Hemisphere observers would be remiss if they did not check out the Summer Triangle currently reigning in the night sky. The popular asterism is, as its name suggests, a simple triangle formed by three brilliant stars – Vega, Altair and Deneb. A resident of the Lyra Constellation and easy to find in the eastern sky, Vega is a blue-white beauty that is the brightest in the trio and the fifth brightest star in the sky. A member of the Cygnus Constellation, Deneb lies to the lower left of Vega. Although the blue-white supergiant is the least bright member of the asterism, it is actually the most luminous. Its distance is what gives it its third place ranking. To the lower right of Vega, you can find the fast-rotating Altair, an oblate spheroid that is the brightest star in the Aquila Constellation. Although they are worthy sights, these three stars are not the only reasons to check out the Summer Triangle. Another notable stellar offering is the amazing double star Albireo that awaits in the middle of the triangle. When viewed through a telescope, this point of light becomes a wonderful contrasting pair made up of a blazing golden yellow star and a subtle blue star. Deep sky favorites lurking in the neighborhood include the appropriately named Ring Nebula (M57), which blooms around a bluish dwarf, and the hourglass-shaped Dumbbell Nebula (M27), which was the first planetary nebula ever discovered. In addition to all of these treats, a grander sight will be revealed under a dark sky when you see the dusty, glowing Milky Way cutting a stunning swath through the midst of the Summer Triangle.
July's Planetary Round-Up
The latter half of July will offer up several lovely pairings between the Moon and our planetary pals. This cycle of conjunctions will kick off with a visually close encounter of the Moon and Saturn on July 16, when the two will have a pre-dawn meet-up in the Pisces constellation. On July 21, a barely-there Moon will snuggle up to Venus in the Taurus constellation before it gets cozy with Jupiter in the pre-dawn hours of July 23. As it emerges from the New phase of the lunar cycle around June 28, the extremely thin Moon will meet up with Mars in the evening sky. In each instance, the Moon and its mate should easily be seen by the naked eye or through a binocular.
July 4 – Mercury at Greatest Elongation
On July 4, Mercury will be in a prime position for early evening viewing in some locations, especially in the southern hemisphere. Because it is always so close to the Sun, Mercury is usually lost in its glare. But on this day, it will be at its greatest eastern elongation or at its furthest point to the east of the Sun, which puts it in a great observing position shortly after sunset. A clear western horizon is essential for viewing Mercury, which can be found in the Taurus constellation during the event. While Mercury will be visible to the naked eye, a telescope could provide some phase details.
Astrophotographer Marty Hendrix captured this image of Messier 45 with the aid of an Explore Scientific ED80 FCD-100 Triplet Refractor.
July 20 – Crescent Moon Pairs Up with the Pleiades
The thin crescent Moon and the storied Pleiades star cluster with its brilliant blue stars will get visually cozy on July 20. In fact, the pair will be close enough for the Moon to occult some of the cluster's brightest stars, which should be a great binocular target for those with agreeable skies! Also known by the names Messier 45 or the more poetic Seven Sisters, the Pleiades open star cluster has a rich lore that crosses cultures and goes back thousands of years. It is relatively young, having formed within the last 100 million years, and lies relatively close to Earth at about 440 light years away. Found in the Taurus constellation, it consists of more than 1,000 confirmed stars, although an average of only six are visible to the naked eye. A dark sky free of light pollution can help a dedicated observer see around a dozen Pleiades stars, but a good pair of binoculars or a low-power telescope can quickly reveal the more elusive members of this legendary cluster.
Late July – Delta Aquariid Meteor Shower
With the Delta Aquariids set to peak around July 30 and the legendary Perseids on the horizon, meteor shower enthusiasts should be actively scouting out their favorite dark patch of sky. Each year, the Delta Aquariid meteor shower serves as the warm-up act for the highly anticipated August performance of the annual Perseids. At its peak, the Delta Aquariid shower produces 15-20 meteors per hour – a figure that pales in comparison to the average 80 meteors per hour that the Perseid shower can deliver during its peak. However, the Delta Aquariids will be at their pinnacle this year when the Moon is barely a sliver in the night sky. With little interference from the Moon, the Delta Aquariids will be easy to spot as they blaze across the night sky, which will amp up their drama.
With a radiant point in the Aquarius Constellation, the Delta Aquariids begin their annual amble across the sky in mid-July, bloom in late-July and fade out in the third week of August. They can be seen almost everywhere but favor observers in the Southern Hemisphere and the Northern Hemisphere’s tropics region. Like other meteor showers, the Delta Aquariids are the result of Earth’s passage through debris left behind by a comet. However, the exact source comet for this shower has been a matter of debate. The most likely candidate is Comet 96P/Machholz, which was not discovered until 1986. Regardless of where they come from, the Delta Aquariids have established themselves as a meteor shower of note, and the lunar circumstances during this year’s peak have given the Delta Aquariids some much-deserved time in the spotlight. To catch sight of a Delta Aquariid, observers should look at a dark patch of sky about 90 degrees away from the radiant point to see the most meteors. The best viewing time is after midnight in the wee pre-dawn hours. To view the meteors, all you need is your naked eye, a good place to lie down under an open sky and patience.
CONSTELLATION SPOTLIGHT: Scorpius Constellation
With stunning features like Antares and The Butterfly Cluster, the Scorpius Constellation is a striking presence in the Southern Hemisphere sky, and July is the perfect month to take in all that the scorpion has to offer. Visible from 40° North to 90° South, the constellation closely resembles its namesake and encompasses a 497 square degree area close to the Milky Way’s galactic center.
One of its most recognizable residents is the beautiful red supergiant Antares. Generally identified as the 16th brightest star in the sky, Antares is an irregular variable with a red-orange glow that makes it truly pop. Closer observations with a moderate telescope could reveal its blue companion star, which can be highly challenging to discern. While Antares beams at the heart of the scorpion, the multi-star system Shaula marks the tip of the celestial beast’s tail. It is made up of a triple-star system dominated by a Beta Cephei type variable and two companion stars. Other stellar choices include Beta Scorpii, a complex multi-star system disguised as a binary system in some scopes; Theta Scorpii, a yellow giant with a magnitude of 1.87; Pi Scorpii, a triple-star system with an eclipsing pair of blue-white dwarfs; Omega Scorpii, a binary system with a blue-white dwarf and a yellow giant; G Scorpii, an orange giant with an apparent magnitude of 3.21; Eta Scorpii, a yellow-white rapid rotator; and Zeta Scorpii, a naked eye double formed by a highly luminous hypergiant and an orange giant.
In terms of deep sky treasures, Scorpius is home to a number of prominent clusters. The Butterfly Cluster (Messier 6) is an open cluster populated by brilliant blue stars and one impressive orange supergiant. The even-brighter Ptolemy Cluster (Messier 7) lies near M6 visually, and the pair can fit easily into the field of view of a pair of moderate aperture binoculars. Other deep sky targets worth pursuing include, Messier 4, a globular cluster near Antares that is the closest of its kind; Messier 80, a very dense globular cluster that contains several hundred thousand stars; NGC 6302, a planetary nebula with a very complex structure and an apparent magnitude of 7.1; and NGC 6231, which is also known as the Northern Jewel Box cluster.
WANT TO NAVIGATE THE NIGHT SKY WITH EASE?
The Tirion Double-Sided Multi-Latitude Planisphere is a comprehensive sky map for northern hemisphere stargazers located between the equator and latitude 60° north that makes it easy to identify what constellations and major celestial objects are up in your night sky based on the date and time.
This night sky guide, which features maps crafted by noted celestial cartographer Wil Tirion, uses a double-sided design to minimize the distortion that is inherent to any polar-centered projection. This design choice means observers can see truer representations of the constellations located outside the equator (noted by a green line) by simply flipping the planisphere over.
In addition to showcasing constellations, this planisphere indicates the location of notable variable stars, open clusters, nebulae and galaxies. Other features include a line representing the ecliptic, a faint blue band for the Milky Way and a magnitude scale that indicates the brightness of the stars that are shown.
This astronomy planisphere is made of durable plastic that easily wipes clean, and the rotating components are secured with sturdy brass rivets for smooth manipulation. Guidance for using your sky map is printed on the device for quick reference.