The Night Sky This Month: July 2019

July night sky
Image Credit: Maximilian Teodorescu

In the July night sky, the Summer Triangle dominates the northeast and east celestial heavens. Found among this huge asterism consisting of the constellations Lyra, Aquila, and Cygnus can be found double stars, famous variable stars, as well as nebulae and supernova remnants. The latter includes the Ring (M57) Nebula, the North America Nebula (NGC 7000), and the Veil.

Against the backdrop of the Milky Way, the constellation Scorpius also looks magnificent, with its curvy S-shaped body, set of claws, and pair of “stinger” stars at the tail closely resembling the creature it depicts. Scorpius is one of the oldest constellations, and was known to the Sumerians as GIR-TAB (“the scorpion”) over 5,000 years ago. Just like in astrology, Scorpius lies between Libra to the west and Sagittarius to the east

Meanwhile, the Spring Triangle‘s two brightest stars can be seen in the southwest, with the red giant Arcturus in Boötis and the blue subgiant Spica in Virgo unmistakable as they stand out against their fainter companions.

The Moon In July 2019

Although we see the Moon only in various shades of gray, the truth is that the Moon is actually very colorful, as the above almost-true color image of the Moon demonstrates. The color variations are the result of differences in the geology of different parts of the Moon’s surface. For instance, the blue coloration of the Mare Tranquillitatis (just right of centre) results from the Mare’s high titanium content. Similarly, the reddish coloration of the Mare Serenitatis, which is immediately above and to the left of the Mare Tranquillitatis, is the result of this area’s high iron content.

These color differences may give many newcomers to lunar observation a new perspective of the Moon. However, it should be noted that it is generally not possible to discern meaningful color differences on the Moon’s surface with optical equipment. The best way to highlight parts of the Moon’s surface is through image processing.

The Moon Phases

New Moon First Quarter Full Moon Third Quarter
July 2nd July 9th July 16th July 25th

A partial lunar eclipse occurs in the July night sky on the 16th. Partial eclipses happen when only a part of the Moon passes through Earth’s umbra, which is the darkest part of Earth’s shadow. In this instance, the partial eclipse will be visible from most of Europe, Africa, central Asia, and much of the Indian Ocean.

The Planets In July 2019

This July is not a good time to observe the planets. That’s because some rise shortly before dawn, while others remain very low on the horizon. Nonetheless, for those who want to hunt down the planets in the July night sky, some details of what to expect are given below-

Mercury will be just barely visible low on the west-north-western horizon as the month starts. Although it will shine at magnitude 1.1 and have an angular diameter of 9.4 seconds of arc for much of the month, the Sun’s glare will make it very difficult to spot.

Venus will rise considerably less than one hour before dawn at the beginning at the month. While it will shine at magnitude -3.9, it will not rise above around 4 degrees over the north-eastern horizon. Moreover, Venus will not be visible from the 18th of the month onwards as it becomes lost in the Sun’s glare.

Mars remains visible throughout July, shining at magnitude +1.8, albeit very low on the west-north-western horizon. By month’s end, Mars will set only about 30 minutes or so after sunset. This will make it almost impossible to spot. Moreover, while Mars is just barely visible, its angular diameter will reduce from 3.7 seconds of arc to 3.5 seconds of arc. Therefore, it will be almost impossible to discern any surface details using binoculars or telescopes.

Jupiter was at opposition on the 10th of June, and it will therefore remain visible in the south after sunset. However, even though the planet will shine at magnitude -2.4, it is now moving westwards through the southern-most reaches of the constellation Ophiuchus. This means it is now in the southern half of the ecliptic, and will therefore not rise more than about 14 degrees or so above the southern horizon. Nonetheless, look for Jupiter about seven degrees to the upper leftward of the bright star Antares by month’s end.

If you have access to an atmospheric dispersion corrector, you might be able to observe the Great Red Spot on the planet’s meridian on the following dates and times-

  • July 2nd – 23:37 UT
  • July 7th – 22:45 UT
  • July 12th – 21:52 UT
  • July 14th – 23:31 UT
  • July 26th – 23:25 UT
  • July 31st – 22:33 UT

Saturn will reach opposition on the 9th, and will cross the meridian at about 01:00 BST, at which time it will shine at magnitude +0.1. While it will have an angular diameter of about 18 seconds of arc, the planet is now moving through the constellation Sagittarius, which means that it is now in the southern part of the ecliptic. As a result, Saturn will not rise above about 14 degrees over the horizon, and an atmospheric dispersion corrector will be required to obtain even reasonable views of the planet.

Meteor Showers in July 2019

The Delta Aquarids Meteor Shower is expected to peak in the July night sky on the 28th/29th. The shower is produced by debris trails from the comets Marsden and Kracht. Although it is not of one the especially prolific meteor showers, it is expected to deliver about 20 or so meteors per hour during its peak. Although the waning crescent Moon is not expected to obtrude during the peak hours, it is nevertheless recommended that this shower be observed from a dark spot, since meteors from this shower are generally not overly bright or luminous.

Note that while the radiant is located in the constellation Aquarius, meteors can appear from almost any point in the sky.

Deep Sky Objects to Look For In July 2019

Prominent constellations in the July night sky include Ursa Major almost directly overhead, and Hercules, Lyra, Cygnus, and Ophiuchus towards the south. These constellations all contain large numbers of spectacular deep sky objects, with Hercules perhaps containing more objects that can be viewed with modest amateur equipment than any other constellation that is now visible. Below are some details of a few such objects in Hercules-

The Great Globular Cluster – Messier 13 (M13, NGC 6205)

The Great Globular Cluster
Image credit: NASA

Messier 13 is without any doubt the finest globular cluster that can be seen from the northern hemisphere. It is thought to contain at least 300,000 stars, which gives it an angular diameter of 20 seconds of arc. This equates to an effective diameter of about 145 light years. In 1974, an experimental message was transmitted toward the cluster on the assumption that since the average stellar density was higher in the cluster’s neighbourhood, the likelihood of the message being intercepted by intelligent extraterrestrial life forms would also be high. However, the cluster is located 22,000 light years away, so by the time the Arecibo message arrives at the cluster, it will have moved several of its own diameters away from the target area.

Messier 92 (M92, NGC 6341)

Messier 13
Image credit: NASA

Consisting of several hundred thousand stars, M92 is relatively luminous. Even at a distance of nearly 27,000 light years it shines with an apparent magnitude of 6.3. It is also one of the oldest known globular clusters that are associated with the Milky Way; with an age of about 14.2 billion years, it is thought to be almost as old as the Universe itself. In fact, many investigators believe that given its estimated age, M92 is likely to be among the very first globular clusters to have formed.

Abell 39

Abell 39

At a distance of only about 6,800 light years, Abell 39 is one of the closest planetary nebulae to Earth. It is also one of the largest known planetary nebulae, stretching over about 2.5 light years. The nebula itself has an apparent magnitude of 13.7, while the central star (the bright dot in the center) has an apparent magnitude of 15.5.

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