Admin and Founder of ‘The Secrets Of The Universe’ and former intern at Indian Institute of Astrophysics, Bangalore, I am a science student pursuing a Master’s in Physics from India. I love to study and write about Stellar Astrophysics, Relativity & Quantum Mechanics.
It’s the month of the best meteor shower of the year. The month when two gas giants of the solar system are on the opposite the Sun, the month with the only Blue Moon of the year, and the month with rare planetary conjunction. August 2021 is full of exciting astronomical events that you should not miss.
August 2: Saturn at opposition
In celestial mechanics, a planetary opposition occurs when the Earth lies between the Sun and the planet, with Earth being on the same side of the planet, as shown below.
Thus on August 2, Sun, Earth, and Saturn will almost align, with Earth in the middle. This optimal positioning occurs when Saturn is almost directly opposite the Sun in the sky. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is the highest in the sky at the same time. At around the same time that Saturn passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest and largest. However, Saturn’s orbit lies far out in the solar system, at 9.5 AU, and hence the angular size doesn’t vary much over the course of conjunction and opposition.
Opposition marks the middle of the best time of year to see a planet. The ringed planet will be visible shortly after the sunset, around 20:00. For observers in the northern hemisphere, Saturn will rise in the south-east direction in the constellation of Capricornus. It will reach its highest point in the sky at 00:30, 42° above the southern horizon. It will become inaccessible around 04:56 when it sinks below 10° above the south-western horizon. The apparent mag of Saturn will be +0.2, making it fairly bright. You can use these space apps to locate Saturn according to your place quickly.
August 2: Moon at apogee
The Moon will reach its farthest point in its elliptical orbit around the Earth, appearing slightly smaller than normal.
August 8: New Moon
The Moon will pass too close to the Sun and remain hidden in its glare for a couple of days. It’s a chance to see faint star clusters, nebulae, and galaxies.
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August 10-11: Moon, Mars, and Venus
On August 10 and 11, the waxing crescent Moon will pass close to Venus and Mars. The three celestial objects will be in the west and can be seen at dusk. Venus will be the bright celestial body after the sunset, only after the Moon. Mars will be difficult to observe due to its proximity to the Sun.
August 12: Perseid meteor shower
The Perseid meteor shower is one of the three top meteor showers of the year, the other two being the Geminids and the Quadrantids.
A meteor shower is a celestial event in which several meteors appear in the sky. Meteor showers take place when Earth comes in the path of the stream of debris from a comet. Each time a comet swings by the Sun in its orbit, some of its ice vaporizes, and a certain amount of meteoroids will be shed. The meteoroids spread out along the entire orbit of the comet to form a meteoroid stream, also known as a “dust trail” (as opposed to a comet’s “gas tail” caused by the tiny particles that are quickly blown away by solar radiation pressure).
This dust trail follows the orbit of the parent comet. When Earth passes through the orbit of this dust trail, these particles interact with the atmosphere and what we see is a spectacular show of meteors: a meteor shower.
The Perseid meteor shower is an annual shower that peaks in August. The parent body associated with the Perseids is the comet 109P/Swift Tuttle. This comet has a highly eccentric orbit. Its orbit takes it outside that of Pluto at the farthest distance and inside that of Earth at the nearest distance. Swift Tuttle takes 133 years to orbit the Sun. Every time this comet passes through the inner solar system, the sun warms and softens up the ices in the comet, causing it to release fresh comet material into its orbital stream.
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Every meteor shower has a point called radiant associated with it. This is the point from where all the streaks appear to originate. Although the streaks can appear anywhere in the sky, it is best to look for them near the radiant. The radiant of the Perseid meteor shower lies in the constellation of Perseus, hence the name Perseid meteor shower.
The best time to catch the shower is on August 12, before dawn. Make sure to look up in the sky on the nights of August 11, 12, and of course, 13. The best displays of the shower will be from midnight to dawn.
If you are lucky, the evening sky might offer you an earthgrazer – a loooooong, slow, colorful meteor traveling horizontally across the sky. The best chance to catch an Earthgrazer is near the horizon.
Lastly, remember the words of a wise man: “Meteor showers are like fishing. You go. You enjoy the night air and maybe the company of friends. Sometimes you catch something.”
August 17: Moon at perigee
The Moon will reach its closest point in its elliptical orbit around the Earth, appearing slightly bigger than normal.
August 19: Conjunction of Mercury and Mars
A conjunction is a celestial event in which two celestial objects appear close to each other as seen from the Earth. For example, if the conjunction involves Jupiter and Saturn, it is known as the Great Conjunction (which occurred on 21 Dec 2020). On August 19, Mercury and Mars will pass within 0°04′ of each other in the constellation of Leo. Because of their vicinity to the Sun, the two planets will be challenging to see with naked eyes. They will be in the west at dusk. Please do not point your telescopes near the Sun. You may end up damaging your eyes.
August 20: Jupiter at opposition
About three weeks after Saturn’s opposition, Jupiter will align with the Sun and the Earth. Jupiter will make its closest approach and will shine brightly in Capricornus. After Venus sets in the west, Jupiter will be the brightest speck of light in the sky. shining at mag -2.9. As seen through a telescope, Jupiter will appear bigger as compared to the rest of the year. However, this increase in angular diameter won’t be noticeable with naked eyes. Look for the gas giant in the east as soon as the dusk sky fades. It reaches its highest point in the sky around midnight and sets in the west at dawn. The conjunctions of Jupiter and Saturn are the flagship planetary events this month.
August 22: Blue Moon
The second Full Moon of a month is commonly known as the Blue Moon. Such an event generally occurs on the last couple of days of the month. However, there is another definition of a Blue Moon. It can also be the third of the four Full Moons in a single season. A season is a period between a solstice and an equinox. The Blue Moon of August will be of this sort.
Note that the Moon won’t appear blue in color as seen from the Earth. Such images are developed using blue filters. The Moon will appear in its usual hue.
August 2021 – Planet Round-up
Mercury
Mercury will pass behind the Sun and will remain hidden in its glare this month. It is currently transitioning from an evening to a morning object.
Venus
Venus dazzles in the western sky at dusk. At an apparent magnitude of -3.92, Venus is the brightest speck of light in the sky after sunset. Thus, it becomes accessible as soon as the dusk sky fades and sets in the west about an hour and a half after the Sun.
Mars
The distance between Mars and Earth is increasing daily as the Red Planet’s orbit carries it to its aphelion later this year. As a result, Mars will remain hidden in the Sun’s glare throughout the month.
Jupiter
While two of the three inferior planets remain out of sight, the gas giants Jupiter and Saturn will put up a spectacular show. Jupiter will be at the opposition on August 20. Look for it in the west as soon as the dusk sky fades. One can see the four Galilean moons – Ganymede, Io, Europa, and Callisto through a telescope.
Saturn
The month will begin with the opposition of Saturn on August 2. The alignment of the Sun, Earth, and Saturn will bring the ringed planet close to us. As a result, Saturn will shine the brightest in August compared to other months of the year. It is still close to Jupiter. The latter, however, is brighter than Saturn.
Uranus
Just like Jupiter and Saturn, Uranus is heading for its opposition later this year. Uranus is currently visible as an early morning object in Aries. Since it has an apparent magnitude of 5.84, it won’t be visible with naked eyes. You will need a telescope to spot the planet.
Neptune
Neptune is currently emerging from behind the Sun, and it rises around midnight in Aquarius. It is then lost to the morning twilight. Therefore, you will need a telescope to spot Neptune.
You can use these space apps to locate all the planets.
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