What’s Up? Constellations, Planets, and Astronomical Events Visible in August 2023
Happy August! The days are long and hot, but the nights have perfect weather for stargazing. The days are steadily growing shorter since the solstice has passed. The sun rises around 6:40 am and sets at 8:30. As each day passes, the amount of daylight changes by approximately 2 minutes and 15 seconds. This rate of change will continue to increase until the equinox next month, but the nights will continue to get longer until the winter solstice in December.
Once in a blue moon is here at last! When two full moons occur in the same calendar month, the second is called a blue moon. This phenomenon is possible because the time it takes for one full cycle of the moon’s phases or one orbit of the moon around the Earth, is 29.5 days. It also happens that both of the full moons this month are supermoons! The full moon is continuing to occur when the moon is at its closest point to Earth, causing it to appear larger and brighter than usual. The first full supermoon occurs on August 1st, which is known as the Sturgeon moon, as this is when the Native Americans would catch the fish in the Great Lakes. The second full moon has many titles: The full super-blue moon. However, since it is also in August, it would not have another nickname like the other full moons have, since there are only 12 nicknames used to describe the full moons of the year.
Despite its nickname, the blue moon does not actually have a blue hue. The name comes from the 16th century saying “when the moon is blue” meaning something is impossible; although it is true the moon can have a blue or green tint due to dust in the atmosphere. After a real blue-tinted moon was observed after a volcanic eruption in Indonesia in the late 1800s, the phrase shifted to mean a rare event. The term “blue moon” was only used to describe the occurrence of two full moons starting in the mid-1900s. If you were ever wondering how often “once in a blue moon” is, it is about once every 33 months, or 2.75 years.
The new moon occurs on August 16th; this day and the surrounding days when the moon is in its crescent phases are the best time to stargaze if the weather permits. Especially since the full moons are supermoons, their brightness will make observing faint celestial objects very difficult.
There is a meteor shower occurring this month! The Perseids shower is a popular meteor shower known for its high frequency of bright meteors that should be visible even from light-polluted areas. The shower runs annually from July 17th to August 24th, but its peak is on the night of August 12th this year. At its peak, it is expected to produce around 60 meteors per hour. The shower will radiate from the constellation Perseus, which can be found near the northeastern horizon at sundown. The constellation will rise further above the horizon as the night goes on, so the best viewing will be near midnight or later at a dark sky site. However, the waning crescent moon provides very little light to interfere with the show, so viewing is still possible from light-polluted areas.
The Perseid meteor shower comes from the debris of the comet 109P/Swift-Tuttle. This comet was discovered in 1862 and orbits the sun every 133 years. Sadly, we will never see the comet again in our lifetimes, but we will continue to enjoy the meteor shower caused by its remnants every year.
Mercury is visible once again. As the innermost planet in our solar system, Mercury orbits the sun in only 88 days, but it is also too close to the sun most nights. Only during its greatest elongation will it be visible. This is when the planet is at its farthest point from the Sun in our sky, and even at this time it is still difficult to observe. Mercury will be in greatest eastern elongation on August 10th. This means the planet will be visible in the western sky for a few moments after sundown.
Venus is currently difficult to view. It is directly in front of the sun for most of the month, but it will be visible in the early morning before sunrise at the end of the month. Mars is also too close to the Sun to observe. It won’t be easily visible again until next year.
Unlike the terrestrial planets, Jupiter and Saturn are more easily visible this month. Jupiter is perfectly visible once it rises after midnight, and Saturn is in opposition on August 27th. Opposition means the planet is opposite the Sun in our sky. Saturn will rise at sunset, and set at sunrise, meaning it will be visible all night.
As always, the ice giants Uranus and Neptune are difficult to observe without binoculars or a telescope. Uranus rises just past midnight, only slightly to the east of Jupiter for the whole month. Neptune rises at 10:00 pm and will be found between Jupiter and Saturn in the constellation Pisces
The most useful constellations for night sky navigation are the Big and Little Dippers. In Ohio, and further north, the Dippers never set below the horizon. They are in the northern sky all night long and all year long. Stars that never set are called circumpolar stars. Polaris, the North Star, is in line with Earth’s north pole. As Earth rotates, Polaris stays still in the northern sky, and all the stars appear to move around it. This becomes apparent when astrophotographers take exposures of the sky that last hours; the stars leave a trail that shows their path around Polaris. Because of this, constellations like Draco and Ursa Major/Minor are useful all year round.
The Big Dipper is likely the most common constellation in the northern sky; however, it is not a constellation. There are only 88 officially recognized constellations, but anyone can connect the dots in the sky to make a shape. These shapes are called asterisms. Ursa Major is a recognized constellation, but the ladle of the Big Dipper is only a section of the constellation that has been given a nickname, therefore it is an asterism. The Big Dipper is notable because it is made up of bright stars that can be seen even in light-polluted cities, and its stars are helpful to guide a stargazer to other constellations. For instance, the two stars at the edge of the ladle point directly to Polaris, which is the tip of the handle of the Little Dipper. Winding between the two Dippers is Draco the Dragon. Another example is that the handle of the Big Dipper arcs over to the bright star Arcturus in the constellation Böotes (pronounced Boh-oh-teez). These are only a few examples of using guide stars to navigate through the sky.
- Sturgeon Moon: https://www.bbc.com/news/uk-england-nottinghamshire-62517894
- Image Credit: Graham Wiffem
- Blue Moon: https://www.space.com/15455-blue-moon.html
- Image Credit: Herken Herken
- Position Diagram: http://alicesastroinfo.com/2007/01/mercury-at-greatest-elongation-2007/
- Saturn: https://solarsystem.nasa.gov/planets/saturn/overview/
- Perseids Radiant Point: https://earthsky.org/astronomy-essentials/everything-you-need-to-know-perseid-meteor-shower/
- Big Dipper/Little Dipper/Draco/Bootes: https://stellarium-web.org/
- Star Trails: https://fuzzy.photos/astrophotos/42-star-trails-at-the-celestial-pole
- Image credit: Frederick Steiling