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NASA Astronomy Picture of the Day:

How big is planet Earth's Moon? Compared to other moons of the Solar System, it's number 5 on the largest to smallest ranked list, following Jupiter's moon Ganymede, Saturn's moon Titan, and Jovian moons Callisto and Io. Continuing the list, the Moon comes before Jupiter's Europa and Neptune's Triton. It's also larger than dwarf planets Pluto and Eris. With a diameter of 3,475 kilometers the Moon is about 1/4 the size of Earth though, and that does make it the largest moon when compared to the size of its parent Solar System planet. Of course in this serene, twilight sea and skyscape, August's rising Full Moon still appears small enough to be caught in the nets of an ancient fishing rig. The telephoto snapshot was taken along the Italian Costa dei Trabocchi, on the Adriatic Sea.

Photo by How big is planet Earth's Moon

The Qianlong Emperor in Ceremonial Armour on Horseback by Giuseppe Castiglione.

Giuseppe Castiglione, Public domain, via Wikimedia Commons. View source.

NASA Astronomy Picture of the Day:

This colorful telescopic view towards the musical northern constellation Lyra reveals the faint outer halos and brighter central ring-shaped region of M57, popularly known as the Ring Nebula. To modern astronomers M57 is a well-known planetary nebula. With a central ring about one light-year across, M57 is definitely not a planet though, but the gaseous shroud of one of the Milky Way's dying sun-like stars. Roughly the same apparent size as M57, the fainter and more often overlooked barred spiral galaxy at the left is IC 1296. In fact, over 100 years ago IC 1296 would have been known as a spiral nebula. By chance the pair are in the same field of view, and while they appear to have similar sizes they are actually very far apart. At a distance of a mere 2,000 light-years M57 is well within our own Milky Way galaxy. Extragalactic IC 1296 (aka PGC62532) is more like 200,000,000 light-years distant. That's about 100,000 times farther away than M57 but since they appear roughly similar in size, former spiral nebula IC 1296 must also be about 100,000 times larger than planetary nebula M57. Look closely at the sharp 21st century astroimage to spot even more distant background galaxies scattered through the frame.

Photo by Kent Biggs

Male lion (Panthera leo) in Maasai Mara National Park. The Leo astrological sign ends at this time of year.

Byrdyak, CC BY-SA 4.0, via Wikimedia Commons. View source.

NASA Astronomy Picture of the Day:

In this predawn skyscape recorded during the early morning hours of August 13, mostly Perseid meteors are raining down on planet Earth. You can easily identify the Perseid meteor streaks. They're the ones with trails that seem to converge on the annual meteor shower's radiant, a spot in the heroic constellation Perseus, located off the top of the frame. That's the direction in Earth's sky that looks along the orbit of this meteor shower's parent, periodic Comet Swift-Tuttle. Of course the scene is a composite, a combination of about 500 digital exposures to capture meteors registered with a single base frame exposure. But all exposures were taken during a period of around 2.5 hours from a wind farm near Mönchhof, Burgenland, Austria. Red lights on the individual wind turbine towers dot the foreground. In their spectacular close conjunction, bright planets Jupiter and Venus are poised above the eastern horizon.

Photo by Klaus Pillwatsch

A woman from the Koch tribe with a lamb.

Nayeem01771031233, CC BY-SA 4.0, via Wikimedia Commons. View source.

NASA Astronomy Picture of the Day:

What are those curved arcs in the sky? Meteors -- specifically, meteors from this year's Perseid meteor shower. Over the past few weeks, after the sky darkened, many images of Perseid meteors were captured separately and merged into a single frame, taken earlier. Although the meteors all traveled on straight paths, these paths appear slightly curved by the wide-angle lens of the capturing camera. The meteor streaks can all be traced back to a single point on the sky called the radiant, here just off the top of the frame in the constellation of Perseus. The same camera took a deep image of the background sky that brought up the central band of our Milky Way galaxy running nearly vertically through the featured image's center. The limestone arch in the foreground in Dorset, England is known as Durdle Door, a name thought to survive from a thousand years ago.

Photo by Josh Dury

Moray eels (Muraena augusti) and a cleaner shrimp (Lysmata grabhami), Teno-Rasca marine strip, Tenerife, Spain. It belongs to the family of moray eel and is endemic of the Canary Islands, Madeira and Azores. It is non-migratory, and dwells at a depth range of 0 to 250 metres (0 to 820 ft), most often at around 0 to 50 metres (0 to 164 ft). Muraena augusti is active during the night and hides in holes or crevices during the day. It can reach up to 100 centimetres (39 in) length and is a carnivore that feeds on small fishes, shrimps and crabs. Like all other moray eels their vision is poor but their sense of smell extraordinary.

Diego Delso, CC BY-SA 4.0, via Wikimedia Commons. View source.