Astro Bob: Copernicus turns to meet rising sun

Watch the sun rise over one of the moon's most impressive craters Thursday night, July 7.

Copernicus at sunrise
The first rays of the rising sun set the western rim of the crater Copernicus aglow May 13, 2019. We'll see the crater under similar lighting conditions Thursday night, July 7.
Contributed / Roger Hutchinson
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I'm in love with Copernicus . Not the Polish astronomer, although he sure had the right idea about the layout of the solar system with the sun in place of the Earth at center. No, I'm talking about the lunar crater named for him.

Located just northwest of the center of lunar near side, it's a big bulls-eye 58 miles (93 kilometers) across. If someone built a bridge across this giant hole, it would take about an hour to make the crossing.

Copernicus on terminator
Thursday evening, July 7, from twilight onward, you can watch the sun rise over the crater Copernicus in a pair of binoculars or a telescope. In a telescope you'll see sunlight touching the crater's western wall and central peaks first. During the night, the crater will slowly fill with sunlight.
Contributed / Virtual Moon Atlas

On Thursday night, July 7, Copernicus will appear astride the lunar terminator, the line that divides the sunlit part of the moon from the part that's still in darkness. As the moon orbits the Earth, the terminator sweeps across the surface at 9.6 miles an hour (15.4 kilometers per hour). That's about the same speed as a beginner averages during a one-hour bicycle ride. In the same amount of time, observers can see changes in the illumination of craters and mountains with their own eyes.

Copernicus from orbit
NASA's Lunar Reconnaissance Orbiter took this photo of Copernicus from lunar orbit. Note the crater's terraced walls caused by slumping due to gravity. The central peaks formed during the rebound of the floor after impact. The region around Copernicus bears the scars of rupture and melting that occurred in the moments after impact.
Contributed / NASA, GSFC, Arizona State University

Depending on your time zone, the lighting on Copernicus will vary somewhat Thursday evening. Observers on the East Coast will see it more of it submerged in darkness than those living on the opposite coast. My absolute favorite Copernican moment is catching the crater completely engulfed in shadow with only its circular rim etched by the rising sun. Maybe that will happen tonight. I know it will for someone.

Copernicus peaks
Copernicus crater's central peak casts a long shadow to the west over a floor flooded with melted rock that hardened to form today's spectacular landscape. The scene is 4,400 feet (1350 meters) across.
Contributed / NASA, GSFC, Arizona State University

As the sun climbs higher over the lunar landscape and the terminator draws back, sunlight spills down the crater's walls until it illuminates the floor and central mountain peaks, the highest of which soars to 3,900 feet (1.2 kilometers). Many times I've imagined standing on top of that mountain, the sun glaring off to the east in a star-filled sky with the crater below me still shrouded in darkness.


Lunar impact
In this illustration asteroids bombard the moon and carve out the craters that we still see to this day. Many of the impacts occurred between 3.8 billion and 4.1 billion years ago. The impactor that created Copernicus struck about 800 million years ago.
Contributed / NASA, LRO

Copernicus formed during the impact of a small asteroid about 800 million years ago. The collision dug out a capacious hollow and flung fragments of lunar crust far and wide. Upon landing, the shards excavated their own craters, exposing fresh rock and dust from beneath the surface to create a spectacular spider web of bright rays with Copernicus at its center. The rays are subtle in low light, but really jump out closer to full moon. Consider a return visit to the crater at that time, when the rays will be obvious through binoculars.

Telescope viewers will also see additional detail like the upraised, hummocky terrain surrounding Copernicus that resemble wrinkles around the eyes — a testament to the incredible forces unleashed when one massive body strikes another at high velocity.

Battered, airless and to our knowledge, lifeless, the moon is truly an alien world. Yet we can see it in rich detail right from our own backyards.

Read more from Astro Bob
The Red Planet is only 50.6 million miles away — almost walking distance! It won't get this close again until May 2031.

"Astro" Bob King is a freelance writer for the Duluth News Tribune.

"Astro" Bob King is a freelance writer and retired photographer for the Duluth News Tribune. You can reach him at
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