If you were looking with the eye alone, how far away in space would our planet Earth still be visible?
Here is Earth from 900 million miles away, from the vantage point of the rings of Saturn. Image via the Cassini spacecraft, which has been orbiting Saturn since 2004.
This image was acquired by Cassini on July 19, 2013. How far away from Earth can we be, to see it still with our own eyes? To answer this question, you have to take into account how brightly Earth reflects sunlight. And the sun itself is an important factor. As seen from any great distance, Earth appears right next to the sun; from a great distance, the glare of our local star would make Earth difficult or impossible to see. But spacecraft exploring our solar system have given us marvelous views of Earth.
So imagine blasting off and being about 300 kilometers – about 200 miles – above Earth’s surface. That’s the height at which the International Space Station (ISS) orbits. The surface of the Earth looms large in the window of ISS. In the daytime, you can clearly see major landforms. At night, you see the lights of Earth’s cities.
The planet Saturn shines over the southeast horizon at nightfall on May 15, and then the moon and the star Antares follow Saturn into the sky by around 10 p.m. local time (at mid-northern latitudes). At more southerly latitudes, the moon and Antares rise at an earlier hour. Look for the waning gibbous moon and Antares before going to bed on this night.
Antares, the brightest star in the constellation Scorpius, represents the Scorpion’s beating Heart. Beating? Yes, because from our northerly latitudes we tend to look at Antares low in the south, and the atmosphere causes it to scintillate. Thus Antares, a red star, is know to twinkle fiercely.
Antares is a red supergiant star, whose volume is a few hundred million times greater than that of our sun. If Antares replaced the sun in our solar system, its circumference would extend all the way into the asteroid belt in between the orbits of Mars and Jupiter.
When the full moon rises on Tuesday night, it will technically be a Blue Moon, but not for the reason you might think.
The Blue Moon on Aug. 20 is not the second full moon of August, but actually gets its name from a relatively obscure rule of astronomy. And there are a few other details about the full moon that might surprise you.
Alas, some things have a longer-lasting affect than others. It would have been nice to have pleasant memories of my home in Derwood, but that is not to be. My erstwhile landlord, who fumbled around for two years and cause me more than a little grief, presented my former co-tenant with a BILL for $11, above taking the entire deposit.
I’ve always wondered what Small Claims Court was really like…guess I’m going to find out for myself.
Stay tuned for more developments on the saga I’m code-naming “Evening Sky in Derwood”.