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By Chuck McPartlin
On Thursday evening, weather permitting, we’ll get some nice celestial views as the Sun sets.
Look to the West to find bright Venus to the right of the thin waxing crescent Moon, just over a day and a half old. This image from Starry Night Pro shows the pair as they will appear at 8 PM PDT, about 3 minutes after sunset.
Binoculars or a telescope will enhance your view of the Moon, showing the craters and plains etched with shadows as the Sun rises along the terminator, the dividing line between day and night on the Moon. Here’s what you’ll see, courtesy of NASA’s Scientific Visualization Studio.
The Moon will be 224,142 miles away, so you’ll be looking back in time about 1.2 seconds. For Venus, the distance will be about 126 million miles, so you’ll be seeing it the way it was 11 minutes and 17 seconds ago. If the seeing is steady, and you’re looking through a telescope, see whether you can detect that Venus is in a fat gibbous phase. In the coming months, as it swings around the Sun and heads toward us, it will wane into a thin crescent even as it gets brighter because of its proximity. Seeing stuff like that got Galileo in big trouble.
Venus is just a little bit smaller than the Earth, and looks so bright because it is covered in reflective clouds, and is only about two thirds of our distance from the Sun. Its atmosphere is so thick that if you were standing on the surface of Venus, you would feel like you were 3,000 feet underwater on the Earth. The atmosphere is mostly carbon dioxide, a greenhouse gas, so the entire surface of Venus is at 800 degrees Fahrenheit. Unless we wise up and stop dumping huge amounts of CO2 into our atmosphere, we’re likely to end up like Venus.
After looking at the Moon and Venus, do an about-face, and look for Jupiter, low in the East Southeast sky. Jupiter is just past its closest point to us for the year, so it will be big and bright, though not as bright as Venus. Jupiter will be about 410 million miles away, or 36 minutes and 40 seconds in the past. It is the biggest planet in our solar system, with a volume of about 1300 Earths. It looks like a giant double cheeseburger through a telescope because of its two dark cloud bands.
Jupiter has 69 known moons, and it has four bright moons that you should be able to see in binoculars. The big four are Io, Europa, Ganymede, and Callisto, in order of their distance from Jupiter. They are also known as the Galilean Moons, since Galileo saw them first in 1610. Here’s a Sky Safari view of their configuration at 8 PM.
Io and Europa are about the size of our Moon. Io is rocky and volcanic, while Europa has a young icy surface covering a salt water ocean with more water than there is on Earth. Ganymede is icy with a rocky core, and is the biggest moon in the solar system, about 1.5 times the diameter of our Moon, and bigger than the planet Mercury. Callisto is smaller than Ganymede, but bigger than Io and Europa. It seems to be a relatively fluffy, undifferentiated mix of rock and ice.
You’re welcome!
NB: The SVS image of the moon alluded to at the end of the third paragraph got removed from the text and used as the header image.
Thank you for all the illuminating info. I will enjoy looking at Jupiter, thinking about how my view of it takes nearly 37 minutes to arrive here. Wow. Hard to wrap one’s mind around some of these facts. I laughed about Venus and “Seeing stuff like that got Galileo in big trouble.” Thanks again, Chuck.