Wonders of the universe: a solar eclipse on Jupiter

NASA released a photo of a solar eclipse on Jupiter. In the tweet below, you can see the moon Io casting a large shadow on the gas giant. Because the Sun is much smaller as seen from Jupiter, the shadow cast by Io is much sharper than those cast by our own Moon. Because Jupiter is so far from the Sun, Io looks four times as big as the Sun as seen from Jupiter's perspective.

Jupiter's North Equatorial Belt and the Shadow of Io, @NASAJuno Perijove 22 - https://t.co/xrLr9x45ks pic.twitter.com/W1ABDQtpVB

— Kevin M. Gill (@kevinmgill) 16 september 2019

Why is the Moon’s shadow on Earth fuzzy while Io’s shadow on Jupiter is so sharp? Io is so big & close that it more than blocks the Sun (it appears 4x as big as the Sun from Jupiter’s perspective) and it’s so close that the penumbra (fuzzy outer edge of shadow) is super thin.

— Katie Mack (@AstroKatie) 14 september 2019