September 21, 2019

Astro-Challenge: Can You Spot the Moons of Mars?

This weeks’ challenge is a toughie and not for the faint of eye sight. In 1877, American astronomer Asaph Hall discovered the Martian Moons using the newly installed 26” refracting telescope at the U.S. Naval Observatory. Named appropriately Phobos (fear) and Deimos (terror), the moons were well suited companions for Mars, the god of war. Both moons, however, are tiny; outermost Deimos is 12.6 km in size and orbits Mars once every 30.35 hours, while innermost Phobos is larger, at 22.2 km in size and orbits the Red Planet in only 7.7 hours! In fact, at an orbital radius of only 9,377 km, Phobos orbits its primary closer than any other satellite in the solar system. Both tiny misshapen worlds are believed to be captured asteroids that will, one day millions of years in the future, spiral into Mars. Most of the time, these moons lie out of the range of all but the largest telescopes; but as Mars just passed opposition this past week, however, sighting these elusive moons might just be possible.

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Astro-Event of the Week:03.23.09:Can you spot Venus at Inferior Conjunction?

Warning: Do not attempt this weeks’ astro-feat unless the Sun is properly blocked, preferably just below the horizon! Sweeping the area near the Sun with optical equipment introduces the very real possibility of momentarily pointing at the Sun, which can cause optical damage!

This week’s observing challenge is a unique attempt, and will put you in league with a handful of skilled observers that even realize this is possible. It is not generally appreciated that Venus’s orbit is tilted 3.4 degrees in relation to our own, as represented by the ecliptic.

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