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Star Points: Leonid meteor shower and penumbral lunar eclipse on tap this month | COMMENTARY

A couple of solar system events are happening overhead this month. Also, Mars, although well past it’s favorable opposition that was discussed here last month, remains very bright and easily visible in the evening sky.

Currently, Mars rises about five minutes earlier each evening. However, the Earth has caught up to and is now passing it, so Mars' apparent size is slowly shrinking. Look at it with any telescope while its surface details remain easier to glimpse.

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November is the month of the annual Leonid Meteor Shower. Meteor showers are caused when the Earth plows through tiny bits of debris left by comets. In the case of the Leonids, that comet is Comet 55/P Tempel-Tuttle, discovered in 1865.

The comet has an orbital period about the sun of 33 years. As its orbital path brings it nearer to the sun, comets lose material consisting of dust, meteoroids, ices and gases. The heavier material remains in orbit. Meanwhile, Earth travels its own yearly orbit which intersects that of the comet in mid-November.

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A balsam tree is silhouetted against the western sky during the Leonids meteor shower as seen in this time-exposure made early Sunday, Nov. 18, 2001, in Duluth, Minn. The Orion constellation is visible to the left above the tree. The diagonal streak is a meteor.
A balsam tree is silhouetted against the western sky during the Leonids meteor shower as seen in this time-exposure made early Sunday, Nov. 18, 2001, in Duluth, Minn. The Orion constellation is visible to the left above the tree. The diagonal streak is a meteor. (Brian Peterson/Minneapolis Star Tribune)

The Leonid shower is known to have outbursts approximately every 33 years, and greater outbursts every 99 years or so. These outbursts occur when then Earth plows through exceptionally rich knots of material left during the comet’s recent passages.

The next great outburst is predicted for 2099. So, the 2020 Leonids will be run-of-the-mill, except for one factor. Bright moonlight will not interfere this year. This is an advantage because any exterior lighting, be it from the moon or artificial outdoor lights, will diminish the number of fainter meteors viewed. For that reason, travel to a dark site is recommended for the most serious observer.

In our geographical region, the Leonids are predicted to peak in the pre-dawn hours of Tuesday, Nov. 17. The meteors can appear anywhere in the sky. However, their paths will all seem to be radiating away from an imaginary point in the head of the constellation Leo, the lion. This point is known as the shower’s “radiant.”

The other celestial event of note this month is a penumbral lunar eclipse. Simply explained, a penumbral eclipse occurs when the moon crosses the Earth’s penumbral shadow. Not as spectacular as a total lunar eclipse or even a partial lunar eclipse, where the moon completely or partially crosses the Earth’s darker umbral shadow.

As far as penumbral eclipses go, this one is pretty good because 83% of the moon will be inside of Earth’s penumbra. The moon will change from being a bright white full moon to a dimmer and grayer ashen full moon. If you don’t want to watch the whole thing, I would recommend checking it out regularly during other activities, such as during TV commercial breaks. (What else do you have to do?) That way, you will notice the stunning changes more readily.

The penumbral eclipse can be seen in the early morning hours on Monday, Nov. 30. Here is the timeline: 2:32 a.m., moon begins entry into Earth’s penumbra; 4:43 a.m., midway or maximum eclipse; and 6:53 a.m., moon leaves penumbra.

When can you first detect the penumbra crossing the full moon? When does the last bit of penumbra cease to be visible? These are questions for an observer.

Good luck with observing both of these events. Hopefully, the sky will be clear.

Curtis Roelle is a member of the Astronomical Society. His column appears the first Sunday of each month. His website is www.starpoints.org, and he can be reached at starpoints@gmail.com.

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