Backyard Astronomy: May 2014

Most of May, peaking May 6-7: Eta Aquariid meteor shower. A meteor shower occurs when the Earth, in its orbit around the Sun, passes through the debris trail of a comet. The Eta Aquariids are associated with Halley’s Comet. Meteor showers are named after the constellation from which they appear to be coming in the sky—in this case, the constellation Aquarius, near Eta Aquarii, one of its brighter stars.

May 10: Saturn at opposition. Opposition is when a planet is on the opposite side of the Earth from the Sun (see below). It’s the best time to view a planet through a telescope.

opposition_saturn

 

May 24: Meteor shower outburst. When the Earth passes through the debris trail of Comet 209P LINEAR, it promises an exciting meteor “storm.” This burst will appear to originate from the constellation Camelopardalis.

Backyard Astronomy: April 2014

Here are some fun astronomical events you can watch from your own backyard. 

April 8: Mars at opposition. Opposition is when a planet is on the opposite side of the Earth from the Sun (see below). It’s the best time to view a planet through a telescope.

opposition

April 15: Total lunar eclipse. A total lunar eclipse occurs when the Earth moves between the Sun and the Moon (see below). Unlike a solar eclipse, in which the Moon moves between the Sun and the Earth, you don’t need any protective eyewear to watch a lunar eclipse.

lunar_eclipse

April 28-29: Annular solar eclipse. This is also known as a “ring of fire” eclipse, due to the way the Moon only partially blocks the Sun. During a total solar eclipse, the Moon moves between the Sun and the Earth and is at just the right distance from the Earth to completely block out the Sun. An annular solar eclipse occurs when the Moon moves between the Sun and the Earth, but the Moon is far enough away from the Earth that it appears slightly smaller in the sky than the Sun. Protective eyewear is required to safely view an annular solar eclipse.

annular_eclipse

Transit of Venus

Mark your calendars, folks. Venus will pass between the Earth and the Sun — what is known as a transit — on the evening of June 5th (as seen from North America). On this date (and with the proper eyewear) you can watch Venus move across the face of the Sun. This is a rare event — the next Venus transit will occur over one hundred years from now.

Tons of details — including how to safely observe the transit — are here.

“Super Moon” visible tonight

If you happen to be outside this evening, check out the Moon when it’s close to the horizon — it’s going to appear slightly larger than usual, thanks to a (somewhat) rare alignment of the Moon’s position in its orbit around Earth relative to the Sun.

The media are referring to it as a “Super Moon.” So, what exactly makes it “super”? The Moon has a slightly elliptical orbit around the Earth, which means sometimes it’s a little closer to the Earth (this position is called “perigee”) and sometimes a little further away (“apogee”). The difference is about 42,000 km, which sounds like a lot, but it’s only about 10% of the Moon’s average distance from the Earth. Today’s perigee is a smidgen1 closer than usual, but not enough to have any significant impact on ocean tides, earthquakes, or volcanic activity. Anyway, when the Moon’s perigee is especially close and coincides with a full moon, that seems to be a “Super Moon.” But it really amounts to a not-so-super 14% increase in the Moon’s apparent size in the sky compared with its apogee size. (I think I just broke the record for how many times the word “moon” can be crammed into a blog post.)

This NASA vid explains it all with nifty images:

DIY Science: If you’re an empirical kind of person, you can try the following: hold up a ruler or some other reference object at arm’s length (steady your arm on a stable surface) and carefully measure the apparent size of the Moon tonight, then do the same on October 12th when there is another full moon, but this time its close to apogee. See if you can detect a slight difference. If you have a telescope equipped with an eyepiece with a linear-scale reticle, this should be a piece of cake.

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