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Lunar eclipse April 2014 April 14, 2014

Posted by aquillam in Astronomy, MichiganAstro, Urban Observing.
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If you’re in SE Michigan the chances of seeing the lunar eclipse are slim. Even if it does clear up, temperatures in the upper 20s aren’t very conducive to sitting outside for several hours watching it. But don’t despair, it is the 21st century after all, and while we may not have flying cars, we do have live streaming on the internet!

First up, a quick overview of the eclipse for observers in the eastern time zone: The eclipse begins just before 2 AM. By 2:30 it should be fairly interesting. The total eclipse begins at 3:07 AM and ends at 4:25 AM. The moon completely exits the umbra, ending the partial eclipse, at 5:33 AM.

If it is cloudy where you are, here are some resources to watch online:

Slooh.com http://events.slooh.com/stadium/total-lunar-eclipse-arizona-april-15-2014

Griffith Observatory TV http://new.livestream.com/GriffithObservatoryTV

Virtual Telescope’s WebTV http://www.virtualtelescope.eu/webtv/

The Coca-Cola space science Center and Columbus State University http://www.ccssc.org/webcast.html

Those are the ones I know about. A Google search might turn up more, especially if there’re any hangouts.

What is “opposition”? April 10, 2014

Posted by aquillam in Astronomy, MichiganAstro.
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In common vernacular, the word opposition means “opposed to”. So when I say Mars is “at opposition”, I get a lot of funny looks. What would a planet be opposed to? So here is an explanation of the astronomical term ”opposition”.

In astronomy, the word opposition actually means opposite in the sky from something else, usually the Sun. For example, the full moon always rises at sunset and sets at sunrise: it is opposite the sun in the sky, so the full moon is always at opposition.

The entire sky is shown a few minutes before sunset, with the Sun on the horizon  in the ENE and the Moon just above the ESE horizon.

A few minutes before sunset on June 12. The Sun and Moon are on opposite sides of the sky. The full moon actually occurs a little after midnight local time, so it is already above the horizon at sunset.

Mars was at opposition on April 8, 2014, so it rose at sunset that night nearly due east (as the Sun was setting nearly due west), and set at sunrise the next morning.

Opposition is a good time to observe the outer planets. There’s the obvious reason that the planet is out all night, so you get plenty of time to observe. However, opposition also means the planet will be at its closest position to Earth, so it’ll be bigger and brighter than normal too. Lets take a look at why.

The Sun and the orbits of two imaginary planets with perfecty circular orbits.

Opposition for circular orbits. An observer on the inner planet would look in one direction to see the Sun, and in the opposite direction to see the outer planet. In this case, the two planets are also at their closest.

 

If the orbits of all the planets were perfectly circular, opposition and “closest approach” would be the same.

 

 

 

 

 

 

 

 

 

However, the orbits are actually elliptical, and the ellipses aren’t aligned with each other. The eccentricity and orientation of the ellipses is what determines when “closest approach” actually occurs. Here is an exaggerated diagram.

A diagram showing the Sun and the elliptical orbits of two planets. The position of the planets is shown for "closest approach"

A few days after opposition, the two planets are actually closer together (though the difference is very small!)

A diagram showing the Sun and the elliptical orbits of two planets. The position of the planets is shown for opposition, so they are in line with the Sun.

An observer on the inner planet would look in one direction to see the Sun, and in the opposite direction for the outer planet, so the outer planet is at opposition.

 

 

 

 

 

 

 

 

 

 

 

 

 

A diagram showing the Sun and the elliptical orbits of two planets. The position of the planets is shown for when opposition and "closest approach" occur at the closest point in their orbits.

The best possible opposition.

All the planets in our solar system have nearly circular orbits. This means that “closest approach” and opposition happen very close to each other, but not exactly at the same time. The very best configuration is of course when opposition occurs at the point when the orbits are closest.

 

 

 

 

This is of course very rare. It happened for Mars back in 2003. The opposition of 2035 will again be very close, but not as good as 2003.

Here is a diagram for this year:

An image showing the Sun and the orbits of Earth and Mars.

Mars at Opposition on April 8, 2014. Closest approach is a few days later, on April 14.

 

Urban observing April 2014 April 1, 2014

Posted by aquillam in Astronomy, MichiganAstro, Urban Observing.
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Special Events

After a few months without much in the way of special events, April brings several things.

Eclipses

The biggest event of the month is probably the lunar eclipse on April 15. Unfortunately, here in Michigan, the eclipse begins at roughly 2 AM and finishes around 5:00 with totality starting a little after 3 AM and ending around 4 AM. Still, if it happens to be clear where you are, it’s worth going out and taking a look. This is the first of a series of four eclipses, about six months apart, all visible from continental US. For maps and information on visibility from your area, check out the eclipse page from NASA: http://eclipse.gsfc.nasa.gov/OH/OH2014.html#LE2014Apr15T

Of course those familiar with eclipses know that a solar eclipse generally falls two weeks before or two weeks after a lunar eclipse. Unfortunately in this case the solar eclipse is only an annular, and is best visible from Australia and Antarctica. More information from NASA: http://eclipse.gsfc.nasa.gov/OH/OH2014.html#SE2014Apr29A

Meteor Showers

The location of Lyra, and several other constellations, at 3:30 AM on April 22.

The constellation of Lyra is high in the east at 3:30 AM on April 22. The Lyrid meteors appear to come from this constellation, but will be visible across most of the sky.

April also brings a return of meteor showers. The Lyrids are active from April 16 through the 25th. The peak should be the morning of the 22nd, but any morning three days before or after that should bring a good number of meteors. Lyrids are known for producing bright dust trails that may last for several minutes, however a waning Moon will interfere with your ability to see these. Check the American Meteor Society articles on meteor showers the week before for predictions.

Mars Opposition

Mars is at opposition on April 8. That means it will rise at sunset and remain out all night. A few days later, on April 14, it reaches “closest approach”, when the distance between Mars and Earth is smallest. So pull out the telescopes and have a look. You’ll have to wait a year and a half before it happens again.

Planets

Practiced observers with binoculars might be able to catch the planet Mercury in the predawn skies at the start of the month. However, it will be a tough catch is it skims the horizon just before dawn. It reaches superior conjunction on the 26th, and returns to the evening skies in May.

6:30 AM on April 11. Neptune is just below Venus.

6:30 AM on April 11. Neptune is just below Venus.

Venus is just about as far west of the sun as it ever gets on April 1. This makes this whole month of excellent time for viewing it in the morning. It is in fact that incredibly bright thing in the East an hour or even two before sunrise. Late in the month it will dim quickly as it heads toward conjunction. Those with a small telescope can use it to find Neptune between the 10th and 13th. Neptune passes just below and to the right of Venus during those days. A nice crescent Moon joins Venus on April 25.

Mars and Porrima on April 25 at 10 PM.

Mars and Porrima on April 25 at 10 PM.

Mars is visible to both morning and evening observers this month. Look for it in the constellation of Virgo. It’s very near the Moon on the night of the eclipse. At the end of the month it is very close to the double star Porrima in Virgo. The distance between the two stars varies  noticeably over a few years. Unfortunately, right now they are very close to each other, so they won’t be distinguishable without a relatively large telescope until 2020.

The brightest thing in the winter skies continues to be Jupiter. It continues its retrograde motion through Gemini for most of the month, pausing and returning to prograde in the last week. Of course it’s now spring, so the best time to observe the winter constellations is before 10 or 11 PM. Orion sets a little after nine at the end of the month, and Jupiter follows not long after.  A thin quarter Moon makes a close pass on April 6, providing a nice opportunity for astrophotos without a telescope.

Saturn technically returns to the evening skies this month, rising at about 11:15 on April 1. the waning crescent moon passes very close on April 17.

Deep Sky Objects

If you have a small telescope, an April evening is a lovely time to put it to use. Early in the evening, many of the winter objects are still out. The Pleiades and the Hyades are naked eye objects, but a small telescope reveals hundreds of individual stars. If you like open clusters, M44 and M47 are also well worth a look. And of course, don’t forget M42, the Orion nebula.

10 PM on April 6, facing west

10 PM on April 6, facing west

Turning our gaze eastward, especially at the end of the month, reveals several globular clusters. These include M13, the Great Cluster in  Hercules, and M92 a great cluster on it’s own if it wasn’t so close to M13. M3 and M5 are also worth a look if your skies are dark enough.

10 PM on April 25, looking east.

10 PM on April 25, looking east.

A Tetrad of Lunar Eclipses – NASA Science March 28, 2014

Posted by aquillam in MichiganAstro, Urban Observing.
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A Tetrad of Lunar Eclipses – NASA Science.

 

Looks like a good year for eclipses! And the first one is only a few weeks away. As you finish up your taxes on April 15, head outside around 3 AM eastern and have a look for the dime red, fully eclipsed Moon!

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