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Cassini’s Legacy September 11, 2017

Posted by aquillam in Astronomy, MichiganAstro, Science.
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As the Cassini mission comes to an end, NASA and JPL ponder what its legacy will be.

When the mission started, I had just recently started working as the outreach coordinator for Michigan Astronomy, and the presentations I did about it were some of the first of my career here.

My how the time flies.

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Saturn Opposition 2017 June 16, 2017

Posted by aquillam in Astronomy, MichiganAstro, Urban Observing.
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It’s summertime, and that means Saturn-time!

But why is that?

A year on Saturn is a bit more than 29 years on Earth, which means Saturn moves about 12º along the ecliptic each year. For comparison, the Moon moves about 15º per day, so in a whole year, Saturn’s position will change less than the the Moon changes in a single day! It fact it’s so little that it take Saturn an average of two years to move through each zodiac constellation. Last year Saturn crossed the boundary into Ophiuchus (between Scorpio and Sagittarius), and it won’t leave until December. That means Saturn will be visible in the evening at about the same time this year as it was last year.

Ophiuchus is often called the 13th zodiac because itt sits between Scorpio and Sagittarius

Saturn takes 29 years to make a complete circuit of the ecliptic

Of course 12º isn’t nothing. Each year opposition drifts just a little farther east along the ecliptic, so the date changes. And since there are 360º in a circle and 365 days in a year, the date corresponds to roughly a degree per day! This year, opposition was June 15th. In 2016, it was June 3, and in 2015, May 23. Next year, opposition will be June 27.

By the way, opposition is when something (like Saturn) is opposite something else (like the Sun) in the sky. So when Saturn is at opposition, it rises at sunset, then sets at sunrise. Each night it rises a little earlier, so the weeks following opposition are the best time for evening observers to get a look. Closest approach is always close to opposition too, so the planet will be bigger and brighter than usual.

elpOrbitsOpp

At opposition, the Sun, Earth, and outer planet are on a line with the Earth in between.

elpOrbitsClose

Because the orbits aren’t circles, the Earth may get closer to the outer planet a few days before or after opposition.

 

So enjoy summertime Saturn while you can. In about 4 more years, it’ll be fall when Saturn’s out.

Urban Observing June 2016 – Planets version June 7, 2016

Posted by aquillam in Astronomy, MichiganAstro, Urban Observing.
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I’m a little overloaded these days, but there’s so much good stuff in planets I wanted to get those out there.

Mars Opposition was on May 22, and it’s closest approach on May 30, so early June is still a great time to check out the red planet.

It’s not far from Saturn, which is at opposition on June 3. It has a nice tilt now too, so it’s a great month for cell phone pictures through a telescope.

Jupiter is still a great evening target. Look for it high in the south at sunset. It’s only 1º from a first quarter moon on the 11th.

11June2300SE-W.png

Morning observers get some of the easiest viewing of Mercury the first 2 weeks of the month. Of course, the early sunrise means you’ll have about a 15 minute window 30 – 45 minutes before sunrise to catch it. Greatest western elongation is on the 5th, but the best angle relative to the horizon is the 13th (at least at 42º latitude.) Binoculars will help.

13June0520ENE.png

Venus fans are out of luck. Superior Conjunction is on the 6th, so it’s lost in the Sun’s glare most of the month. If you’re up for challenge, start watching for it in the evening at the end of the month.

The lowest full moon of the year will be on June 20. If you’re a fan of optical illusions, check it out – the low altitude enhances the Moon Illusion.

Earth goes between sun and Saturn tonight | EarthSky.org June 2, 2016

Posted by aquillam in Astronomy, Urban Observing.
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June 2-3, 2016 is the night of Saturn’s opposition. This world is now opposite the sun in Earth’s sky. How to see Saturn and enjoy it as its best!

Source: Earth goes between sun and Saturn tonight | EarthSky.org