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Don’t miss the Geminids! December 5, 2018

Posted by aquillam in Astronomy, MichiganAstro.
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One of the best meteor showers of the year takes up most of the month of December, but will be best on the mornings of December 13 & 14.

Rising ENE a little after 7 PM, the radiant of the Geminids is up nearly all night. As always, the best time to watch for meteors is in the hours between midnight and dawn, since that’s when your sky is facing the direction Earth is traveling, so heres a map for December 14 at 2 AM.

14Dec0205_z

The sky from 42º latitude at 2 AM on December 14, 2018. Note Orion toward the SW, and the Big Dipper in the NW. Click for bigger image.

Conveniently, the Moon sets at about 10 PM the evening before, so if you can get away from city lights, you’ll have good dark skies for the best observing time. This is an active shower though, so it’s work going out and looking anytime you happen to be up and the weather is clear.

According to the AMS, the Geminids have a peak rate of about 120 meteors per hour (or about 2 per minute), tying them with January’s Quadrantids for highest rate. The usually lousy weather of December makes them much less famous, and harder to watch, than the August Perseids.

Additionally, Earth&Sky points out this shower has a high number of earth-grazers – meteors that come in at a low angle and appear slow moving. They’re actually moving pretty fast – they’re coming up from behind and hitting the Earth, like a stone hitting your back  or side car windows while you’re driving down the road. They’re rare, but memorable, and only visible in the evening.

So get out and look for Gemini as often as you can from now ’till Christmas!

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A naked-eye comet for the holidays (2018) December 4, 2018

Posted by aquillam in Astronomy.
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I guess I must be having a lot of fun, because it sure doesn’t feel like four months has passed since I last logged in here. But there’s a naked-eye comet out there, so I couldn’t let it go by without saying anything!

Comet 46P/Wirtanen is no Hale-Bopp or Hayakutake, but it’s a lot brighter than anything we’ve seen in the northern hemisphere for quite a while. It’s current observed magnitude comes in at a 5.4, making it about the same brightness as M13, the great cluster in Hercules. Experienced observers know this means it is visible to the naked eye, but only just, and only under ideal conditions when you know exactly where to look.

The good news is, it’s expected to get brighter. It’s also positioned perfectly for evening viewing in the northern hemisphere, and a pair of binoculars is all you need for a great view.

Many things affect how bright a comet appears, so predicting it can be a bit tricky. It should be brightest on December 16, but it’ll also be right next to the Moon that night, so looking a few days before or after is a good idea. Here’s a chart for 9 PM on December 16, with the position of the comet on several other dates noted.

Dec2018Comet

The sky on December 16, 2018. The yellow dots indicate the positions of comet 46P/Wirtanen at 9 PM on several other evenings between December 4 (under the arrow pointing to Deneb Kaitos) through December 31.

On December 4 – 5, it’s right next to Deneb Kaitos, one of the brightest stars in Cetus. It’ll pass less than 5º from Uranus between the 22 & 23. On the 29th, it’ll pass Hamal, the brightest star in Aries.

If you’d like regular updates, or charts for your location, check out the comet 46P/Wirtanen page on LiveSky.

Venus in August 2018 August 1, 2018

Posted by aquillam in Astronomy, MichiganAstro, Urban Observing.
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Everyone else may be talking about Mars, but don’t miss your chance to check out Venus this month!

 

The orbits of Earth, Venus, and Mercury about the Sun, with 16º elongation and maximum eastern and western elongation shown.
The maximum elongations for Venus are shown with the dashed lines, and those for Mercury are shown with the dotted lines.

Venus orbits closer to the Sun than we do. That means from our point of view, it never gets very far from the Sun. When it is farthest in the sky from the Sun, we call it greatest elongation. On August 18, Venus will be at greatest eastern elongation, and it’ll be a little over 45º east of the Sun. That means it’ll be easy to see in the western sky for at least an hour after sunset.

 

 

Additionally, Venus will be headed for a crescent phase, which brings it closer to us, so it’ll be getting bigger and brighter. It’ll actually be at it’s brightest near the end of September.

 

 

Because of the angle of the ecliptic, it sets a lot sooner in September. Here are a couple maps showing the ecliptic from SE Michigan (or anywhere between 40 – 50º N latitude) on August 1st and 30th, both 1 hour after sunset. You can see the ecliptic moves southward, which means anything on the ecliptic will set earlier in the northern hemisphere.

W (west) is at the center bottom and NW near the bottom right corner. The ecliptic runs from the top left corner to the bottom about 1/4 of the way between W and NW.

Venus and the ecliptic on August 1st 2018, 1 hour after sunset.

W (west) is at the center bottom and NW near the bottom right corner. The ecliptic runs from the top left corner to the bottom just to the left of W.

Venus and the ecliptic on August 30th 2018, 1 hour after sunset.

So now’s the time for the easiest and latest observations of Venus, and September will be the time for the brightest and most interesting telescopic view of Venus!

Observing tips for July 4th, 2018 July 2, 2018

Posted by aquillam in Astronomy, MichiganAstro, Urban Observing.
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The forth of July brings a lot of people outside after dark. While you’re waiting for those fireworks to begin, here are a few things to look for.

I recommend taking along a pair of binoculars.

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Venus and Mercury in the West July 3, 2018, 9:30 PM.

Start about half an hour after sunset (or about 9:30 in SE Michigan) and look west. About 20º ( 2 sideways fists) above due west is Venus. As the skies darken, it stands out like a beacon! look 16º (index finger to pinky) down and to the right for Mercury. Mercury can be a tough object to spot because it’s never far from the Sun, so it’s never visible in really dark skies. The first map is for July 3, 9:30 PM in Ann Arbor, but should be good for the 4th as well.

04July2200S_JuSa

Jupiter and Saturn in the south at 10 PM July 4

Fireworks usually begin around 10 PM (especially if you’re farther north.) Get a seat facing south for some of the summer’s best celestial show. Jupiter is about 30º above the southern horizon, and Saturn about 10º up in the SE. While you’re looking that way, be sure to check out Scorpio and Sagittarius too. Bright Antares, the heart of the scorpion, falls between Jupiter and Saturn right now.

With binoculars or a small telescope, you can pull in the 4 brightest moons of Jupiter. They’ll be lined up in a tight row on the 4th, which helps make it easier to pick them out at low magnification.

From left to right, Io, Europa, Jupiter, Ganymede, and Callisto

The Galilean Moons of Jupiter at 10 PM July 4, 2018.

If you actually have a small telescope and can pull your eye away from Jupiter, check out nearby Zubenelgenubi, a nice double star whose name means “southern claw” because it was once considered part of Scorpius.

Saturn is sitting on the top of the teapot. If your skies are dark enough later in the evening, you’ll be able to see the Milky Way trailing up the sky next to it. With binoculars or a small scope, the rings should be visible, if only as a strangely oblong shape. Some of the brighter moons may also be visible, though they aren’t nearly as easy as Jupiter’s moons.

From left to right, Iapetus, Rhea, Saturn, Tethys, and Titan, which is actually much lower that the other moons.

Saturn and its moons, July 4, 2018 at 10 pm

It’s early days yet for Mars, but if you’re out past midnight, look back to the same are Saturn was at 10 PM. Mars rises ESE around 11 PM, so it’s up nearly 10º in the SE at midnight. It’s the brightest thing in that area right now, and only getting brighter, so if your skies are clear, it’ll be hard to miss. Keep an eye on it the rest of the month as it moves toward closest approach on July 31!