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Wednesday, November 15, 2017


Leonid Meteor Shower, November 17-18, 2015

North-eastern horizon at around 4:00 am (daylight saving time, 3:00 am standard time) on the morning of Saturday, November 18 (click to embiggen). The starburst indicates the radiant, the apparent point of origin of the meteors (they can actually first appear much further away from the radiant).

The Leonids are an iconic meteor shower due to spectacular displays in 1833, 1966, 2001 and 2002. They are due to dusty debris from Comet Tempel-Tuttle slamming into Earth's atmosphere. While occasional Leonid meteors can be seen most of November, the rate rises to a peak in mid-November. However, the spectacular rates of the storm years are long gone and will not reoccur for some time, For the foreseeable future only the occasional meteor will be seen, even at the peak.

This year the peak is on Saturday, November 18, with estimates of between 10-15 ZHR (Zenithal Hourly Rate - the number of meteors you could expect to see if the radiant was at the Zenith under dark skies). However, the radiant never gets very high in Australia, and although the peak occurs 3:30 am in Australia, we expect to see far fewer meteors than the ZHR. Somewhere in the range of one meteor every 20 minutes is likely even under dark skies. However, this year the meteors are expected to be quite bright.

As well, this year there may be an early peak. The IMO is advising of possible enhanced Leonids activity on November 17 at 4 am AEDST ( November 16, 17h07m UT), this is November. A ZHR of 12 composed of brighter than usual meteors may be seen (this translates to about a meteor every 15 minutes).

While we can expect to see very few meteors, the morning will be a beautiful sight anyway.Orion the Hunter is stretched out overhead, and the Pleiades nearby. You might even see a satellite or two (but not the ISS or iridium flares). To check the weather forecast, go to the Meterology Departments forecast site, or alternately the Weather Channel.

When to look: The best time is between 3:00 am to 5:00 am daylight saving time (2-4 am standard time) on the mornings of the 17th to 18th.

Where to look: Face north-east. About five hand spans above the horizon you should see bright Saturn. A hand span to the right brings you to the bright white star Alpha Leonis, Regulus. Following down and to the left from Regulus you will see a number of fainter stars which form a sickle shape, the head of the lion. The radiant of the Leonid shower will be roughly in the center of the curve of the sickle, about one finger width up (see image above). However, the meteors can turn up almost anywhere in the eastern half of the sky, so make sure you have a spot with a fairly clear field of view, without any bright street-lights in the way. Use common sense in choosing a viewing site. Lone persons should not choose dark parks in the seedy part of town to watch the Leonids, as a mugging can ruin your entire day.

What do you need: For meteor watching, very little is needed. Basically, all you need is you. If you want to try and count the meteors, you will need a couple of sheets of paper, a pencil and a good watch. Bundle up against the pre-dawn cold, warns shoes, thick socks, sensible pants and a good jumper and possibly a blanket to wrap yourself in (I really mean this, last time I had a jumper and a windproof and I was seriously cold). Bring a reclining chair if you have one, or just a picnic chair or a good picnic blanket, and find a dark site with a wide-open view of the sky. Then just lie back, relax, and look up at the stars. Optional extras are a torch with red cellophane over the business end (otherwise you ruin your night vision everytime you turn it on), and a thermos of something warm to drink. Mosquito repellent is also a very good idea.

Give it some time: Many people wander out, look around for five minutes, see nothing and wander back in. It will take about five minutes for your eyes to become accustomed to the dark. Also, meteors tend to come in bursts, and if you wander out in a lull, you may miss lots. As well, our time perception sucks. You may think you have been watching for 10 minutes, but in reality only about 2 minutes has passed. Give it time, watch the stars, and enjoy.

IMO Leonids Live! IMO weekly meteor outlook.


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