Thursday, May 2, 2013

eta Aquariid Meteor Shower 6-9 May, 2013

UPDATE to the update:
definitely an outburst, compare
and here

Update: on the MeteorObs list there is a report of an outburst, and a new dust trail analysis suggests that some dust trails will intersect Earth on the morning of the 7th (Australian time). So definitely go and look on the morning of the 7th.

Morning sky on Tuesday May 7 looking east as seen from Adelaide at 5:00 am local time in South Australia showing the eta Aquariid meteor shower radiant, the crescent Moon, Uranus and comet Lemmon. Similar views will be seen elsewhere at the equivalent local time (click to embiggen)

The eta Aquariids meteor shower, the debris from Halleys comet, peaks on May 6 at 01 UT (thats 11 am AEST and 10:30 am ACST, disappointingly in daytime) with a ZHR of 55. However, the radiant rises around 2 am, so you can't see the shower until the morning of Tuesday the 7th (see update above).

The figure ZHR is zenithal hourly rate. This is the number of meteors that a single observer would see per hour if the shower's "point of origin", or radiant, were at the zenith and the sky were dark enough for 6.5-magnitude stars to be visible to the naked eye.

In practise, you will never see this many meteors as the radiant will be some distance below the zenith. Also, unless you are out deep in the countryside, the darkness will be less than ideal. As well, moonlight will significantly reduce rates. How many are you likely to see in reality? I discuss this further down, lets talk about when to see them first.

Although the actual peak is on 6th at 13:00 AEST, for Australia the best time to see the eta-Aquarids is in the early mornig of the 7th (see update above). early morning of May 8 and 9, between around 4 and 5 am, when Aquarius is fairly high above the horizon.

Why the 8th, when the 7th is closer to the peak of the shower?  On the 7th the Moon significantly interferes with seeing the meteors (but it may still be worth watching, it's even worse on the 6th when the Moon is just below the radiant)
. By the 8th the Moon is only a thin crescent and low on the horizon.

How many will br seen on the 7th is not clear, but very good rates have been seen already, and dark sky sites may possibly see one meteor every two minutes or so. There have been many bright ones reported with persistent trains. People in the suburbs may be will see less, but at least one every 6 minutes should be possible.

People in the suburbs should see a meteor around once every 6 minutes, and in the country about once every 3 minutes on the 8th, a bit fewer on the 7th and 9th. The radiant of the shower is about five handspans up from the eastern horizon, and three handspans to the left of due east at 4 am (see above for a spotter chart at 5 am).

When looking, be sure to let your eyes adjust for at least 5 minutes so your eyes can be properly adapted to the dark. Don't look directly at the radiant site, because the meteors will often start their "burn" some distance from it, but around a handspan up or to the side. Be patient, although you should see an average of a meteor every six to three minutes, a whole stretch of time can go by without a meteor, then a whole bunch turn up one after the other.

Make yourself comfortable, choose an observing site that has little to obstruct the eastern horizon, have a comfortable chair to sit in (a banana lounger is best), or blankets and pillows. Rug up against the cold.  A hot Thermos of something to drink and plenty of mosquito protection will complete your observing preparations. As well as meteors, keep an eye out for satellites (see Heavens Above for predictions from your site).

The sky will also be particularly beautiful, with the Milky Way stretching over the sky and constellation of Scorpius gracing the north-western sky.If you have strong binoculars you can look out for comet Lemmon and Uranus either side of the crescent Moon.

Use the NASA meteor shower flux estimator for an estimate of what the shower will be like from your location. You need to choose 31 Eta Aquariids and remember to set the date to 7-8 or 8-9 May 2013. You can follow the progress of the shower at the IMO live Aquariid site.

Cloud cover predictions can be found at SkippySky.


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