Geminids Meteor Shower 2014

One of the most active and reliable meteor showers, the Geminids, happens every year in mid-December. This year’s display promises to be a good one for those meteorwatchers with clear skies.

The maximum rate of Geminids is predicted to occur between sunset on 13 Dec and sunset on 14 Dec, so the night of 13 Dec is the best bet, although nights on either side will still show plenty of shooting stars.

UPDATE: The excellent International Meteor Organisation (imo.net) have issued a live graph of Geminid activity. Last night the peak rate was around 46/hr +/- 21/hr. That rate will only increase overnight tonight, to a peak of around 120/hr.

When Gemini Sends Stars to Paranal
Image Credit & Copyright: Stéphane Guisard (Los Cielos de America), TWAN

There are a few ways you can maximise your chances of seeing some Geminids (see The What, How, Where, When and Why) but the best way is to get somewhere dark, like one of the UK’s International Dark Sky Places. I’ll be heading down to Galloway Forest in SW Scotland.

The Geminids’ radiant (the point in the sky where all the meteors appear to emerge from) rises at sunset, so you can begin your meteorwatch as soon as it gets dark enough. You’ll have until near midnight under dark skies, at which point the last quarter moon will rise to brighten the sky a little and drown out some of the fainter meteors.

The number of meteors that you will observe every hour depends on a number of factors:

• the density of the cloud of dust that the Earth is moving through, that is causing the shower in the first place;
• the height above the horizon of the radiant of the shower, the point from which the meteors appear to radiate;
• the fraction of your sky that is obscured by cloud;
• the naked-eye limiting magnitude of the sky, that is a measure of the faintest object you can see.

The Geminids meteor shower has a maximum zenith hourly rate (ZHR) of  around 120 (the highest of any meteor shower). This is the number of meteors that you can expect to see if the radiant is directly overhead (the point in the sky called the zenith), and you are observing under a cloudless sky with no trace of light pollution.

However conditions are rarely perfect. In the UK, for example, the radiant of the shower will not be at the zenith; it will be around 10° above the horizon at 1800h, 25° above the horizon at 2000h, 40° at 2200h,, 60° at 0000h just as the Moon rises to spoil the view a little.

Assuming a clear night, the other factor is the limiting magnitude of the sky, a measure of the faintest object you can see. Man-made light pollution will be an issue for most people. From suburbia the limiting magnitude of the sky is ~4.5 (around 500 stars visible), so you will only be able to see meteors that are at least this bright; the fainter ones wouldn’t be visible through the orange glow. In a big city centre your limiting magnitude might be ~3 (only around 50 stars visible); in a very dark site like Galloway Forest Dark Sky Park the limiting magnitude is ~6.5 (many thousands of stars visible), limited only by the sensitivity of your eye. So in most cases it’s best to try and get somewhere nice and dark, away from man-made light pollution.

The calculation that you need to make in order to determine your actual hourly rate is:

Actual Hourly Rate = (ZHR x sin(h))/((1/(1-k)) x 2^(6.5-m)) where

h = the height of the radiant above the horizon

k = fraction of the sky covered in cloud

m = limiting magnitude

Let’s plug the numbers in for the Geminids 2014.

ZHR = 120 (maximum)

h = 10° at 1800, 25° at 2000, 40° at 2200, 60° at 0000

k = 0 (let’s hope!)

m = 6.5 (if you get somewhere really dark!)

So your actual hourly rate under clear dark skies is

(120 x sin(10))/((1/(1-0) x 2^(6.5-6.5) = 21 meteors per hour at 1800
(120 x sin(25))/((1/(1-0) x 2^(6.5-6.5) = 50 meteors per hour at 2000
(120 x sin(40))/((1/(1-0) x 2^(6.5-6.5) = 77 meteors per hour at 2200
(120 x sin(60))/((1/(1-0) x 2^(6.5-6.5) = 104 meteors per hour at 0000

If you’re observing in suburbia you need to divide these numbers by around 4, and in bright cities by 10! Nonetheless, even in a city if you’re out at midnight during peak activity you’ll see around 10 meteors.

Remember though that these numbers are assuming perfectly clear skies under perfectly dark conditions, and are assuming a peak rate of 120 at each of these times. It probably won’t be nearly this good, but the bottom line is: there’s never a better night to see meteors!

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Perseids 2013: The What, How, Where, When, and Why

Here’s a simple guide for observing the Perseids 2013 meteor shower this year, covering five basic questions:
What is the Perseids meteor shower?

The Perseids meteor shower is the most reliable of the active regular meteor showers that happen throughout the year. A meteor shower is a display of meteors (or shooting stars) where you see lots of them in the space of just a few hours. The Perseids occurs around the same time each year, in mid-August, and during the peak of the shower meteor rates increase from just a few an hour (the background rate that you’ll see on any clear, dark night) up to maybe 100 or 200 meteors every hour for observers in the perfect location. Meteorwatchers in the UK will probably see dozens per hour from dark sites, dropping to a few an hour (still worth watching for) in towns and cities.

How can I observe the meteor shower?

You don’t need any special equipment to observe a meteor shower; just your eyes. Try and get as far from city lights as possible (out into the countryside if you can, or into a local park if not), and get comfortable. You might want to bring a reclining deck chair with you, as that makes meteorwatching much more civilised! Just lie back and take in as much of the sky as possible. If you’re lucky enough to see a good display of meteors, you might see as many as one a minute, maybe more!

Where should I look?

Meteors streak across the whole sky, so you don’t need to look in any specific direction, but of course if you’ve got a tall building or tree that’s blocking the view, or a streetlight nearby that’s a bit glare-y, then put these to your back. The Perseids meteors all appear to streak from a point in the sky (called the radiant) in the constellation of Perseus (hence the name) which rises in the east about 10pm local time, climbing to its highest in the sky towards dawn.

When is it happening?

The peak of the meteor shower will probably happen some time around 1815 and 2045 UT (1915 and 2145 BST) on Monday 12 August 2013, although there are uncertainties here. The peak could happen any time between 1415 BST 12 Aug and 0215BST 13 Aug. This means that observers in the UK might catch the peak of the shower, if it happens after the sky darkens on 12 August. Even on the nights on either side we’ll still see plenty. In fact the peak of the Perseids is several days wide, so you can start meteorwatching early, and carry on well after 12 August, so that even if this weekend is cloudy you’ll almost certainly have a chance to see some Perseids. Whatever night you’re out you’ll see more the later you’re up. Starting after dusk, the meteor rate will increase each night as Perseus climbs higher in the sky towards dawn.

Why do meteor showers happen?

Meteors are tiny bits of space dust streaking through our atmosphere. These motes of dust float about in space and as the Earth orbits the Sun it hoovers them up. Sometimes the Earth passes through a particularly dense clump of dust, and we get lots of meteors, in a meteor shower. These clumps of dust are left behind by comets as the orbit the Sun, their streaking tails leaving behind a trail of tiny rock particles. The comet that left behind the space-rocks that we’ll see in the Perseids meteor shower is called Swift-Tuttle, after the two astronomers that discovered it in 1862.

Quadrantids Meteor Shower 2012

On the night of 03/04 January 2012 the first meteor shower of the year will take place, the Quadrantids. This shower ranks as one of the best performers of the year, assuming your skies aren’t clouded, as they so often are in winter. If the peak of this shower occurs under ideal conditions – i.e. perfectly clear skies, free from light pollution – then you can expect to see in excess of 100 meteors every hour. The peak for this shower is very brief though, so you’ll have to catch just the right conditions at just the right time to see a display this good. This year’s peak is estimated to occur just before dawn on 04 January 2012.

Not only do you have the weather to contend with, but this year the waxing gibbous Moon will be up for much of the night. However the Moon sets at around 0415, giving you a couple of hours before the sky starts to brighten before sunrise. Given that the peak of this shower will probably occur within this short window, things are looking pretty good for this year’s display.

Last year’s graph of meteor activity shows how sharp the peak is, so you probably won’t see many Quadrantids on the nights either side of the peak, but it’s worth a look if you have clear dark skies. ZHR for this year may be anywhere between 60 and 200.

Quadrantids Activity from 2011, credit imo.net

How best to view the Quadrantids 2012

1. Get somewhere as far from street lights and city glow as possible, preferably somewhere really dark, like your nearest national park or one of the UK’s dark sky places: Galloway Forest Park, Sark or Exmoor.
2. Go out at the right time, which for this year’s shower is between around 0400 and 0700 GMT.
3. You don’t need binoculars or a telescope, your eyes are best for viewing meteors.
4. Wrap up warm, as if you have clear skies (which you’ll be hoping for) it will be very cold in these early morning hours.
5. Bring a reclining deck chair so you don’t have to stand all night, and a blanket to wrap yourself in!
6. Although the radiant of the meteor shower (the point where the meteors will appear to stream from) is high in the E around 0400 you don’t need to worry about facing in any particular direction, just position yourself so that you can see as much sky as possible, and enjoy the view!

You can follow the progress of the meteor shower at meteorwatch.org, or on twitter via @VirtualAstro and the #meteorwatch hashtag.

If you want to make more serious observations of this shower you can submit them to either the International Meteor Organisation, the British Astronomical Association, or the Society for Popular Astronomy.

Draconids Meteor Shower 2011

On Saturday 8 October 2011 a rare event may occur – a meteor storm! The usually sedate Draconids meteor shower only produces a few shooting stars per hour in most years, but in some years we have a meteor storm, and that’s just what’s predicted for this year.

It won't look like this

During a meteor storm the Earth passes through a particularly dense clump of comet dust, meaning that rates of shooting stars temporarily spike, and estimates this time suggest the possibility of up to 10 shooting stars per minute during the peak of the storm. However a nearly full Moon will spoil the view, drowning out all but the brightest 10% of meteors, reducing the actual observed rate of perhaps 1 per minute – still well worth looking out for.

The peak is set to occur at 2000UT (2100 BST), and is ideally placed for observers in the UK. Activity is expected to increase from 1600UT (1700 BST) but at that stage the sky will still be bright in the UK.

If you’re keen to witness this (possibly) amazing event here are some top tips:

1. Head out early. Start your meteorwatch once the sky gets dark enough. For most people in the UK this will be from 1900 – 1930 BST (anyone living in the north of Scotland will have to wait a bit longer). Although the peak of the storm is estimated to occur around 2100 BST there will be plenty to see in the hours leading up to the peak.
2. Know where to look. The Draconids all appear to originate from the constellation Draco, which will be high in the NW sky, just above and to the left of the north star, Polaris. However the meteors will streak across the entire sky so don’t just look NW.
3. Know what to look for. Meteors appear as bright streaks of light moving rapidly across the sky. They last for a fraction of a second, but the Draconids are unusually slow meteors. Still, blink and you might miss one.
4. Keep the Moon to your back. The full Moon will drown out the light from all but the brightest Draconids, and if you look at the Moon it will spoil your night vision, so keep it behind you, ideally blocked out by a building or tree.
5. You just need your eyes. Binoculars and telescopes, while ideal for observing faint nebulae and planets, are no good for meteorwatching. You want to take in as much of the sky as you can, and have as wide a field of view as possible, so just use your eyes.
6. Get comfortable. The best bit of meteorwatching kit is a reclining lawn chair. Point it towards the NW, lie back, look up and enjoy the show.
7. Keep warm. It will be very cold outside if it is clear, so wrap up warm. If you’re lying back on a reclining chair, wrap yourself in a blanket or sleeping bag form maximum warmth.
8. Get away from city lights. This isn’t as important for this shower, as the Moon is flooding the sky with natural light anyway, but in general the fewer lights you have around you the better.
9. Get away from clouds. This hopefully goes without saying, but if your sky is cloudy you won’t see much. The UK Met Office website can tell you if there is a clear sky anywhere near you, and you should consider traveling to get clear skies.
10. Record your observations. If you want to take part in a meteorwatch and submit your observations there a several ways you can do that. One fun and accessible approach is to tweet your observations with the #meteorwatch hashtag. If you want to take more detailed rigourous data you can submit an observing form to the International Meteor Organisation, the British Astronomical Association or the Society for Popular Astronomy

Make sure you tell your friends! This a great opportunity to see a rare meteor storm, so get as many people as possible outside and looking up.

CAVEAT: This is only a predicted meteor storm; it may not occur and if it does not then meteor levels will be very low.

Quadrantids Meteor Shower 2011: What You Might See

The first meteor shower of 2011 is the Quadrantids, the peak of which falls on the night of the 03/04 January 2011. The Quadrantids shower has one of the highest predicted hourly rates of all meteor showers, comparable to the two great annual showers, the Perseids and the Geminids, occurring in August and Deember respectively. However unlike the Perseids and Geminids, the Quadrantids peak is very narrow, occurring over just a few short hours.  (You can read the IMO’s rather technical summary of the 2011 Quadrantids here: http://www.imo.net/calendar/2011#qua)

The predicted Zenith Hourly Rate (see my previous post about ZHR and what it actually means here) for the Quadrantids is around 120. The narrow peak is predicted to occur some time between 2100 on 3 January and 0600  on 4 January 2011, however the radiant of the shower – the now-defunct constellation Quadrans Muralis – is very low in the evening hours, rising higher towards dawn, and so the best viewing times are later in this run, just before dawn.

The radiant will rise due N and get to its highest before dawn due E, so look roughly in a NE direction to maximise your chance of seeing some Quadrantids. As always with meteor showers, don’t use binoculars or a telescope – your naked eyes are best. One very useful bit of equipment is a reclining deck chair, which makes observing so much more comfortable!

Let’s use the equation relating ZHR to actual observations of meteors to work out how many Quadrantids you might see:

Actual Hourly Rate = (ZHR x sin(h))/((1/(1-k)) x 2^(6.5-m)) where

h = the height of the radiant above the horizon

k = fraction of the sky covered in cloud

m = limiting magnitude

In the case of the 2011 Quadrantids, if observed from the UK, h = 15 degrees at 2100, rising to 25 degrees at midnight, 40 degrees at 0300, and 65 degrees at 0600. Let’s assume you have clear skies (haha) with k = 0.

The number of Quadrantids you can expect to see from a variety of observing sites, at various times throughout the night, is as follows:

For very light polluted sites, such as city centres, m = 3, and therefore you can expect to see between 3 and 10 meteors per hour at the peak, depending on when it occurs.

In suburban skies near a city or town centre m = 4, and you’ll see between 5 and 20 meteors per hour at the peak, depending on when it occurs.

In rural skies where m = 5, you’ll see between 11 and 38 meteors per hour at the peak, depending on when it occurs.

Under very dark skies, where m = 6.5 (i.e. where there is no or negligible effect of light pollution, like in Galloway Forest Dark Sky Park) you’ll see anywhere between 31 and 109 meteors per hour at the peak, depending on when it occurs.

Remember, all of these numbers assume perfectly clear skies. If half your sky is cloudy, cut these numbers in half!

Also remember that it depends when the peak occurs. Due to the rather narrow peak, if you observe at 2100 on 3 January you may see very few if the peak doesn’t occur until 0600. Still, it’s very much worth a look, just in case!

How many Quadrantid meteors will I see?

Where are you observing from?	Limiting magnitude	Number of Quadrantids per hour if peak occurs at 2100	Number of Quadrantids per hour if peak occurs at 0000	Number of Quadrantids per hour if peak occurs at 0300	Number of Quadrantids per hour if peak occurs at 0600
Very light polluted city centre	3	3	5	7	10
Suburban Site	4	5	9	14	20
Rural Site	5	11	18	27	38
Dark Sky Site	6.5	31	50	77	109