The Quadrantids in your sky

We’ve already shown you how this stream of particles comes curving in on a cometary orbit to pass by Earth – take another look at that dynamic diagram.

And here’s how and where they will appear as meteors as they crash into our atmosphere, mostly during the night between January 3 and 4 (Friday and Saturday).

See the end note about enlarging illustrations.

The radiant is the point or small area in the sky from which, traveling on essentially parallel paths, the “shooting stars” seem to spray into all parts of the sky.

(Radiant names are derived from the constellations they’re in; this one is unique is that the constellation Qudrans Muralis, the mural quadrant, is an obsolete one in areas now assigned to others.)

The meteor trails aren’nt necessarily yellow: that’s to distinguish them from the other features in our chart.  And they’re likely to appear seconds or minutes apart, only rarely simultaneously.

The Quadrantids come at us from half-north, and from in front.  (Notice “Earth’s direction of travel” near the east point in imgthe picture.)  So they appear mainly on Earth’s front or morning side.  In other words, the radiant rises not long before midnight, and, as the night goes on, climbs higher, parallel to the celestial equator.  So the dark hours before morning twilight are when the radiant is highest and the meteors probably most abundant.

An estimate for their zenithal hourly rate, or ZHR, is 110 – one pf the best of the year.  But that means: the average number one alert observer might count in an hour at the peak time with the radiant overhead and the sky conditions perfect.  It’s all too likely that the time is not quite the peak,  the radiant is lower, the sky un-cloud-free and light-polluted, and the observer sleepy!

So you’ll probably count fewer, even if you’re warmly dressed and comfortable on a chaise longue facing east with a flask of coffee.

But it’s from many such counts, by observers who report their locations and observing methods and conditions, that meteor scientists derive their estimates not only of ZHRs but of the meteor streams’ orbits, compositions, and origins.

One major factor is favorable this year: the Moon is at First Quarter on Jan. 3 (at about 5 by Universal Time), so it sets about midnight, over on the western horizon opposite to where the Quadrantids’ radiant is rising.  So there will be little and then no moonlight to compete with the fainter meteors.

Earth, flying along its orbit, meets the Quadrantid meteors.  The time for the picture is midnight in North America’s Central time zone; America is swinging into view of the meteors.  The First Quarter Moon is crossing our orbit behind us.  The broad flat arrow shows Earth’s advance in 3 minutes, and the arrow on its equator shows its rotation in 3 hours.  The actual stream of particles in space is millions of miles wide; the dotted line represents only those that happen to arrive from exactly overhead.

Compare the picture from last year, when the Moon was two days before New, so rising just before sunrise.

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ILLUSTRATIONS in these posts are made with precision but have to be inserted in another format.  You may be able to enlarge them on your monitor.  One way: right-click, and choose “View image”, then enlarge.  Or choose “Copy image”, then put it on your desktop, then open it.  On an iPad or phone, use the finger gesture that enlarges (spreading with two fingers, or tapping and dragging with three fingers).  Other methods have been suggested, such as dragging the image to the desktop and opening it in other ways.

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