## Watch the Quadrantid meteors tonight! January 3, 2009

Posted by dorigo in astronomy, personal, science.
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Tonight the Earth will cross the core of a filament of debris orbiting our Sun since the passage of a comet in the year 1490. This will give rise to a spectacular shower of meteors, the Quadrantids.

I observed this shower in 2002 and 2004. In particular, I vividly remember the night of January 4th, 2004: exactly five years ago, I witnessed a beautiful peak of this meteor stream. Quadrantids are not so well known as the more famous Perseids or Leonids, but they can provide quite sizable rates during the first nights of January.

Tonight I am unable to repeat the bold feat of 2004: I feel tired after a day on the snow, and the temperature outside is -15 degrees! However, if you have a chance, please have a look at the sky. Quadrantids flow out of a point of sky between Ursa Mayor and Bootes, high up in the northern sky in the second half of the night. You need not observe in that direction: meteors will streak from that point in all directions.

Five years ago I drove to Passo S.Antonio, not far from Padola, where I am right now on vacation. The night then was bitterly cold, -11 to -14 degrees, but I had dressed up with several layers of warm clothing. Nevertheless, in order to stay out watching the stars I had to make frequent runs back and forth. I managed to observe for four hours!

I took notes of the time and magnitude of all the quadrantid meteors I saw during the four hours of observation. In the end, there were 144 of them (plus 13 non-quadrantids)! The peak was, as expected, in the hours before dawn, when I saw 40 tracks in a 15′ period before 6AM. My notes also show that at 5.48AM I observed FOUR simultaneous meteors, all in Virgo, and separated about 10 degrees. Two of visual magnitude 3.0, and two of magnitude 4.0. A spectacular event!

Below I report a few graphs I made after data analysis. The first shows the Zenith Hourly Rate (ZHR), the meteor rate per hour corrected for the altitude of the radiant, the light pollution, and other factors. As you can see, the ZHR soared to about 200 just before dawn on January 4th, 2004.

The fit is a gaussian distribution (other curves could provide just as good an interpretation of the distribution of ZHR values), which peaks at 5AM UT, with a rate of exactly 200. Note that the point between 3.75 and 4.00 is not zero: it is missing, since I took a break!

The second graph shows the distribution of visual magnitude of the 144 quadrantid tracks, a distribution which one needs to fit in order to find a coefficient R, the population index (basically an exponential slope), used in the computation of the ZHR. If the shower has many bright meteors, R is small, and the ZHR receives a smaller correction if the sky darkness is not perfect (fewer faint tracks fall unseen). My fit obtains $R=1.805 \pm 0.236$, which is well compatible with 2.0, the value usually adopted when R is not known from direct measurement.

The distribution of visual magnitudes falls for values above 6.0, since the sky was not free from light pollution, and the faintest meteors I could detect were of magnitude 5.0: only three of them, seen just because I was looking exactly where they fell. The human eye is unable to detect faint signals with peripheric vision, and that is the reason of the dampening of the curve for values above 4.0.

I hope some of you may spend some time out tonight, and let me know how many Quadrantids could be seen!

Update: upon checking a few sources, I found out that the peak this year was last night! This night the rate should be in the few tens per hour… I feel relieved after all! In fact, while I am already in bed with my laptop as I write these lines, until I discovered that the peak has already happened a part of me wanted to pull my body out, dress up like a total freak, and drive to a remote place!

1. International Year of Astronomy: IYA2009 « Collider Blog - January 5, 2009

[…] There is even a calender of astronomical observations, listing for example the Quadrantid Meteor Shower that Tommaso Dorigo just wrote about. […]

2. changcho - January 6, 2009

Happy New Year Tomasso – I see you are a meteor fan as well. I only did a detailed observation of the Quadrantids back in the 80’s. It was cold but no snow (Northern California). For this year I could not do a ‘proper’ observation of the Quads – I was left alone overnight with the baby (wife worked at hospital that night); however after feeding him he went back to sleep around 6:00 am local time I saw that the sky was still dark and Bootes was quite high – went out to the backyard and observed 3 meteors in 6 minutes! Not bad I thought, but I was very sleepy and cold and went back to sleep.

Question – what function are you using to find your parameter R? Just a polynomial?

dorigo - January 6, 2009

Hi Changcho,

no, it is an exponential, but there is a damping factor $1-erf(x-x_0)$ to account for the magnitude extinction. The exp slope is the population index R I mention in the post.

Cheers,
T.

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