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(meteorobs) If you observe around Jul. 19
Dear observers,
There could be two possible minor showers which might be observable tonight:
1) The one from near-earth-asteroid 1997 BR, which may has maximum rate
around Jul. 19 when the Earth come across the point nearest to the asteroid's
orbit. Theoretical calcilation by Rob McNaught gives:
> Any meteors from this asteroid would occur around the descending node at
> Solar Long (2000) = 116.8 deg (~July 19) from a theoretical radiant near
>
> RA 175 deg Dec +65 deg (2000)
>
> Atmospheric velocity = 16 km/sec
>
> Such a low velocity could result in up to 19 deg of zenithal attraction
> to place the observed radiant on the horizon. This would be an evening
> shower for northern latitudes with a solar elongation of ~60 deg.
2) A more evident shower is given by Arkadiusz Olech in his paper submitted
to Astronomy and Astrophysics (which you can find at
http://xxx.lanldot gov/abs/astro-ph/9807017). Where this one has maximum around
Jul. 16/17, with very different radient from above one:
alpha-Cygnid meteor shower
Activity: Jun. 30 to Jul. 31, clear maximum near July 16-17
(solar longitude 116.5 degree)
ZHRs: 3.6 +/- 1.2
geocentric velocity = 41 km/s
Center of the radiant for the momentof maximum: RA 302.5 deg, Dec +46.3
drift of the radiant (deg/day in RA, Dec): +0.6, +0.2
population index: 2.55 +/- 0.14
It can be seen that the difference of the two possible showers is quite
obvious from their velocity and radiant. So it might be very helpful to
get such information during observation. It's a great pity that I could not
be able to observe it tonight at a dark site, for I have to stay at the city
for a preparation for a visit to Russia tomorrow. But please send me a
copy of your observations, and I would like to include it at my web page
for 1997 BR at http://vega.bac.pkudot edu.cn/~zj/scap/special/neo/1997br/.
Wish you all clear skies!
Jin
========================================================================
Jin Zhu | Tel.: +86-10-62759888 (O)
Beijing Astronomical Observatory | +86-10-68392030 (H)
Chinese Academy of Sciences | +86-314-5053035 (Schmidt dome)
P. R. China | Fax : +86-10-62759888
------------------------------------------------------------------------
email: zj@bac.pkudot edu.cn or jinzhu@sun.ihep.ac.cn
WWW Home Page: http://vega.bac.pkudot edu.cn/~zj
Pager: zhu@mail.263dot net.cn (only Sub. line) OR +86-10-64256688 PIN 82333
========================================================================
From Pierre Martin Jul 18, 98 07:02:17 pm -0400
> I observed last night under good clear skies. Unfo0rtunately, I was out just
> after midnight unbtil dawn when the sky cleared. I kept an eye out for
> possible
> meteors from 1997 BR, but nothing was seen. I will be out all night
> tonight. I have
> not seen such a good blue sky for a long time. Meteors from 1997 BR would
> be very slow and radiate from near Ursa Major.
From Michael Boschat Jul 18, 98 03:01:37 pm -0300
> The Chinese believe that there could be a possible meteor shower on the
> 19th caused by the asteroid 1997 BR from approx. RA 12h Dec +65d.
>
> I have been trying to detect them via radio at 83.25 MHz but there's
> seems to be some type of interference and I am not sure if it is
> Sporadic-E, can't get a reply from anyone if it is or is not.
>
> I did pick out the following meteors today July 18th:
>
> 1000-1100 UT 7/hr
> 1100-1200 7
> 1200-1300 10
> 1300-1400 5
> 1400-1500 4
>
>
> Contact Jin Zhu at zj@bac.pkudot edu.cn or jinzhu@sun.ihep.ac.cn
> about the shower
John Holtz write:
> Starting at about 9:50 pm EDT July 17 (1:50 UT July 18), there was an
> unexpected "shower" of meteors! The rate started out at 1 or 2 per minute, but
> then tapered down and virtually died out by 10:15 pm EDT. The meteor streaks
> were very short, only 1 or 2 degrees long. The magnitude was around 2. The
> trails faded out immediately. The meteors may have been concentrated around
> the Big Dipper, Draco, Bootes, and Hercules area. All of them were heading
> due south, so we couldn't determine a likely radiant.
References: