ZHR的计算与2001狮子座流星雨

2001年11月,天赐良机,让很多爱好者亲身体验到什么是流星暴雨。不过事后,一些观测者凭自己的印象,认为这次的狮子座流星雨的ZHR(即天顶每小时计数)值可能会达到七、八千,甚至上万。我在2002年2月12日(春节！)时又查了一下国际流星组织的网页,阿尔特于2002年1月25日给出的最新结果,2001年狮子座流星雨在北京时间2点左右的峰值ZHR,已经调整     

踏上红土地

每年12月中旬是著名的双子座流星雨来到的日子。与其他流星雨相比．双子座流星雨的ZHR值每年都能稳定在120左右。流星运行速度较慢且明亮,易于观测．又具观赏性,加上临近冬至日．昼短夜长．可以尽情地观看流光异彩飞舞于漫漫长夜。正因如此,天文爱好者们每年都冒着寒冬凛冽不疲于此。2007年12月13日～15日,我们几位北京的同好,受昆明晶华公司的邀请,     

2006年7月重要天象预告

7月28日南宝瓶座δ流星雨极盛7月12日～8月19日为南宝瓶座δ流星雨活跃期。7月28日流星雨达到极盛。流星雨极盛时辐射点的赤道坐标为赤经339°(22时36分)、赤纬-16°,靠近宝瓶座δ。ZHR(当辐射点位于天顶时,每小时的流星数)最大值达到20。7月28日月龄为2.9。7月～8月期间同时还是南宝瓶座ι和摩羯座α流星雨的活跃期。因此在这一天区可能看到很多流星。参见下图。     

2007年5月重要天象预告

2007年5月6日宝瓶座η流星雨极大宝瓶座η流星雨在"流星雨界"名气并不算大,但提起形成它的母彗星哈雷彗星,绝对是世人皆知。该流星雨的 ZHR 值可达60,在上半年为数不多的较大流星雨中已经算不错的了。由于凌晨三点多宝瓶座才会升起,观测这个流星雨只需要您早起两个小时,而且此时天气也不寒冷,监测它并不困难。不过5月6日20点极大值时在我国看不到,加之黎明前农历二十的月亮会严重干扰观测,而且天大亮前辐射点也不会升得很高,60的 ZHR 值要打上很多折扣,预计1小时能看到两三颗群内流星就已经很不错了。然而冲着哈雷彗星这颗我们中国人最先观测到的彗星,我们也应该在那个周日凌晨监测一下宝瓶座η流星雨。     

您准备好2001年狮子座流星雨的观测了吗

去年11月18日刚过,狮子座流星雨的观测就传来喜讯——其最强峰值ZHR(“每小时天顶标准计数”的英文缩写)超过400。图1给出国际流星组织发布的流星计数变化图。横坐标是以“太阳经度”表示的时间,纵坐标即是ZHR值。可见,在缓慢的增强过程中有几个峰值,而箭头所指的三个时刻,正是天文学家Asher和McNaught所预报的时刻！ 1999年初,英国天文学家Asher和澳大利亚国立大学的McNaught研究了一种计算彗星尘埃尾物质与     

重要天象预告

8月13日 英仙座流星雨极盛 今年7月7日-8月24日为英仙座流星雨极盛期。8月13日极盛,极盛时辐射点的坐标为赤经3时4分,赤纬 58°。在理想夜空(观测者可看到6.5等星)和理想地点(辐射点在天顶)的条件下可观测到的每小时流星数ZHR为100-110。当辐射点的天顶距为Z,实际可见     

2014年12月重要天象预告

12月2日 凤凰座流星雨 12月的天象被三场流星雨主宰,首先来临的是我们几乎从没听说过,但是在今年却值得推荐的一场流星雨——凤凰座流星雨。 凤凰座流星雨是一个很奇怪又神秘的流星雨,它只在1956年12月5日爆发过一次,ZHR达到300,从那之后就销声匿迹,每年的ZHR只有1～5左右。而它的母彗星D／1819 W1（Blanpain）也只在1819年被观测到过一次。这些现象都给凤凰座流星雨蒙上了一层神秘的面纱。     

论鲁庄公七年夏四月辛卯夜,恒星不见,夜中星陨如雨

对《春秋》记载的“鲁庄公七年(前687年)四月辛卯夜,恒星不见,夜中星陨如雨．”一段中的夜恒星何以当见而不见这个千古未解的迷团进行探讨,在1994年笔者研究的1533年狮子座流星雨出现时呈现的天空亮度的基础上,结合古今中外的有关资料, 发现这天恒星不见的原因,实际是夜中出现的流星雨产生的天空明亮掩盖恒星．文中附带证明恒星不见和星陨如雨实际是出现在同一时段,即都在夜中．同时还估算了这次流星雨的流星数密度和流星总数、掩盖恒星亮度的流星质量以及被掩盖恒星的天空面积．     

举办2001年狮子座流星雨摄影赛通知

鉴于2001年11月19日前后,在中国东部、中部,有可能观测到每小时标准天顶计数峰值达到一万颗以上流星的狮子座流星暴雨。为促进这一可能的、罕见的流星雨观测和保留珍贵的流星雨资料,我们决定举办《2001狮子座流星雨摄影赛》。我们在全国范围内(包括港、澳、台)征集狮子座流星雨的观测照片。来稿要求为: 1.提供拍摄有狮子座流星的5对以上     

偶见天龙座流星雨

我曾经作多次流星雨的观测,可一直没见过令人兴奋的场面。１９６５年我就曾观测过狮子座流星雨,可就只见到几颗流星。去年的狮子座流星雨,我们在严寒难耐的冬夜坚守观测了４个小时,也只见到１７颗流星。１９９８年６月２７日夜晚,我们偶然和天龙座流星雨相遇,一颗接...     

The activity of the 2004 Geminid meteor shower from global visual observations

A comprehensive set of 612 h of visual meteor observations with a total of 29 077 Geminid meteors detected was analysed. The shower activity is measured in terms of the Zenithal Hourly Rate (ZHR). Two peaks are found at solar longitudes     and     with  ZHR = 126 ± 4  and  ZHR = 134 ± 4  , respectively. The physical quantities of the Geminid meteoroid stream are the mass index and the spatial number density of particles. We find a mass index of   s ≈ 1.7  and two peaks of spatial number density  234 ± 36  and  220 ± 31  particles causing meteors of magnitude +6.5 and brighter in a volume of 10⁹ km³, for the two corresponding ZHR maxima. There were  0.88 ± 0.08  and  0.98 ± 0.08  particles with masses of 1 g or more in the same volume during the two ZHR peaks. The second of the two maxima was populated by larger particles than the first one. We compare the activity and mass index profiles with recent Geminid stream modelling. The comparison may be useful to calibrate the numerical models.     

Evolution of the Geminids Observed Over 60 Years

Visual observations collected over 60 years (1944–2003) are analysed. The profiles and values of the population index near the activity peak are rather constant over the entire period and confirm the strong mass segregation within the stream. The peak activity is characterized by a plateau in the profile with a ZHR between 120 and 130 lasting for about 12 h between λ_⊙=261.5° and 262.4° (J2000). This is consistent with an age of the Geminid stream of about 6000 years. The position of this plateau is constant. Variations of the ZHR by more than 10% within the peak period are found in data of well-observed returns. These structures of about 0.2° duration can be traced over more than a decade with an average drift of about −0.02° in solar longitude per year     

Observational effect for the lunar gravity on meteor streams

Meteoroids always posed a great hazard to spacecraft security. A meteoroids stream assembled by a large massive body will further enhance the hazard severalfold. For example, the radiant of Northern Taurids (NTA) will be occulted by the Moon on Nov. 12, 2011. Since the gravitational lensing effect of massive bodies can gather together the orbits of meteoroids, the observable flux of meteoroids will increase. In this paper a set of numerical methods was built to discuss the observational effect of this kind of phenomena. The ZHR of NTA is generally small. But it can be local strong on the Earth by the lunar gravitational assembling. The calculated result suggests that a ten times stronger than normal NTA will appear in the sea area of Tristan da Cunha islands during 00h45m UT to 02h00m UT on Nov. 12, 2011.     

Taurid resonant-swarm encounters from two decades of visual observations

Enhanced Taurid activity in terms of visual meteor and fireball rates has been found in 1988, 1991, 1995, 1998 and 2005 data. The years of heightened activity are shown to be unequivocally linked to the encounters of swarms of resonantly trapped particles in the Taurid meteoroid stream according to the model proposed by Asher & Clube. While the annual activity level of the Taurid meteor shower in terms of zenithal hourly rate  (ZHR) is 7.8 ± 1.2  , swarm year activity typically reaches ZHRs of 12–17. The annual fraction of fireballs is below 1 per cent; in swarm years, this fraction is as high as 2.4–4.6 per cent near the maximum of the Taurid activity period.     

The Orionid Meteor Shower Observed Over 70 Years

Visual Orionid meteor data dating back to 1944 were transformed into the standard format of the Visual Meteor Data Base (VMDB) of the International Meteor Organization (IMO) for systematic analysis. The strong 2006 Orionid return with a very low population index (r = 1.6) and a peak ZHR of 60 (about 2.5 of the average peak strength) resembled meteor showers connected with the returns of resonant meteoroids. An investigation of data dating back to 1928 yielded similar rate enhancements in 1936, further supporting the assumption that meteoroids trapped in the 1:6 resonance with Jupiter caused the unusual 2006 Orionid return.     

Visual Observations Of The Leonid Meteors 1998 In Yunnan

The 1998 Leonid meteor shower was observed at the Gaomeigu station of Yunnan Observatory during five successive days in November. The visual records indicate that the number of meteors increased suddenly, from a ZHR of about 140 to over 400, in the early morning of November 17th, Beijing time. But it decreased slowly in the following two days. During the maximum there was a high proportion – about 10 percent – of very bright fireballs with enduring trains. The brightest one was about -10 magnitude with a smoke train fading about three minutes after. This revised version was published online in July 2006 with corrections to the Cover Date.     

Detection of 2009 Leonid,Perseid and Geminid Meteor Showers through its effects on Transmitted VLF Signals

The detection of 2009 Leonid, Perseid and Geminid meteor showers over Agartala, Tripura, India (Lat: 23.0° N, Long: 91.4° E) will be reported here by using two VLF receivers tuned to subionospheric transmitted VLF signals at the frequency 16.4 kHz from Aldra Island, Norway (Lat: 66.42° N, Long: 13.13° E) and the other at 18.2 kHz from Vijayananarayanam, India (Lat: 8.4° N; Long: 77.7° E). The received signals exhibited their peak values on November 17, 2009 when ZHR (Zenithal Hourly Rate) was highest. Some typical variations which are observed in the records of amplitude during the 2009 Leonid, Perseid and Geminid meteor showers will be presented in this paper.     

Leonids 2006 observations of the tail of trails: Where is the comet fluff?

In 2006, Earth encountered a trail of dust left by Comet 55P/Tempel-Tuttle two revolutions ago, in A.D. 1932. The resulting Leonid shower outburst was observed by low light level cameras from locations in Spain. The outburst peaked on 2006 Nov. 19d 04h39m ± 3m UT (predicted: 19d 04h50m ± 15m UT), with a FWHM of 43 ± 10 min (predicted: 38 min), at a peak rate of ZHR=80±10/h (predicted: 50-200 per hour). A low level background of older and brighter Filament Leonids (χ∼2.1) was also present, which dominated rates for Leonids brighter than magnitude +4. The 1932-dust outburst was detected among Leonids of +0 magnitude and brighter. These outburst Leonids were much brighter than expected, with a magnitude distribution index χ=2.60±0.15 (predicted: χ=3.47 and up). Trajectories and orbits of 24 meteors were calculated, most of which are part of the Filament component. Those that were identified as 1932-dust grains penetrated just as deep as Leonids in past encounters. We conclude that larger meteoroids than expected were present in the tail of the 1932-dust trail and meteoroids did not end up there because of low density. We also find that the radiant position of meteors in the Filament component scatter in a circle with radius 0.39°, which is wider than in 1998, when the diameter was 0.09°. This supports the hypothesis that the Filament component consists of meteoroids in mean-motion resonances.     

TVZHR profile for the 1991 Perseid shower

Image intensified video detection systems were used to observe the 1991 Perseid meteor shower from two locations in eastern Canada. In 29.6 hours of total observing time a total of 668 meteors were detected, of which 403 were Perseids. We derived a profile of TVZHR (television zenithal hourly rate) values for the 1991 Perseid shower over the solar longitude (epoch 2000) interval 138°51 to 141°01. The apparent limiting stellar magnitudes of the observing systems were +9.4 and +8.8 (corresponding to limiting meteor magnitudes for our geometry ranging from +8.7 to +7.0). Within the observing period, the maximum TVZHR rate was approximately 1600, and occurred at solar longitude 139.9°. This is in good agreement with the second peak observed by visual observers. The data suggest that TVZHR values should be divided by a factor of approximately 5 to compare TVZHR and ZHR values.