Statistical analysis of Chinese historical records of fireballs

Chin.Astron.Astrophys.11 (1987) 312-319 Act.Astrophys.Sin.-7 11987) 220-229

STATISTICAL

ANALYSIS

OF CHINESE

Pergamon Journals. Printed in Great Britain 0275-1062/87$10.00+.00

HISTORICAL

RECORDS

OF

FIREBALLS

LIU Xie-lin

Keywords

Institute for Thought and Culture, Tsinghuu University

Meteors - Fireball - Historical data analysis

Received 1986 May 29

ABSTRACT Apower spectrum analysis is applied to the yearly statistics of Chinese historical records of fireballs. The results show that sound is an important indicator of origin. Noisy fireballs have the following possible periods in years: 170.6tO.0, 102.4iO.0, 66.1t2.2, 27.320.4, 23.3kO.0, 17.9kO.4, 14.8_+0.1, 12.4f0.1, 10.5_+0.3. Noisy fireballs and meteorite falls have basically the same periods, and both originate in the asteroid belt. We think that the factors affecting both are the Yarkovsky effect and the perturbations by Jupitor. The 10.5-yr, 23.3-yr and 66.1-yr periods are related to the Yarkovsky effect and the 12.4-yr, 17,9-yr, 102.4-yr and 170.6-yr periods, to Jovian perturbations. The 14.8-yr and 27.3-yr periods may be due to the combined effect of the two, or to some other causes.

1.

INTRODUCTION

Meteors are phenomena caused by solid particles entering the Earth's atmosphere, and refer particularly to the light produced when the particles are ionized through interacting with the atmosphere. Fireballs denote those meteors with brightness exceeding the brightest planet, or a visual magnitude brighter than -5. Among the ancient Chinese records of meteors, there is a wealth of fireball data. In this paper, I mainly study sporadic fireballs. At present, it is generally accepted that meteor streams originate in comets. Whether sporadic meteors have a cometry or an asteroidal origin has remained a difficult question in meteor astronomy, with no agreed answers. Beginning in the '60's, scientific study of fireballs has been boosted up and a series of fireball observing networks have been set up. In the U.S.A. there is the Prarie Network (1963-1975) led by Whipple and McCrosky; in Czechoslavakia and West Germany, there is the European Network (1964present) led by Ceplecha. The objects observed by these two networks are generally brighter than magnitude -9. In Canada, there is the MORP Network (1971-present)led by Halliday. Based on data obtained by these observing efforts, astronomers have gained a series of results in their study of fireballs. Cepleche and McCrosky [I],

analysing the Prarie data, discovered that fireballs can be divided into 3 classes, with Class I made up of chondrites and Class II, of carbonaceous chondrites and Class III, of loose cometary material. It should be said that there have also been different opinions on this subject [Z]. In this paper, I shall attempt an investigation onthe origin of fireballs and their activity pattern, by applying a power spectrum analysis of Chinese historical records of these objects.

2:

ANCIENT RECORDS OF FIREBALLS OF CHINA

There is a wealth of records of sporadic meteors in China. From the beginning of written records until the year 1930, we can count several thousand entries. Most of these records refer to fireballs; for, in ancient times, only bright meteors would have aroused people's attention and have been written down. An example is the following entry: "Dynasty Song, Emperor Renzong, Reign Tiansheng, Year 6, Month 4, Day Jia-shen [lo29 May 141, when the night water-clock was nearly empty, there was a star as big as a bushel passing from N to SW. Its light lit up the ground. There was noise like thunder. A trail several zhang [several tens of degrees] in length was dragging behind which,

313

Chinese Historical Fireballs

TABLE1 PN Serial No. Velocity (km/s) -10.6

Mmax Total light* cos HE

ZR (km)

Ceplecha Class

~-

-10.5

-10.6

-8.6

13.55

13.44

13.79

13.51

0.626

0.881

0.640

0.623

68.9

57.1

41.7

35.1

111s

IllA

II

I

*integrated over the entire duration after a long while, dispersed into a pale white cloud",[3]. For convenience in statistical analysis, we must first make a classificationof the fireball records according to some parameter. The parameter should be closely related to the properties of fireballs. Ceplecha (1980, [4]) pointed out that of the parameters, initial velocity, maximum brightness, total energy emitted etc., only the height of terminal point HE is closely correlated with the structure and composition. See TABLE 1 reproduced from the Prarie Network data, [4]. From the table we see that fireballs having the same initial velocity, track inclination,maximum brightness and total emission can have very different terminal heights. Therefore, this is the parameter closest to the nature of the fireball. Of course, terminal heights are not given in ancient records. We now note that sound is closely correlated with terminal height. Millman's analysis of meteorite fireballs [S] showed that the average initial height of fireballs is 85 km, average terminal height is 17 km, and there is, in general, sound of explosion at the terminal point. Wetherill [6] analysed 25 meteorites from Hey's table of meteorites and found that 17 of them were accompanied by sound, 5 had unknown circumstance of fall, and for the remaining 3, it was recorded that the meteorite emitted a howling sound as it was about to fall to the ground. Fedynsky[7] pointed out that when a fireball enters within 55 km of the atmosphere, it will be accompanied by sound. Therefore we could say that sound is an indicator of whether or not the terminal height of the fireball is below 55 km, and is consequently a parameter that is probably related to the intrinsic property of the fireball. Accordingly, we first divide the fireball records into 3 groups and then analyse them separately. We consider all records that satisfy the following two conditions: 1) magnitude brighter than -5, corresponding

to the presence of such descriptions as "casting people's shadows" or "ground brightly lit" in the records and 2) no corresponding meteorite falls were found. Of these fireballs, those accompanied by sound, "with noise like thunder" etc. arelabelled Group I; those not so accompanied, Group III; and the union of Group I and Group III, that is, the entire set of records taken without regard to the presence or absence of sound, is labelled Group II. The source of our data mainly comes from the "General Catalogue of Records of Heavenly Phenomena of Ancient China" compiled by Beijing Observatory. The following points regarding the data should be explained. (1) Because we often encounter the situation where the same record is given in different annals with different dates or where the descriptions given in the official history and local gazettes are in conflict, we shall adopt the following conventions: (a) When the contents given in the official history and a local gazette are the same, but the dates are different and when the date in the latter is an obvious error (e.g., the month does not contain the sexagismal ganzhi date), then we follow the official history. (b) If the same record is given in several local gazettes, then we follow the one with the correct date. (cJ When the records in the official history and a local gazette belong to the same fireball, but the dates are different and both are possible, then we follow the official history if before 1500, and the local gazette if after. This is because, before 1500, local gazette accounts were often copies of the official account; it is only after 1500 that local gazettes became more or less independent. (2) For objects described as "tian gout' ("heavenly dog"), "Wang shi" ("bent arrow"), etc., we examine each record individually with regard to morphology and in the light of the work by Colleague Zhang Tian-shan [8], and accept or reject as the case may be.

LIU

314

3.

POWER SPECTRUM ANALYSIS OF YEARLY FREQUENCIES

To search for periodicity in the fall of fireballs, we take the year as unit and analyse the records statistically. Fig. 1 shows the yearly frequency distribution of Group I (noisy) fireballs.

400

500

,

600

after the year 1350. Before, the records are often broken, and the frequencies low; after, the records are continuous and the frequencies high. To decrease the uncertainity in the mathematical treatment, the entire series was divided into two, 29-1349 (A),and 1350-1930 (B). We assume each of the two series is a stationary process. The power spectrum of a time series gftl is obtained when we plot the amplitude l&l of the Fourier components in the Fourier expansion of g(t),

against the frequency Wn=ni2~/L), L being the total time span. If the spectrum shows a peak at W,, then it means that the time series contains the corresponding periodic component. The power spectra of Groups IA, IB and IIB were calculated and shown in Figs. 2-4. The periods obtained are given in TABLE 2.

iV0

F;l/rr.

Fig. 2

175u

Fig. 1

INJO

1850

lYO0

year

Yearly frequency of Group I fireballs from A.D. 30 to A.D. 1930.

We note that there is an obvious difference between the records before and

Power spectrum of Group IA fireballs (noisy, 30-1349)

From TABLE 2 we are led to the following conclusions: 1) Of the 11 periods present in Group IB (noisy, 1350-1930), no less than 8 coincide well with the periods in Group IA (noisy, 30-1349). Three show exact coincidence; these are 23.3, 102.4 and 170.6 yr. This adequately demonstrates that periodicities are indeed present in the time series of Group I (noisy) fireballs, andthatthe entire original series is basically a stationary process. 2) A comparison between the periods of Group IB and GroupIIB shows that they do not coincide completely. This means that the activities of noisy and soundless fireballs

Chinese Historical Fireballs

TABLE 2

Periods

PERIOD

-

Fireballs (China) ;roup IB

Group IA A.D.3o--134! _.___-

350--1Y30

Multiples N of

_-

Jupiter Period

China I

10.9

11.4 12.5

Falls

Meteorites

_-

12.3

and Meteorite

l-

._-

10.2

Fireball

(year)

roup IIB

ZSO--1930

10.8

of

315

12.5

World

474-1943 -___

800-197-i

10.6

10.3

10.8

11.4

11.3

12.1

12.5

009-1473 -.-

14.0

11.862 N

N

11.86

1

17.79

lf

13.9

14.8

14.7

14.9 15.5

16.8 17.6 18.3

18.3

21.3

22.3

23.3

23.3

27.0

27.0

16.0

16.0

17.7

17.7

19.6

20

22.0

22.6

17.7

23.72

2

29.65

21

35

35.58

3

47

41.51

31

59.31

5

24.3 27.0 28.2

29

30

32.6 3fJ.6

3ti.6

19.5 41.0 53.8 68.3

G4.0

102.4

102.4

170.6

170.6

63.5

64.0

60

Gl

1u5

110

175

175

265

106.7G

9

118.62

10

177.93

15

237.24

20

512.0 -

Note: The

meteorite

periods

are

taken

from

the

paper

POWI

by

ZHANG Shu-yuan

and YU Zhi-jun

[9].

Power

‘moor----

"'0°1' I

0.25 -

I0.00

0.10

0.2u

0.50

F.l/vr. Fig.

3

Power

spectrum

of

Group

(noisy, 1350-1929)

0.40

o 50

IB fireballs

Fig.

4

Power spectrum of Group IIB fireballs (all, 1350-1929)

316

a”

Chinese

Historical

TABLE Fireballs

(Group

IB)

10.2

11.4

12.5

317

Fireballs

3

14.9

17.6

27.0

36.6

64.0

-----

Meteorites

(1009-1473)

10.6

11.4

12.1

14.7

17.7

28.2

32.6

32.9

-----

Meteorites

(1474-1943)

10.3

11.3

102.4

170.6

105.

175

--63.5 --12.5

are not the same. In order to further reveal the differences between the two types, we compare the daily statistics (frequencies on given days of the year, over the years) of Group I (noisy) and Group III (soundless) fireballs. See Fig. 5. From Fig. 5, it is not difficult to see (a) that, as regards activity by day, the two types of fireballs behave entirely differently and (b) that Group I fireballs have no relation whatever with stream meteor activities in the course of the year, whereas Group III fireballs are closely correlated with meteor streams, the dates of their maximum frequency basically coincide with the dates of maximum stream meteor activity. Since meteor streams originate in comets, the above result shows that Group I fireballs are not connected with comets, while Group III are. This shows that the two types of fireballs are essentially different; the soundless fireballs have their origin in comets. 3) In TABLE 3, we compare the periods obtained here for Group IB fireballs with those of Chinese ancient meteorites obtained by YU and CHANG [9] using maximum entropy spectral analysis. We easily see that the activity periods of noisy fireballs and meteorites coincide well with each other. Such a close agreement, resulting from analyses from different data, by different methods, cannot be due to accident. Combining this result with that of the preceeding analysis of the daily frequencies, we are led to the inference that noisy fireballs and meteorites have the same activity pattern, and have a common origin. 4) Taking the periods present in both Group IA and Group IB data as reliable we now assert that noisy fireballs periods, possess the following periods in years: 170.3, 102.4, 66.1+ 2.2, 27.3? 0.4, 23.3, 17.9? 0.4, 14.8kO.1, 12.4+ 0.1, 10.5? 0.3. 5) Comparison with Fireball Studies In their analyses of outside China. Prarie Network fireball data, Ceplecha and McCrosky (1976, [1]) proposed the empirical criterion of terminal height, PE=log PE+A log m,+ B log V-/m+C log (cos ZR), in termsofthe initial mass mm, initial velocity V_, and the inclination of the track to the

13.9

17.7

vertical fireballs according Class Class Class Class

29.0

3.5

61

110

plane 2~. These authors divided into the following classes to the value of PE:

I: II: IIIa: IIIb:

the

-4.6O
Ceplecha (1977, [2]) pointed out that Class I have an extremely large bulk density (mean value 3.7 g/cm3); they are the usual chondritic meteoroids corresponding to the usual chondritic meteorites, hence have their origin in asteroids. The Class III objects have a density of 0.6 g/cm3 and there is direct evidence that they originate in comets. Class II have a low density of 2.1 g/cm3, made of carbonaceous chondrites. Class I and Class II fireballs have different distributions of orbital semi-major axes, hence are essentially different: Class II objects originate in cometary material. For comparison, the present writer made a statistical analysis of 28 fireball records in the 1977 Data of the European Network [lo] and found the following statistics of terminal heights: Terminal Height (km) maximum minimum mean Class

I

Class

II

Class

III*

7

One record erroneous.

53.54 kO.30 58.99 f0.05 88.07 0.04

25.7 +1.0 27.0 ro.2 56.8 0.4

with

&=32.4+

42.74 to.35 41.26 +0.55 71.48 0.2

is

of

number records 3 9 16

possibly

Thus, the terminal height is generally less than 55 km for both Class I and Class II, and hence these objects will be accompanied The material of Class III objects by sound. is so weak that even though they may have a mass between 100 and 1000 kg, they cannot, in general, penetrate the atmosphere to below 55 km and they will not produce any sound [II]. Since, like Class I objects, Class II objects are accompanied by sound, they should, according to our analysis, share

318

LIU

the same origin as the meteorites, and cannot originate in comets, as Ceplecha asserts.

4.

ANALYSISOF THE PERIODSOF FIREBALLFALLS

Our foregoing analysis led to the periods (in years) in the noisy fireballs listed in the first line of TABLE3. These periods are similar to the periods in meteorite falls; hence the noisy fireballs have the same origin as the meteorites. I now address the question “what are the physical factors connected with these periods?” (1) The periods of activity of noisy fireballs are not connected with comets. I have already stated that noisy fireballs are not connected with meteor streams,buthave a common origin with meteorites, hence their periods of activity are not connected with comets. I now cite further supporting evidence. Millman [12] has pointed out that, up to now, no meteoroidal matter originating in comets has ever been found on the Earth’s King (1976, 1131) also pointed out surface. that, there has so far been no evidence that any recovered meteorite is a sizeahle fragment of the solid body of a comet. Therefore, we think that the view held by YANGWei-hua et al. [14] that “when Earth passes through a cometary orbit, fragments of comet may fall on the Earth as meteorites”, Their belief that comets lacks evidence. affect meteorite falls is likewise unacceutable. (2) Noisy fireballs originate in asteroids and their activity periods are the result of modulation by Jupiter’s perturbation and the Yarkovsky effect. At present, the question of the origin of meteorites is not entirely clarified. A detailed analystical discussion on the present status of the studies of this problem has been given by Wasson and Wetherill [15]. Refs. 1151 and [16] cite much evidence in support of the statement that meteorites come from asteroids New evidence has been forthcoming that the Apollo-Amor asteroids are the latest parent bodies of meteorites [17]. These results were mainly obtained from photographic orbits of meteorites. l’be asteroid belt is the place of origin of the parent bodies of through various factors, certain meteorites: asteroids through orbit changes, evolve in their old age into the Apollo-Amor asteroids. The Apollo-Amor objects do not come from dead cometary nuclei. It is known that the transport of bodies from the main asteroid belt to the ApolloAmor type of orbits, is mainly affected by two factors + One is the Yarkovsky effect, that is, the gain or loss of angular momentumcaused by asymmetric re-emission of the solar radiation absorbed by a The other is perturbation by rotating body.

Jupiter. Fragments resulting from numerous collisions in the main asteroid belt are brought into Apoll-Amor type orbits by these factors. Since we believe that meteorites and noisy fireballs have a common origin, analyses on the former can apply to the latter. The results of this paper support the view that meteorites come from Apollo-&nor asteroids, and these latter come from the main asteroidal First we can see from TABLE2 that the belt. periods of fireballs, 12.4rO.l (=1x 11.861, 17.940.4 (=1.5x11.86), 23.3+0.0 (=2x11.86), 102.4io.o (=9x11.86), 170.5+0.0 (=15x11,86), reflect precisely the effect of Jupiter. Next, the variation of sunspot number reflects the solar activity, so we could say that the size of sunspot number reflects the variation in solar radiation. Chang and Yu [IS] and YANGet al. [14] both noted the fact that the number of sunspots in history varied basically in step with the recorded meteorite frequency. I have compared the frequency curves of noisy fireballs with that of sunspots given in Ref. [191 f and note that there is also a general agreement between the two. This shows that the three periods of noisy fireball falls, 10.5? 0.1, 23.3+ 0.0 and 66.1? 2.2 (=3x 223, are reflections of the solar cycle, As to the periods 27.3-r-0.4 and 48.1i1.1, they could be a combined effect of the Jupiter perturbation and the Yarkovsky effect, or due to some other causes.

5.

CONCLUSIONS

1. Sound is an important parameter informative of the origin of fireballs. Noisy fireballs possess the following possible periods in years: 170.0? 0.0, 102.4 10.0, 66.112.2, 27.3*0.4, 23.320.0, 17.9 t 0.4, 14.8i 0.1, 12.410.1, 10,Sf 0.3. These are basically the same as the periods found in meteorite falls. Noisy fireballs and meteorites share a colon origin. and meteorites come 2. Noisy fireballs from Apollo-Amor asteroids, and these, in turn, come from the main asteroid belt. The factors affecting the fall of noisy fireballs are the Yarkovsky effect and the perturbation The periods of noisy fireballs, by Jupiter. 10.5~ 0.3, 23.35 0.0, 66.1i2.2 are related The periods to the Yarkovsky effect. 12.4+O.l, 17.9+0.4, 23.320.0, 102.4+0.0, 170.6rtO.O are related to perturbations by Jupiter. originate in 3. Soundless fireballs cometary matter.

319

Chinese Historical Fireballs

REFERENCES ['I [2J

C+‘~lw Ceplecha,

Z., McCrosky, R. E.. J. Gcophyr. Rcr., 81 (lY76), 6257. 2.. Comets, Asteroids, Mcteorities, Univ. ul Toledo Press, 143.

[31 "Lidai Tianwen LUli Deng Zhi Huibian" ("General Compilation of Astronomical and Calendrical Chapters") Vo1.4. Zhonghua Books. p.1085. [4 1 Ceplecha Z., in "Solid Particles in the Solar System" = I.A.U. Symposium No. 90, ed. Halliday and McIntosh, 1980. 171. I'. M., Meteorite Research (1969), 541. LSl Millman,

[61

Wctherill,

G. W., Lctrcn

r71

Fcdynsky,

V., Mcteor~ (195Y),

.I. Gcophyr.

Rcr,

74(196Y),

MIXCOW Foreign

4402.

Languages

Publirhing

~oure,

36.

[81 ZHUANG Tian-shan in "Kejishi Wenji" ("Collectionof Essays on History of Science and Technology") Book 10, (1983). [Yl Yu, 2, Chang S., et al, Mem. Nnrr. Inrz. Polar Rrr. Spocr, lrsuc 30(1983), 362. [ 101 Crplecha, z. et al., Bull. Arrron. Inif. Czechurl., 34( 1983), 195. oj Arrronomy, 6(19X3), 391. 1’11 Simonenko, A. N., Lerin, B. J., Highligkrr [‘21 Millman, P. M., From Plasma to Planet (1972), (Alinguist 8: Wilnell Stock), 158. King E.A., "General Outline of Cosmic Geology" (Chinese translation P31 by WANG Daode et al.) (1983) Kexue Chubanshe. p.213. P41 YANG Wei-hua et al., Diqiu Huaxue ("Geochemistry")(1983) No.1, 52. Wasson,

.I. T. et al., Arrcroidr

Wood, J. A., The New Solar Lcvin,

B. J., Simonenko,

Client

Shuguan,

(1979),

Systrm

The Univ. (1981),

A. N., Icorur,

Yu Zhijun.

Mrm. Nat.

Arizona

Press. 926.

187.

47 (1981)

487.

Inrr. Polar

Rcr.

Spat. lirue.

20, 276.

DING You-ji, LUO Bao-rong and FENG Yong-ming Chin.Astron.Astrophys. 7 (1983) 24-30 = Act.Astron.Sin. 23 (1982) 287-298 PO1 Cook A.F., "Evolutionary and Physical Properties of Meteoroids" (1973). Pll ZHUANG Tian-shan, Chin.Astron. 1 (1977) 197-220 = Act.Astron.Sin., 14 (1966) 37-58. WI Love11 B., "Meteor Astronomy"