Smithsonian

Contributions to Astrophysics

VOLUME 4, NUMBER 3

ORBITAL ELEMENTS OF METEORS

by GERALD S. HAWKINS and RICHARD B. SOUTHWORTH

SMITHSONIAN INSTITUTION

Washington, D. C.

1961

Publications of the Astrophysical Observatory

This series, Smithsonian Contributions to Astrophysics, was inaugurated in 1956 to provide a proper communication for the results of research conducted at the Astrophysical Observatory of the Smithsonian Institution. Its purpose is the “increase and diffusion of knowledge” in the field of astrophysics, with particular emphasis on problems of the sun, the earth, and the solar system. Its pages are open to a limited number of papers by other investigators with whom we have common interests.

Another series is Annals of the Astrophysical Observatory. It was started in 1900 by the Observatory’s first director, Samuel P. Langley, and has been published about every 10 years since that date. These quarto volumes, some of which are still available, record the history of the Observatory’s researches and activities.

Many technical papers and volumes emanating from the Astrophysical Observatory have appeared in the Smithsonian Miscellaneous Collections. Among these are Smithsonian Physical Tables, Smithsonian Meteorological Tables, and World Weather Records.

Additional information concerning these publications may be secured from the Editorial and Publications Division, Smithsonian Institution, Washington, D.C.

FRED L. WHIPPLE, Director,

Astrophysical Observatory,

Smithsonian Institution.

Cambridge, Mass.

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. - Price 15 cents

Contents

Publications of the Astrophysical Observatory

Orbital Elements of Meteors

Acknowledgments

References

Orbital Elements of Meteors

By GERALD S. HAWKINS[1] and RICHARD B. SOUTHWORTH[2]

The meteors whose orbits we study here were chosen from the Baker Super-Schmidt photographs taken from stations at Doña Ana and Soledad, New Mexico, from February 1952 to July 1954. The photographs form a homogeneous and fairly continuous record of the night sky, the major interruptions being caused by periods of moonlight. The principle of the classical decimation process was used to ensure a random sample, every tenth meteor being chosen for analysis. Heights, velocities, and radiants for these meteors were given previously (Hawkins and Southworth, 1958). The orbital data were computed by the method of Whipple and Jacchia (1957).

The fundamental data for each meteor tabulated in our earlier paper included date, height of appearance, height of maximum light, height of disappearance, radiant, zenith distance of radiant, extrapolated extra-atmospheric velocity V∞, photographic magnitude at maximum light, and rise in magnitude above the plate limit.

The orbital elements of 359 meteors, computed by Whipple and Jacchia’s (1957) method, appear in table 1, which has been arranged to facilitate comparison with other papers in this volume of meteor papers. We omitted one meteor (1954 April 29.13439) because its velocity could not be determined. We assigned the orbit of the earth to two meteors (1953 April 11.14238 and 15.24742) whose velocities V∞ fall short of the velocity of escape. Each double-station meteor has two trails and two trail numbers; in the first column of the table we tabulate the trail number used by other investigators at Harvard. Forty-six of the meteors selected for our random sample had already been accurately reduced by Jacchia (Jacchia and Whipple, 1961) and are designated in the table by an asterisk; the tabulated values are his. The date (Universal Time) will permit identification of the meteor in our 1958 paper.

[1] Boston University and Harvard College Observatory.

[2] Harvard College Observatory.

Members of meteor showers included in the Whipple and Hawkins (1959, p. 545) list have been identified in the usual way. To conform with other papers in this volume, they are designated here in the following code:

Blank—Sporadic

1 —α Capricornid

2a—Southern Taurid-Arietid

3 —Southern ι Aquarid

4 —Geminid

5 —Southern δ Aquarid

7 —Perseid

8 —Orionid

9 —Draconid (Giacobinid)

10 —Quadrantid

17 —Northern Taurid

19 —Monocerotid

26 —Northern δ Aquarid

28 —Andromedid (Bielid)

33 —Northern ι Aquarid.

The successive columns in table 1 contain the orbital elements referred to the mean ecliptic and equinox of 1950.0: major semi-axis a, eccentricity e, perihelion distance q, aphelion distance q', argument of perihelion ω, longitude of ascending node , inclination i, longitude of perihelion defined here as π = ω + , and elongation of the true geocentric radiant from the earth’s apex λ. The values of a, q, and q' are expressed in astronomical units; the values of ω, , i, and π are expressed in degrees.

The standard deviation ΔV∞ of the extrapolated extra-atmospheric velocity V∞, as estimated from all the uncertainties in the reduction, is listed next as a guide to the accuracy of the result. We give no standard deviation for meteors analyzed by Jacchia; these were long trails of superior quality whose standard errors in V∞ would be less than 0.1 km/sec. The radiant was determined with comparatively small error, averaging seven minutes of arc. Representative values of the errors in the orbital elements that can arise from an error of 0.1 km/sec in V∞ are as follows:

These values may be multiplied appropriately for larger errors in V∞. In unfavorable cases the errors in the elements may be larger.

Whipple’s (1954) cosmic weight C.W. and comet-asteroid criterion K are tabulated in the next columns of table 1. The final column contains an approximate value of the mass m∞ of the meteor above the atmosphere, computed on the conventional model of the single-body meteor (Hawkins, 1957, equation (48)).

Acknowledgments

The research described in this paper was supported jointly by the U.S. Army, Navy, and Air Force under contract with the Massachusetts Institute of Technology. The photographic equipment was constructed and operated under contracts with the Air Force Cambridge Research Center and the Office of Naval Research. A few of the meteors included in the sample for statistical homogeneity had been reduced previously by Dr. L. G. Jacchia under contract with the Office of Ordnance Research.

References

HAWKINS, G. S.

1957. The method of reduction of short-trail meteors. Smithsonian Contr. Astrophys., vol. 1, pp. 207–214.

HAWKINS, G. S., AND SOUTHWORTH, R. B.

1958. The statistics of meteors in the earth’s atmosphere. Smithsonian Contr. Astrophys., vol. 2, pp. 349–364.

JACCHIA, L. G., AND WHIPPLE, F. L.

1961. Precision orbits of 413 photographic meteors. Smithsonian Contr. Astrophys., vol. 4, pp. 97–129.

WHIPPLE, F. L.

1954. Photographic meteor orbits and their distribution in space. Astron. Journ., vol. 59, pp. 201–217.

WHIPPLE, F. L., AND HAWKINS, G. S.

1959. Meteors. Handbuch der Physik, vol. 52, pp. 519–564.

WHIPPLE, F. L., AND JACCHIA, L. G.

1957. Reduction methods for photographic meteor trails. Smithsonian Contr. Astrophys., vol. 1, pp. 183–206.

Table 1. — Orbital Elements of a Random Sample of Meteors