Solar Parallax Research Articles

Quasi-stereoscopic imaging of the solar X-ray corona

The first published three-dimensional images of the solar X-ray corona, obtained by means of solar rotational parallax, are presented in stereographic form. Image pairs approximately 12 hours apart during times of stable coronal conditions were selected from the digitized images obtained with theSkylab X-ray Spectrographic Telescope. The image resolution limit is approximately 10 arc sec. Many coronal structures not visible in the separate images are clearly observed when the image pairs are viewed stereoscopically. This method gives a preview of the potential resources for solar research and forecasting of solar-geomagnetic interactions that could be provided by stereoscopic observations of the Sun using a small group of spacecraft. The method is also applicable to other X-ray, ultraviolet, or other wavebands in which the corona has extended, transparent structure.

The United States Naval Astronomical Expedition (1849–52) for the Solar Parallax

The United States Naval Astronomical Expedition (1849–52) for the Solar Parallax

A simple, accurate, geometrical approximation to the Keplerian motion

A new method which shows, simply and accurately, the planetary position as a geometrical point in the orbit as a function of time is presented. By comparison with the historical hypotheses of planetary motion, it is thus visually recognizable how such hypotheses, especially those propagated in the 17th century, approached the Keplerian motion geometrically by means of observations. The reason why such a mathematically accurate hypothesis as that presented here was not developed previously, say in the 17th century, was due mainly to the inaccurate values for the solar parallax involved in the observations of that time.

Captain James Cook and The Royal Society

Foremost among the scientific societies of Europe the Royal Society took the initiative in making the necessary preparations for the observations of the transit of Venus in the eighteenth century, when this phenomenon occurred only twice. Such observations were necessary in order to enable the calculation of the solar parallax to be made. The observations of the transit of Venus in 1761 proved to be unsatisfactory and consequently the transit of 1769 was looked forward to with great anticipation. In 1766 Council embarked on the preliminary arrangements for the observation of the forthcoming transit. Exertions were made to engage the most competent observers and instruments were recalled and put in good order. The result of their deliberations was a Memorial to the King in February 1768. The memorialists, after stating the reasons for the desirability of the observations, proposed several localities where the observations should take place. One such locality was '. . . any place not exceeding 30 degrees of Southern latitude, and between the 140th and 180th degrees of longitude West . . .’. The King immediately granted the prayer of the memorialists and ordered a sum of ‘ £4,000 clear of fees’ to be paid to them. The Astronomer Royal, Nevil Maskelyne, F.R.S., was directed by the Council of the Royal Society to prepare the necessary instructions for the observers, Messrs Dymond and Wales, who were to be sent to Hudson Bay; Mr Call to Madras; and Lieutenant Cook and Mr Green to the Pacific. The instructions for Lieutenant Cook and Mr Green are recorded in Council Minutes (1). ( See Appendix A.) The expedition to the Pacific had for its main, but not exclusive object, the observation of the transit by Mr Green and was placed under the command of Lieutenant James Cook who hoisted his pennant in the Endeavour .

Radar determination of the Astronomical Unit

A comprehensive review is given of the Earth-Venus measurements made with the Lincoln Laboratory Millstone radar in 1959 and 1961. The time-delay and Doppler shift data yield a value for the Astronomical Unit of 499.0052 ± 0.001 light-sec. Using 299 792.5 km/s for the speed of light leads to an AU of 149 598 000 ± 300 km. With the radius of Earth taken as 6 378.15 km, the solar parallax then becomes 8″.79416 ± 0″.00002. This value is consistent with measurements made at various other laboratories to about one part in 105.

On the compatibility of the recent solar parallax results from radar echoes of Venus with the motion of Eros

The author investigates whether the adoption of a value of the solar parallax determined by radar measures would permit an acceptable representation of the observations of Eros. The solution he obtaines leaves important residuals and leads to a rather unlikely value for the mass of Mars.

Astronomical constants: a survey of determined values

The authors give the main relations between fundamental and derived constants in analytical and numerical forms. Then, they enumerate and comment results of determinations of parameters of the figure and gravity field of the Earth, solar parallax, constant of lunar equation, the masses of planets, the constants of aberration, of nutation and of precession and give an extensive list of references.

The constant of nutation and the system of astronomical constants

The author discusses the dependence of the constants of nutation and precession upon the values of other fundamental constants such as the dynamical ellipticity of the Earth, the mass of the Moon and the solar parallax in the case of two different theoretical models of the Earth.

Inaugural address Delivered at the I.A.U.-Symposium no. 21

After a presentation of the problem posed by the construction of a system of astronomical constants, the author describes the new catalogue FK 4. He then reviews recent progress in the knowledge of the orbits of major planets and in the determination of solar parallax, the constant of aberration and the constant of precession.

Constants related to the Earth and Moon

The author discusses various determinations of zonal and tesseral harmonics of the Earth's gravitational field, the values of the solar parallax, and the constants related to the figure of the Moon and its motion.

A radar investigation of Venus

Radar measurements of Venus carried out by the Millstone radar of the Massachusetts Institute of Technology Lincoln Laboratory from 6 March to 18 May 1961 are reported. Range measurements reduced with the help of Duncombe's elements for the orbits of the earth and Venus lead to a value for the astro- nomical unit of 149 597 850+400 km. Reduced with 6378.388 km for the earth's equatorial radius, this yields for the solar parallax irO = 8'.' +0'.'000024. Small residual systematic errors in the planetary ephemerides are disclosed. Measurements of the signal intensity and range dispersion are compatible with a relatively smooth rocky surface as the reflecting agency. The observed frequency broadening is com- patible with a sidereal rotational period of 225 (+275, -110) days, which suggests that the period of rotation equals the period of revolution.

The astronomical unit determined by radar reflections from Venus

view Abstract Citations (23) References (4) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The astronomical unit determined by radar reflections from Venus Muhleman, D. O. ; Holdridge, D. B. ; Block, N. Abstract Radar reflections from the surface of the planet Venus at a wavelength of 12.5 cm yielded a value of the astronomical unit of 149 598 845+250 (p.e.) km, or a solar parallax of 8"7940976+147 based on an earth radius of 6378 145 m. The computations were accomplished utilizing Doppler-frequency-shift and time-of- flight observations (range measurements) in conjunction with the "best" available planetary ephemerides of the earth and Venus. The investigations yielded proof of the transparency of the Venus atmosphere at 12.5 cm and some information on the radius of Venus. Systematic errors in the published ephemerides are also discussed. Publication: The Astronomical Journal Pub Date: May 1962 DOI: 10.1086/108693 Bibcode: 1962AJ.....67..191M full text sources ADS |

Radar Observation of Venus

Radar observations of Venus during the last close approach have resulted in a value of solar parallax of 8.79460 seconds of arc, corresponding to a value for the astronomical unit of 149,596,000 km. This is in satisfactory agreement with the determinations made, during the same close approach of Venus, at the Millstone Hill Radar Observatory and at Jodrell Bank, which are 149,597,700 km and 149,601,000 km, respectively. The size of the astronomical unit heretofore generally accepted as most authoritative is based upon a 1950 determination by Rabe, and is 149,532,200 km.

A New Determination of the Solar Parallax by Means of Radar Echoes from Venus

DURING the recent close approach of Venus the Jodrell Bank radio telescope has been used to obtain radar echoes from the planet. The radar equipment, which operated at a frequency of 408 Mc./s., had a peak-power of 60 kW. and gave 30-m.sec. pulses at one pulse per second. The transmitter and receiver were operated alternately for periods of approximately five minutes, the light-time to Venus and back. To eliminate fading caused by Faraday rotation of the line of polarization of the signals in the Earth's ionosphere, an aerial system transmitting right circular polarization and receiving left circular was used. This was achieved by means of a feed aerial consisting of crossed coplanar dipoles and reflectors fed in quadrature from a hybrid ring, which also provided 40 db. of isolation between the receiver and transmitter. An electron-beam parametric amplifier (Adler tube) with a noise figure of 2 db. formed the input to the receiver.

Radar echoes from Venus and a new determination of the solar parallax

Radar echoes from Venus and a new determination of the solar parallax

A Dynamical Determination of the Astronomical Unit by a Least-Squares Fit to the Orbit of Pioneer V.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Dynamical Determination of the Astronomical Unit by a Least-Squares Fit to the Orbit of Pioneer V. McGuire, J. B. ; Morrison, D. D. ; Wong, L. Abstract Squares Fit to the Orbit of Pioneer V. J. B. McG~i~~, D. D. MORRISON, AND L.WONG, Space Technology Laboratories, Inc., Los Angeles, California (introduced by GUIDO M~~~c~). -The astronomical unit has long eluded precise determination because it enters the two-body Kepler problem as a scale factor, and as a scale factor changes in the size of the astronomical unit do not change any angular measurement. Since angles are the primary measured quantitites of classical astronomy, the astronomical unit does not enter the dynamics and thus the astronomical unit has been determined by geometrical means (i.e., measuring solar parallax). If, however, one is concerned with a three-body problem, the effect of a change in the astronomical unit is to add a secular (i.e., time-increasing) perturbation to the motion. This effect has been utilized by E. K. Rabe (1950, Astron. J. 54, 112) in the so- called dynamical method of astronomical unit determination. It was first suggested by R. C. Booton (1960, Space Technology Laboratories Tech. Rept. 60-0000- 00215) that the orbit of an interplanetary probe could be affected (since it is a three-body problem) by a change in the astronomical unit, and thus the astronomical unit should be measurable by a least- squares fit to the radio Doppler data from such a probe. Previous determinations of the astronomical unit have been made by both dynamical and geometrical means. The most recent of the dynamical measurements is that of Rabe, which has a quoted accuracy of *4~4 parts in 10~. The most recent geometrical measurement is that of Spencer-Jones (1941, Mcm. Roy. Astron. Soc. LXVI, Part II) which has a quoted accuracy of *1.1 parts in 10~. The measured values of the astronomical unit, however, differ by one part in 10~. At the time of writing of this abstract the tracking of the Pioneer V probe is incomplete; thus the accuracy of the measurement of the astronomical unit is as yet unknown. Unfortunately, radio contact with Pioneer V will not be maintained to a sufficient distance from the earth to effect any improvement in the uncertainties in the astronomical unit quoted by Rabe. It is hoped, however, that sufficient accuracy will be attained to lend more weight to either Rabe or the Spencer-Jones value of the astronomical unit. It will be shown that Doppler tracking of an interplanetary probe to a distance of 80000000 miles from the earth could yield a value of the astronomical unit which is competitive in accuracy with Rabe's determination. Supported by National Aeronautics and Space Administration. Publication: The Astronomical Journal Pub Date: 1960 DOI: 10.1086/108136 Bibcode: 1960AJ.....65R.493M full text sources ADS |

The solar parallax and the hydrogen line.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The solar parallax and the hydrogen line. Lilley, Edward ; Brouwer, Dirk Abstract The use of absorption lines in the spectra of discrete sources as frequency standards is examined. Such lines appear to be particularly attractive for a measurement of the solar parallax. Produced by the hyperfine transition F = 0 H F = I, the absorption lines are the sharpest features known in 21 cm research. An interstellar Hi cloud which produces the absorption line, has some velocity with respect to the sun. By measuring the exact frequency of the line on two occasions about six months~ apart, one can eliminate the cloud's constant motion and obtain a value of the earth's orbital velocity. The velocity measurements permit one to compute the solar parallax. This is a standard method with stellar radial velocities which, because of optical limitations, has not been successful in improving knowledge of the solar parallax. However, by shifting the experiment into the radio domain, sufficiently precise Doppler measurements are possible. A number of calculations have been performed to investigate the accuracy of the hydrogen line-solar parallax experiment. We find that it is a "time-limited" problem, and that two basic quantities compete to limit the precision of a single measurement. The quantities are: (I) The natural rate, d(Av)/dt, at which the absorption line shifts frequency due to the orbital and rotational motions of the earth. (2) The minimum time, T, during which a given radio telescope and receiver combination, working on a particular source, can achieve a measurement accuracy of ~f cycles. The expressions for (i) and (~) are: d(Av) v0k dH dt = c cos6cos~cosH dt (i) T = 2())1(4T)f)1 (Ts + TR)2, (2) where the symbols have their usual definitions in spherical and radio astronomy. The total annual hydrogen line Doppler shift for a source on the ecliptic is of the order 3 X io~ cycles. Thus the accuracy with which the parallax may be determined becomes lf/3 X 100. A new hydrogen line radiometer is being designed and developed, funded by the National Aeronautics and Space Administration. The performance goal for the radiometer is bf = I cycle, leading to an accuracy goal of about one part in 3 X io~ for the solar parallax. The solar parallax `observational program will extend over several years and will be conducted at the Naval Research Laboratory and at Agassiz Station `of Harvard College Observatory. Harvard College Observatory Cambridge, Mass. and Vale University Observatory New Haven, Conn. Publication: The Astronomical Journal Pub Date: 1959 DOI: 10.1086/108033 Bibcode: 1959AJ.....64R.338L full text sources ADS |

British Preparations for Observing the Transit of Venus of 1761

WO important astronomical events that aroused the educated world and resulted in the greatest co-operative enterprises in the history of science to that time took place during the latter half of the eighteenth century. The preparations for the observations were accompanied by considerable excitement, for the transits of Venus in I76i and I769, properly observed from various points on the earth's surface, would enable astronomers to determine the solar parallax and thereby obtain the distance between the earth and the sun. Once this was accomplished, other distances in the solar system then known only relative to one another could be computed, and the Newtonian system of the world could be brought closer to completion by the determination of its exact scalar dimensions.' For the historian of science, the attempted determination of those dimensions in I76i is truly important. In a broader sense, however, the preparations for the large-scale international effort to view the transit throw some light on the relations between science and society in the Age of Reason. On either side of the Atlantic the British world combined private and public funds and institutions in what proved, in both cases, to be a prelude to more successful observations in I769. The very idea that the transits of the planet Venus might serve as a natural astronomical instrument for determining the size of the universe was due to Edmund Halley.2 But for a long time following the announce-

Additional note on the solar parallax from Eros

view Abstract Citations (5) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Additional note on the solar parallax from Eros Rabe, Eugene Abstract : The consideration of the uncertainty of the precessional constant, as well as of the inconsistency of the initially adopted values of the constant of aberration and the solar parallax, does not lead to any significant increases for the prob- able errors of the Eros solution. Publication: The Astronomical Journal Pub Date: November 1954 DOI: 10.1086/107053 Bibcode: 1954AJ.....59..409R full text sources ADS |

Royal Society: Medal Awards

HIS Majesty the King has been graciously pleased to approve the recommendations made by the Council of the Royal Society for the award of the two Royal Medals for the current year as follows: to Sir Harold Spencer Jones, Astronomer-Royal, for his determination of the solar parallax and of other fundamental astronomical constants ; to Dr. E. B., Bailey, director of H. M. Geological Survey, for his distinguished contributions to the knowledge of mountain structure and his studies on the tectonics of vulcanism.