Lunar Occultation of the Radio Source CTA 21

R. W. CLARKE; R. A. BATCHELOR

doi:10.1038/207511a0

78. The lunar occultation of a radio star and the derivation of an upper limit for the density of the lunar atmosphere

Symposium - International Astronomical Union ◽

10.1017/s0074180900049536 ◽

1957 ◽

Vol 4 ◽

pp. 403-405 ◽

Cited By ~ 1

Author(s):

B. Elsmore

Keyword(s):

Radio Source ◽

Large Diameter ◽

Circular Region ◽

Radio Brightness ◽

Interferometric Method ◽

Filamentary Structure ◽

Lunar Occultation ◽

Upper Limit

Observations were made at Cambridge on 26 April 1955 of the lunar occultation of the large-diameter radio source in the constellation of Gemini. This radio source, having r.a. 06h 13m 37s and dec. 22° 38′ (1950·0), has been identified by Baldwin and Dewhirst (1954) [1] as the galactic nebulosity IC443, which consists of a filamentary structure contained within a circular region of 24′·5 radius. Baldwin and Dewhirst also succeeded in measuring the distribution of radio ‘brightness’ across the source using an interferometric method; their measurements indicate that the diameter of the radio source is approximately the same as that of the visible nebulosity.

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Lunar Occultation of the Radio Source 3C 273

Nature ◽

10.1038/201755a0 ◽

1964 ◽

Vol 201 (4921) ◽

pp. 755-756 ◽

Cited By ~ 9

Author(s):

J. A. BAILEY ◽

N. J. B. A. BRANSON ◽

B. ELSMORE ◽

P. A. G. SCHEUER

Keyword(s):

Radio Source ◽

Lunar Occultation

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Lunar Occultation of a Radio Source

Nature ◽

10.1038/191058a0 ◽

1961 ◽

Vol 191 (4783) ◽

pp. 58-58 ◽

Cited By ~ 6

Author(s):

C. HAZARD

Keyword(s):

Radio Source ◽

Lunar Occultation

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Radio observations of the lunar atmosphere

Symposium - International Astronomical Union ◽

10.1017/s007418090005052x ◽

1959 ◽

Vol 9 ◽

pp. 47-49

Author(s):

B. Elsmore

Keyword(s):

Radio Source ◽

Crab Nebula ◽

Large Diameter ◽

Radio Observations ◽

Radio Brightness ◽

Lunar Occultation ◽

Terrestrial Atmosphere ◽

Accurate Position ◽

The Crab Nebula

Observations of a lunar occultation of a radio source may provide information concerning both the distribution of radio “brightness” across the source and its accurate position. For sources of which these results are already fairly well known, observations at long wavelengths may be used to derive the density of the lunar atmosphere [1]. During recent years two such occultations have been observed at Cambridge: one, the occultation of IC 443, the large-diameter radio source in the constellation of Gemini, from which the density of the lunar atmosphere was estimated to be less than 10–12 of that of the density of the terrestrial atmosphere [2] and [3]; and two, the occultation of the Crab nebula on 1956 January 24 [4].

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Lunar Occultation of the Radio Source 3C 273

Nature ◽

10.1038/201756a0 ◽

1964 ◽

Vol 201 (4921) ◽

pp. 756-757 ◽

Cited By ~ 4

Author(s):

R. G. CONWAY ◽

C. G. T. HASLAM ◽

P. P. KRONBERG ◽

C. H. SLATER

Keyword(s):

Radio Source ◽

Lunar Occultation

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The road to quasars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315002185 ◽

2014 ◽

Vol 10 (S313) ◽

pp. 190-195 ◽

Cited By ~ 2

Author(s):

K. I. Kellermann

Keyword(s):

Radio Source ◽

Optical Measurements ◽

Radio Sources ◽

Optical Counterpart ◽

Owens Valley ◽

True Nature ◽

Radio Observatory ◽

The Road ◽

Lunar Occultation ◽

Faint Galaxy

AbstractAlthough the extragalactic nature of 3C 48 and other quasi stellar radio sources was discussed as early as 1960 by John Bolton and others, it was rejected largely because of preconceived ideas about what appeared to be unrealistically high radio and optical luminosities. Not until the 1962 occultations of the strong radio source 3C 273 at Parkes, which led Maarten Schmidt to identify 3C 273 with an apparent stellar object at a redshift of 0.16, was the true nature understood. Successive radio and optical measurements quickly led to the identification of other quasars with increasingly large redshifts and the general, although for some decades not universal, acceptance of quasars as the very luminous nuclei of galaxies.Curiously, 3C 273, which is one of the strongest extragalactic sources in the sky, was first cataloged in 1959 and the magnitude 13 optical counterpart was observed at least as early as 1887. Since 1960, much fainter optical counterparts were being routinely identified using accurate radio interferometer positions which were measured primarily at the Caltech Owens Valley Radio Observatory. However, 3C 273 eluded identification until the series of lunar occultation observations led by Cyril Hazard. Although an accurate radio position had been obtained earlier with the OVRO interferometer, inexplicably 3C 273 was initially misidentified with a faint galaxy located about an arc minute away from the true quasar position.

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An Investigation of the Radio Source 06N2A in Gemini

Australian Journal of Physics ◽

10.1071/ph560494 ◽

1956 ◽

Vol 9 (4) ◽

pp. 494 ◽

Cited By ~ 9

Author(s):

H Rishbeth

Keyword(s):

Radio Source ◽

Lunar Occultation

A lunar occultation of the radio source 06N2A in Gemini was observed in the course of an investigation at a wavelength of 3�5 m, for which the "Mills Cross" aerial was employed. During the occultation the intensity of the source was reduced by over one-fifth, although less than one-tenth of the associated galactic nebulosity IC 443 was obscured. The radio source appears to resemble the nebula, and the relation between them is discussed with the aid of simple geometrical models of the source.

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