Radar bounces off the sun

• Radar Echoes from the Sun
  • Radar was bounced off the sun.  A distinct pattern of long and short pulses were sent and received.
  • This confirms the sun is a physical object and the distance matches other measurements.
  • Link to publication: https://science.sciencemag.org/content/131/3397/329
  • Direct PDF Download: Radar Echoes from the Sun
• Radar Studies of the Sun at 38 MC/S
  • Jesse C. James, 1966
  • “About 1000 daily radar experiments have been made of the Sun at El Campo, Texas, since April, 1961. This paper presents some of the results of these experiments.”
  • “Briefly, one radar experiment is performed by transmitting a coded signal toward the Sun for 16 min., the round-trip time, and then receiving the echo for the following 16 min. The average transmitted power is 500 kw, and the antenna gain is 33 to 36 db relative to isotropic.”
  • Link to Publication: http://adsabs.harvard.edu/full/1966ApJ…146..356J
  • Direct PDF Download: RADAR STUDIES OF THE SUN AT 38 MC:S 1966
• Solar radar astronomy with the low-frequency array
  • Planetary and Space Science, Volume 52, Issue 15, December 2004, Pages 1391-1398
  • Paul Rodriguez
  • Review of previous measurements of the sun using radar.
  • Link to Publication: https://doi.org/10.1016/j.pss.2004.09.008
  • Direct PDF Download: Solar radar astronomy with the low-frequency array-2004-Rodriguez
• Plasma theory of solar radar echoes
  • V. N. Mel’nik
  • Institute of Radio Astronomy of National Academy of Sciences, Kharkov, Ukraine
  • published 13 May 2003
  • “Radar scattering by the ion-sound turbulence accompanied by Type III Langmuir turbulence is considered. It is shown that such scattering explains reflections from heights >1.6R0 observed by James [1966, 1970]”
  • Link to publication: https://doi.org/10.1029/2000RS002454
  • Direct PDF Download: Plasma theory of solar radar echoes-2000-V. N. Melnik
• Radar Probing of the Sun
  • PhD Thesis by Mykola Khotyaintsev
  • Link to publication: http://www.diva-portal.org/smash/get/diva2:169021/FULLTEXT01.pdf
  • Direct PDF Download: Radar Probing of the Sun-Khotyaintsev-2006
• Online discussion from CosmoQuest forums on bouncing Radar off the Sun with many links:
  • Can Radar be used to determine Sun’s distance if it’s not a solid mass?
• Some people have claimed that the sun is a “black body” therefore cannot bounce radar.  This is incorrect.
  • Discussion of the sun’s black body status:
    • “There is no such thing as black body. The concept of a black body is an idealization based on some simplifying assumptions. The Sun doesn’t exactly satisfy those simplifying assumptions.”
    • How can it be that the sun emits more than a black body?

Distance to the sun analysis from radar bounces

The first publication says the radar bounce took approximately 1000 seconds, the second approximately 16 minutes or 960 seconds. Taking the mean we get 980 seconds +- 20 seconds.

When bouncing radar it travels the distance twice, dividing the time in half we get 490 +- 10 seconds for the one-way time to the sun.

The speed of light is 299,792,458 m/s, Radar is part of the non-visible spectrum of light.

The distance is velocity * time.
299,792,458 * 490 = 146,898,304,420 meters
Calculating margin of error:
299,792,458 * 480 = 143,900,379,840 meters
299,792,458 * 500 = 149,896,229,000 meters

That’s between 89,415,551 miles and 93,141,199 miles.

Other measurements of the sun and other planets

• Radar Surveys of the Solar System
  • Earth to sun distance average:
    • 499.004786  light seconds
    • 149,597,871.3487 km
    • 92955807.676 miles
  • Mercury orbit average:
    • 0.387098414951 AU
    • 57,909,098.8791 km
    • 35,983,045.812 miles
  • Venus orbit average:
    • 0.723329859677 AU
    • 108,208,607.291 km
    • 67,237,711.323 miles
  • Link to publication: https://www.jstor.org/stable/985736?read-now=1&refreqid=excelsior%3A5adcc1b69794904193519c05a597c4b4
  • Direct PDF Download: Radar Surveys of the Solar System
• The astronomical unit determined by radar reflections from Venus
  • Weighted mean distance from earth to the sun:
    • 149,598,884 km +- 126km
    • 92,956,436.9 miles +- 78.3 miles
  • Link to publication: http://adsabs.harvard.edu/full/1962AJ…..67..191M
  • Direct PDF Download: The astronomical unit determined by radar reflections from Venus
• A Critical Discussion of the Abundance Results in the Solar Atmosphere
  • Discusses atomic compisition of the sun using Fraunhofer lines.
  • Primary:
    • H, He
  • Major light elements:
    • C, N, O, Na, Mg, Al, Si, S, Sc
  • Elements in Iron group:
    • Ti, V, Cr, Mn, Fe, Co, Cu
  • Rare elements:
    • Li, Be, P, K
  • Link to publication: http://adsabs.harvard.edu/full/1966IAUS…26..171M
  • Direct PDF Download: A Critical Discussion of the Abundance Results in the Solar Atmosphere
• The circular velocity at the sun
  • Solar rotation velocity is 220 km/s
  • Link to Publication: http://adsabs.harvard.edu/full/1979IAUS…84..225K
  • Direct PDF Download: The circular velocity at the sun 1979IAUS___84__225K
• Galactic chaos and the circular velocity at the sun
  • The available data favor a scale and model-free circular velocity at the Sun in the range 225-245 km/s with a most probable value of 235 km/s.
  • Link to Publication: http://adsabs.harvard.edu/full/1987AJ…..94..666C
  • Direct PDF Download: Galactic chaos and the circular velocity at the sun 1987AJ_____94__666C
• DETECTION OF A DEARTH OF STARS WITH ZERO ANGULAR MOMENTUM IN THE SOLAR NEIGHBORHOOD
  • “…we can make a dynamical measurement of the solar rotation
    velocity around the Galactic center:  239 +-9 km/s”
  • Link to Publication: https://iopscience.iop.org/article/10.3847/2041-8205/832/2/L25
  • Direct PDF Download: DETECTION OF A DEARTH OF STARS WITH ZERO ANGULAR MOMENTUM IN THE SOLAR NEIGHBORHOOD Hunt_2016_ApJL_832_L25

With a moderatly priced telescope, people can view the details of the sun themselves: