Solar radius

Last updated
Conversion of nominal solar radius
1 R☉ =Units
6.95700×108 metres
695,700 kilometres
0.00465047 astronomical unit
432,288 miles
7.35355×10−8 light-year
2.25461×10−8 parsec
2.32061 light-seconds

Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun's photosphere where the optical depth equals 2/3: [1]

Contents

695,700 kilometres (432,300 miles) is approximately 10 times the average radius of Jupiter, 109 times the radius of the Earth, and 1/215th of an astronomical unit, the approximate distance between Earth and the Sun. The solar radius to either pole and that to the equator differ slightly due to the Sun's rotation, which induces an oblateness in the order of 10 parts per million. [2]

Measurements

Evolution of the solar luminosity, radius and effective temperature compared to the present-day Sun. After Ribas (2009) Solar evolution (English).svg
Evolution of the solar luminosity, radius and effective temperature compared to the present-day Sun. After Ribas (2009)

The uncrewed SOHO spacecraft was used to measure the radius of the Sun by timing transits of Mercury across the surface during 2003 and 2006. The result was a measured radius of 696,342 ± 65 kilometres (432,687 ± 40 miles). [4]

Haberreiter, Schmutz & Kosovichev (2008) [1] determined the radius corresponding to the solar photosphere to be 695,660 ± 140 kilometres (432,263 ± 87 miles). This new value is consistent with helioseismic estimates; the same study showed that previous estimates using inflection point methods had been overestimated by approximately 300 km (190 mi).

Nominal solar radius

In 2015, the International Astronomical Union passed Resolution B3, which defined a set of nominal conversion constants for stellar and planetary astronomy. Resolution B3 defined the nominal solar radius (symbol ) to be equal to exactly695700 km. [5] The nominal value, which is the rounded value, within the uncertainty, given by Haberreiter, Schmutz & Kosovichev (2008), was adopted to help astronomers avoid confusion when quoting stellar radii in units of the Sun's radius, even when future observations will likely refine the Sun's actual photospheric radius (which is currently [6] only known to about an accuracy of ±100–200 km).

Examples

Solar radii as a unit are common when describing spacecraft moving close to the sun. Two spacecraft in the 2010s include:

Radius of another objects relative to the Sun's radius
NameRadius (Solar radius)Radius (kilometers)
WOH G64 (largest known star)1540 [7] 1,071,378,000
UY Scuti 909632,400,000
Betelgeuse 764 [8] 531,500,000
Antares A680 [9] 473,076,000
Rigel A78.9 [10] 54,980,000
Aldebaran 45.1 [11] 31,375,000
Arcturus 25.4 [12] 17,670,000
Pollux 9.06 [13] 6,300,000
Sirius A1.711 [14] 1,190,350
Sun 1695,700
Proxima Centauri 0.1542 [15] 107,275
Jupiter 0.102871,492 [16]
Saturn 0.086660,268 [16]
Uranus 0.0367325,559 [16]
Neptune 0.0355924,764 [16]
Earth 0.0091686,378 [16]
Venus 0.008696,051.8 [16]
Mars 0.004883,396.19 [16]
Mercury 0.00352,440.53 [16]
Moon 0.00251,738.1 [17]
Pluto 0.00171,188.3 [16]

See also

Related Research Articles

<span class="mw-page-title-main">70 Virginis</span> Star in the constellation Virgo

70 Virginis is a binary star located 59 light years from the Sun in the equatorial constellation of Virgo, near the northern constellation border with Coma Berenices. 70 Virginis is its Flamsteed designation. The star is visible to the naked eye as a faint, yellow-hued point of light with an apparent visual magnitude of +4.97. It is drifting further away with a heliocentric radial velocity of +4.4 km/s and has a high proper motion, traversing the celestial sphere at the rate of 0.621 arc seconds per annum.

HD 63454, formally named Ceibo, is a star located in the southern circumpolar constellation Chamaeleon near the border with Mensa. To see the star, one needs a small telescope because it has an apparent magnitude of 9.36, which is below the limit for naked eye visibility. The object is located relatively close at a distance of 123 light years based on Gaia DR3 parallax measurements but is receding with a heliocentric radial velocity of 33.8 km/s. At its current distance, HD 63454's brightness is diminished by two tenths of a magnitude due to interstellar dust. It has an absolute magnitude of +6.68.

<span class="mw-page-title-main">Groombridge 34</span> Binary star system in the constellation of Andromeda

Groombridge 34 is a binary star system in the northern constellation of Andromeda. It was listed as entry number 34 in A Catalogue of Circumpolar Stars, published posthumously in 1838 by British astronomer Stephen Groombridge. Based upon parallax measurements taken by the Gaia spacecraft, the system is located about 11.6 light-years from the Sun. This positions the pair among the nearest stars to the Solar System.

<span class="mw-page-title-main">Zeta Tucanae</span> Star in the constellation Tucana

Zeta Tucanae, Latinized from ζ Tucanae, is a star in the constellation Tucana. It is a spectral class F9.5 main sequence star with an apparent magnitude of +4.23. Despite having a slightly lower mass, this star is more luminous than the Sun. Based upon parallax measurements by the Hipparcos spacecraft, it is approximately 28.0 light years from Earth. This is one of the least variable stars observed during the Hipparcos mission.

20 Leonis Minoris is a binary star system in the northern constellation of Leo Minor. It is faintly visible to the naked eye, having an apparent visual magnitude of +5.4. Based upon an annual parallax shift of 66.46 mas, it is located 49 light years from the Sun. The star has a relatively high proper motion and is moving away from the Sun with a radial velocity of +56 km/s. The system made its closest approach about 150,000 years ago when it came within 32.2 ly (9.86 pc).

<span class="mw-page-title-main">HD 100546</span> Star in the constellation Musca

HD 100546, also known as KR Muscae, is a pre-main sequence star of spectral type B8 to A0 located 353 light-years from Earth in the southern constellation of Musca. The star is surrounded by a circumstellar disk from a distance of 0.2 to 4 AU, and again from 13 AU out to a few hundred AU, with evidence for a protoplanet forming at a distance of around 47 AU.

36 Ursae Majoris is a double star in the northern constellation of Ursa Major. With an apparent visual magnitude of 4.8, it can be seen with the naked eye in suitable dark skies. Based upon parallax measurements, this binary lies at a distance of 42 light-years from Earth.

HD 165259, also known as HR 6751 is a triple star system located in the southern circumpolar constellation of Apus. It has an apparent magnitude of 5.86, making it faintly visible to the naked eye Parallax measurements place the system at a distance of 138 light years, and it is currently receding with a heliocentric radial velocity of 13.1 km/s.

<span class="mw-page-title-main">HD 114613</span> Star in the constellation Centaurus

HD 114613 is a fifth magnitude yellow subgiant that lies 66.7 light-years away in the constellation of Centaurus. The star may be host to a long-period giant planet.

Xi Pegasi is the Bayer designation for a double star in the northern constellation of Pegasus, the winged horse. Located in the horse's neck, the primary component is an F-type main sequence star that is visible to the naked eye with an apparent visual magnitude of 4.2. It is 86% larger and 17% more massive that the Sun, radiating 4.5 times the solar luminosity. Based upon parallax measurements taken with the Hipparcos spacecraft, it is located 53.2 ± 0.2 light years from the Sun.

Gliese 221, also known as BD-06 1339, is a star with an exoplanetary companion in the equatorial constellation of Orion. It is too faint to be visible to the naked eye, having an apparent visual magnitude of 9.70 and an absolute magnitude of 8.15. Using parallax measurements, the distance to this system can be estimated as 66.2 light-years. It is receding from the Sun with a radial velocity of +23 km/s. This is a high proper motion star, traversing the celestial sphere at an angular rate of 0.333″·yr−1.

HD 168009 is a star in the northern constellation of Lyra. It has an apparent visual magnitude of 6.3, placing it just above to below the normal limit of stars visible to the naked eye under good viewing conditions of 6-6.5. An annual parallax shift of 42.93 mas provides a distance estimate of 76 light years. It is moving closer to the Sun with a heliocentric radial velocity of −65 km/s. In about 328,000 years from now, the star will make its closest approach at a distance of around 17 ly (5.1 pc).

<span class="mw-page-title-main">HD 111395</span> Star in the constellation Coma Berenices

HD 111395 is a single, variable star in the northern constellation of Coma Berenices. It has the variable star designation LW Com, short for LW Comae Berenices; HD 111395 is the Henry Draper Catalogue designation. The star has a yellow hue and is just bright enough to be barely visible to the naked eye with an apparent visual magnitude that fluctuates around 6.29. Based upon parallax measurements, it is located at a distance of 55.8 light years from the Sun. The star is drifting closer with a radial velocity of −8.9 km/s. It is a member of the Eta Chamaeleontis stellar kinematic group.

HD 46588 is a star in the northern circumpolar constellation Camelopardalis. It has an apparent magnitude of 5.44, allowing it to be faintly seen with the naked eye. The object is relatively close at a distance of only 59 light years but is receding with a heliocentric radial velocity of 15 km/s.

<span class="mw-page-title-main">19 Leonis Minoris</span> Spectroscopic binary in the constellation Leo Minor

19 Leonis Minoris is a spectroscopic binary located in the northern constellation Leo Minor. It has an apparent magnitude of 5.1, making it one of the brighter members of the constellation. The system is relatively close at a distance of 94 light years but is drifitng closer with a heliocentric radial velocity of 8.6 km/s.

References

  1. 1 2 Haberreiter, M; Schmutz, W; Kosovichev, A.G. (2008), "Solving the Discrepancy between the Seismic and Photospheric Solar Radius", Astrophysical Journal, 675 (1): L53–L56, arXiv: 0711.2392 , Bibcode:2008ApJ...675L..53H, doi:10.1086/529492, S2CID   14584860
  2. ↑ "NASA RHESSI oblateness measurements 2012". Archived from the original on 2018-09-17. Retrieved 2017-07-12.
  3. ↑ Ribas, Ignasi (August 2009). "The Sun and Stars as the Primary Energy Input in Planetary Atmospheres" (PDF). Proceedings of the International Astronomical Union. 5 (S264 [Solar and Stellar Variability: Impact on Earth and Planets]): 3–18. arXiv: 0911.4872 . Bibcode:2010IAUS..264....3R. doi:10.1017/S1743921309992298. S2CID   119107400.
  4. ↑ Emilio, Marcelo; Kuhn, Jeff R.; Bush, Rock I.; Scholl, Isabelle F. (2012), "Measuring the Solar Radius from Space during the 2003 and 2006 Mercury Transits", The Astrophysical Journal, 750 (2): 135, arXiv: 1203.4898 , Bibcode:2012ApJ...750..135E, doi:10.1088/0004-637X/750/2/135, S2CID   119255559
  5. ↑ Mamajek, E.E.; Prsa, A.; Torres, G.; et, al. (2015), IAU 2015 Resolution B3 on Recommended Nominal Conversion Constants for Selected Solar and Planetary Properties, arXiv: 1510.07674 , Bibcode:2015arXiv151007674M
  6. ↑ Meftah, M; Corbard, T; Hauchecorne, A.; Morand, F.; Ikhlef, R.; Chauvineau, B.; Renaud, C.; Sarkissian, A.; Damé, L. (2018), "Solar radius determined from PICARD/SODISM observationsand extremely weak wavelength dependence in the visibleand the near-infrared", Astronomy & Astrophysics, 616: A64, Bibcode:2018A&A...616A..64M, doi: 10.1051/0004-6361/201732159
  7. ↑ Levesque, Emily M.; Massey, Philip; Plez, Bertrand; Olsen, Knut A. G. (2009-06-01). "The Physical Properties of the Red Supergiant WOH G64: The Largest Star Known?". The Astronomical Journal. 137 (6): 4744–4752. arXiv: 0903.2260 . Bibcode:2009AJ....137.4744L. doi:10.1088/0004-6256/137/6/4744. ISSN   0004-6256.
  8. ↑ Joyce, Meridith; Leung, Shing-Chi; Molnár, László; Ireland, Michael; Kobayashi, Chiaki; Nomoto, Ken'ichi (2020-10-01). "Standing on the Shoulders of Giants: New Mass and Distance Estimates for Betelgeuse through Combined Evolutionary, Asteroseismic, and Hydrodynamic Simulations with MESA". The Astrophysical Journal. 902 (1): 63. arXiv: 2006.09837 . Bibcode:2020ApJ...902...63J. doi: 10.3847/1538-4357/abb8db . ISSN   0004-637X.
  9. ↑ Ohnaka, K.; Hofmann, K. -H.; Schertl, D.; Weigelt, G.; Baffa, C.; Chelli, A.; Petrov, R.; Robbe-Dubois, S. (2013-07-01). "High spectral resolution imaging of the dynamical atmosphere of the red supergiant Antares in the CO first overtone lines with VLTI/AMBER". Astronomy and Astrophysics. 555: A24. arXiv: 1304.4800 . Bibcode:2013A&A...555A..24O. doi:10.1051/0004-6361/201321063. ISSN   0004-6361.
  10. ↑ Moravveji, Ehsan; Guinan, Edward F.; Shultz, Matt; Williamson, Michael H.; Moya, Andres (2012-03-01). "Asteroseismology of the nearby SN-II Progenitor: Rigel. I. The MOST High-precision Photometry and Radial Velocity Monitoring". The Astrophysical Journal. 747 (2): 108. arXiv: 1201.0843 . Bibcode:2012ApJ...747..108M. doi:10.1088/0004-637X/747/2/108. ISSN   0004-637X. S2CID   425831.
  11. ↑ Hatzes, A. P.; Cochran, W. D.; Endl, M.; Guenther, E. W.; MacQueen, P.; Hartmann, M.; Zechmeister, M.; Han, I.; Lee, B. -C.; Walker, G. A. H.; Yang, S.; Larson, A. M.; Kim, K. -M.; Mkrtichian, D. E.; Döllinger, M. (2015-08-01). "Long-lived, long-period radial velocity variations in Aldebaran: A planetary companion and stellar activity". Astronomy and Astrophysics. 580: A31. arXiv: 1505.03454 . Bibcode:2015A&A...580A..31H. doi:10.1051/0004-6361/201425519. ISSN   0004-6361.
  12. ↑ Ramírez, I.; Allende Prieto, C. (2011-12-01). "Fundamental Parameters and Chemical Composition of Arcturus". The Astrophysical Journal. 743 (2): 135. arXiv: 1109.4425 . Bibcode:2011ApJ...743..135R. doi:10.1088/0004-637X/743/2/135. ISSN   0004-637X.
  13. ↑ Baines, Ellyn K.; Armstrong, J. Thomas; Schmitt, Henrique R.; Zavala, R. T.; Benson, James A.; Hutter, Donald J.; Tycner, Christopher; Belle, Gerard T. van (2017-12-21). "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer". The Astronomical Journal. 155 (1): 30. arXiv: 1712.08109 . doi: 10.3847/1538-3881/aa9d8b . ISSN   0004-6256.
  14. ↑ Liebert, James; Young, Patrick A.; Arnett, David; Holberg, J. B.; Williams, Kurtis A. (2005-09-01). "The Age and Progenitor Mass of Sirius B". The Astrophysical Journal. 630 (1): L69–L72. arXiv: astro-ph/0507523 . Bibcode:2005ApJ...630L..69L. doi:10.1086/462419. ISSN   0004-637X.
  15. ↑ Kervella, P.; Thévenin, F.; Lovis, C. (February 2017). "Proxima's orbit around Alpha Centauri". Astronomy & Astrophysics. 598: L7. arXiv: 1611.03495 . Bibcode:2017A&A...598L...7K. doi:10.1051/0004-6361/201629930. ISSN   0004-6361.
  16. 1 2 3 4 5 6 7 8 9 "Planetary Physical Parameters". Jet Propulsion Laboratory. Retrieved January 24, 2024.
  17. ↑ "Moon Fact Sheet". nssdc.gsfc.nasa.gov. Retrieved January 24, 2024.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.