Astronomy:6 Hebe

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6 Hebe 24px (historical)
Discovery[1]
Discovered byKarl Ludwig Hencke
Discovery siteDriesen, Prussia
Discovery date1 July 1847
Designations
(6) Hebe
Pronunciation/ˈhiːbiː/[2]
Named afterHēbē
A847 NA; 1847 JB
Minor planet categoryMain belt
AdjectivesHebean /hiːˈbiːən/ (trad.)[3]
Orbital characteristics[1]
Epoch 13 September 2023
(JD 2453300.5)
Uncertainty parameter 0
|{{{apsis}}}|helion}}2.92 astronomical unit|AU (437 million km)
|{{{apsis}}}|helion}}1.93 AU (289 million km)
2.43 AU (364 million km)
Eccentricity0.2027
Orbital period3.78 yr (1379.85 d)
Average Orbital speed18.93 km/s
Mean anomaly144.0°
Inclination14.736°
Longitude of ascending node138.63°
|{{{apsis}}}|helion}}10 March 2022
239.59°
Earth MOID0.97 AU (145 million km)
Proper orbital elements[4]
Proper semi-major axis2.4252710 AU
Proper eccentricity0.1584864
Proper inclination14.3511092°
Proper mean motion95.303184 deg / yr
3.77742 yr
(1379.702 d)
Precession of perihelion31.568209 arcsec / yr
Precession of the ascending node−41.829042 arcsec / yr
Physical characteristics
Dimensions205 km × 185 km × 170 km[5][6]
Mean diameter195±3 km[7]
Flattening0.25[lower-alpha 1]
Mass(1.24±0.24)×1019 kg[7][lower-alpha 2]
(1.27±0.13)×1019 kg[lower-alpha 3][8]
Mean density3.18±0.64 g/cm3[7]
Equatorial surface gravity
~0.079–0.099 m/s2
Equatorial escape velocity
~0.127–0.135 km/s
(457–486 km/h)
Rotation period7.274 h[6]: 349 
Pole ecliptic latitude45°
Pole ecliptic longitude339°
Geometric albedo0.268[7][5]
Physics~170 K
max: ~269 K (−4°C)
S
Apparent magnitude7.5[9] to 11.50
Absolute magnitude (H)5.61[1]
Angular diameter0.26" to 0.065"


6 Hebe (/ˈhiːbiː/) is a large main-belt asteroid, containing around 0.5% of the mass of the belt. However, due to its apparently high bulk density (greater than that of the Moon), Hebe does not rank among the top twenty asteroids by volume. This high bulk density suggests an extremely solid body that has not been impacted by collisions, which is not typical of asteroids of its size – they tend to be loosely-bound rubble piles.

In brightness, Hebe is the fifth-brightest object in the asteroid belt after Vesta, Ceres, Iris, and Pallas. It has a mean opposition magnitude of +8.3, about equal to the mean brightness of Saturn's moon Titan,[10] and can reach +7.5 at an opposition near perihelion.

Hebe may be the parent body of the H chondrite meteorites, which account for about 40% of all meteorites striking Earth.

History

Hebe was discovered on 1 July 1847 by German astronomer Karl Ludwig Hencke in the town of Driesen, Brandenburg, Prussia (now Drezdenko, Poland).[1] It is the sixth asteroid discovered. It was the second and final asteroid discovery by Hencke, after 5 Astraea. The name Hebe, after the Greek goddess of youth, was proposed by Carl Friedrich Gauss at Hencke's request.[11] The first asteroids discovered had widely been considered planets by astronomers, but the rapid discoveries of several new asteroids in the late 1840s complicated the classification of asteroids.[12] In the years following its discovery, Hebe was variously labelled as a planet,[11] small planet, or asteroid.[13] Eventually, throughout the latter half of the 19th century, the terms "asteroid" and "minor planet" became favored,[12] although some astronomers continued referring to Hebe as a planet in this period.[14]

Gauss chose a wineglass as Hebe's astronomical symbol.[11][15] It was encoded in Unicode 17.0 as U+1CEC0 𜻀 (12px).[16][17] As asteroids and their symbols grew in number, the practicality of assigning unique astronomical symbols to each asteroid was questioned. In 1851, astronomer Johann Franz Encke proposed a simpler system of a number—denoting the order of discovery—inscribed in a circle. For Hebe, this would be ⑥.[12][18]: 80  This system was widely adopted by astronomers, though astronomers eventually switched to using parentheses enclosing the number—thus (6) Hebe[19] or 6 Hebe[1] in modern notation.[12]

On 5 March 1977, Hebe occulted the star γ Ceti A (Kaffaljidhma).[20]

Orbit

A vector orbital diagram
The orbit of 6 Hebe compared with the orbits of the inner planets and Jupiter

Hebe orbits the Sun with an average distance (or semi-major axis) of 2.426 astronomical units (AU),[1] placing it in the inner section of the main asteroid belt.[21]: 1282  Its distance to the Sun varies from 1.935 AU at perihelion to 2.917 AU at aphelion due to its moderately elliptical orbit, indicated by its orbital eccentricity of 0.202. It has an orbital period of 3.778 Earth years, following an orbit inclined by 14.74° with respect to the ecliptic plane.[1]

Hebe resides near but does not participate in several orbital resonances. It orbits close to the 3:1 mean-motion resonance (MMR) with Jupiter at approximately 2.50 AU.[21]: 1282  Asteroids caught in the 3:1 Jovian MMR have orbital periods one-third that of Jupiter's; their orbits are destabilized and they are eventually removed by encounters with the planets, creating the 3:1 Kirkwood gap.[22]: 101  Hebe is also located near the destabilizing ν6 (g=g6) secular resonance with Saturn, which at Hebe's average distance of 2.426 AU is located at 15–16° inclination.[21]: 1282 

Possible Hebe family

In the 1990s, Hebe was identified as a possible source for H chondrites and IIE iron meteorites.[21]: 1293 [23]: 3  Its location near the 3:1 Jovian MMR and the ν6 Saturnian secular resonance means that fragments created by impact events are easily destabilized into Earth-crossing orbits, where they could eventually impact Earth as meteorites.[24]: 288, 300  Indeed, the H chondritic surface compositions of two near-Earth objects—(4953) 1990 MU and 2007 LE—point towards Hebe as their parent body.[25]: 65 [26]: 436  Spectral observations of asteroids near the 3:1 Kirkwood gap in the early 2010s identified 695 Bella, 1166 Sakuntala, and 1607 Mavis as potential relatives of Hebe.[27]: 531–532 [28] However, they are located on the opposite side of the 3:1 Kirkwood gap, indicating that they jumped across the gap.[23]: 3–4  In 2020, a study led by Sherry K. Fieber-Beyer identified nine additional candidate members of the tentative Hebe family, with some located on Hebe's side of the 3:1 Kirkwood gap.[23]: 1 

Physical characteristics

Simulations (top) and direct images (bottom) of 6 Hebe[29]
Size comparison: the first 10 asteroids profiled against the Moon. Hebe is sixth from the left.

Hebe is a large asteroid, with a volume-equivalent spheroidal diameter of 193 ± 6 kilometres (119.9 ± 3.7 mi). Though Hebe's shape approximates an oblate spheroid, it hosts numerous extreme topographical features. Five large depressions have been identified on its surface, possibly representing deep impact craters.[30]: 4–6  The depressions range from around 50 km (31 mi) to over 100 km (62 mi) in size, with depths between 7 and 18 kilometres (4.3 and 11.2 mi).[30]: 6  Hebe additionally has a large, flattened face, giving it the appearance of a "lopped-off tooth". This large facet may represent a section of the asteroid that was blasted away into space by an ancient impact event.[23]: 9 

Based on Hebe's lightcurve, or variations in its observed brightness, it rotates in a prograde (counterclockwise) direction with a rotation period of 7.27 hours. Its north pole pointing towards ecliptic coordinates (β, λ) = (45°, 339°) with a 10° uncertainty.[6]: 349 

Spectrum and composition

Hebe is classified as an S-type asteroid[31]: 104  under the Tholen classification scheme.[32] Planetary scientist Michael James Gaffey further subdivided S-type asteroids into seven mineralogical subclasses,[33] categorizing Hebe as an S(IV)-type asteroid. Hebe's S(IV) classification indicates its surface is silicate (or stony) in composition and undifferentiated or partially differentiated.[21]: 1282 

See also

Notes

  1. ↑ Flattening derived from the maximum aspect ratio (c/a): f=1−ca, where (c/a) = 0.75±0.04.[7]
  2. ↑ Composite estimate.
  3. ↑ (6.40±0.67)×10−12 M☉

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 "JPL Small-Body Database: 6 Hebe". Jet Propulsion Laboratory. https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=6. Retrieved 2023-09-20. 
  2. ↑ Noah Webster (1884) A Practical Dictionary of the English Language
  3. ↑ Gabriel Nisbet (1733) Caledon's Tears
  4. ↑ "AstDyS-2 Hebe Synthetic Proper Orbital Elements". Department of Mathematics, University of Pisa, Italy. https://newton.spacedys.com/astdys/index.php?pc=1.1.6&n=6. 
  5. ↑ 5.0 5.1 Supplemental IRAS Minor Planet Survey
  6. ↑ 6.0 6.1 6.2 Torppa, Johanna; Kaasalainen, Mikko; Michałowski, Tadeusz; Kwiatkowski, Tomasz; Kryszczyńska, Agnieszka; Denchev, Peter; Kowalski, Richard (August 2003). "Shapes and rotational properties of thirty asteroids from photometric data". Icarus 164 (2): 346–383. doi:10.1016/S0019-1035(03)00146-5. Bibcode: 2003Icar..164..346T. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 Vernazza, P. (October 2021). "VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis". Astronomy & Astrophysics 654: A56. doi:10.1051/0004-6361/202141781. A56. Bibcode: 2021A&A...654A..56V. 
  8. ↑ Baer, James; Chesley, Steven R.; Matson, Robert D. (May 2011). "Astrometric masses of 26 asteroids and observations on asteroid porosity". The Astronomical Journal 141 (5): 143. doi:10.1088/0004-6256/141/5/143. Bibcode: 2011AJ....141..143B. 
  9. ↑ Donald H. Menzel; Jay M. Pasachoff (1983). A Field Guide to the Stars and Planets (2nd ed.). Boston, MA: Houghton Mifflin. pp. 391. ISBN 0-395-34835-8. https://archive.org/details/fieldguidetostar00menz_0/page/391. 
  10. ↑ The Brightest Asteroids
  11. ↑ 11.0 11.1 11.2 Wöchentliche Unterhaltungen für Dilettanten und Freunde der Astronomie, Geographie und Witterungskunde. 1847. p. 315. https://books.google.com/books?id=9AcFAAAAQAAJ&pg=PA315. 
  12. ↑ 12.0 12.1 12.2 12.3 Hilton, J. L. (16 November 2007). "When did asteroids become minor planets?". U.S. Naval Observatory. http://aa.usno.navy.mil/faq/docs/minorplanets.php. Retrieved 27 March 2025. 
  13. ↑ Gould, B. A., Jr. (July 1848). "On the Orbits of the Asteroids". American Journal of Science and Arts 6 (16). 
  14. ↑ Luther, R. (1889). "Berechnung der Planeten (II) Parthenope und (6) Hebe" (in German). Astronomische Nachrichten 122 (6): 107–114. doi:10.1002/asna.18891220603. Bibcode: 1889AN....122..107L. 
  15. ↑ Steger, Franz (1847) (in de). Ergänzungs-conversationslexikon. 3. p. 442. https://books.google.com/books?id=aZyhQWSEjhoC&pg=PA442. "Hofrath Gauß gab auf Hencke's Ansuchen diesem neuen Planetoiden den Namen Hebe mit dem Zeichen (ein Weinglas)." 
  16. ↑ Bala, Gavin Jared; Miller, Kirk (18 September 2023). "Unicode request for historical asteroid symbols". Unicode. https://www.unicode.org/L2/L2023/23207-historical-asteroids.pdf. 
  17. ↑ "Miscellaneous Symbols Supplement". The Unicode Consortium. 2025. https://www.unicode.org/charts/PDF/U1CEC0.pdf. 
  18. ↑ Gould, B. A. (January 1852). "On the symbolic notation of the asteroids". The Astronomical Journal 2: 80. doi:10.1086/100212. Bibcode: 1852AJ......2...80G. https://articles.adsabs.harvard.edu/pdf/1852AJ......2...80G. 
  19. ↑ "(6) Hebe = 1847 NA = 1947 JB". Minor Planet Center. https://minorplanetcenter.net/db_search/show_object?utf8=%E2%9C%93&object_id=Hebe. Retrieved 26 April 2025. 
  20. ↑ Dunham, David W.; Maley, Paul D. (December 1977). "Possible Observation of a Satellite of a Minor Planet". The Minor Planet Bulletin 5: 16–17. Bibcode: 1977MPBu....5...16D. 
  21. ↑ 21.0 21.1 21.2 21.3 21.4 Gaffey, Michael J.; Gilbert, Sarah L. (November 1998). "Asteroid 6 Hebe: The probable parent body of the H-type ordinary chondrites and the IIE iron meteorites". Meteoritics & Planetary Science 33 (6): 1281–1295. doi:10.1111/j.1945-5100.1998.tb01312.x. Bibcode: 1998M&PS...33.1281G. 
  22. ↑ Yoshikawa, Makoto (September 1990). "Motions of Asteroids at the Kirkwood Gaps". Icarus 87 (1): 78–102. doi:10.1016/0019-1035(90)90022-2. Bibcode: 1990Icar...87...78Y. 
  23. ↑ 23.0 23.1 23.2 23.3 Fieber-Beyer, Sherry K.; Gaffey, Michael J. (December 2020). "The Family of (6) Hebe". The Planetary Science Journal 1 (3): 68. doi:10.3847/PSJ/abc17a. 58. Bibcode: 2020PSJ.....1...68F. 
  24. ↑ Farinella, Paolo; Froeschle, Christiane; Gonczi, Robert (March 1993). "Meteorites from the Asteroid 6 Hebe". Celestial Mechanics and Dynamical Astronomy 56 (1–2): 287–305. doi:10.1007/BF00699740. Bibcode: 1993CeMDA..56..287F. 
  25. ↑ Kelley, Michael S.; Gaffey, Michael J.; Reddy, Vishnu; Sanchez, Juan A. (May 2014). "Surface composition of near-Earth Asteroid (4953) 1990 MU: Possible fragment of (6) Hebe". Icarus 233: 61–65. doi:10.1016/j.icarus.2014.01.015. Bibcode: 2014Icar..233...61K. 
  26. ↑ Fieber-Beyer, Sherry K.; Gaffey, Michael J.; Bottke, William F.; Hardersen, Paul S. (April 2015). "Potentially hazardous Asteroid 2007 LE: Compositional link to the black chondrite Rose City and Asteroid (6) Hebe". Icarus 250: 430–437. doi:10.1016/j.icarus.2014.12.021. Bibcode: 2015Icar..250..430F. 
  27. ↑ Fieber-Beyer, Sherry K.; Gaffey, Michael J.; Kelley, Michael S.; Reddy, Vishnu; Reynolds, Chalbeth M.; Hicks, Tony (June 2011). "The Maria asteroid family: Genetic relationships and a plausible source of mesosiderites near the 3:1 Kirkwood Gap". Icarus 213 (2): 524–537. doi:10.1016/j.icarus.2011.03.009. Bibcode: 2011Icar..213..524F. 
  28. ↑ Gaffey, M. J.; Fieber-Beyer, S. K. (September 2013). "Identification of a Possible H-Chondrite Asteroid Family". 76th Annual Meeting of the Meteoritical Society. Edmonton, Alberta, Canada. Bibcode: 2013M&PSA..76.5124G. 
  29. ↑ "Not the mother of meteorites". https://www.eso.org/public/images/potw1725a/. 
  30. ↑ 30.0 30.1 Marsset, M.; Carry, B.; Dumas, C.; Hanuš, J.; Viikinkoski, M.; Vernazza, P.; Müller, T. G.; Delbo, M. et al. (August 2017). "3D shape of asteroid (6) Hebe from VLT/SPHERE imaging: Implications for the origin of ordinary H chondrites". Astronomy & Astrophysics 604: A64. doi:10.1051/0004-6361/201731021. A64. Bibcode: 2017A&A...604A..64M. 
  31. ↑ Migliorini, F.; Manara, A.; Scaltriti, F.; Farinella, P.; Cellino, A.; Di Martino, M. (July 1997). "Surface Properties of (6) Hebe: A Possible Parent Body of Ordinary Chondrites". Icarus 128 (1): 104–113. doi:10.1006/icar.1997.5679. Bibcode: 1997Icar..128..104M. 
  32. ↑ DeMeo, F. E.; Alexander, C. M. O'D.; Walsh, K. J.; Chapman, C. R.; Binzel, R. P. (2015). "The Compositional Structure of the Asteroid Belt". Asteroids IV. University of Arizona Press, Tucson. pp. 13–41. doi:10.2458/azu_uapress_9780816532131-ch002. ISBN 978-0-816-53213-1. Bibcode: 2015aste.book...13D. https://www.mit.edu/~fdemeo/publications/DeMeoetal2015_AIV.pdf. 
  33. ↑ Gaffey, Michael J.; Bell, Jeffrey F.; Brown, R. Hamilton; Burbine, Thomas H.; Piatek, Jennifer L.; Reed, Kevin L.; Chaky, Damon A. (December 1993). "Mineralogic variations within the S-type asteroid class". Icarus 106 (2): 573–602. doi:10.1006/icar.1993.1194. Bibcode: 1993Icar..106..573G. 



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