699 Hela

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699 Hela
699Hela (Lightcurve Inversion).png
Lightcurve-based 3D-model of Hela
Discovery [1]
Discovered by J. Helffrich
Discovery site Heidelberg
Discovery date5 June 1910
Designations
(699) Hela
Pronunciation /ˈhiːlə/ [2]
1902 WE ·1910 LC ·1923 TB ·1948 KD ·1957 WX1 [1] [a]
Mars crosser [3]
Orbital characteristics [3]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc 113.38 yr (41,411 d)
Aphelion 3.6831  AU (550.98  Gm)
Perihelion 1.5414 AU (230.59 Gm)
2.6123 AU (390.79 Gm)
Eccentricity 0.40995
4.22 yr (1,542.1 d)
3.93957°
0° 14m 0.384s / day
Inclination 15.297°
242.548°
91.479°
Earth  MOID 0.62609 AU (93.662 Gm)
Mars  MOID 0.4063 AU (60.78 Gm)
Jupiter  MOID 2.10581 AU (315.025 Gm)
TJupiter 3.239
Physical characteristics
Dimensions 12–27 km [7]
3.3962  h (0.14151  d) [3]
11.72 [3]

    699 Hela is a Mars crossing asteroid. It was discovered on 5 June 1910 at Heidelberg Observatory by German astronomer Joseph Helffrich, and may have been named after Hel, the Norse ruler of the underworld. [8] This asteroid is orbiting the Sun at a distance of 2.61 astronomical units (AU) with a period of 4.22 years and an eccentricity of 0.41. The orbital plane is inclined at an angle of 15.3° to the plane of the ecliptic. [3]

    Contents

    History and naming

    Hela was discovered on 5 June 1910 in photographs taken by German astronomer Joseph Helffrich on 5–6 June at Heidelberg Observatory. [9] It was reported in the journal Astronomische Nachrichten on 11 June under the old-style provisional designation 1910 KD. [4] The asteroid was later named Hela, possibly after the Norse goddess of the dead Hel, ruler of the underworld. [8] : 66 

    Subsequent observations of Hela were conducted by Johann Palisa in Vienna on 10 and 14 June and 2, 4, and 5 July. Helffrich and Palisa's observations were unfavorably distributed, preventing the calculation of Hela's orbit. Nevertheless, its high eccentricity was already noticed by astronomers. In 1911, astronomer Adolf Berberich identified the lost asteroid 1902 KQ with Hela; by that time, Hela had been assigned the number (699). [10] 1902 KQ was observed from Heidelberg Observatory on 21 November 1902, [5] making these observations the earliest precoveries of Hela identified. [1]

    In 1925, the style of minor planet provisional designations was changed from a rotating system from AA to ZZ to one tied to half-months and days of the month. This system is currently in use, and was retroactively extended to minor planets discovered before 1925. [11] Thus, Hela's designations for its official discovery and earliest precovery were changed from 1910 KD and 1902 KQ to 1910 LC and 1902 WE, respectively. [1]

    Orbit

    Hela orbits the Sun with an average distance, or semi-major axis, of 2.61 astronomical units (AU), taking 4.23 years to complete one orbit. Due to its high orbital eccentricity of 0.41, its distance from the Sun varies from 3.69 AU at aphelion to 1.54 AU at perihelion, crossing the orbit of Mars. It has an orbital inclination of 15.29° with respect to the ecliptic plane. [3]

    Physical characteristics

    With an absolute magnitude of 11.7, [3] the asteroid is about 12–27 km in diameter. [7] It is classified as a stony Sk [12] or Sq-type [3] asteroid in the SMASS taxonomy. Photometry data used to produce light curves provide a rotation period of 3.39624±0.00006 h. The lightcurve inversion method was used to build a shape model with a rounded form and an equatorial bulge. [13]

    Notes

    1. ↑ JPL's Small-Body Database (SBDB) Lookup notates Hela's retroactive new-style designations as A902 WE, A910 LC, and A923 TB. [3] Its old-style designations were 1902 KD, [4] 1902 KQ, [5] and 1923 OZ. [6]

    References

    1. 1 2 3 4 "(699) Hela = 1902 WE = 1910 LC = 1923 TB = 1948 KD = 1957 WX1". Minor Planet Center. Retrieved 1 November 2025.{{cite web}}: CS1 maint: url-status (link) (2393 obs)
    2. ↑ Noah Webster (1884) A Practical Dictionary of the English Language
    3. 1 2 3 4 5 6 7 8 9 "JPL Small-Body Database Browser: 699 Hela (A910 LC)". Jet Propulsion Laboratory . Retrieved 7 May 2016.
    4. 1 2 Wolf, M. (June 1910). "Photographische Aufnahmen von kleinen Planeten". Astronomische Nachrichten (in German). 185: 61. Bibcode:1910AN....185...61W. doi:10.1002/asna.19101850407.
    5. 1 2 Alberts, B. (January 1914). "Über den Planeten 699 Hela". Astronomische Nachrichten. 196: 421. Bibcode:1914AN....196..421A.
    6. ↑ "Notes on some Points connected with the Progress of Astronomy during the Past Year". Monthly Notices of the Royal Astronomical Society. 84 (4): 258–296. 8 February 1924. doi: 10.1093/mnras/84.4.258 .
    7. 1 2 "Absolute Magnitude (H)". NASA/JPL. Archived from the original on 2 March 2001. Retrieved 24 June 2014.
    8. 1 2 Schmadel, Lutz (2003), Dictionary of minor planet names, vol. 1, Springer, p. 68, ISBN   9783540002383.
    9. ↑ Brendel, M. (December 1911). "Der Planet 699 [1910 KD]". Astronomische Nachrichten (in German). 190: 137. Bibcode:1911AN....190..137B. doi:10.1002/asna.19111900805.
    10. ↑ Berberich, Adolf (1911). "Planet 699 [1910 KD]". Astronomische Nachrichten (in German). 190 (1): 12. Bibcode:1911AN....190...11B. doi:10.1002/asna.19111900106.
    11. ↑ "Provisional Designations". Minor Planets Center. Retrieved 5 November 2025.
    12. ↑ Angeli, C. A.; Lazzaro, D. (August 2002), "Spectral properties of Mars-crossers and near-Earth objects. Results of the S3OS2 survey", Astronomy and Astrophysics, 391: 757–765, Bibcode:2002A&A...391..757A, doi: 10.1051/0004-6361:20020834 .
    13. ↑ Alonso, E. Díez; et al. (April 2021), "Asteroids 4092 Tyr (Follow Up, Analysis, Preliminary Results) and 699 Hela (Spin-Shape Model)", Bulletin of the Minor Planets Section of the Association of Lunar and Planetary Observers, 48 (2): 136–139, Bibcode:2021MPBu...48..136A.
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