949 Hel

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949 Hel (prov. designation: Template:Mp or Template:Mp) is a dark background asteroid from the outer regions of the asteroid belt, approximately Script error: No such module "convert". in diameter. It was discovered by German astronomer Max Wolf at the Heidelberg Observatory on 11 March 1921.[1] The transitional X-type asteroid has a rotation period of 8.2 hours. It was named in memory of the discoverer, after the Norse goddess of the dead, Hel.[2]

Orbit and classification

Hel is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[3][4] It orbits the Sun in the outer asteroid belt at a distance of 2.4–3.6 AU once every 5 years and 2 months (1,901 days; semi-major axis of 3 AU). Its orbit has an eccentricity of 0.19 and an inclination of 11° with respect to the ecliptic.[5] The body's observation arc begins at Lowell Observatory on 11 January 1931, almost a decade after its official discovery observation at Heidelberg in March 1921.[1]

Naming

This minor planet was named from Norse mythology, after Hel, the goddess of the dead and the queen of the underworld. The asteroid's name was proposed by the widow of Max Wolf, who had died two years earlier (RI 1013Script error: No such module "Check for unknown parameters".).[2]

Physical characteristics

In the Tholen-like taxonomy of the Small Solar System Objects Spectroscopic Survey (S3OS2), Hel is an X-type asteroid, while in the SMASS-like taxonomy of the S3OS2, it is a Xk-subtype that transitions from the X-type to the uncommon K-type asteroids.[4][6]

Rotation period

In September 2016, a rotational lightcurve of Hel was obtained from photometric observations by Pedro Brines and colleges of the Spanish group of asteroid observers (OBAS). Lightcurve analysis gave a rotation period of Script error: No such module "val". hours with a brightness variation of Script error: No such module "val". magnitude (U=2+Script error: No such module "Check for unknown parameters".).[7] The result supersedes previous observations by French amateur astronomers Laurent Bernasconi and René Roy in December 2001 and February 2004, which gave two tentative periods of Script error: No such module "val". and Script error: No such module "val". hours with an amplitude of 0.12 and 0.14, respectively.[8][9]

Diameter, mass and albedo

According to the surveys carried out by the Japanese Akari satellite, the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), and the Infrared Astronomical Satellite IRAS, Hel measures Script error: No such module "val"., Script error: No such module "val". and Script error: No such module "val". kilometers in diameter, and its surface has a corresponding albedo of Script error: No such module "val"., Script error: No such module "val". and Script error: No such module "val"., respectively.[10][11][12] The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0445 and a diameter of 69.11 km based on an absolute magnitude of 9.8.[8]

Benoit Carry estimates a diameter of Script error: No such module "val". kilometers, along with a mass of Script error: No such module "val". and a density of Script error: No such module "val"..[13] Apart from the above mentioned Script error: No such module "val". kilometers, the WISE team has also published three more mean-diameters of Script error: No such module "val". and Script error: No such module "val". and Script error: No such module "val". with albedos of Script error: No such module "val"., Script error: No such module "val". and Script error: No such module "val"., respectively.[4][8]

An asteroid occultation on 27 October 2005, gave a best-fit ellipse dimension of 69.0 × 69.0 kilometers, while a second occultation event gave an ellipse of 61.0 km × 61.0 km on 3 February 2014, with the latter having a better quality rating.[4] These timed observations are taken when the asteroid passes in front of a distant star.[4]

References

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  1. ↑ a b Script error: No such module "citation/CS1".
  2. ↑ a b Script error: No such module "citation/CS1".
  3. ↑ Script error: No such module "citation/CS1".
  4. ↑ a b c d e Script error: No such module "citation/CS1".
  5. ↑ Script error: No such module "citation/CS1".
  6. ↑ Script error: No such module "Citation/CS1".
  7. ↑ Script error: No such module "Citation/CS1".
  8. ↑ a b c Script error: No such module "citation/CS1".
  9. ↑ Script error: No such module "citation/CS1".
  10. ↑ Script error: No such module "Citation/CS1". (online, AcuA catalog p. 153)
  11. ↑ Script error: No such module "Citation/CS1".
  12. ↑ Script error: No such module "Citation/CS1".
  13. ↑ Script error: No such module "Citation/CS1". See Table 1.

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External links

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