Medusa (minor planet designation: 149 Medusa) is a bright-coloured, stony main-belt asteroid that was discovered by French astronomer J. Perrotin on September 21, 1875, and named after the Gorgon Medusa, a snake-haired monster in Greek mythology. It is orbiting the Sun at a distance of 2.17 AU with a period of 3.21 years and an eccentricity of 0.065. The orbital plane is tilted slightly at an angle of 0.94° to the plane of the ecliptic.[3]

149 Medusa
149Medusa (Lightcurve Inversion).png
A three-dimensional model of 149 Medusa based on its light curve.
Discovered byHenri Joseph Perrotin
Discovery date21 September 1875
(149) Medusa
Named after
A875 SA; 1905 BA;
1906 HB
Main belt
Orbital characteristics[3][4]
Epoch 31 July 2016 (JD 2457600.5)
Uncertainty parameter 0
Observation arc124.55 yr (45493 d)
Aphelion2.32 AU (346.60 Gm)
Perihelion2.03 AU (304.06 Gm)
2.17 AU (325.33 Gm)
3.21 yr (1,171.4 d)
20.18 km/s
0° 18m 26.374s / day
Earth MOID1.04 AU (155.77 Gm)
Jupiter MOID2.88 AU (430.38 Gm)
Physical characteristics
Dimensions19.75±0.9 km
Mass8.0×1015 kg
Mean density
2.0 g/cm3
Equatorial surface gravity
0.0055 m/s2
Equatorial escape velocity
0.0104 km/s
26.023 h (1.0843 d)[4]
26.038 h[5]
Temperature~189 K

When it was discovered, Medusa was by far the smallest asteroid found (although this was not known at that time). Since then, many thousands of smaller asteroids have been found. It was also the closest asteroid to the Sun discovered up to that point, beating the long-held record of 8 Flora. It remained the closest asteroid to the Sun until 433 Eros and 434 Hungaria were found in 1898, leading to the discovery of two new families of asteroids inward from the 4:1 Kirkwood gap which forms the boundary of the main belt.[citation needed]

Photometric observations of this asteroid at the Organ Mesa Observatory in Las Cruces, New Mexico, during 2010 gave a light curve with a rather long rotation period of 26.038 ± 0.002 hours and a brightness variation of 0.56 ± 0.03 in magnitude.[5]


  1. ^ "Discovery Circumstances: Numbered Minor Planets (1)-(5000)". IAU-Minor Planet Center. Retrieved 22 August 2016.
  2. ^ "Medusa". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  3. ^ a b "The Asteroid Orbital Elements Database". astorb. Lowell Observatory.
  4. ^ a b Yeomans, Donald K., "149 Medusa", JPL Small-Body Database Browser, NASA Jet Propulsion Laboratory, retrieved 12 May 2016.
  5. ^ a b Pilcher, Frederick (April 2011), "Rotation Period Determinations for 25 Phocaea, 140 Siwa, 149 Medusa 186 Celuta, 475 Ocllo, 574 Reginhild, and 603 Timandra", The Minor Planet Bulletin, vol. 38, no. 2, pp. 76–78, Bibcode:2011MPBu...38...76P.

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