Discovery of the Hungaria asteroid 2005 YV53

La Caņada Observatory, Juan Lacruz, Dec 2005


I found this asteroid at mag 20.5R in stacked CCD frames taken at La Caņada on 2005 Dec the 24th, soon after detection I noticed the fast movement about 0.7"/min in a quite inclined path so I fed the astrometry to Bill Gray's FindOrb(1) to try and find a preliminary orbit. Unlike other discoveries it didn't seem to fit to a main belt asteroid typical orbit and it didn't converge as usual. I continued shooting images, a total of 355 images of 30 sec each totalling about 3 hours exposure were obtained on a cold and very clear night,  once stacked and solved in astrometrica, I sent the astrometry to the minor planet center (mpc) noting the special object's movement.

The next day I checked the astrometry with the mpc checker service, I requested all known objects up to mag 21 in an area of 3 degrees radius centered on the observations, all the bodies returned by the checker had quite different movements, both in speed and position angle, to that of the object and thus it seemed very likely new and special, if it were a common main belter its movement should have been similar to most of the rest of bodies returned by the checker.

On 2005 Dec the 29th I got an automated email from the mpc with the temporary designation 2005 YV53 credited to J87 La Caņada, the object though didn't have a published orbit, just a Väisälä aproximation based on the very short arc, however the predicted movement looked like that of a Hungaria asteroid. 

As known from the theory of orbit determination (2) (Gauss, 1809; Danby,1989), when three observations are used to compute a preliminary orbit, the curvature of the arc appears as a divisor in the orbit solution of Gauss' method. The smaller is the curvature, the less accurate is the orbit; since Hungarias have almost circular orbits the uncertainty in preliminary calculations is usually big, these bodies can be taken by NEOs until a longer observational arc is acquired.

The Hungaria asteroids (3), have a mean semimajor axis of 1.91 AU; thus, their orbital periods are less than one-fourth that of Jupiter, i.e. between resonances 1:4 and 1:5. Hungarias have nearly circular orbits (the mean eccentricity is 0.08) and moderately large inclinations, the mean inclination being 22.7°. At least one dynamical family (Hirayama family), the Hungaria family, exists within the Hungaria group. Because of the low eccentricities of their orbits, the mean perihelion distance of a Hungaria asteroid is 1.76 AU. Accordingly, a typical Hungaria cannot pass close to Mars, whose aphelion distance is 1.67 AU. A few Hungarias, however, have perihelion distances a few hundredths of 1 AU less than Mars's aphelion distance and so are shallow "Mars crossers" as well.

Hungaria asteroids are mainly E-type thought to be made of enstatite (magnesium silicate) and have very high albedos, some Hungarias might have been perturbed into apollo type orbits.

See a plot  (4) with the distribution of the different asteroid groups, Hungarias are shown in light blue colour inside the innermost regions of the main belt.


Bibliography :


(2) Orbit Determination with Very Short Arcs,

Andrea Milani, Giovanni F. Gronchi, Mattia de' Michieli Vitturi

Department of Mathematics, University of Pisa, via Buonarroti 2, 56127 Pisa, Italy

and Zoran Knezevic

Astronomical Observatory, Volgina 7, 11160 Belgrade 74, Serbia and Montenegro

(3) Project Pluto, Bill Gray,

(4) Asteroid and comet groups, Petr Scheirich, 2005,

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