3749 Balam

Orbit and classification

Balam is a member of the Flora family, a very large group of stony asteroids in the inner main-belt. It orbits the Sun in the inner main-belt at a distance of 2.0–2.5 AU once every 3 years and 4 months (1,222 days). Its orbit has an eccentricity of 0.11 and an inclination of 5° with respect to the ecliptic.

Naming

It is named after the Canadian astronomer David Balam, principal observer at Victoria's Climenhaga Observatory in British Columbia. The approved naming citation was published by the Minor Planet Center on 31 May 1988 (M.P.C. 13178).

Physical characteristics

The S-type asteroid has an albedo of 0.16. The body's rotation around its axis has been measured several times by different lightcurve observations with a concurring period of 2.8 hours.

Triple asteroid

Outer satellite

On 13 February 2002, the discovery of a minor-planet moon, provisionally designated , was announced by a team of researchers from SwRI, UA, JPL and OSUG, using the Gemini North Telescope on Mauna Kea in Hawaii. It has an estimated diameter of 1.84 kilometers. It orbits km away in days, with a high orbital eccentricity of ~ 0.9. The distant and highly eccentric orbit of S/2002 (3749) 1 suggests that it was likely captured by Balam.

Being such a small primary body in the inner main belt with a separation of over 100 primary radii, S/2002 (3749) 1 is the most loosely bound binary known. Balam has a Hill sphere with a radius of about 1,500 kilometers.

Inner satellite

In March 2008, Franck Marchis discovered another satellite from eclipses seen in Balam's light curve, making Balam a trinary asteroid. The inner satellite, which does not have a provisional designation, has a derived diameter of 1.66 kilometers, based on diameter-ratio of with its primary.

Other known trinary asteroids include 45 Eugenia, 87 Sylvia, 93 Minerva, 107 Camilla, 130 Elektra and 216 Kleopatra.

Asteroid pair

Balam forms an asteroid pair with . Asteroid pairs are on highly similar heliocentric orbits. At some point in the past, the pair of asteroids became gravitationally unbound due to rotational fission induced by the YORP-effect or from a collisional breakup of the parent body. After the discovery of Balam's two satellites by Bill Merline (inner moon) and Franck Marchis (outer moon) in 2002 and 2008, respectively, Czech physicist David Vokrouhlický identified the unbound secondary in 2009. Based on backward orbit integrations, it is thought that Balam and form a secured asteroid pair that became separated approximately 400,000 years ago.

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