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26074 Carlwirtz
26074 Carlwirtz (provisional designation 1977 TD) is a dynamical Hungaria asteroid and binary Mars-crosser from the innermost regions of the asteroid belt, approximately 3 kilometers (2 miles) in diameter. It was discovered on 8 October 1977, by German astronomer Hans-Emil Schuster at ESO's La Silla Observatory in northern Chile. The likely binary asteroid on a relatively circular orbit has a short rotation period of 2.5 hours.[3] It was named for German astronomer Carl Wilhelm Wirtz.[1] The system's suspected minor-planet moon of unknown size was first detected in 2013.[5] Orbit and classificationCarlwirtz is a member of the Mars-crossing asteroids, a dynamically unstable group between the main belt and the near-Earth populations, crossing the orbit of Mars at 1.66 AU.[1][6] It also belongs to the dynamical Hungaria group, which forms the innermost dense concentration of asteroids in the Solar System.[3] It is, however, not a member of the Hungaria family (003), but a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements.[6][7] It orbits the Sun in the innermost asteroid belt at a distance of 1.65–1.97 AU once every 2 years and 5 months (890 days; semi-major axis of 1.81 AU). Its orbit has an unusually low eccentricity of 0.09 and an inclination of 32° with respect to the ecliptic.[2] The body's observation arc begins at La Silla Observatory in October 1977, on the night following its official discovery observation.[1] NamingThis minor planet was named after Carl Wilhelm Wirtz (1875–1939), a German astronomer at Strasbourg and Kiel observatories. In 1924, he revealed statistically the redshift-distance relationship of spiral nebulae. The official naming citation was published by the Minor Planet Center on 28 September 2004 (M.P.C. 52769).[8] Physical characteristicsCarlwirtz is an assumed E-type asteroid,[3] but may as well be a common S-type asteroid, since the E-type is typical found among members of the Hungaria family rather than among the larger, encompassing dynamical group with the same name. Rotation periodIn June 2013, a rotational lightcurve of Carlwirtz was obtained from photometric observations by American photometrist Brian Warner at the Palmer Divide Station (U82) in California. Lightcurve analysis gave a well-defined rotation period of 2.5493±0.0003 hours with a brightness amplitude of 0.11±0.01 magnitude (U=3).[5][a] Follow-up observations by Warner in May 2018 gave a similar period 2.539±0.002 hours (U=2+).[3][b] SatelliteDuring the observations in June 2013, Warner also noted that Carlwirtz is likely a synchronous binary asteroid with a minor-planet moon in its orbit.[5][a] While the satellite dimension could not be determined, it has an orbital period of 16.11 hours with an estimated semi-major axis of 6.1 kilometers.[4] However, neither in 2013 nor in the 2018-observations any eclipsing/occultation events could be detected. Instead the asteroid has a classically shaped bimodal lightcurve instead. Since Carlwirtz has a period that is close to two thirds of an Earth-day, single-station observations have difficulties to track a complete lightcurve.[3][5][a][b] Diameter and albedoThe Collaborative Asteroid Lightcurve Link assumes an albedo of 0.30 – a compromise value between the S-type (0.20) and E-type (0.40) asteroids – and calculates a diameter of 2.54 kilometers based on an absolute magnitude of 14.9.[3][5] According to estimates by Johnston's archive, Carlwirtz measures 3.62 kilometers in diameter for an assumed albedo of 0.16. Notes
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