1627 Ivar
1627 Ivar is an elongated stony asteroid and near-Earth object of the Amor group, approximately 15×6×6 km. It was discovered on 25 September 1929, by Danish astronomer Ejnar Hertzsprung at Leiden Southern Station, annex to the Johannesburg Observatory in South Africa. It was named after Ivar Hertzsprung, brother of the discoverer. 1627 Ivar was the first asteroid to be imaged by radar, in July 1985 by the Arecibo Observatory.
Classification and orbit
Ivar orbits the Sun at a distance of 1.1–2.6 AU once every 2 years and 6 months. Its orbit has an eccentricity of 0.40 and an inclination of 8° with respect to the ecliptic. Ivar's observation arc begins with its official discovery observation in 1929, as no precoveries were taken, and no prior identifications were made.It has an Earth minimum orbit intersection distance of which corresponds to 43.5 lunar distances. The eccentric Amor asteroid is also a Mars-crosser. In August 2074, it will pass Earth at 0.141 AU, closer than it actually approached Mars in July 1975.
Physical characteristics
In the SMASS and Tholen taxonomic scheme, Ivar is characterized as a common stony S-type asteroid.Rotation period
A large number of rotational lightcurves of Ivar have been obtained from photometric observations since 1985 '. They give a well-defined rotation period between 4.795 and 4.80 hours with a brightness variation between 0.27 and 1.40 magnitude, indicative of its non-spheroidal shape '. New radar and visual observations refined the period to 4.7951689 ± 0.0000026 hours. Future photometric observations will show whether the YORP effect will slowly change the body's spin rate.In 1985, the body was observed with radar from the Arecibo Observatory in Puerto Rico at a distance of 0.20 AU. The measured radar cross-section was 7.5 square kilometers. It was the first asteroid to be imaged by radar. Radar observations have been performed again in June & July 2013 and July 2018.