Astronomical Unit in the context of List of Earth-crossing asteroids

A Mars-crossing asteroid (MCA, also Mars-crosser, MC) is an asteroid whose orbit crosses that of Mars. Some Mars-crossers numbered below 100000 are listed here. They include the two numbered Mars trojans 5261 Eureka and (101429) 1998 VF31.

Many databases, for instance the JPL Small-Body Database (JPL SBDB), only list asteroids with a perihelion greater than 1.3 AU as Mars-crossers. An asteroid with a perihelion less than this is classed as a near-Earth object even though it is crossing the orbit of Mars as well as crossing (or coming near to) that of Earth. Nevertheless, these objects are listed on this page. A grazer is an object with a perihelion below the aphelion of Mars (1.67 AU) but above the Martian perihelion (1.38 AU). The JPL SBDB lists 13,500 Mars-crossing asteroids. Only 18 MCAs are brighter than absolute magnitude (H) 12.5, which typically makes these asteroids with H<12.5 more than 13 km in diameter depending on the albedo. The smallest known MCAs have an absolute magnitude (H) of around 24 and are typically less than 100 meters in diameter. There are over 21,600 known Mars-crossers of which only 5751 have received a MPC number.

Beta Crateris, Latinized from β Crateris, is a binary star system in the southern constellation of Crater. It is visible to the naked eye with an apparent visual magnitude of 4.46. Based upon an annual parallax shift of 9.59 mas as seen from Earth, it is around 340 light years from the Sun.

This is an astrometric binary star system with an orbital period of 6.0 years and a projected separation of 8.3 AU. The orbit has an estimated semimajor axis of 9.3 AU. The primary component A is listed as an A-type giant star with a stellar classification of A2 III. However, Houk and Smith-Moore (1988) give a main sequence classification of A1 V, while Abt and Morrell (1995) list it as a subgiant star with a class of A2 IV. The spectrum shows enhanced barium, possibly as a result of a previous mass transfer event.

The Themis family (adj. Themistian; FIN: 602) is a family of carbonaceous asteroids located in the outer portion of the asteroid belt, at a mean distance of 3.13 AU from the Sun. It is one of the largest families with over 4700 known members, and consists of a well-defined core of larger bodies surrounded by a region of smaller ones. The collisional Themis family is named after its parent body, the asteroid 24 Themis, discovered on 5 April 1853 by Italian astronomer Annibale de Gasparis.

HR 4796 is a binary star system in the southern constellation of Centaurus. Parallax measurements put it at a distance of 235 light-years (72 parsecs) from the Earth. The two components of this system have an angular separation of 7.7 arcseconds, which, at their estimated distance, is equivalent to a projected separation of about 560 Astronomical Units (AU), or 560 times the separation of the Earth from the Sun. The star and its ring resemble an eye, and it is sometimes known by the nickname "Sauron's Eye".