Asteroids

Asteroids (Greek for "star-like") come in all shapes and sizes from the largest known asteroid at 587 miles across, the larger bodies are called minor planets (SEE also: Dwarf Planets Pluto, Ceres, Eris, Makemake and Haumea etc)

Asteroids have a diameter greater than one meter anything smaller is a meteoroid.

The majority of asteroids fall into three main groups: Carbon based C-type, Nickel / Iron based M-type, and Stony S-type.

Pallas is the second largest asteroid, 326 miles (524 km)in diameter, located in the Asteroid belt .

Binaries

Around 15 percent of all known asteroids larger than 650 feet (200 meters) in diameter are binary pairs(double asteroid), two gravitationally bound objects in orbit around each other travel through space together.

The vast majority of binaries involve an unequal pair, in which one asteroid is significantly larger than the other. An exceptionally rare phenomenon is that of a “equal mass” binary, in which the two objects are roughly the same mass.

Trojan Asteroids

Trojan Asteroids are found at L4 and L5 (lagrange points) that are in the same orbit as that of a planet.

The Earth is only known to have one Trojan Asteroid called 2010 TK7 around L4.

There are at least 5,000 Trojan asteroids in the Lagrangian points around Jupiter.

Apollo Asteroids

Apollo asteroids are Near Earth Asteroids (NEAs) with perihelion distances less than 1.017 AU, and semi-major axis greater than 1 AU. They have sizes less than 10 km (1866 Sisyphus is the largest discovered so far) and form the majority of the population of Earth-crossing and Potentially Hazardous asteroids.

Visited Asteroids

Asteroids that have been visited by robotic spacecraft (All USA flybys probes unless stated, listed by year of arrival at asteroid)

    • '951 Gaspra' by ESA Galileo in 1991

    • '243 Ida' by ESA Galileo in 1993

    • '253 Mathilde' by 'NEAR Shoemaker' in 1997

    • '433 Eros' by 'NEAR Shoemaker' Lander in 1998-2001

    • '9969 Braille' by Deep Space 1 in 1999

    • '5535 Annefrank' by Stardust in 2002

    • '25143 Itokawa' by Japan Hayabusa Lander/Sample and return in 2005

    • '2867 Šteins' by ESA Rosetta in 2008

    • '21 Lutetia' by ESA Rosetta in 2010

    • '4179 Toutatis' by China Chang'e 2 in 2012

    • Ryugu by Japan's Hayabusa2 probe with 3 rovers and a lander 2018

Upcoming:

    • '101955 Bennu' by OSIRIS-REx 2018 sample collection and return

    • '(486958) 2014 MU69' by 'New Horizons' on the 1st Jan 2019

Comets versus Asteroids

Naming of Asteroids

Why I Have a Real Planet Named After Me - (33434) Scottmanley