Darmstadtium (Element 110) discovered/created 1994

Darmstadtium was first created November 9, 1994 at the Institute for Heavy Ion Research in Darmstadt, Germany.  Researches bombarded a lead (Pb-208) target with nickel (Ni-62) and created a single atom of the isotope darmstatdium-269. Using heavier isotopes of nickel, they created 9 atoms of Ds-271, confirmed by its decay and the daughter elements.

So far, 10 isotopes of darmstadtium have been reported, with Ds-281 being the most stable, with a half-life of about 12.7 seconds.  Due to such a short life span, chemical characteristics have not been determined.  However, Ds is extremely radioactive.  It is named after the city Darmstadt, where it was discovered.

Iapetus, moon of Saturn, discovered 1671

Iapetus, the third largest moon of Saturn, was discovered by Giovanni Cassini, October 25, 1671.  It is unique for several reasons.  First, it has a dark region, known as Cassini Regio, which is contrasted with the brightness from ice on the rest of the moon.  Ice covers most of the moon.

Second, Iapetus has an inclined orbit, more than any of the regular, i.e. largest, moons.  The rings of Saturn would be clearly visible because of its inclined orbit.  

Third, it has an equatorial ridge that runs through the center of  Cassini Regio.  Mountains in this ridge rise over 12 miles of the surrounding plains, making them among the tallest mountains in the solar system.  Mons Olympus on Mars is the tallest in the solar system. 

The source of the dark material and why the equatorial ridge exists only in Cassini Regio are unknown.

The spacecraft Cassini passed by at a range of 1,227 km (762 miles) on September 10, 2007. 

Chiron, minor planet, discovered 1977

Chiron, a minor planet between Saturn and Uranus, was discovered November 1, 1977, by Charles Kowal.  It was the first of a class of objects known as centaurs, astral bodies orbiting between the asteroid belt and the Kuiper Belt.  

It also has a classification as a comet, 95P/Chiron.

It has a radius of about 107.8 + 5km and rotates about every 6 hours.  It orbits the sun about every 50.5 years.

In February 1988, it brightened by 75%, which is typical of comets but not asteroids.  In April 1989, it developed a cometary coma, and in 1993, it formed a tail.  

Eris, the most massive dwarf planet, discovered 2005

Eris, discovered January 5, 2005, is the most massive dwarf planet in our solar system, but slightly smaller than Pluto.  The team of Mike Brown, Chad Trujillo and David Rabinowitz discovered Eris from pictures taken in October 2003 and made the announcement in July 2005.

It has an orbit of 558 years and at its closest approach to the sun it is 37.91 astronomical units.  At its maximum, it is almost three times that distance at 97.65 AU.  Eris has one moon named Dysnomia, which, in Greek mythology, is the daughter of Eris.

Although more massive than Pluto, Eris is slightly smaller.