Q 01/05

Eris holds which record among the dwarf planets?

A) Largest by diameter

B) Closest to the Sun

C) Most massive

D) Most moons

Answer · why

C) Most massive

It outweighs Pluto by about 27%, though Pluto is a hair wider.

Q 02/05

Who led the team that discovered Eris?

A) Mike Brown

B) Alan Stern

C) Clyde Tombaugh

D) Carolyn Shoemaker

Answer · why

A) Mike Brown

Chad Trujillo and David Rabinowitz were his co-discoverers; Brown later wrote a book called How I Killed Pluto.

Q 03/05

In what year was Eris discovered on archived images?

A) 1992

B) 1998

C) 2001

D) 2005

Answer · why

D) 2005

The images had been taken in October 2003 but its slow motion had been filtered out by the search software.

Q 04/05

Which observatory's Samuel Oschin telescope took the images in which Eris was found?

A) Mount Wilson

B) Lowell

C) Palomar

D) Keck

Answer · why

C) Palomar

The 1.2-metre Schmidt camera in California had already found Quaoar, Orcus and Sedna for the same team.

Q 05/05

Why did the search software initially miss Eris in the 2003 images?

A) It moved too slowly across the sky

B) It was outside the camera field

C) It was hidden behind a bright star

D) It was far too faint to register

Answer · why

A) It moved too slowly across the sky

The code ignored anything slower than 1.5 arcseconds per hour; Sedna's discovery prompted a re-check by eye.