Q 01/05

Eris holds which record among the known dwarf planets?

A) Largest by diameter

B) Closest to the Sun

C) Most massive

D) Most moons

Answer · why

C) Most massive

Most massive. Eris outweighs Pluto by about 27%, yet the two are almost exactly the same width, so Eris must be much the denser world.

Q 02/05

Which asteroid-belt world was named a dwarf planet alongside Eris and Pluto in 2006?

A) Vesta

B) Ceres

C) Pallas

D) Hygiea

Answer · why

B) Ceres

Ceres. It had been here before: announced as a new planet in 1801, it was demoted to an asteroid as similar bodies kept turning up, then promoted agai...

Q 03/05

Which distant object's discovery prompted the re-check of old images that revealed Eris?

A) Quaoar

B) Sedna

C) Varuna

D) Ixion

Answer · why

B) Sedna

Sedna. Finding a world that far out convinced the team that others might be hiding in pictures they had already taken, and a second look turned up Eri...

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) Kitt Peak

Answer · why

C) Palomar

Palomar. Its survey photographed each patch of sky three times over three hours, and anything that shifted against the background stars was flagged as...

Q 05/05

Why did search software miss Eris in the 2003 images?

A) It moved too slowly across the sky

B) It sat outside the camera field

C) A bright star's glare hid it

D) It was too faint to register

Answer · why

A) It moved too slowly across the sky

It moved too slowly across the sky. To cut false alarms, the software ignored anything drifting under 1.5 arcseconds an hour; Eris surfaced when the t...