Q 01/05

What type of galaxy is the Milky Way?

A) Lenticular

B) Elliptical

C) Barred spiral

D) Irregular

Answer · why

C) Barred spiral

Astronomers began suspecting a central bar in the 1960s, and infrared observations in 2005 confirmed it was bigger than expected.

Q 02/05

Roughly how many stars is the Milky Way estimated to contain?

A) Between 1 and 4 trillion

B) Between 10 and 40 billion

C) Between 100 and 400 billion

D) Between 1 and 4 billion

Answer · why

C) Between 100 and 400 billion

The uncertainty comes from very-low-mass stars that are hard to detect; there are thought to be at least as many planets as stars.

Q 03/05

The Sun sits on the inner edge of which spiral arm?

A) The Sagittarius Arm

B) The Scutum-Centaurus Arm

C) The Perseus Arm

D) The Orion Arm

Answer · why

D) The Orion Arm

We are about 27,000 light-years from the Galactic Center; the next arm out, the Perseus Arm, is around 6,500 light-years away.

Q 04/05

What is the intense radio source at the Galactic Center called?

A) Sagittarius A*

B) Cygnus X-1

C) Scorpius X-1

D) Centaurus A

Answer · why

A) Sagittarius A*

It marks a supermassive black hole; the '*' is pronounced 'star'.

Q 05/05

Roughly how massive is the black hole at the centre of the Milky Way?

A) About 40,000 solar masses

B) About 4 billion solar masses

C) About 4,000 solar masses

D) About 4 million solar masses

Answer · why

D) About 4 million solar masses

It is a quiet giant, accreting only about a hundred-thousandth of a solar mass per year, typical of an inactive galactic nucleus.