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

Barred spiral: a long bar of old stars crosses the centre instead of the arms winding right in. A 2005 infrared survey of some 30 million stars showed...

Q 02/05

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

A) Between 1 and 4 billion

B) Between 10 and 40 billion

C) Between 100 and 400 billion

D) Between 1 and 4 trillion

Answer · why

C) Between 100 and 400 billion

Between 100 and 400 billion is the usual estimate. The range is wide because we count from inside the galaxy, and its dim, low-mass stars are very har...

Q 03/05

The Sun sits in which spiral arm of the Milky Way?

A) The Sagittarius Arm

B) The Scutum-Centaurus Arm

C) The Perseus Arm

D) The Orion Arm

Answer · why

D) The Orion Arm

The Orion Arm, a minor spur between two larger arms. It puts us about 26,000 light-years from the centre, roughly halfway to the edge, in what NASA ca...

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*

Sagittarius A*, said 'A-star', marks the galaxy's supermassive black hole. In 2022 the Event Horizon Telescope released the first image of it: a glowi...

Q 05/05

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

A) About 4,000 solar masses

B) About 40,000 solar masses

C) About 4 million solar masses

D) About 4 billion solar masses

Answer · why

C) About 4 million solar masses

About 4 million solar masses, weighed by tracking stars that whip around an invisible object at the centre. That work won Reinhard Genzel and Andrea G...