A Galaxy

Question 1

basic information

Answer 1

Spiral galaxy, approximately 2.5 million light-years from Earth, and the nearest major galaxy to the Milky Way.
About 25%-50% more massive than Milky Way.
Has a diameter of about 220,000 lightyears.

Question 2

Observation history

Answer 2

In 1917,Heber Curtisobserved anova within Andromeda.
In 1925, Edwin Hubbleidentified extragalacticCepheid variable starsfor the first time on astronomical photos of Andromeda.

Question 3

What type of galaxy is Andromeda?

Answer 3

A barred spiral galaxy.

Question 4

Inner structure

Answer 4

Has a dense and compact star cluster at its center.

Question 5

Halo

Answer 5

Andromeda Galaxy is surrounded by a massive halo of hot gas that is estimated to contain half the mass of the stars in the galaxy. The nearly invisible halo stretches about a million light-years from its host galaxy.

Question 6

History

Answer 6

Formed roughly 10 billion years ago from the collision and subsequent merger of smallerprotogalaxies

Question 7

How fast is it approaching Earth?

Answer 7

The Andromeda Galaxy is approaching theMilky Wayat about 110 kilometers per second (68 miles per second). And is expected to collide with Earth in 4 billion years.