Real Milky Way is lighter than previously thought
Like the chocolate bar that bears its name, the Milky Way galaxy is lighter than it might first appear.
Now scientists have discovered that the real Milky Way, the galaxy containing the sun and its family of planets, is lighter than was previously thought.
In fact, it has about half the mass of one of its closest neighbours, the Andromeda galaxy, 2.5 million light years away.
Both are similar types of spiral galaxy and the largest in a clump of galaxies known as the Local Group.
Scientists believe that Andromeda's extra weight must be in the form of dark matter, an invisible substance which is thought to bind galaxies together with its gravity.