Galaxies for the Guilty by Berdan Andernacht

She was studying how galaxies spin when she realized the vast spiral Andromeda Galaxy seemed to be rotating strangely. In the late 1970s, astronomer Vera Rubin made the surprising discovery of dark matter. These include those in the process of colliding or interacting, and those with active nuclei ejecting jets of gas.

These galaxies are abundant in the early universe, before spirals and ellipticals developed.Īside from these three classic categories, astronomers have also identified many unusually shaped galaxies that seem to be in a transitory phase of galactic development. Astronomers often see irregular galaxies as they peer deeply into the universe, which is equivalent to looking back in time. Irregular galaxies, which have very little dust, are neither disk-like nor elliptical. Spirals are actively forming stars and comprise a large fraction of all the galaxies in the local universe. The arms of barred spirals usually start at the end of the bar instead of from the bulge. In barred spirals, the bar of stars runs through the central bulge.

These galaxies are divided into two groups: normal spirals and barred spirals. Spiral galaxies appear as flat, blue-white disks of stars, gas and dust with yellowish bulges in their centers. Much more common are dwarf ellipticals, which are only a few thousand light-years wide. Astronomers theorize that these are formed by the mergers of smaller galaxies. The largest and rarest of these, called giant ellipticals, are about 300,000 light-years across. They possess comparatively little gas and dust, contain older stars and are not actively forming stars anymore. These galaxies span a wide range of sizes, from dwarf galaxies containing as few as 100 million stars to giant galaxies with more than a trillion stars.Įllipticals, which account for about one-third of galaxies observed, vary from nearly circular to very elongated. Four Successful Women Behind the Hubble Space Telescope's AchievementsĪstronomers classify galaxies into three major categories: elliptical, spiral and irregular.Characterizing Planets Around Other Stars.Measuring the Universe's Expansion Rate.

Galaxies for the Guilty by Berdan Andernacht