What is the major disadvantage of Hubble’s classification system? More than two-thirds of all observed galaxies are spiral galaxies. In 1936, Hubble debuted a way to classify galaxies, grouping them into four main types: spiral galaxies, lenticular galaxies, elliptical galaxies, and irregular galaxies. You might be interested: What Are The Purposes Of The Laws Congress Passes? Why is Hubble’s law so important?īecause the exact value of the Hubble constant, H, is so important in extragalactic astronomy and cosmology – it leads to an estimate of the age of the universe, helps test theories of Dark Matter and Dark Energy, and much more – a great deal of effort has gone into working it out. Galaxy orbiting due to gravitational movements. What are the limitations of Hubble’s law?įollowing are the limitations of Hubble’s law which makes the measurement challenges: Because of the intrinsic motion of galaxies, observed velocity gets influenced. … An SBc galaxy in the Hubble classification system would have… a barred spiral shape with loose arms. How were astronomers able to determine that the spiral nebulae were actually distant galaxies? Edwin Hubble discovered a Cepheid in M31 and determined its distance to be well outside of the Milky Way. How were astronomers able to determine that the spiral nebulae were actually distant galaxies? First, Hubble divided the galaxies into two general categories: elliptical and spiral galaxies. Astronomers use his system, called the “Hubble Tuning Fork,” even today. What became of Hubble’s system of classifying galaxies?Īfter he discovered what galaxies really were, Edwin Hubble became the first person to classify galaxies. … For nearby galaxies, though, their peculiar velocity is larger than their velocity from the expansion, so their peculiar velocity dominates their total velocity, causing them to lie far from the line relating velocity to distance. They are: Hubble’s Law only works for distant galaxies. The elliptical galaxies made up the fork's handle, and spiral galaxies and barred spiral galaxies make the fork's prongs. Hubble classified the galaxies using a 'tuning fork' system. Why do we say that galaxies in the Local Group don’t obey the Hubble’s law? In the early 1900s, Edwin Hubble looked at galaxies like the ones you saw in the last few pages.