What type of Galaxy do astronomers consider to be the oldest?

There are two main types of galaxies: spirals and ellipticals. Spirals, like the Milky Way, are essentially rotating disks. Ellipticals tend to be more massive, are football-shaped, and have stars flying around randomly in all directions. read more

The oldest galaxies are, of course, the galaxies that formed earliest. If they formed early, they had plenty of time to merge with other galaxies. Mergers make the final galaxy heavier and disrupt the structure of both galaxies, so that even spiral galaxies would have their stars’ motions randomized. read more

Astronomers have discovered the oldest known stars, dating from before the Milky Way Galaxy formed, when the Universe was just 300 million years old. The stars, found near the centre of the Milky Way, are surprisingly pure but contain material from an even earlier star, which died in an enormous explosion called a hypernova. read more

Astronomers now know that it is NOT an evolutionary sequence because each type of galaxy has very old stars. The oldest stars in any galaxy all have about the same age of around 13 billion years. This means that spirals form as spirals, ellipticals form as ellipticals, and irregulars form as irregulars. read more