Elliptical galaxies could be formed by the collision and merging of two spiral galaxies.
What is galaxy?
Galaxy is the huge collection of stars, interstellar gases, dust particles, stones. Galaxies tend to come in two shapes such as spirals and ellipticals.
In spiral galaxies, the stars orbit in a very thin disk, and all the stars move in the same direction. Two or more spiral arms wind around the center just like a pinwheel.
Selecting a sample of about 50 spiral galaxies that have collided and in the process of merging into a single object. We took infrared images using the UH 88-inch (2.2-meter) telescope, and obtained spectra of these mergers using one of the Keck telescopes.
Infrared images are used to see, if the starlight in these objects decreases with distance from the center of the galaxy the way it does in spirals or the way it does in ellipticals. The light intensity decreases exponentially in outward direction from the centers of spirals, but it declines much more slowly with distance from the center for ellipticals. It is found that at least 45 out of 51 mergers are ellipticals.
Thus, most of these mergers really are evolving into elliptical galaxies.
Learn more about galaxy.