How are the bars in barred spiral galaxies thought to have formed?(1 point) Responses separation separation merging merging primordial collapse primordial collapse slow evolution
The bars in barred spiral galaxies are thought to have formed through a process called primordial collapse.
The bars in barred spiral galaxies are thought to have formed through a process known as slow evolution.
The bars in barred spiral galaxies are thought to have formed through a process called "slow evolution." To understand this, let's break it down step by step:
1. Start with a spiral galaxy: Barred spiral galaxies are a type of spiral galaxy that have a central bar structure cutting through the center of the galaxy.
2. Spiral arms form: Spiral galaxies initially have spiral arms that extend out from the center. These arms are made up of stars, gas, and dust.
3. Density waves: As the galaxy rotates, density waves can form within it. These waves are regions of higher density that move through the galaxy, causing gravitational disturbances.
4. Instability: The density waves can trigger gravitational instabilities in the spiral arms. As a result, some of the stars and gas within the arms start to migrate towards the center.
5. Bar formation: Over time, this inward migration of stars and gas can lead to the formation of a bar structure. The bar is essentially a concentration of stars and gas along the central region of the galaxy.
6. Ongoing evolution: Once the bar forms, it continues to evolve as the galaxy rotates. It can grow longer or shorter, thinner or thicker, depending on various factors such as the amount of material involved and the gravitational interactions within the galaxy.
It's important to note that the exact mechanisms and timescales for bar formation in barred spiral galaxies are still an active area of research in astrophysics. However, the process of slow evolution through density waves and gravitational instabilities is currently our best understanding of how bars are thought to form in these galaxies.