The barred spiral galaxy is a fascinating class of galaxies in the universe. They are characterized by the presence of a central bar-shaped structure composed of stars, around which the spiral arms of the galaxy extend. This article explores some of the most popular and well-known barred spiral galaxies, delving into their unique features, history, and significance in the field of astronomy.
1. Milky Way Galaxy
The Milky Way, our home galaxy, is perhaps the most famous example of a barred spiral galaxy. Although it’s challenging to observe its structure from within, studies and indirect observations suggest that the Milky Way has a prominent central bar. The bar is believed to be about 27,000 light-years in length, significantly impacting the dynamics of the galaxy, including the orbits of stars and the distribution of gas and dust. The Milky Way’s spiral arms, rich in star-forming regions, extend from the ends of the bar.
2. NGC 1300
NGC 1300 is a striking example of a barred spiral galaxy located about 69 million light-years away in the constellation Eridanus. It spans approximately 110,000 light-years in diameter. NGC 1300 is renowned for its vividly defined central bar and well-structured spiral arms. The Hubble Space Telescope has captured stunning images of this galaxy, revealing the intricate details of its arms and the dense cluster of stars at its core.
3. NGC 1097
Located about 45 million light-years away in the constellation Fornax, NGC 1097 is another spectacular barred spiral galaxy. It is particularly known for its unique features, including a series of star-forming regions that appear like a ring around the galaxy’s central black hole. This galaxy also has a set of faint outer arms that make it one of the more intriguing and studied objects in the night sky.
4. NGC 1365
NGC 1365, also known as the Great Barred Spiral Galaxy, is part of the Fornax Cluster and lies about 56 million light-years away. It is one of the most prominent and well-studied barred spiral galaxy in the sky. The galaxy is notable for its symmetrically well-defined bar and prominent spiral arms. The central region of NGC 1365 is highly active, housing a supermassive black hole that significantly influences the galaxy’s dynamics.
5. Messier 83 (M83)
Messier 83, also known as the Southern Pinwheel Galaxy, is located about 15 million light-years away in the constellation Hydra. It is one of the closest and brightest barred spiral galaxy, making it a popular subject for amateur and professional astronomers alike. M83 is known for its widespread star formation, particularly in its central bar, which has resulted in numerous supernovae being observed in this galaxy.
6. NGC 7479
NGC 7479, located in the constellation Pegasus, is another prominent barred spiral galaxy. The galaxy, located approximately 105 million light-years away, is notable for its strong bar and asymmetrical spiral arms. These features likely result from past gravitational interactions with other galaxies. The central region of NGC 7479 is highly active, with intense star formation and a supermassive black hole at its core.
7. NGC 1302
NGC 1302 is a lesser-known but equally fascinating barred spiral galaxy, located in the constellation Eridanus. It is about 61 million light-years away and is characterized by its small but well-defined central bar and spiral structure. NGC 1302 is an example of how barred spiral galaxy can vary significantly in size and appearance.
8. Messier 95 (M95)
Messier 95, located about 33 million light-years away in the constellation Leo, is a barred spiral galaxy with a distinct ring-like structure surrounding its bar. This feature is thought to be a result of resonances with the bar’s rotation, leading to enhanced star formation in the ring. M95 is part of the Leo I Group of galaxies and is often studied in conjunction with its neighbors, Messier 96 and Messier 105.
9. NGC 1512
NGC 1512 is a barred spiral galaxy located about 30 million light-years away in the constellation Dorado. The extended bar, known for stretching over 70,000 light-years, and a striking dust lane that intersects the bar, are its notable features. This galaxy is also noteworthy for its interactions with the nearby dwarf galaxy NGC 1510, influencing its structure and star formation.
10. NGC 4314
NGC 4314 is a barred spiral galaxy in the constellation Coma Berenice, about 40 million light-years away. This galaxy is particularly interesting for its central region, which contains a ring of young stars and star clusters, indicating recent star formation activity. NGC 4314’s bar appears to funnel gas and dust into this central region, triggering the formation of new stars.
What is the difference between elliptical and barred spiral galaxies?
Elliptical and barred spiral galaxies are two distinct types of galaxies with several key differences:
Shape and Structure
- Elliptical Galaxy: These galaxies have an ellipsoidal shape and appear as elongated spheres. They lack a distinct structure and do not have spiral arms. Elliptical galaxies range from nearly spherical (E0) to highly elongated (E7).
- Barred Spiral Galaxy: As a subclass of spiral galaxies, barred spirals feature a central bar-shaped structure composed of stars. From the ends of the bar, spiral arms extend outward. This bar is a prominent feature distinguishing them from regular spiral galaxies.
- Elliptical Galaxy: Generally older and contains older stars, with little to no ongoing star formation. They consist mostly of old, red stars and have a low content of gas and dust, which are essential for forming new stars.
- Barred Spiral Galaxy: They are active sites of star formation, especially along their spiral arms. The bar structure is believed to channel gas from the galaxy’s disk towards the center, potentially enhancing star formation.
Size and Mass
- Elliptical Galaxy: Can vary significantly in size, ranging from dwarf ellipticals to giant ellipticals. The largest galaxies in the universe are typically elliptical galaxies.
- Barred Spiral Galaxy: These galaxies also vary in size but are generally not as massive as the largest ellipticals.
Distribution in the Universe
- Elliptical Galaxy: More common in densely populated regions of the universe, like galaxy clusters.
- Barred Spiral Galaxy: More frequently found in less densely populated regions, like the outskirts of galaxy clusters or more isolated environments.
- Elliptical Galaxy: Stars in elliptical galaxies move in random orbits, giving these galaxies their rounded shape.
- Barred Spiral Galaxy: Stars and gas in these galaxies follow more ordered paths – stars in the disk mostly move in circular orbits, while stars in the bar can follow more elliptical or straight-line orbits.
Color and Brightness
- Elliptical Galaxy: Generally appear redder and dimmer due to older star populations.
- Barred Spiral Galaxy: Tend to be brighter and bluer because of younger, hotter stars in the spiral arms.
Barred spiral galaxies, with their unique structures and dynamic processes, offer invaluable insights into the workings of the universe. From the familiar spirals of the Milky Way to the striking bars of NGC 1300 and the star-forming rings of M95, each galaxy presents a unique story about the evolution and characteristics of these cosmic structures. The study of these galaxies not only enhances our understanding of the universe but also brings into focus the incredible diversity and beauty of the cosmos.