What is a spiral galaxy in astronomy?

A spiral galaxy typically has a rotating disc with spiral ‘arms’ that curve out from a dense central region. The Milky Way is a spiral galaxy. Four classes are used to classify galaxies: spiral; barred spiral; elliptical and irregular.

What is a spiral galaxy simple definition?

Spiral galaxies are twisted collections of stars and gas that often have beautiful shapes and are made up of hot young stars. Most of the galaxies that scientists have discovered so far are spiral galaxies, as opposed to the other two main categories of galaxy shapes — elliptical and irregular.

What is a spiral shape galaxy?

Spiral galaxies have a central bulge of stars surrounded by a disk that contains arms, which form a spiral structure. Stars in the bulge of a spiral galaxy tend to be older and redder than the rest. There’s also a much fainter, roughly spherical, stellar halo encompassing the disk.

How does a spiral galaxy work?

Spirals exist only among flattened or ‘disk’ galaxies. These galaxies are differentially rotating–that is, the time to complete a full rotation increases with distance from the center. Differential rotation causes any disturbance in the disk to wind up into a spiral form.

Which statement describes a characteristic of a spiral galaxy?

Which statement describes a characteristic of a spiral galaxy? It is shaped like a pinwheel. Which phrase describes an irregular galaxy?

What are 3 characteristics of spiral galaxies?

Spiral galaxies usually consist of a rotating disk that contains stars, dust, gas, and a concentration of stars known as the bulge in the center.

What is the spiral shape?

A spiral is a shape which winds round and round, with each curve above or outside the previous one. […]

How is a spiral galaxy formed?

In the process of merging, a disk is formed and stars are born in this disk. As small galaxies pass around the periphery of this disk, the effects of their gravity create a spiral structure in the disk. Spiral galaxies like our Milky Way Galaxy are thought to be formed in this manner.

What are the two types of spiral galaxies?

Spiral galaxies appear as flat, blue-white disks of stars, gas and dust with yellowish bulges in their centers. These galaxies are divided into two groups: normal spirals and barred spirals.

What phrase best defines a galaxy?

Galaxy is a collection of millions or even billions of stars, gas, and dust held together by force of gravity, so the answer is: ´´a large collection of stars, gas, and dust held together by gravity´´.

What causes spiral galaxies?

Astronomers believe that galaxies have spiral arms because galaxies rotate – or spin around a central axis – and because of something called “density waves.” A spiral galaxy’s rotation, or spin, bends the waves into spirals. Stars pass through the wave as they orbit the galaxy center.

Why are spiral galaxies the most common?

New research finds that spiral arms are self-perpetuating, persistent, and surprisingly long lived. Spiral galaxies make up roughly 77 percent of the galaxies that scientists have observed. Because elliptical galaxies are made up of older, dimmer stars, they are more challenging to spot.

What are the characteristics of a spiral galaxy?

Characteristics and classifications. Most spiral galaxies contain a central bulge surrounded by a flat rotating disk of stars. Made up of older, dimmer stars, the bulge in the center is thought to contain a supermassive black hole, though observing it can be a challenge.

What are the four main parts of a spiral galaxy?

The four main parts are the disk, the nuclear bulge, the halo, and the galactic corona. galaxy disk: the large, flat point of a spiral galaxy, rotating around its center. The disk is where the sun orbits. contains individual stars, clusters of stars, and almost all of the gas and dust found in the galaxy.

What does spiral galaxy mean?

spiral galaxy. noun. : a galaxy exhibiting a central nucleus or barred structure from which extend curved arms of higher luminosity.

What are the properties of a spiral galaxy?

Shape and structural properties. Highly flattened disk of stars and gas, containing spiral arms and thickening to central bulge. Sa and Sba galaxies have largest bulges, the least obvious spiral structure, and roughly spherical stellar halos. SB galaxies have an elongated central “bar” of stars and gas.