What is a density wave and how is it defined?

[′den·səd·ē ‚wāv] (physics) A sound wave or other type of material wave which causes the density of the matter through which it passes to alternately rise above and drop below its mean value.

What is meant by a density wave?

“A density wave is shorthand to describe the way stars in a galaxy are packed a little more closely together in the arms and spread more thinly in between the arms.

What is a density wave in astronomy?

One of the more successful models developed to explain the origin of spiral arms in galaxies is the density wave model. It is particularly good in describing the formation of the spiral structure we see in grand design spirals.

What does density wave theory predict?

The density-wave theory of galactic spiral-arm structure makes a striking prediction that the pitch angle of spiral arms should vary with the wavelength of the galaxy’s image. The reason is that stars are born in the density wave but move out of it as they age.

What is the density wave model quizlet?

Density wave theory. A model for spiral galaxies that proposes that the arms are the result of density waves sweeping around the galaxy. • A density wave is a wave in which areas of high and low pressure move through the medium. lThe stars revolve around the Galaxy independent of the spiral arms.

What are spiral density waves directly responsible for?

Overall, spiral density waves are what form two well-defined spiral arms, but self-sustaining star formation and differential rotation is what’s responsible for the production of many discontinuous branches, spurs, and little arms in a galaxy.

What is the source of energy that makes emission nebulas glow quizlet?

Emission are found near hot, luminous stars of spectral types O and B, which is is the main factor behind what makes the IC 434 emission nebula glow. These luminous stars emit large amounts of ultraviolet radiation, which is then absorbed by nearby interstellar gas, for which the atoms of the gas become ionized.

What process makes a red emission nebula glow?

As these atoms fall back to lower energy states, they emit radiation. The process is similar to that of a neon light. This causes the nebula to glow. Emission nebulae tend to be red in color because of the abundance of hydrogen.

What is the primary visible color of emission nebula?

The predominant color of emission nebulae is blue. Emission nebulae are created by gas absorbing ultraviolet energy from the hot young stars within them, such as in the Orion Nebula.

Which nebulae emits their own light because luminous ultraviolet stars ionize gas in the nebula?

Emission nebulae

temperature. clouds or nebulae (one nebula, two nebulae). Emission nebulae emit their own light because luminous ultraviolet stars (spectral type O,B) ionize gas in the nebula. The gas then emits light as the electrons return to lower energy levels.

Why is reflection nebula blue?

Explanation: Reflection nebulae reflect light from a nearby star. Many small carbon grains in the nebula reflect the light. The blue color typical of reflection nebula is caused by blue light being more efficiently scattered by the carbon dust than red light.

Do nebulae emit visible light?

Emission nebulae are clouds of ionised gas that, as the name suggests, emit their own light at optical wavelengths.

Are planetary nebulae emission or absorption nebulae?

A planetary nebula (PN, plural PNe), is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term “planetary nebula” is a misnomer because they are unrelated to planets.

How does a protostar become a real star?

A protostar becomes a main sequence star when its core temperature exceeds 10 million K. This is the temperature needed for hydrogen fusion to operate efficiently. The length of time all of this takes depends on the mass of the star. The more massive the star, the faster everything happens.

Can a nebula only become a star?

Nebulae are often star-forming regions, such as in the “Pillars of Creation” in the Eagle Nebula. In these regions, the formations of gas, dust, and other materials “clump” together to form denser regions, which attract further matter, and eventually will become dense enough to form stars.

Is a nebula bigger than a galaxy?

Simply put, the main difference between galaxies and nebulae are an extreme difference in size, as well as their basic structure. A nebula is a cloud of dust and gas, usually tens to hundreds of light years across. A galaxy is much larger — usually thousands to hundreds of thousands of light years across.

What’s the gravity of a black hole?

The black hole would have the same gravity as the sun. Earth and the other planets would orbit the black hole as they orbit the sun now. The sun will never turn into a black hole.

Is a star bigger than an asteroid?

1 Answer. Phillip E. From largest to smallest they are: Universe, galaxy, solar system, star, planet, moon and asteroid.

How much bigger is the Milky Way than Saturn?

About how many times larger is the diameter of the Milky Way Galaxy than the diameter of Saturn’s rings? (Data: Saturn’s rings are about 270000 km in diameter; the Milky Way is 100000 light-years in diameter.

When did humans learn that the Earth is not the center of the universe?

In 1543, Polish astronomer Nicolaus Copernicus questioned the idea that the Earth was the center of the universe, but couldn”t provide proof. Galileo did.

How long would it take to travel 4.4 light-years?

Last year, astronomers raised the possibility that our nearest neighbor, Proxima Centauri, has several potentially habitable exoplanets that could fit the bill. Proxima Centauri is 4.2 light-years from Earth, a distance that would take about 6,300 years to travel using current technology.

What is the name of the galaxy Earth belongs to?

the Milky Way Galaxy

We live on a planet called Earth that is part of our solar system. But where is our solar system? It’s a small part of the Milky Way Galaxy. A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems.

What is the Milky Way in space?

The Milky Way is a large barred spiral galaxy. All the stars we see in the night sky are in our own Milky Way Galaxy. Our galaxy is called the Milky Way because it appears as a milky band of light in the sky when you see it in a really dark area.

How many suns are in the Milky Way?

2. How many suns are there in this universe? There are an estimated 100 billion stars in our Milky Way galaxy alone, making up about 100 billion suns. So there are likely billions of other galaxies with billions of suns.