Why do the spiral arms show up so clearly in spiral galaxies?
Why do the spiral arms show up so clearly in spiral galaxies?
Why do the spiral arms show up so clearly in spiral galaxies? Stars are spread almost uniformly throughout the disk of the galaxy outside the nuclear bulge, but the brightest stars occur only in the spiral arms, making the arms stand out. You just studied 9 terms!
Why are the spiral arms of a galaxy so bright?
Spiral arms appear visually brighter because they contain both young stars and more massive and luminous stars than the rest of the galaxy. As massive stars evolve far more quickly, their demise tends to leave a darker background of fainter stars immediately behind the density waves.
What is a spiral arm Tracer?
1- Spiral tracers • Spiral tracers are objects that are commonly found in spiral arms and so. are used to trace spiral structure. • Photos in blue taken of nearby spiral galaxies such as M31 (Andromeda. galaxy) show the bluish spiral arms distinctly.
Why do the spiral arms appear blue?
The gas and dust in the arms filter out all but the blue light from stars in the arms. Stars are forming in the spiral arms so there are many more high mass, hot, blue stars. Almost all the stars of the disk are in the arms of the galaxy and their light makes it appear blue.
What use are 21 cm radio waves to galactic astronomers?
The 21-centimetre radiation readily penetrates the clouds of interstellar dust particles that obstruct optical observations deep into the galactic centre and thus allows the mapping of the galaxy’s spiral structure.
What do the spiral arms in spiral galaxies contain quizlet?
The spiral arms are made up of gas, dust, and new stars that have formed in these denser regions of gas and dust. Why is it hard to tell what type of galaxy we live in (Milky Way)? the gas, dust, and stars keep astronomers from having a good view of our galaxy.
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 objects make good spiral tracers?
A spiral tracer is any object that is only found in spiral arms and therefore detection of the locations of these objects trace out the locations of spiral arms. Some good spiral tracers are: O&B stars, emission nebulae, young clusters and neutral hydrogen (which emits 21 cm radiation).
What spectral classes of stars work best as spiral tracers?
Galactic fossils. Stars with masses equal to that of the Sun or below, which have spectral class F, G and K (the Sun is a class G star), are the perfect tracers for studies of the Milky Way for several reasons.
What color are the spiral arms Why?
Spiral Galaxies Waves propagating through the disk form the spiral arms that we see, and cause the gas clouds to collapse and form new stars. Because the spiral arms are regions of active star formation they contain many hot young blue and blue-white stars, making them extremely visible.
What galaxy is red?
elliptical galaxies
Because star-forming activity in many giant elliptical galaxies has shut down to very low levels, these galaxies mostly house long-lived stars with low masses and red optical colors. Astronomers have therefore called these galaxies “red and dead”.
What is true of spiral galaxies?
Most spiral galaxies contain a central bulge surrounded by a flat, rotating disk of stars. The bulge in the center is made up of older, dimmer stars, and is thought to contain a supermassive black hole. Approximately two-thirds of spiral galaxies also contain a bar structure through their center, as does the Milky Way.
What is the significance of the 21 cm spectral line?
In radio astronomy. The 21 cm spectral line appears within the radio spectrum (in the L band of the UHF band of the microwave window to be exact). Electromagnetic energy in this range can easily pass through the Earth’s atmosphere and be observed from the Earth with little interference.
What are radioactive tracers used for?
Radioactive tracers are also used in hydraulic fracturing. This is the fracturing of underground rock layers (and is often called fracking). A pressurised liquid is forced into the rock layers which fracture and release natural gas which is collected and sold.
Why map the intensity of redshifted 21 centimeter radiation?
First, by mapping the intensity of redshifted 21 centimeter radiation it can, in principle, provide a very precise picture of the matter power spectrum in the period after recombination.
How is the 21 cm line used to map a galaxy?
The Hydrogen 21-cm Line The hydrogen in our galaxy has been mapped by the observation of the 21-cm wavelength line of hydrogen gas. At 1420 MHz, this radiation from hydrogen penetrates the dust clouds and gives us a more complete map of the hydrogen than that of the stars themselves since their visible light won’t penetrate the dust clouds.
