2.What are RR Lyrae stars? Why are they useful for determin-ing the distance fro
ID: 1608030 • Letter: 2
Question
2.What are RR Lyrae stars? Why are they useful for determin-ing the distance from our solar system to the center of theGalaxy?
How do astronomers determine the distances to H I (neutralhydrogen) clouds?
What kinds of objects (other than H I clouds) do astronomersobserve to map out the Galaxy’s spiral structure? What isspecial about these objects? Which of these can be observedat great distances?
What is the difference between dark matter and dark nebulae?
What is the winding dilemma? What does it tell us about thenature of spiral arms?
Explanation / Answer
RR lyrae stars are commonly found in clusters and are used to measure (extra)galactic distances.
it is found useful for determining the distance from our solar system to the center of the galaxy because beyond the milky way it is very difficult to measure because of low luminosity. thats why we used in globular cluster studies.
HI is a technique used to determine the structure of spiral galaxies and it is also used to determine the gravitational interuption between the galaxies.
HI cloud is a technique in which hydrogen is neutral. As we know that matter between the stars in the Milky Way Galaxy, occurs in the form of relatively cold neutral hydrogen gas. Neutral hydrogen clouds are easily identify at radio wavelengths because they emit a wavelength of 21 cm.
The HI clouds are also useful to map out the structure of our Galaxy even in regions which do not contain large amounts of normal stars.
We are able to observed the distance which are less luminous and also which are not possible to see from a any other instrument.
Tha basic diffrence between the dark matter and dark nebulae is that the dark matter produces an attractive force (gravity) while the dark nebulae produces the repulsive force (anti gravity). as per the fact . together they made up 96% of our universe.
spiral arms is the structure which rotate about our galaxy. it is not of spiral shape.this Differential rotation in the galaxy "wrap" the spiral arms around the nucleus. This is called the "Winding Dilemma" because it is clear that the spiral patterns that we see in galaxies must b elong lived.
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