Q:1 What Is the Accurate

Q:1 what is the accurate speed of light in km/sec? calculate the time required from the sun light to come to earth from the sun. how long would it take the light to travel from one end of the milky wave to the other end that is 10,000 light years long? Compute the sun's angular diameter as seen from the earth. why the modern astronomers, physicist and engineers are always trying to determine the true nature of the sun?

The speed of light is 299,728,377 km/sec.

The average distance of the sun from earth is 146,000,000 km.

Light travels 17.98 million minute.

Therefore, the light from the sun reaches earth in approximately

minutes.

By definition, lights travels 10,000 light years in 10,000 years.

Therefore, light would travel from one end to the other in 10,000 years.

The diameter of the sun is 1,390, 000 km.

The angular size of the sun is its diameter divided by its distance from the reference point.

1,390,000km/149,000km = 0.009 radians = 0.5 degrees (assuming 1

radian = 57 degrees).

The sun is important for many reasons. It is fueled by the same process of nuclear fusion that coverts hydrogen into helium that was initially responsible for the creation of all matter. This process could be crucial for future methods of synthetic energy production to replace fossil fuels. The sun is the nearest star to earth and provides the best opportunity to study the manner in which all stars evolve and change.

The sun is the source of solar flares and solar winds and directly affect climactic conditions on the earth.

Q:2 Describe characteristics of the sun's photosphere. what are sun spots, describe their properties. how do sun spots effect the earth? what is the solar wind and is it related to sun spots?

The sun's surface features faculae, granules, supergranules, and sunspots. Sunspots are the most important feature from our perspective because they produce the solar wind that is responsible for heating the earth's upper atmosphere by virtue of ultraviolet light and x-rays. Sunspots are dark regions on the sun's surface that represent comparatively cooler areas. They represent powerful magnetic fields that generate a magnetic solar "wind" that force solar gases past the earth at high speed, disruption power systems and the orbits of satellites.

Q:3 what is meant by the helium flash? when does it accrue in the evolution of the stars? what are variable stars? what are the cepheid variables, describe their behavior and how are they used in astronomy?

Toward the end of the life of relatively small stars of about 2.25 solar masses, when the core no longer has enough hydrogen to maintain fusion to resist the inward force of gravity from the mass of the star. The collapse increases internal pressure until some of the stars external matter is ejected, eventually stabilizing into a dwarf star of degenerate matter.

A variable star is one whose apparent brightness changes as viewed from earth. Cepheid variables are a certain type of variable star whose apparent brightness changes in regular cycles lasting from 3 to 50 days. Astronomers use them to measure distances in space.

Q: 4 describe and explain the characteristic of Hertzsprung-Russell diagram.

what is the significant and use of this diagram? how is a black hole formed? what are the properties of black holes? compute the Schwarzschild radius for the sun.

What happens when the star shrinks to the radii? what is the most likely place to find a black hole?

The Hertzsprung-Russell diagram is a scatter-graph of stars that allows astronomers to plot their absolute luminosity against their specific classifications and temperatures. This technique demonstrated that the temperature and luminosity of stars are not random but related in such a way as to permit classification.

Stars much larger than that explode much more violently and completely than those that end up as dwarf stars. They produce black holes whose only features are vestigial remains of the original star such as mass and electromagnetic signature. They are regions of infinite gravity from where even light cannot escape.

The Schwarzschild radius is the size that a given object would have to be for its matter to be so dense that the escapes velocity would be equal to light speed. Beyond that density, light is no longer visible from that (former) star. The sun would reach that point once it radius approached 3 km.

Black holes are most likely to be found at the centers of galaxies.