Professor Questions Unit 6

Professor Questions Unit 6

1 . Discuss how astronomers compare the stars

There may be several terms astronomists use to compare stars , including luminosity , flux , energy flux , apparent magnitude and absolute magnitude

Luminosity is the measured in Watts

Energy flux is the flow of energy out from a particular surface area and is measured in Watts per meter square

Observed flux - As the radius of the circle placed around the radiating object increases , the flow of energy per meter square would decrease The observed flux would be higher if the radius

of the circle is less (inverse square law

Apparent Magnitude is the amount of light that is received from a particular star . It is determined using the luminosity of the star and the distance from us . The apparent magnitude would be low for a brighter object

Absolute magnitude is the amount of light that is received from a particular object when the object is placed at a distance of 10 par secs (A B 's Astronomy Lab , University of Columbia , 2002

2 . From nebulae , stars are formed . Discuss the factors that affect the gestation time for the birth of protostars

The nebulae from which clouds form are nothing but clouds of dust and gas . They slowly begin to contract to begin the process of star formation . The mass is known as the `protostars ' and it would continue to condense and slowly heat up . Once it reaches a critical mass phase the nuclear fusion reaction takes place hydrogen atoms fuse together to form helium , two protons and tremendous amounts of energy . Once this phase begins , the star is born

Factors that affect gestation time for the birth of protostars

Gravity of the passing star (external energy to help star formation

Shockwave from a nearby supernova (external energy to help star formation

Heating by contraction (Giant molecular clouds need to contract to heat up and begin the thermonuclear processes

Magnetic fields available (helps in contraction

Rotation or angular momentum of the protostars

Size of the star (smaller stars live longer than larger stars as they take longer to burn their fuel (Sea Sky , 2008 UNT , 2008

3 . Discuss how a stars life affected by its `fuel`

Once the protostar gets heated up , nuclear fusion reaction begins (thermonuclear processes , and the star now enters its stable phase The star would be combating gravitational collapse by fusing atoms together and forming energy . The star 's life span depends on how much of matter it actually contains . The process of nuclear fusion in the stars would involve conversion of hydrogen to helium , helium to carbon until iron is formed . Once iron is formed , the energy required to fuse iron is much higher and hence the reaction stops . Larger stars tend to use up larger amounts of fuel compared to smaller stars , and hence would live much shorter . Several large stars in the universe live for about a few hundreds of thousands of years . As smaller stars would be spending their fuel much more slowly , they...