Show:
Telescopes
Characteristics of Stars
Lives of Stars
Star Systems & Galaxies
The Expanding Universe
100
Why are most telescopes located on mountaintops?
Optical telescopes gather and focus visible light. When those light waves hit the molecules of the atmosphere, they cause the resulting image to be blurry. By placing optical telescopes above as much of the atmosphere as possible, it reduces the interference of the atmosphere, allowing a clearer image.
100
What two factors determine the absolute brightness of a star?
Size and temperature (NOT distance)
100
When does a star become a star?
A star is born when the contracting gas and dust from a nebula become so dense and hot that nuclear fusion starts.
100
Distinguish between a star system and a star cluster.
A star system is a grouping of 2 or more stars. A star cluster is a large grouping of several thousand (or more) stars.
100
Identify and summarize the leading theories on how the universe came into existence, and how it is believed that it will end.
The leading theory for how the universe began is the big bang. It states that the universe began from a tiny point of energy which expanded to create our universe. The leading theory on how the universe will end is the INFINITE, EXPANDING UNIVERSE. That is, according to current evidence, we expect the universe to continue expanding forever. (?!)
200
Reflecting telescopes use _____________ while refracting telescopes use _______________.
mirrors/lenses
200
Name three of the five characteristics used to classify stars.
Any three of the following: color, brightness, temperature, size, and composition (what it's made of).
200
Star A have 10 solar masses, while Star B has 5 solar masses. Which star would you expect to live longer?
Mass is inversely proportional to lifetime, therefore as the mass of a star increases, its lifetime decreases. In this case, Star B would live longer, because it has a lesser mass.
200
Distinguish between binary, eclipsing binary, and trinary star systems.
Binary star systems have 2 stars. They vary in terms of the types and sizes of those stars. Eclipsing binary stars are made up of two stars, but periodically one star moves in front of and blocks the light from the other star. This causes the light of the brighter, larger star to be dimmed for a period of time. The smaller, dimmer star then moves out of the way, and the large, bright star returns to its normal apparent brightness. This process repeats again and again, based on the orbits of the stars involved in the eclipsing binary system. A trinary star system is a group of three stars, all in a stable gravitational relationship with each other.
200
Distinguish between dark matter and dark energy.
Dark matter is anything in the universe which does not give off light. Planets and dead stars are examples. Dark energy is the mysterious force which is believed to be causing the accelerated expansion of the universe. It is not presently proven; it is only a hypothesis at this moment.
300
Distinguish between the electromagnetic spectrum and the visible light spectrum.
The electromagnetic (EM) spectrum is composed of all of the different types of electromagnetic radiation, such as microwaves, radiowaves, visible light, etc. The visible light spectrum refers to ONLY the forms of EM that we can see: ROYGBV.
300
A scientist is observing a trinary star system. One of the stars is blue, another is yellow, and the third is red. Order the stars from coolest to hottest.
Generally speaking, stars proceed from coolest to hottest following the visible light spectrum, ROYGBV. Therefore, red would be coolest, yellow next, and blue hottest.
300
Describe the life cycle of a small mass star.
All stars are born from nebulae, and small mass stars are no different. Once the star has formed, it is called a Main Sequence star. After a certain period of time, it will burn through all of its Hydrogen, and expand to form a Giant star. Once it burns through all heavier elements (Helium, etc.) all nuclear fusion will cease. At this point, the gravity of the star will cause the core to collapse, while the star's atmosphere drifts away, forming a planetary nebula. Once the star's atmosphere has drifted away, all that is left is the white hot core, called a white dwarf. Finally, once the white dwarf has cooled completely, it is a cold, dark black dwarf star.
300
An astronomer is observing a particular star in the night sky. Every once in a while, she notices that the star demonstrates a slight back and forth motion. How would you explain this wobble?
Even though it may not be directly visible, there may be another object present. In order for an object to cause a gravitational disturbance to something as large as a star, it must itself be very large. Only a planet or another dark object (e.g., black dwarf, black hole) would have sufficient gravity to cause this to occur.
300
Name two pieces of evidence which support the big bang.
The fact that the universe is currently expanding (and has been as long as we've been observing it) hints at an earlier time when it was smaller. If we extend that thinking logically back, we can imagine a moment when the universe was infinitesimally small. This is the moment of the big bang. A second piece of evidence is the cosmic background radiation, which we believe is the leftover thermal (heat) energy of the original big bang explosion. As the heat signature of the universe is still present, we can imagine that it was very, very hot.
400
Put the following forms of electromagnetic waves in order from longest wavelength (lowest energy) to shortest wavelength (highest energy): visible light, radiowaves, ultraviolet, gamma, microwaves, infrared, x-rays.
From longest wavelength (lowest energy) to shortest wavelength (highest energy): radiowaves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma waves.
400
Star A is 200 l-y from earth, while Star B is 40 l-y from earth. Which star would you expect to have the greater parallax? Explain.
Parallax is the apparent change in position of an object when it is viewed from different points of view. An object's parallax is inversely proportional to its distance: in other words, when an object is closer, it has a greater parallax, and when an object is farther away, it has a smaller parallax. Therefore, Star B, which is closer to earth, would demonstrate a greater parallax.
400
Describe the life cycle of a large mass star.
All stars are born from nebulae, and large mass stars are no different. Once the star has formed, it is called a Main Sequence star. After a certain period of time, it will burn through all of its Hydrogen, and expand to form a Supergiant star. Once it burns through all heavier elements (Helium, etc.) all nuclear fusion will cease. At this point, the gravity of the star will cause the core to collapse, but at some point the nuclear forces of the atoms making up the star resist the collapse of gravity, and explode in a Supernova. Following this explosion, gravity once again wins the day, and the star collapses to form one of the two densest objects in the universe. If the star is between 10-20 solar masses, it will form a neutron star. If the star is greater than 20 solar masses, it will form a black hole.
400
Identify the two different types of star clusters, and discuss their levels of new star formation.
Open clusters are loosely organized collections of a few thousand stars. Open clusters still have much gas and dust, so they are active centers of new star formation. Globular clusters are densely packed groupings of older stars. Since there is very little gas and dust, very little new star formation occurs in globular clusters.
400
The Andromeda Galaxy is 2.5 million l-y away, while the Sombrero Galaxy is 30 l-y away. According to Hubble's Law, which galaxy would you expect to be moving away from us at a faster rate? Explain.
Hubble's Law states that the farther a galaxy is away from us, the faster it will be moving away from us (farther, faster). Conversely, the closer a galaxy is to us, the slower it will be moving away from us. Since the Sombrero Galaxy is farther away, it will be moving away from us at a faster rate.
500
The center of the Milky Way Galaxy is a dense cloud of gas and dust. What type of telescope would you use to try to gather information about the center of the Milky Way? Defend your answer.
Generally speaking, the longer the wavelength of EM radiation, the more interference it will experience due to gas, dust, and other obstructions. Therefore, the most effective telescopes would likely be telescopes which use short wavelength EM energies, such as ultraviolet or X-ray radiation.
500
Use the H-R Diagram to answer the following: a) identify a star that is both hot and bright b) identify a star that is hot, but dim c) discuss the star Procyon in terms of color, temperature, and brightness
a) Answers will vary (AWV), but may include: Zeta Eridani, Spica, or Rigel. b) Sirius B is one of the few hot, dim stars c) Procyon is approximately 6000 degrees C, yellow in color, and moderate in brightness.
500
Betelguese is a star with approximately 12 solar masses. Describe Betelguese's life cycle starting from its birth inside of a nebula.
As a high mass star, Betelguese must have been formed from a large cloud of gas and dust inside the nebula. It would then become a main sequence star. Since it is a high mass star, it would quickly burn through its fuel and become a supergiant (which it has). It will then explode in a supernova, and since it has 12 solar masses, end its life as a neutron star.
500
Identify the three different types of galaxies. Describe them in terms of their shapes, as well as their level of new star formation.
The three types of galaxies are irregular, spiral, and elliptical galaxies. Irregular galaxies are large, irregularly shaped collections of gas and dust. Since there is so much gas and dust, they are very active centers of new star formation. Spiral galaxies are pinwheel shaped galaxies with a dense central core, and arms that extend out spirally from the center. The center is a dense concentration of older stars, and little new star formation occurs there. However, the arms still contain much gas and dust, so new star formation can occur here. Finally, elliptical galaxies are roughly oval shaped. They are dense concentrations of thousands (or more) stars. There is virtually no gas or dust left in an elliptical galaxy, so there is little new star formation.
500
Planet X is small and hot, while planet Y is large and cool. Predict the atmospheres which will develop on these two distinct planets. Explain your reasoning.
The two factors which contribute to the formation of an atmosphere are temperature and gravity. Hotter temperatures and smaller mass (less gravity) cause thinner atmospheres, while cooler temperatures and larger mass (greater gravity) cause thicker atmospheres. Since Planet X is small and hot, it will have a thin atmosphere. Since Planet Y is large and cool, it will have a thick atmosphere.