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Astronomy 110 Exam 2

Terms in this set (32)

Understand the concept of EM spectrum and similarities and differences between types of radiation.
Electromagnetic waves are alike because they travel at the same speed. They are different because they have different wavelengths and frequencies. List in order of increasing frequency the kinds of waves that make up the electromagnetic spectrum.
understand the concept of a blackbody and its relation to color and temperature.
If you think in terms of visible light, the hotter the blackbody, the bluer the wavelength of its peak emission. When the object becomes a little hotter, it appears dull red. As its temperature increases further it becomes bright red, orange, yellow, white, and ultimately blue-white.
Recognize the difference between continuous emission and absorption spectra.
The main difference between emission and absorption spectra is that an emission spectrum has different coloured lines in the spectrum, whereas an absorption spectrum has dark-coloured lines in the spectrum.
Describe the information gleaned from starlight that has been separated by color.
The information comes to us at the speed of light! The light of stars is produced by atoms and molecules that encode, in the starlight itself, key science information about their chemical composition, temperature, pressure, and velocity
Name the three components to measuring radiation.
Three common measurements of radiation are the amount of radioactivity, ambient radiation levels, and radiation dose.
Understand the difference between light-gathering power and resolving power.
The light-gathering power of a telescope is determined by the diameter of its aperture, or opening—that is, by the area of its largest or primary lens or mirror.

The resolving power of an objective lens is measured by its ability to differentiate two lines or points in an object. The greater the resolving power, the smaller the minimum distance between two lines or points that can still be distinguished.
Discuss the ways in which the atmosphere is not helpful to astronomy, and ways around it.
Some of the problems include: Weather - It is almost impossible to do astronomy through thick cloud! Light Pollution - Modern towns and cities have lots of lights on at night. ... Transmission - Many kinds of light, especially those that we cannot see with our eyes, do not get through the atmosphere at all.
Compare and contrast reflecting and refracting telescopes.
The difference between Reflecting and Refracting Telescopes is that a reflecting telescope has a single or a combination of curved mirrors in order to reflect the light rays and form an image. On the other hand, an refracting telescope has a lens as its objective lens to form an image.
Explain why the largest telescope are reflecting and not refracting.
For technical reasons, the largest optical telescopes are reflecting rather than refracting telescopes: it is easier to build and support large mirrors of high optical quality than large lenses.
understand the axes used on an HR diagram(and be prepared to draw one!)
These diagrams, called the Hertzsprung-Russell or HR diagrams, plot luminosity in solar units on the Y axis and stellar temperature on the X axis, as shown below.
Describe how stars are classified, what they are made of, and how we know this.
Stars are classified by their spectra (the elements that they absorb) and their temperature. ... In order of decreasing temperature, O, B, A, F, G, K, and M. O and B stars are uncommon but very bright; M stars are common but dim.. An easy mnemonic for remembering these is: "Oh be a fine guy/girl, kiss me."
Described two methods for determining stellar distances.
Astronomers estimate the distance of nearby objects in space by using a method called stellar parallax, or trigonometric parallax.
Given two stars, place them on an HR diagram and compare size, luminosity, temperature, color, and age.
The model stars with the largest masses are the hottest and most luminous, and they are located at the upper left of the diagram. The least-massive model stars are the coolest and least luminous, and they are placed at the lower right of the plot.
Know the major types of stars and their location on an HR diagram.
The main sequence stretching from the upper left (hot, luminous stars) to the bottom right (cool, faint stars) dominates the HR diagram. It is here that stars spend about 90% of their lives burning hydrogen into helium in their cores.
Explain the difference between a star's luminosity and its apparent brightness.
Luminosity is the rate at which a star radiates energy into space. Apparent brightness is the rate at which a star's radiated energy reaches an observer on Earth.
Discuss how stars are born and live out the majority of their lives
Summary. Stars are born in giant, cold clouds of gas and dust called nebulae. A star is born once it becomes hot enough for fusion reactions to take place at its core. Stars spend most of their lives as main sequence stars fusing hydrogen to helium in their centres.
Describe how clusters of stars allow us to better understand stellar evolution.
Star clusters are particularly important because they allow astronomers to check models of stellar evolution and the ages of stars. ... They therefore share the same initial metallicity so any effect of this on stellar evolution is effectively the same for the members of the cluster
Discuss the three types of star deaths and what determines the ultimate fate of a star.
Low-Mass Stars (0.5 solar mass or less)
Medium-Mass Stars (0.5 solar mass to 3.0 solar mass)
Massive Stars (3.0 solar masses or larger)
Understand the difference between type 1 and 2 supernovae.
A type I supernova occurs in closed binary systems where two average stars orbit around each other quite closely. ... A type II supernova occurs in larger stars of around 10 solar masses. After it leaves the main sequence it starts fusing increasingly heavy elements in shells around the core
What evidence is used to 'see' black holes?
The best evidence of stellar-mass black holes comes from binary star systems in which (1) one star of the pair is not visible, (2) the flickering X-ray emission is characteristic of an accretion disk around a compact object, and (3) the orbit and characteristics of the visible star indicate that the mass of its invisible companion is greater than 3 MSun. A number of systems with these characteristics have been found. Black holes with masses of millions to billions of solar masses are found in the centers of large galaxies.
Explain the relationship between the event horizon and escape velocity.
At the event horizon, the escape velocity is equal to the speed of light. Since general relativity states that nothing can travel faster than the speed of light, nothing inside the event horizon can ever cross the boundary and escape beyond it, including light.
Discuss three pieces of evidence that support the theory of relativity.
In 1919 observation of a solar eclipse confirmed Einstein's prediction that light is bent in the presence of mass. This experimental support for his general theory of relativity garnered him instant worldwide acclaim.
Describe the three attributes a hypothesis must possess.
A good Hypothesis must possess the following characteristics - 1.It is never formulated in the form of a question. 2.It should be empirically testable, whether it is right or wrong. 3.It should be specific and precise. 4.It should specify variables between which the relationship is to be established.
The theory of relativity says what about space and time?
General relativity is physicist Albert Einstein's understanding of how gravity affects the fabric of space-time. ... Special relativity argued that space and time are inextricably connected, but that theory didn't acknowledge the existence of gravity
Be prepared to identify the 4 different galaxy types and the age range of stars each contains.
Edwin Hubble invented a classification of galaxies and grouped them into four classes: spirals, barred spirals, ellipticals and irregulars. He classified spiral and barred spiral galaxies further according to the size of their central bulge and the texture of their arms.
Described what type of galaxy do we live in and how we know this.
The Milky Way is a large barred spiral galaxy. All the stars we see in the night sky are in our own Milky Way Galaxy.
Explain how we know where the center of our galaxy is located.
To observe the galactic center you can look at longer wavelengths (as in the infrared photo immediately below, which covers the same area of the sky as the visible photo). In the infrared photo, the dimming by dust is much less, and we can see that the center of the galaxy is actually quite bright.
Understand red-shift and how it is related to the recessional velocity of galaxies.
In other words, the farther they are the faster they are moving away from Earth. The velocity of the galaxies has been determined by their redshift, a shift of the light they emit toward the red end of the visible spectrum.
Discuss two methods used to determine distance to other galaxies.
Astronomers estimate the distance of nearby objects in space by using a method called stellar parallax, or trigonometric parallax.
Provide and explain evidence that the universe is expanding
Astronomers observe a regular progression of galaxies which are expanding at progressively higher velocities as they measure galaxies at increasing distances.
Describe what we can learn about the university by running Hubble's law in reverse and explain what other evidence supports the big bang.
Hubble's law, which says simply that a galaxy's velocity (or as is sometimes plotted, its redshift) is directly proportional to its distance, also tells us something important about the state of the universe. If the universe is static and unchanging, there should be no correlation between distance and velocity.
Draw and label a diagram showing Hubble's constant and describe how we infer the age of the universe from this diagram.
Draw a straight line that best fits the points on the graph; remember that this line must pass through the origin (the 0,0 point). Measure the slope of this line (rise/run), this is your value of the Hubble constant, in the units of km/sec/Mpc.
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