ASTR 315 Quizzes Q/A

College Park is at a latitude of 39 deg N. Which one of the following could be the HArise/set for a star with a declination of 30 deg when seen from College Park? +/- 2 h +/- 5 h You Answered +/- 6 h Correct Answer +/- 8 h

+/- 8 h

What is the right ascension of the Sun on the day of the vernal equinox? 12 h 6 h 3 h Correct! 0 h

0 h

What is the possible range of values for right ascension that a star could have? -90 to +90 degrees Correct! 0 to 24 hours 0 to 12 hours 0 to 180 degrees

0 to 24 hours

Below are the wavelengths of different light waves. Which one has the MOST radiative energy? 3 x 10^-10 m You Answered 6 x 10^-7 m 9 x 10^-5 m Correct Answer 1 x 10^-14 m

1 x 10^-14 m

What will the local sidereal time be at 6pm on October 7? 7 h Correct! 19 h 22 h 3 h

19 h

What will the local sidereal time be at noon on January 21? 13 h Correct Answer 20 h You Answered 4 h 1 h

20 h

At 3 am on the day of the autumnal equinox, what is the right ascension of a star on the celestial equator that is on the western horizon (setting)? 9 h 15 h 3 h Correct! 21 h

21 h

At 3am on the day of the autumnal equinox, what is the right ascension of a star on the meridian? You Answered 15 h 21 h Correct Answer 3 h 12 h

3 h

If a light wave's wavelength is 1 m, which one of the following is its frequency? 0.3 x 10^-7 s 2 x 10^4 Hz 3 x 10^8 m/s Correct! 3 x 10^8 Hz

3 x 10^8 Hz

What is the right ascension of the Sun on the summer solstice (June 21)? 20 h Correct! 6 h 12 h 18 h

6 h

At 9pm on the day of the vernal equinox, what is the right ascension of a star on the meridian? You Answered 0 h 15 h 12 h Correct Answer 9 h

9 h

About how old is the solar system? About 13.7 billion years old About 6000 years old About 2 billion years old Correct! About 4.5 billion years old

About 4.5 billion years old

Which one of these stars has the LARGEST apparent brightness? Achernar, apparent magnitude 0.51 Megrez, apparent magnitude 3.3 Polaris, apparent magnitude 2.0 Zubenelakrab, apparent magnitude 3.9

Achernar, apparent magnitude 0.51

The latitude of College Park is 39 deg N. Which one of these stars could NOT be seen from College Park at some time during the year? Vega, DEC 38 deg, RA 19 h Fomalhaut, DEC -30 deg, RA 23 h Kochab, DEC 74 deg, RA 15 h Mintaka, DEC 0 deg, RA 6 h Correct! Acrux, DEC -63 deg, RA 12 h

Acrux, DEC -63 deg, RA 12 h

Which of the following pieces of information do we need to know in order to figure out when a star will rise and set for a night we plan to observe? (choose all that apply) Correct! The latitude we plan to observe from Correct! The right ascension of the star Correct! The date we plan to observe Correct! The declination of the star

All the above

What is 1 AU? The distance to the nearest star other than the Sun Correct Answer Approximately half of the diameter of the Earth's orbit around the Sun You Answered The average distance between the Earth and the Moon The Sun's diameter

Approximately half of the diameter of the Earth's orbit around the Sun

What will likely happen if a pixel on a CCD becomes saturated while an image is being taken? The CCD will short-circuit and burn out. The pixel will overload and appear completely black in the image. The pixel will stop absorbing additional light. Correct! Charge from the saturated pixel will move into adjoining pixels.

Charge from the saturated pixel will move into adjoining pixels.

After you take the first image of the asteroid and look at the preview of it, what should you do? Take another image immediately. Focus the telescope. Correct! Compare it to the finder chart to make sure the telescope is pointing at the right area of the sky. Save the image so it can be analyzed in class later.

Compare it to the finder chart to make sure the telescope is pointing at the right area of the sky.

According to the diversity article, which one of the following types of group conflict is actually useful to have? You Answered Team values/goals conflict Correct Answer Conflict about the best course of action for the group project Interpersonal conflict between team members

Conflict about the best course of action for the group project

What are the typical units of right ascension? Degrees and hours Degrees, arcminutes, and arcseconds Years, months, and days

Degrees, arcminutes, and arcseconds

Which of these characteristics affects an asteroid's mass? (choose all that apply) Correct! Diameter Correct! Porosity Correct! What it is made of You Answered Distance from Earth

Diameter Porosity What it is made of

Asteroid Iris is 2.4 AU from the Sun on average. Asteroid Flora is 2.2 AU from the Sun on average. Which asteroid has BRIGHTER sunlight hitting it? Correct! Flora Iris They both receive sunlight of the same brightness. It depends on each asteroid's albedo.

Flora

The apparent magnitude of Fomalhaut is 1.2. The apparent magnitude of Merak is 2.4. Which one of the following best describes how their apparent brightnesses compare? Merak is 2.5 times brighter than Fomalhaut. Correct! Fomalhaut is 2.5 times brighter than Merak. Merak is 0.5 times brighter than Fomalhaut. Fomalhaut is 1.2 times brighter than Merak.

Fomalhaut is 2.5 times brighter than Merak

The asteroid Vesta's apparent magnitude ranges from 5.1 to 8.5. Which one of the following is the most likely reason its apparent magnitude changes? It sometimes passes behind clouds of dust within the solar system. It has very different materials on each side of it that reflect different amounts of light. Correct! Fomalhaut is 2.5 times brighter than Merak Its diameter is gradually increasing and decreasing.

Fomalhaut is 2.5 times brighter than Merak

Which of these things affect how bright an asteroid appears to us? (choose all that apply) Correct! How far it is from the Earth Correct! How reflective it is Correct! How far it is from the Sun How fast it rotates Correct! How big it is How dense it is

How far it is from the Earth How reflective it is How far it is from the Sun How big it is

Where are most asteroids in the solar system located? Correct! In between the orbits of Mars and Jupiter Inside the orbit of Mercury Outside the orbit of Neptune In between the orbits of the Earth and Mars

In between the orbits of Mars and Jupiter

How is one new measurement about an asteroid useful? Correct! It gives us information about whether that asteroid formed within our solar system or came from outside the solar system. One measurement is not useful unless many more measurements are made of the same asteroid. It can tell us if that particular asteroid has any chance of impacting the Earth.

It gives us information about whether that asteroid formed within our solar system or came from outside the solar system.

Which of the following correctly describe the celestial equator? (choose all that apply) You Answered When we imagine where it is in the sky, it runs from the north to south celestial poles. Correct! Its declination is zero degrees. Correct! It is the extension of the Earth's equator into space. The celestial equator can only be seen in the sky from the Earth's equator.

Its declination is zero degrees. It is the extension of the Earth's equator into space.

Which one of the following is NOT a typical characteristic of a jovian planet? The jovian planets have much larger orbits around the Sun than the terrestrial planets. Jovian planets have much larger diameters than the terrestrial planets. Jovian planets have much larger masses than the terrestrial planets. Correct! Jovian planets have much higher average densities than the terrestrial planets.

Jovian planets have much higher average densities than the terrestrial planets.

Which one of the following objects would appear the LARGEST in the sky? (Don't worry about whether your eye can actually resolve these objects; imagine that you have super vision that can resolve anything.) Pluto, with an angular diameter of 0.081 arcseconds You Answered The star Proxima Centauri, with an angular diameter of 0.001 arcseconds. The asteroid Ceres, with an angular diameter of 0.48 arcseconds Correct Answer Jupiter's moon Ganymede, with an angular diameter of 1.4 arcseconds

Jupiter's moon Ganymede, with an angular diameter of 1.4 arcseconds

The latitude of College Park is 39 deg N. Which one of these stars is circumpolar when seen from College Park? Acrux, DEC -63 deg, RA 12 h You Answered Mintaka, DEC 0 deg, RA 6 h Correct Answer Kochab, DEC 74 deg, RA 15 h Fomalhaut, DEC -30 deg, RA 23 h Vega, DEC 38 deg, RA 19 h

Kochab, DEC 74 deg, RA 15 h

What is light pollution? Small amounts of light emitted by smog, which is only visible at night. Light from the moon that is accidentally captured by digital cameras observing other astronomical objects. Correct! Light from artificial sources that scatters through the sky at night, making it bright. The distortion in images caused by stars' twinkling.

Light from artificial sources that scatters through the sky at night, making it bright.

Which of the following planets are terrestrial? (choose all that apply) Jupiter Correct! Mars Correct! Venus Correct! Earth Neptune Saturn Correct! Mercury Uranus

Mars Venus Earth Mercury

Which asteroids are the ones most likely to impact the Earth? The youngest asteroids The largest asteroids The most massive asteroids Correct! Near-Earth asteroids

Near- Earth Asteroids

If a star is above the horizon and halfway between when it rises and sets, what special location must it be at in the sky? Correct! On the meridian At the north celestial pole At the zenith On the celestial equator

On the meridian

Approximately where in the Milky Way galaxy is the solar system located? In the center of the galaxy At the edge of the galaxy Correct! Partway between the center and the edge of the galaxy Astronomers are not sure.

Partway between the center and the edge of the galaxy

What two things do you need to do BEFORE you begin a session of observing? (choose two) Check the weather at your observing location Correct! Print a finder chart for your asteroid Correct! Get an ephemeris for your asteroid Reserve the telescope time

Print a finder chart for your asteroid Get an ephemeris for your asteroid

When you start each series of 3 images, what should you do? You Answered Focus the telescope. Correct! Record the weather conditions. You Answered Point the telescope to a slightly different part of the sky. Correct! Check and record the exposure time and filter used. Increase the exposure time.

Record the weather conditions. Check and record the exposure time and filter used.

What should you do if you login at the beginning of an observing session and find out it is cloudy at your observing location? Logout of the telescope system and inform Dr. Hayes-Gehrke of the lost night of observing. Correct! Remain logged in and monitor the weather for at least three hours to see if it improves. Tell the observatory roof to open and take images through the clouds. Contact the support staff at the observatory.

Remain logged in and monitor the weather for at least three hours to see if it improves.

What are asteroids made of? Correct! Rocks and metals Ices Astronomers do not know. Gases

Rocks and metals

Which of the following objects are part of our solar system? (choose all that apply) Correct! The Sun Correct! Comet Halley Correct! The Earth Correct! Jupiter You Answered Polaris, the North Star Correct! Pluto Correct! Mars's moon Phobos You Answered The star Betelgeuse Correct! The asteroid Vesta Correct! The Earth's moon You Answered The Andromeda Galaxy

Sun Comet Halley The Earth Jupiter Pluto Mars's moon Phobos The Asteroid Vesta The Earth's moon The Andromeda Galaxy

From which webpage can you monitor what the telescope is doing after you give it a command? Single Image Run Image Series Deep Sky Catalog Correct! System Status

System Status

Which two telescopes will be used by the class? (choose two) Correct! T21 in Mayhill, New Mexico T18 in Nerpio, Spain Correct! T7 in Nerpio, Spain T9 in Siding Spring, Australia

T21 in Mayhill, New Mexico

Imagine that a CCD is used to take an image of a star for 30 seconds. Then the same CCD is used to take a new image of the same star for 60 seconds. How does the number of electrons trapped in each pixel compare in the two images? The 30-second image has fewer electrons than the 60-second image, but we really can't tell how many fewer. The 30-second image has one-quarter as many electrons as the 60-second image. You Answered The 30-second image has twice as many electrons as the 60-second image. Correct Answer The 30-second image has half as many electrons as the 60-second image.

The 30-second image has half as many electrons as the 60-second image.

As mentioned in a previous question, the Discovery Channel Telescope has a primary mirror diameter of 4.3 m. The telescope we will use for the class has a primary mirror diameter of 0.43 m. If these telescopes observe the same wavelength of light, how do their angular resolutions compare? Correct Answer The Discovery Channel Telescope's angular resolution is 10 times smaller. The Discovery Channel Telescope's angular resolution is 10 times larger. You Answered The Discovery Channel Telescope's angular resolution is 100 times smaller. The Discovery Channel Telescope's angular resolution is 250,000 time smaller.

The Discovery Channel Telescope's angular resolution is 10 times smaller.

Why is local sidereal time different from normal (solar) time? The stars are moving through the galaxy. It is caused by parallax. The stars are getting farther away from the solar system. Correct! The Earth orbits the Sun, so our point of view of the stars is changing.

The Earth orbits the Sun, so our point of view of the stars is changing.

What is the name given to the amount of energy the Sun emits per second in all directions? Correct! The Sun's luminosity The Sun's energy The Sun's apparent brightness The Sun's albedo The Sun's magnitude

The Sun's luminosity

What defines the zero point of right ascension? Correct! The Sun's right ascension at noon on the vernal equinox The setting point of the Sun on the autumnal equinox The Sun's longitude at midnight on the summer solstice The average location of the Sun in right ascension when measured throughout the year

The Sun's right ascension at noon on the vernal equinox

How does an astronomer create a color CCD image? The astronomer uses the time information on the CCD to determine which photons arrived first and last, since the first photons to arrive would be higher frequency. The astronomer takes multiple images, each with CCDs that detect specific wavelengths of light, and then combines them. The astronomer analyzes the ADUs in each pixel to determine which ones were caused by which wavelengths of light and uses that information to color-code each pixel. Correct! The astronomer takes multiple images, each through a different colored filter, and then combines them.

The astronomer takes multiple images, each through a different colored filter, and then combines them.

What is the Local Group? A small number of asteroids that orbit rather closely to the Earth in the solar system. Correct! The group of galaxies of which the Milky Way is a member. A group of galaxies that the Milky Way is moving toward. The stars that are closest to the Sun within the Milky Way galaxy.

The group of galaxies of which the Milky Way is a member.

Why doesn't a telescope focus all of the light it gathers into a tiny pinpoint? The objects that a telescope observes are not tiny pinpoints, but have finite sizes, so their telescopic images also have finite sizes. Correct Answer The light waves reflecting off of the telescope mirror interfere with each other, making a light pattern of a specific size for each telescope. You Answered The Earth's atmosphere disperses the light coming from astronomical objects, preventing the telescope from making such a perfect image. The background light from other objects, such as the Moon or artificial lights, interferes with the light waves from the object of interest.

The light waves reflecting off of the telescope mirror interfere with each other, making a light pattern of a specific size for each telescope.

The University of Maryland Astronomy Department has joined a partnership to use the Discovery Channel Telescope, which has a primary mirror diameter of 4.3 m. The telescope we will be using for the ASTR 315 class project has a primary mirror diameter of 0.43 m. How do the light-gathering powers of these telescopes compare? The light-gathering power of the Discovery Channel Telescope is 2 times larger than the class telescope. The light-gathering power of the Discovery Channel Telescope is 3.5 times larger than the class telescope. The light-gathering power of the Discovery Channel Telescope is 10 times larger than the class telescope. Correct! The light-gathering power of the Discovery Channel Telescope is 100 times larger than the class telescope.

The light-gathering power of the Discovery Channel Telescope is 100 times larger than the class telescope.

Why do astronomers prefer to observe when the moon is not above the horizon? The Moon tends to attract clouds in the sky, which affects measurements of astronomical objects. Correct! The moonlight lights up the sky, making it harder to observe faint objects. The Moon's gravity distorts the light from objects in the sky near the Moon, affecting the accuracy of those observations. The Moon blocks our view of some objects in the sky since it is close to the Earth.

The moonlight lights up the sky, making it harder to observe faint objects.

A computer displays a CCD image with colors dictated by the numerical value of each pixel. What is the numerical value of each pixel? The angular size of the pixel Correct! The number of ADUs a pixel is assigned, based on the charge it accumulated The number of photons that a pixel absorbed The Airy disk of the pixel

The number of ADUs a pixel is assigned, based on the charge it accumulated

Imagine that you look at an impact crater on the Moon and an impact crater on Mercury. Both impact craters have the same angular diameter. Which impact crater has the LARGER physical diameter? The one on the Moon You Answered It cannot be determined from this information. Correct Answer The one on Mercury They both have the same physical diameter.

The one on Mercury

What is the current local sidereal time at any location? Correct! The right ascension of a star on the meridian at that location. The declination of a star on the celestial equator at that time. The right ascension of the Sun at that time and location. The hour angle of the Sun at that time and location.

The right ascension of a star on the meridian at that location.

If an astronomer says that a star has an hour angle of 4 h, what can we deduce? (choose all that apply) Correct! The star crossed the meridian 4 hours ago. You Answered The star is circumpolar. The star has a positive declination.

The star crossed the meridian 4 hours ago.

Suppose a telescope's angular resolution is calculated to be 0.3 arcseconds, based on its primary mirror diameter and the type of light it observes. The telescope's light is projected onto a CCD whose pixels each detect light from 0.5 arcsec x 0.5 arcsec of the sky. The image of the star is centered on one pixel. What appearance will the star have in the CCD image? (We are ignoring the effects of the atmosphere.) You Answered The star will appear to be a round, bright spot made by a cluster of several pixels, with the brightest one in the center. The star will appear as a round, bright spot in the center of one pixel. Correct Answer The star will appear to be square: one pixel in size. The star will not appear in the image at all.

The star will appear to be square: one pixel in size.

Asteroid Egeria is 2.6 AU away from the Sun on average. Jupiter is 5.2 AU away from the Sun on average. How does the brightness of the sunlight hitting Jupiter compare to that hitting Egeria? The sunlight hitting Jupiter is 1/6 as bright. Correct Answer The sunlight hitting Jupiter is 1/4 as bright. You Answered The sunlight hitting Jupiter is 2 times brighter. The sunlight hitting Jupiter is 1/2 as bright.

The sunlight hitting Jupiter is 1/6 as bright

Which of the following types of light moves the slowest? X-rays, since they have the shortest wavelength. Radio waves, since sound moves slower than light. Visible, since most of the Sun's light is of this form. Correct! They all move the same speed. Gamma rays, since they have the highest frequency.

They all move at the same speed

Which one of these characteristics of CCDs makes them especially useful for astronomers? Correct! They detect much fainter light than the eye or other sensors do. They are expensive. They are sensitive to the heat in their surroundings. They can be attached to telescopes.

They detect much fainter light than the eye or other sensors do.

Why do we see visible light coming from asteroids? They reflect light from the billions of stars in our galaxy. They reflect the light sent out from astronomers' telescopes. They are glowing in visible light. Correct! They reflect sunlight.

They reflect sunlight

If something goes wrong while you're observing and you can't figure out what the problem is what should you do? Stop using the telescope and logout. Do nothing, wait, and see if the problem resolves itself. Correct! Use the "page on-duty engineer" button on itelescope.net. Call Dr. Hayes-Gehrke.

Use the "page on-duty engineer" button on itelescope.net. Call Dr. Hayes-Gehrke.

Which one of these telescopes would have the most light-gathering power? Correct! VLT Antu, primary mirror diameter 8.2 m Hale Telescope, primary mirror diameter 5.1 m MMT, primary mirror diameter 6.5 m Discovery Channel Telescope, primary mirror diameter 4.3 m

VLT Antu, primary mirror diameter 8.2 m

The four images below show an asteroid (circled) moving compared to the stars in the image. Why do the asteroid and many of the stars appear about the same size in the images?eso0711a.jpg Correct! We are seeing the Airy disks created by the light from the stars and the asteroid, not their true sizes. The asteroid's relatively rapid rotation distorts its shape in images, making it appear as large as the stars. Because the stars are so much farther away than the asteroid, they appear to be about the same size. The asteroid is emitting a lot more light than the stars.

We are seeing the Airy disks created by the light from the stars and the asteroid, not their true sizes.

Which of the following are valid reasons for studying asteroids? (choose all that apply) Correct! We will increase the overall amount of humanity's knowledge. Correct! We will learn about the solar system's formation. Correct! We will be better prepared if an asteroid is going to impact the Earth. You Answered We will learn about life in other solar systems.

We will increase the overall amount of humanity's knowledge. We will learn about the solar system's formation. We will be better prepared if an asteroid is going to impact the Earth.

Which of the following types of light has the most energy per photon? Ultraviolet Violet visible light Correct Answer X-rays Red visible light You Answered Radio waves

X-rays

Using the information from the previous question, is it ever possible to see Vesta in the sky by eye, assuming we're in the right location on the Earth? Correct! Yes, when Vesta is at its brightest, it is possible to see by eye. No, because no matter how bright Vesta gets, it's always too close to the Sun to see by eye. No, Vesta is never bright enough to see by eye. Yes, when Vesta is at magnitude 8.5, it is possible to see by eye.

Yes, when Vesta is at its brightest, it is possible to see by eye.

A CCD can be exposed for long periods of time in order to collect light. How is the light "stored" in the CCD? As pixels As photons Correct! As electric charge As vibrations within the silicon

as electric charge

If the wavelength of light increases, how does the frequency change? It increases as the square of the wavelength. Correct! It decreases. The change depends on the energy of the light. It does not change, because all light travels at the same speed.

it decreases

Match the analogous coordinates between the geographic coordinate system and the celestial coordinate system. Correct! latitude = DEC Correct! longitude = RA

latitude = DEC longitude = RA

Suppose two identical asteroids are the same distance away from the Sun. Which asteroid would appear brighter from the Earth? It cannot be determined from this information. The asteroid that is farthest from the Earth. Correct Answer The asteroid that is closest to the Earth. You Answered They will appear the same brightness from the Earth.

the asteroid that is closest to the Earth.