All flashcards
Flashcard 1: What is the difference between a star's apparent brightness and its actual brightness (luminosity)?
Answer: Apparent: how bright it looks; luminosity: how much light it emits. Apparent depends on distance; luminosity is the star's true energy output.
Flashcard 2: What observation best supports the claim that a star looks dim because it is very far away?
Answer: It is dim but shows the same color/type as known bright nearby stars. Same spectral type suggests similar luminosity, so dimness indicates distance.
Flashcard 3: Which graph best supports the claim that brightness decreases as distance increases for similar stars?
Answer: A graph where brightness drops as distance rises (negative trend). Inverse relationship shows brightness decreases with distance.
Flashcard 4: What is the most direct observational evidence that a star is brighter than another star in the same photo?
Answer: It has a higher measured light intensity (more counts) in the image. Higher photon counts directly measure greater brightness.
Flashcard 5: Which evidence best supports that two stars have different luminosities if they are the same distance away?
Answer: They have different measured apparent brightness at the same distance. Same distance eliminates that variable, isolating luminosity differences.
Flashcard 6: What observation supports the claim that dust between Earth and a star makes it look dimmer?
Answer: The star is dimmer and redder than similar stars without dust. Dust absorbs light and scatters blue wavelengths more than red.
Flashcard 7: Which factor changes a star's apparent brightness even if the star itself does not change?
Answer: Distance from Earth. Only distance affects how bright a star appears from Earth.
Flashcard 8: What observation would you use to support the claim that a star's brightness changed over time?
Answer: Repeated measurements show it is brighter/dimmer on different dates. Changing brightness values prove the star itself varies.
Flashcard 9: Which statement is supported by observing that two stars look equally bright but one is farther away?
Answer: The farther star has greater luminosity. Equal apparent brightness but greater distance requires more actual light output.
Flashcard 10: Choose the claim best supported by observing a star is dim but has very high luminosity data.
Answer: It is very far away. High luminosity appearing dim means great distance.
Flashcard 11: What does it mean if a star appears brighter in a telescope image with a longer exposure time?
Answer: The image collected more light; the star itself may be unchanged. Longer exposure gathers more photons without changing the star.
Flashcard 12: What is the best observational evidence that a star is intrinsically dim, not just far away?
Answer: It is close (near distance) yet still appears dim. Nearby stars should appear bright unless they have low luminosity.
Flashcard 13: Which comparison is most fair when using photos to argue about which star is brighter?
Answer: Photos taken with the same telescope settings and exposure time. Consistent settings ensure differences reflect actual star brightness.
Flashcard 14: What is the best evidence to support that a star is closer if it appears brighter than similar stars?
Answer: Distance measurement shows it is nearer than the similar stars. Similar stars have similar luminosity, so brightness differences indicate distance.
Flashcard 15: Which observation supports the claim that a star is bright because it is nearby rather than very luminous?
Answer: It has a small luminosity estimate but a short distance from Earth. Low luminosity but high apparent brightness indicates proximity.
Flashcard 16: Identify the main tool scientists use to collect light from stars for brightness measurements.
Answer: Telescope. Telescopes gather and focus starlight for analysis.
Flashcard 17: Which option is an observation (evidence) rather than an inference about star brightness?
Answer: Measured brightness values recorded over time. Direct measurements are observations; conclusions about why are inferences.
Flashcard 18: What is the key observation used to argue that a star is not steady in brightness over time?
Answer: Its measured brightness changes on repeated observations. Variable stars change brightness periodically.
Flashcard 19: Which observation is evidence that atmosphere affected a brightness measurement?
Answer: The star looks dimmer on a hazy night than on a clear night. Haze scatters light, reducing the star's apparent brightness.
Flashcard 20: What is the difference between apparent brightness and intrinsic brightness of a star?
Answer: Apparent: how bright it looks from Earth; intrinsic: true brightness. Apparent depends on distance; intrinsic is the star's actual light output.
Flashcard 21: What observational evidence shows that distance affects a star's apparent brightness?
Answer: The same type of star looks dimmer when it is farther away. Distance causes light to spread out, reducing brightness per unit area.
Flashcard 22: Which observation best supports that a star appears dimmer because it is farther away?
Answer: It has the same color/type as a brighter star but looks fainter. Same star type ensures equal intrinsic brightness for fair comparison.
Flashcard 23: What tool provides observational evidence by measuring star brightness as a number?
Answer: A photometer (or light sensor) measuring brightness. Converts light intensity to numerical values for precise comparison.
Flashcard 24: What does it mean if two stars have the same apparent brightness in observations?
Answer: They look equally bright from Earth. Same apparent brightness doesn't reveal which is closer or brighter.
Flashcard 25: Which observation supports that a star is intrinsically brighter, not just closer?
Answer: It is bright even though evidence shows it is very far away. High apparent brightness despite great distance indicates high intrinsic brightness.
Flashcard 26: What is the main observational clue that a star is closer than another similar star?
Answer: It appears brighter when the stars are the same type/color. Same type ensures equal intrinsic brightness, so brighter means closer.
Flashcard 27: Identify the observation that best supports: "Star A is closer than Star B." Both are the same color.
Answer: Star A appears brighter than Star B. Same color indicates similar type, so brighter appearance means closer distance.
Flashcard 28: What is a light-year, and why does it matter for star brightness observations?
Answer: Distance light travels in 1 year; greater distance means dimmer appearance. Light spreads out over distance, making distant stars appear dimmer.
Flashcard 29: What does a star's color provide observational evidence about that helps compare brightness fairly?
Answer: Its temperature/type, helping compare similar stars. Color indicates temperature, allowing comparison of similar star types.
Flashcard 30: Which observation is strongest evidence that two stars should be compared as similar types?
Answer: They have the same color. Same color indicates similar temperature and star type.