Unit 8: Discoveries About Stars Flashcards
(99 cards)
1
Q
What does stellar parallax help us determine?
A
The distances to nearby stars using Earth’s orbit as a baseline.
2
Q
Why is measuring stellar parallax important?
A
It proves Earth’s motion and allows calculation of star distances.
3
Q
Why was stellar parallax hard to detect before the 1800s?
A
The angular shift is extremely small due to the vast distances of stars.
4
Q
What is the largest parallax angle detectable with Earth’s orbit?
A
About 1 arcsecond.
5
Q
Why was it difficult to find which stars to measure for parallax?
A
Astronomers didn’t know which stars were closest.
6
Q
Why was targeting bright stars a flawed method for detecting parallax?
A
Some stars are intrinsically bright, even if far away.
7
Q
What discovery by Edmund Halley in the 1700s changed views on stars?
A
Stars have their own motion through space, not just apparent motion.
8
Q
What is proper motion?
A
The actual motion of stars across the sky over long periods.
9
Q
Which star is known for the fastest proper motion?
A
Barnard’s Star.
10
Q
How fast does Barnard’s Star move?
A
About 10 arcseconds per year.
11
Q
What distance unit is based on stellar parallax?
A
Parsec.
12
Q
What is the definition of 1 parsec?
A
The distance to a star with a parallax of 1 arcsecond.
13
Q
How is the distance to a star in parsecs calculated?
A
Using the formula distance = 1 / parallax (in arcseconds).
14
Q
What does ‘parsec’ stand for?
A
Parallax-second.
15
Q
What is a light year?
A
The distance light travels in one year.
16
Q
Why is the light year a useful unit?
A
It also tells how long light has taken to reach us, i.e., how old the light is.
17
Q
How long does it take sunlight to reach Earth?
A
About 8 minutes.
18
Q
What strategy allowed astronomers in the 1830s to detect stellar parallax?
A
Targeting stars that were both bright and exhibited large motion across the sky.
19
Q
Who made the first successful parallax measurement and of which star?
A
Von Struve measured the parallax of Vega in 1837.
20
Q
What parallax shift did Von Struve detect for Vega?
A
One-eighth of an arcsecond.
21
Q
Who measured the parallax of 61 Cygni?
A
Bessel, in 1838.
22
Q
Why was 61 Cygni a good target for parallax measurement?
A
It had high proper motion, was a binary star, and showed noticeable movement across the sky.
23
Q
What was the measured parallax of 61 Cygni?
A
One-third of an arcsecond.
24
Q
Who measured the parallax of Alpha Centauri and where?
A
Thomas Henderson, in South Africa.
25
What is the distance of Alpha Centauri from Earth based on its parallax?
Approximately 1.3 parsecs.
26
What is the significance of Alpha Centauri in terms of proximity?
It is the closest star system to Earth.
27
What was the purpose of the Hipparcos Space Telescope?
To create a detailed star catalog and measure stellar parallax for about 100,000 stars.
28
Why was Hipparcos launched into space?
To avoid atmospheric distortion and increase measurement precision.
29
What limitation did Hipparcos face despite measuring 100,000 stars?
It only covered stars within a small region around the Sun in the Milky Way.
30
What is the Gaia mission's goal?
To measure parallax and positions for up to 4 billion stars, about 1% of the Milky Way.
31
Why is stellar parallax critical for astronomy?
It anchors other distance measurement techniques used for more distant objects.
32
What is light, according to modern physics?
Light is electromagnetic radiation, consisting of oscillating electric and magnetic fields.
33
Who proposed the wave theory of light in the 1600s?
Robert Hooke and Christian Huygens.
34
What does the amplitude of a light wave represent?
The brightness or intensity of the light.
35
What does the wavelength of a light wave determine?
The color of the light.
36
What is wavelength symbolized by?
The Greek letter lambda (λ).
37
What does frequency describe in a light wave?
How many wavelengths are produced per second.
38
What is the relationship between wavelength and frequency?
Inversely proportional: longer wavelength means lower frequency, and vice versa.
39
What wavelength corresponds to red light?
Approximately 700 nanometers.
40
What is the unit nanometer?
One billionth of a meter.
41
What is the electromagnetic spectrum?
The full range of all types of electromagnetic radiation.
42
What are the longest wavelength EM waves?
Radio waves.
43
What are the shortest wavelength EM waves?
Gamma rays.
44
What is infrared radiation commonly associated with?
Heat.
45
What type of EM wave does the Sun emit that can burn skin?
Ultraviolet (UV) light.
46
How are x-rays used in medicine?
To image bones and teeth by passing through skin and reflecting off denser structures.
47
What type of EM wave is used in cancer treatment?
Gamma rays.
48
What does the visible spectrum refer to?
The portion of the EM spectrum visible to the human eye.
49
What wavelength is near the thickness of a soap bubble membrane?
About 500 nanometers.
50
How does our atmosphere protect us from harmful EM radiation?
It blocks or absorbs most UV, x-ray, and gamma radiation from the Sun.
51
What differentiates different types of electromagnetic waves?
Their wavelength, frequency, and energy.
52
Who was Joseph Fraunhofer and what was his profession?
He was a German glassmaker and lens maker in the early 1800s, known for producing high-quality optical glass.
53
What discovery did Fraunhofer make in 1814?
He discovered dark lines in the spectrum of sunlight, now known as Fraunhofer lines.
54
What did Fraunhofer use to observe the sunlight?
A prism to disperse sunlight into a spectrum and a telescope fitted with his lenses to observe it.
55
What are Fraunhofer lines?
Dark absorption lines seen in the solar spectrum, which appear at specific wavelengths.
56
Why were the Fraunhofer lines significant?
They were consistent and unique, acting like a 'fingerprint' of the Sun’s composition.
57
What is a spectroscope?
An instrument that spreads light into its component colors (spectrum) for analysis.
58
Who were Gustav Kirchhoff and Robert Bunsen?
German scientists who developed the technique of spectroscopy and investigated spectral lines from heated elements.
59
What did Bunsen and Kirchhoff discover about heated elements?
Each element produces a unique set of bright emission lines when heated.
60
What are emission lines?
Bright lines on a dark background, showing specific wavelengths of light emitted by an element.
61
How do emission lines differ from the solar spectrum observed by Fraunhofer?
Emission lines are bright lines on a dark background, while Fraunhofer observed dark absorption lines on a bright spectrum.
62
What conclusion did Bunsen and Kirchhoff draw from their experiments?
That each chemical element has a unique spectrum that can be used to identify it.
63
What is spectroscopy?
The study of the light spectrum from a source to determine its chemical composition.
64
How did spectroscopy revolutionize astronomy?
It allowed scientists to determine the composition of stars and celestial objects without needing to visit them.
65
What type of spectrum does the Sun produce?
A continuous spectrum with dark absorption lines caused by elements in the solar atmosphere absorbing certain wavelengths.
66
What is the significance of the quote by Kirchhoff and Bunsen about spectroscopy?
It emphasized that spectroscopy opened up new ways to study the universe far beyond Earth.
67
What did Bunsen and Kirchhoff realize about the Sun’s spectrum?
That the dark lines in the Sun’s spectrum match the bright lines in the spectra of known flame elements like sodium and potassium.
68
What was surprising about combining sunlight with flame light in a spectroscope?
Instead of canceling each other out, the dark absorption lines became even darker.
69
What major conclusion did Bunsen and Kirchhoff reach from their solar spectrum experiment?
That the Sun must have an atmosphere made of gas that absorbs specific wavelengths of light.
70
What causes the dark lines (absorption lines) in the Sun’s spectrum?
The Sun’s atmosphere absorbs specific wavelengths of light emitted from its core.
71
What is the difference between emission lines and absorption lines?
Emission lines are bright lines produced when atoms emit light; absorption lines are dark lines where specific wavelengths are absorbed.
72
How can we observe the Sun’s atmosphere without interference from the core?
By observing the Sun during a total solar eclipse, when the core is blocked by the Moon.
73
What did astronomers confirm by collecting spectra during solar eclipses?
That the Sun has an outer layer of heated gas—an atmosphere—that produces emission lines.
74
What process allows scientists to identify the Sun’s chemical composition?
By matching absorption lines in the Sun’s spectrum with known emission spectra from elements (spectroscopy).
75
What quote summarizes Bunsen and Kirchhoff’s view on solar spectroscopy?
‘The spectrum of the Sun with its dark lines is just a reversal of the spectrum the atmosphere would show by itself.’
76
What discovery was made possible by observing the Sun’s atmosphere during eclipses?
The identification of different elements in the Sun's outer layers through their emission lines.
77
Why couldn't Bunsen and Kirchhoff identify all of the dark lines in the Sun’s spectrum?
Because some chemical elements, like many gases, had not yet been discovered or tested for their spectra.
78
Who began producing spectra for gases, expanding on Bunsen and Kirchhoff’s work?
Julius Plücker, who used vacuum tubes to create spectra for gases like neon, argon, and hydrogen.
79
What major match was made between a gas and the Sun’s spectrum?
Hydrogen’s emission lines matched several of the dark lines in the Sun’s absorption spectrum.
80
What happened in 1868 during an eclipse that led to the discovery of a new element?
Norman Lockyer and Jansen observed a yellow spectral line that did not match any known element.
81
What element was discovered in the Sun before it was found on Earth?
Helium, named after the Greek sun god Helios.
82
Where was helium eventually discovered on Earth?
In the lava from Mount Vesuvius in Italy.
83
By the 1890s, what had spectroscopy allowed scientists to do?
Identify many elements in the Sun’s atmosphere and understand its chemical composition.
84
What scientific method was confirmed and applied to stars beyond the Sun?
Spectroscopy—identifying elements by matching known spectra to those from celestial objects.
85
What is the outermost visible layer of the Sun called, and how is it studied?
The Sun’s atmosphere, studied by analyzing its emission spectrum during a solar eclipse.
86
What does spectroscopy allow us to do without visiting celestial bodies?
Determine their chemical composition using only the light they emit or absorb.
87
What are the three main features that can appear in a visual spectrum?
Continuum light, emission lines (bright lines), and absorption lines (dark lines).
88
What does a graphical spectrum represent?
It represents the intensity of light at each wavelength as a graph.
89
What type of feature does a spike in a graphical spectrum indicate?
An emission line.
90
What type of feature does a dip in a graphical spectrum indicate?
An absorption line.
91
What is a nebula?
A colorful cloud of gas in space; can be emission line nebulae or other types like star clusters or galaxies.
92
Who first analyzed the spectra of nebulae using spectroscopy?
William and Margaret Huggins.
93
What was the first nebula that the Hugginses observed spectroscopically?
The Cat's Eye Nebula.
94
What did the single bright line in the Cat's Eye Nebula spectrum suggest?
That the object was made of hot gas, not stars.
95
What kind of spectrum do star clusters produce?
They show continuum emission and absorption lines, similar to a star’s spectrum.
96
What kind of spectrum does a galaxy produce?
A spectrum with continuum emission, absorption lines, and emission lines.
97
What was the significance of the green line seen in the Cat’s Eye Nebula?
It was initially thought to indicate a new element called 'nebulium', but was later identified as highly excited oxygen.
98
What type of spectrum does a hot gas cloud produce?
An emission line spectrum.
99
How can astronomers differentiate stars, gas clouds, and galaxies?
By analyzing their spectra: gas clouds show emission lines, stars show absorption lines and continuum, and galaxies show all three.
