Stars and Stellar Structure Flashcards

Question

what colour do hot stars emit? and cool stars?

Answer 1

hot = blue cool = red

Answer 2

its temperature

Answer 3

By finding its radius via the Stefan-Boltzmann Law

Answer 4

(constant) x (temperature)^4 𝐿 = 𝐴𝜎𝑇^4

Answer 5

2.07 - 1.2 x 1.2 x 1.2 x 1.2 This is because 20% increase = 1.2

Answer 6

If we know T and L, then we can figure out the A in the law. From hear using the formula for the surface area for a sphere, we can find the radius ( 𝐴 = 4𝜋𝑅^2)

Answer 7

The star’s annual parallax, apparent magnitude, and B – V colour index

Answer 8

Two stars in are orbiting each other around a center of mass. around 50% of Stars are binary Stars

Answer 9

1. Astrometric 2. Eclipsing 3. Visual 4. Spectroscopic

Answer 10

Were we can see the two stars orbiting each other, some can be seen with he naked eye but most with binoculars/telescopes

Answer 11

Like visual binary but one star is far too faint to see, but you can still see the wobble of the bright star

Answer 12

From "side view" one star passes between the other and the observer. Like when the moon and sun eclipse.

Answer 13

Doppler shifts in the spectrum of a star reveal a companion Measure the spectrum of the bright star over time The Doppler shift changes periodically Indicates orbiting companion

Answer 14

Stars are found throughout the universe and are essential for the formation of chemical elements that make up our bodies.

Answer 15

Some stars are brighter than others, dimmer stars are more numerous, and some are too dim to see without telescopes or binoculars.

Answer 16

Betelgeuse, Rigel, Sirius, Polaris.

Answer 17

A constellation is a pattern of stars that humans have created pictures from, often based on local wildlife, culture, or mythology.

Answer 18

88 constellations.

Answer 19

Stars are labelled with Bayer letters, ordering them from brightest to dimmest, with alpha (𝛼) being the brightest.

Answer 20

Stars are named by their position in the sky across the constellation, from west to east.

Answer 21

A unique identifier for stars in various catalogues, such as HR, HD, and HIP numbers.

Answer 22

The brightness of a star.

Answer 23

Brighter stars.

Answer 24

A brightness ratio of 100.

Answer 25

A method used to determine the distance to a star by measuring its position change from different perspectives.

Answer 26

The apparent motion of stars against the background of more distant stars.

Answer 27

How far away are they? How big are they? How hot are they? What are they made of?

Answer 28

It is the largest star catalogue, containing over one billion stars.

Answer 29

The total amount of energy emitted by a star per unit of time.

Answer 30

The brightness observed depends on the distance from Earth.

Answer 31

* The Sun: -26.7 * The full moon: -12.5 * Venus: -4 to -5 * Jupiter: -2.5.

Answer 32

The brightness of a star as it would be observed at a standard distance of 10 parsecs.

Answer 33

The brightness of a star decreases with the square of the distance from the observer.

Answer 34

The process of using triangulation to determine the distance to a star by measuring its apparent shift in position as seen from different locations on Earth's orbit. ## Footnote Parallax is crucial for measuring distances to stars and involves observing the star from two different points in Earth's orbit.

Answer 35

Using angles, specifically in degrees, arcminutes, and arcseconds. ## Footnote One degree is divided into 60 arcminutes, and each arcminute is divided into 60 arcseconds.

Answer 36

The average distance between the Earth and the Sun, defined as 1 AU = 150,000,000 km. ## Footnote This unit is commonly used for distances within our Solar System.

Answer 37

The distance that light travels in one year, equivalent to approximately 9.5 × 10^12 km. ## Footnote 1 light year is also equal to about 63,000 AU.

Answer 38

A unit of distance used in astronomy, defined as 1 parsec = 3.26 light years. ## Footnote The parsec is related to the parallax method for measuring distances to stars.

Answer 39

Distance is inversely proportional to the parallax angle; further stars have smaller parallax angles. ## Footnote The formula for distance in parsecs is d (pc) = 1/p (arcseconds).

Answer 40

The actual movement of a star through space, separate from its apparent motion caused by parallax and Earth's rotation. ## Footnote Most proper motions are not noticeable without precise measurements.

Answer 41

The rate at which a star emits energy in the form of light, measured in Watts (W). ## Footnote The Sun has a luminosity of 4 × 10^26 W.

Answer 42

The intensity of light from a star decreases with the square of the distance from the star. ## Footnote This means that if you double the distance, the brightness decreases by a factor of four.

Answer 43

A measure of the intrinsic brightness of a star as it would be observed from a standard distance of 10 parsecs. ## Footnote The absolute magnitude is denoted by M, while apparent magnitude is denoted by m.

Answer 44

The difference between a star's apparent magnitude and absolute magnitude, expressed as m - M. ## Footnote A negative distance modulus indicates a star is closer than 10 parsecs.

Answer 45

Hotter stars appear blue, while cooler stars appear red, with colors ranging from blue to red based on surface temperature. ## Footnote This color-temperature relationship is counterintuitive as red is often thought of as 'warm'.

Answer 46

A hypothetical object that perfectly absorbs all radiation falling on it and emits light based on its temperature. ## Footnote Many real objects, including stars, can be approximated as black bodies.

Answer 47

The Kelvin scale, where absolute zero is the zero point. ## Footnote The conversion from Celsius to Kelvin is done by adding 273.15.

Answer 48

It has the greatest proper motion of any star, moving just over 10” per year. ## Footnote Its parallax angle is about 0.55′′, making it one of the closest stars to Earth.

Answer 49

kelvins = ◦C + 273.15

Answer 50

The coldest temperature possible, with no thermal energy.

Answer 51

* Maximum intensity increases * Total intensity (area under the curve) increases * Curve shifts in wavelength to lower values (towards ultraviolet)

Answer 52

Approximately 5800 K

Answer 53

The difference in a star’s brightness in different colours of light.

Answer 54

* U — ultraviolet * B — blue * V — visible

Answer 55

B − V < 0 (the star appears blue)

Answer 56

B − V ≈ 0 (the star appears white)

Answer 57

B − V > 0 (the star appears red)

Answer 58

Around 3000K or slightly lower

Answer 59

In excess of 20,000K

Answer 60

Approximately 700,000 km

Answer 61

Luminosity = (constant) × (surface area) × (temperature)⁴

Answer 62

L = 4πσR²T⁴

Answer 63

Around 0.1R⊙

Answer 64

Approximately 760R⊙

Answer 65

Around 50%

Answer 66

A system of stars where the individual stars can be seen separately.

Answer 67

A binary system where one star is much fainter than the other, causing observable changes in the brighter star's position.

Answer 68

Binary systems viewed in line with their orbit, causing periodic dips in brightness.

Answer 69

Binary systems observed based on changes to their spectral lines due to the Doppler effect.

Answer 70

a³ / (M₁ + M₂) = P²

Answer 71

Solar masses (M⊙)

Answer 72

The study of star systems and any orbital configuration.

Answer 73

The period of an orbit 𝑃 to the average distance (semimajor axis 𝑎) and the total mass of the bodies.

Answer 74

𝑎³/(𝑀1 + 𝑀2) = 𝑃²

Answer 75

Star masses in solar mass M⊙, semimajor axis in AU, and period in years.

Answer 76

The relative masses of the bodies.

Answer 77

The ratio of the stars' masses (𝑀1/𝑀2).

Answer 78

𝑀𝐴 = 2𝑀𝐵

Answer 79

They have about one tenth the mass of the Sun.

Answer 80

Star-like objects that cannot undergo nuclear fusion due to insufficient mass.

Answer 81

100-120 times the mass of the Sun.

Answer 82

They become so luminous that radiation pressure blows off their outer layers.

Answer 83

Stars based on their temperatures and luminosities.

Answer 84

Towards the left.

Answer 85

A diagonal band where most stars fall during their longest part of their lifetimes.

Answer 86

Hotter stars are always more luminous.

Answer 87

Stars that are more luminous than main sequence stars with the same temperature.

Answer 88

Stars that are white in color but much less luminous than white main sequence stars.

Answer 89

𝐿 ∝ 𝑀³.⁵

Answer 90

Harvard classification system.

Answer 91

O, B, A, F, G, K, M

Answer 92

It differentiates stars of the same temperature based on their sizes.

Answer 93

Dark bands that indicate the presence of specific elements.

Answer 94

Hydrogen (73.9% by mass)

Answer 95

The process through which stars generate energy by fusing hydrogen into helium.

Answer 96

4 × 10²⁶ joules every second.

Answer 97

The calculated lifetime of the Sun based on gravitational contraction.

Answer 98

The lifetime of the Sun under the gravitational contraction scheme, estimated to be about 25 million years.

Answer 99

9 × 10¹⁵ J

Answer 100

* Fission: splitting heavy atoms into smaller ones * Fusion: joining small particles/atoms to produce heavier elements

Answer 101

At the core of the Sun.

Answer 102

Positively charged particles found in the nucleus of an atom.

Answer 103

Particles similar in mass to protons but with no charge, also found in the nucleus.

Answer 104

Negatively charged particles that orbit the nucleus.

Answer 105

The number of protons in the nucleus.

Answer 106

Atoms with the same number of protons but different numbers of neutrons.

Answer 107

An atom with fewer or more electrons than protons.

Answer 108

The creation of helium from four single protons (hydrogen nuclei).

Answer 109

3.96 × 10⁻¹² J

Answer 110

95 billion years

Answer 111

A balance between gravitational force and gas pressure within the Sun.

Answer 112

* Core: where fusion takes place * Radiative zone: heat transferred through radiation * Convective zone: heat transported by buoyancy of gas bubbles

Answer 113

About 15 million K.

Answer 114

About 6000 K.

Answer 115

Energy is transported primarily by light radiation.

Answer 116

Convection of hot gas bubbles.

Answer 117

A process for converting hydrogen to helium that occurs in more massive stars.

Answer 118

The spontaneous emission of particles from an unstable nucleus, transforming it into a different element.

Answer 119

The time it takes for half of a substance to decay.

Answer 120

12C captures a proton, producing 13N and a photon.

Answer 121

It decays into 13C, emitting a positron and a neutrino.

Answer 122

12C and 4He.

Answer 123

15O decays into 15N, producing a positron and a neutrino ## Footnote The half-life of 15O is 122 seconds.

Answer 124

12C and 4He are produced ## Footnote This reaction is part of the CNO cycle.

Answer 125

Both processes convert 4 protons into helium ## Footnote The CNO cycle occurs in stars with greater mass.

Answer 126

Greater temperatures are required to overcome electrostatic forces ## Footnote The electric charge of heavier elements involved in the reaction is greater.

Answer 127

Stars larger than the Sun have smaller convective envelopes, some having none at all.

Answer 128

The rate at which the CNO cycle generates energy is extremely sensitive to temperature.

Answer 129

Helium builds up in their cores until hydrogen fusion stops.

Answer 130

It is the fusion of three helium nuclei to form carbon-12 (12C) ## Footnote Requires temperatures around 108K.

Answer 131

It does not result in a stable nucleus.

Answer 132

The triple alpha process jumps from helium (Z = 2) to carbon (Z = 6).

Answer 133

It is the fusion of helium nuclei with heavier elements, increasing atomic and mass numbers ## Footnote Example: 12C + 4He → 16O.

Answer 134

It is the process where energetic gamma-ray photons break apart nuclei.

Answer 135

Iron-56 (56Fe).

Answer 136

Energy cannot be released in the fusion of iron.

Answer 137

It is the energy required to break a nucleus completely apart.

Answer 138

It plots binding energy per nucleon against the number of nucleons (mass number).

Answer 139

More neutrons are needed to keep the nucleus stable.

Answer 140

It is a slow neutron capture process that builds heavier isotopes in stars.

Answer 141

It is a rapid neutron capture process occurring under extreme conditions, such as in supernovae.

Answer 142

It has no stable isotopes and is produced in s-process reactions ## Footnote Its spectral lines are observed in red giant stars.

Answer 143

Brightness falls rapidly at first, followed by a gradual dimming.

Answer 144

Photosphere, chromosphere, and corona.

Answer 145

Temperature changes with height above the surface.

Answer 146

Photosphere, Chromosphere, Corona ## Footnote Each layer has distinct temperature and density characteristics.

Answer 147

5800 K ## Footnote The photosphere is where most of the light radiated from the Sun is released.

Answer 148

Granulation, Sunspots, Pores ## Footnote These features can be observed especially during times of solar activity.

Answer 149

A layer above the photosphere, about 1500 km thick ## Footnote It starts 500 km above the surface.

Answer 150

H-alpha ## Footnote H-alpha has a wavelength of 656.3 nm.

Answer 151

Increases from photosphere temperature to about 20,000 K ## Footnote Density drops steadily as well.

Answer 152

A very thin layer where temperature rises from 20,000 K to over 1,000,000 K ## Footnote It separates the chromosphere from the corona.

Answer 153

The unexpected increase in temperature of the corona as we move away from the Sun's surface ## Footnote This area is a significant research focus in astrophysics.

Answer 154

Ultraviolet and X-rays ## Footnote These wavelengths must be observed from space due to atmospheric blockage.

Answer 155

Bright cells surrounded by dark borders, about 1000 km wide ## Footnote This is evidence of the convective zone underneath.

Answer 156

Dark patches due to being about 2000 K cooler ## Footnote They indicate areas of strong magnetic activity.

Answer 157

Several times the size of the Earth ## Footnote They often appear in pairs of opposite magnetic polarity.

Answer 158

An 11-year cycle of solar activity as indicated by sunspot numbers ## Footnote Solar maximum is when activity is highest, and solar minimum is when it is lowest.

Answer 159

The Sun rotates at different rates depending on solar latitude ## Footnote 25 days at the equator and 35 days at the poles.

Answer 160

Indirectly inferred by dips in a star's brightness ## Footnote Larger starspots are easier to detect.

Answer 161

Coronal mass ejections (CMEs) ## Footnote Both can significantly impact space weather.

Answer 162

The study of the changing environment in space, particularly concerning Earth ## Footnote Includes phenomena like solar wind and CMEs.

Answer 163

Rapid brightenings in the light received from distant stars ## Footnote These can be much more powerful than solar flares.

Answer 164

An extremely powerful flare from a star, up to 100,000 times stronger than solar flares ## Footnote Can cause significant impacts on planetary habitability.

Answer 165

Unprecedented damage to our systems here on Earth

Answer 166

They can increase UV radiation, which can be extremely harmful to lifeforms

Answer 167

It leads to many magnetic phenomena and cycles of activity revealed by sunspot numbers

Answer 168

Space weather that can impact us here on Earth

Answer 169

Lower mass stars due to their greater convective envelopes

Answer 170

Spectacular distant objects

Answer 171

sunspot numbers

Answer 172

It shows multiple spikes in brightness