Science Flashcards

Question

Explain the origin and name some basic characteristics of **magnetic fields**

Answer 1

**Magnetic field** Invisible forces associated with electric currents and motions of electrons in atoms e.g. the field associated with a simple bar magnet **Created by** A charge in motion or vibrating **Magnetism** * A property of some matter * Some matter is “magnetic”

Answer 2

Until 1820, electricity and magnetism were thought to be completely separate **Faraday** In 1832 he showed that you can produce electrical current by simply changing a magnetic field around a conductor. An electromagnetic wave is generated by an electric charge which is non-stationary (moving or vibrating) **Maxwell** In 1873, he devised 4 elegant equations to describe the curl and divergence of electric and magnetic fields * Magnetic fields also curl around a changing electrical field. This generates a magnetic field between the capacitor plates. Electric and magnetic fields are perpendicular to each other and the frequency of the vibrating charge is responsible for the frequency of the EM wave Consequence: when an electric field vibrates the magnetic field generated induces more electric field, this causes EM waves rippling out from the vibrating charge: he predicted radiowaves = the origin of all EM radiation (“Radio to Gamma”) **Heinrich Hertz** (1857-1894) Soon produced radio waves - as predicted by Maxwell - using vibrating charges. He measured wavelength and velocity and showed that they possessed many of the properties of visible light

Answer 3

The concept in quantum mechanics that light may be described as either a * wave * particle * EM radiation Electromagnetic waves display both **wave** characteristics (e.g. reflection, refraction, diffraction) and **particle** characteristics (e.g. Einstein’s Photoelectric Effect, BB radiation)

Answer 4

Multi-Wavelength Astronomy means observations made at all wavelengths. More energetic (hot) objects are observed at shorter wavelengths while colder bodies are generally observed towards the radio end of the spectrum **Radio** Temperature \< 10K cosmic background, cold interstellar medium, regions near neutron stars and white dwarfs **Infra-Red (IR)** T = 10-10^{3 K} cool stars, planets, comets, asteroids **Visible** T = 10³-10⁴K planets, galaxies, stars, nebulae **UV** T = 10⁴-10⁶K supernova remnants, very hot stars, quasars **X-Rays** T = 10⁶-10⁸K cluster of galaxies, neutron stars, supernova remnants **Gamma-Rays** T = More than 10⁸K pulsar or neutron stars, accretion dusks around black holes

Answer 5

Number of cycles of a wave to pass some point in a second. Is expressed in cycles per second, or **Hz** (1 Hertz = 1/s) Concept applies to all types of waves

Answer 6

All electromagnetic waves travel in a straight line trough space v = c = constant in a vacuum (3 x 10⁸ m/s)

Answer 7

E = h v * E is the energy of the radiation * V is the frequency of the radiation in Hz * h is Planck's Constant, 6.626 x 10^-34Js

Answer 8

Our eyes can see just a relatively narrow frequency band of electromagnetic waves, the so-called visible light. This visible light consists of the colors in a rainbow. Each of these colors actually corresponds to different energy (frequency) and a different wavelength e.g. blue light has more energy and a shorter wavelength than red light

Answer 9

**The photoelectric effect** Einstein explained why UV radiation ejects electrons (photoelectrons) from metals, the so-called *Photoelectric Effect.* Einstein noted that the maximum energy of the emitted electrons (maximum kinetic energy, K_max) increases with frequency. He argued that some incoming photons possessed enough energy to release the metallic electrons. This explanation is only feasible if light can behave as a particle **Black body radiation** Max Planck explained the emission of a hot black body by assuming that the energy is carried by discrete “bundles” or “packages” of energy called “photons” * A perfect black body is a theoretical object that absorbs 100% of incident radiation * It is a perfect radiator **Wien's displacement law** When the temperature increases, the peak of emission shifts toward lower λ (higher frequency → higher energy). The peak of the emission spectrum depends on the temperature of the source e.g. healthy human beings maintain a temperature of 310 K (37.0°C) **Atomic Emission spectrum** These spectra are characteristic of thin gases, where electrons become temporarily excited and emit a photon of characteristic energy. These emissions are manifested in colorful emission lines **Atomic absorption spectrum** An absorption spectrum occurs when light from a warm body, e.g. the Sun, passes through a cool, dilute gas and atoms in the gas absorb at characteristic frequencies. Dark lines that can be seen in the spectra as the re-emitted light is unlikely to be emitted in the same direction as the absorbed photon

Answer 10

**Reflection** Angle of incidence = angle of reflection **Refraction** Refraction is the bending of light when the beam passes from one transparent medium into another e.g. starlight passing from interplanetary space into Earth’s atmosphere **Polarization** Light and other EM radiation can be polarized i.e. the wave can have vibrations confined to a single plane that is perpendicular to the direction of motion. The incident wave is vibrating in the same vertical plane as the polarizerand will be transmitted (see picture). However, the transmitted wave will be absorbed by the analyzer, which has a perpendicular vertical plane **Interference** Where two or more waves interact with each other constructively (increasing in magnitude) or destructively (decreasing in magnitude). Light also shows interference **Diffraction** The effect of a wave spreading as it passes through an opening or goes around an object e.g. sound waves can easily be heard around corners

Answer 11

**Microgravity** Microgravity is the perceived effect of lack of gravity (or better, of reduced gravity) that is achievable in orbit or in free fall **Free-fall** * During real free-fall, the only significant force acting on a body is the force of gravity itself and there are no contact forces acting on the body * When an object is in free-fall, the ‘familiar’ effects of gravity are greatly reduced * "Weightlessness" = In free-fall, an object appears to weigh nothing. An object’s weight is actually a measure of how hard gravity pulls on the object **Orbit** Orbit is the state of continuous free fall at the same rate around the curvature of the Earth (or other body), an object in orbit is 'weightless'

Answer 12

**Drop towers** are structures on the surface of the Earth where items can be dropped vertically ~ few seconds **+** Their advantages are low cost, accessibility and controllability **+** They are well suited to certain scientific studies like combustion experiments **-** they are not suited to longer experiments e.g. for life sciences, biotechnology, and materials sciences (living organisms and crystals grow/change too slowly) **Aircraft** that perform parabolic arc flights have a longer duration ~ 5-15 s. **+** The experimenter can fly with their experiment **+** is an interesting (and inspiring) experience **-** Their microgravity quality is not as good as drop towers as they are never truly in free-fall and the aerodynamic drag forces are high **Suborbital rockets** Duration ~ several minutes are small rockets that follow suborbital trajectories, free falling parabolically back to Earth **+** Their microgravity environment is usually very good **+** can carry significant payloads in terms of mass **Orbiting spacecraft** are free falling around Earth **+** Well suited for long-term experiments **+** Astronauts can perform actions on them **-** The microgravity environment is marginal *Comment* Some satellites for gravity experiments have been constructed and claim an environment of ~ 10^-14 g

Answer 13

The internal structure of the Earth is composed by **outer parts** (they are rocky) and **inner parts** (they are metallic): * crust * upper mantle * lower mantle (silicate composition) * outer core (Iron and sulfur liquid composition) * core (iron and nickel solid composition) The Earth’s magnetic field results from the self-exciting dynamo effect in the outer core. It is generated by the convective motion of **ferromagnetic materials** (Fe, Ni, Co, some REE)

Answer 14

Flares are explosions that happen when energy stored in twisted magnetic fields around sunspots is violently released as hot plasma. They release a stream of atoms, ions, electrons and radiation into space

Answer 15

Coronal mass ejections (CMEs) are giant bubbles of hot plasma which escape through the Sun’s corona at high velocities Some of this material collides with the near-Earth environment. Luckily, we can prepare for large CMEs

Answer 16

**Photosphere** Visible surface of Sun ( ~ 6,000 ºC) **Corona** is a hot outer region (\> 1,000,000 ºC) composed of ultra-hot, plasma ** Prominences** are bright, often loop-shaped features, composed of cooler plasma

Answer 17

Ionized gases flow from the Sun’s atmosphere and are directed by the (Solar) magnetic field. This combination leads to 'charged particles' called the solar wind * Composition is close to that of the photosphere, but not as rich in heavy ions (escape of lighter ions more probable) * ~99% of the particles are H+ and He++ ions (i.e., protons and alpha particles) * Of the 99%, ~ 3.5-4.5% are helium ions Space missions like SOHO provided data on velocities of two distinct solar wind types: **Slow wind** from the equator, v ~ 200 km s^-1 (i.e. takes ~ 9 days to reach Earth) **Fast wind** from poles, v ~ 800 km s^-1(i.e. takes ~2 days to reach Earth) • v \> 1,000 km s^-1possible Note that the speeds are *non-relativistic* = not approaching the speed of light

Answer 18

Solar wind interacts with the Earth’s magnetic field (deflects and traps some charged particles, and deforms and compresses it), resulting in the magnetosphere * The particles spiral back and forth along field lines * Most such particles (not deflected by the bow shock) are concentrated in the two **Van Allen Radiation Belts** *Characteristics* * Earth’s magnetic field shields us from much of the solar wind. Solar wind largely deflected “like water around the bow of a ship” (bow shock) * The region of space sitting behind the bow shock and surrounding Earth is termed the magnetosphere: 60-80,000 km (“sunny side”) and out to \> 300,000 km away from Sun.

Answer 19

**Space weather** is a branch of space physics and aeronomy concerned with the time varying conditions within the Solar System, including the solar wind, emphasizing the space surrounding the Earth, including conditions in the magnetosphere, ionosphere and thermosphere. **A geomagnetic storm** Is a temporary disturbance of the Earth's magnetosphere caused by a solar wind shock wave and/or cloud of the magnetic field that interacts with the Earth's magnetic field. The frequency of geomagnetic storms increases and decreases with the sunspot cycle. **Carrington's event** in 1859 the astronomer Carrington noticed an intense burst of white light emerging from two spots * The burst – a ‘super flare’ -- lasted about five minutes and was brighter than the Sun * 17 hours later, the Earth witnessed the worst geomagnetic storm in 500 years (CME) with blood-red aurorae visible even in tropical countries * Telegraph systems malfunctioned, machines burst into flames, compasses were rendered obsolete, etc. * Carrington suggested that there might be a solar-terrestrial connection

Answer 20

During a magnetic storm, the solar wind pushes and pulls Earth’s magnetic field and causes undesirable electrical fluctuations in terrestrial conductors e.g. electrical cables. Several times a year plasma from a solar storm (CME or a massive flare) can lead to chaos **Satellite damage and loss** Satellites are used for TV, phone, radio, banking transactions, military applications, GPS, etc. During a solar storm, a satellite may become ‘disorientated’ and descend in its orbit, or even re-enter the atmosphere. Electrical charges build up and, sometimes, discharge within destroying fragile electrical circuits **Communications problems** Solar storms cause static and interruption of radio/TV/phone signals. All vibrating/moving charges generate EM radiation. Here, solar wind particles are generating (interfering) radio waves **Electrical problems on Earth** During an electrical storm, huge fluctuations affect power lines, melt high-voltage transformers, trip power breakers, etc. **Corrosion on oil/gas pipelines** is greatly accelerated e.g. the Alaskan oil pipeline

Answer 21

**2 definitions** 1. The Solar System may be defined as that volume of our Galaxy corresponding to the heliosphere 2. The Solar System (formed 4.56 billion years ago) may be defined as that part of our Galaxy where the Sun has a significant gravitational influence on those bodies that are relatively close to it. These bodies include: * 8 planets and satellites * Dwarf planets (five recognized) * Minor planets (asteroids) * Trans-Neptunian Objects (Kuiper Belt Objects, Scattered Disk Objects, Oort Cloud Objects) * Comets * Meteoroids (a fraction of which become meteorites) * Interplanetary Dust Particles * Man-made materials e.g. spacecraft/space debris * Any other material or body that orbits the Sun

Answer 22

The heliosphere is the region of our Galaxy in which the Sun’s magnetic field and the solar wind dominate the interstellar medium (Heliosphere) is similar to a planet’s magnetosphere, e.g. * An outer bow shock * A boundary called the heliopause, where energy of solar wind particles \< winds from nearest stars

Answer 23

Disk where icy bodies could have formed *Explanation* In 1943, Kenneth Edgeworth suggested that collisions between particles were so infrequent in the primordial outer Solar System that only small bodies (like comets) could form. It extends from the orbit of Neptune (30 AU) to ~ 55 AU from the Sun

Answer 24

Comets originate in an essentially spherical cloud situated in the outermost edge of the Solar System ## Footnote consists of the spherical, **Outer Oort Cloud** and the doughnut-shaped **Inner Oort Cloud** *Explanation* Proposed by Ernst Öpik In 1932. OC is ~50-50,000 AU from the Sun. No direct OC evidence exists. It is inferred statistically (randomly distributed inclinations of long period comets is well established). Oort cloud comets weekly-bound to the Sun and nearby stars can gravitationally perturb their orbits (and eject them towards the inner Solar System)

Answer 25

Accretion is the accumulation of particles into a massive object by gravitationally attracting more matter, typically gaseous matter, in an accretion disk Most astronomical objects, such as galaxies, stars, and planets, are formed by accretion processes

Answer 26

**Definition** **planet** 1. Is in orbit around the Sun 2. Has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (compression due to gravity is balanced by a pressure gradient force in the opposite direction) and nearly round shape (“gravitationally rounded”) 3. Has cleared the neighborhood around its orbit of debris Pluto does not have requirement 3, It is a dwarf planet.

Answer 27

**The Nebular Collapse model of Laplace** Laplace realized that an accreting “ball of gas” would collapse in a disk and spin as material falls inward, and form an accretion disk as some of the material is flung outward to the edges – via centrifugal force – forming concentric rings. The bulge at the center of this disk can form a Star and the peripheral material may form planets, comets, etc

Answer 28

* *+** The theory allows planets to be as old as the Sun * *-** Does not explain their high angular momentum Previous theories failed to explain why the sun had a little angular momentum and failed to explain how ‘hot gas’ condensed into planets

Answer 29

**Fred Hoyle** (1915-2001) explained the Sun’s low angular momentum and how hydrogen and fine dust were displaced to the outer Solar System * The young Sun had a strong magnetic field and the hydrogen ions (H-, H+) would have acted as tiny “magnets” * Eventually, their period of rotation would have matched that of the Sun. Transfer of momentum (“Sun to gas”) would have slowed Sun’s rotation * Acceleration of the gas may have been sufficient to move them along with the tiniest dust grains to the outer Solar System where they may have accreted into Gas Giants in the new “gas-rich” environment * The inner planets would have accreted from the remaining, larger solids (mostly silicate and oxide grains) in a “gas-free” environment

Answer 30

Thanks to Hubble Space Telescope we can observe dusty disk and bipolar outflows of masses from protostars. Modern telescopes can observe dusty disks around young stars rather similar to the proto Sun. These disks are similar to those predicted by theoretical scientists

Answer 31

**What are meteorites** A meteorite is a natural piece of solid material from the Solar System too small to be regarded as an asteroid, which collides with the Earth (or other planetary body) and lands on its surface **Where do meteorites come from** The vast majority of meteorites are known to be fragments of asteroids and to originate in the asteroid belt. But a minority of meteorites are thought to be small lunar or Martian fragments blasted from the surface by meteorite cometary impacts **Why are they important** Meteorites are the oldest ‘rocks’ that we can study in the laboratory and can tell us about chemical, mineralogical, isotopic conditions in the early Solar System. They have changed little since they accreted in the solar nebula 4.56 Ga

Answer 32

**Smaller asteroids are the source of chondrites**: stone meteorites that are literally “a piece of the Sun” Are tiny fragments of undifferentiated asteroids. They are the most primitive (least heated) and most common types of meteorites and are of most value scientifically. Chondrites are ultimately defined by their elemental abundances which are very similar to those of the Sun’s photosphere ~ 86.2% of all meteorites are chondrites

Answer 33

Larger asteroids are the source of **Achondrites** These bodies differentiated (melted) as a result of sufficiently high temperature internally. Very massive body, the interior is extremely hot.

Answer 34

Chondrites: Stone meteorites that are literally “a piece of the Sun”. This is why abundances in type I carbonaceous chondrites are linear with solar abundances sun and asteroids formed by the same starting ingredients 4.6 billion years ago

Answer 35

Diamonds formed outside the Solar System – They are presolar They are a direct link with the interstellar medium ~ Grains are typically 1-3 nm in size

Answer 36

Most of these grains formed in the cool atmospheres of old stars Probably in the same way that they are made synthetically in the laboratory via chemical vapor deposition (CVD)

Answer 37

When the source is receding from the observer, the light is redshifted (it loses energy). Whether or not the radiation is visible, "redshift" means an increase in wavelength *Example* high redshift quasars (z \> 0.1) CBR: z = 1100 emitted at T ≈ 3000K, now 2.725 K

Answer 38

Speed of wave = wavelength x frequency

Answer 39

**The visible** 380–740 nm for the human eye, up to ~ 900 nm for the astronomer (7600–3200 K) *Technology* * Observers eye * Photographic plates * CCD: Charge-Coupled devices (high-resolution spectroscopy) **Near-infrared** *Technology* * Silicium requires visible photon energy to move the electrons * HgCdTe compounds can be tuned to be sensitive to NIR photons * Adaptive optics * Correct 60% or more of the atmospheric turbulences * Benefit from a larger mirror than from space * Need a bright star nearby but can also use artificial (laser) stars * Also used for communication and EO **Mid and far-IR** *Technology* * As Impurity Band Conduction (IBC) array * From the ground: interferometry * From space: sensibility much higher but resolution worst (until JWST and before ELTs) * Observations from the ground are hampered by high background–where from? * Instruments must be cooled to a few K (He) **Radio Astronomy** **The Ultraviolet** 10–320 nm *Technology* Micromechanical plate detectors MCP * *Xrays and gamma rays** 0. 01-10 nm and below, only from space *Technology* CCD, with single-photon detection e.g. on ESA’s XMM–Newton: Metal Oxide Semi-conductor (MOS)

Answer 40

**The visible** 380–740 nm for the human eye. Most of the stars and nearby galaxies’ energy are emitted in the visible e.g. the Sun at 500 nm (5,772 K) **Near-infrared** * Brown dwarfs emit most of their energy in the near-infrared * Young circumstellar disks **Mid and far-IR** very cool object * Circumstellar discs - important molecules: NH3, C2H2, CO2, HCN, Polycyclic aromatic hydrocarbon (PAH) - Nano-diamonds and ices: H2O, CO * Extremely red galaxies, star-forming galaxies **Radio Astronomy** * Cold regions such as circumstellar disks * CO lines * Electrons moving in a magnetic field * Supernova remnants * Neutron stars that have strong magnetic fields (creating jets) * The Sun **The Ultraviolet** 10–320 nm any event that involves high temperatures/energies: * Stellar coronae * Interactions with the stellar winds (e.g. aurorae on comet 67P/Churyumov-Gerasimenko) * Gases in the interstellar medium * Accretion unto compact objects as white dwarfs * *Xrays and gamma rays** 0. 01-10 nm and below, only from space * binary stars with accretion into a neutron * Black hole accretion, e.g. Cygnus X-1 * supernovae

Answer 41

**Multiwavelength observations** * Identify and characterize celestial objects * Obtain intrinsic parameters * Determine redshift based on low-spectral-resolution data * e.g. when spectroscopy is not possible (faintness * Detect in one wavelength and study in another * highly energetic, transient objects * refine position * Technology* * GROND on ESO-MPG/2.2m in La Silla * X-Shooter on the ESO/VLT in palanel * ESA's Euclid

Answer 42

In the circular, restricted **Three-Body Problem,** the two massive bodies orbit their center of mass in coplanar, circular motion. The third body is too small to have an effect on the other two. Analytic solutions of this problem identify 5 points where the particle (small body) has zero acceleration and zero velocity in the rotating frame. These are known as libration or lagrangian points (L-points). The L-points mark the positions in which the small body, under the influence of gravity only, would maintain a stable configuration with the other 2. **If an object is placed in one of the L points, it would remain stationary relatively to the other two**

Answer 43

Two bodies are in resonance when their orbital periods have a ratio of integer numbers. *Explanation* The number ratio indicates the number of orbits of the first body relative to the orbits of the second body. For example, a 7:3 resonance with Jupiter means that the asteroid completes 7 orbits for every 3 orbits of Jupiter around the sun.

Answer 44

Resonances affect the stability of orbits in planetary systems and play a significant role in the evolution of planetary systems

Answer 45

Tidal forces can be explained by taking into account that the orbiting bodies have volume, that is to say, not all points of the first body are in the same distance from the second body. Thus, they experience unequal gravitational forces. The net effect is the stretching of the body. *Consequences* * Tidal forces can alter the orbit of satellites, making a moon spiral outwards or inwards (Orbit expansion of the Moon and the inner satellites of Jupiter, Saturn and Uranus, Orbit decay of Phobos and Triton) * The movement of mass that creates the tidal bulges creates a lot of energy and can cause heating and volcanism (**tidal heating**). * Tides transport *angular momentum* between planetary rotation and satellite orbits. It is the reason most major moons have a synchronous rotation rate with their planets (**spin-orbit lock**). * If the moon approaches too close to the planet, it may reach a point when its internal forces cannot resist the tidal forces and it fragments (breaks apart). That point is called the *Roche limit*. The fragments can then continue to orbit in a **ring formation**.

Answer 46

They are short-term, photospheric objects associated with areas of intense, magnetic activity * Their dark color reflects their relative coolness as convection is inhibited by the strong magnetic fields * Sunspots move as Sun rotates on its axis * Sunspot activity follows an 11-year cycle, which is related to solar activity (Solar Maximum) * Underlying physics is poorly understood * Some sunspots are growing rapidly and could pose a threat for Earth-directed M-class solar flares (Flares release a stream of atoms, ions, electrons and radiation into space)

Answer 47

**AU** distance Sun-Earth **Parsec** Distance between 2 stars **Luminosity** Is the absolute brightness of a star given by the amount of energy radiated from its surface per second (in watts or in terms of the sun’s luminosity. Energy emitted from a body per second (Abs Value) OR comparison with Sun.

Answer 48

**Star** Accretions of gas and dust that radiate energy by nuclear fusion reactions. Pierre-Simon Laplace (1749-1827), the father of **nebular collapse theory**, which proposes that a collapsing ball of gas and dust will form a spinning disk. Dust grains may then collide and bind electrostatically forming increasingly larger bodies. **Birth** Gas cloud fragmentation. Stars form in vast clouds of cold gas and dust, dense molecular clouds. Most stars dominantly composed of H and He * Low density, 10K; contains gas and dust * Gravity induces contraction: increases with density * Internal gas pressure keeps molecules away from each other more efficient at small scale, for large sound speed * Clouds larger than the Jeans length will collapse * equilibrium at Jeans mass (Jeans 1902) * Determines the minimum stellar mass for that cloud * effects of magnetic field difficult to take into account **Dark Clouds** Region between stars is called the interstellar medium (ISM) * Dense Interstellar Molecular Clouds are very cold (10-50K) regions of gas ( ~ 99%) and dust ( ~ 1%) * Galactic radiation is filtered so many molecules survive * 10⁹-10¹² particles m^-3 (compared to 10⁶ in the ISM in general) but still 10⁶ times less than a ‘good laboratory vacuum’ * Most molecules in dense clouds are ices (not in gas phase) **Protostar** * Contraction continues as gravitational potential energy is converted to heat that is radiated away: the stronger the radiation, the faster the contraction * This depends on composition (amount of metals) Lower level metal and light escapes easier * At a certain point, the contracting fragment is sufficiently hot and compact to be considered a protostar * A protostar is a compacting body that will evolve to become a main sequence star * The more massive the protostar, the quicker it evolves to a main sequence star **Around the young star, a circumstellar disk forms** * why as a disk * the original cloud had a (even small) rotation * as the gas contrasts the rotation rate increases to conserve angular momentum * note: this works in 3D only * lifetime: 10 to 20 Myr

Answer 49

**Cycle** Stars are born, evolve, and die in different ways, largely depending on their mass * *Low mass stars** (0. 08-1.4 solar masses) evolve through a red giant phase stars and ultimately white dwarfs **High mass stars** (\>2 solar masses) evolve to supernovae producing heavy elements, leaving behind a neutron star or black hole

Answer 50

The HR Diagram compares Temperature and Luminosity of different stars status, including the Main Sequence * MS is a region of the Hertzsprung-Russell Diagram where most stars lie * MS characteristics largely mass-dependant * MS represents ~90% of a star’s lifetime * Henry Norris Russell and Heinrich Vogt (1890-1968) determined that a certain mass of stellar material of fixed composition can reach only one stable configuration.

Answer 51

**3 phases** * 2 atoms of H fuse into Deuterium * 1 more atom of H joins Deuterium making 3 He * 3 He is bombarded with another 3 He, make 4 He and releases 2 atoms of H, which restart 1 A star is in equilibrium if nuclear and gravitational forces are equal * Other reaction chains exist (CNO as catalysts) * The greater the mass of a star, the further it contracts until radiation pressure can counter-balance gravity

Answer 52

Big Bang Stars Low Mass vs. High Mass Red Giants vs. Red Super Giants Planetary Nebulae vs. Supernova White Dwarf vs. Neutron Star or Black Hole

Science Flashcards

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