Term
|
Definition
| Stars are huge balls of burning gas that emit light from far away distances. |
|
|
Term
| What is the defining characteristic of stars? |
|
Definition
| nuclear FUSION in the core of a star. FUSION FUSION FUSION |
|
|
Term
| How does the Sun hold itself up against self-gravity? |
|
Definition
| It is held up by gas pressure. |
|
|
Term
| How is the Sun structured? What are its atmospheric layers? |
|
Definition
| Made up of Photosphere, Chromosphere, and Corona. |
|
|
Term
| What is the chemical composition of the Sun and how does it compare to those of the planets? |
|
Definition
| Much like a Jovian planet. Made up of Hydrogen, Helium, and other gases. |
|
|
Term
| What fusion reaction is the Sun using (primarily) and where? |
|
Definition
| Nuclear fusion in hot, dense core. |
|
|
Term
| What was the solar neutrino "problem"? |
|
Definition
a lot of solar neutrinos on Earth, but we have only observed about 1/3 the expected.
Solution=neutrinos transformed to two other kinds and when we found three we counted them all. |
|
|
Term
| What are sunspots and why are they relatively dark? |
|
Definition
| dark spots in the photosphere, the darker the cooler. very magnetic. |
|
|
Term
| What drives the solar activity cycle? |
|
Definition
| driven by magnetic field growth. |
|
|
Term
| How do we determine basic stellar properties such as surface temperature, chemical composition, luminosity, mass, size, and velocity? |
|
Definition
|
|
Term
| How do we measure distances to stars? |
|
Definition
| by using the parallax method. distance-to-star = Earth-Sun distance / parallax-angle |
|
|
Term
| What is a stellar parallax? |
|
Definition
| the slight back-and-forth shifting of star positions that occurs as we view the stars from different positions in Earth's orbit of the Sun. |
|
|
Term
| Are the brightest stars in the night sky just closer to us or are they relatively far away & unusually luminous? |
|
Definition
| it depends on size, distance, and luminosity. Those stars that are closer and more luminous appear brighter than stars that are farther away and less luminous. |
|
|
Term
| How does the Sun's luminosity compare to other stars? |
|
Definition
| our Sun is about average compared to other stars in the universe. |
|
|
Term
| What does E=mc2 mean and how is it particularly relevant to the fusion process? |
|
Definition
| mass is a form of energy, stars creates their own energy through fusion. |
|
|
Term
| Why does fusion require extremely high temperatures and densities? |
|
Definition
To bond together, two nuclei must be thrown together with great force. This is fusion. Must overcome electrical repulsion of two fusing, must go really fast=high temps.
Also particles are incredibly small and they repel so they need high density to find each other and must go fast to carry out fusion. |
|
|
Term
| What kinds of particles fuse in fusion reactions? |
|
Definition
| hydrogen, helium, carbon. They are positively charged atomic nuclei=what is fusing. |
|
|
Term
| How do fusion reactions produce energy? |
|
Definition
| Nuclear fusion involves the joining together of two atomic nuclei, fusing them into a single nucleus. When you join two nuclei together (usually light nuclei with only a few protons and/or neutrons), a tremendous amount of energy is released. |
|
|
Term
| Where do fusion reactions occur in a star? |
|
Definition
|
|
Term
| How do stars fuse hydrogen, helium, carbon, etc? |
|
Definition
| Hydrogen: proton-proton chain/CNO cycle, Helium: triple alpha (two step process), Carbon: alpha capture. |
|
|
Term
|
Definition
| stars form in cold, dense gas clouds, gravitationally contracting & fragmenting |
|
|
Term
| Which stars are most numerous, which provide the most mass, which generate the most light? |
|
Definition
| most numerous: high mass most mass: top left most light: giants top right and high mass |
|
|
Term
| How old is the Sun and when will it start to die? |
|
Definition
| 5 billion years, it will start to die at 10 billion years. |
|
|
Term
| What stellar property determines how quickly a star evolves (and dies)? |
|
Definition
| stellar evolution theory( lifetime = τ ∝ Mc2/L ) |
|
|
Term
| How does the temperature for helium fusion compare to that for hydrogen fusion? |
|
Definition
| The triple-alpha process requires more energy because fusing only two helium nuclei results in some form of unstable beryllium. |
|
|
Term
| How do stars die? What are the three kinds of stellar corpses? What stellar property determines which way a star dies? |
|
Definition
From the same way a star is born, it dies. As the nuclear fusion process takes place. Each atom slams into each other, not only producing that energy but the two atoms that smash turn into one atom, a heavier atom. It turns from Hydrogen to a heavier element Helium and so forth down the periodical table of elements. The heavier the element the more heat is required to fuse them toghter. Pending on the mass of the star, a star can continue the nuclear process all the way to the element iron. Iron is an element that absorbs energy so the nuclear process ends there for majority of the stars. The stars core will try to fuse iron but fail, and the star expands and boom super nova.
White Dwarf +Planetary Nebula, Neutron Star + Supernova II, Black Hole
Luminosity |
|
|
Term
| What happens to a star if it tries to fuse iron in its core? |
|
Definition
| iron core implosion...it produces a neutron star |
|
|
Term
| What will the Sun become when it dies? What will most stars end up as? |
|
Definition
| white dwarf. black holes. |
|
|
Term
| How can a star's evolution be affected by being in a close stellar binary system? |
|
Definition
| If two stars orbit close enough they can transfer mass to one another |
|
|
Term
| What kinds of stars blow up in supernovae? What do these explosions leave behind? |
|
Definition
Type I accreting WD, in binary star system, completely explodes, old stellar population
Type II single massive star has iron core collapse, leaves NS remnant, young stellar population |
|
|
Term
| What is a planetary nebula? |
|
Definition
| gas cloud puffed off from distended and unstable star. the core shrinks and becomes white dwarf. |
|
|
Term
| What do Hertzsprung-Russell diagrams plot? Why are they useful? |
|
Definition
| plot stellar TEMPERATURE vs. LUMINOSITY |
|
|
Term
| What other stellar properties (apart from those explicitly plotted) can be deduced from Hertzsprung-Russell diagrams? |
|
Definition
get AGE of star clusters from MS Turnoff
high L, high T limit (upper left) of MS
most luminous stars die in < 106 yrs
least luminous stars die in > 1011 yrs
=> upper left of MS erodes down over time
get DISTANCE to star clusters by matching MS
"spectroscopic parallax" |
|
|
Term
| How are the mass and luminosity of main sequence stars related? |
|
Definition
| Luminosity depends directly on mass |
|
|
Term
| What is the relative size of a star which is cooler than the Sun but is more luminous? |
|
Definition
| get AGE of star clusters from MS Turnoff |
|
|
Term
| What is a white dwarf? How does a white dwarf form? |
|
Definition
| White dwarf stars are formed when stars of 0.08 and 8 solar masses expand into red giants, than start to shrink, and die. Whats left is a white dwarf. |
|
|
Term
| How does a white dwarf holds itself up against its self-gravity? |
|
Definition
| electron degeneracy pressure |
|
|
Term
| How big in size is a white dwarf? What is its maximum mass? |
|
Definition
| Diameter = 1 Earth diameter. Mass < 1.4 Msun |
|
|
Term
| What is the ultimate fate of an isolated white dwarf? |
|
Definition
| will cool forever → Black Dwarf (none old enough yet) |
|
|
Term
| Will our Sun ever undergo a white dwarf supernova? |
|
Definition
|
|
Term
| What are black holes? What are their basic properties? |
|
Definition
| a collapsed star with such strong gravitational fields that even light cannot escape from it. Sphere from which NOTHING escapes. . . not even light !! MASSIVE gravity. |
|
|
Term
|
Definition
| Through the dying of giant stars when the fuel is exhausted. Gravity forces matter to fall into it's self and crush downward, until a singularity is created. |
|
|
Term
| What holds up a black hole against self-gravity? |
|
Definition
|
|
Term
| What is the event horizon of a black hole? How is its size related to the mass of a black hole? |
|
Definition
| When something becomes a black hole the mass is at the center. The event horizon is the radius within which gravity is so strong that light cannot escape. The closer you are to mass (middle) is infinity. |
|
|
Term
| When a star becomes a black hole, where does the star's mass go? |
|
Definition
| it goes to the very center of the black hole. |
|
|
Term
| How do we detect black holes? |
|
Definition
| by measuring its effects on objects around it. |
|
|
Term
| What is the maximum mass of a black hole? |
|
Definition
| There is no maximum mass. |
|
|
Term
| What happens to the appearance of an object as it falls into a black hole? |
|
Definition
| blue shifted..events happen faster because your sense of time is faster. |
|
|
Term
| Can you see out of a black hole? |
|
Definition
|
|
Term
| What kinds of particles fuse in fusion reactions? |
|
Definition
| protons, as well as other atomic nuclei |
|
|
Term
| When hydrogen fusion takes place, some of the ___ of the original ___ gets converted to ___? |
|
Definition
| mass, proton, energy (light) |
|
|
Term
|
Definition
| dark, cool patches on the sun where magnetic fields have suppressed heat flow from the interior. |
|
|
Term
| What makes a star a star? |
|
Definition
| big bag of gas w/ nuclear fusion reactions |
|
|
Term
| The sun is held up against gravity by? |
|
Definition
|
|
Term
| The sun gets energy from? |
|
Definition
|
|
Term
| The chemical composition of the sun is similar to? |
|
Definition
|
|
Term
|
Definition
|
|
Term
| The solar cycle is caused by? |
|
Definition
| the growth and decay of magnetic fields |
|
|
Term
| Most of the brightest stars are bright because? |
|
Definition
| they are intrinsically luminous but further |
|
|
Term
| Mea Parallax allows us to directly determine? |
|
Definition
|
|
Term
| A nearby stars parallax angle is measured by earthlings and jupiterlings whose angle is bigger? |
|
Definition
|
|
Term
| Stars parallax angle measured by earth and venus. How do they compare? |
|
Definition
|
|
Term
| Binary stars essential in determining stellar property of what? |
|
Definition
|
|
Term
| Stars with cooler surface temperature than sun, but more luminous must be? |
|
Definition
|
|
Term
| Where are the stars with the largest diameters? |
|
Definition
|
|
Term
| Where are the stars on the main sequence with shortest life time? |
|
Definition
|
|
Term
| Where on main sequence do stars have the shortest life? |
|
Definition
|
|
Term
| Where are the white dwarfs on the HR diagram? |
|
Definition
|
|
Term
| Where on the main sequence do stars have most mass? |
|
Definition
|
|
Term
| When stars burn hydrogen on the main sequence, where do the reactions occur? |
|
Definition
|
|
Term
| Presently, low mass stars burn hydrogen via _____ high mass ___ |
|
Definition
| Proton-Proton chain, CNO cycle |
|
|
Term
| The sun is about_____and is about_____its life |
|
Definition
| 5 billion years old, half |
|
|
Term
| After nuclear fuel has been used the core? |
|
Definition
|
|
Term
| The stellar remnant of a star like the sun becomes? |
|
Definition
|
|
Term
| Supernova’s are important because? |
|
Definition
| it expels our building blocks |
|
|
Term
| Hydrogen fusion occurs at____temp then helium? |
|
Definition
|
|
Term
| The stellar remnant of a star like the sun |
|
Definition
|
|
Term
| If the sun were somehow a BH earth would |
|
Definition
|
|
Term
| When a star becomes a BH, its mass goes |
|
Definition
| mass compresses to singularity at center |
|
|
Term
| What kind of pressure holds a black hole? |
|
Definition
|
|
Term
| If you shined a light from inside EH could we see it? |
|
Definition
|
|
Term
| Maximum mass of white dwarf? |
|
Definition
|
|
Term
| What happens when you push a white dwarf to its mass limit? |
|
Definition
|
|
