Stars

Spiral galaxy (our Milky Way)

A spiral galaxy has a nucleus of bright stars and flattened arms that spiral around the nucleus. It contains billions of young stars, gas and dust

Identify the two variables used to identify stars on the H-R diagram

Luminosity (absolute magnitude) and temperature

What is Absolute magnitude?

The TRUE brightness of a star How bright the star would appear if all the stars were at a standard, uniform distance from Earth

What is Apparent magnitude?

The brightness of a star as seen from Earth Depends on both how much light the star emits and how far the star is from Earth The lower number on the scale means the brighter the star appears

During nuclear fusion what elements are created?

hydrogen and helium

What does the vertical axis on the Hertzsprung-Russell Diagram represent?

represents the star's luminosity or absolute magnitude.

Match the word on the left with the definition on the right. ____ 1. black dwarf a. star left at the core of a planetary nebula ____ 2. white dwarf b. a red super giant star explodes ____ 3. nebula c. what a medium-mass star becomes at the end of its life ____ 4. protostar d. a large cloud of gas or dust in space ____ 5. supernova e. exerts such a strong gravitational pull that no light escapes ____ 6. neutron star f. the earliest stage of a star 's life ____ 7. black hole g. the remains of a high mass star

1. c 2. a 3. d 4. f 5. b 6. g 7. e

Low Mass Star life cycle: ____ 1. Red giant -a ____ 2. Where fusion begins-b ____ 3. Nebula-c ____ 4. Black dwarf-d ____ 5. The stage the sun is in-e ____ 6. White dwarf-f ____ 7. Planetary Nebula-g

1. c 2. b 3. e 4. a 5. g 6. f 7. d

High Mass Star ____ 1. Black Hole-a ____ 2. Supernova-b ____ 3. Protostar-c ____ 4. Gravity causes this to condense into a protostar-d ____ 5. Main sequence star-e ____ 6. When a star begins to run out of fuel and grows larger-f ____ 7. Neutron star-g

1. d 2. c 3. e 4. f 5. b 6. g 7. a

What is dark matter?

23% of the universe Does not give off light Has gravity

What is dark energy?

73% of the universe Opposes gravity

How do scientists determine the composition and temperature of stars?

?

What is the life cycle of stars?

All stars start as a nebula. A nebula is a large cloud of gas and dust. Gravity can pull some of the gas and dust in a nebula together. The contracting cloud is then called a protostar. A protostar is the earliest stage of a star's life. A star is born when the gas and dust from a nebula become so hot that nuclear fusion starts. Once a star has "turned on" it is known as a main sequence star. When a main sequence star begins to run out of hydrogen fuel, the star becomes a red giant or a red super giant. THE DEATH OF A LOW OR MEDIUM MASS STAR After a low or medium mass or star has become a red giant the outer parts grow bigger and drift into space, forming a cloud of gas called a planetary nebula. The blue-white hot core of the star that is left behind cools and becomes a white dwarf. The white dwarf eventually runs out of fuel and dies as a black dwarf. THE DEATH OF A HIGH MASS STAR A dying red super giant star can suddenly explode. The explosion is called a supernova. After the star explodes, some of the materials from the star are left behind. This material may form a neutron star. Neutron stars are the remains of high-mass stars. The most massive stars become black holes when they die. After a large mass star explodes, a large amount of mass may remain. The gravity of the mass is so strong that gas is pulled inward, pulling more gas into a smaller and smaller space. Eventually, the gravity becomes so strong that nothing can escape, not even light.

why are blue super giants so much more rare than red super giants?

Blue giants are much rarer than red giants, because they only develop from more massive and less common stars, and because they have short lives in the blue giant stage.

what stars are the hottest? Coolest?

Blue stars are the hottest. Red stars are the coolest.

What is the color range of stars from hottest to coolest?

Blue, Blue-white, White, Yellow-white, yellow, orange, red

What does the Hertzsprung-Russell Diagram show?

It is a tool that shows relationships and differences between stars. It is something of a "family portrait." It shows stars of different ages and in different stages, all at the same time. It also illustrates the relationship between the absolute magnitude and the surface temperature of stars. As stars evolve, their position on the Hertzsprung-Russell diagram moves. In the diagram each star is represented by a dot. There are lots of stars out there, so there are lots of dots. The position of each dot on the diagram tells us two things about each star: its luminosity (or absolute magnitude) and its temperature.

Explain what happens to helium and the outer layers of a star in the planetary nebula stage.

It is red because it is cooler than it was in the main sequence star stage and it is a giant because the outer shell has expanded outward. In the core of the red giant, helium fuses into carbon. ... As the core collapses, the outer layers of the star are expelled. A planetary nebula is formed by the outer layers. https://imagine.gsfc.nasa.gov/educators/lessons/xray.../background-lifecycles.html

Identify the major factor that controls a star's evolution and lifespan.

Its size or mass

Explain what is happening during the main sequence stage of a star.

Main sequence stars fuse hydrogen atoms to form helium atoms in their cores. https://www.space.com/22437-main-sequence-stars.html

Irregular Galaxy

No particular shape, low total mass, rich in dust and gas There are not many of this type

What are quasars?

Quasar: quasi-stellar radio source; a very luminous object that produces energy at a high rate Related to galaxies not stars The most distant objects that have been observed from Earth Pushing galaxies apart The universe is expanding and the rate of expansion also seems to be accelerating

What is Cosmic background radiation?

Radiation uniformly detected from every direction in space; A remnant of the big bang

Why are Red Super Giant stars very bright but not hot?

Red Super Giants stars have an exhausted supply of hydrogen in their cores and have begun thermonuclear fusion of hydrogen in a shell surrounding the core. They have radii tens to hundreds of times larger than that of the Sun. https://en.wikipedia.org/wiki/Red_giant

Which type of star is the most common?

Red dwarfs

what is a spectrograph?

Spectrograph is a device used to measure the light that the stars emit It separates light into different colors or wavelengths. The colors & lines of spectrum of a star indicate the elements that make up the star. Most common elements are hydrogen and helium.

Types of galaxies

Spiral, irregular, elliptical

life cycle of stars?

Stellar nebula Average star or Massive star Red giant Red super giant Planetary Nebula Supernova White dwarf Neutron star or black hole

how do you know the surface temp. of a star?

Surface temperature of a star is indicated by the star's color.

What galaxy is Earth in? What is the name of this galaxy?

The Milky Way

What does the horizontal axis on the Hertzsprung-Russell Diagram represent?

The horizontal axis represents the star's surface temperature. Usually this is labeled using the Kelvin temperature scale. On this diagram, the higher (hotter) temperatures are on the left, and the lower (cooler) temperatures are on the right.

Elliptical galaxy

These galaxies vary in shape from nearly spherical to very elongated. They are extremely bright in the center, contain few young stars and very little dust and gas

What is The Role of Black holes in Center of Galaxies?

Today most scientists believe that super massive black holes at the galactic centers are the "engines" that power the quasars.

Differentiate between a red shift and blue shift.

When an object moves away from us, the light is shifted to the red end of the spectrum, as its wavelengths get longer. If an object moves closer, the light moves to the blue end of the spectrum, as its wavelengths get shorter. https://www.space.com/25732-redshift-blueshift.html

Why are White Dwarf stars very hot but not very bright?

White dwarfs are stars that have burned up all of the hydrogen they once used as nuclear fuel. Fusion in a star's core produces heat and outward pressure, but this pressure is kept in balance by the inward push of gravity generated by a star's mass. https://www.nationalgeographic.com/science/space/universe/white-dwarfs/

what is a Star?

a ball of gas that gives off tremendous amount of electromagnetic energy

Galaxy:

a collection of stars, dust and gas bound together by gravity Galaxies are the major building blocks of the universe!

Tell why and when stars move out of the main sequence stage

a main sequence star burns through the hydrogen in its core, reaching the end of its life cycle. At this point, it leaves the main sequence. https://www.space.com/22437-main-sequence-stars.html

Barred Galaxy (not a type of galaxy!)

a spiral galaxy with a central bar-shaped structure composed of stars a spiral galaxy with a band of bright stars emerging from the center and running across the middle of the galaxy

The stages below are not in the right order. Number the stages in the correct order. _____ a. The star begins to run out of fuel and expands into a red giant or red super giant. _____ b. Stars start out as diffused clouds of gas and dust drifting through space. A single one of these clouds is called a nebula _____ c. What happens next depends on the mass of the star. _____ d. Heat and pressure build in the core of the protostar until nuclear fusion takes place. _____ e. The force of gravity pulls a nebula together forming clumps called protostars. _____ f. Hydrogen atoms are fused together generating an enormous amount of energy igniting the star causing it to shine.

a. 4 b. 1 c. 6 d. 3 e. 2 f. 5

List the two major elements found in stars.

hydrogen and helium

What two things make up most of the universe?

hydrogen and helium

What are Ripples?

irregularities in the cosmic background radiation where the temperature differs The ripples may indicate the first stages in the formation of the universe's galaxies.

what are Pulsars?

rapidly spinning neutron star that emits pulses of radio and optical energy across space

Identify when the birth of a star begins.

stellar nebula

What does Luminosity mean?

the total amount of energy a star gives off each second

Explain how the color and temperature of stars relate.

the wavelength of light where a star's emission is concentrated is related to the star's temperature - the hotter the star, the more blue it is; the cooler the star, the more red it is. curious.astro.cornell.edu/.../stars...star...stars/389-what-can-we-learn-from-the-color-of-a...