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A STAR IS BORN
Transcript of A STAR IS BORN
2. How are stars different and how are they classified by those differences?
Stars are different sizes and colors.
These different sizes and colors are how they are classified.
Stars are classified by their temperature and the elements they absorb.
There are seven main types of stars:
3. How do different types of stars evolve? (from birth to death)
All stars are born in clouds of gas and dust.
Once a star is formed, how long it exists depends on its size. The larger it is, the shorter its lifespan is.
Since stars live by fusing the hydrogen in their core, once it’s gone they get hotter and collapse in on themselves. The core becomes so hot it pushes the outer layers of the star outward, making them expand and cool, turning the star into a red giant.
As time passes, the star’s energy becomes unstable. What happens next depends on the size of the core.
Small stars become white dwarfs. They eject their outer layers and fade away as they cool off. They can also form a nova if they're near another.
A nova occurs when a white dwarf is close enough to a another star and uses its gravity to take its hydrogen, build up, and explode. The glow then fades and the cycle begins again.
Astronomical Terms | Infoplease.com http://www.infoplease.com/ipa/A0004425.html#ixzz2uYHJhoto
A STAR IS BORN
4. The different types of galaxies.
Elliptical galaxies are shaped like a spheroid, or elongated sphere. In the sky, where we can only see two of their three dimensions, these galaxies look like elliptical, or oval, shaped disks.
Spiral galaxies have three main components: a bulge, disk, and halo. The bulge is a spherical structure found in the center of the galaxy. This feature mostly contains older stars. The disk is made up of dust, gas, and younger stars.
The halo of a galaxy is a loose, spherical structure located around the bulge and some of the disk. The halo contains old clusters of stars, known as globular clusters. Spiral galaxies are classified into two groups, ordinary and barred.
Irregular galaxies have no regular or symmetrical structure. They are divided into two groups, regions of elemental hydrogen gas, and many Population I stars, which are young hot stars. Irr II galaxies simply seem to have large amounts of dust that block most of the light from the stars. All this dust makes is almost impossible to see distinct stars in the galaxy.
5. How does gravity affect stars and their formation?
When stars form, gravity pulls dust and gas in space into a cloud. As parts of the cloud become denser, gravity changes in those areas causing them to collapse in on themselves.
Once these fragments condense they start to form into protostars with their own unique gravity, which remains stable until their death. The larger a star is, the greater its center of gravity.
The reason stars don’t implode right away is due to gravity constantly pulling a star in on itself. This is countered by the outward pressure of the heated gases that make up stars, creating a balance between the opposing forces.
When nuclear fusion finally stops, a star's rate of pressure decreases until it's overcome by gravitational forces and implodes. The remnants of the star come together and the cycle begins again.
6. The size of the universe in general terms.
Imagine that our entire Solar System were the size of a quarter. And also imagine the Sun is speck of dust, as are its nine planets, whose orbits are represented by the flat disc of the coin
There is an edge to what we are able to see and could ever possibly seeing the universe.
We could never see a galaxy that is farther away in light travel time than the universe. the universe is old and estimated 14 billion or so years. Thus, we are surrounded by a "horizon" that we cannot see behind
7. About the Sun
The Sun is an overall average star as far as size and color. Specifically, it is classified as a yellow G type star which is a fairly common type of star. The Sun is made up of around 70% hydrogen, 28% helium and 2% of other elements like carbon and oxygen. The age of the Sun is unknown except for that scientists know that it is older than the Earth which is about 4.6 Billion years old.
In order to shine, a star must be hot, and it needs energy to maintain its heat.
Although this process actually works in proto-stellar clouds, it can't be useful to sustain a star : calculations show that, less than 25 million years ago, the Sun would have needed to be bigger than the Earth orbit.
Types of Star Evolutions cont.
Large stars die in a bigger explosion called a supernova. In a supernova, the star's core collapses and then explodes after building up too much mass. It goes on until electrons and protons combine to form neutrons, making a neutron star.
Neutron stars are very dense because they have so much mass packed in a small volume; this is what makes the gravitational pull of the star’s surface so immense. If the collapsed core doesn’t have enough mass to become a neutron star, it collapses to form a black hole.
A black hole is so strong that nothing can escape it, even light. Since it is impossible to see a black hole, we detect them using indirect observations. An example of an indirect observation is seeing the outer layers of a nearby star being pulled away from its center.
As matter goes into a black hole, it forms a disk superheated to massive temperatures, emitting x and gamma rays.
The dust and debris left behind by novae and supernovae eventually blend with the nearby gas and dust made as stars die. Eventually, those materials are recycled, and a new generation of stars and accompanying planetary systems form.
8.General terminology related to stars
: the theoretical end-product of the total gravitational collapse of a massive star or group of stars. Crushed even smaller than the incredibly dense neutron star, the black hole may become so dense that not even light can escape its gravitational field. In 1996, astronomers found strong evidence for a massive black hole at the center of the Milky Way. Recent evidence suggests that black holes are so common that they probably exist at the core of nearly all galaxies.
General terminology related to stars Cont.
: the alignment of two celestial objects at the same celestial longitude. Conjunction of the Moon and planets is often determined with reference to the Sun. For example, Saturn is said to be in conjunction with the Sun when Saturn and Earth are aligned on opposite sides of the Sun.
Elongation: the angular distance between two points in the sky as measured from a third point. The elongation of Mercury, for example, is the angular distance between Mercury and the Sun as measured from Earth. Planets whose orbits are outside Earth's can have elongations between 0° and 180°. (When a planet's elongation is 0°, it is at conjunction; when it is 180°, it is at opposition.) Because Mercury and Venus are within Earth's orbit, their greatest elongations measured from Earth are 28° and 47°, respectively.
General terminology related to stars Cont.
: gas and millions of stars held together by gravity. All that you can see in the sky (with a very few exceptions) belongs to our galaxy—a system of roughly 200 billion stars. The exceptions you can see are other galaxies. Our own galaxy, the rim of which we see as the “Milky Way,” is about 100,000 light-years in diameter and about 10,000 light-years in thickness. Its shape is roughly that of a thick lens; more precisely, it is a spiral nebula, a term first used for other galaxies when they were discovered and before it was realized that these were separate and distinct galaxies. Astronomers have estimated that the universe could contain 40 to 50 billion galaxies. In 2004, the Hubble Space Telescope and observers at the Keck Observatory in Hawaii discovered a new galaxy 13 billion light-years from Earth.
General terminology related to stars Cont.
: the eclipse of one celestial object by another. For example, a star is occulted when the Moon passes between it and Earth.
Opposition: the alignment of two celestial objects when their longitude differs by 180°. Opposition of the Moon and planets is often determined with reference to the Sun. For example, Saturn is said to be at opposition when Saturn and the Sun are aligned on opposite sides of Earth. Only the planets whose orbits lie outside Earth's can be in opposition to the Sun.
: an extremely dense star with a powerful gravitational pull. Some neutron stars pulse radio waves into space as they spin; these are known as pulsars.
: the path traveled by an object in space. The term comes from the Latin orbis, which means “circle” or “disk,” and orbita, “orbit.” Theoretically, there are four mathematical figures, or models, of possible orbits: two are open (hyperbola and parabola) and two are closed (ellipse and circle), but in reality all closed orbits are ellipses. Ellipses can be nearly circular, as are the orbits of most planets, or very elongated, as are the orbits of most comets, but the orbit revolves around a fixed, or focal, point. In our solar system, the Sun's gravitational pull keeps the planets in their elliptical orbits; the planets hold their moons in place similarly. For planets, the point of the orbit closest to the Sun is the perihelion, and the point farthest from the Sun is the aphelion. For orbits around Earth, the point of closest proximity is the perigee; the farthest point is the apogee. See also Retrograde.