Astronomy Final

Brown dwarf

"Failed stars"; not massive enough to begin fusion of hydrogen

8. Describe the life cycle of a sun-like star, from birth to death.

-Interstellar cloud contracts via gravity -Fragments emerge and collapse until cloud is so dense radiation cannot escape -Protostar photosphere forms and continues to collapse, planets begin to form -Newborn star, fusion begins, still contracting a bit Main Sequence Star, hydrostatic equilibrium longest part of star's lifetime

7. Sketch an H-R diagram. What are the different regions on the H-R diagram? How does a star move through the H-R diagram through its life?

-OBA area is hot -GKM area is cool -Bottom of the graph is dim -Top of the graph is bright A star stays the same spectral type for the entirety of its main sequence phase

16. Why are heavier elements (such as carbon, oxygen, neon, etc) formed in the cores of large mass stars but not small mass stars?

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17. Why aren't elements heavier than iron formed in the cores of stars via fusion?

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9. Describe the life cycle, from birth to death, of a star that is greater than 10 times more massive than the Sun

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Satellite

A body that orbits another body, can be artificial or natural

Protostar

A dense core of a collapsing cloud fragment, a star "embryo"

2. What differentiates a dwarf planet from an asteroid?

A dwarf planet is "a celestial body in direct orbit of the Sun that is massive enough for its shape to be controlled by gravitation. An asteroid is a large chunk of rock that orbits around the sun, also known as planetoids or minor planets.

Planet

A large body in space that orbits a star and does not produce light of its own

Kuiper belt

A region outside the orbit of Neptune containing dwarf planets and smaller objects

Meteor

A streak of light in the sky produced by the burning of a meteoroid in Earth's atmosphere.

Solar system

A system comprising the sun (or another star) and the satellites that orbit it (directly or indirectly)

Supernova

A very bright "explosion" of a dying high-mass star that releases tremendous amounts of radiation

Red giant

A very large, red star, stage after the main sequence; found in the upper right part of the HR diagram

Dwarf planet

An object that is smaller than a planet, but is not a satellite of another planet

1. Why do all of the planets orbit the Sun in the same plane (i.e. why is the solar system flat)?

Angular momentum. Most planets, objects in the asteroid belt and the Kuiper Belt orbit in the ecliptic (same plane as the sun)

Asteroid belt

Area between Mars and Jupiter containing most asteroids in the solar system

4. Why were dwarf planets made into a separate group of solar system objects?

Dwarf planets are too small to be considered full planets, but too big to fit in

Differentiation

Gravity causes more dense materials to sink towards the center

11. How are stars formed in nebulae?

If the gas in a nebula is dense and the temperature us high enough, stars will begin forming in the nebula

Jovian planet

Jupiter, Saturn, Uranus, Neptune

6. Explain the nebular theory and condensation theory. Use these terms to describe how a solar system forms around a new star

NB does not account for why the dust/gas in the disk would clump together to make planets. If NB was the only process involved, the solar system would smooth out with no clumps. CT: dust particles accumulate more atoms and molecules from gas. Dust is cool, so warm gas cools off and allows more dust/gas to collect

13. How can HR diagrams be used to determine the age of a cluster of stars?

Stars that begin to form start in the zero age main sequence which is in the middle of the diagram. Then they start moving into the turnoff where the main sequence terminates. Only stars less massive than the sun remain in the main sequence

3. What are major differences between terrestrial planets and Jovian planets?

Terrestrial planets are made of solid surfaces, the jovian planets are made of gaseous surfaces. Terrestrial: smaller, denser than jovian, orbit close to the sun, few moons. Jovian: larger, orbit far from the sun, many moons, rings, less dense

Hydrostatic equilibrium

The balance of outward thermal pressure with inward gravitational force

10. How does the life of a large star differ from a small star?

The bigger the star, the shorter the lifespan

Condensation theory

The idea that cool interstellar dust is the thing that makes planets form in the solar nebula

White dwarf

The leftover core of a star after the outer layers have been blown off during the red giant phase

Terrestrial planet

The name given to the four inner planets: Mercury, Venus, Earth, and Mars

Accretion

The process by which a clump of material grows into a large object by collision and sticking

Nebular theory

The theory that planets form in the solar nebula disk around a protostar

14. Why is a brown dwarf known as a "failed star" and not an extremely large planet?

They're very cool and dim. Not even hot enough to star fusion. Never evolve past the protostar stage

Black hole

a region of space having a gravitational field so intense that no matter or radiation can escape.

Moon

a small body in orbit around a planet

18. Why is supernova 1987a important?

astronomers could watch a supernova occur in real time and knew exactly which star erupted

15. Why do more massive blue main sequence stars have shorter lifespans than less massive red main sequence stars?

blue main sequence stars are already at their luminosity peak and go into the turnoff

Globular Cluster

closely-packed; lower abundance of heavy elements than the sun; found in galactic halo

Planetary nebula

gas blown off of a red giant as the inner core becomes unstable; gas is lit by light from the dying core

5. What is the difference between a meteor and an asteroid?

meteor: a streak of light in the sky. Asteroids are small, rocky objects that orbit the sun.

12. How do globular clusters differ from open clusters?

open clusters are the remnants of bursts of star formation, while globular clusters are the remains of the cores of small galaxies eaten by the Milky Way.

Open cluster

spaced out stars; 100s of stars per cluster; found in galactic plane

Astronomical unit (AU)

the average distance between Earth and the sun

Neutron star

the small, dense remains of a high-mass star after a supernova

Supernova remnant

very hot radiating dust, gas, and other particles leftover from a supernova