astronomy I finals review

stellar nucleosynthesis

the process of element formation that relies on nuclear fusion

nuclear fusion

when two simpler nuclei form a bigger nucleus and some of their mass converts to energy. powers stars and creates most elements in universe

nebula

a large cloud of gas and dust in space where stars form. Gravity causes parts of it to collapse and clump together.

protostar

As gas collapses, it heats up and forms this — a young, forming star that has not yet begun fusion.

main sequence

When the core becomes hot enough for nuclear fusion to start, hydrogen fuses into helium. The star enters the main sequence phase, where it spends most of its life in equilibrium between gravity and pressure. (90% of stars)

red giant/ supergiant

When hydrogen runs out, the star expands into a red giant (if medium-sized) or red supergiant (if massive). The star begins fusing helium and heavier elements in its core.

core collapse and final stages

Eventually, gravity overcomes the outward force of fusion and the star core collapses and ejects its outer layers that form planetary nebula. For low-mass stars (like the Sun): The outer layers drift away, leaving behind a white dwarf. The star’s remaining energy slowly fades over time. For high-mass stars: The core collapses violently, causing a supernova explosion. The core may become a neutron star or a black hole, depending on its mass

solar system formation

Forming 4.5 billion years ago from a cloud of gas and dust called a solar nebula. Gravity caused the nebula to collapse and spin. A massive collection of gas and dust accumulated in the center. When it was massive enough it would undergo nuclear fusion and create the Sun. The additional material clumped together to form planets, dwarf planets, asteroids, and moons.

asteroids

solid rocky or metallic bodies that independently orbit the Sun. A large percentage of the known asteroids are between Mars and Jupiter

comets

“dirty snowball” mainly composed of solids that easily change to gas when heated. As the solids melt they leave behind a trail known as a comet's trail

oort cloud

spherical shell of icy objects in the outermost reaches of the Solar System. Thought to be the origin of most long-period comets

meteorites

a rock that leaves a visible streak as they pass through our atmosphere and strike Earth A.k.a shooting stars

keplers first law

a planet has an elliptical shaped orbit around the sun. closest point to sun is perihelion and farthest is aphelion. if eccentricity 0, circle, if 1 very eccentric.

keplers second law

planets move faster when closer to the sun (at the perihelion)

keplers third law

distance from sun impacts orbital period. further a planet is from the sun, the longer one year will be.

evidence of big bang theory

The colors of lights from stars and galaxies (their spectra)

2. The stretching of light from distant galaxies (redshift)

3. Galactic motions

4. The composition of matter

5. Leftover radiation from the early universe

○ Also known as, Cosmic Background Radiation (CMB)

light spectra

When light passes through a prism (or diffraction grating), it spreads out into a pattern of colors called a spectrum. Each element absorbs or emits light at certain wavelengths, creating its own unique pattern of lines called spectral lines. Each element gives off its own unique pattern of colors, like a barcode. These lines show which elements are present in a star or galaxy. By comparing spectral lines from galaxies to those from elements on Earth, astronomers can better determine differences in environment, age, motion, and physical characteristics.

Electromagnetic Energy

- energy that is radiated through space in the form of transverse waves.

doppler effect

the apparent wavelength shifting of electromagnetic energy caused by the relative motion between the energy source and the observer

redshift

as galaxies move farther away from the observer light waves stretch out and shift towards the red end of the spectrum

blue shift

observed when a celestial body is moving closer to the observer light waves compress and shift towards the blue end. (rarely observed)

galactic motions

Galaxies are not staying still – most are moving away from each other. Also known as, Cosmic Expansion

hubble constant

rate of expansion of the universe

big bang nucleosynthesis

the creation of the first atomic nuclei from protons and neutrons as the universe cooled. In the first few minutes, the universe was hot and dense enough for simple nuclei to form.

background radiation

left over energy created by the big bang found in all parts of the universe. Scientists have found evidence of long wave radiation [microwave] that come from all directions in the Universe