Astronomy Exam – Flashcards

billions of light-years away

Elliptical galaxies contain less dust and cool gas than spiral galaxies. Elliptical galaxies are redder than spiral galaxies. Spiral galaxies have more young stars than elliptical galaxies. Elliptical galaxies are generally smaller than spiral galaxies.

Irregular galaxies

Elliptical

a relationship between the rotation speed of a spiral galaxy and its luminosity

best standard candle for long distances

Curtis and Shapley

He observed Cepheid variables in the galaxy

galaxy recession velocity and distance

redshifts of bright objects in galaxies

Matter is evenly distributed throughout the universe.

the age of the universe.

It causes the wavelength of light to increase.

spiral and barred spiral

elliptical and irregular

elliptical

elliptical

any object whose luminosity is known independently from its apparent brightness

white dwarf supernovae

whether they were nebulae located in the Milky Way, or spiral galaxies located far outside our galaxy

He found Cepheid variables in them that looked very faint

galaxies move away from each other, and that the velocity with which they recede is proportional to their distance. It leads to the picture of an expanding universe and, by extrapolating back in time, to the Big Bang theory.

They take the distance to any galaxy and divide it by its speed of recession (time = distance/velocity).

Space itself is expanding.

when it was younger and when the whole universe was younger.

twice as far away as Galaxy B.

halo

about 28,000 light-years from the center, in the disk

1000 light-years

230 million years

atomic hydrogen gas

radiation from supernova explosions

the recycling of stellar material from stars into the interstellar medium which then forms new stars

molecular clouds

hot bubbles

x rays

preferential scattering of blue light from dust grains

spiral arms

in the protogalactic cloud

4 the large and small Magellanic Clouds, the Canis Major dwarf galaxy, and the Sagittarius dwarf galaxy

3 million solar masses

about 4 years

about 100,000 years

The blue color is due to the scattering of light by interstellar dust grains and the red color arises from hydrogen emissions.

supernova remnant planetary nebula emission/ionization nebula reflection nebula

spiral barred spiral elliptical irregular peculiar

Crab Nebula explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar material it sweeps up and shocks along the way.

Ring Nebula emission nebula consisting of an expanding, glowing shell of ionized gas ejected from old red giant stars late in their lives.

Orion Nebula PINK Emission nebulae are clouds of ionized gas that, as the name suggests, emit their own light at optical wavelengths.

Pleiadies Nebula reflection nebulae are clouds of interstellar dust which reflect the light of a nearby star or stars. The energy from the nearby stars is insufficient to ionize the gas of the nebula to create an emission nebula, but is enough to give sufficient scattering to make the dust visible

Bulge Disk Halo Spiral galaxies consist of a flat, rotating disc containing stars, gas and dust, and a central concentration of stars known as the bulge. These are surrounded by a much fainter halo of stars, many of which reside in globular clusters.

barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in approximately two-thirds of all spiral galaxies. Bars generally affect both the motions of stars and interstellar gas within spiral galaxies and can affect spiral arms as well.

Oval Smooth Blurred light An elliptical galaxy is a type of galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless brightness profile. Unlike flat spiral galaxies with organization and structure, they are more three-dimensional, without much structure, and their stars are in somewhat random orbits around the center.

An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy.The shape of an irregular galaxy is uncommon - they do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure.

The model accounts for the fact that the universe expanded from a very high density and high temperature state, and offers a comprehensive explanation for a broad range of phenomena, including the abundance of light elements, the cosmic microwave background, large scale structure and Hubble's Law

1. Hubble's Law 2. The Cosmic Microwave Background Radiation 3. Nucleosynthesis ( Abundances of Deuterium and Helium)

The cosmic microwave background (CMB) is the thermal radiation left over from the time of recombination in Big Bang cosmology

Abundances of Deuterium and Helium Big Bang nucleosynthesis refers to the production of nuclei other than those of the lightest isotope of hydrogen during the early phases of the universe. It is believed by most cosmologists to have taken place from 10 seconds to 20 minutes after the Big Bang, and is calculated to be responsible for the formation of most of the universe's helium along with small amounts of the hydrogen isotope deuterium, the helium isotope helium-3 and a very small amount of the lithium isotope lithium.

-a flat Universe (Euclidean or zero curvature) - a spherical or closed Universe (positive curvature) -hyperbolic or open Universe (negative curvature)

, the density of matter in the expanding universe remains unchanged due to a continuous creation of matter, thus adhering to the perfect cosmological principle, a principle that asserts that the observable universe is basically the same at any time as well as at any place

atomic hydrogen gas