Astronomy Quiz on Galaxies and Cosmology

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Questions and Answers

What phenomenon allows us to observe the galactic center despite the obscuring gas and dust?

Infrared radiation

Visible light

Ultraviolet light

Gamma rays and radio waves (correct)

What is the shape of the rotation curve expected based on Keplerian orbits?

It remains constant with distance

It decreases with distance (correct)

It increases with distance

It flattens out with distance

Which classification of galaxies has tightly wound arms according to the Hubble Tuning Fork?

Barred Spiral SBb

Spiral Sa (correct)

Irregular

Elliptical EO-E7

What is one proposed solution to the missing mass problem in galaxies?

Small brown dwarf stars in the galactic halo Signup and view all the answers

Who confirmed the existence of external galaxies through the use of Cepheid variables?

Edwin Hubble Signup and view all the answers

Which type of galaxy typically has little to no gas and dust?

Elliptical Signup and view all the answers

What is the primary cause of spiral arms in galaxies?

Gravitational density waves Signup and view all the answers

What is the estimated mass range of spiral galaxies in solar masses?

$10^9$ to $4 imes 10^{11}$ Signup and view all the answers

What method uses the apparent size of a galaxy to estimate its distance?

Apparent Size Signup and view all the answers

What is the approximate value of Hubble's constant?

65 km/sec/Mpc Signup and view all the answers

What are supernovae primarily used for in astronomy?

Determining distances to galaxies Signup and view all the answers

Which shape of the universe suggests it will expand forever but not accelerate?

Flat Signup and view all the answers

During which era did the strong force split off to establish three fundamental forces?

Electro-Weak Era Signup and view all the answers

What event occurs approximately 3 minutes after the Big Bang?

Formation of helium Signup and view all the answers

What does the term 'Inflationary Epoch' refer to?

A rapid expansion of the universe Signup and view all the answers

What kind of universe will accelerate indefinitely into the future?

Hyperbolic Signup and view all the answers

Which notable phenomenon did Penzias and Wilson observe that supports the Big Bang theory?

Cosmic microwave background radiation Signup and view all the answers

What aspect of the universe does Einstein's equations of General Relativity reveal?

Possible shapes of the universe Signup and view all the answers

What characterizes rich clusters of galaxies?

They have thousands of member galaxies. Signup and view all the answers

What does Hubble's Law describe?

The relationship between recessional velocity and distance of galaxies. Signup and view all the answers

What is the current value of Hubble's constant approximately?

65 km/sec/Mpc Signup and view all the answers

Which method is deemed the most accurate for determining distances to galaxies?

Supernovae Signup and view all the answers

What shape does a hyperbolic universe imply?

It will continue to accelerate outward. Signup and view all the answers

Which era occurred immediately after the Big Bang?

Planck Era Signup and view all the answers

What phenomenon did Penzias and Wilson observe that supports the Big Bang theory?

3 Kelvin background radiation Signup and view all the answers

Which of the following descriptions fits a flat universe?

It expands forever without acceleration. Signup and view all the answers

What determines the distances to galaxies using apparent size?

Smaller apparent size indicates greater distance. Signup and view all the answers

At time T=0 in the history of the universe, what was contained in the initial point?

Time and matter Signup and view all the answers

What is the composition of a galaxy?

A collection of stars, gas, and dust Signup and view all the answers

What was William Herschel's incorrect belief about the Solar system's location?

At the center of the Milky Way Signup and view all the answers

What is the relationship used by Harlow Shapley to estimate distances to globular clusters?

$M = m - 5 ext{log}(d) + 5$ Signup and view all the answers

Which component of the galaxy does interstellar gas and dust obscure?

The galactic center Signup and view all the answers

Which type of star is classified under Population I?

O and B stars Signup and view all the answers

How is tangential velocity of a star calculated?

$T = 4.7 rac{m}{d} rac{km}{sec}$ Signup and view all the answers

What does the Local Standard of Rest (LSR) represent?

The average speed of stars in the local vicinity Signup and view all the answers

What is the approximate mass of the galaxy compared to the Sun?

$9.4 imes 10^{10} M_{sun}$ Signup and view all the answers

What allows the measurement of speeds around the galactic center?

Doppler shifts of spectral lines Signup and view all the answers

Study Notes

Hubble's Constant

To determine Hubble's constant (H₀), Hubble needed to measure distances to a large number of galaxies for which he had spectra (thus velocities).
He then plotted recessional velocity versus distance, and the slope of a line fit to the data is the value of H₀.
Problem: How do you determine distances to distant galaxies?

Methods of Determining Galactic Distances

The size galaxies appear: The smaller they look, the further they must be.
The brightness of HII regions: The brighter they appear, the closer they are.
Supernovae: Most accurate method.

The Big Bang Theory

The universe started as an infinitely small point 15 billion years ago.
Time expanded outward, carrying galaxies, gas, and dust.
Predicts observed 3° Kelvin background radiation by Penzias and Wilson.
Solutions of Einstein's equations of General Relativity for a homogeneous, hyperbolic (saddle-shaped), or flat universe.

Shapes of the Universe

Spherical: The universe would eventually collapse back on itself. Parallel lines will eventually intersect, the sum of angles in a triangle are greater than 180°.
Flat: The universe will expand forever, but not accelerate. Parallel lines remain parallel, angles in a triangle always equal 180°.
Hyperbolic: The universe accelerates outward. Parallel lines will eventually diverge, interior angles in a triangle add to less than 180°.

History of the Universe

Universe, space, time, matter, and energy all contained in an infinitesimally small point.
Planck Era: Need quantized gravity to know what happened here.
Grand Unified Field Era: No normal atoms, strong force, weak force and electromagnetic force are all one force here.
Electroweak Era: The strong force splits off, so there now 3 fundamental forces: gravity, strong, and electro-weak. Elementary particles form.
Electromagnetic and weak forces separate: Particle era
Nucleo-synthesis Era: Protons, neutrons form first atoms, and H forms helium.
Radiation Era: Atoms now form part of radiation era (photons become free). Radiation cools the universe expands, atoms are free to pick up electrons, form complete atoms, forming stars and galaxies.
Inflationary Epoch: There was a time early on (10⁻³⁵ sec) when the universe expanded faster than the speed of light. This is necessary to explain observations of the background radiation.

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Description

Test your knowledge on galaxies and cosmological concepts with this quiz. Explore topics such as galactic centers, galaxy classification, and the expansion of the universe. Perfect for students of astrophysics or anyone interested in the mysteries of the cosmos.