Astrophysics

Featured Answers

Astrophysics Basics

• The Electromagnetic Spectrum
• Blackbody Radiation
• Luminosity, Effective Temperature, Flux and Magnitudes
• Blotzmann and Saha Equations
• Spectral Classification of Stars
• The Hertzsprung-Russell Diagram

Stellar Formation

• Hydrostatic Equilibrium
• Free-Fall Times
• Pre-Main-Sequence Evolution
• Star Formation Theories

Radiative Transfer in Stars

• Radiative Opacities and Matter-Radiation
• Specific Intensity and Radiative Moments
• Radiative Transfer Equation
• Local Thermodynamic Equilibrium
• Radiative Equilibrium
• Roseland and Other Mean Opacities
• Schwarzschild-Milne Equations
• Radiative Acceleration of Matter and Pressure

Stellar Atmosphere

• The Grey Atmosphere
• Line Opacities and Broadening
• Equivalent Width and Formation of Atomic Lines
• Atmospheric Modelling

Stellar Interiors

• Equations of Stellar Structure
• Energy Transport in Stars
• Polytropic Models
• Structure of the Sun
• Variable Stars and Asteroseismology

Nucleosynthesis and Stellar Evolution

• Nuclear Fusion
• Models of the Nucleus
• Main-Sequence Burning
• Helium-Burning Phase
• Advanced Nuclear Burning
• Evolutionary Tracks in the H-R Diagram
• Stellar Clusters
• Stellar Remnants
• Novae and Supernovae

Chemically Peculiar Stars and Diffusion

• Chemically Peculiar Stars
• Atomic Diffusion Theory
• Radiative Accelerations
• Transport Mechanisms

General Relativity

• Gravity Waves
• Black Holes
• Relativistic Orbits
• Space-Time

Universe Formation

• Planet Composition
• Galaxy Composition
• Nebulae Composition
• Big Bang and Universe Evolution

Uncategorized Questions

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• Why is Earth's acceleration usualIy very small compared to the acceleration of the object that Earth interacts with?
• Spaceships that travel millions of miles into outer space use very little fuel. How can they go so far on so little fuel?
• How does an alteration in eccentricity of the orbit affect the elliptical and circular nature of it?
• What relationship exists between the speed of the galaxies moving apart and their initial distances from one another?
• Does the mass and size of the Earth change over time?
• How does a rocket move through space? What are the forces responsible for moving the rocket?
• If the mass of a satellite orbiting the earth were to increase, what would happen to that satellite?
• How does gravity keep a planet moving in an orbit around the sun?
• Will a planet or comet be moving faster in its orbit when it is farther from or closer to the sun?
• When a spinning star shrinks in radius, it speeds up. Why does this happen?
• Which law explains how rockets are launched into space?
• Why do astronauts in space experience less gravitational force than they do on earth?
• How is the Doppler Effect used to measure the distance a stellar object is away from Earth?
• What is the centripetal force that holds planets in orbit?
• The planet Jupiter is about 300 times as massive as Earth, but an object on its surface would weigh only 2.5 times as much as it would on Earth. Why?
• Mimas, a moon of Saturn has an orbital radius of #1.87 * 10^8# #m#. What is the orbital period?
• What is the velocity of a satellite moving in a stable circular orbit about the Earth at a height of 3600 km?
• What keeps a satellite up in its orbit about the Earth?
• On the surface of Earth, a spacecraft has a mass of #2.00 * 10^4# kilograms. What is the mass of the spacecraft at a distance of one Earth radius above Earth's surface?
• What is the gravitational force that the Sun exerts on Jupiter?
• Why don't satellites in orbit fall to the ground? Why don't they fly off into space?
• What two motions combine to produce an orbit?
• How does the moon accelerate as it orbits the Earth?
• A satellite is put in a circular orbit about Earth with a radius equal to one-half the radius of the Moon's orbit. What is its period of revolution in lunar months?
• The Martian satellite Phobos travels in an approximately circular orbit of radius #9.4 * 10^6# #m# with a period of #7# #h# #39# #min#. What is the mass of Mars?
• What is asteroseismology?
• What is the study of asteroseismology? Why do astrophysicists study this field?
• What is the difference between astrophysics and astrobiology?
• Who founded astrobiology? Who are some other major astrobiologists?
• Does the study of astrophysics include astrochemistry?
• What are astrophysics, astrochemistry and astrobiology?
• Why is astrochemistry important?
• What is linear opacity?
• What are the four main classes of chemically peculiar stars? How is their classification determined?
• How are chemically peculiar stars identified?
• How hot are chemically peculiar stars in comparison to main sequence stars?
• How do you measure time in space?
• Do hydrodynamics apply in space?
• What is electromagnetic radiation and how does it relate to the electromagnetic spectrum?
• A rocket ship leaves Earth's atmosphere its initial velocity is less than its final velocity. What is this an example of?
• How can you tell if a satellite dish is tracking a satellite in a low-Earth orbit or a geosynchronous orbit?
• When the Moon orbits Earth, what is the centripetal force?
• If the Moon moved farther away from Earth, what would happen to the gravitational force between Earth and the Moon?
• A satellite in a circular orbit experiences a centripetal acceleration of #8.62# #m##/s^2#. The tangential speed of the satellite is #7.65 * 10^3 m##/s#. What is the altitude of the satellite?
• What was Einstein's equation, and what did it tell us about Big Bang?
• Why does adding a second planet affect the orbit of the first planet?
• What is the speed of a satellite moving in a stable circular orbit about the Earth at a height of 4000 km?
• What does the Doppler Effect tell astronomers about the universe?
• The radius of the moon's orbit about the Earth is about #3.6 * 10^8# #m#. The moon's period is #2.3 * 10^6# seconds. What is the centripetal acceleration of the moon?
• If the average distance between Earth and the Sun were doubled, what changes would occur in the sun's gravitational pull on Earth and Earth's period of revolution?
• Is there any probability that dark matter is either made of 3 neutrons bound together or it can be neutronium?
• How much energy is required to release one photon?
• How long does it take for a GPS signal to get to earth?
• Time travels faster than light. Light has a mass of 0 and according to Einstein nothing can move faster than light if it doesn't have its weight as 0. Then why does time travel faster than light?
• What are the implications of the study of the supernovas that show the universe is increasing its rate of expansion? Why do scientists oppose the idea of an open universe?
• What forces keep a planet in orbit and how does each one work on the planet?
• Why hasn't the discovery in 1998 of the increasing rate of the expansion of the universe had a bigger effect on the philosophies of science and astronomy?
• What is meant by Apogee and perigee,Eccentricity? How do we Calculate them?
• What causes some scientists to be so sure that Oort belt exists when there is no direct evidence of the Oort belt of comets?
• The space shuttle, Endeavor, is launched to altitude of 500 km above the surface of the earth. The shuttle travels an average rate of 700 m/s. How long will it take for Endeavor to reach its orbit?
• What would happen if a gamma ray burst hit the Earth?
• Question #55254
• Question #5a9ba
• Question #3e70f
• Question #e192b
• What are effects of the strong gravitational forces found holding the mass of the Sun together?
• Question #7ba36
• Stephen Hawking said that the early universe expanded faster than light, how this possible if nothing can travel faster than light?
• What is negative energy and can black holes lose mass?
• What fusion reactions other than Hydrogen are important in stars?
• What happens in Earth's interior to produce Earth's magnetic field?
• Why are planetary orbits elliptical and why do bodies in a solar system orbit the center of mass and nit the star itself?
• Why are stars generally several light years apart except in binary star system, etc.?
• ```why does red light travel faster than violet light , though violet light has more energy (in glass)? plz give a simple answer which can be understood by a 10th class student.
• Question #1f381
• What is antimatter, and what are some of it's properties?
• Question #f510d
• Question #3d262
• Question #29853
• How are Gluons Made??
• Why the speed of light is constant in every reference point?Train going with a speed of 200m/sec emitting light from the front of it,then there the speed of light would be 300000200m/sec but there also the speed of light is constant (300000000m/sec)
• Question #ca73e
• How far apart would two Earth sized planets have to be to have the same effect as the Moon on the Earth?
• Why photon doesn't have antiparticle?
• How can we verify the 3 consequences of relativity?
• Question #ff2e0
• Question #78a66
• Question #b0e7d
• What is anti- particle ? And what is its relation with black hole or some outer space things like that.
• What happens to the mass of a star which collapses into a black hole?
• What is the standard gravitational parameter (GM)?
• What is the Sun's gravitational pull strength?
• How is the sun an example of nuclear energy?
• If light has no mass, why it is attracted by a black hole? Like, if the force is g = m.a then the attraction would be 0 and the photon would just pass by?
• Why light can't escape from a blackhole if they have no mass?
• Question #e04e8
• Question #54ee7
• Is there a balance between pressure and gravity in main-sequence Stars, white dwarfs, neutron stars, and black holes?
• What defines a planet's orbit?
• Question #8a8fb
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