30 Answered Questions for the topic astrophysics
Size of the Moon Question
Let’s say you were to do an experiment using a coin that helps to find the distance from earth to moon through measuring the distance between your eye and the moon with the coin. This will later... more
Find the velocity of the planet given by description below.
Consider a planet of mass m, moving in a circular orbit of radius r, around a star of mass M. From a = v2/r, the force of gravity and Newton’s second law, find the velocity of the planet. Assume... more
Question about Gravity
J.M.JI understand that two objects pull upon each other with the same gravity, as the gravity equation gives one value for two masses: F = Gm1m2/r2 . However, it sounds absurd to say that a tennis... more
Astronomy astrophysics equation
If the sun expanded to a radius 200 times it's present radius, what would it's average density be in g/cm^3
What is the luminosity of this star?
A star observed has a brightness of 0 W·m-2 and has a distance determined to be 6.41×1017 m (16.60 parsecs). Use the equation: B=L/4(pi)d2 to solve this problem.Thank you!!
Why has the star Rigel moved back and forth on the HR-diagram?
Have a lot of questions. Has it done this more than once? And if it has, has the mass of the star shifted with the fluctuations?Has Rigel already been a red supergiant?How big does the star have to... more
If light takes millions of years to reach us
...are we seeing black holes feeding in the past?
White Holes mistaken for Quasars??
Could a quasar be a white hole? If a black hole pulls in everything including light, while breaking down time as you speed up through the accretion disk till you reach the event horizon, could a... more
Faster than light
Fou Lu what if you are so tall, that every step you take would be the equivalent of the diameter of our galaxy?Would you need 100 K light years (or even longer) to perform this step, or would it... more
Earth's mantle and core ?
Has there ever been an attempt to explore the Earth's mantle (either manned/robotic) ? There was an exploration of the Mariana Trench the deepest point of the crust under the pacific ocean, but it... more
Calculate redshift of a Galaxy using recession velocity and distance
A galaxy is receding away from us with a recession velocity of 100,000 km s^−1. What is the distance to this galaxy? (Don't input the distance, just calculate it.) What is the redshift z of this... more
Flux of sunlight on Earth
The luminosity of the Sun is 4∗10^33 erg s^−1, and its distance to the Earth is 1.5∗10^13 cm.What is the flux of sunlight on the Earth, in units of erg s^−1 s^−1 cm^−2?
Is it possible for two black holes to collide perfectly?
If two blackholes with exactly the same mass, are traversing the universe on a perfect collision course with no other gravitational force effecting either black hole, what would happen to both... more
What happens to a star when its binary star goes supernova?
Taking into account two binary stars, if relatively close, what would happen when one star goes supernova before the other? Does that binary simply rip apart?
How large does a star need to be for its supernova to produce element 115
How large does a star need to be for its supernova or hypernova / collapsar to produce super heavy elements like 115?Also, how abundant are these stars in the universe?
Based on astronomy topic what do you mean by an e-folding time of the main stellar population model?
A comet is discovered that has an orbital period of 85 years. Determine the average distance of this comet from the Sun in AU.
How is distance measured to far away stars and galaxies?
What I need is an accurate description of the methods used to determine the distance to Andromeda. The Parallax method is for nearby objects as I presume. The red shift method applies, but how do... more
Does a celestial system exhibit a collective magnetic field?
Sol exhibits a magnetic field, most of the planets in orbit around Sol exhibit a magnetic field - strong and weak both. Does the solar system as a whole exhibit a magnetic field? Does the paradigm... more
What are the demographics of stars visible to the naked eye?
Of the stars that can be seen with the naked eye, what are the distributions of each type? For example, how many are main sequence? how many are Super Red giants/white dwarfs/neutron... more
How to explain the existence of heavier elements in Population I stars and in Population II stars contain lighter one?
Recently I read Astrophysics Notes where I found a statement that young stars are classified as Population I stars and relatively older one as Population II stars. Population I stars contain... more
How is it possible for astronomers to see something 13B light years away?
In a NPR News story from a few years back:> "A gamma-ray burst from about 13> billion light years away has become> the most distant object in the known> universe."I'm a layman when it... more
How would we see a near-lightspeed object emitting light?
Consider an object travelling near the speed of light relative to us (let it be a spaceship or a star), which is emitting light (consider it monochromatic resulting from a two level electronic... more
What is the evidence for a supermassive black hole at the center of Milky Way?
Black holes cannot be seen because they do not emit visible light or any electromagnetic radiation. Then how do astronomers infer their existence? I think it's now almost established in the... more
In astronomy what phenomena have theory predicted before observations?
As far as I know, astronomy is generally an observational science. We see something and then try to explain why it is happening. The one exception that I know of is black holes: first it was... more