A star is an astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but due to their immense distance from Earth they appear as fixed points of light in the sky. The most prominent stars are grouped into constellations and asterisms, and many of the brightest stars have proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. The observable universe contains an estimated 1022 to 1024 stars, but most are invisible to the naked eye from Earth, including all individual stars outside our galaxy, the Milky Way.
A star's life begins with the gravitational collapse of a gaseous nebula of material composed primarily of hydrogen, along with helium and trace amounts of heavier elements. The total mass of a star is the main factor that determines its evolution and eventual fate. For most of its active life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space. At the end of a star's lifetime, its core becomes a stellar remnant: a white dwarf, a neutron star, or, if it is sufficiently massive, a black hole.
Almost all naturally occurring elements heavier than lithium are created by stellar nucleosynthesis in stars or their remnants. Chemically enriched material is returned to the interstellar medium by stellar mass loss or supernova explosions and then recycled into new stars. Astronomers can determine stellar properties including mass, age, metallicity (chemical composition), variability, distance, and motion through space by carrying out observations of a star's apparent brightness, spectrum, and changes in its position on the sky over time.
Stars can form orbital systems with other astronomical objects, as in the case of planetary systems and star systems with two or more stars. When two such stars have a relatively close orbit, their gravitational interaction can have a significant impact on their evolution. Stars can form part of a much larger gravitationally bound structure, such as a star cluster or a galaxy.
*Please Help* Question related to Orbital speed of star, Keep getting *10^4 to high??
Homework Statement
A star has a mass of 2.2*1030kg, there is a planet of mass 4.5*1027kg orbiting it at a distance of 3.1*1011m (also told that it has a "period of wobble" of 9.2*107s due to the orbiting...
Im trying to solve back for Jupiters effect on the suns orbital velocity. I've looked up the asnwer and its 12.7 m/s
and the formula I have for this is
http://en.wikipedia.org/wiki/Doppler_spectroscopy
v = SQR (Gm*/r)
where G is Grav constant
M is the mass of the star (planets mass is...
How do I do this problem. I think you have to use this formula L1/L2 = 2.512^(M2-M1) and then see the relationship with the Stephan Boltzmann Law. I keep getting an answer of 0.1 based on the ratio, but it's not making any sense.
Here's the question. Star P is a pulsating variable star. As...
Given the semi-empirical mass formula for the binding energy of a nucleus is
B(Z,A)=a1A-a2A2/3-a3Z2/A1/3-a4(Z-N)2/A+delta(Z,A)
calculate the energy released in the reaction 28Si +4He --> 32S + gamma.
Hence find how long silicon burning will sustain a massive star which has 1Mo of silicon in...
Hello again,
I've got a question about a star in a hydrostatic equilibrium.
How do I derive an equation of motion for a pertubation in the full momentum equation? I'm attaching my solution (my_solution.jpg) , but I'm not quite sure about it.
The full exercise is attached as...
Hi, I'm currently studying GR from Wald's book. The book is fine, but I want to know more details about the collapse of stars, e.g., more about white dwarfs, neutron stars, mass limits, the use of Fermi-Dirac statistics in this cases, etc. What book, paper or website would you recommend?. (I'm...
Homework Statement
(1) A Physics lecturer, on a dark night, shines his laser pointer towards the star Vega.
(a) Roughly, how many optical photons from the Sun per second enter the eye of an
astronomer standing on a planet orbiting Vega ? Assume that 50 % of the light
from the Sun is...
Does the resistances of each phase in a 3 phase generator add together in the Star (wye)?
I read on a windmill site that the Delta connection is typically one third the resistance of the Star. So if i had 3 phases that were .5 ohms each in Delta configuration, would the resistance be 1.5 ohms...
Hi all !
I'm looking around the net to find good resources on how to compute total radiation flux from a given star at a given orbiting distance.
Ideally I'd like to get not just the W/m2 of the star, but also the expected high-energy radiation, thermal, solar wind pressure.. well, the...
I know that nuclear fusion is the source of energy for our sun and most of the other stars. Neutron stars and white dwarfs have very high surface temperatures. What is the source of their energy?
This is blatant homework help that I don't know how to approach. Any hints would be appreciated.
Suppose you are in an infinitely large old universe in which the average density of stars is n = 109 Mpc-3 and the average stellar radius is equal to the sun's radius is R = 7*108. How far, on...
Homework Statement
Show that Total energy of this system is given by E=(-432(r^5)(pi^4))/(G*T^4)
http://img189.imageshack.us/img189/7325/38899527.png Homework Equations
F=GMm/r^2
F=mv^2/r
T=2(pi)r/VThe Attempt at a Solution
[PLAIN][PLAIN]http://img97.imageshack.us/img97/7766/27047783.png
There is a problem:
"The distance of Barnard’s star is 1.83 pc and mass 0.135 M. It has been suggested that it oscillates with an amplitude of 0.026" in 25 year periods. Assuming this oscillation is caused by a planet, find the mass and radius of the orbit of this planet."
My question is...
******* I attempted to post this already today but I don't think I'm not sure if it worked...I apologise if this is a dublicate!**********
the problem is:
suppose that a star is modeled as having a density that decreases linearly from the center to the surface,
rho(r)=rho_c(1-r/R)...
Homework Statement
A stellar wind behaves as a steady adiabatic spherical outflow of a perfect monatomic gas (gamma=5/3) from the surface of the star, so at radius 'a' the density is 'p0' temperature 'T0' and outflow velocity 'u0'. If the fluid motions are dominated by the star's gravitational...
Homework Statement
Assume a star is in hydrostatic equilibrium and that the density of the star is follows
\rho \propto \frac{1}{r^{a}}
where \r is the distance from the centre of the star and \r is a constant.
Derive an relation for the pressure of the star as a function of \r...
Homework Statement
Consider an unresolved binary star at a distance of 500pc consisting of
an A1V dwarf and a K0III giant star.
compute mb and mv and B-V for this object
we know the mass, luminosty, radius, Mbol , Mv, Te , and B-V for each individual star.
Homework Equations...
I've often wondered why there is so much misinformation around the topic of the reasons that very massive main sequence stars are so luminous. It even shows up in books, but if we restrict to seemingly reliable internet sites, I'll bet that in 10 google hits of sites that offer an explanation...
A star that has been ejected from a galaxy probably wouldn't be any different from stars within galaxies. It could be possible for a planet to orbit this star. What would the night sky appear like? Would the galaxies be too dim to see, and the night sky fully black?
Lets say that the star is...
OK, I know it's difficult to move a star. But I'm trying to write some science fiction here and I want to make sure I'm consistent with astronomy and cosmology.
Now assume that over the next billion years we completely colonize the galaxy and we're all cooperative and stuff. What would be the...
Homework Statement
Consider a star made up of ionized hydrogen.
First, take the electrons to be non-relativistic. If the mass of the star is M, derive
an estimate for the radius R. As the mass increases, how does the radius change
Homework Equations
p~(h2 /Me) n5/3
The Attempt at...
I am trying to find some sky surveys that have longitudinal data of star magnitudes. The passband does not matter. All that matters is that stars has been observed periodically for a decent amount of time (no surveys with only 9-10 observations per catalogue object).
Sadly, the only ones I know...
I am here with another silly doubt...Is twinkling because of the star or the distance? What matters here?
For example...If the stars Sirius and Proxima Centauri were at the same distance from earth, which star would twinkle more?
As they are at the same distance, would they twinkle...
In the Doppler shift or radial velocity method for detecting exoplanets, it is assumed that the orbital period of the star's planetary companion is equal to the period of the star's detected wobble. I'm assuming that this fact comes straight from the solution to the two-body problem.
My...
Hi, I'm a biology student...with barrrrely any physics knowledge. However I have to write a report on this article, A Jupiter-mass companion to a solar-type star. and in it, the author finds the upper limit to the mass of the planet, but i read that using the radial velocity method only the...
Hi
I have to describe a method to solve a problem involving a black hole. The only information given is the period of the orbiting star and the radius of the orbit. I have to find the stars mass.
Would i use the equation F=(mv^2)/r and then substitute in v=(2 pi r)/T for the radius where T...
Forces in Equilibirum? Star Wars forces?
Homework Statement
http://iweb.tntech.edu/murdock/books/v4chap1.pdf
Go to question 11 where you see three charges hanging.
The solution is something i don't understand.
The forces between the middle and left or right are the same. But the...
I have been reading about the star system on wiki and noticed that one of the Alpha Centauri stars could in theory have a terrestrial planet in the goldilocks region. I also came to know that its orbit would only be stable for 250 million years. Given that these stars have been around for a few...
Hello,
I was reading a book on Quantum Mechanics by Manjit Kumar, and read at the part of the Bohr–Einstein debates about Einstein's box to measure the weight of a photon.
Now I was wondering, how can a Star collapse if it's constantly losing so much weight?
I've heard many things about the fusion in the star.
But recent cosmic data say vary high energy Gamma ray emission occurring in the Universe.
Some research said its related to the Dark Matter annihilation.
I'm weakly afraid of saying about that, but.
Is one of them related to particle...
this is a piece of star's picture that was taken with using Optical Vortex Coronagraph by university arizona in 2006
If you compare this objects with planets around star beside their unusual form you can see they are very bright as if they have their own light source aside of star. and also...
mass of a star...
given is a binary star system, with mass m1=6*1.99*10^30kg, radius =r1, v=270km/s, orbital period, T=1.7days... the other star of the binary system(compact and dense)with mass m2, and radius r2 orbits around a same common point... (r1>r2, G=6.67*10^-11Nm^2kg^-2)...
Hello All,
I am studying for my introductory astronomy exam and I came about these two question;
Galileo discovered
a) radioactivity b) some moons of saturn c) 2 moon of Mars d) some moons of Jupiter e) the telescope
I know he discovered 4 moons of Jupiter but "some" is a bit...
Homework Statement
Two stars are in a circular visual binary system. The orbital
period of the binary is 30 years. The distance to the binary is 20
parsecs. The angular radius of the orbit of each star is 1". What
are the masses of the two stars?
Homework Equations
I am assuming that...
Homework Statement
A star of mass M and radius R is moving with velocity v through cloud of particles of density \rho . If all the particles that collide with the star are trapped by it, show that the mass of the star will increase at a rate
\frac{dM}{dt} = \pi \rho v \left(R^2 +...
The question is A main sequence star is barely visible at a distance of 20 pc with a certain telescope. The star subsequently
ascends the red giant branch, during which time its surface temperature drops by a factor of 3 and its radius increases by a factor of 50.
a) Determine the how...
Homework Statement
A pulsating star has a period of 3 sec as seen from the rest mass frame of the star. What is the period of the star as measured by an observer traveling 2.4 x 108 m/s with respect to the star?
Homework Equations
The Attempt at a Solution
Homework Statement
Consider a binary star system in
which the two stars have masses M1 = 1.24 solar masses and
M2 = 3.04 solar masses. The period of star 1 is 142 yr. The
eccentricity of star 1 is \epsilon = 0.691. Use G = 6.67259 × 10−11
Nm2/kg2, take the astronomical unit to be...
A letter in the current issue of Nature:
==quote==
A two-solar-mass neutron star measured using Shapiro delay
P. B. Demorest1, T. Pennucci2, S. M. Ransom1, M. S. E. Roberts3 & J. W. T. Hessels4,5
National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia 22093, USA...
Hello everyone;
I am a new member and have little formal hard science ed, but have read many pop science books by Sagan, Hawking, and others. In light of this fact please try to formulate answers with this in mind... NO MATH SPAMMING ALLOWED lol
My question has to do with the...
When a neutron star flucuates into a black hole does the gravity increase tenfold? Or does the neutron star gravity (while turning into a black hole) increase as expected with the addition of more mass?
Homework Statement
I have to write a computer program to simulate a binary star system and I can not assume that the larger mass is stationary. I am given their respective masses, and the period of the system. I am just wondering how to find the write combination of initial velocity and...
Homework Statement
A star is moving in a circular orbit of radius r within a galaxy. What is it's orbital speed
v(r) as a function of \rho(r) and radius.
The galaxy is spherically symmetric with a mean density \rho(r) and radius R.
Homework Equations
F =...
Homework Statement
Use a coupled fourth order Runge-Kutta, to find the structure of white dwarf stars.
I think I am applying the Runge-kutta method wrong?
Variables defined in C code notes
Homework Equations
Equations in c code. and in attached images.
The Attempt at a Solution
This is...
When calculating the space velocities of stars by combining what we see of both their radial and proper (tangential) motions, how is the final velocity determined?I don't believe they just add these two vectors together do they? Do they make use of the transverse Doppler shift calculation here?
Homework Statement
b) Two stars, both of which behave like black bodies, radiate the same total energy per second. The cooler star has a surface temperature, T, and 3.0 times the diameter of the hotter star.
i) What is the temperature of the hotter star in terms of T?
ii) What is the ratio of...
Uploaded the PDF someone please help me i have no idea what to do!
Homework Equations
(-G*m1*m2)/r^2
dP/dt
The Attempt at a Solution
I don't even know where to start i drew everything out and i think dP/dT is 0 cause its at a constant speed someone please help! :(
Hello expert
I have downloaded several star catalog. But how can I open the file? How can I read the file? I would like to see the positioning of the stars.
I would also like to know the distance and angle between stars.
If anyone here know, would appreciate if you can share. I have tried to...