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.
Homework Statement
A star is at radius r = 10kpc with v_t=100km/s and v_r=50km/s. The spherical potential is
\phi = V^2ln(r) with V=200km/s
1. what is r_min r_max?
2. Integrate the orbit numerically
The Attempt at a Solution
1.
at r_min and r_max v_r is 0 therefore I can write...
[b]1. The two components of a double star are observed to move in circles of radii r_1 and r_2. What is the ratio of their masses? (Hint: Write down their accelerations in terms of the angular velocity of rotation, w)
The answer is m1/m2 = r2/r1.
How does one cancel the velocity from the...
Hello Friends
I need little help pleasezz :redface:
How Can I solve this circuit? Which things first I have to find. And how.
Problem Statement is.
A. Average power of each phase load and total Load.
B. Determine the reactive power of each phase and total reactive power
C. Find the...
Hello,
Sorry if this is not the right place but I'm trying to find this for days now...
I'm trying to find a working formula to determine the position (r.asc/decl) of a star at any given time and for a specific location on earth.
So the parameter would be:
R. Asc. of the star...
Hi everyone,
Firstly i want to say that I've watched some of the "The Universe" episodes on my computer, and i pretty much have basic knowledge about the cosmos. But there's only one thing in particular that I'm confused: the life of a star. I pretty much know the "core" of it, but i can't...
Ok, I'm watching all of the episodes this season. This seasons does seems to be going better, they are eliminating the duds upfront, which is a nice change. They canned that weird health food nut this week.
The next person I want to see go is Jamika. She is so fake when she gets in front...
How do I calculate the mean phase-weighted intensity magnitude of a variable star? I.e., if I have binned (magnitude) data points over the whole light curve, how do I change those magnitudes to intensities so that I can get the average intensity and then convert that value back to a magnitude...
Star clustering... (Help me...)
Here goes...:cry:
I am currently taking a BS Degree in Applied Physics and I do need someone's help right now. My research is all about the clustering of stars... Frankly speaking, I don't know where to start. I just first want to organize my thoughts and step...
Just saw Star Trek like an hour ago with my friend and it was great! :biggrin: I've never actually seen the show but I think I can make time. How did you guys like it?
It's well known that white dwarf stars are supported by degenerate-electron pressure. Calculation shows that maximum mass of white dwarf star is about 1.4 solar mass. My question is why it has a maximum mass? The postulate of Quantum mechanics says that it should be a distribution of mass...
Homework Statement
28. Calculate the quadrupole tensor I_{jk} and its traceless counterpart \overline{I}_{jk} (Eq. (9.78)) for the following mass distributions.
(a) A spherical star whose density is \rho(r, t). Take the origin of the coordinates in Eq. (9.73) to be the center of the star...
Hello my name is Kristoffer and I am new here :)
I have made a spreadsheet in MS Excel to compare star-data and need some help try it out. Testing.
This filesize is about 15 mb (4,5mb zip-packed)
I have not taken any astronomy class or something like that. So I am not 100% sure the...
Hi,
When the core of a star shrinks during its evolution, does it always lead to the expansion of the star? If not, why? What cases would cause it to expand?
Thanks in advance,
Maria
Homework Statement
The normalized extinction is defined as
F(\lambda) = \frac{A_{\lambda}-A_v}{A_B - A_v}
where A_{\lambda} is the extinction (in magnitudes) at wavelength \lambda . B and V are wavelength bands but for the purposes of this question we will
assume that they represent...
http://www.imdb.com/title/tt0796366/
Double-click to watch the trailer
https://www.youtube.com/watch?v=7w4vk5OZmn8
Expectations?
It looks like they use my idea of a reentry suit.
Homework Statement
"The mass of a star is 4.85x10^29kg. In scientific notation, Kepler's constant for that star is bx10^w s2/m3. the value of b is_____."
Homework Equations
K=T2/r3
The Attempt at a Solution
This problem is very tough. I first assumed that K would be 0 because the...
What's physically stopping all the fuel fusing at once or rather each stage of its fuel cycle fusing into the next quickly? i know there's a lot of it and gravity holds it together but what are these atoms doing while they wait to under go fusion exactly? They are after all under the same...
https://www.youtube.com/watch?v=Il5TBgD9kHI
Whoops, use this link:
http://www.youtube.com/watch?v=Il5TBgD9kHI&eurl=http%3A%2F%2Fwww%2Ephysicsforums%2Ecom%2Fshowthread%2Ephp%3Ft%3D307427&feature=player_embedded
I'd like to create a catalogue of stars that are within a one degree belt along the ecliptic. Since most databases use RA/Dec coordinates, this appears to be a daunting task. Any suggestions?
If someone had a superstrong chamber that could withstand anything (hypothetically) if they constantlty fed the correct materials at the correct state into the chamber could they create a mini self sustaining star?
Homework Statement
A certain star is 13 million light-years from Earth. The intensity of the light that reaches Earth from the star is 6 10-21 W/m2. At what rate does the star radiate EM energy?
Homework Equations
i know you have to convert lightyears to m. (1.23e17m) multiply this...
Problem about "binary star system"
Homework Statement
About half of the visible "stars" are actually binary star systems, two stars that orbit each other with no other objects nearby. Consider the motion of the center of mass of a binary star system. For a particular binary star system...
I need to work out the luminosity of 3 stars 85 PEG A / B / C using the following data and equation,
Absolute Mag of stars A/B/C/SUN
MA = 5.28
MB = 8.53
MC = 15
MS = 4.84
Apparent Mag of stars A/B/C
mA = 5.75
mB = 9.00
mC = 15.47
LS = Luminosity of Sun – 1 ?
Equation
MA-MS =...
If a person could orbit close to a neutron star what color would it appear to be?
I have always imgained them to be blue, but this might be totally wrong. :rolleyes:
I went to an American Helicopter Society (AHS) DC, chapter meeting tonight. It's full of people who are big in the government and industry. This months guest speaker was with Dell Dailey of the US department of state (He's a former chopper pilot, blackhawks, cobra, and hueys). He said whatever...
I observed a really bright star in the sky a few minutes ago its still there.
Its in the west sky low just a few degrees above the horizon.
I'm assuming its a planet because i live in the city of London, Ontario which is a pretty large city for Canada.
I'm also assuming its Venus...
Homework Statement
Neutron stars, such as the one at the center of the Crab Nebula, have about the same mass as our sun but a much smaller diameter.
If you weigh 650 N on the earth, what would be your weight on the surface of a neutron star that has the same mass as our sun and a diameter...
Does anyone know if an average Neutron star with a diameter of 10 miles, was headed towards Earth.. would our Nuclear weapons be able to physically destroy it? Assuming our technology can provide a direct hit, and do it in time. If so, then how many Megatons would the Nuke need to be, and how...
Here's one for everyone to ponder.. Firstly, this question has always bugged me since I was born. It's not impossible to imagine an Alien civilization 1.5 billion years more advanced than us, using the method of 'Hurling Neutron Stars at 99% the speed of light, to destroy planets and their...
So far i understand that a star many light years away from us can be moving at the speed of light, but this breaks no rules as it is traveling with space.
But how about the star's momentum relative to us on Earth, i can only guess as it is moving away from us at the speed of light it's momentum...
Homework Statement
In recent years, a number of nearby stars have been found to possesses planets. Suppose, the orbital radius of such a planet is found to be 4.3 times 1011 m, with a period of 1080 days. Find the mass of the star.
Homework Equations
?
The Attempt at a Solution
I...
I was looking for a space time metric that describes the INTERIOR of spherically symmetric rotating stars. However, wherever I look it is always the metric for an exterior of "slowly rotating star" (frame dragging effect) or something similar to it but always the metric AROUND the object...
Homework Statement
A star of mass M and radius r rotates with angular speed of such value that objects on the surface at its equator are just about to experience zero apparent weight. The period of rotation of the star is given by?
Homework Equations
g' = g- Rw[SUB]2 (where w is the...
Homework Statement
A star surrounded by a sphere of dust with a radius R. The star emits a short bright flash of light, it is absorbed and re-emitted by the dust. Someone much further away than R sees the light, first at a point on the shell and then in an expanding ring.
A)Show that the...
Homework Statement
I am trying to describe the limit for the minimum radius of a star to first year university level students in order to describe the reason for the size of the Sun. I'm a bit confused by the critical density of the material in the star's core and how we know that the main...
Star Wars + Legos = Yes I am a big Dork...whatever. I still think this is COOL.
Sweeeeet. That's freakin awesome.
http://www.flickr.com/photos/23575410@N05/
That kid must have spend a few grand on that. Legos are $$$ expensive.
Determine the average density in solar units of a 0.5 solar mass star with effective temperature 20000K and luminosity 0.03 solar luminosity.
I don't know what the relationship is that I have to use, I have tried using this:
rho = 3m/(4pir^3)
and mixing it with other equation but I...
In my problem, it says only this: "The star Arcturus culminates. What is the sidereal time at this moment?"
Do I need to know when the star culminates to solve the problem, and if I do where would I find this information?
Homework Statement
A microwave detector is located 0.5m above the surface of a large lake far from the shore. As a star, emitting monochromatic microwave radiation of 21cm wavelength, rises slowly above the horizon, the detector indicates successive maxima and minima in the signal...
Homework Statement
A planet is in a circular orbit about a star that explodes, shedding 2% of its mass in an expanding spherical shell. Find the eccentricity of the new orbit of the planet, which otherwise is not affected by the shell.
Homework Equations
\sqrt{1-\varepsilon^2} =...
If this is true, could someone please tell me, if a grain of sand represented the size of an average star what would be the average distance between every grain of sand to give a approx size to the universe.
Hi
I've just started a new Electrical Course and have been working through an old exam paper but i got a bit lost when doing the star connection question - see attached for question and work done
would just like someone to tell me if any of what I've done is correct and where I've gone...
Homework Statement
The mass of a star is 1.51·1031 kg and its angular velocity is 1.50E-7 rad/s. Find its new angular velocity if the diameter suddenly shrinks to 0.49 times its present size. Assume a uniform mass distribution before and after. Icm for a solid sphere of uniform density is 2/5...
i got part a, but i can't get part b!
1. A star has a mass of 2.96 x 10^30 kg and is moving in a circular orbit about the center of its galaxy. The radius of the orbit is 3.3 x 10^4 light-years (1 light-year = 9.5 x 10^15 m), and the angular speed of the star is 1.6 x 10-15 rad/s. (a) Determine...
Star with negative pressure?
Is it possible to have a star with matter with unusual equation of state.
Will it be possible to have a star with negative pressure.