Stars Definition and 890 Threads

So my first question is, how do we know how many stars are in our galaxy? And the second is, how do we know the big bang started with a singularity (as opposed to, say, the universe being a few light years wide and then start expanding 13.7 billion years ago until it reached our present size)...

At first, scientists found stars with planets and think that there are suns with planetary system. But it seems now that every sun has planets. My questiion is are there any suns without a planet.

I have a question regarding binary or multiple star systems and their [hypothetical] orbiting planets. I am curious if it is common (or even possible) for one or more of the orbiting planets to constantly switch the star they are orbiting, as in a figure eight shape. Can the stars "trade the...

If the proton does not decay, will black dwarfs become iron stars in 10^1500 years>

Can there be stars and planets made out of antimatter?

Firstly please if you reply don't post the solution, rather the method you would use to get it as I'm trying to learn how to answer this kind of question for an exam. the problem (quoting my question paper): the stars S1 and S2 are seen along the same line of sight from Earth. Srat S1 is...

Neutron Stars and Special Relativity and General Relativity Here is a question which I can't quite wrap my head around: Suppose we have a Neutron Star that is borderline on the Chandrasekhar limit in its rest frame. In another frame, the Neutron star is moving. As a result, its density...

Is it possible to find the distance to stars from my house using the parallax technique? If I can how close does a star have to be to be measured in a month instead of six months?

Homework Statement Two white dwarfs are found to lie within 16 arcseconds of each other on the sky. The probability that such an alignment occurs by chance is very small. Therefore, they are almost certainly physically associated, lying at the same distance fr0m the Sun. One of the stars...

Let's say we have a star of 0.7 solar masses on the main sequence. Can somebody describe what happens to it when it comes off the main sequence? Thanks Maria

Hi Everyone, First post here. I'm a 37 year old man who has just recently begun dabbling in the basics of Physics, purely for the academic enjoyment of making by brain go "ow!". Upon reading the "bowling ball on a bed sheet" description of how the gravity of large objects can bend the...

What organization is the official namer of stars? The reason I ask is with all the new Earth sized planets being found and the eventual identification of those with at least water and perhaps signatures of life by spectral analysis, the planet first found as such, I believe at least, should...

Homework Statement A certain double star consists of two identical stars, each of mass 3.0E30 kg, separated by a distance of 2.0E11 m between their centres. How long does it take to complete one cycle? Give your answer in seconds. Homework Equations Gm / 4π^2 = r^3/ T^2 (I'm...

I'm always perplexed by the numbers I see on estimates of the age of the universe and the age of our solar system. Somehow, I don't see it adding up. Here's my logic, plese point out the flaw: 1- Current estimate of the age of the universe : 13.73 billion years give or take. (when I was in...

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?

Do the positions of stars determine our position in time, or does our position in time determine the positions of stars?

Would it be possible to calculate the approximate distance between stars in a globular cluster by doing something simple like this: Approximate distance to a cluster: 25,000 Ly Two stars in the cluster just barely resolved in my telescope (resolution about 1 arcsec) Therefore: 2pi...

1.a.) A star is 450 light years from earth. i) what is the minimum time a spacecraft could make a return trip to this star? ii)How fast should the spacecraft travel to make the journey in 30 astranaught years? iii) What is the distance of eart to this star as measured by the astronauts on...

mass of stars? 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, telescopic observations...

Since neutrons have no electric charge, how is it that a neutron star is able to produce a magnetic field? :confused:

Is it possible with our current technology to measure the diameter of stars in galaxies other than our own?

Homework Statement I am trying to understand the following example question in my course book, The answer is actually given but i don't understand how they got to it, i would like someone to give me an idea how this has been worked out In the Sirius Binary system the orbital period is 50...

I'm doing a project about astronomy. I've never done one, I just jumped from quantum physics to here, so I don't think I know anything =.=. To start, I think I need some stars spectrum, but since stars are not as bright as the sun, I don't really know how to have them. Could someone give me some...

Understanding the first star formation is critical to cosmology. Matt Turk is a (remarkably young) expert on this. The way they go about it is with computer simulations and checking the results against whatever can be observed. Here is a talk by Matt Turk...

Below is a question I recently got wrong, and the (automated) feedback. Since the stars are in a stable configuration, I realize that the forces must be equal, but I thought that the differing gravitational forces were balanced by the centripetal forces of the orbit (the smaller star being...

Suppose that a binary-star system consists of two stars of equal mass. They are observed to be separated by 350 million {\rm km} and take 5.4 Earth years to orbit about a point midway between them. I got 1.1x10^29 as my answer, but it is incorrect. Can anyone help me out?

Their are 2 stars orbiting one another. Their masses are equal. The speed at which they rotate is 220 km/h, and their orbital period is 14.4 days. Find the mass of the Star. Homework Equations 220km/h = 61.1m/s 14.4 days = 51840s V= 2pi(r)/T F=ma F=mv^2/R F= m4pi^2r/T^2 Fg=...

Why are stars different sizes? Are there stars made up of something other than hydrogen? It was my understanding stars are made of hydrogen but if all of them where made of this then they should all start fusion whey they reach critical mass/density making them all relativley the same sizel...

I'm quite interested in finding out the % distribution of stars (by type, viz. O,B,..,M), a) within our galaxy and b) within other galaxy types (ex. globular, etc) - and how these distributions change with time. Can anyone sate my curiosity (or point me in the right direction) ?

Homework Statement Two stars 18 light-years away are barely resolved by a 68 -cm (mirror diameter) telescope. How far apart are the stars? Assume \lambda = 540 <units>nm</units> and that the resolution is limited by diffraction. Express your answer using two significant figures...

How do people calculate the distnce between Earth and a star?

So the question is basically, A stationary spherical star sits at the origin, and has mass 8M and radius 2R. Another sphere of mass M and radius R has a velocity and is coming toward the larger mass. We are to neglect gravitational effect until the 2 masses come into contact. What happens is...

I've wondered about this for a while: -the Milky Way which we are part of appears to be a white cloudish streak in the sky. I guess this is because the stars are so far away that it appears as a cloud of light? -But I would assume that all the stars in the Milky Way, our own galazy, must...

Hi all, I was wanting to know of any resources out there that can tell me the how many stars of each spectral type there are in the solar neighbourhood. Any suggestions would be rad!

Homework Statement 2 solar type stars are in a close binary system. Each indivual star has an apparent brightness of m = 10 mag. Determine the apparent magnitudes of the combined system of the 2 stars assuming they cannot be resolved as individual objects. Determine the minimum brightness...

You can get the idea of the size of an object by knowing the distance to the object and the angular distance between the object's edges. Obviously, this is an intuative part of human vision. We can use this method to measure the diameter of our own star. We have methods to measure the...

Homework Statement I am just interested to learn how stars are able to produce electromagnetic waves/radiation (The PROCESS(es)). I am into radio electronics , but have wondered how electromagnetic waves can be produced by stars. I guess 'why' is radiation given off, how is the energy...

I witnessed a rather incredible aerial phenomenon years ago with naked eyes. It was around 2:00AM and a very clear night. As I was talking with someone, I caught something out of the corner of my eye above while I was talking with someone. It was cylindrical-shaped (although the ends seemed...

Hi, I have attatched the question. I have done part a using: m(r) = integral(4pir^2rhodr). Does anyone have any suggestions for parts a and b? Thanks p.s. if anyone knows of a freeware program for paints for macs i would appretiate it rather than having to create pdf's lol

When the sun goes down over the horizon, we can still see the sun because the light of the sun is bent by our atmosphere. I would imagine that if one were outside of our atmosphere on the far side of Earth away from the sun, yet in a path in line with that light they would also see the sun...

It takes a continuous input of energy to spin, otherwise things would fly apart or stop spinning. So why do large macro objects spin, and continue to spin?

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 intensity...

Earth first formed about 4.6 billion years ago, condensing out of the gases & dust in the proto-Sun's Planetary Disk. But, for about the 1st billion years, the proto-planet was repeatedly pummeled by swarms of Impactors. They deposited gargantuan quantities of energy onto the Earth's surface...

Bigger stars are significantly brighter. That pushes back their Habitable Zones (HZs), where D2 ~ L, which makes them look smaller in the skies of (hypothetical) habitable planets, whose years are also a lot longer: Type Mass Temperature Radius Luminosity HZ-Distance Apparent-Size HZ-Year...

By inspection of the following star data (Solar units), we find that: M ~ R3/2 (Nilssen's Law) From this we can derive further scaling laws, for average density (p) and surface gravity (g): p ~ R-3/2 g ~ R-1/2 p ~ g3 Surface gravity (g) acts as a "compressive force" on the star's gases...

I did some research in regards to the age and metallicity of population I stars in hopes to come up with a novel solution to the Fermi Paradox. Anyways, while the metallicity of the oldest Population I stars can be tracked down to be something like -1 (10% of that of the sun) determining the age...

There were two stars one above the other in the Western Sky just after sunset. I think they were planets. One could by Uranus but I am not sure what the other may be. I am at: lat=40.91666667 long=81.43333333 Can anyone help?

Since Dark Matter is by definition immune to electromagnetic forces, then it has no other way to interact except through gravity -- unless one wants to come up with some entirely new force, which has never been seen. If Dark Matter did have some force of its own, akin to electromagnetism...

Hi all, hope everyone is doing well this rainy cold night. Hopefully it's not like that wherever you are. Anyhow - I hope someone can help me out. I'm writing some software for a mobile device to create star maps. I've gotten pretty far into it. I'm using data from the Yale bright star...

Homework Statement Three stars, each with the mass and radius of our sun, form an equilateral triangle 5.0*10^9m on a side. If all three are simultaneously released from rest, what are their speeds as they crash together in the center? Homework Equations Fg= GMm/r^2 The Attempt at a...