Stars Definition and 930 Threads

I feel the need to make sure my Dobsonian scope is working at its best. I was considering a conventional (?) red LED collimator but I suddenly begin to see these Artificial Stars on sale. Would that be a better way to go? Anyone have experience of them? Looking at real stars tells me that the...

I've been recently watching videos about white light and the double slit experiment and how it creates a rainbow. It let me to some confusion and I would like some clarification. My questions are: Do all stars like ours produce white light? Would red giants only emit red light and blue giants...

Hello everyone, I know that pre-main sequence stars do heat up because of gravitational contraction, and the increase in internal energy (and so in temperature) comes from this shrinking and is governed by the virial theorem (...

And how we use it to calculate distances from stars to the earth.Thank you

I will try to be as literal as I can. I was researching about the black hole, according to NASA and much other organisation a black hole form when a star collapses under its own gravity. "Stellar black holes form when the center of a very massive star collapses in upon itself". Gravity is...

If I spin around in an open field at night and look up to the stars they appear to be moving relative to me. Additionally, they are very far away and trace out a giant arc length in a very short time (S=rθ). With respect to me, these stars are moving faster than light. Is this a problem? Has...

Hi. I couldn't find good information of this online, so I'll ask here. I'm wondering what the maximum possible lifespan of a particular star. Here's what is known of it: It's a B class-blue giant star. Its surface temperature is 25,000 K. (This is very vague and may offer no help but:) It has no...

I am not a physicist but have heard that photons from the sun effect the flight path of asteroids? I was just wondering if these same photons would ever be able to effect nearby star systems? Therefore could there be a slight push between star-systems pushing them further apart? (Does this come...

Homework Statement Ok, these questions are very simple but they are really bugging me and I would greatly appreciate an explanation. Question 1 is "which of the following elements must have been made in stars". The options are hydrogen, helium, carbon, oxygen and iron. Question 2 is "which of...

If so, what is the evidence? Sources are appreciated.

I know that the speed/acceleration of a star can be measured using redshift/blueshift caused by the motion of stars, but I just learned that gravitation also causes redshift and blueshift. Would this not cause some uncertainty into the determining how fast a star is moving away from us? If so...

My lecturer claimed that "reverse entropy stars" could exist in our universe. One of the examples he gave was that if you exposed some sort of detector in the direction of a hypothesized reverse entropy star, you could determine if it existed by whether it "sucked" photons out of the detector...

I'd like to answer this yes or no question for a number of objects: "Is this star, at any point between these two times, going to be above the local horizon?". Say, I'm at the prime meridian at a latitude of 50 degrees, and I want to know whether, between the sidereal times of 11:00:00 and...

I just read something about the theory of stars formation that left me puzzled. I am easily puzzled so please bear with me. The theory goes somewhat like this: There is s nebula (gas) that is contracting and increasing mass and pressure at its center until they are so big that a nuclear reaction...

Homework Statement Calculate the number of white dwarf, neutron star and black holes the galaxy will have after 5Gyr of evolution. M<8(solar mass) for white dwarf 8(solar mass) < M < 40(solar mass) for neutron star M > 40(solar mass) for black hole Initial mass function is ξ(M) = AM-s...

Dear PF Forum, Just out of curiosity :smile: Can we (through telescope or HST for example) see stars in Andromeda Galaxy? Is the Andromeda Galaxy the closes galaxy to us. Can we really be sure that there is no other galaxy across Milky Way because our line of sight is blocked by clusters of...

Panama Papers Some highlights so far, I wonder if any US politicians or businessmen are in the records.http://www.usatoday.com/story/money/2016/04/03/german-paper-massive-financial-leak-reveals-offshort-accounts/82586798/ The Panama Papers (11.5 million documents, 2.6 terabytes)...

Are there any binary stars that can be seen with binoculars which have orbital periods you can observe from week to week or month to month? tex

Janus submitted a new PF Insights post How Representative is the Night Sky? Continue reading the Original PF Insights Post.

Are the gas giants and stars only composed of gas particles? Don't they have a solid crust or something? If they don't have a solid part then how can they exist alone?

Do all stars in the Milky Way orbit the galactic center in approximately the same direction? Also, toward which Zodiac constellation is the Sun moving in its orbit?

Now kindly pardon my ignorance but I hope one of you can explain to me how this can be possible. A rotating neutron star or pulsar have been observed to spin at between 10 to 700 times per second. Now before I proceed further I like to draw your memories back to the merry go round we played as...

From the perspective of someone at or near the exact north pole (where, for all practical purposes, they are not rotating), ignoring the gradual change of the stars as the Earth orbits the sun, would the stars appear to move at all in the night sky? Or would they be stationary because the...

Hi all, I refer to the following pdf document, in particular the appendix: http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1974A%26A...37..183A&link_type=ARTICLE&db_key=AST&high= End goal is to distribute N stars each having mass m (looks like equal mass stars is the easiest scenario)...

I was thinking about adding another page to my website concerning the nearest stars, the brightest stars, etc. In a list of the nearest stars, the vast majority are brighter than the Sun. (I looked for stars with an absolute magnitude that was greater than the Sun's (4.85) and had a visual...

Hi, Could I please get some guidance on if my approach and solution are correct here. I feel I'm on the right track. But even though the answer to part b) feels right, it would be helpful to get advice. Homework Statement A space rocket travels between two stars separated by 10 light years...

I was going to try and do an animation of stars orbiting Sagittarius A* but can't seem to find any useful data for it. The Wikipedia page has some data https://en.m.wikipedia.org/wiki/Sagittarius_A* and was trying to reconcile this with https://en.m.wikipedia.org/wiki/Orbital_elements since I...

Are all stars contained within a galaxy? Or are there some single stars between galaxies? If there are intergalactic stars how were they created since I thought galaxies provided the creation mechanism? tex

Several days ago I started thinking about the mystery of dark matter (yup, it was after LIGO discovery, and we all do it from time to time, right?). Then I came up with a strange conclusion that within our galaxy, there should be an equivalent of about 24 000 stars that we just cannot see--in...

One questions that I am really confused with! If the sun is 8 light minutes away, this means that whenever we see the Sun, we are actually looking at how the Sun looked like 8 minutes ago if I am not wrong. If we look at a star that is let's say 15 billion light years away from the earth, is it...

Good morning all, Recently in a modern physics course of mine, my professor was covering the topic of energy levels and ionization energies and it included a diagram very similar to this one: While it is interesting to learn that these diagrams correspond to a very specific and strict set...

As the Stephan-Boltzmann's Law says, the minimal change in a star's mass would have a massive effect on its luminosity, but can necessarily two stars with the same mass have the same luminosity?

What happens to the neutrons in a neutron star as it collapses Into a black hole?

What'd happen if two stars collided? Could it happen? Would the speed/mass change the result?

A method of definitely distinguishing a neutron star from a possible stellar black hole is that it produces X-ray bursts, which have a sharp rise time and may last for an extended period. I had previously thought these occurred when hydrogen fell to the surface and was immediately fused to...

Dear PF Forum, Anybody knows how to remove the star? I forgot when I unintentionally put that star, now I want to remove it. But I can't. Some websites suggest by inserting some HTML (or Java script? Can't tell the difference) script. Is there an easy way withouth signing off google? Thanks...

Hey PF, Since there are stars that can be powered predominantly (>50%) by the CNO cycle, which requires carbon as a catalyst, and i understand the core temperatures of these stars is about 106 K. Does this mean that stars where the triple-alpha process is dominant (108 K) had to exist and die...

I'm looking for reliable data of the spectra of different stars, anyone know any good resouces? Quantitative data would be best because I want to analyze it myself (not just find out something that was already on the site). Thanks in advance :)

I think this could be a good chance that we see how neutron stars form from White Dwarf mergers. The combined mass of the two are less that than required for a type Ia Supernovae. Won't they merge and collapse into a neutron star? What does everyone else think might happen. I want to be sure if...

Greetings, Hi, I am new member of Physics Forums. Here is my question: How many stars can we see from Earth? and also If you know, How far can we see? Thanks!

I am a little puzzled with how there is a White Dwarf Binary of Five Minutes. How do they get so close?

"At a deeper level, I've had several people tell me that the stars scare them." -Tony Flanders, Sky & Telescope, Jan. 2016 issue

Hello pf, I have been trying to grasp the concept of RA. I have read through a few books and I know that it is measured eastwards from the point on the celestial sphere where the Sun crosses the celestial equator at the vernal equinox. I just want to check I understand this correctly. Does it...

I have a few questions. Would a given galaxy contain same amount of stars and gas through its lifetime? I want to say no, but I was thinking for every dead star, there will be a new star forming, and the gases would be preserved in the galaxy. And would the spiral disk component of the Milky Way...

Homework Statement What is the Jean's length in parsecs for a typical neutral hydrogen cloud, which has a density of n(H I) ~10^8 atoms/(m^3) and a temperature of 100K? Homework Equations jean's length = sqrt[(15*K*T)/(4pi*G*u*p)] where: 'K' is the Boltzmann constant 'T' is the temperature of...

I have just found this article and wondered how many bodies in the milky way have proper motion. And why our galaxy seems different to others in that it has such a massive black hole. http://arxiv.org/abs/astro-ph/9807210 A. M. Ghez, B. L. Klein, M. Morris, E. E. Becklin (UCLA) (Submitted on 20...

Homework Statement Picture- https://www.flickr.com/photos/137149410@N02/shares/32x7oM The stars are at vertices of a 45 degree right angle. It is assumed that the stars are spherical so that we can replace each star by a point mass at it's center, as seen in the picture. 1) The two forces...

Population 1 stars are young, hot and more luminious, so when a star is young, fusion of hydrogen is taking place inside it's core. Why then Population 1 stars are called metal rich and Population 2 stars 'matal poor'? Why shouldn't it be the reverse?

In a neutron star gravity has overcome electron degeneracy pressure allowing the protons and electrons to combine into neutrons. But if that is the case, how do neutrons emit light if there are no electrons to swoosh the photons away? I have been thinking, and wonder if the surface (or "crust")...

Homework Statement The Sun has an absolute visual magnitude of about 4.8 and a particular star has an absolute visual magnitude of –0.29. How many times more luminous is this star than the Sun, assuming these stars have similar spectral types and hence colours? a) 100 times b) 125 times c) 150...