What is Star: Definition and 1000 Discussions

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.

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  1. hongseok

    I Stellar evolution path and Regression line

    I analyzed the relationship between the surface temperature and luminosity of stars of similar mass using a regression model. Through this, I was able to obtain a regression line. Since stars of similar mass show similar evolutionary paths, I believe this regression line can be viewed as a rough...
  2. wanwa

    Discover the Correct Star Radius with These Key Answers | Choose Wisely!

    I have the key answer for this (choosing 1 answer) A. 0,018 B. 1,134 C. 0,278 D. 0,974 E. 0,982
  3. P

    B Supernova Ejection: How Large Are the Chunks?

    when a star goes supernova, does it eject out earth, mercury and mars sized chunks. Surely the asteroids that are even the size of Texas won't have enough gravity to compact hard enough to become one chunk. What is the current belief on how large of chunks are ejected from a supernova. Thanks
  4. Vanilla Gorilla

    I Calculating the Hodge Star in the most general case

    I have been learning a little Differential Geometry lately and recently came across the Hodge Star. So far I have been unable to find an explanation for its calculation that I can understand. I believe some ways of computing it were only valid in an orthonormal basis, but I would like to be able...
  5. S

    B Night Sky of Alpha Centauri: Sol as a Bright Star

    I finally got around to watching the movie "Avatar", which takes place in the Alpha Centauri system. I was thinking that a great little scene between the 2 main characters (i.e., the paraplegic Earthling and the Centauri woman) would have been looking up at the night sky and seeing Sol as a...
  6. Grelbr42

    Happy Star Wars Day - May the 4th Be With You

    Happy Star Wars Day everybody. May the 4th be with you! And only 138 days until Talk Like a Pirate day.
  7. C

    I Calculating Proportional Luminosity of Fictitious Star

    I am attempting to calculate the proportional luminosity of a fictitious star using surface area and temperature in kelvin. To what level of accuracy can I expect from the formula L ∝ AT^4? Where L = Luminosity, A = surface area and T = Temperature L ∝ AT^4 L ∝ 4π · (r)^2 · (T)^4 If I replace...
  8. Natanis_Likens

    Exploring the Works of Physicist Norma G. Sanchez & Star Analysis

    There's a some things I've been wanting to look into for a while now I just don't know where to access that kind of information. 1. I'm interested in any information/journals concerning Physicist Norma G. Sanchez (I might be wrong on her title, please correct me if I am) work on a unifying...
  9. F

    B Can a T-tauri star degenerate into a Brown dwarf?

    Can T-tauri stars, due to the fact that they loose matter, become a Brown dwarf?
  10. T

    B What is the best source for this star data? (M44 Beehive Cluster)

    Hi I need the below data for the thousand or so stars in M44 the Beehive Cluster. What would be the easiest way to get this data? Thank you. RA, Dec, distance, apparent magnitude, absolute magnitude, spectrum
  11. E

    I Solving Spherically Symmetric Static Star Equations of Motion

    Hi guys, I can't seem to be able to get to $$ (\rho + p) \frac {d\Phi} {dr} = - \frac {dp} {dr} $$ from $$T^{\alpha\beta}_{\,\,\,\,;\beta} = 0$$ the only one of these 4 equations (in the case of a spherically symmetric static star) that does not identically vanish is that for ##\alpha=r##...
  12. J

    B Does the Nemesis star exist?

    Does the Nemesis star really exist? I don't think it does. If the Sun had a companion star it should have been detected by now. Stars don't go hidden.
  13. C

    A Has the merger of a neutron star and an anti-neutron star been modeled?

    If a neutron star and an anti neutron star collided, would they 1) completely annihilate each other, 2) form a black hole, or 3) partially annihilate each other with the remaining stars being pushed away from each other by the energy created?
  14. PeterDonis

    I Physics Error in Larry Niven's "Neutron Star

    In the short story "Neutron Star" by Larry Niven, the narrator, Beowulf Shaeffer, is piloting a spaceship on a hyperbolic orbit that is supposed to make a close approach to a neutron star. He says at one point that he sees incoming light from distant stars blueshifted in all directions, and...
  15. C

    I Is it possible to unbind a neutron star?

    Type 1a supernovas unbind a white dwarf. Is there some theoretically possible scenario in which a neutron star could be unbound and thus turned into degenerate matter or even regular matter? For example, by a high speed glancing collision with another neutron star or by tidal disruption by a...
  16. S

    I How far away are stars in a typical star cluster from each other?

    I'm trying to grok what this would look like to an observer on an Earth-like planet around a star in the center of such a cluster.
  17. Haorong Wu

    I May I treat the light from a star as a light beam?

    Hi. I am studying the wavefront evolution of light from a star. In the papers I have read, the star is often treated as a point source and the light is approximated as a line (geodesics), but this approximation is not very useful when I study the wavefront evolution, so I want to extend the...
  18. anorlunda

    I JWST Image Reveals Processes Ejecting Material in Star Formation

    Thanks to the JWST, we have this stunning picture. The APOD description says What are the processes that eject material at this stage?
  19. K

    I Primordial neutron star -- a new candidate for dark matter

    could this explains the 3rd peak of the CMB and dark matter cold Primordial neutron star High Energy Physics - Phenomenology [Submitted on 7 Sep 2022 (v1), last revised 12 Sep 2022 (this version, v2)] Primordial neutron star; a new candidate of dark matter M. Yoshimura Z-boson exchange...
  20. Astronuc

    Long-lost star catalogue of the astronomer Hipparchus

    https://www.scientificamerican.com/article/first-known-map-of-night-sky-found-hidden-in-medieval-parchment/ Hipparchus worked on the Greek island of Rhodes three centuries before, roughly between 190 and 120 BC, astronomer Claudius Ptolemy in Alexandria, Egypt compiled a star catalogue...
  21. Sciencemaster

    I Database of binary star data info within 10 PC of Earth

    I'm looking for a database of binary stars within 10 PC of Earth, including information such as eccentricity of orbits, their distance from one another, etc. I'm hoping to find a list with this information, or just a collection of pages with this information. I've tried Simbad but I can't find...
  22. D

    B Neutron Star Merger Shrapnel

    Basically, after seeing a meteor transit our atmosphere below 30,000 feet altitude too fast for my eyes to register yet leaving what looked like a beam of plasma from hanging from 1 side of the sky to the other for 3 seconds which I realized was a trail of smashed atoms of the atmosphere that...
  23. BillTre

    RIP Nichelle Nichols, aka Lt. Uhura from Star Trek

    Actress Nichelle Nichols, best known for her groundbreaking portrayal of Lt. Nyota Uhura in “Star Trek: The Original Series,” has died at age 89, of natural causes. Besides being on the first Star Trek show, she was also central to some important racial firsts on US TV: The Rev. Martin...
  24. BWV

    I Help me on the timeline of star formation in the early Universe

    Referencing this posted on the Webb thread: https://www.quantamagazine.org/two-weeks-in-the-webb-space-telescope-is-reshaping-astronomy-20220725/ So will they able to do spectroscopy on GLASS-z13, the galaxy dating 300M after the big bang? Do they expect to see any heavier elements in a galaxy...
  25. bbbl67

    I Strange Star Physics: Existence of Baryons?

    I wasn't sure if I should post this in astrophysics or particle physics, so I'll try particle physics first, mods feel free to move it to a more appropriate forum. So I was wondering if hypothetical Strange stars exist, would the strange quarks arrange themselves into baryons (i.e. Lambda-0 or...
  26. K

    B Object Weight on Magnetar vs Neutron Star: Attract or Repel?

    Probably a misguided question, but would the intense magnetic field of a magnetar increase the overall pull an object would feel at the surface of the magnetar as compared to a regular neutron star? Or would it possibly lessen the amount of gravitational pull the object would feel at the...
  27. T

    B Is it possible for a giant star to have a black hole inside it?

    I’m sure that when a star is in the process of becoming a black hole, there must therefore be one inside it at some point during the process (correct me if I’m wrong on that). But if so, how long does that take? Could there exist a supergiant star that has a black hole inside it for a long...
  28. B

    I Lateral offset from a centered star as measured at the focal plane

    Hello, I need a bit of help. My age and fading competence are showing (no complaints, just facing up to it). I have an optical SETI observatory in Panama with a 20" Newtonian and a piggybacked 14" Cassy. I wish to mask a portion of stellar Airy disks with an E-W wire on a small photometer...
  29. DhruvSorathiya

    I Could the Sun burn an image sensor of a star tracker in space?

    Hello, I have a question. If a star tracker in space faces the sun directly then could it be possible that the sun completely burns the image sensor? To be specific we are a student satellite team (Student satellite program IIT Bombay) developing a star tracker and we don't have an exact idea...
  30. C

    Can't find total resistance in a complex star circuit

    [Thread moved from the technical forums to the schoolwork forums by the Mentors] Hi i have this assignment for homework: There is only one battery for the circuit, E=10V, R=4 Ohms and L=1H it asks me to find the time constant of the circuit. i know that a time constant in a RL circuit is t=L/R...
  31. Melbourne Guy

    Hiding an orbital colony 'behind' a planet from a flare star

    So, I think it's possible to place an object in an orbit such that it remains perpetually in the planet's shadow, like in my awesome graphical representation. But is it?
  32. T

    Stargazing Size of Star Images: Electronic Effect, Feynman Paths, or Daft Question?

    Images of stars taken by Earth based telescopes can be enlarged by atmospheric fluctuations, but images of bright stars taken by Hubble are also large. Is this the result of some electronic effect in the camera pixels whereby the intensity of light falling on a pixel can cause adjacent pixels to...
  33. M

    What kind of fusion do you think Star Wars has?

    Fusion power is mentioned a lot in Star Wars. In the Bad Batch arc of the second to last season of Clone Wars, the Separatist facility was powered by a fusion reactor. The A-wing is powered by fusion. GNK droids are walking fusion batteries and they have made fusion furnaces the size of a small...
  34. plin092

    B What is the oldest of each class of star?

    Hello! I would appreciate it if anyone could help me figure this out. I’ve been struggling to find info on my own but so far nothing’s turned up. I am a little confused on the timeline of the generations of stars. I know that our sun is considered an early Population I star. However, I could...
  35. diogenesNY

    Stargazing Hubble Spots Farthest Star Ever Seen

    From NASA.gov Mar 30, 2022 Record Broken: Hubble Spots Farthest Star Ever Seen. NASA’s Hubble Space Telescope has established an extraordinary new benchmark: detecting the light of a star that existed within the first billion years after the universe’s birth in the big bang – the farthest...
  36. ergospherical

    Radial oscillations of a star

    So far I have not made much meaningful progress beyond two equations; \begin{align*} \rho \frac{D\mathbf{u}}{Dt} = - \nabla p \implies \rho \left( \frac{\partial}{\partial t} + u \frac{\partial}{\partial r} \right)u = - \frac{\partial p}{\partial r} \end{align*}and thermal energy:\begin{align*}...
  37. M

    B What happens to the Core of a main sequence star as additional mass is added?

    So there is a post going around the facebook groups about what would happen if we could pour a Sun sized bucket of water onto the sun, the claim being that the sun would gain mass and become a bigger, hotter burning blue star. I know this cannot happen but I was just curious as to what would...
  38. dlgoff

    Star Trek the Next Generation - The Inner Light

    I just watched this episode of Star Trek the Next Generation; The Inner Light. One of my favorites. edit: I just found this from a google search
  39. OJ Bernander

    A Dustball Collapse & Evaporation: No Black Hole Singularity

    This old nut is often dismissed as flawed thinking by a naive student. It’s been discussed here too, I know. However, when you do the math in standard (Schwarzschild-like) coordinates: Dustball collapse and evaporation in standard coordinates (Arxiv) A. the (coordinate) speed of light...
  40. Istiak

    Find the energy which was released when the 'Death Star' was destroyed

    > In the movie "Star Wars: A new Hope", Luke Skywalker blows up the 'death star'. Assume that the 'death star' is a perfectly spherical spaceship with uniform mass distribution. The mass of 'Death Star' ##M=1021 \mathrm{kg}## and the radius ##R=667\mathrm{km}## Estimate the amount of the energy...
  41. H

    I Gaia vs DESI: Comparing Largest Star Maps Ever

    I've read that ESA's Gaia space observatory has created the "richest map of our galaxy (and beyond)" https://www.esa.int/Science_Exploration/Space_Science/Gaia/Gaia_creates_richest_star_map_of_our_Galaxy_and_beyond Meanwhile, it's been widely reported tat the "The Dark Energy Spectroscopic...
  42. dlgoff

    Exploring the Unknown with Darmok: Star Trek: TNG

    I'm watching what I think is the best episode of Star Trek: The Next Generation: Darmok: https://en.wikipedia.org/wiki/Darmok
  43. S

    B So, a black hole and an antimatter star bump into each other....

    This is a bit hypothetical obviously as I doubt the conditions for this scenario would ever occur in the real universe. Imagine a black hole, about 10 solar masses. It is, amazingly, sitting in an area of space that is a perfect vacuum. Just by chance, a rogue antimatter star of exactly the...
  44. B

    Statistical physics, using the ideas of Fermi Energies, etc. for a star

    a) V=(4/3)pi(r^3) N=M/m_n (M=mass of neutron star, m_n=mass of neutron) Subbed into E_f = (hbar^2 / 2m) (3(pi^2)N / V)^(2/3). T_F = E_F / k_B b) dU = (dU/dS)_s dS + (dU/dV)_s dV p = -(dU/dV)_s dV V=(4/3)pi(r^3) -> r = cubedroot(3V/4pi) subbed into U_g = -(3/5)(G M^2 / r) take (dU/dV) plug into...
  45. X

    I Is the Sun a low-mass star or a medium-mass star?

    In many text, the Sun is referred to as a low-mass star, yet it is also referred to as a medium-mass (or intermediate-mass) star in some other text. Which one is "correct"? What is the range of low-mass vs medium-mass? Is it really just low-mass vs high-mass and that medium-mass is just the...
  46. Grinkle

    B Maximum mass of a neutron star

    I read this - https://www.sciencedaily.com/releases/2018/01/180116093650.htm And I see this - "However, there are indications that a neutron star with a maximum mass would collapse to a black hole if even just a single neutron were added." And I think the maximum mass of a neutron star is...
  47. H

    B Navigating To Another Star System

    I assume that as the light years to another Star reduce the position of the Star will change relative to other references in the navigation calculations. So what adjustments would be necessary to a Starship's course as it gobbles up the distance to maintain pointing it's nose at the destination...
  48. Bm23

    Stargazing Star appearing to move ping pong like rapidly

    My self and others are curios what could have caused what look as if it was a star suddenly and multiple times with in a 5 min period to ping-pong around rapidly and what looked like it had to be over vast areas of space i read a thread where some one asked the same question but it was several...
  49. D

    Star Opacity and Balmer Break

    I am not sure where to start for this. Considering it needs to be demonstrate Balmer Break, I am assuming it needs to be wavelength based. As a result I am assuming I cannot use mean (Kramers) Opacity but rather express in terms of Opacity k= n*sigma/rho. My thoughts are to use Boltzmann...
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