Read about sun | 57 Discussions | Page 1

  1. mollwollfumble

    B Linear dark features on the Sun

    I’ve been watching =AT2AcUch2CYj2r40rQ431p1Rt1SQ-YzVLo-ryJHYFIT8s9ZlMJ5pcWH9lN17FRuz2eLTlNPVb4fP2yk4PPLqjJK_6lpeWheAbATLZd7foljjUg2sOFxm-mZbhhcw3G9ApCzWIWNjgBGcGjoXMqdW6Jv-Rb8P2yA']https://www.youtube.com/watch?v=l3QQQu7QLoM What is the scientific name of the enigmatic long linear dark features...
  2. E

    Question about variations of the Sun's path over long periods of time

    Hello. I am a filmmaker writing a screenplay and I am in need of technical support to validate a method being used in the film. I am going to post this in the Earth Science forum but I'll copy it here, in case anyone reading this might know. Thank you all! "I am wondering if shadows cast...
  3. thebosonbreaker

    I Confusion over what exactly constitutes the ecliptic

    When first introduced to the concept of the ecliptic, I was under the impression that the ecliptic was the path taken by the Sun across the sky over the course of a day. That is to say, the rising in the east and setting in the west, due to the Earth's (daily) rotation from west to east. (Image...
  4. artworkmonkey

    Calculate the density at the centre of the Sun

    Homework Statement Assuming you know the core mass, and other data about the sun, such as temperatures and pressures. Find the density at the very center of a star. Homework Equations I think this may be involved. P(r) = p(r)/µmH kT(r) The Attempt at a Solution [/B] I don't know where to...
  5. artworkmonkey

    Sun question: Determine the velocity of the gas

    Homework Statement From near to the center of the solar disc, Fe I line emission from point X shows a spectral line with components 666.823, 666.830 and 666.837 nm, around the rest wavelength of 666.800 nm. The central component is not as bright as those at the longer and shorter wavelengths...
  6. V

    A Calculation of the "lightness number" for solar sails

    Hello, In the wikipedia article about solar sails the lightness number is mentioned and the calculation is the characteristic acceleration ac divided by the Sun´s local gravity (distance: 1AU): λ = ac / 5.93 why do they use 5,93 m/s^2 for the sun´s gravity and not 274 m/s^2?
  7. N

    Stargazing Is there any material I can use for an aperture solar filter?

    I live in a small town and would like to make some observations today. However i dont have a solar aperture filter, i only have an eyepiece filter of which i do not trust. So is there any household items, materials i could use safely to save me from from ordering on the net and waiting however...
  8. YoungPhysicist

    I Is the Sun a black body?

    Black bodies are objects that don't reflect radiation. But If I shoot light beams to the sun, it doesn't reflect it , so does that mean the sun is a black body(or at least very close to a theoretical one)?
  9. K

    Coordinates: Sun?

    What are the coordinates for the sun? ?
  10. J

    I Which object will hit the surface of a planet first?

    If we have two objects A and B appear on the opposite sides of the equator of a planet like Earth with the same mass as Earth. Object A is a neutron star with the mass of the sun and object B is a iron cube with the mass of one gram. Will A or B hit the Earth at the same time or will one hit...
  11. mjda

    I How to describe the Sun's interior?

    My question to you is this... Can the interior of the Sun be described as an ideal gas? From my knowledge, to describe a body of gas as an ideal gas, the separation between the particles must be much greater than the size of the actual particles. How could one justify whether the Sun fits this?
  12. klotza

    Insights Either the Sun Is Getting Smaller or Gravity Is Getting Weaker

    Greg Bernhardt submitted a new PF Insights post Either the Sun Is Getting Smaller or Gravity Is Getting Weaker Continue reading the Original PF Insights Post.
  13. D

    I Star formation and heavy elements

    Hello. First post here so hi all. My question(s) is regarding the formation of solar masses by accretion of gases and dust. From what I understand, stars are formed by large clouds of gasses and dust particles pulling together and with enough gravity, (magnetic fields), and time. A fusion...
  14. shihab-kol

    B Expansion of stars

    I read in some books that as the sun approaches the end of the fusion process(the complete one) , it will expand and engulf some of the inner planets. But why will it expand?
  15. P

    I Electromagnetism in the Lithosphere and Ionosphere

    Hi guys, Disclaimer: not a physicist (I wish I was that brainy) Quick question regarding a speculative architecture project I am undertaking; In the completely hypothetical event of a huge, otherworldly solar flare super-charging the earth's ionosphere beyond anything we have ever recorded...
  16. davenn

    Stargazing Solar imaging and techniques

    Hi everyone This thread is for showing your images of solar activity taken with YOUR cameras, telescopes etc. That is, don't post images from SDO, SOHO or any other professional sources unless you specifically want to ask "how do they do that and what are those solar features I can see? This...
  17. D

    Is the sun telling us something?

    Sometimes it looks like there is a message here. Sun on 9/8/2017 - wavelengths 211, 193, 171 from http://sdowww.lmsal.com/suntoday/index.html?suntoday_date=2017-09-08 Beautiful!
  18. C

    B How long does it take for the temperature on Earth to....

    How long does it take for the temperature on earth to cool down after the sun has set? I want to know if the total solar eclipse will change the temperature.
  19. J

    I Calculation of daily solar insolation

    Hi all, I'm trying to calculate the daily solar insolation (integrated solar irradiances from sunrise to sunset) for a given location and day of the year. For latitude 43.2° and April 15th, I get: H0 = (solar constant * scale factor for intra annual variation of sun-earth distance * 86400...
  20. J

    I Calculation of the hour angle of the Sun

    Hi all, According to the sunrise equation, the hour angle of the sun at sunset is: cos H = -tan(a)tan(d) where H = the hour angle, a = latitude and d = solar declination angle. This equation says that H at sunset = -H at sunrise. Now, I have a few questions concerning that: 1) I was...
  21. Chracatoa

    How often does the moon orbit intersect with sunset?

    Bear with me, this is a very specific question for a scifi book I'm writing. If we had a ring in place of the moon, and you lived somewhere in the United States, how often would the ring intersect with the sun when it's setting (or rising, if it makes it easier). I know that it can take up to...
  22. R

    Trees are natural

    A tree seed takes water and minerals(?) from the ground, carbon and oxygen(?) from the air, and heat and light(?) from the sun. When a tree dies and dries up, it can be used as firewood, a source of energy. Is there a way to capture that energy without the seed-tree scenario? i.e., but can we...
  23. MKP81

    Earth rotation speed if it was tidal locked to the Sun

    Dear Forum, I am filmmaker from Berlin and despite physics focus back in high school I am really bad at it. I am trying to get my head around some ideas I am working on and would kindly ask you for some tiny calculations. I hope this is OK and maybe even fun for someone here? So my questions...
  24. A

    I Percent of stars in our galaxy that belong to clusters?

    Of all the stars in our galaxy, how much of them belong to clusters?? Is our sun rare in terms of not belonging to any cluster? I can't find any sources on that
  25. SamP37

    B Energy output of a nuke

    Helly everyone. I'm new in physics and I don't understand many things there. What interests me the most is energy generation. I was mostly reading Wiki articles, and I found something I couldn't understand, so I'm asking for help. According to wiki, peak power output of the largest nuke ever was...
  26. Jadaav

    I RA and declination of Sun & phase of Moon program

    Hello there, I want to write a fortran program which gives me the right ascension and declination of the sun and the phase of the moon when a date and time is given. I just want to know how to write it and if there are any references that can help me. Thanks, Jadaav.
  27. xpell

    B When are we "trailing" the Sun in its galactic revolution?

    Hi! I guess this question must be easy, but it's driving me crazy: in what time of the year does the Earth "trails" the Sun in its current galactic movement towards Vega? And, could you please confirm that during this period Vega is not visible because it's always facing the "day side" of the...
  28. J

    A Why 15 million K is sufficient for fusion in solar core?

    Wikipedia says that solar core has 15 millions of Kelvins ( https://en.wikipedia.org/wiki/Solar_core ), what translates into ~1.4 keV energy per degree of freedom. For nuclear fusion we need to take the two nuclei to distance of range of nuclear forces: ~1fm (...
  29. bri7

    Astronomy : Velocity of approach of the Sun's equator

    The sun's rotational period is 25 days at the equator. Given that the radius of the sun is 700,000 km, calculate the max velocity of approach or recession of the Sun's equator as viewed from Earth. Find the max change in wavelength of a spectral line due to the rotation and express it as a...
  30. J

    I How to derive full solar sprectrum from gamma rays

    I understand that the fusion of hydrogen to helium in our sun's core generates gamma rays. My question is how are these gamma rays transformed to the full spectrum of photons that we that we observe from earth?
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