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How do scientists monitor the Sun's activity?

  1. Feb 5, 2012 #1
    Hello! I just want to humbly ask how do scientists and agencies like NASA, ESA, etc. monitor the activity of our Sun?

    For example, if Solar storms are occurring in the Sun, how do we know it from Earth?

    And another specific question:

    We know that in about 5 billion years (is this correct?), the sun will end its main sequence phase and enter being a Red Giant, as it loses Hydrogen fuel in its core.

    Hypothetically, should we (human civilizations) lived up to that era, how can we know that the Sun is losing hydrogen and enter its Red Giant phase? This is based on our present technologies and machines.

    Thank you! Sorry for any wrong statements I may have made above, should there be any.
  2. jcsd
  3. Feb 5, 2012 #2


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    Staff: Mentor

    There are a multitude of telescopes and spacecraft that observe the Sun every day. Here's a couple of links to more information.


    The Sun will gradually warm over it's lifetime, and upon hitting the boundary between a main sequence star and the Red Giant phase it will greatly expand and brighten over the course of a few million years. (a very short time on the scale of stellar evolution) It will be obvious that the Sun is approaching the Red Giant phase, we quite literally couldn't miss it even if we wanted to. (Especially considering that even if the Earth was still habitable at this point in time, the process would cook the Earth well before the Sun expanded to the point that it took up Earth's orbit.)
  4. Feb 5, 2012 #3
    - Thanks for the links! I'll look into this!

    Yes, I've learned about this as I've read. Thanks!

    Haha I see. Yes it would be obvious. But if I may ask, how obvious would this be from the Earth's (and the people's) point of view? I mean as the Sun goes through the giant phase, if we are still around hypothetically, how would we be able to witness it first hand?" I mean if the earth would be cooked, it would not be cooked instantaneously, right? Because this would progress over millions of years. Correct? (I apologize if it does not make any sense. It's kind of hard to explain it in words, haha)

    I don't know if there's such a thing, but can scientists and agencies like NASA monitor the sun's "hydrogen level" in its core?

    Thank you very much! I'm sorry for the persistent questions :))
  5. Feb 5, 2012 #4


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    People build detailed mathematical models of the sun, and calibrate them against observations, so we think we understand the interior of the sun very well. Below are some links. We can observe neutrinos coming from the sun, and these come directly from the core, so we have good observational evidence of the conditions deep inside the sun.

    The standard solar model (SSM - see the second link below) says that the mass fraction of hydrogen in the core (referred to as X in the SSM) has already dropped from its initial value of 70% by mass to 33% by mass, so the sun has already burned up over half of its hydrogen fuel in its core.

    As others have said, long before the sun enters its red giant phase, the Earth will have become too hot for humans to live. The sun gradually warms as it burns up hydrogen, and we think it has already increased its luminosity by about 30% from its initial value 4.5 billion years ago.


  6. Feb 5, 2012 #5


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    We would see the sun warming, getting brighter, and eventually start to expand. Not really sure what you are asking.

    Not directly, but we might be able to measure the reaction rate via neutrino detectors and can infer a lot from observing the outer layers of the sun.
  7. Feb 17, 2012 #6

    Thank you!! This helped a lot and got more idea especially with the neutrinos! So as the Sun consumes its hydrogen fuel and increase its brightness, Would the Sun have lesser reaction rate, and expect lesser neutrinos detected here on Earth, or would it have higher reaction rate and have more neutrinos detected here on earth?

    And also, as the Sun loses its mass, can we also calculate how much mass is lost by calculating the amount of solar energy transmitted by the Sun? Because the For every reaction, a small percentage of the mass is being converted and energy, correct? So could we apply the mass-energy equivalence (E=mc^2) here?
  8. Feb 17, 2012 #7
    Thank you this helped a lot!

    So as the Sun consumes its hydrogen fuel and increase its brightness, Would the Sun have lesser reaction rate, and expect lesser neutrinos detected here on Earth, or would it have higher reaction rate and have more neutrinos detected here on earth?
  9. Feb 17, 2012 #8


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    I'm not certain, but if it's increasing in brightness then that should mean the core is producing more energy through more nuclear reactions. I would expect a greater neutrino flux. I really don't know though.

    Yes, the neutrinos, emitted radiation, and solar wind all carry mass away from the Sun.
  10. Feb 17, 2012 #9


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    Here is a very interesting NASA SDO video of what appear to be tornadoes - and all sorts of other peculiar activities - on the surface of the sun.

    Respectfully submitted,
    Last edited by a moderator: Sep 25, 2014
  11. Feb 25, 2012 #10
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