Dr. SOHO's FAQ: The Sun


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  • Does the Sun have a name other than "The Sun?" Any star can be a sun, but we give names to other stars. What about ours?
  • Is the Sun the brightest star?
  • What is the chemical composition of the Sun? (if you can, list the elements and percentages, etc.)
  • What is the surface of the Sun like? Is it solid, soupy, or just gas that (assuming you didn't burn up) you would pass right through?
  • My son and a few of his 7 year old friends were wondering about the temperature of the Sun. Specifically, how did you figure out the temperature of the Sun? How do you measure the temperature of the Sun, or is it just an estimate? Thank you for your help.
  • Where is the coldest part of the Sun?
  • Does the Sun weigh as much as the Earth?
  • What is the typical variation of the Sun's output during the calendar year? Is this variation noticeable on Earth? How about in space? How drastic are changes in the Sun's corona?
  • What kind of particles is the solar wind made of?
  • Is it possible to mimic solar wind experimentally?
  • Could the power of the solar wind be harnessed and used somehow in the future?
  • I saw on the news that the Sun has a recurring event every 6 minutes but we don't know what the event is. Can you elaborate?
  • How close can you get to the Sun without burning up?
  • I was wondering, why is the Sun darker than it was 20 years ago? What else can we expect from the Sun in the near future?
  • Is information available detailing solar intensity variations in the visible spectrum on various time scales? If so, over what dynamic range, to what accuracy, and is a standard time tick available for correlation purposes?
  • Given that the Sun is tossing out matter in eruption events and converting mass to energy in fusion, is there any data on the net change in mass of the Sun?
  • Have there been any data collected by SOHO which help explain the discrepancy in solar neutrino flux?
  • I am curious about the known forces acting within the sun. I am aware of gravity, which is a function of its mass. I know a little about the energy released with nuclear fusion, which is where the energy comes from in the Sun (I believe). Of course, there are electromagnetic forces which are evident in the aurora borealis; I do not know where this plays in the overall picture of the Sun. Are these the forces acting in the Sun? Do we know about any other forces which have some effect on the Sun? Gravity is the one that interests me because it is both the weakest and strongest of forces as I understand it. I would very much appreciate your comments on this topic.
  • How do scientists know that the Sun has a core?
  • Dear Doc, Do we know that the Sun has a dense core (13 to 14 times the density of lead), and if so, how do we know?
  • Sirs: I have heard that observational evidence is questioning the accepted theory that the Sun has a core. Is this in evidence through SOHO?
  • Is the Sun solid?
  • Please, how can I find daily sunspot index (Wolf numbers) at SOHO www-pages?
  • Lately, the folks into conspiracies and paranoid, paranormal subjects have been talking about the Sun's huge emissions of energy. I realize that if the Earth were hit by a massive particle ejection, as in April 1997, there might be widespread damage to satellites and power systems. I am curious, though: is our Sun behaving more erratically than usual? Was there a particle ejection in early November 1997 more severe than the April 1997 event? Is this above-mentioned activity something that we endure every decade or so?
  • Is there any measurement of the Sun's corona expansion rate? Let's say, how many kilometers or miles per year the Sun grows.
  • Hi, Dr. SOHO. I have a question about Lyman Alpha emissions. From what I know, Lyman Alpha has something to do with recombination of electrons in hydrogen atom (from n=2 to n=1). This means that the hydrogen atom should still have the electrons orbiting around the nucleus. But the chromospheric temperatures in the Sun are above 10,000 degrees Celsius. At this temperature, I thought that electrons would be stripped away from the hydrogen atom. Can you tell why I am wrong? What is the source of Lyman Alpha in the Sun???
  • What are the causes of the influence of the Sun's magnetic waves?
  • Is the solar wind continuous from here to the Sun? Is the solar wind always a plasma? How does the ion concentration decay with the distance from the Sun? As R2?
  • Is the Sun expanding or contracting, and at what rate?
  • Holding an Amateur Radio License, I am interested in sunspots, but have difficulty in determining which images are or are not sunspots that affect radio communications. Can you enlighten me?
  • How many years will it take before the Sun explodes or disappears?
  • With pollution/ozone levels as they are today (and I am assuming they will only get worse), how does this affect the Sun? My mother has always said, "According to the Bible we are all going to go by a destructive fire." Today she says, "I know what is going to happen. . .the Sun is going to blow up."
  • I'd like to know how the magnetic axis, the rotational axis, and the ecliptic relate to each other. Also, are the Sun's axes stable and well- understood? Do they drift or wobble? Do the magnetic poles ever shift? If there is an offset between the Sun's axes and the ecliptic, does this manifest in aspects of the solar wind?
  • I was looking at a paper on the Earth's radiation environment, and it referred to the August 1972 solar event. What event was that?
  • For my Advanced Physics class in high school, we need to find out if the Sun has different temperatures at the surface vs. the center of the Sun. Which is cooler or hotter, if there is any difference? Also, is there a difference in density between the surface and the center?
  • What are some practical applications for the rotation period of the Sun? So far, we have only been able to come up with an flimsy idea concerning the amount of sunlight a plant receives, in respect to the rotation period of the Sun. Secondly, are there any useful sites where we could gather additional information?
  • Could you please advise me on how scientists were able to calculate how big the Sun is, or where I can obtain this information?
  • What kind of star is the Sun?
  • How is the amount of hydrogen in the Sun measured? And how do we know so much about it? It came up in science class where we are studying astronomy, and I'm interested in knowing about it. Thanks for your help.
  • Dear Sir: I would like to find out about: 1. the shape of the solar magnetic field 2. its observed components - e.g., dipole and other Could you please advise where I can find these. Thank you.
  • I perform at the Arizona Renaissance Festival. My character is a scientist and is tutor to the Prince. I use this role to teach science to children at the festival.

    (I am an engineer who loves science and math. To me they are fun as well as interesting. Most kids today are taught science and math as a required topic. They are told these are difficult and required. I tell them science is fun and exciting.)

    Typically, I perform 8 times a day to audiences ranging from 4 to 30 kids. I am very hands-on and allow the kids to dictate the direction I go. I currently have "experiments" that demonstrate sublimation, magnetism, combustion and two different exothermal chemical reactions.

    I would very much like to add a solar telescope. I believe I can really turn kids on to astronomy if they can observe sunspots and/or solar flares. Living in Arizona, in spite of this year's el Nino storms, I have a great opportunity to demonstrate a solar telescope.

    Can you provide guidelines for constructing a (relatively) inexpensive solar telescope? Any help you can give will be appreciated.

  • When will the next solar eclipse be?
  • Is the solar corona/wind electrically neutral? If there was a charge imbalance, could it be detected by your instruments if the concentration of charged particles is about 12 parts per million by weight of the solar wind?
  • I would be thankful if you could give me information on the recent published discovery of a magnetic carpet on the surface of the Sun. I would like to know, technically, how the magnetic carpet works and how it was discovered by SOHO. (measurements and such) If you know of any other references I could contact, it would be very helpful. Thank you and I hope to hear from you soon.
  • How do you interpret the elongated, S-curved flow of plasma[?] which is imaged at approx. 02:00 (northwest) on the EIT image in He II 304 Angstrom, taken at 13:19 UT on 31 May 1997? Is this a prominence which we view half as a filament and half as prominence at 60,000 K via the EIT image? Once again I would like to thank the SOHO scientific team for the opportunity to follow this fascinating experiment.
  • I have been hearing talk lately of an increasing likelihood of major solar events to begin occuring in the next few months and culminating with a disastrous finale in 1999. Is it true that solar activity is on the increase? Is this Solar Cycle 23 that I keep hearing about as menacing as some have predicted? They say that we will experience X-ray and gamma ray radiation here on Earth the likes of which we have never before encountered in recorded history. Some have gone as far as to predict the end of life on the planet as a result of a cataclysmic event before the year 2000. I am a bit concerned over the rumors and thought I would inquire with people that follow this activity as their life's work.
  • I'm trying to track down a very brief report that I saw in the paper some time ago and, unfortunately, failed to clip. It said that the Sun appeared to be warming up very slightly -- i.e., there appeared to have been a small increase in the solar constant. Could anybody there help me track this down?
  • I am interested in Sun photometry as a means of measuring haze. In working through the basic calculations that are usually performed, I have encountered two difficulties that, as far as I can tell, are simply ignored by those working in the field It is my hope that NASA may have data that will allow these calculations to be put on firmer ground. My questions are:

    1. The assumption that is usually made in the field of Sun photometry is that the output of the Sun is constant within the narrow wavelength being measured. Of course, the output is almost certainly not exactly constant, so the question is really how much variation one can expect over various time intervals. I suspect the variation is small, but the accuracy of an instrument can't be determined without this vital information. There is a lot of data (for example, from NASA) regarding total output and for wavelengths below 400 nm. However, I need data for 525 nm and other wavelengths above 400 nm. Does NASA have such data? If not, is it planning to gather such data?

    2. This question is in regard to calculating the Sun-Earth distance. I know how to make the calculation but have been unable to determine error bounds for the calculation. I am familiar with DE200/LE200 and have looked at Chapter 5 of the "Explanatory Supplement to the Astronomical Almanac" which gives a great deal of information about the calculation. However, that mathematical model was adjusted to various observations. Although the maximum error for some of these observations is given, I do not understand how one goes from the observation error bounds to the error bounds for the Earth/Sun distance. Where can I obtain the Earth/Sun distance error bounds?

  • Could you please explain to me how energy escapes the Sun? Thank you.
  • I am wondering how long it would take for the fastest possible signal to transit from the core of the Sun out to the surface of the Sun. The issue is the density is far greater than with normal dielectrics, so the velocity of propagation ought to be far slower. But with the density gradient from core to surface, it gets complicated. So, how long would it take for an EM signal to transit the radius of the Sun, assuming it took a direct path (i.e., ignoring scattering).
  • I am trying to find detailed data for densities/temperatures of the solar atmosphere out to many millions of kilometers if not out to 1+ AU. I figured SOHO might have been used to collect such data or that you might know where to look. Has SOHO been used to study the solar atmosphere in detail? Where (else) should I look?! I have found such data out to 400km, but no further. I have spent days in university and college libraries to no avail. (FYI: I have a B.S. in math/physics from the '60s and a general background in science.)
  • Hi, I am 7 years old and I was wondering... how does the Sun just sit there? What is holding it in place and keeping it from falling or moving around?
  • Is the Sun moving in space? At what speed? Where is it going to? Where does it come from? Does it encounter other celestial bodies going through its path, and how do we know of such encounters? Many thanks for your time and commitment.
  • I was curious about how I can view those photographs of tornadoes on the Sun. Also do you have any charts on your site about sunspot and electromagnetic activity over a long period of time?
  • I heard on the news about the tornadoes on the Sun the size of Africa and the wind speed of over 300 mph. I was just wondering, how do they measure the wind speed on the Sun?
  • My question for you is: I don't understand how there can be solar wind. I thought there was no friction in space. I was under the impression that there has to be some kind of resistance that causes friction which in turn causes wind. If you could just explain to me how solar wind is created, I would be grateful.
  • I have a quick and short question on the sun. We know that the sun is a ball of fire basically but in order for fire to be you need to have Oxygen, not to mention a fuel of some type in order for it to continue to burn.

    My question is that if there is no oxygen in space how is it that fire is possible, also what fuels are their for the sun to continue to burn? I don't know much about space this is why I ask you this question out of curiosity and the need of knowledge on this topic.