Talk:Sun

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Peace

We are all children of the sun, we all came out of the sun so why do we fight? We all came from one source. —Preceding unsigned comment added by 79.72.91.250 (talk) 21:47, 8 October 2008 (UTC)

Well, here's your ticket back. Bon yoyage! Myles325a (talk) 01:59, 26 December 2008 (UTC)

Extent of hydrogen/helium ionization

I'm in astro 320 at U of Alberta (MT tomorrow :)) and I am confused about the reason why hydrogen is ~100% ionized in Sun's core (T = 1.57*10^7 K; ref. my assignment). To calculate N(II)/N(total), I calculated N(II)/N(I) using the Saha eqn (using electron density = 6.1*10^31 m^-3), and found N(II)/N(total) by noting that: N(total) = N(I) + N(II). Also, I used partition functions, Z(H(I))=2 and Z(H(II)) = 1 (no degeneracy for proton). Anyway, I calculated that N(II)/N(total) = 0.709, or 70.9%. This calculation neglected helium (all hydrogen in sun), but helium would lower hydrogen ionization energy by compressing H's orbitals (is this right? or would it raise the I.E.?) from 13.6 eV, which (I think) would, if lowered, increase the calculated fraction. Conversely, He is also ionized (III or II) producing more `free` electrons to reduce the fraction of ionized Hydrogen. Are there other effects to account for the 100% ionization. —Preceding unsigned comment added by Bizarrini (talk • contribs) 01:20, 15 October 2008 (UTC) - Why hasn't anyone tried to answer my question yet? It's been months... —Preceding unsigned comment added by 75.159.7.47 (talk) 07:22, 3 January 2009 (UTC)

Faint young Sun vs. life cycle

Neither the faint young sun subsection nor the Faint young sun paradox article addresses the fact that the Sun was probably significantly more massive at the time (due to the blowoff by the solar wind in the intervening period, as mentioned elsewhere in the article -- though in connection with the future). This would result in an earth orbit closer to the Sun, thus offsetting the lower intrinsic solar brightness. The radius of the orbit is roughly inversely proportional to the Sun's mass, while the solar flux intercepted at earth's orbit is inversely proportional to the square of the orbit radius. So, if the solar mass was roughly 20% bigger than today, that would have completely compensated for the lower, 70% luminosity. Even if the mass difference was smaller -- understanding that the solar wind was probably less intense than today or in the future due to the lower luminosity, it seems this effect could still have been a significant contributor to the liquid water, in addition to possible greenhouse gases mentioned elsewhere. Are there any references as to how much mass has been blown off from the Sun since it was formed or containing a discussion of this effect?24.58.175.197 (talk) 21:47, 31 October 2008 (UTC)john wilkinson

In a billion years, the current solar wind will remove 0.003% of the solar mass. Later the sun will start to shed mass much more rapidly, but in the current phase of its evolution, the mass change is negligible. Dragons flight (talk) 01:10, 1 November 2008 (UTC)

"Ending all human life"

"The increase in solar temperatures is such that in about a billion years, the surface of the Earth will become too hot for liquid water to exist, ending all terrestrial life."

Really? You presume to say that you know what evolution will produce in a billion years? That not only natural selection will not produce organisms able to live in progressively hotter temperatures, even as the slow transition of the surface temperature crosses the boiling point, but that the descendants of humans and any other intelligent species will not devise a way to live in such a world? zafiroblue05 | Talk 07:05, 17 November 2008 (UTC)

"0.3 watt per m3"

The calculation is not consistent. The actual valvue should be higher, do the math!

Regards, Bart Bozon —Preceding unsigned comment added by 62.234.183.218 (talk) 17:47, 26 November 2008 (UTC)

Needs sources

For an FA quality rating, this article seems to have a lot of material that is not sourced. Would it be possible for references to be added, as appropriate, so as to avoid a future FAR? Thank you.—RJH (talk) 20:54, 28 November 2008 (UTC)

Evidence for fusion

Question for the experts:

What (if any) actual experimental evidence do we have to support the idea that the core of the sun contains hydrogen, and that the primary source of energy is fusion? There's no cite, and no explanation -- and I haven't been able to find anything elsewhere. Ungtss (talk) 06:06, 6 December 2008 (UTC)

Question #2: It is mentioned that the photon travel time is something like 10,000 years to 170,000 years from the core to the surface. It is said that a photon is absorbed and re-emitted multiple times before it reaches the surface. What is the evidence that the 'same photon' is being absorbed and re-emitted? Slight explanation will benefit us. 57.67.164.37 (talk) 08:07, 17 December 2008 (UTC)

Mass of Sun

What is the exact mass of the sun in KG? I guessed something like 1456136933221566562465252,7179234 KG... —Preceding unsigned comment added by 82.168.235.93 (talk) 16:05, 5 January 2009 (UTC)

Well if you read the article and look at the source of the value given for the mass of the sun it takes you to: http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html which says 1,989,100 x 10²⁴ kg. Which should be good enough value for any calculation you are doing unless you want a lot of precision, and even if you want that, if you think about it the sun is loosing mass all the time by converting it to energy in huge amounts and blowing it off in solar wind, so the mass is constantly decreasing.Ergzay (talk) 12:33, 7 January 2009 (UTC)

Speed of the Sun Around the Galaxy

According to "Milky Way a Swifter Spinner, More Massive, New Measurements Show" (http://www.cfa.harvard.edu/press/2009/pr200903.html) by the Harvard-Smithonian Center for Astrophysics on January 05, 2009, the new distances and speeds are as follows:

- 28,000 light-years from the Milky Way’s center
- 600,000 miles per hour (My manual conversion: 268 km/s)

Klabbas (talk) 23:27, 7 January 2009 (UTC)

 Question: The current distance is given to 3sf with standard error. Can you find the accurate data which the article references? haz (talk) 14:11, 8 January 2009 (UTC)

Sun-Overview

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"The solar constant is equal to approximately 1368 watts per square meter at a distance of one AU from the Sun (that is, on or near Earth). Sunlight on the surface of Earth is attenuated by the Earth's atmosphere so that less power arrives at the surface—closer to 1,000 watts per directly exposed square meter in clear conditions when the Sun is near the zenith." This doesn't seem to be correct. At least one of these numbers must be incorrect for the amount of watts per exposed square meter.

"Space based solar energy has long interested NASA and others in the space community because solar energy is eight times stronger in space then it is after it has passed through the atmosphere." Source: http://blog.wired.com/wiredscience/engineering/index.html
— Preceding unsigned comment added by Funkyfu (talk • contribs) 09:20, 15 January 2009 (UTC)

The article is correct. One factor is that in space you almost never get "behind the planet", so you enjoy sunshine 24 hours a day, not just an average of 3 or 4 hours. Putting solar panels in space is not only stupid, but ridiculous, though. What would happen if someone hacked into the beam controls and wiped out Detroit? That is why space based systems have never been developed. They are not needed, and are horribly problematic. The movies Dr. No and Diamonds are Forever use these death ray themes. 199.125.109.37 (talk) 20:45, 18 January 2009 (UTC)

James Bond movies aren't a reliable guide to technology. What would happen if someone hacked into the beam controls is pretty much nothing, beyond the loss of power. The power density of the microwave beam wouldn't be that much brighter than sunlight.

Space-based solar power hasn't been developed yet because thus far it's even more expensive than ground-based solar.

—WWoods (talk) 01:40, 19 January 2009 (UTC)

Link to Nemesis article?

I was surprised to find no mention of the Sun's hypothetical companion Nemesis (star), or any links to its article. I know that its existence is debatable, but as a still unsolved question that relates directly to the sun, I'm surprised to not see it. Should a link be added somewhere, possibly in the 'see also' section? 155.68.113.210 (talk) 21:12, 19 January 2009 (UTC)