# Questions Regarding the Sun

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#### tyguy

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Is it true that the suns core has a density 100 times that of water? Why are the conditions of such a high temp and density needed to account for the observed properties of the sun?<br /><br />Also, I forget the reason, but why does a large star like Sirius (which is about 2 1/2 times more massive) die out much faster than our own sun, assuming it has the appropriate amount of hydrogen compared to our sun?<br /><br />Thanks!!!

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#### weeman

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I'm not exactly sure of its density compared to water, however the Sun does have a density of about 160 g/cm^3, about 10 times that of lead. <br /><br />The immense density of the core is due to incredible amounts of gravitational force. As the pressure at the core increases, so does the temperature. This leads to a point when the Sun's core is hot enough that it can sustain nuclear fusion. It is this fusion that gives the Sun its brilliance and heat. If it weren't for the incredible heat at the Sun's core, nuclear fusion would not take place, meaning we don't have a full fledged star, simply a protostar. <br /><br />I'll let someone else explain your Sirius question, since I am not as informed on that one <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

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#### tyguy

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Excellent, thanks.<br /><br />Astronomy Class Homework for the win <img src="/images/icons/smile.gif" />

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#### 3488

##### Guest
Hi tyguy,<br /><br />Welcome to SDC.<br /><br />Yes the Sun's core density is approx 160 X that of water & a pressure of 250 Billion atmospheres <br />(250,000,000,000 Bars).<br /><br />You mention Sirius / Alpha Canis Majoris.<br /><br />A comparison below.<br /><br />Sun (Left) Sirius (right).<br />Approx Diameter: Sun: 1,392,000 KM. Sirius: 2,366,400 KM.<br /><br />Approx Mass: Sun: 333,000 Earths. Sirius: 712,600 Earths.<br /><br />Equatorial Rotation: Sun: 25.4 Days. Sirius: 5.5 Days.<br /><br />Activity Cycle: Sun: 11.1 Years. Sirius: 3.0 Years.<br /><br />Age: Sun. 4.6 GYO. Sirius 210 MYO or 0.210 GYO.<br /><br />Power output: Sun: 386 ergs* per second. Sirius: 10,036 ergs* per second.<br /><br />*1 erg = 1 Billion Trillion Megawatts or 1 followed followed by 33 zeros or 1 Decillion.<br /><br />Sirius is using up its fuel at a rate much higher than the Sun's. <br /><br />Sirius has a mass of 2.14 times that of the Sun, but is expected at the very <br />most to last 1 GY, before evolving off the main sequence.<br /><br />Sirius is therefore using hydrogen in its core some 19.26 times faster than the Sun.<br /><br />2.14 solar massed star, Sirius, evolving off main sequence when only 1 GYO. <br /><br />1 Solar massed star, Sun, evolving off main sequence after 9 GYO. (9 X 2.14 = 19.26).<br /><br />I am not a nuclear physisist, so perhaps someone who knows more than my <br />ramblings could assist.<br /><br />Sirius is also a metal enriched star (metals = elements heavier than helium), <br />some 4 times that of the Sun.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

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##### Guest
Andrew - you get an A. I'd have given you an A+, but you didn't provide a detailed bibliography.<br /><br />Ty, on the other hand... It looks like you copied Andrew's work. <div class="Discussion_UserSignature"> <p>.</p><p><font size="3">bipartisan</font>  (<span style="color:blue" class="pointer"><span class="pron"><font face="Lucida Sans Unicode" size="2">bī-pär'tĭ-zən, -sən</font></span></span>) [Adj.]  Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.</p><p><strong><font color="#ff0000"><font color="#ff0000">IMPE</font><font color="#c0c0c0">ACH</font> <font color="#0000ff"><font color="#c0c0c0">O</font>BAMA</font>!</font></strong></p> </div>

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#### mindmute

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Andrew,<br />Nice. <--(pronounced the way Col. Jack O'neil would say it.)<br /><img src="/images/icons/smile.gif" /><br /><br />1 question:<br />Sirius is a binary system (perhaps trinary), do/will her sister stars have any effect on her evolution.?

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#### 3488

##### Guest
Thank you very much Adrenalynn, for your very kind comments. <br /><br />I did a lot of research on Sirius a while back & kept the notes <img src="/images/icons/laugh.gif" /> .<br /><br />It is a fascinating subject & Sirius being the brightest STAR in the sky other than our <br />own Sun, is of great interest.<br /><br />I think the more we learn about other stars, the more we learn about our own Sun. <img src="/images/icons/laugh.gif" /><br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

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#### 3488

##### Guest
Hi Mindmute.<br /><br />Very interesting point concerning Sirius B.<br /><br />Sirius B may had rejuvented Sirius, when it ejected the hydrogen rich outer layers, when<br />the Red Giant stage ended & became a White Dwarf.<br /><br />Chances are, there was considerable mass transfer during that period from B to A.<br /><br />Perhaps Sirius is OLDER than the 210 million years, but is like a 210 MYO star due to the<br />death of its partner.<br /><br />Sirius is suspected of being part of the Ursa Major Moving Group, a very loose open<br />cluster, almost dispersed. Five of the stars of the Plough or Big Dipper (not Dubhe & Alkaid)<br />appear to share a common proper motion. Also many other stars are suspected<br />of being direct relations, including a few that are bright, such as Menkalinan / Beta Aurigae, <br />Alphecca / Alpha Coronae Broealis & Sirius / Alpha Canis Majoris. <br /><br />Other stars include: Gamma Leporis, Zeta Trianguli Australis, Zeta Leonis, Zeta Bootis, <br />Delta Aquarii, Beta Serpentis & Gamma Microscopii. Of course there are many others,<br />but I included these as it shows, how fragmented this 'cluster' has become.<br /><br />Sirius was the oxymoron, due to the fact that it appeared to be only about two thirds<br />of the expected age of the Ursa Major Moving Group, yet shares the same proper motion <br />& speed as the others. The mass transfer that may have happened when Sirius B died,<br />does away with that oxymoron altogether. If so, than with some confidence, Sirius B was a red giant<br />& the mass transfer occured approx 160 million years ago.<br /><br />In 64,000 years time, Sirius will appear at its very brightest, as it passes at its<br />closest point to our solar system. It will be at magnitude -1.54, so only slightly <br />brighter than now.<br /><br />Sirius became a naked eye object approx 500,000 years ago, as it closed in & <br />will drift too far away for naked eye visibility in about 560,000 years time.<br /><br />At this <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

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#### alokmohan

##### Guest
Siriusly?Sirius broght flood in ancient Egypt.Not nice guy.Stars who live fast die early like human beings.

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#### 3488

##### Guest
Hi alokmohan,<br /><br />Good to see you again.<br /><br />Sirius did not cause the Nile Flood in Egypt, rather that when Sirius was just visible in the dawn<br />skies (Helical Rising) the time of the year for the Nile flooding was imminent.<br /><br />The ancient Egyptians would notice the stars of Orion rise first, then <br />Mirzam / Beta Canis Majoris (Mirzam = The Announcer i.e of Sirius), they knew that the time of <br />flooding was drawing near, so they would use these, as a warning to leave the Nile Flood plains.<br /><br />But the flooding remember was not a curse, but a life saver. The Nile flood, fertilised & renewed<br />the soils & as a result, the Egyptian people did not starve. <br /><br />When Sirius appeared shortly after Mirzam, in the morning sky, the floods <br />were on the way. <br /><br />Just as when Arcturus made its helical rising, the Egyptian farmers knew it was <br />time to sow seeds. The stars really were an important calender keeping method <br />for ancient Egypt.<br /><br />Very true, stars that do live fast, die young.<br /><br />Think of Rigel. 30 solar mass star, 4 million years of stable life tops.<br /><br />Hydrogen usage compared to our Sun. 30 * 2,250 = 67,500. <br /><br />(30 = solar mass. 2,250 = 9 GY divided by 4 MY).<br /><br />Rigel is using Hydrogen at a rate of 67,500 times that of our own Sun. <br /><br />Despite the 30 solar masses, Rigel is living very fast & will die very young.<br /><br />Not to mention Helium into Carbon, etc (got no idea the rate of that reaction. It is not something<br />happening within our Sun YET).<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

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#### tyguy

##### Guest
Thank you very much for you help.<br /><br />I find it interesting that we cannot view a white dwarf at the point to which it is no longer luminous. We were discussing this in class and the teacher asked why we have never seen a white dwarf that far along in its life. <br /><br />Also, got to see a comet and mars through a harvard telescope....very cool. It was the most powerful telescope in the world at 1 point.

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##### Guest
Hi Again, Ty! And delayed welcome to SDC!<br /><br />Have you seen my photography of Comet Holmes?<br />http://www.jlrdesigns.com/astrophotography/holmes-11-06-07.jpg<br /><br />It's amazing what you can do in your back yard. <div class="Discussion_UserSignature"> <p>.</p><p><font size="3">bipartisan</font>  (<span style="color:blue" class="pointer"><span class="pron"><font face="Lucida Sans Unicode" size="2">bī-pär'tĭ-zən, -sən</font></span></span>) [Adj.]  Maintaining the ability to blame republications when your stimulus plan proves to be a devastating failure.</p><p><strong><font color="#ff0000"><font color="#ff0000">IMPE</font><font color="#c0c0c0">ACH</font> <font color="#0000ff"><font color="#c0c0c0">O</font>BAMA</font>!</font></strong></p> </div>

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#### tyguy

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Wow, very clear...nice picture.<br /><br />It is very cool to be able to see something like that through a telescope, that was my first time using a high powered one.<br /><br />Did you take any pics of mars?

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#### 3488

##### Guest
hi tyguy,<br /><br />The universe is not yet old enough for Black Dwarfs (NOT to be confused with <br />Black Holes, totally different).<br /><br />There can be no white dwarf old enough as yet to have cooled to a Black Dwarf.<br /><br />In the far future however, there will be loads (our Sun included).<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

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#### wick07

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<font color="yellow">In the far future however, there will be loads (our Sun included). </font><br /><br />Which leads to an almost mind boggling thought about how young our universe really is (universally speaking of course). The youngest stars we see are only second generation. A civilization like ours in another 30 billion years will have a completely different universe to look at, with many new fascinating objects that right now we can only conceptualize.<br /> <div class="Discussion_UserSignature"> <p><font color="#3366ff"><strong>_______________________________<em> </em></strong></font></p><p><font color="#0000ff"><em>"</em>If you are surrounded by those who constatly agree with you, then you're in an intellectual vacuum.  If you feel like trying to make a difference, you have to BE different.  How can you do that without interacting with those who are different from yourself?"</font></p><p><font color="#0000ff">-  a_lost_packet_</font></p> </div>

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#### nexium

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That most of the stars are 2nd generation is more definition than fact. Rigel type stars could have done 3000 generations by now, and the oldest class m stars are still first generation. The oldest class g stars like our sun are 2nd generation or more. Neil

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#### tyguy

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what restricts the mass range of white dwarfs?

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#### nexium

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Are there yet any yellow or orange dwarfs = compact stars, which have cooled for 13 billion years, or are they still white hot?

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