The most important star in the Nautical Almanac is unnumbered. It is our own Sun.
Although Celestial Navigation is becoming a lost skill with the advent
of GPS, navigators are well advised to learn this Dark Art in the event
that the batteries go dead or the GPS unit goes on the fritz. Celestial
Nav can, and has, saved lives. And though it seems a little
impenetrable, all a navigator needs to know to take ("reduce") a sun
sight are the height of the Sun above the horizon (for which you use a
sextant), the precise time of your sight (for which you use an accurate
timepiece), the Greenwich Hour Angle (GHA) of the Sun (for which you use
the Nautical Almanac) and the Declination of the Sun (for which you use
a Sight Reduction Table). A few mathematical calculations later, and
you will know where in the world (literally) you are.
In
Celestial Nav the Sun is the most frequently referenced object for very
good reasons. It's big and it's bright and generally speaking the rest
of the stars are invisible all day long. There are 58 important stars
listed in the Nautical Almanac, and 115 more "Tabulated" stars (in the
event you need them), but literally none outshine the Sun (from where we
are). Our Sun is the ultimate Zero Magnitude star --- actually, for
what it's worth the Sun's Magnitude is listed at -27. As if we need to
know it's the brightest thing we see.
Without the Sun, we literally wouldn't be here. It is the Sun's energy that powers the Earth's own energy, and provides us with our very lives. The ancients knew that, and so they worshiped the Sun as a god. So, having said that, let's take a scientific look at our Sun:
The Sun has a proper name: It is Sol (pronounced "Soul"), and it's Latin. The most common use of the name Sol occurs in the word "Solar," that is, "Of the Sun," as in "Solar System." A more antique word would be "Solarian" which means the same thing. In the original Latin "Solarian" would translate to "Solaris," which doesn't fit well into common English sentence usage, and has become something of a book and movie title, and is the professional name of an astrologer I know.
Another word that you might come across is "solarium" for a sunroom.
Scientists are not always seemingly respectful of the sun. They often
describe Sol as an "ordinary" star, an "average" star, and a "very
typical" star. They've classed it as a "Yellow Dwarf." All these
descriptions may lead you to think that Sol goes home at dusk, puts his
feet up, and reads the paper before turning in for the night. But this
"very typical" star is unique in one respect: It's the only star in the
universe (thus so far as we know) that has a living planet orbiting it.
Although it is classed as a yellow star because it radiates much of its energy in the yellow (or more precisely, yellow-green) wavelength band, it emits radiation in all bands (as most stars do), including the ultraviolet and infrared. This "invisible" light can be seen by other animals, causes reactions in plants, and causes sunburn. It is because we are so close, and because we literally are the children of the sun, that our eyes have evolved to see its light as white.
And lest Sol seem a little boring nonetheless, consider that this "dwarf" star has a mass 330,000 times that of the Earth. It would take 110 Earths to circle the Sun's equator, and a million Earths could fit snugly inside the Sun. From where we sit, the Sun is 13 billion times brighter than Sirius, the next-brightest star we see. Sol is eight light minutes from Earth, about 93 million miles away.
The Sun contains 99.86% of all the mass in the Solar System, with Jupiter, the largest planet, taking up a far distant second 0.0009546% of the Sun's mass (and yet Jupiter takes up 75% of the remaining mass of the Solar System). The Sun's radius is 432,288 miles.
The Sun is a vast ball of plasma, busily converting hydrogen to helium through a process of nuclear fusion. The temperature of the surface of the Sun is just under 10,000 degrees Fahrenheit, but the temperature of the core is 28,799,541 degrees F. At that temperature hydrogen (the lightest element) loses its single electron, and those "lost" electrons get picked up by other atoms, forming two-electron helium atoms. This is a violent process, and the energy released in this forcible fusion reaction is responsible for the light and heat emitted by the Sun. 600 million tons of hydrogen is converted into 430 million tons of helium every second in the Sun's core. The Sun has been fusing hydrogen into helium at this rate for 4.5 billion years and will continue to do so for another 4.5 to 6 billion years.
When we consider that the Sun is nowhere near the largest, brightest or most dynamic star we have met in our armchair travels, the immeasurable energy of the universe becomes just a little more evident. There are things out there --- pulsars and quasars and neutron stars --- that make the Sun look like an ember. Scientists consider the "metabolism" of the Sun to be equivalent to that of a sleeping iguana; but it is this very lethargy that gives the Sun its long lifespan and has allowed life to evolve on Earth.
Considering that the Sun is more dynamic than 85% of all stars, the
possibilities for the long-term evolution of life on planets circling
other suns increase to incredible levels.
The story of the Sun
began long before the Sun was born. Five to six billion years ago, a
supergiant star whose name we will never know, perhaps a blue star like
Rigel or a red star like Betelgeuse, exploded in a dramatic supernova
somewhere in our Milky Way galaxy. More than likely, this dying
supergiant was a member of a multistar system containing, maybe, a green
or yellow dwarf with a planetary system, and a cool red dwarf. The
explosion of the primary consumed them all, spraying stardust for light
years in all directions. A cloud of wreckage called a nebula, was the
result.
Some of those elemental molecules are still moving quickly through space propelled by the force of the original blast, and they will travel literally forever, reaching far distant galaxies in trillions of years. They are much like dust particles in Earth's atmosphere, the lightest of which can spend eternity suspended in midair.
But unlike dust particles in an atmosphere, dust and gas particles in space tend to agglutinate, or clump together, in those regions of space where the nebula is more dense, drawn by gravity. The cloud breaks into a series of whirlpools.
A single molecule becomes two, and eventually a dust particle. As it grows bigger its gravitational pull increases, causing it to grow even bigger. The particle becomes a speck, a speck becomes a grain, a grain becomes a pebble, a pebble becomes a stone . . . and as it grows, the pressure within increases, the heat increases, and it forms a sphere. If it grows very large, eventually the sphere gets so hot that it spontaneously combusts.
And so our Sun was born, and so were the planets around it, all from the whirlpooling, swirling stuff left over from the long-ago death of the blue (or red) supergiant and its friends. We know that there must have been planets in that vanished star system because there are so many heavy metals --- like gold and silver --- on Earth and in the Sun, and more than likely on the other seven planets circling the Sun.
The Sun is in the heart of its Main Sequence. Too small to explode, when it grows old it will first turn into a red giant, expanding and consuming Mercury and Venus (and baking the Earth). Hopefully, on that day, our species will have long been colonizing other solar systems. When it uses up the very last of its fuel it will collapse down into an ultradense White Dwarf the size of the Earth or even Mars, and will phosphoresce dimly for eternity. But in that violent and unstable red giant phase it will throw off stellar material that will eventually form the substance of other stars, and the cycle will begin again.
We are here because far away and long ago a star died. Every molecule in your body, in everything, is star-stuff --- and the stuff in your fingertip is from a different star than the stuff in your fingernail. Talk about miracles.
The story of the Sun is a story of rebirth and reincarnation. Not for nothing is our star named Sol.
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| A star gone supernova some 5 - 6 billion years ago was the end of the beginning for our Sun. |
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| A nebula, drifting through space. It is the death shroud of an ancient star or stars, and the nursery of newly-forming stars. Made of dust and gas and fragments (literally stardust) this nebula is backlit by other stars behind it. Everything in the stars comes from nebulas --- including us. |
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| Gravity pulled the dust of the Sun's ancestor into a whirlpool. Pressure at the center caused heat which caused the Sun to ignite. The newborn Sun lit up the dustcloud. The heat and energy of the new sun increased the disc's rate of rotation, causing planets to form.The stuff in the surrounding disk became the planets and everything on them, and us. |
Without the Sun, we literally wouldn't be here. It is the Sun's energy that powers the Earth's own energy, and provides us with our very lives. The ancients knew that, and so they worshiped the Sun as a god. So, having said that, let's take a scientific look at our Sun:
The Sun has a proper name: It is Sol (pronounced "Soul"), and it's Latin. The most common use of the name Sol occurs in the word "Solar," that is, "Of the Sun," as in "Solar System." A more antique word would be "Solarian" which means the same thing. In the original Latin "Solarian" would translate to "Solaris," which doesn't fit well into common English sentence usage, and has become something of a book and movie title, and is the professional name of an astrologer I know.
Another word that you might come across is "solarium" for a sunroom.
 |
| The Sun (Sol) is a yellow dwarf, the second most common and second most long-lived of all stars. Only dim red dwarfs are more numerous and can live longer --- trillions, and not just billions, of years. |
 |
| The Sun is a violent thermonuclear reactor. It has an intense magnetic field, blows off the substance of its outer layer in a solar wind, and occasionally flares. All this activity can disrupt activities and even the life of species on the Earth. |
Although it is classed as a yellow star because it radiates much of its energy in the yellow (or more precisely, yellow-green) wavelength band, it emits radiation in all bands (as most stars do), including the ultraviolet and infrared. This "invisible" light can be seen by other animals, causes reactions in plants, and causes sunburn. It is because we are so close, and because we literally are the children of the sun, that our eyes have evolved to see its light as white.
 |
| Our friendly Sun. Giver of light and warmth, it is also the giver of deadly radiation and uncontrolled heat and iciness. In reality, the Sun and the Earth are partners in a very delicate dance in which the Earth has always been just one step ahead. Planets that fell behind have been blasted into a naked iron ball (Mercury), overwhelmed by heat and light (Venus) and dessicated (Mars). It's possible that life might have existed on any of them. But not anymore. |
And lest Sol seem a little boring nonetheless, consider that this "dwarf" star has a mass 330,000 times that of the Earth. It would take 110 Earths to circle the Sun's equator, and a million Earths could fit snugly inside the Sun. From where we sit, the Sun is 13 billion times brighter than Sirius, the next-brightest star we see. Sol is eight light minutes from Earth, about 93 million miles away.
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| The Sun is the master of the Solar System. Huge Jupiter is dwarfed by the Sun, and the terrestrial planets --- Mercury, Venus, Earth, and Mars --- are barely visible in this scaled comparison. |
The Sun contains 99.86% of all the mass in the Solar System, with Jupiter, the largest planet, taking up a far distant second 0.0009546% of the Sun's mass (and yet Jupiter takes up 75% of the remaining mass of the Solar System). The Sun's radius is 432,288 miles.
The Sun is a vast ball of plasma, busily converting hydrogen to helium through a process of nuclear fusion. The temperature of the surface of the Sun is just under 10,000 degrees Fahrenheit, but the temperature of the core is 28,799,541 degrees F. At that temperature hydrogen (the lightest element) loses its single electron, and those "lost" electrons get picked up by other atoms, forming two-electron helium atoms. This is a violent process, and the energy released in this forcible fusion reaction is responsible for the light and heat emitted by the Sun. 600 million tons of hydrogen is converted into 430 million tons of helium every second in the Sun's core. The Sun has been fusing hydrogen into helium at this rate for 4.5 billion years and will continue to do so for another 4.5 to 6 billion years.
 |
| The Sun is barely visible compared to other well-known stars in this scaled comparison model |
When we consider that the Sun is nowhere near the largest, brightest or most dynamic star we have met in our armchair travels, the immeasurable energy of the universe becomes just a little more evident. There are things out there --- pulsars and quasars and neutron stars --- that make the Sun look like an ember. Scientists consider the "metabolism" of the Sun to be equivalent to that of a sleeping iguana; but it is this very lethargy that gives the Sun its long lifespan and has allowed life to evolve on Earth.
 |
| In this model Rigel and Antares are compared to Betelgeuse, and Betelgeuse is compared with the largest stars yet known. When VY Canis Majoris was found, astronomers argued that physics precluded stars from being any larger; in 2017, UY Scuti made them wrong. Sol is a glowing ember in the heavens and we live on a mote of dust. |
 |
| As stars go, the Sun is not very large, but there are more "yellow dwarfs" like the Sun than any other stars except red and brown dwarfs. Red and brown dwarfs exist in the trillions throughout the universe. Even more stable and long-lived than Sol, red and brown dwarfs are quite capable of hosting innumerable planets on which life has had time to develop. Jupiter may be a brown dwarf that never ignited. |
Some of those elemental molecules are still moving quickly through space propelled by the force of the original blast, and they will travel literally forever, reaching far distant galaxies in trillions of years. They are much like dust particles in Earth's atmosphere, the lightest of which can spend eternity suspended in midair.
But unlike dust particles in an atmosphere, dust and gas particles in space tend to agglutinate, or clump together, in those regions of space where the nebula is more dense, drawn by gravity. The cloud breaks into a series of whirlpools.
A single molecule becomes two, and eventually a dust particle. As it grows bigger its gravitational pull increases, causing it to grow even bigger. The particle becomes a speck, a speck becomes a grain, a grain becomes a pebble, a pebble becomes a stone . . . and as it grows, the pressure within increases, the heat increases, and it forms a sphere. If it grows very large, eventually the sphere gets so hot that it spontaneously combusts.
And so our Sun was born, and so were the planets around it, all from the whirlpooling, swirling stuff left over from the long-ago death of the blue (or red) supergiant and its friends. We know that there must have been planets in that vanished star system because there are so many heavy metals --- like gold and silver --- on Earth and in the Sun, and more than likely on the other seven planets circling the Sun.
The Sun is in the heart of its Main Sequence. Too small to explode, when it grows old it will first turn into a red giant, expanding and consuming Mercury and Venus (and baking the Earth). Hopefully, on that day, our species will have long been colonizing other solar systems. When it uses up the very last of its fuel it will collapse down into an ultradense White Dwarf the size of the Earth or even Mars, and will phosphoresce dimly for eternity. But in that violent and unstable red giant phase it will throw off stellar material that will eventually form the substance of other stars, and the cycle will begin again.
We are here because far away and long ago a star died. Every molecule in your body, in everything, is star-stuff --- and the stuff in your fingertip is from a different star than the stuff in your fingernail. Talk about miracles.
The story of the Sun is a story of rebirth and reincarnation. Not for nothing is our star named Sol.
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