Basic Facts About the Sun

Most of the facts about the sun known to us today are fairly recent, coming after the invention of the telescope, photography, spectroscopy, and the launching of satellites.

Invention of the Telescope

It appears that the earliest working models of the telescope seem to have been invented by Hans Lippershy in 1608. Just a year later, Galileo was using these devices to do incredible research, helping him discover that the sun was rotating – and fully convincing him that the Heavens were governed by predictible movement. This lead to his later assertion, that the Earth moves around the sun - one of the most basic facts about the sun.

19th Century

However it wasn't until the invention of photography and spectroscopy in the 19th century, combined with proper record keeping, that proper solar research could begin, and we could finally learn some more useful facts about the sun.

On September 1st, 1859, a British astronomer observed and recorded for the first time a major coronal mass ejection / solar flare, now known as the “Carrington Event”. As the radiation from the storm hit the Earth it knocked out telegraphs - the world’s first electromagnetic-based communications system. Since then a number of solar storms have demonstrated the fragility of our electronic communications and power systems.

Click on the following links to learn more about Coronal Mass Ejections or about why NASA and other scientists are concerned that an even worse scenario than what happened in 1859 could occur in 2012.

20st Century

In 1989 a similar solar storm destroyed a transformer and blacked out most of Quebec. Since then, our dependence on delicate digital systems has increased and few of them are hardened against sudden spikes in solar radiation. Even moderate solar activity can have an effect on our lives such as degrading the accuracy of the signals from the GPS satellites or the power-output from communications satellites.

In 1998 a solar storm knocked out a communications satellite and rendered millions of pagers all over America useless.

Even moderate solar activity can have an effect on our lives such as degrading the accuracy of the signals from the GPS satellites or the power-output from communications satellites.

21st Century

Increasing our understanding of the sun and the ability to predict solar weather is a key goal of the Solar Dynamics Observatory [SDO] NASA launched in February 2010 to study the variability of the sun.

SDO is equipped with cameras that will be able to take IMAX-quality images of solar explosions. It also has sensors that can look deep inside the sun to reveal the inner workings of the sun’s magnetic dynamo, the root of all solar activity. SDO’s Helioseismic and magnetic imager will allow “Scientists to make ultrasound images of the Sun and to study active regions in a way similar to watching sand shift in a desert dune.”

The following is one of the first photos from SDO showing a huge loop of material shooting up from the sun's surface in March. Known as a prominence eruption, the loop was born from a relatively cold cloud of plasma, or charged gas, tenuously tethered to the sun's surface by magnetic forces. Such clouds can erupt dramatically when they break free of the sun's unstable hold.

The most important feature of NASA’s SDO mission is the Solar Sentinel program, which will send a series of satellites that will give us a permanent three-dimensional near-real-time vision of the Sun. These spacecraft will actually lead the way towards a move from gathering data for science and gathering data for what might be termed - Solar System Wide Weather forecasting.

Meanwhile, the following is a summary of some of the facts about the sun we have learned so far:

Made from Recycled Material

Our sun is one of around 300 billion stars in the Milky Way Galaxy, which was formed around 9 billion years ago.

If you want to know what recycling is good for you … be thankful for the sun. It formed from an interstellar cloud 4.6 billion years ago, out of material that had been at least partially recycled from earlier generations of stars in our Galaxy. It accounts for 99.8% of the mass of our solar system.

Almost all of the elements in the Sun beyond element number 2 (helium) were made in these earlier generations of stars, including small amounts of sulfur, magnesium, carbon, neon, iron, oxygen, nickel, chromium and calcium.

The Sun's Orbit

The Sun orbits the center of the Milky Way at a distance of approximately 24 to 26 thousand light years from the galactic center, completing one clockwise orbit every 225 to 250 million years. The Sun has circled the Milky Way galaxy about 20 times only since it's formation.

The Sun is pretty bright

Our own Sun is a relatively bright star. Of the stars within 17 light-years of the Earth and ranked them by brightness, our sun would be number 4.

The luminosity of the Sun is equivalent to the luminosity of 4 trillion, trillion 100 watt light bulbs.

Color of the Sun

From space, the Sun looks white.

Why then does it appear reddish around sunrise and sunset … and yellow during the day?

Basically the reason has to do with the absorption and scattering of the electromagnetic energy by the molecules of gas that make up the atmosphere (ozone, nitrogen, oxygen, argon, water vapor, etc.). Gas molecules are smaller than the wavelength of visible light. When light hits a gas molecule, some of it may get absorbed. After awhile, the molecule radiates the light in a different direction. The color radiated is the same color absorbed. All of the colors can be absorbed, but the higher frequencies (blues) are absorbed more often than the lower frequencies (reds). This process is called Rayleigh scattering. (named after Lord John Rayleigh, an English physicist, who first described it in the 1870's.)

As the sun begins to set, the light must travel farther through the atmosphere before it gets to you. More of the light is reflected and scattered. As less reaches you directly more of the light is absorbed / scattered. The sun loses its brightness and color of the sun itself appears to change, first to orange and then to red. This is because even more of the short wavelength blues and greens are now scattered. Only the longer wavelengths (reds and oranges) are left in the direct beam that reaches your eyes.

The sky around the setting sun may take on many colors. The most spectacular shows occur when the air contains many small particles of dust or water. These particles reflect light in all directions. Then, as some of the light heads towards you, different amounts of the shorter wavelength colors are scattered out. You see the longer wavelengths, and the sky appears red, pink or orange.

Solar Warming

It feels like the Sun has been around forever, unchanging, but that's not true. The Sun is actually slowly heating up. It's becoming 10% more luminous every billion years.

In fact, within just a billion years, the heat from the Sun will be so intense that liquid water won't exist on the surface of the Earth. Life on Earth as we know it will be gone forever.

It'll take another 7 billion years for the Sun to reach its red giant phase before it actually expands to the point that it engulfs the Earth and destroys the entire planet. In other words, the expected life of the sun is around 11 billion years.

Rotation of the Sun

All matter in the Sun is in the form of gas and plasma because of its high temperatures.

One of the most potentially important facts about the sun deals with the rotations of these gases and plasma. Because of the effects of gravity, the Sun rotates faster at its equator (about 25 days) than it does at higher latitudes (about 35 days near its poles).

The differential rotation speeds causes its magnetic field lines to become twisted together over time, causing magnetic field loops to erupt from the Sun's surface and trigger the formation of the Sun's dramatic sunspots, coronal mass ejections (CMEs) and geomagnetic storms.

Every 11 years solar cycle of magnetic activity. Basically, this means that the sun reverse's it magnetic field about every 11 years, i.e., its north magnetic pole becomes a south pole, and vice versa.

Click here to read more about solar flares, geomagnetic storms and the problems they can cause.

22 Year Magnetic Cycle

The Sun has a strong and complex magnetic field, which is caused in part because the varying speeds that the plasma spins as the sun rotates on its axis. The sun's magnetic field plays an important role in most aspects of the active Sun (sunspots, prominences, flares, the solar wind, and the nature of the corona), so the 22 year magnetic cycle is central to the periodicity of the active Sun.

On average the Sun's polarity reverses every 11 years, i.e., the north magnetic pole becomes the south pole, and vice versa. The Solar magnetic field has a 22 year cycle, exactly twice that of the sunspot cycle, because the polarity of the field returns to its original value every two sunspot cycles.

Sunspot Cycle 24

After viewing the sun with his new telescope, Galileo made the first European observations of sunspots in 1610. Solar sunspot cycles have been tracked continuously since March 1755 in the West. We are currently in cycle 24, which started December 2001. On average, each cycle lasts 11.1 years.

Sunspots are well-defined surface areas that appear darker than their surroundings because of lower temperatures. The largest sunspots can be tens of thousands of kilometers across. As the temperatures cool, the sun contracts increasing the pressure below the sunspot, and helping to keep the nuclear fusion reactions going.

During a 75-year period beginning in 1645, astronomers detected almost no sunspot activity on the sun. Called the “Maunder Minimum,” this event coincided with the coldest part of the Little Ice Age, a 350-year cold spell that gripped much of Europe and North America.

Note 1: F. Richard Stephenson and Kevin K.C. Yau found evidence or more than 200 records of sunspot activity in the Orient going back to 200 BC.

Note 2: A recent theory claims that there are magnetic instabilities in the core of the Sun that cause fluctuations with periods of either 41,000 or 100,000 years. These could provide a better explanation of the ice ages.

Solar Wind

Solar winds are essentially bands of plasma, extremely hot, charged particles, or electrons that escape from the Sun's surface. They carry around 6.7 billion tons of matter away from the sun per hour This is equivalent to losing a mass equal to the Earth every 150 million years. However, given the size of the sun even these large number only represent about 0.01% of the Sun's total mass has been lost through the solar wind.

The solar wind is not uniform. Although it is always directed away from the Sun, it changes speed and carries with it magnetic clouds, interacting regions where high speed wind (800 km/s) catches up with slow speed wind (300 km/s). These high and low speed streams interact with each other and alternately pass by the Earth as the Sun rotates.

These wind speed variations buffet the Earth's magnetic field and can produce storms in the Earth's magnetosphere and can cause numerous problems.

The wind is considered responsible for the tails of comets to always face away from the sun.

For more information about possible risks and problems caused by solar winds, see a more detailed explanation regarding solar flares, and geomagnetic storms.

Energy Stability

The energy output of the sun has been relatively stable over the past 50,000 years which has allowed humanity to flourish. Scientists predict that even though there are likely to be numerous fluctuations (e.g., solar flares, coronal mass ejections, etc.) the energy output should remain fairly constant for another 50,000 years, which gives a fair amount of time to get our collective act together.

Miscellaneous Facts About the Sun

The Greek philosopher Aristarchus of Samos (310 to 230 BC) is credited as being the first person to claim that the Earth orbited the sun. The crater Aristarchus on the Moon is named in his honor.

During photosynthesis the sun's energy is used to split water molecules, starting a flow of electrons. The energy from this flow of electrons is harnessed and used to make the bonds in organic molecules.

The source of the sun's energy has challenged scientists for centuries. In the 19th century it was assumed that the sun's energy resulted from its gravitational collapse.

Some solar scientists believe that global warming is caused primarily by solar activity and that while man-made pollution causes a host of other problems and does contribute to global warming it is not the major cause, however at the present time this is more of a theory than widely accepted fact.

Solar eclipses are visible in a narrow path, a maximum of 269 km wide. A maximum of 5 Solar eclipses only can occur in an year. No Total solar eclipse can last longer than 7 minutes and 58 seconds because of the speed that the earth and moon rotate. At any place on the Earth, a total solar eclipse will occur on an average of once every 360 years.

Approximately one million Earths can fit inside the Sun.

Around 50 trillion neutrinos from the Sun will pass through your body every second while you read this sentence. Neutrinos are a by-product of the fusion of hydrogen into helium – and are basically mass-less and as the name implies, charge neutral.

The Near-Term Future

Mainstream scientific concern about the consequences of peak solar activity that could occur in 2012 has grown since a recent National Research Council report funded by NASA and issued by the National Academy of Sciences, entitled “Severe Space Weather Events: Understanding Economic and Societal Impact” was issued.

This report details the potential devastation that a severe solar storm could have on the current planetary energy grid and because of the inter-linkages of a cybernetic society, on our entire human civilization. The report has stimulated a number of interesting discussions regarding ways that utility operators, the military, corporations and individuals can protect their vulnerable electronics, and provide another reason to consider the potential benefits of producing your own electricity and reducing your dependency on the electrical grid.

Stay tuned as we intend to update an expand our section on facts about the sun, including adding more links to related articles you might find beneficial.

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