Primordial Light: THE SUN
Exploring our own back yard.
Our Sun is a very ordinary star in mass and temperature. The Sun and its planets (and regardless of what you may have read or heard, our Solar System has nine planets, including Pluto) formed about four and a half billion years ago from a cloud of (mostly hydrogen) gas and fine dust that was perturbed somehow—perhaps by the gravity of a passing star, perhaps by pressure waves from the explosion of a massive star in the neighborhood. Whatever the cause, the gas and dust in the cloud began to clump together. Once that process began, the equilibrium of the cloud was upset and the denser areas attracted more and more gas as their increased mass exerted a greater gravitational attraction on the cloud. When the cloud reached a certain density it had to—according to the theory of gravity—take the spherical shape that virtually all celestial bodies above a certain mass have. As such a sphere—it is now the Proto Sun—gains more and more mass the gravitational pressure on the hydrogen at its center causes the core to become very hot. Finally, when the temperature is above about 10 million Kelvins, the hydrogen atoms at the core are moving with such energy that when they collide they fuse together to make helium. A star is born. The fusion process produces more energy than is required to fuse hydrogen into helium, and the excess energy travels to the surface of the star and into space as stellar radiation. Amazingly, the complex process of convection that carries radiation from the Sun’s core to its surface requires millions of years to transport the radiation from the core to the surface. Then it takes another eight minutes to reach the Earth. Now it is the sunshine that makes life on Earth possible. (Though it is also the ultraviolet radiation that may cause skin cancer and it is the powerful radiation that may damage earth satelittes, disrupt radio and television signals, and temporarily shut down electric power distribution systems on Earth.) The larger a star is, the faster it burns its fuel; some massive stars live only some few millions of years before they exhaust the supply of fuel they require for fusion and with no radiation pressure to maintain their size, they collapse on themselves in a Supernova explosion. Our Sun is a relatively small star, and it burns its fuel at a much more economical rate. The Sun has now burned about half of its fuel, and it is expected to last for another five billion years or so (so you can proceed with your plans for the weekend). The Sun is the subject of intense scientific exploration, especially from spacecraft. NASA maintains many web pages that contain good science presented in such a way that laymen like you and me can understand it. Here is a starting point for basic facts about the Sun.
A Very Large Sunspot Group on January 12, 2005
Sunspots are areas where sub-surface magnetic disturbances have caused a slight cooling, and therefore, a darkening, of the photosphere, which is the visible surface of the sun. Since the sun is a ball of gas, it doesn't have an absolutely defined solid surface like the Earth and the other rocky planets. Galileo is believed to be the first to discover sunspots, in 1612. His drawings of sunspots may be seen here in animated form. Galileo was an astute observer, so it is no coincidence that his sunspot drawings are so similar to my photographs. Galileo really upset the applecart because the doctrine of the Church of Rome was that all heavenly bodies were perfect and without blemishes. Galileo’s best (or worst from the Church’s point of view) attack on the applecart was his revolutionary discovery that there are moons in orbit around Jupiter. That meant that the Earth is not the center of the Universe as Church doctrine insisted that it was. Galileo’sreward for this monumental discovery was years of house arrest and finally being forced to repudiate what he knew to be true. But the truth will be supressed, and in 1992, 350 years after Galileo’s death, the Church of Rome apologized for condemning Galileo and his scientific research
Nine days later, on January 21, 2005, the Sunspot Group shown in
the top image had rotated nearly out of sight. It’s that dark spot on
the extreme right limb (edge) of the Sun.
The Sun rotates on its axis as does the Earth, but with an important difference. Since, as noted above, the Sun is not a solid body, different latitudes can rotate at different rates. The solar equator rotates once every 26 days. At 60° north and south of the equator the rotation requires about 31 days, and at the poles the Sun rotates once every 36 days. If the Earth rotated in this manner and the period of rotation (the length of the day) was 24 hours at the Equator, the day would be about 29 hours long in Helsinki, Finland, and 36 hours long at the North and South Poles. And you think you have problems with time zones now!
Two Sunspot Groups on October 30, 2003
Sunspots are areas where sub-surface magnetic disturbances have caused a slight cooling, and therefore a darkening, of the photosphere, which is the visible surface of the sun. Since the sun is a ball of gas, it doesn't have a sharply defined solid surface like the Earth and the other rocky planets, but the photosphere suffices for our purposes.
This is the larger of the two sunspot groups shown above. This group is many times the size of the Earth.
Below: Three Stages of the Partial Solar Eclipse of April 8, 2005
6:22 P.M. EST
6:30 P.M. EST
6:37 P.M. EST
I was not ready for this one. The sky had been obscured by dense clouds
all day, and it was still obscured when the eclipse began at about 4:59 P.M. EST. I was so certain that the sky would not clear that I didn’t have a telescope or camera ready. Suddenly, at about 6:15 P.M., the clouds parted. Lucky for me that I have the very portable Questar telescope shown below; I was able to get it from it’s storage box and have it set up and ready to photograph the last few minutes of the eclipse in about five minutes. (Actually, luck has nothing to do with my having the Questar. When I bought the Questar in 1982 I was a world traveler and I wanted a very portable, high-quality telescope that would fit under an airline seat. The Questar was, and is, the perfect instrument for that purpose.)
A Solar Eclipse Montage from July 11, 1991
A Solar Eclipse Montage from Christmas Day, 2000
(Or: Standing Outside For Hours in Freezing Weather on Christmas Day
While Everyone Else Sits by the Fireplace)
The images in both montages were made with the Questar Duplex and
an Olympus OM4 35mm film camera.
Photographing the Christmas Eclipse
It was bitterly cold—about 15°F with a wind-chill factor of 0°.
The Questar Duplex Equipped with a Safe Solar Filter
Heed this warning! Looking at the Sun through a camera, binoculars, a telescope, or with your naked eye can cause immediate, permanent blindness. Never look at the Sun unless you have a “safe solar filter.” A “safe solar filter” is one that a reputable manufacturer has stated is suitable for visual observation of the Sun. If you are at all uncertain about your filter, don’t use it. Sunglasses, polarizing filters, neutral-density filters, and smoked glasses are not safe solar filters. Don’t use them.