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Site Highlights: Scenic drive Virtually no visitors No entry fee Off the beaten track Open to the public See scientists at work Instruments up close Live pictures of sun Educational View White Sands View Tularosa Basin
The National Solar Observatory / Sacramento Peak is located in southern New Mexico at the height of 9200 feet (2800 meters) in the Sacramento Mountains. This site, chosen in 1947, overlooks While Sands Missile Range in the Tularosa Basin. The dry air of the southwest, isolation from any major source of air pollution, and plenty of sunshine make this an excellent site for observing the Sun.
The staff presently consists of research scientists, engineers, technicians, and support staff. In addition, scientists from other observatories and universities around the world come to the National Solar Observatory.
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The Evans Solar Facility is housed in the Big Dome, which was completed in 1952. There are two main telescopes in this facility: a 16" coronagraph and a 12" coelostat. Each of these telescopes can be used to feed one of several instruments. This means that two observing programs can be run simultaneously.
The Evans Solar Facility is used most often to look at the corona: the faint outermost layer of the Sun (see Site Gallery). Because the visible disk of the Sun is so bright, one cannot usually see the corona. The main telescope in the Big Dome is a coronagraph. It has a disk inside that blocks off the bright disk of the Sun simulating an eclipse, so the scientists can study the faint corona.
Most of the time, the scientists that use this facility investigate solar flares, a magnetic field high above the visible surface of the Sun, and filaments (which are called prominences when they are seen sticking beyond the bright disk of the Sun).
The Evans Solar Facility has no fixed observing program. Scientists are able to point the telescopes wherever they want on the Sun and to use whatever filters or other special equipment they need to complete their research.
This structure contains an entrance window and two mirrors that guide the light of the Sun down the tower in an evacuated tube from which the air has been removed. The tower is an impressive 136 feet (41m) tall, but the building has 228 more feet (72 m) below ground, so most of the building is in fact not visible. After the light has hit the two mirrors at the top, it goes straight, down the tube at the center of the telescope until it hits the primary mirror, 188 ft (57 m) below the ground. The primary mirror is 64 inches (163 cm) in diameter. It focuses the light and sends it back up to ground level, where it exits the vacuum tube and can be guided into the scientists' experiments on the optical benches.
The rotating part of the telescope weighs more than 200 tons. It is suspended at the top from a ring- shaped container holding 10 tons of mercury. The central tube is hanging: it does not sit on anything. Because mercury has very low friction, it is fairly easy to rotate the 200 tons of tube and instruments. (see Site Gallery)
The kinds of things on the Sun that scientists investigate using this telescope include granulation, sunspots, faculae, weak magnetic field, filaments, and solar flares.
Sunspots are associated with strong magnetic field on the Sun. As the magnetic field twists and turns, it builds up a tremendous amount of energy. This energy can be released explosively in what is called a flare. Eruptive phenomena such as flares can eject particles which can reach the Earth. This can result in the Aurora Borealis, or Northern Lights, seen frequently at higher latitudes and it can also lead to the disruption of some radio communications.
Understanding of the Sun can also be gained by looking at the area where there are no sunspots. This spot-free area is known as the "quiet" sun. The fine, mottled background of the quiet sun is called granulation. Each bright granule represents hot gas rising from below. As the gas cools and falls, it becomes darker, creating the dark lanes between the brighter cells of rising gas. The rising, spreading motion of hot gas causes the magnetic field to collect in the dark lanes.
A wealth of information is obtained by spectral analysis, and much of the work done at National Solar Observatory/ Sacramento Peak is based on spectroscopy. By examining the solar spectrum, it is possible to determine the sun's chemical composition, its temperature, the motions of its surface gases, and the strength of the magnetic field.
The Hilltop Dome was completed in 1963. As with the Evans Solar Facility, the roof of the building (with the doors in it) can rotate around to allow the telescope to see the Sun anywhere in the sky. This telescope is used for taking patrol images of the whole Sun. These images are used to discover when something interesting is happening on the Sun.
The Hilltop Dome contains several telescopes that have one task only: to look at the whole Sun all the time that the Sun is visible. Pictures are regularly taken through these telescopes; most of the time at the rate of one picture per minute, but more if it is likely that something interesting will happen. The Hilltop Dome telescope takes two kinds of pictures: ones that show what the Sun looks like to the human eye, and others at a particular color (with a wavelength of 6563 Angstroms) that is affected by hydrogen atoms in the Sun. In such pictures, faculae, filaments, and solar flares stand out much better than in ordinary pictures.
The Hilltop Dome pictures form an archive of observations of the Sun. It allows scientists to see the largest possible number of interesting things on the Sun (such as solar flares), even if the other telescopes at the observatory are looking at other parts of the Sun. If a solar flare is seen, then we can go back to the archive and check if something happened earlier that could help us predict when the next one will come.
In 1950, the Grain Bin Dome was the first telescope dome built in Sunspot.The Observatory ordered the grain bin from a Sears catalog and modified it for use as a telescope dome. A 6-inch prominence telescope was mounted on a 10-foot spar inside for observing the limb (edge) of the Sun.
The modifications included a slit in the roof and the ability to rotate so that the telescope could track the Sun. From March 1951 through 1963 daily flare patrol images were taken from the Grain Bin. Additional or newer telescopes were installed in 1952,1955, and 1957. In 1963 the solar patrol duties of the Grain Bin were transferred to the then newly built Hilltop Dome.
The Grain Bin Dome seems not to have been used after 1963, until a night-time telescope was installed in 1995. Sunspot residents can now use that telescope to look at the night sky. Over the years that the Grain Bin Dome was not in use, the trees around the Dome have grown, limiting the amount of observable sky.
Faculae are places smaller than sunspots or pores where a magnetic field sticks through the surface of the Sun. The magnetic field in faculae is not as strong as that in sunspots. Faculae are hard to see in ordinary pictures of the Sun, but they appear bright in pictures taken with appropriate filters in front of the camera.
Solar flares flares are explosive eruptions of material from the Sun into space. Solar flares occur sometimes when strong magnetic field becomes very twisted. The energy stored in the twisted field is released, heats the material to temperatures of millions of degrees, and shoots part of it into space. Solar flares may have effects on Earth, the most important being that they may disrupt some short-wave radio communications. However, solar flares have no influence on the lives of most people.
Granulation is the irregular pattern of bright spots (granules) surrounded by dark lanes that covers most of the visible surface of the Sun. Granules have a diameter of about 600 miles (about the size of the state of Texas), a temperature of about 10,000 degrees F, and last for about 8 minutes. Granules are places where hot material comes to the surface of the Sun from below, like hot bubbles in boiling water. When the material has cooled off, it turns darker and goes down the lanes.
Our Solar Furnace:
For the past 4.5 billion years, the Sun has been bathing our Earth with life-sustaining heat and light. Yet, as the closest star to Earth, it is 145 million km distant (this distance is called an Astronomical Unit). You could fit 109 Earths across the Sun's 864,000 - mile face.
The core of the Sun is a solar furnace; its heat is an incredible 27 million degrees F (15 million degrees C). The surface temperature of the sun is about 10,000 degrees F (5,700 C). About three quarters of the weight of the Sun is hydrogen, almost one quarter is helium and less than 1% is made up of other elements. Sunlight generated in the core takes millions of years to reach the surface.
The corona (outer atmosphere)
The Sun's thin outer atmosphere is called the corona. Recent studies have revealed that there are openings in the corona where the density and temperature are unusually low. These "coronal holes" allow solar material to escape more easily. This material gives rise to high-speed solar wind streams which interact with the Earth's magnetic field and cause geomagnetic storms.
In the chromosphere, below the corona, fountain-like jets of gas, called spicules, rise thousands of miles high. Slender spicules of flaming gas reach heights of 6,000 miles or more. Loop prominences are formed when fiery material raining down from the corona is caught by arch shaped magnetic field lines.
The Photosphere (visible surface)
The photosphere is the visible surface of the sun. It is a layer of gas several hundred miles thick where huge, cooler sunspots are seen. These dark, splotchy sunspots appear where magnetic field lines burst through the surface.
Sunspots are places where a very strong magnetic field sticks through the surface of the Sun. Sunspots vary greatly in diameter, from about 1500 miles for the smallest ones (which are called pores) to 30,000 miles or more for the largest ones. The magnetic field in sunspots can be up to 5000 times stronger than the magnetic field of the Earth. Sunspots can last about a month or so (if they are big). Sunspots do not affect the weather or anything else on Earth.