Journey Through The Solar System, Episode 01 - Our Star, The Sun
Transcript
00:00There are billions of stars in this galaxy called the Milky Way.
00:21Our star, the Sun, provides Earth organisms the energy to live and thrive.
00:27The Milky Way and our Sun circle the many planets of our solar system.
00:31And many as they are, the planets of our solar system are only a fraction of the mass of our Sun.
00:39And our Sun is a relatively small star in the universal scale.
00:57Music
01:26I'm Larry Ross, Director of Space Programs at the NASA Lewis Research Center in Cleveland, Ohio.
01:31And I'm your host for a series of 13 programs about the solar system.
01:36During the series, Journey Through the Solar System,
01:39we'll closely examine our corner of the universe, beginning at the Sun
01:44and moving outward to Mercury, Venus, Earth, the Moon, Jupiter, Saturn, and beyond.
01:52Let's begin with the Sun.
01:54Inside, its temperature could be as high as 25 million degrees.
01:59Pressures are estimated at a trillion pounds per square inch.
02:04Not many years ago, man knew little about the Sun.
02:08Now, from a motion picture called Partnership in Space Mission Helios,
02:13we have a clip about the past.
02:16Man has been fascinated by the Sun since the beginning.
02:24In ancient Britain, the Druids built a mysterious monument to it.
02:29In Egypt, the Sun was worshipped as a deity, and its passage from day to night was sanctified.
02:36The Mayans offered sacrifices to the Sun.
02:40For the Aztecs, it measured time.
02:43Some artists reproduced it in colorful stones and gold.
02:48Others captured its mysterious quality on canvas.
02:53Children see it as a smiling face.
02:58It is the source of bounty,
03:04and, as in parts of Africa, an element of devastation.
03:15Early man brought the Sun down from the sky to within his reach.
03:19Modern man journeys upward to understand it.
03:22Still, it remains a mystery.
03:25To many of the ancient peoples of Earth, the Sun was not the center of the solar system.
03:30Often, Earth was considered the center of the universe.
03:34An excerpt from the film called A View of the Sky explains these views.
03:39First, we had to come out of the darkness and shed a world of mysteries and superstitious beliefs.
03:53First, we had to fight our way upwards to clarity and light,
03:57to take the position we thought belonged to us, the very center of creation.
04:20It was Claudius Ptolemaeus who devised the first complete system of the universe.
04:26Ptolemy, who lived in Alexandria around 200 A.D., said this,
04:31The Earth is the center of the universe.
04:34The Sun and the planets turn around it in circles.
04:38Beyond the planets lie the celestial sphere of stars, which also turns around the Earth.
04:46It is not surprising that Ptolemy should have placed the Earth and with it himself at the center of the universe.
04:53This was dictated to him by the Greek image of man, Greek love and respect for the human body and mind.
05:05The Greek knew that man was beautiful and that he was a hero, knew it beyond all doubt.
05:12That is why he created gods after his own image.
05:16And that is why he could conceive of only one place for himself in the universe, at the very hub.
05:24Nor is it surprising that Ptolemy's heavenly bodies should have moved in circles.
05:30Greek love for harmony is reflected by a love for geometric forms and above all for roundness.
05:38Nor were the Greeks content with just loving roundness.
05:42In typical Greek fashion, they systematized their instinct and promoted roundness to a principle of nature.
05:49Aristotle, the father of Greek physics, proclaimed the circle the perfect form.
05:55Circular movement, the perfect movement.
06:02Since the planets were bodies of divine nature, they could move only in circles.
06:07This to the Greeks was so obvious that it became the supreme law of their astronomy.
06:14Ptolemy's contribution of course is far more than having applied Greek philosophy to the sky.
06:20His great achievement is having brought the essence of Greek thought and Greek culture into agreement with observation.
06:28Today we know that the family of planets, asteroids and comets circle the Sun.
06:33We also know that our star is like a grain of sand on an infinite beach.
06:43There are so many stars that we cannot truly count them all.
06:53What is the model of the structure of our Sun, this average-sized star?
06:58For that and how we study the Sun, let's go to the motion picture universe narrated by William Shatner.
07:07Some small stars do not travel in the company of other stars.
07:11Our own Sun is one of these.
07:17To the astronomer, the Sun is a vast laboratory for the detailed study of a star's structure and energy.
07:25The vertical tower of the solar observatory supports a heliostat mirror which tracks the Sun,
07:32gathers its rays and reflects them down a light shaft that extends 300 feet below ground.
07:44At the end of the shaft, the rays are cast back to an observing room
07:48where minute-by-minute changes across the face of the Sun are observed.
07:55Another mirror projects a light beam to a spectroscope,
08:00an instrument which splits the light into its component colors, a visible spectrum.
08:06The dark lines that cut across the spectrum band
08:09are produced by the radiation from the Sun's interior shining through its atmosphere.
08:15Each line is the signature of a chemical element such as sodium, iron, calcium.
08:21It is this array of lines that forms the code which describes the properties and motion of a star.
08:30By narrowing the view of the Sun to a single line of the spectrum,
08:33each level of the solar atmosphere can be photographed,
08:38and each reveals a remarkably different aspect.
08:44And with the addition of computer mapping and color processing
08:48that distinguishes levels of brightness,
08:51a detailed and multidimensional picture is obtained of a Sun
08:55undergoing dramatic and turbulent change.
09:02The Sun is a sphere of hot, seething gases and surges of radiation.
09:09Most of the light we get from the Sun comes from the thin, bright layer
09:12which defines its visible edge, the photosphere.
09:19Above it, the chromosphere, a region of flaming outbursts of gas,
09:25extends through a transition zone to the thin outer atmosphere of the corona.
09:33Once thought to be a quiet layer of the solar atmosphere,
09:37the corona is now revealed to be a region of dramatic large-scale changes and unexpected turbulence,
09:44with temperatures reaching millions of degrees.
09:49Deep beneath the Sun's atmospheric shell is the core, a violent nuclear furnace.
09:58Here, hydrogen is fused into helium,
10:01and in the process, some of the matter is converted into an enormous amount of energy.
10:08Radiating outward as a gas, it convects like a boiling liquid beneath the surface.
10:15The turbulent, bubbling motion is visible in the granular cells of the photosphere.
10:24Sunspots, regions of intense magnetic fields, appear on the surface,
10:31disappear in a few hours,
10:34or grow and persist for months in a mysterious 11-year cycle.
10:45The Sun rotates once in 27 days.
10:49Because its equatorial regions rotate faster than the polar caps,
10:53the shearing action in the gas contorts the magnetic field into tangled structures
10:59which give rise to the Sun's eruptive action.
11:05Shaped by these magnetic fields are the spectacular prominences,
11:10titanic streamers of gas reaching heights of more than half a million miles above the surface.
11:20The greatest explosions in the solar system are flares,
11:26intense bursts of light erupting with the force of billions of hydrogen bombs.
11:33They move at hundreds of miles a second,
11:36then, after minutes or hours, they fade away.
11:43The dark areas across the solar disk are coronal holes
11:48which may provide new clues to the Sun's interior
11:52and may be a source of the solar wind that blows outward to the farthest planets.
11:58On Earth, effects of these solar events are visible
12:03when auroras light up the dark Arctic sky and radio communication is disrupted.
12:17The Sun is an average, middle-aged star
12:21yet it will generate heat and light for billions of years to come
12:25as it has for five billion years past.
12:28It dominates the motions of all bodies in the solar system.
12:33Parts of that film are based on facts gathered during the three Skylab flights.
12:38The three Skylab missions of the 1970s gave us more knowledge of our Sun
12:43than in all the previous history of the solar system.
12:46Several telescopes were mounted aboard Skylab.
12:49The last crew of three men spent almost three months in space,
12:53much of that time observing the Sun and making thousands of pictures.
12:58Here's another clip from the Helios film.
13:01NASA recently took solar research a long stride forward with its Skylab program.
13:07It is the first of its kind in the world.
13:11NASA recently took solar research a long stride forward with its Skylab program.
13:17From its spectacular Touch and Go mission in June 1973,
13:22Skylab returned 25,000 unique portraits of the Sun.
13:27Scientists estimate that the Sun will burn for another five billion years.
13:33Its energy is created through nuclear fusion,
13:36but little else is known about the Sun's surface.
13:38Solar research is vital to our control over physical conditions on this planet.
13:44A better understanding of the Sun can help us cope with its menacing and dangerous aspects.
13:51During solar eruptions, compass needles on airplanes may swing erratically.
13:56Ship communications could black out.
13:58An ability to predict such eruptions would help prevent many tragedies.
14:02Storms, tornadoes, and hurricanes could be anticipated
14:05if we understood what is happening on the Sun's surface.
14:09The Helios mission is an important advance in the exploration of the Sun's activity.
14:15The results of Skylab came to us because telescopes and other instruments
14:20were carried above the Earth's interfering atmosphere.
14:23Many of the observations of the Sun made from Skylab
14:27are impossible to make from the ground because observation in parts of the spectrum is not possible.
14:32Dr. Richard Towsey explains an instrument called a spectroscope,
14:36which was used by Skylab's astronauts to dissect the Sun's ultraviolet light for study.
14:42Here's a small sample section of three of the spectra.
14:46On this scale, the whole spectrum would be about 100 feet long.
14:51This instrument is so powerful that it can separate nearly 100,000 different ultraviolet colors.
14:58Just what do all these black line images mean?
15:02Each atom produces its very own combination of spectral lines,
15:07just as each one of us has his own very special set of lines on his fingertips.
15:13So, if we have a complete list of atomic fingerprints,
15:18and we do have a tremendous data file on atomic spectra,
15:22we can tell exactly what atoms are present.
15:26More yet, by studying the intensities of the lines and their widths,
15:32we can say what the conditions were at the place on the Sun that the instrument was observing.
15:38We can calculate the temperature and the density.
15:42We can make a chemical analysis,
15:45and we can even derive the velocities of the atoms.
15:49This is what the Sun looks like in the extreme ultraviolet,
15:52and it is what the astronaut will see produced on his scope
15:57by the closed-loop extreme ultraviolet TV monitor that forms a part of the B instrument.
16:03The spectrograph slit is very tiny,
16:07something like this little red sliver, if you can see it.
16:12There are all sorts of different features and phenomena on the Sun's disk,
16:18and above its limb in the corona.
16:23These regions are the active areas,
16:28which are the spawning ground for solar flares.
16:32We can place the slit here,
16:35move it around,
16:37explore the structure of the region,
16:41and we can hope to be lucky enough to catch a flare.
16:47Or we can slew the ATM
16:51to point at this curious bright ring
16:55that surrounds most of the Sun
16:58and study the conditions at the limb.
17:01By moving the slit out,
17:03we can investigate the changes in the Sun's atmosphere
17:07at height intervals of about 500 miles,
17:10much as the meteorologist studies the Earth's atmosphere
17:14with sounding balloons.
17:17Why do we want to do all this?
17:20Because we still do not understand very well
17:24how the tremendous energy of the Sun escapes.
17:28The outer Sun's atmosphere, or corona,
17:31has a temperature of a million degrees,
17:34but inside the corona,
17:36the edge of the Sun is at only 4,000 degrees.
17:40We all know that heat flows from hot to cold,
17:44but never from cold to hot.
17:47Even more mysterious and closer to our lives
17:51is the solar cycle.
17:53Happily, the Sun is almost absolutely constant.
17:58But in the extreme ultraviolet and X-rays,
18:02the part studied by Skylab,
18:05it is anything but constant.
18:07In X-rays, every 11 years,
18:10it goes from almost nothing
18:11to very great intensities,
18:14and back to nothing.
18:16It is certain that the solar cycle
18:19has controlled the Earth's climatic changes
18:22from prehistoric times.
18:24Many of us think it has a lot to do
18:27with our monthly weather.
18:29In any case, the Sun is the object
18:32that is most important to life,
18:35and we must learn all we can about it.
18:39Dr. Towsey also described
18:41some of the early results of Skylab,
18:43just a few of the thousands of facts gathered.
18:46In the corona, the Sun's disk is dark,
18:50with most of the emission above the limb.
18:54The active regions on the disk itself
18:57show all kinds of fantastic forms,
19:00but loops are still present,
19:03and it is clear that magnetic fields
19:06extend way up into the corona.
19:09The large amount of information
19:12gathered during the Skylab mission
19:14is still being analyzed
19:16by scientists and astronomers.
19:18Hundreds of articles have been published
19:20in the scientific journals.
19:22Pictures tell us the story
19:24in a simpler way.
19:26In its quiet times,
19:28the Sun is far from calm.
19:30It is a churning ball of hot gases.
19:33Its surface has bubbling granules.
19:34Sunspots come and go.
19:42During its quiet periods,
19:44observations from Skylab and the ground
19:47led to a better understanding
19:49of the solar atmosphere,
19:51temperature, density,
19:53chemical composition,
19:55magnetic fields, and physics.
19:57From analysis of thousands of pictures
19:59of the Sun taken in the ultraviolet spectrum,
20:02we have gained new insights
20:04on how wave energy
20:06is transmitted upward
20:08to heat the outer layer of the Sun.
20:10Ultraviolet pictures were processed
20:12at color code differences.
20:17Green shows part of the Sun
20:19called the chromosphere
20:21with temperatures of about
20:2335,000 degrees Fahrenheit.
20:27Red reveals the hotter part
20:29of the chromosphere,
20:31which is almost 270,000 degrees Fahrenheit.
20:35Blue shows us the corona
20:38with temperatures around
20:402.5 million degrees Fahrenheit.
20:47The poles of the Sun
20:49were found to be different
20:51from the rest of the star.
20:53At the poles,
20:55the solar atmosphere is stretched upward
20:57and there are long-lived holes
20:59in the corona.
21:01At these holes,
21:02heat and solar particles
21:04of the solar wind
21:06can flow easily into space.
21:17That the coronal holes
21:19are clearly the source
21:21of solar wind disturbances
21:23was an important finding.
21:25The solar wind affects
21:27the Earth's upper atmosphere.
21:29Changes in the upper atmosphere
21:30affect radio communications
21:32as well as weather on Earth.
21:44Like scattered jewels,
21:46bright points of light
21:48dot the solar disk
21:50in this X-ray picture.
21:56Scientists checked
21:58magnetic maps of the Sun
22:00and found that bright points
22:02overlie compact magnetic regions
22:04that have both positive
22:06and negative polarity.
22:08About 100 of these bright points
22:10can be seen at one time
22:12on the Sun's hemisphere
22:14and they come and go
22:16at about 8-hour intervals,
22:18though some last longer
22:20and others are gone in a few minutes.
22:24X-rays are emitted
22:26by the Sun's high-temperature gases,
22:28so only the hot corona is seen.
22:30Almost 60,000 X-ray pictures
22:32of the corona were taken.
22:34Scientists learned
22:36that the corona is built
22:38entirely of magnetic loops
22:40and arches.
22:54Cloud-like extensions
22:56of the chromosphere
22:58are called solar prominences.
23:00They are associated
23:02with magnetic fields
23:04on the Sun's surface.
23:06These long ribbons
23:08persist for weeks
23:10or months before fading.
23:14The Sun's outer atmosphere,
23:16or corona,
23:18reaches out millions of miles.
23:20One of Skylab's telescopes
23:22masked the Sun's disk
23:24creating artificial eclipses.
23:26Eight months of eclipse observation
23:28were done by Skylab
23:30as compared to less than 80 hours
23:32observed from all the natural eclipses
23:34since the use of photography
23:36began in 1839.
23:42The outer corona was found
23:44to be constantly changing.
23:49The Sun is a seething inferno.
23:52There are huge eruptions
23:54and explosions.
23:58All this Skylab showed us
24:00in detail we had not seen before.
24:08Immense clouds of coronal material
24:10called transients
24:12are propelled outward
24:14by flares and prominence eruptions.
24:16The Sun can have violent periods.
24:24We learned a lot from Skylab
24:26but we still have much to learn
24:28about the star that keeps
24:30changing.
24:33In 1986,
24:35NASA plans to launch
24:37the International Solar Polar Mission.
24:39The shuttle will carry
24:41the Lewis Centaur rocket
24:43into low Earth orbit.
24:45The Centaur will ignite
24:47sending the probe to the Sun.
24:54The objective is to learn more
24:56about the Sun's polar regions
24:58and the space around them.
25:00As we saw,
25:02the polar regions are the source
25:04of the solar wind
25:06which affects radio communications
25:08and the weather.
25:20Man shall continue to study the Sun
25:22because his curiosity is insatiable
25:27and because we are of the Sun.
25:31Without it,
25:33we would not exist
25:35and we must understand
25:37how it affects our weather,
25:39our communications
25:41and our destiny.
25:57That brings us
25:58to the end of our first episode,
26:00Our Star of the Sun.
26:08Next time,
26:10during this 13-program journey
26:12through the solar system,
26:14we will preview the planets
26:16and examine in detail Mercury,
26:18the planet nearest the Sun.
26:29This is Larry Ross
26:31saying goodbye
26:33from NASA's Lewis Research Center
26:35in Cleveland, Ohio.
26:58NASA Jet Propulsion Laboratory
27:00California Institute of Technology
27:29NASA Jet Propulsion Laboratory
27:31California Institute of Technology
27:58California Institute of Technology