Basic Astronomy

Basic Astronomy

What makes the planets move the way they do?

To begin with, there is some misunderstanding as to just what is meant by the term universe. Often popular writers use it to mean the particular group of stars to which our Sun belongs. As the astronomer uses the term, however, it is considered to mean the sum total of all the stars and other cosmic bodies.

Scientists do not know as yet how the universe originated and developed. The most useful idea about it so far is that set forth by Albert Friedmann in 1922. He based his ideas on Einstein’s relativity theory. According to Dr. Friedmann, everything in the universe was at one time packed together into a tiny point. This means all energy as well as matter – remember that the one can be converted into the other as is demonstrated by atomic power plants. Well, since all the energy and all of the matter in existence were confined in such a small space, the pressures were tremendous. The result was an enormous explosion.

Stars and galaxies… Could it be, intelligent life is awaiting for us somewhere in the Universe. Illustration: Elena (Megan Jorgensen)

After this explosion, every particle in the universe began to move away from every other particle. This is the theory of the expanding universe. American astronomer Edwin Hubble found good evidence that it is the truest picture of the cosmos that we have.

If you want to know how every particle in the universe can move away from every other particle, consider the example of a child’s balloon. If you make a series of ink dots at random on the balloon’s surface and then blow it up, you will find that the distances between every given spot and all of the other spots increase.

When the primordial universe exploded, its particles were those of atom of hydrogen gas and dust. Some quantities of this condensed into stars, and groups of stars began to congregate as galaxies. Not all of them did, however, and there are still great clouds of dust and hydrogen in the universe.

Those astronomers who go along with this theory believe that the universe will keep expanding until some definite time far off in the future. Then the particles will begin to come together again. The universe will shrink once more into an infinitesimal point, the internal pressures will increase, and there will be another explosion.

Thus, over countless years, the universe will alternately shrink and expand. It is interesting to compare this theory with the ancient Hindu concept in which the god Brahma breathes the entire cosmos in and out, each breath lasting billions of years.

It is possible for astronomers to observe the rate at which the universe is expanding. Once they learned that rate, it was only a matter of working backwards to find the time when it had started. That was approximately 15 billion years ago.

We know that light travels at a certain speed, actually 186 thousand miles per second. If the universe is fifteen billion years old, than no light can reach us that comes from a distance farther than that which light can travel in that time. That distance, by the way, is 90 sextillion miles, – a figure we can represent by 90 with 21 zeroes following it.

Now, if astronomers can locate objects in the universe that are 90 sextillion miles away, then their light must have started out from them 15 billion years ago. But 15 billion years is the age of the universe. So the light from those objects must have begun its trip at the time the universe was formed.

In 1963, astronomers first discovered those bodies. They not only give off the light, but radio waves as well. The interesting question is, since their light comes from the most distant possible point in the universe, when we look at them, are we seeing the light that was given off at the time the universe was created? And what are they like now?

The groups of stars that formed when the universe began to expand are known as galaxies. The galaxy in which our Sun is located is popularly called the Milky Way. It looks like a bright band of millions of stars that sweeps across the sky. Actually, it has been estimated that it is made up of over 200 billion separate stars.

We see the Milky Way as a band because of the way that we are positioned in it. It is really shaped like a Fourth of July pinwheel. The Earth is so situated that we look across the narrow edge of the pinwheel. In our galaxy, our Sun is a rather small and aging star.

Astronomers know that by the kind of light that it gives off. If it were younger, the light would be bluer. The Sun, when it set, will appear as a blue ball instead of a red one.

The next star to our Sun is Alpha Centauri. It is about 26 trillion miles away. The light that arrives here from Alpha Centauri started out over four years ago. There is some evidence that there are planets circling this star.

Our Sun does not remain still in the galaxy. It moves at a constant rate towards a point in the constellation of Hercules, dragging the solar system of planets along with it. It is at this point that the galaxy becomes to students of astrology. Professor Giorgio Piccardi of the University of Florence in Italy showed that forces which apparently originate in the galaxy are capable of altering the rate of chemical reactions, some of which involve compounds analogous to those found in human issues. This has suggested that the forces which make astrology “work” may not originate in the solar system at all, but at some point in the Milky Way or even beyond.

At this point we have moved from the universe and into the galaxy. We will now go from the galaxy down into the solar system proper.

Astronomers estimate that the solar system is 4, 5 billion years old. When the explosion occurred, the universe was filled with clouds of gas and dust. Gravity drew the particles of these together causing huge incandescent bodies – the stars – to condense out of the contracting clouds. One of those bodies was our Sun. Out of the remains of the cloud from which the Sun was formed, the planets appeared. Probably they were originally rings of dust that rotated around the Sun’s equator. Eventually the condensed into spheres of more or less solid matter.

The planets are arranged roughly on a plane that extends from the Sun’s equator. They move a little above and below that plane at different times. The distance they are above and below the plane is known as planet’s latitude. The plane itself is known as the ecliptic.

The Sun has no declination. The reason is that declination is measured from the Earth, and, from that viewpoint, the ecliptic passes through both the Earth’s and the Sun’s centers.

Now, though the ecliptic passes through the Earth’s center, it does not coincide with the Earth’s equator. The Earth is tilted off-center on its axis by about 23 degrees. Because the ecliptic and the equator do not coincide, from our point of view the Sun appears to go below the equator in winter and return above in in the summer.

The times at which it crosses the equator are known as the autumnal equinox – and the vernal equinox.

The Earth turns on its axis at a regular rate, on revolution per day. For convenience geographers divided the Earth into 360 divisions along the equator. Those are called degrees of longitude pass by given point in 24 hours. This is at the rate of 15 degrees per hour or one degree every four minutes.

The particular degree on which you are situated is called your meridian. It is also the highest point that the Sun will reach any day. This is the location of the medium coeli (M.C) or Midheaven. The meridian passes through the zenith or the point in the sky directly over your head. The zenith is always the same number of degrees above the equator which gives them their ship’s latitude.

Another method of measuring positions in the sky is by their hour angle. We saw that the Earth moved at the rate of one degree every four minutes. For us, that means that the heavenly bodies seem to move over our heads at the same rate. We can locate a body by saying how long it will take to reach our meridian or by how long it has been since it passed our meridian.

For instance, let us say that a body is located 15 degrees to the east of our meridian. We know that at the rate of four minutes for each degree, it will take 4 times 15 minutes or one hour to come to our meridian. Thus we say that the body has an hour angle of one hour east. If it had passed the meridian and was 15 degrees away, we would say it was one hour west.

Blazing a Trail Around the Sun

Blazing a Trail Around the Sun

First series of interplanetary Pioneers, extensions of the initial Pioneer program completed with Pioneer 5 in 1960, were seeking a better understanding of the Sun and its impact on the space environment. About 37 inches in diameter and 35 inches high, and weighing about 140 pounds, the Pioneer spacecraft allowed scientists to predict space “weather” with increasing accuracy.

The first of the new series, Pioneer 6, was launched in 1965 on an “inward” path. Its solar orbit oranges more than 20 million miles inside the Earth’s orbit. Pioneer 7, launched in 1966 and Pioneer 8, launched in 1967, both followed “outward” paths, ranging as far as 13 million and 9 million miles, respectively, beyond Earth’s orbit around the Sun. Pioneer 9 was launched in 1968 into another inward orbit like that of Pioneer 6.

Two Velas undergoing non-reflective testing of electronic systems in a plastic-spiked sound-proof chamber. Photo in public domain

Nuclear watchdogs patrol dual circular orbit

An intricate three-part launch and injection technique is used to position TRW’s Vela nuclear detection satellites in orbit. First, two satellites are tandem-launched into a wide-ranging elliptical transfer orbit. Next, as they reach the 60-70,000-mile apogee of the transfer orbit for the first time, an injection motor – mounted on each spacecraft – fires and sends one of the satellites into a circular orbit, leaving its twin in the transfer orbit. Then, with the second Vela completes one more revolution and returns to the original apogee, it too is injected into a circular orbit. By this time, the first Vela has traveled in its orbit to a point about 150 degrees away or almost to the other side of the Earth. The two spacecraft are then in the same orbit on nearly opposite sided of the planet.

Designed and manufactured by TRW for the Air Force, the 500-pound spacecraft carry delicate sensors which can detect nuclear weapons testing anywhere on Earth or in the atmosphere – or even as far away as Venus and Mars.

Solar System

The Solar System

The term “Solar system” is used to designate the group of celestial objects which travel through space under the gravitational attraction of the Sun. In addition to the Sun, it consists of eight planets with their satellites, several thousand asteroids, as well as comets and countless meteors.

At the centre of this system is the Sun, an enormous mass of glowing gas whose surface temperature is roughly 5,500 degrees Centigrade. In the Sun is concentrated the greatest mass in the system – about 99% – and hence it is dominating body, exerting a controlling influence over the motions of the other members.

Year after year the planets continue to follow their respective paths around the Sun with periods which vary from 88 days for Mercury to 248 years for Pluto, an “ex-planet”, considered today as a big asteroid. Mercury is the nearest to the Sun, and is at a mean distance of 36,000,000 miles, while Pluto is the farthest “planet-asteroid”, with a mean distance of 3,664, 000, 000 miles.

Illustration by Elena

The names of the planets in order of increasing distance from the Sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto used to be classified as a planet, but is considered an asteroid now, with other asteroids situated mainly between Mars and Jupiter. Accompanying six of the planets as they travel through space are 32 satellites or moons. In keeping with its enormous size, Jupiter has the greatest number of moons, namely 12, next comes Saturn with 10, then Uranus with 5, Mars and Neptune with 2 each and lastly the Earth with only one. While the sizes of the satellites are not all known, it is believed that those of Mars are the smallest, having diameters of the order of 5 and 10 miles respectively.

The diameters of the planets vary greatly, from 3,100 miles in the case of Mercury to 88,700 miles for Jupiter. The asteroids are in quite a different category, for their diameters range from less than a mile to 480 miles. By way of contrast the diameter of the Sun is 8644,000 miles.

In the endless journey around the Sun, the Earth encounters numerous small objects which we often see flashing across the sky. These are meteors – sometimes called “falling stars”. It is estimated that many millions of them enter the Earth’s atmosphere daily, but relatively few survive the swift flight through our protective blanket of air to reach the Earth’s surface as meteorites.

Finally a word about comets, those strange objects which in most cases are too faint to be seen except through a telescope. For many of them orbits have been computed and their times of return to the vicinity of the Sun are known and carefully observed. Comets like Halley’s, which are bright enough to excite popular interest, are quite rare, and during the years which elapse between their visits to the Sun’s neighbourhood, they are travelling at great distances from the Sun, often far beyond the orbits of the distant planets.

Mercury: Mean distance from Sun (millions of miles) = 35,98; distance from Earth (millions of miles) = 50 -136; period of revolution = 88 days; period of axial rotation at equator = 59 days; Equatorial Diameter – Miles: 3,100; Mass (Earth=1) = 0,056; Number of satellites = 0; Density (Water = 1) 0,054.

Venus: Mean distance from Sun (millions of miles) = 67; distance from Earth (millions of miles) = 26 -160; period of revolution = 225 days; period of rotation = 244 days; Equatorial Diameter – Miles: 7,700; Mass (Earth=0,817); Number of satellites = 0; Density (Water = 1) = 4,99.

Earth: Mean distance from Sun (millions of miles) = 93; distance from Earth (millions of miles) = 0; period of revolution = 365 days; period of rotation = 23 hours 56 minutes; Equatorial Diam-Miles: 7,927; Mass (Earth=1)=1; Number of satellites = 1; Density (Water = 1) = 5,52.

Mars: Mean distance from Sun (millions of miles) = 142; distance from Earth (millions of miles) = 368 -600; period of revolution = 687 days; period of rotation = 24 hours 37 minutes; Equatorial Diam-Miles: 4,200; Mass (Earth=1)= 0,108; Number of satellites = 2; Density (Water = 1) = 3,94.

Jupiter: Mean distance from Sun (millions of miles) = 483; distance from Earth (millions of miles) = 368-600; period of revolution = 12 years; period of rotation = 9 hours 50 minutes; Equatorial Diam-Miles: 88,700; Mass (Earth=1) =318, 0; Number of satellites = 12; Density (Water = 1) = 1,33.

Saturn: Mean distance from Sun (millions of miles) = 886; distance from Earth (millions of miles) = 784 – 1,028; period of revolution = 29, 5 years; period of rotation = 10 hours 14 minutes; Equatorial Diam-Miles: 75,100; Mass (Earth=1) = 95, 2; Number of satellites = 10 (?); Density (Water = 1) = 0,71.

Uranus: Mean distance from Sun (millions of miles) = 1,782; distance from Earth (millions of miles) = 1,606 – 1,958; period of revolution = 84 years; period of rotation = 10 hours 49 minutes; Equatorial Diam-Miles: 29,200; Mass (Earth=1) = 14, 6; Number of satellites = 5 (?); Density (Water = 1) = 1,70.

Neptune: Mean distance from Sun (millions of miles) = 2,792; distance from Earth (millions of miles) = 2,674 – 2,910; period of revolution = 165 years; period of rotation = 14 hours (?); Equatorial Diam-Miles: 27,700 (?); Mass (Earth=1) = 17,3; Number of satellites = 2 (?); Density (Water = 1) = 2.26.

Pluto (asteroid): Mean distance from Sun (millions of miles) = 3,664; distance from Earth (millions of miles) = 91, 3-94, 4; period of revolution = 248 years; period of rotation = 6, 39 days (?); Equatorial Diam-Miles: 3, 500; Mass (Earth=1) = 0,06; Number of satellites=0; Density (Water = 1) = 5.5.

Moon: Mean distance from Sun (millions of miles) = 93; distance from Earth (millions of miles) = 22, 000 – 253,000; period of revolution = 27 days 7 hours, 7 minutes; period of rotation = 27 days, 7 hours, 7 minutes; Equatorial Diam-Miles: 2,160; Mass (Earth=1) = 0, 012; Number of satellites=0.

Sun: Mean distance from Sun (millions of miles) = 0; distance from Earth (millions of miles) = 91, 3 = 94, 4; period of revolution = n.a.; period of rotation = 25 – 35 days; Equatorial Diam-Miles: 864,000; Mass (Earth=1) = 333,000,0; Number of satellites = 8 planets (+ Pluto) + thousands of asteroids, comets and meteors.

Data taken from the Handbook of the British Astronomical Association.

Additions to the Solar System

Besides controlling the earth and the five planets of antiquity, the sun holds sway over three other planets, Uranus, Neptune, and Pluto, and also over a large number of fly-weight bodies called minor planets or planetoids. Of these additions, Uranus and the minor planet Ceres can be glimpsed with the unaided eye, but only when conditions are particularly favourable. All the rest look like stars even in quite large telescopes, and are therefore not shown in the Planetarium sky. They make themselves known in the real sky by their motions relative to the fixed stars.

Incredibly reach world… Illustration: Megan Jorgensen.

Space Portfolio

A Space Portfolio

Each of the 26 flights that the U.S. has sent into space up through Apollo 16 is represented here, from the first Mercury launch in 1961 through the two-man Gemini series in the mid-‘60s to Apollo’s successful assault on the Moon:

(The missing flight numbers – for example, Mercury 1 and 2 – represent missions that were unmanned tests).

Illustration by Elena

Mercury:

(a) Alan Shepard aboard Mercury 3 spacecraft just before the first U.S. suborbital flight.

(b) Mercury 4 on the pad a few days before it carried Virgil Grissom into space.

(c) New York welcomes John Glenn, accompanied by wife and Vice President Johnson, after first U.S. earth-orbiting mission in Mercury 6.

(d) Scott Carpenter awaits pickup in Pacific after landing 250 miles off target in Mercury 7.

(e) Mercury 8`s Wally Schirra takes a joyful postflight stretch on carrier deck.

(f) Navy recovery team picking up Gordon Cooper and his Mercury 9 spacecraft.

Gemini:

(g) Grissom and John Young preparing to board Gemini 3.

(h) Ed White takes first U.S. spacewalk during flight of Gemini 4.

(i) Gemini 5 lifts off from the Cape.

(j) A view of Gemini 7 from Gemini 6 during the first rendezvous in orbit.

(k) Frogmen attaching flotation collar to Gemini 6, which was belatedly launched after Gemini 7.

(l) Agena target rocket with which Gemini 8 completed first space docking.

(m) A balking protective shroud on another Agena that to Gemini 9’s Tom Stafford looked like “an angry alligator”.

(n) Gemini 10’s Young and Michael Collins.

(o) A view of Indian subcontinent – and protruding spacecraft antenna – from Gemini 11.

(p) Edwin “Buzz” Aldrin climbs out of Gemini 12.

Apollo:

(q) Third-stage Saturn 4B booster after separation from Apollo 7.

(r) Earthrise seen by Apollo 8 as it emerges from far side of Moon on Christmas Eve.

(s) Dave Scott pokes head out of Apollo 9’s command module Gumdrop.

(t) Apollo 10’s lunar-module Snoopy just before rejoining command ship Charlie Brown in first docking in lunar orbit.

(u) Father and son look across Banana River at Apollo 11 lifting off for first lunar landing; Aldrin standing at attention near flag at Tranquillity Base.

(v) Apollo 12’s Pete Conrad, Richard Gordon and Al Bean beginning post-flight quarantine aboard carrier Hornet.

(w) As Navy chaplain offers prayers, Apollo’s 13 James Lovell, James Haise and John Swigert bow their heads after their near disaster in space.

(x) Apollo 14’s lander Antares at dawn of a lunar day.

(y) Crew of Apollo 15 being hoisted aboard recovery helicopter after splash-down.

(z) Young riding Apollo 16’s lunar rover in Moon’s Descartes region.

(Time, 11 December 1972)

Apollo 17: Farewell Mission to the Moon

Apollo 17: Farewell Mission to the Moon

Once again the Earth will tremble for miles around. Once again tongues of flame will spill across Cape Kennedy`s Pad 39A. Once again a mighty rocket will lift into the sky. But, if all goes according to plan, this week`s scheduled blast-off of Apollo 17 will be remarkably different from past launches.

It will take place at night, turning dark into daylight at the cape, presenting a fiery spectacle that may be seen by millions of people from Cuba to as far north as the Carolinas. The magnificent display will serve as a fitting farewell not only to the departing astronauts but to the entire Apollo program. For with the launch of Apollo 17, the US is bringing to an end its exploration of the Moon.

Historians will have a difficult time explaining the decision to abandon the Apollo program. Having trained the men, perfected the techniques and designed the equipment to explore the Earth`s own satellite, having achieved the ability to learn more about man`s place in the universe, Americans lost the will and the vision to press on. Barely three years after the first lunar landing, the nation that made it all possible has turned its thoughts inward and away from space.

Apollo 17 Crew. The scenario for a space odyssey excited mankind in the 1960s, with the awesome accomplishements of the Apollo program. The prime crew for the Apollo 17 lunar landing mission are: Commander, Eugene A. Cernan (seated), Command Module pilot Ronald E. Evans (standing on right), and Lunar Module pilot, Harrison H. Schmitt. They are photographed with a Lunar Roving Vehicle (LRV) trainer. Cernan and Schmitt will use an LRV during their exploration of the Taurus-Littrow landing site. The Apollo 17 Saturn V Moon rocket is in the background. This picture was taken at Pad A, Launch Complex 39, Kennedy Space Center (KSC), Florida. Photo taken on 30 September 1971.

Three additional manned missions to the Moon originally planned by NASA have been canceled for lack of congressional funding and public support. Though the U.S. spent $5.9 billion to develop the complex Apollo system of rockets, the production of Saturn boosters has been halted. The painstakingly assembled team of skilled technicians, engineers and scientists that made Apollo possible is slowly being disbanded.

Despite gloom at the Manned Spacecraft Center in Houston, there are encouraging signs that man`s ability to explore the solar system will not be completely lost. Next year NASA will use one of its surplus Saturns to launch Skylab, a primitive orbital station in which three men will remain in space for up to 56 days. In 1975 a spare Apollo will take part in the greatly publicized linkup with a Soviet Soyuz, an operation that will serve as a gesture of amity between the two great space rivals and also help develop space-rescue techniques. Finally, in the late 1970s NASA hopes to fly its vaunted space shuttle – a hybrid of spaceship and rocket plane that could ferry men and supplies to orbital launch pads for journeys far beyond the Moon.

In America and elsewhere, there are those who have branded the moon landings as brazen propaganda ploys or technological stunts. They prisoners of limited vision who cannot comprehend, or do not care, that Neil Armstrong`s step in the lunar dust will be well remembered when most of today`s burning issues have become mere footnotes of history.

Yet even those who have pressed hardest for an end to manned space flight so that funds can be diverted to social needs on earth, cannot gainsay Apollo`s ultimate value. The dramatic landings on the Moon won acclaim and worldwide respect for America in a decade when the U.S. garnered more disapproval and distrust that at any other time in its history. Wherever touring astronauts appeared, on either side of the Iron Curtain, they were cheered by huge, admiring crowds.

Apollo Rocket. Photo in public domain

But Apollo`s contributions go far beyond nationalistic considerations and even the highly touted technological spin-offs from space (like fuel cells and miniature computers). The moon flights have made man aware of the finiteness of his planet and the bonds between the people who dwell on it. “To see the Earth as it truly is,” wrote Poet Archibald MacLeish after Apollo 8`s Christmas Eve orbit of the Moon in 1968, “is to see ourselves as riders on the Earth together, brother on that bright loveliness in the eternal cold”.

Anti-Science. As Science Fiction Writer Ray Bradbury recalls H.G. Wells have anticipated the anti-science movement in his screenplay for the classic 1936 movie Things to Come. In the film a raging mob – including the intellectuals of the day – besiege the first spaceship to be launched from Earth. “We don`t want mankind to go out to the moon and the planets!” shouts the mob`s leader. “We shall hate you more if you succeed than if you fail. Is there never to be calm and happiness for man?” Despite the protests, the moonship is shot skyward from a space cannon and on onlooker philosophies: “For man, no rest and no ending. He must go on – conquest beyond conquest”. Many Americans today have begun to wonder just how long and how far Western man can continue these conquests: whether the relentless, Faustian striving to dominate nature should not give way to the Eastern ideal of living in harmony with nature.

It is a genuine and perhaps momentous issue. But chances are that the modern world`s answer will remain Well`s answer: that man must first conquer “this little planet, its winds and ways, and all the laws of mind and matter that restrain him. Then the planets about him, and at last out across immensity to the stars. And when he has conquered all the deeps of space and all the mysteries of time, still he will be beginning.”

Time, December 11, 1972