The Awesome Universe—Where Did It Come From?

So Mysterious, Yet So Beautiful

THIS time of the year, the night sky beckons with bejeweled splendor. High overhead strides mighty Orion, easily visible on January evenings from Anchorage, Alaska, to Cape Town, South Africa. Have you had a good look recently at the celestial treasures to be found in well-known constellations, such as Orion? Astronomers took a peek not long ago using the recently repaired Hubble Space Telescope.

From the three stars of Orion's belt dangles his sword. The fuzzy star in the middle of the sword is not really a star at all but the famous Orion Nebula, an object of striking beauty even when seen through a backyard telescope. Its ethereal glow, however, is not the secret of its fascination for professional astronomers.

"Astronomers investigate the Orion Nebula and its many young stars because it is the largest and most active region of starbirth in our part of the Galaxy," reports Jean-Pierre Caillault in Astronomy magazine. The nebula appears to be a cosmic maternity ward! When the Hubble telescope photographed the Orion Nebula, capturing details that had never been seen before, astronomers saw not just stars and glowing gas but what Caillault describes as "fuzzy little ovals. Blots of orange light. They resemble specks of one's lunch dropped accidentally onto the photo." Scientists believe, however, that rather than darkroom defects, these fuzzy ovals are "protoplanetary disks, the first solar-systems-in-the-making viewed from a distance of 1,500 light-years." Are stars—indeed, entire solar systems—being born at this moment in the Orion Nebula? Many astronomers believe they are.

Deep inside the Orion Nebula—a cosmic maternity ward?

From Maternity Ward to Stellar Graveyard

As Orion strides forward, bow in hand, he seems to confront the constellation Taurus, the bull. A small telescope will reveal, near the tip of the bull's southern horn, a faint patch of light. It is called the Crab Nebula, and in a large telescope, it appears to be an explosion in progress. If the Orion Nebula is a stellar nursery, then the Crab Nebula next door may be the grave site of a star that suffered a death of unimaginable violence.

That heavenly cataclysm may have been recorded by Chinese astronomers who described a "Guest Star" in Taurus that suddenly appeared on July 4, 1054, and shone so brightly that it was seen during the daytime for 23 days. "For a few weeks," notes astronomer Robert Burnham, "the star was blazing with the light of about 400 million suns." Astronomers call such a spectacular stellar suicide a supernova. Even now, nearly a thousand years after the observation, the bombshards from that blast are racing through space at a speed estimated at 50 million miles [80 million km] per day.

Supernovas, Pulsars, and Black Holes

At the heart of the Crab Nebula lies one of the strangest objects in the known universe. According to scientists, the tiny corpse of a deceased star, compressed into unbelievable densities, spins in its grave 30 times per second, sending out a beam of radio waves that were first detected on earth in 1968. It is called a pulsar, described as a spinning supernova remnant so compressed that the electrons and protons in the atoms of the original star have been squeezed together to produce neutrons. Scientists say it was once the massive core of a supergiant star like Betelgeuse or Rigel in Orion. When the star exploded and the outer layers were blasted into space, only the shrunken core was left, a glowing white-hot cinder, its nuclear fires long extinguished.

Imagine taking a star as massive as two of our suns and squeezing it into a ball 10 to 12 miles [15 to 20 km] in diameter! Imagine taking the planet Earth and squeezing it down to 400 feet [120 m]. A cubic inch [16 cu cm] of this material would weigh more than 16 billion tons.

Even this does not appear to be the final word on compressed matter. If we were to shrink the earth all the way down to the size of a shooter's marble, the earth's gravitational field would finally become so strong that not even light could escape. At this point our tiny earth would seem to disappear inside what is called a black hole. Although most astronomers believe in them, black holes still have not been proved to exist, and they do not appear to be as common as was thought a few years ago.

The Andromeda galaxy, the most distant object visible to the naked eye. Its rotation rate seems to violate Newton's law of gravity and raises the question of dark matter invisible to telescopes

The Hubble Space Telescope has been at work in this area too, peering deep into the heart of the nebula and discovering "details in the Crab that astronomers never expected," according to Astronomy magazine. Astronomer Paul Scowen says the discoveries "should have theoretical astronomers scratching their heads for some time to come."

Astronomers, such as Harvard's Robert Kirshner, believe that understanding supernova remnants like the Crab Nebula is important because they can be used to measure the distance to other galaxies, which is currently an area of intense research. As we have seen, disagreements over the distances to other galaxies have recently touched off a lively debate over the big bang model of the creation of the universe.

Beyond Taurus, but still visible in the Northern Hemisphere in the western January sky, is a soft glow in the Andromeda constellation. That glow is the Andromeda galaxy, the most distant object visible to the naked eye. The wonders of Orion and Taurus are in our own cosmic backyard—within a few thousand light-years of Earth. Now, however, we gaze across an estimated two million light-years at a great spiral of stars much like our own galaxy, the Milky Way, but even larger—some 180,000 light-years from end to end. As you look at the gentle glow of Andromeda, your eyes are bathed in light that may be over two million years old!

How Do They Know How Far It Is?

When astronomers tell us that the Andromeda galaxy is two million light-years away, they are really giving us an educated guess. No one has come up with a way to measure such mind-boggling distances directly. Distances to the very closest stars, those within 200 light-years or so, can be measured directly by stellar parallax, which involves simple trigonometry. But this only works for stars so close to the earth that they appear to move slightly as the earth goes around the sun. Most stars, and all galaxies, are much farther away. At that point the guesswork begins. Even stars in our own backyard, such as the famous red supergiant Betelgeuse in Orion, are subject to guesswork, with estimated distances for it ranging from 300 light-years to over 1,000. It should not surprise us, therefore, to find disagreement among astronomers regarding galactic distances, which are a million times greater.

In recent years Margaret Geller and others have embarked on ambitious programs to map all the galaxies around us in three dimensions, and the results have raised serious questions for the big bang theory. Instead of seeing a smooth distribution of galaxies in every direction, the cosmic cartographers discovered a "tapestry of galaxies" in a structure extending for millions of light-years. "How that tapestry was woven from the nearly uniform matter of the newborn universe is one of the most pressing questions in cosmology," according to a recent report in the respected journal Science.

We began this evening with a look at our January night sky and quickly discovered not only heart-stopping beauty but also questions and mysteries that pertain to the very nature and origin of the universe. How did it begin? How did it arrive at its present stage of complexity? What will happen to the celestial wonders that surround us? Can anybody say? Let us see.

The Cartwheel galaxy. A smaller galaxy collided with it, careened through it, and the smaller galaxy left in its wake the blue ring of billions of newly formed stars surrounding the Cartwheel galaxy

The Cat's Eye Nebula. The effect of two stars orbiting each other most easily explains the intricate structures

Are Those Colors Real?

People who scan the sky with a backyard telescope often feel a sense of disappointment upon first locating a famous galaxy or nebula. Where are the beautiful colors they have seen in photographs? "The colors of galaxies cannot be seen directly by the human eye, even through the largest existing telescopes," notes astronomer and science writer Timothy Ferris, "for their light is too faint to stimulate the color receptors of the retina." This has caused some persons to conclude that the beautiful colors seen in astronomical photos are fakes, simply added in the processing somehow. This is not the case, however. "The colors themselves are real," writes Ferris, "and the photographs represent the best efforts of astronomers to reproduce them accurately."

In his book Galaxies, Ferris explains that the photos of faint distant objects, such as galaxies or most nebula, "are time exposures obtained by aiming a telescope at a galaxy and exposing a photographic plate for as long as several hours while starlight seeps into the photographic emulsion. During this time a driving mechanism compensates for the earth's rotation and keeps the telescope trained on the galaxy, while the astronomer, or in some cases an automatic guiding system, makes minute corrections."

Picture Credits:
The Cone Nebula in NGC 2264 cluster: Courtesy of Anglo-Australian Observatory, photograph by David Malin
Orion Nebula: C. R. O'Dell/Rice University/NASA photo
Cartwheel galaxy: Kirk Borne (ST Scl), and NASA
Cat's Eye Nebula: J. P. Harrington and K. J. Borkowski (University of Maryland), and NASA

Appeared in Awake! January 22, 1996