Astronomy: Quasars and other mysteries


Tom Burns - Stargazing



My mother often told me that for everything we take with us, we have to leave something behind. I never really understood what she meant until one spring night, long ago, when I had a staring match with a faint point of light.

I had recently started graduate school in English. Teaching the infamous Freshman Composition course paid my tuition and little else. However, over a year’s time, I managed to save enough to pay for the parts to assemble a really big telescope.

I cranked out the telescope in a single frenzied weekend, and by Monday night, I was at my usual observing location at Perkins Observatory. I was observing that night with my astronomical mentor Biff Smooter.

After we observed a few bright objects, I decided to test the capabilities of the ‘scope and its mirror by bagging a quasar, or quasi-stellar object.

Up to that point, the farthest objects I had observed were the galaxies, whirlpools of hundreds of billions stars that were millions of light-years away. (“Remember,” as Biff often said, “a single light-year is equal to about six trillion miles, so we’re talkin’ ‘bout a considerable distance here.”)

The quasars are billions of light years away and are among the most distant objects we know of in the universe. That was exciting enough, but there was more.

Because quasars are so distant, it takes a very long time for their light to get to us. A light-year is defined as the distance that light travels in one year.

That means that the light from quasars takes billions of years to reach Earth. My new ‘scope would become a time machine that would let me see the universe as it was a very long ago, as near as my ‘scope could reach to the beginning of time itself.

Biff wanted to find our target quasar, but I wouldn’t let him. This one would belong to me.

The quasar in question has the unimaginative name of 3C 273.

I started by finding the constellation Virgo, the Virgin, which sits directly south in May.

I knew 3C 273 was located up and to the right of the star Porrima at a spot marked on most detailed star charts.

But I also knew it would be very faint (distant objects usually are). After a grueling hour of searching, I found it.

It was a faint speck, even in my comparatively large telescope. I was looking at an object producing four trillion times more visible light than our daystar, the sun. And it looked like a speck. The name “quasi-stellar object” made sense now. 3C 273 looked just like a faint star.

Biff explained that its appearance is deceiving. This quasar is flying away from us at about 28,000 miles per second, about 16 percent of the speed of light.

Given its distance of 2.4 billion light years (3 billion times 6 trillion miles), it had to be at least four trillion times brighter than our sun for us to see it at all.

But the quasar is minuscule in volume compared to the galaxies. I wondered aloud how much stuff could be crammed into so small a space.

Biff reminded me that galaxies have at their centers enormous black holes. Those bottomless pits of gravitation each suck the substance of millions stars into themselves.

As that primordial stellar matter spirals into the black holes at speeds approaching that of light, huge amounts of energy are released. It was that giant conflagration that I saw 2.4 billion years later as a distant speck of light.

The Milky Way’s black hole is a puny thing indeed compared to the black hole that fuels 3C 273.

Our entire galaxy fits its black hole and its surrounding 300 billion stars into a spacious disc 100,000 light-years in diameter. The black hole that fuels 3C 273 manages to fit the mass of around 800 billion suns into a space perhaps only 7,500 light-years across.

As it turns out, 3C 273 is surrounded by an egg-shaped, elliptical galaxy of enormous size with trillions, not billions, of stars. Yet the galaxy that surrounds 3C 273 is far fainter than the light cascading from its central black hole.

In the interceding 2.4 billion years, 3C 273 may very well have settled down into a tranquil galaxy like our Milky Way.

But I realized with a flash of melancholy that I would never really know.

That information, in the form of light, would take another 2.4 billion years to get here. I would be long gone. Humanity would be long gone. Perhaps our Earth and even our sun would no longer possess those qualities that sustain life on our planet.

I stared at that tiny point of light, and it seemed to stare back, challenging me.

At last I knew my place in that universe. Tiny human that I was, I had reached out to experience a small part of the cosmos.

But I also realized just how small I was, how vast and incomprehensible the universe. 3C 273 was no speck. I was the speck.

That quasar was the farthest object I had observed. It is still the farthest. Yet that faint speck of light is but 17 percent of the distance to the edge of the observable universe and hence 17 percent of the distance to the beginning of time.

My self-possessed joy of youth was burned up in the quasar’s raging fire.

But I knew a greater joy — one of belonging to, of sharing in, the life of the much larger universe around me.

My mother was right in a way I could never explain to her. For everything we take with us, we must leave something behind. I left behind my youth. I gained the Universe.

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Tom Burns

Stargazing

Tom Burns is director of the Perkins Observatory in Delaware.

Tom Burns is director of the Perkins Observatory in Delaware.