Shimmering speck of light has story to tell


By Tom Burns - Stargazing



My mother was something of a neat freak. When I went away to college, she tossed out my old, collectible erector set and all of my comic books. I sometimes muse about the value of my pristine collection of Metal Men comics, which long ago became landfill in a trash dump outside of Youngstown, Ohio.

When we went on vacation, one simple rule was strictly enforced — pack light.

She always eyed my pile of take-alongs with miserly dismay. “For everything you take with you, you have to leave something behind,” she would say.

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 was observing with my astronomical mentor Biff Smooter. Over many months, he showed me many an astronomical object and patiently described its distance, sizes, makeup and significance.

That night we were going to bag a quasar.

Up to that moment, the farthest objects we had observed that night were the galaxies of the Virgo Cluster, whirlpools and ellipsoids of hundreds of billion stars that were millions of light-years away. (“Remember,” Biff said as he spat a juicer of chewing tobacco, “one light-year is about 6 trillion miles, so we’re talking about 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.

In the 1950s, astronomers began to identify sources of strong radio-wave emissions in the sky. They look for all the world like stars, but a study of their spectrum reveals that they are nothing like stars. Astronomers thus gave them the name quasi-stellar radio source, quasar for short.

Because quasars are so distant, it takes a very long time for their light to get here. 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 ’scope would become a time machine that would let me see the universe as it was very long ago, as near as my ’scope could reach to the beginning of time itself.

Biff had observed that particular quasar many times before, so he wanted to speed things up and find it himself.

But I wouldn’t let him. This one was mine. The quasar we were going to find had the rather unimaginative name of 3C 273. It was the first quasar discovered in the late 1950s.

It was one of many such radio sources listed in the Third Cambridge Catalog of Radio Sources, published in 1959. Astronomers soon identified it with a star-like visual counterpart in the sky.

Four years later, astronomer Maarten Schmidt determined that the object was at least a couple of billion light-years away from us. At that distance, 3C 273 was certainly not a star. Only the galaxies were that far away, but no galaxy was visible. All astronomers saw was a remarkably bright star-like object.

I started by finding the constellation Virgo, the Virgin, which sits directly south in late April. It looks like a “Y” tipped slightly to the left. Next, I found Porrima, the star at the intersection of the three strokes of the “Y.”

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

But I also knew it would be very faint (distant objects usually are), and Biff wouldn’t tell me what it looked like. (He was a little miffed that I wouldn’t let him find it for me. Tough.)

So I had to consult a detailed star chart.

I used Wil Tirion’s Sky Atlas 2000 because it plots many faint stars, and I knew I would have trouble distinguishing 3C 273 from the plethora of foreground stars in the area.

After a grueling hour of searching, I found it.

Even in my comparatively large telescope, it was a faint speck. The name “quasi-stellar radio source” made sense now. 3C 273 looked just like a faint star.

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

That tiny dot is four trillion times brighter than our sun. Given its distance of 2.44 billion light-years (2.44 billion times six trillion miles), it had to be at least that luminous for us to see it at all.

But compared to the galaxies, its volume is minuscule.

Our home galaxy, the Milky Way, fits 300 billion stars into a disk 100,000 light-years in diameter. 3C 273 manages to hold the equivalent of a small galaxy in a volume only 7,500 light-years across.

I wondered aloud how much stuff could be crammed into so small a volume.

Biff reminded me that we were looking into the past at a part of the universe in an early stage of its formation.

Perhaps 3C 273 and the hundreds of thousands of other quasars like it were the cores of giant galaxies at the early stages of their development.

Perhaps at their centers were gigantic black holes, areas of such high gravitation that even light cannot escape. The black hole that fuels 3C 273 contains the mass of 900 million suns. Those bottomless pits of gravitation each sucked the substance of millions of stars into themselves.

As that primordial stellar matter spiraled into the black holes at speeds approaching that of light, vast amounts of energy were released. I was seeing that stupendous conflagration 2.44 billion years later as a distant speck of light.

As quasars go, 3C 273 is something of an aberration. Thanks to giant telescopes, astronomers have observed and identified 750,000 quasars. At an average distance of 10 or so billion light-years, most of them are very far away.

Because their light took so long to get to us, we see them when the universe was new, when galaxies first formed out of primordial gas clouds. The fact that astronomers see so many of them in the early universe suggests that quasars are a critical early step in the development of galaxies.

How new? In 2020, Hawaiian astronomers detected a quasar they dubbed Pōniuāʻena at the startling distance of 13.1 billion light-years. The light from Pōniuāʻena started its long journey to Earth as early as 700 million years after the creation of the universe in the Big Bang.

And if you thought the black hole at the center of 3C 273 was huge, imagine Pōniuāʻena’s black hole at 1.5 billion solar masses.

For some unknown reason, 3C 273 is one of the odd exceptions. The quasar is at the core of a galaxy that formed only 2.44 billion years ago.

Its relative youth and proximity to Earth turned out to be a lucky break for amateur astronomers like me. More distant quasars are invisible, even in large amateur telescopes. This shimmering point of faint light is the farthest thing I would ever see in my telescope.

The same conditions turned out to be a lucky break for astronomers as well. Finally, in 2003, the Hubble Space Telescope provided visual verification of the galactic-core theory.

Astronomers blocked the light from the quasar using a small obstruction called an occulting disk. With the brilliance of the quasar quelled, the quasar’s egg-shaped galactic halo came into view.

In the intervening 2.44 billion years, 3C 273’s black hole has probably gathered up all the gas, dust, and stars in its galactic neighborhood. Its home galaxy has settled down into a tranquil collection of 300 billion stars spinning slowly like our Milky Way.

But as I stared at that point of light, so feeble to my eye but so mind-bendingly powerful in my imagination, I realized with a flash of melancholy that I would never really know.

The information about the quasar’s final fate will come in the form of light. That light would take another 2.44 billion years to get here. I would be long gone. Humanity would be long gone. Earth and sun will abide, but we will probably not be here.

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

In the decades that followed, I observed galaxies that were hundreds of millions of miles away. But I have never seen quite so far as I did on that warm spring night.

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. I realized that despite human intelligence’s great potential, the vastness of space and time prevents us from knowing the final fate of that simple point of light.

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

But I knew a greater joy. Humans depend on the belief, perhaps illusory, that our lives have purpose. Even a shimmering speck of light has a story to tell. My purpose, then and now, is to tell those stories.

My mother was right in a way I could never have explained to her. For everything we take with us, we must leave something behind.

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By Tom Burns

Stargazing

Tom Burns is the former director of the Perkins Observatory in Delaware.

Tom Burns is the former director of the Perkins Observatory in Delaware.