Love of planetary nebula led to M27 nickname


By Tom Burns - Stargazing



Back in my graduate-student days (a long, long time ago), I was not a very attentive student. Perkins Observatory was mainly, but not entirely, to blame.

I often set up my home-built telescope in the parking lot and observed the night away. Members of the Columbus Astronomical Society often joined me, or rather, I joined them. I was the new kid on the block.

Technically, the club had an informal arrangement with Ohio State University’s Astronomy Department, which ran the place at that time, to use the facility.

However, Ohio State astronomy graduate students were often collecting data with the giant telescope in the dome or reading in the spooky haunts of the library. Most of them kept the doors firmly locked to keep out amateur riffraff like us.

There was, thank goodness, one notable exception. I’ll call him Doug because, in fact, that is his real name.

He was not a graduate student. Instead, he was a lowly member of the Columbus Astronomical Society. But he knew his way around a telescope. As a result, one of the OSU astronomers had hired him to do research grunt work alone in the dark, echoic dome.

All-night observing can be a lonely preoccupation. At first, Doug let me in to use the bathroom, then to talk for long hours, and finally to use the observatory telescope on my own as he snoozed on the library floor downstairs.

Among the other members of the astronomy club, Doug had the unusual nickname of M27.

He had “borrowed” from OSU an antique telescope built in the latter part of the 19th century. The telescope was a thing of beauty — all brass and glass and polished wood. It had been lovingly handcrafted by Alvan Clark, the greatest of all lens makers of the 19th century.

“The Clark,” as he lovingly referred to it, was tiny by the standards of modern amateur telescopes. Only a limited number of objects looked good when viewed through it.

The telescope was born to look at planets. The rings of Saturn and the cloud bands on Jupiter were a sight to behold. On the rare occasions that Doug wandered away from the Clark, I would quickly feast my eyes on them.

Oddly, Doug never observed the planets. Again and again, he returned to a single object with unflagging astronomical obsession.

If he could get an audience, he always swung the telescope to M27, a planetary nebula in the obscure constellation Vulpecula, the “Little Fox.”

So, Doug invariably showed beginners like me that beautiful little cloudy patch in his “borrowed” ‘scope. M27 didn’t look like much in a 100-year-old refractor, and some of us became convinced that it was the only astronomical object Doug knew how to find.

No one who knew him ever complained, though. Doug owned an extensive collection of firearms, including M-1 and M-16 rifles and an ever-changing array of Civil-War muskets. Doug “borrowed” bricks of slightly radioactive lead from Ohio State’s Van de Graaff generator to pour his own musket balls.

Occasionally, I could hear musket fire outside as I drowsily used the Perkins telescope. As the sound echoed loudly in the dome at 3 a.m., I was startled magically awake. The combination of Doug’s gun hobby and his somewhat unstable character inspired a high level of tremulous respect.

In any case, I learned to find M27 under Doug’s tutelage. First, he’d have to find Vulpecula, which was no easy task. It is one of the faintest and least conspicuous constellations in the sky.

The best way to locate Vulpecula is to look for the constellation Lyra, the Lyre, which is high in the east once the sky has gotten good and dark (around 10 p.m.).

Directly to the east of Lyra is Cygnus, the Swan, which will look like a cross lying on its side. To the left of the star at the base of the cross is a flat triangle of stars — that’s Vulpecula.

M27 is just below the left star in the triangle. You can also find it by looking for the “point” star in the small constellation Sagitta, the Arrow, and moving up. It will look like a small, fuzzy star in binoculars. In a telescope larger than the Clark, it looks like a slightly larger fuzzy thing — but spectacularly so.

In a small telescope at low power, M27 looks like a small grayish disk of light.

Early users of telescopes noted that the small class of objects like M27 looked a bit like the planets Neptune and Uranus. They called them planetary nebulae based on that superficial similarity of appearance.

Some even argued that they might be planets that were in the process of forming. They were wrong about that, of course.

Planetary nebulae like M27 turn out to be shells of gas that are rapidly expanding from sun-like stars in the process of dying.

Here’s what happens: Stars like our own sun burn so brightly because they fuse their hydrogen into helium. That doesn’t sound like much, but it’s essentially the same process that a hydrogen bomb uses to produce its thermonuclear reaction.

When stars only a bit larger than our sun begins to run out of hydrogen, they swell up to 1,000 times their original size. Those so-called “red giant” stars then collapse to a highly dense sphere, called a “white dwarf,” only about the size of a small planet like Earth. As they collapse, they eject their outer shell, about 10 or 20 percent of their substance, into space.

In a trillion years or so, the white dwarf eventually fades to black, a light-and-heat-giving star no more. The outer shell of gas will continue to expand. In time, it becomes too faint and spread out for us to see.

M27 is a relatively close 1,300 light-years from Earth. (A light-year is about 6 trillion miles.) If that sounds like a long way, remember that our galaxy of 300 billion stars is about 100,000 light-years in diameter.

M27 is expanding at around 19 miles per second. It has been doing so since the explosive expansion of its central star about 50,000 years ago.

The expanding shell of gas is about one and a half light-years, or about 9 trillion miles, in diameter. Our solar system is only about seven and a half billion miles across — the diameter of dwarf-planet Pluto’s orbit.

If M27’s central star had been our sun, the initial expansion of the star into a red giant would have burned Earth to a crisp. The shell of hot gases would by now have reached far past the orbit of Pluto.

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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.