How Barnard plaque at Perkins came to be


By Tom Burns - Stargazing



On the front of Perkins Observatory is a plaque honoring E.E. Barnard. Some unremembered artist carved his name into Italian marble inlaid with gold leaf.

He joins such notables as Tycho Brahe, Nicolaus Copernicus, and Johannes Kepler there. Here is the story of that plaque.

Just a bit over a century ago, our view of the universe was quite different than it is today.

Jupiter had four moons, a number that had not changed since Galileo discovered them in 1609.

The stars of our Milky Way galaxy moved with respect to each other, but their movement was slow and unremarkable.

Astronomers heatedly debated the nature of the “spiral nebulae,” which we now called galaxies. Were they in our Milky Way galaxy and perhaps stars in the process of formation? Or were they galaxies in their own right, “island universes” for billions of stars?

Into that scene intruded an amateur astronomer, E. E. Barnard.

Barnard was born in 1857. The death of his father three months before his birth forced his family into poverty.

When he was nine years old, his family’s dire circumstances led him to become an assistant in a photography studio. The job was fortunate, even though it did not seem so at the time.

While other children were getting formal educations, he was working. However, his lifelong interest in photography later bore fruit in his astronomical endeavors.

By the time he was 18, his budding interest in astronomy had led him to make a ruinously expensive purchase. Just five years later, he discovered two comets with his five-inch refracting telescope and a third in 1882.

His interest in comets was not purely scientific. He got married in 1861. He needed money.

He was responding to a challenge by a patent-medicine huckster and philanthropist named Hulbert Harrington Warner, who had offered $200 for the discovery of every new comet.

He eventually discovered five comets and used the $1,000 reward to build a house for his new wife and himself.

His cometary adventures attracted the attention of other amateur astronomers in Nashville, Tennessee. They raised enough money to pay for his enrollment at Vanderbilt University. At last, he was to get a formal education.

But Barnard never graduated. Instead, he joined the staff at Lick Observatory in California.

In 1892, he made two critical discoveries. His observations of a nova, a star that varies abruptly in brightness, led him to conclude that stellar explosions caused such eruptions.

In that same year, he discovered the fifth moon of Jupiter, which he dubbed Amalthea. It was the first moon of Jupiter discovered since Galileo’s discovery of four moons in 1609.

Amalthea is also the last moon discovered with just the eye. Astronomers have found all the rest of Jupiter’s 69 moons using photography or, lately, digital imaging.

Perhaps Barnard’s most outstanding contribution to modern astronomy was the application of his early interest in photography. Working at the Yerkes Observatory, he photographed the Milky Way, not an easy task at the time.

Using those photographs, he generated a list of dark nebulae, dark regions of the Milky Way that appear to contain no stars. Amateur and professional astronomers still use his list to this day.

I will never forget my first observation of Barnard 33, the Horsehead Nebula, as a dark notch superimposed on a bright background nebula.

His detailed inspection of those dark nebulae led him to conclude that they consisted of dark clouds of dust and gas blocking the light from background stars.

In 1916, near the end of his career, Barnard discovered a tiny red-dwarf star. It turned out to be the fourth closest star to our sun and Earth. Only the three stars of the Alpha Centauri system are closer.

Barnard’s Star, as it is called, is also the fastest-moving star ever recorded. It moves through space in Earth’s general direction at a startling 88.6 miles per second. At that rate, it will reach its closest point, 3.75 light-years away, in 11,800 CE.

The most interesting of Barnard’s discoveries to amateur stargazers came in 1884 when he was still using his little refractor to observe the sky. Barnard’s Galaxy is a small dwarf galaxy in a cluster of galaxies called the Local Group.

The sun is one of 300 billion in the Milky Way galaxy. The Milky Way is an average galaxy, one of trillions in the universe.

Galaxies are clumped together in clusters, some of which have thousands of member galaxies and are hundreds of millions of light-years in diameter. (A light-year equals about 6 trillion miles.)

The Milky Way is one galaxy in a cluster called the Local Group. With only 40 or so galactic members, the Local Group is a scant five million light-years in diameter.

Most of the Local Group’s area consists of the void between galaxies. The distance from the Milky Way to the closest large galaxy is over 20 times the width of the Milky Way.

Only two other galaxies of the Local Group are similar in shape and size to the Milky Way, a spiral galaxy.

A much smaller type, called the dwarf galaxy, is far more numerous. Dozens of dwarf galaxies populate our galactic cluster, yet in total, they comprise less than 1/10 of the matter in the Local Group.

The two most prominent dwarf galaxies in our local group are the Large and Small Magellanic Clouds.

As satellite galaxies of the Milky Way, the Magellanic Clouds are easily visible to the unaided eye. Unfortunately, they are easily visible to the unaided eye for Southern-Hemisphere observers but not for us Northern Hemispherians.

Two galaxies of our Local Group illustrate the contrast between the spirals and dwarves.

The first is our very own Milky Way. Just after dark from dark, rural skies, you can see it spread across the sky as a hazy band of light. In large binoculars, you can see that countless stars make up the milky glow. Its size is typical of the spiral galaxies, about 100,000 light-years across and about 10,000 light-years thick.

If you could get outside the Milky Way and observe it “face-on,” you would see a central hub, dense with stars, and thin spiral arms that arc from the hub like a child’s pinwheel.

Like all large galaxies, the Milky Way is also full of dust and gas that either hasn’t formed into stars or are the remnants of stars that have lived out their lives and died, spewing back part of their substance into the interstellar medium.

The most accessible dwarf galaxy to observe from our earthly vantage is Barnard’s Galaxy. Look south, up and to the left of the teapot-shaped constellation Sagittarius. Center the small triangle of stars, marked as “55” on most star maps. Then sweep upward and to the left until you see a faint, elongated splotch with no defined spiral structure.

Barnard’s Galaxy is about 1.7 million light-years away, roughly 3/4 of the distance to the Andromeda Galaxy, the closest spiral galaxy to the Milky Way.

In long-exposure photographs, Barnard’s galaxy breaks up into sparsely packed stars. (You can see right through it in a long-exposure image.) Its stellar material amounts to no more than 50 million suns, a pathetic 1/6,000 of the “starstuff” in the Milky Way. And it’s tiny by the standards of the Milky Way — only 10,000 light-years in diameter, about 1/10 the width of the Milky Way.

At one time, Barnard’s Galaxy probably looked like a miniature version of our spiral Milky Way. However, close gravitational encounters with other Local-Group galaxies have stripped it of stars and bent it out of shape.

Because of its small size and low mass, Barnard’s doesn’t have the gravity to sweep up much gas and dust from intergalactic space. Galaxies need such cosmic debris to make new stars and keep themselves going as old stars die. Barnard’s Galaxy does indeed have some new stars in it, but it will never be a prolific “star-maker” like the Milky Way and other large spirals.

Astronomy has a way of washing away human pride. Earth is not the center of the solar system. The sun is not at the center of the Milky Way.

The Milky Way is not at the center of its cluster of galaxies. Even on the relatively small scale of our Local Group, our beloved planet is a speck of dust lost in the cosmic void replete with six trillion galaxies. Most of those galaxies are clumped together in clusters far more extensive than our puny Local Group.

Gravity binds the few dozen galaxies of our Local Group together. Despite their enormous distances from each other, they move together at incomprehensible velocities through a universe vast even by the standard they set.

A pioneering cadre of astronomers from the turn of the nineteenth century to the twentieth began the process of showing us our place in the universe.

One of them was E. E. Barnard. A marble plaque inlaid with gold leaf seems small recompense for the gifts he gave us.

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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.