A thousand nebulae



I am finally reading The Age of Wonder by Richard Holmes. It is wonderful. SPACE! Can you imagine discovering the infinite beauty of space, beyond what the naked eye can see? And really, everyone can do that. I want a telescope! My dad used to have a great big red one and I only remember looking through it once when I was wee, at the moon, and also at the Little Dipper, which I didn’t know about yet so I yelled out that I found something that looked like a hand mirror, or a squirrel with a nut, or something.

I am learning about William Herschel, a self-taught astronomer who, with the help of his sister Caroline, revolutionized how we look at space and what we see when we get there. He found Uranus (and cannot be entirely blamed for the name)!

“Only thirty nebulae were known in the 1740s, at the time of Herschel’s birth. By the time Herschel began to study them in the mid-1770s, Charles Messier in Paris had catalogued just under a hundred. Within a decade, by the mid-1780s, Herschel would have increased this tenfold, to over a thousand nebulae. No one really knew their composition, origins, or distance. In general they were thought to be a few loose clouds of gas, hanging static in the Milky Way, some loose flotsam of God’s creation, and of little cosmological significance. Herschel suspected that they were star clusters at immense distances, whose composition might hold a clue to an entirely new kind of universe” (p. 88).

He got his big break in December 1779, when he had his seven-foot reflector in the street in front of his house to observe the moon. A “gentleman” stopped to see what he was doing, and Herschel let him take a peek. “Next morning,” he wrote, “the gentleman, who proved to be Dr Watson, junior (now Sir William), called at my house to thank me for my civility in showing him the moon” (p. 93). Ha! Dr Watson introduced him into the scientific community in Bath.

Caroline was responsible for taking notes of her brother’s observations, which consisted of vertical “sweeps” of the sky with his hand-made telescopes. She “gave the term ‘sweeping’ a certain domestic familiarity, so that in her letters she sometimes implies she is a sort of celestial housekeeper” (p. 116). Lovely.

That – sweeping, star dust – reminds me of two really terrific articles that were in the Dust Issue of the Best Magazine in the World, Cabinet. In one interview, Dorian Sagan recalls his wonderful pop, Carl, and how he liked to say we are all “star-stuff”: “Sly and the Family Stone were on the same cosmic track as my father when they sang, ‘Everybody is a Star.'” That song is so good. It makes me sad.

There is also an interview with nuclear physicist Jean Duprat by Brian Dillon. Duprat studies micrometeorites and cosmic dust. In ANTARCTICA. And basically, most of the dust in uninhabited Antarctica is space dust. From comets. Magic! That dust shows us that matter came from the stars.

“If you look at the nuclei out of which the solar system is formed—leaving aside hydrogen and helium, which were made during the Big Bang—but if you look at the heavier elements, then everything on earth, including us, is stardust. There is no way to synthesize nuclei—at least in an efficient way—within the solar system itself; you can have a few nuclear reactions, but it’s nothing in terms of production of matter. all the matter has been synthesized in the very heart of stars before our solar system formed.”

The thin galaxy above comes from the wonderful NASA Astronomy Photo of the Day site, as does the following text. I love NASA.

NGC 4452: An Extremely Thin Galaxy
Credit: ESAHubbleNASA

Explanation: Why is there a line segment on the sky? In one of the more precise alignments known in the universe, what is pictured above is actually a disk galaxy being seen almost perfectly edge on. The image from theHubble Space Telescope is a spectacular visual reminder of just how thin disk galaxies can be. NGC 4452, a galaxy in the nearby Virgo Cluster of Galaxies, is so thin that it is actually difficult to determine what type of disk galaxy it is. Its lack of a visible dust lane indicates that it is a low-dust lenticular galaxy, although it is still possible that a view from on top would reveal spiral structure. The unusual stellar line segment spans about 35,000light years from end to end. Near NGC 4452‘s center is a slight bulge of stars, while hundreds of background galaxies are visible far in the distance. Galaxies that appear this thin are rare mostly because our Earth must reside (nearly) in the extrapolated planes of their thin galactic disks. Galaxies that actually are this thin are relatively common — for example our own Milky Way Galaxy is thought to be about this thin.


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