SCOTT SIMON, HOST:
There have been a lot of news stories this week about the Hubble Space Telescope and its 25th anniversary. But if you wondered who this guy Hubble was, why the telescope was named after him, NPR science correspondent Joe Palca provides the answer as part of his series Joe's Big Idea.
JOE PALCA, BYLINE: The reason Edwin Hubble got a telescope named after him is he made two of the most important astronomical discoveries of all time. Back in the 1920s, he was working on the largest telescope in the world - the 100-inch Hooker telescope on Mount Wilson, just outside Los Angeles. On a chilly evening this past February, I climbed up to the dome of that telescope with operator Nik Arkimovich. I asked him to show me where Hubble would sit when he was using the telescope. Arkimovich points to a platform near the top of the telescope frame.
NIK ARKIMOVICH: So Hubble gets to sit on a chair at the Newtonian focus right there.
PALCA: What does he do up there?
ARKIMOVICH: He's making adjustments to the guiding.
PALCA: Motors and gears guide the telescope so it can stay pointed at a star as it moves across the sky. But astronomers need to make small tweaks throughout the night.
ARKIMOVICH: He's got an eyepiece with crosshairs on it, and he's got a paddle that allows him to make minor adjustments. And his job is to keep the star in the crosshairs for maybe eight hours.
JOHN MULCHAEY: It's certainly much, much easier today.
PALCA: That's John Mulchaey, acting director of the Carnegie Observatories where Hubble worked during the day.
MULCHAEY: Now we sit in control rooms. The telescopes operate brilliantly on their own, so we don't have to actually worry about tracking and things like this.
PALCA: Today, telescopes like the Hubble Space Telescope use digital cameras to catch the light from stars and other celestial objects. Mulchaey says in Hubble's day, they used glass plates.
MULCHAEY: At the focus of the telescope, you would put a glass plate that has an emulsion layer on it that actually is sensitive to light.
PALCA: At the end of an observing run, the plates would be developed, much like the film in a camera.
MULCHAEY: A good portion of astronomy history is stored in this room and rooms here.
PALCA: Here is the basement of the Carnegie Observatories building in Pasadena. A century's worth of glass plates are stored here.
MULCHAEY: So why don't we go take a look at Hubble's famous Andromeda plates?
PALCA: The plates are famous for a reason. They completely changed our view of the universe.
MULCHAEY: All right, so this is a rare treat for you because this plate doesn't see the light of day for very often.
PALCA: To the untrained eye, there's nothing terribly remarkable about the plate, but Mulchaey says what it represents is the most important discovery in astronomy since Galileo. The plate shows the spiral shape of the Andromeda galaxy - Hubble was looking for exploding stars in Andromeda called novas. Hubble marked these on the plate with the letter N.
MULCHAEY: The really interesting thing here is there's one where it's an N crossed and it's crossed out in red. And he's changed the N to VAR with an exclamation point.
PALCA: Hubble realized this wasn't a nova. The VAR stands for a variable star known as a Cepheid variable. It's a kind of star that allows you to make an accurate determination of how far away something is. This Cepheid variable showed the Andromeda galaxy wasn't a part of our galaxy at all. It was its own galaxy, way, way out there. At the time, most people thought the Milky Way was it - the only galaxy there was.
MULCHAEY: And what this really showed was that wait, there's other galaxies out there. The universe is much, much bigger than anybody realizes.
PALCA: Another blow to our human conceit that we are the center of the universe. Hubble went on to show the universe was expanding; a discovery so astonishing that Hubble had a hard time believing it himself. If Hubble made such important discoveries with century-old equipment, makes you wonder what he might've uncovered with the Hubble Space Telescope. Joe Palca, NPR News.
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