Telescopes: bigger is better
October 23, 2015
In the 17th century, Galileo Galilei observed the stars with optical telescopes that had only up to about 30fold magnification - still, he was able to discover the four largest moons of Jupiter.
"I looked through one of these small devices in a museum in Florence," says Klaus Hodapp, astronomer at the University of Hawaii. "The image quality is horrible. It's hard to believe Galilei saw anything at all with that thing."
Nowadays, astronomers watch processes much further away - in other galaxies even. They rely on more sophisticated and larger telescopes than the one that Galilei started with all that time ago.
Plan to go big
The larger a telescope is, the more powerful it is, says Rolf-Peter Kudritzki. Like Hodapp he emigrated from Germany to Hawaii to work at the Institute of Astronomy at the University of Hawaii.
"Telescopes catch light waves - just like an umbrella that has been turned upside down collects rain drops," Kudritzki explains. "The bigger a telescope is, the more light it can catch and the better the sharpness of the image becomes."
Larger telescopes enable astronomers to observe fainter objects.
"We can look deeper into the universe and that means, also further into the past - because light takes a long time to reach us from objects far away," Kudritzki says.
Astronomers hope to learn more about the beginnings of our universe. About the black hole in the center of our galaxy, for example. Was it there before the galaxy itself was born? Or did the galaxy come first?
Larger telescopes also enable astronomers to observe and analyze planets around distant stars - and maybe find another Earth out there.
The biggest optical telescopes right now have mirrors that measure about 10 meters, 32 feet. But a new device that will be built in Hawaii is going to exceed that number by far. The mirror of the new optical telescope will be 30 meters - almost 100 feet - in diameter. That's why it is simply called the thirty-meter telescope, or TMT.
Meanwhile, in Chile's Atacama desert, engineers are busy building the European Extremely Large Telescope. Its mirror will be even larger: 39.3 meters, over 130 feet.
An astronomer's village
The TMT will be built on Mauna Kea, Hawaii's highest volcano on Big Island. The mountain is 4,200 meter tall, almost 14,000 feet. The road up there is a challenge - it is steep and large parts are unpaved.
"We tend to joke that if an instrument makes it up Mauna Kea, then it can withstand a rocket launch," Klaus Hodapp says and laughs.
When reaching the top of the mountain, the road gets much better. Dust in the air worsens the image quality, that's why the road was paved here.
On the plateau on top, large buildings with white or metallic domes twinkle in the sunlight; inside are the telescopes. Other devices look like huge satellite dishes. In total 13 telescopes look - or listen - deep into the northern-hemisphere sky.
Paved roads lead to each of the telescopes. It looks like a small but spacious village.
The TMT will be built on an open flat area on the northern plateau. There is not much to be seen yet, apart from a few construction vehicles.
Mauna Kea is famous among astronomers for its fantastic views of the universe. According to Kudritzki, it is the best place in the world to observe the Northern hemisphere.
"Hawaii lies in the middle of the ocean like a tiny spot on a table top. Winds called jet streams pass the flat ocean and Mauna Kea more or less unhindered."
That's why only few turbulences in the atmosphere occur. Such turbulences interfere with astronomical observations.
Many small mirrors
Building large powerful telescopes has been an astronomers' dream for decades. But it is easier said than done. Building a mirror with a diameter of more than 8.4 meters - like the ones in the Large Binocular Telescope in Arizona - seemed to be impossible.
"The glass breaks as soon as the mirror gets too warm," says Günther Hasinger, director of the Institute of astronomy at the University of Hawaii.
Then engineers developed segmented mirrors: an array of smaller mirrors that are adjusted to each other to form one large mirror area.
The 30-meter telescope will be made out of 492 single hexagonal segments.
Adaptive optics makes the pictures even sharper. It is a technology that has been used on a broad scale since the 1990s.
Computers control the mirror segments of a telescope and correct in real time the distortion caused by the turbulence of the Earth's atmosphere. All modern telescopes work in this way.
Enduring protests
The thirty-meter telescope was supposed to start its research work in 2024. But that's already cutting it fine. Protests against the new telescope have halted construction work several times.
Mauna Kea is sacred for native Hawaiians. Some of them oppose to the construction of another telescope on their holy mountain.
One of the opponents is Pua Case. She says she will never stop fighting against that "thing" - as she puts it.
"You got 13 telescopes on our mountain, you have leveled the top of the mountain, you have taken the entire top of our mountain," she says. "To demand for one more is an insult to our very core."
The building surrounding the TMT will be 18 storeys high. Opponents say it will be clearly seen from the towns on Big Island.
"We are not standing here against science or astronomy, we are saying: 18 storeys on our mountain is not right," Pua case says. "We look up at our mountain and see it [the telescope] every day for the rest of our lives and our children and children's children, too."
On Wednesday, the University of Hawaii announced that one of the older British-made telescopes on Mauna Kea would be removed to comply with state regulation that 25 percent of the older telescopes must be removed