Gaia - building on the legacy of Hipparcos
Transcript of video
[ Narrator ]
When our ancestors first looked up into the night sky they must have wondered at the band of stars and diffuse light crossing the heavens above them. It probably looked like a distant constellation, but we now know that our planet Earth is part of this constellation, known as the Milky Way. But it is only through the science of astrometry, the measuring of distances and movements of stars, that we are able to map our place in our Galaxy and by extension in the Universe. The Greek astronomer Hipparchus was the first to map the Milky Way.
[ Giuseppe Sarri ]
"Hipparchus, the Greek astronomer, 2000 years ago, made the first catalogue of stars; which was an important catalogue, which was there up to the Middle Ages. And he did it with the naked eyes, therefore it was really impressive. He could go to magnitude six. And then, with the development of telescopes, with Galileo and the first telescope, we could - astronomers could measure more stars and with higher precision."
[ Narrator ]
While Hipparchus mapped one thousand objects and charted them on the sky, by the end of the 16th Century another astronomer, Tycho Brahe, created a catalogue of a thousand stars with a factor of precision a hundred times better than what was done by Hipparchus. More recently, in 1967 a Frenchman called Pierre Lacroûte revived astrometry with a proposal to place a telescope on a satellite above the Earth's atmosphere. In 1980, realising the importance to science of this idea, ESA decided to endorse this project which would eventually be called Hipparcos.
[ Pierre Lacroûte - English voice-over ]
"I really thought that there was the possibility of doing something in space with astrometry. We worked hard to imagine what methods to use. And then the Space Agency took up the project and then after the work of many astronomers and engineers it became the highly successful Hipparcos project."
[ Narrator ]
The launch of Hipparcos in 1989 marked a major step forward in astrometry, one that produced results about ten thousand times more accurate than those of Tycho Brahe four hundred years before. By placing a telescope in space ESA was able to measure the position of stars without the distortion of the Earth's atmosphere, which had previously deformed measurements taken from the surface of Earth. Four years after its launch, Hipparcos exceeded all expectations by producing a million million bits of information, which after being received by ground stations in Germany, Australia and the United States, went into the biggest computation in the history of astronomy to produce the Hipparcos and Tycho catalogues. These catalogues of measurements pinpointed the position of more than one hundred thousand stars to high precision and more than one million stars to lesser precision and, as predicted, became the reference for astronomers for the last fifteen years.
But it is now time for ESA's new astronomy mission Gaia to build on the legacy. By harnessing advances in technology to build the largest CCD optical plane and the most stable casing to date, Gaia will be able to see ten thousand times as many objects as Hipparcos. It will produce the most extensive and accurate catalogue of the objects in our Milky Way, a hundred times more accurate and all-encompassing than that produced by Hipparcos. This will allow astronomers to create a new map that will massively improve our understanding of the Milky Way, how it has evolved in the past and how it will evolve in the future.
[Editor's note: this video was originally published on ESA's videos for professionals website.]