Herschel Space Observatory Lives Up to the Family Name —
Astronomy is about scientific discoveries, and every week our scientists bring us new and richer views of the Universe around us. But astronomy is also about history, and about people. The name “Herschel” provides a good example.
The Herschel Space Observatory has been observing the sky at infra-red wavelengths since shortly after its launch two years ago, on May 14, 2009. But its name has a much longer legacy.
The orbiting observatory is named after Sir William Herschel, a self-taught astronomer who discovered the planet Uranus as well as infra-red light, around two hundred years ago. The Herschel family was an incredibly astronomical one, with William, his sister, Caroline, and his son, John, all playing important roles in the history of astronomy.
Born “Friedrich Wilhelm Herschel” in Germany in 1738, William moved to England at the age of 19, and—after many years spent earning a scanty living as a music teacher and learning astronomy and telescope-making in his spare time—became one of the leading astronomers of his time. He is best known for his discovery of the planet Uranus. Working from his home in Bath, England, in 1781 (the same year that the British army surrendered to the Americans at Yorktown, ending the Revolutionary War), Heschel found the new planet using a telescope he made himself. He gained favor from King George III by trying to name the new planet “George’s Star,” though the name didn’t stick. The king evidently appreciated the flattery, though, because he appointed William “The King’s Astronomer” in 1782—a position that included a substantial annual income.
No longer needing to support himself with music lessons, Herschel was now able to devote full time to science, and in the year 1800 he also discovered infra-red light, which has wavelengths longer than visible light that we can see.
Today, the Herschel Space Observatory is making use of the planet Uranus and observing it in infra-red light. The extensive study of our Sun’s seventh planet means that it is very well understood. Using a combined imaging infra-red spectrometer and imaging photometer (camera), the orbiter regularly observes Uranus so that astronomers can calibrate other measurements against this planet’s well-known brightness.
Professor Bruce Swinyard of University College London a member of the observing team, explains: “Uranus was one of the first objects we observed, being imaged shortly after the lid over the instruments was opened. One of the reasons Uranus is particularly useful is that its spectrum is very smooth and well understood at our wavelengths, making it an ideal standard to compare other measurements to.”
The story doesn’t end with William. His sister, Caroline Herschel, worked closely with him for many years, becoming one of the first female astronomers. She made many discoveries of her own—especially of a number of comets that bear her name. And comets, it turns out, are also a major target for the Herschel Space Observatory.
A case in point: In 2009, as NASA’s Deep Impact spacecraft was flying past Comet Hartley 2, the newly launched Herschel orbiter observed this comet in far-infra-red wavelengths. Measuring the chemical properties of the water ice which makes up much of the comet, the Herschel team found it to be very similar to that of Earth’s oceans. This supports the theory that much of the water in the Earth’s oceans was delivered by comet impacts billions of years ago in the violent, early stages of our Solar System’s history.