Blog #12: William Herschel

William Herschel was born November 15, 1738 in Hanover, although he eventually moved to England and did most of his work there. Over his long career, he catalogued over 800 binary star systems and over 2400 nebulae, discovered a planet and four moons in the solar system, and discovered infrared radiation, as well as making his own telescopes (including one that was the longest in the world for around 50 years) and composing over 20 symphonies.

Herschel's 40-foot telescope

His work with binary star systems is particularly interesting. Many at the time believed that the perceived motion was due to the Earth's rotation around the Sun, rather than the actual motion of the stars that were being observed. Herschel, however, hypothesized that the stars in binary systems did move, orbiting each other because of their mutual gravitational attraction. He later confirmed his hypothesis and continued to discover binary and multiple star systems.

During Herschel's time, probably the only binary systems that could be detected were visual binaries -- systems in which the stars are far enough apart to be visually distinguished. However, pairs of stars that are closer together can sometimes be detected by measuring the Doppler effect on the system as each star moves closer or farther from our point of observation. These are called spectroscopic binaries. A third type of binary star system is the eclipsing binary. If the plane of the stars' orbit is properly aligned with the observer such that the stars eclipse each other as they orbit, this will be observable and will indicate that the stars form a system.

Binary star system

He worked closely with his sister Caroline, who acted as his secretary, recording his descriptions of the objects he saw in the night sky. They must have made a pretty good team, because they tracked the relative positions of pairs of stars for 25 years carefully enough that they were able to determine that the stars were orbiting each other. In fact, the first recorded orbit of a pair of stars actually wasn't completed until 5 years after Herschel died.

For these and his other discoveries, Herschel became quite well known as an astronomer. After discovering a planet and trying to name it after King George III, Herschel was knighted (although I'm curious as to whether he got that honor before or after the name "Uranus" was picked instead). He died at 83, but his son John continued his work and eventually became a prominent astronomer in his own right.

"That's Sir William Herschel to you!" 

Sources: 

http://listverse.com/2011/09/08/top-10-most-important-astronomers/

https://en.wikipedia.org/wiki/William_Herschel

https://en.wikipedia.org/wiki/40-foot_telescope

http://www.space.com/17432-william-herschel.html

https://en.wikipedia.org/wiki/Binary_star

https://upload.wikimedia.org/wikipedia/commons/3/36/William_Herschel01.jpg

https://upload.wikimedia.org/wikipedia/commons/6/62/Herschel_40_foot.jpg

http://www.dailygalaxy.com/.a/6a00d8341bf7f753ef01bb08126160970d-pi