You never know what hidden treasures can be uncovered in the archives.

And this was certainly the case at Carnegie Observatories’ collection when research for an article led to the unexpected discovery of a 1917 glass plate showing the first-ever evidence of a planetary system beyond our own Sun.

It all started last year when UCL astrophysicist Dr Jay Farihi contacted Carnegie Observatories’ Director, John Mulchaey, whilst researching an article on planetary systems surrounding white dwarf stars. Farihi was searching for a glass plate that contained a stellar spectrum of van Maanen’s star – a white dwarf discovered by Dutch-American astronomer Adriaan van Maanen.

The 1917 photographic plate spectrum of van Maanen’s star from the Carnegie Observatories’ archive.

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Part of George Greenough’s 1819 geological map of England & Wales, showing modern-day Cumbria (then Cumberland and Westmoreland)

This picture shows part of George Bellas Greenough’s 1819 geological map of England and Wales – the first to comprehensively map what lies beneath England’s countryside. This page shows the counties of Cumberland and Westmoreland (modern Cumbria).

Greenough was a pioneering geologist of the 19th century who left his collections to UCL when he died in 1855. (His name is commemorated in UCL’s Earth Sciences student society, the Greenough Society.)

Some of Greenough’s maps, along with other historic items from UCL’s Geology Collections, were publicly displayed on Friday as part of Earth Sciences week.

Links

• UCL Earth Sciences
• UCL Museums & Collections

High resolution images

• High resolution images of Greenough’s map, and other items from the Geology Collections, can be downloaded from Flickr

Semiconductors are the basis of almost all the electronics we are used to today. Transistors are tiny switches (often microscopic) which govern how electricity flows through a device, thanks to their variable electrical conductivity. Putting many transistors in sequence means the flow of electrons through the circuit can begin to follow logical rules and make calculations – the basis of all computing. Even small devices like smartphones can today contain over a billion transistors squeezed onto the tiny chips inside them.

But electronics existed before semiconductors. The transistor was invented in the late 1940s, and only became widely used in the mid 1950s, a decade after the invention of electronic computers.

Early electronic devices, including the first computers such as Colossus and ENIAC, relied instead on thermionic valves.

A small electronic valve manufactured by Mullard. (This is the same Mullard that endowed UCL’s Mullard Space Science Laboratory). Photo: O. Usher (UCL MAPS)

Dating back to the early 20th century, valves can carry out the same functions as semiconductors do today, acting as switches and diodes. But the principles they work on are totally different – instead of exploiting the quantum properties of semiconductors, valves use brute force: glowing hot filaments that flood the valve with electrons.

This means they are extremely energy-inefficient – the ENIAC computer, with just under 18,000 valves (compare this to over a billion transistors in an iPhone) drew 150 kilowatts of power. A typical oven uses around 2 kW, a modern laptop computer uses less than 0.1 kW.

This high power consumption also means that valves look a lot like another device with a glowing filament, appalling energy efficiency and vast production of waste heat: the filament light bulb. (Like old-style light bulbs, valves also regularly burn out and need to be replaced.)

A selection of larger thermionic valves found in UCL Chemistry. Photo: O. Usher (UCL MAPS)

Valves were widely used for electronic applications in university labs until their relatively sudden obsolescence in the 1950s left unused stocks in store rooms. They still occasionally turn up when cupboards are cleared out – including a large haul of several crates of mint-condition valves recently found in UCL’s Department of Chemistry, pictured here. These are of little use for research today, but they are of great historical interest, not least for restoring and repairing old electronic devices.

Dekatrons (counting tubes) were widely used in early computers including the Harwell Dekatron Computer, which is now at the National Museum of Computing.

For this reason, the valves have been donated to the National Museum of Computing at Bletchley Park.

Tool used to demonstrate electric charges. Credit: O. Usher (UCL MAPS). Acknowledgement: Jim Grozier

When metal objects are given an electric charge, the charge is not evenly spread through it. It collects on the surface, and in particular on parts of the surface which are curved.

This object from the collections of the Department of Physics & Astronomy is a historic teaching device that would have been used to demonstrate this phenomenon in times past.

Sitting atop an insulating stand, the device would be charged up and retain the charge long enough for a lecturer to carry out a demonstration. Using a small square of metal on an insulating handle, attached to an electroscope, the demonstrator would be able to show that the charge was concentrated on the sharply curved area on the right hand side in this photo.

Photo credit: O. Usher (UCL MAPS). Acknowledgement: Jim Grozier

Links

• UCL Physics & Astronomy
• UCL Museums & Collections

High resolution images

• Download image in full resolution
• View image on Flickr