Spectroscopy and The Discovery of Helium – Astronotes

May 23, 2019 - Comment

To observe on from final week’s put up on grid computing in our collection on the technological purposes of astronomy to society now we have an article on spectroscopy and the invention of a brand new factor within the cosmos – helium – by Armagh Observatory and Planetarium’s Michael Burton. He’s our Director and earlier


To observe on from final week’s put up on grid computing in our collection on the technological purposes of astronomy to society now we have an article on spectroscopy and the invention of a brand new factor within the cosmos – helium – by Armagh Observatory and Planetarium’s Michael Burton. He’s our Director and earlier than coming to Armagh was the Director of Instructing on the Faculty of Physics within the College of New South Wales in Australia. He’s additionally a member of the Worldwide Astronomical Union and President of the IAU’s Division B (“Services, Expertise, Information Science”).

A wholly new factor was found by astronomers within the
19th century when making use of the then nascent diagnostic device of
spectroscopy to the exploration of the cosmos. 
Helium, unknown on the Earth at the moment, was found in a spectrum
taken of the sunshine from the Solar.

The 2 most ample parts within the Universe are the 2
lightest parts, hydrogen and helium. 
They make up the overwhelming majority of the mass of the observable universe,
dwarfing the contribution from all heavier parts mixed by a large
margin.  Helium is the second lightest,
in addition to the second most ample factor. 
It makes up practically 1 / 4 of the mass contained within the stars.  Stars are certainly helium factories.  They spend most of their lives creating
helium from the hydrogen of their cores, via the method of nuclear
fusion.  But Helium was unknown as an
factor till the center of the 19th century.  It was solely found by probability via the applying
of the brand new device of spectroscopy to observations of the sunshine from the Solar,
enabling the splitting up of the sunshine into its part colors.

The rules of spectroscopy outlined in a useful graphic by Lund Observatory. Mild from a star is handed via a prism and spreads out into its colors within the spectrum on the best. The darkish traces within the spectrum are attributable to the absorption of the star’s gentle at particular wavelengths because of the parts within the outer layers of the star. They supply a fingerprint permitting astronomers to work out what a star is manufactured from.

In 1868 astronomer Jules Janssen noticed a photo voltaic eclipse in India via a prism.  He observed a vivid yellow spectral line emanating from photo voltaic prominences – large storms erupting from the Solar.  The road was unidentified.  At first it was thought to return from the chemical factor sodium because it was shut by to 2 different vivid traces arising from this factor.  The 2 traces of sodium had been often known as the D1 and D2 Fraunhofer traces, named after their discoverer.  The unknown line was recognized later that yr by astronomer Norman Lockyer in a photo voltaic spectrum and he named it the D3 Fraunhofer line.  He concluded it was attributable to a brand new, unknown factor.  Lockyer named it Helios, after the Greek phrase for the Solar.  Helium was then unknown, and actually was not found on the Earth for an additional 27 years, till 1895.

A number of fascinating properties of helium have been
found within the ensuing years.  The
alpha particle, produced via radioactive decay, was discovered to be a helium
nucleus.  It’s the most simple product of
nuclear fusion in stars, as protons are changed into helium nuclei.  Helium, when cooled to close absolute zero, is
a liquid and has no viscosity, a phenomenon we name superfluidity.

This graphic represents the big selection of makes use of that helium is utilized to in quite a lot of industrial purposes. Credit score: USGS

Helium is now utilized in a variety of necessary industrial purposes.  Essentially the most well-known is flight, the place helium fuel (being much less dense than air) naturally offers buoyancy for airships and balloons.  Owing to its low boiling level helium is used extensively in cryogenic purposes.  Liquid helium acts as a coolant for superconducting “magnetic resonance imaging” (MRI) scanners used for medical analysis.

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