Posted
on August 18, 2014
French
astronomer Pierre Janssen traveled all the way to Guntur, India, to
watch a solar eclipse on this date in 1868. Of course, Janssen didn't
just watch the eclipse—he studied it—and he discovered some
important things about the Sun.
It's
wonderful that we CAN discover things about an object 93 million
miles away!
What
did Janssen discover? He observed bright lines in the spectrum of the
outer atmosphere of the Sun – a layer called the chromosphere –
that showed that it is gaseous.
One
of the lines was a very bright yellow line that was, it turned out, an indication of an element that had never been discovered.
The bright yellow line was helium – you know, the super-lightweight gas that we often
use to fill balloons and blimps, so that they will float in the air.
Janssen
noted that the chromospheric lines were so bright, they could be
observed even without an eclipse. This paved the way for studying
solar prominences without having to wait for—and travel to—a rare
total solar eclipse.
Janssen
even went on to demonstrate the ability to observe spectral lines
without an eclipse.
By
the way, Janssen's discovery of helium was made again just a few
months later—separately, independently—by the English astronomer
Joseph Norman Lockyer.
Because Lockyer went further, testing with a
chemist to see exactly what element made the line, Lockyer was the
one who got to name the new element, and today he shares credit for
helium's discovery with Janssen.
Check
out this spectacular example of a solar prominence! And here and here are more average solar
prominences. (Note that each prominence dwarfs the Earth in size, as shown in this scale drawing, left.)
Also
on this date:
Bad Poetry Day
Plan ahead:
Check
out my Pinterest boards for:
And
here are my Pinterest boards for:
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