What experimental technique was used to discover the huge hydrogen cloud that surrounds the nucleus and the coma of a comet?
A)Hubble Space Telescope IR photography
B)ground-based photography, at the hydrogen Balmer $\alpha$ wavelength
C)radio measurements at 21 cm wavelength
D)rocketborne ultraviolet photography

Question

Quizplus · Accepted Answer

Rocketborne ultraviolet photography was used to discover the huge hydrogen cloud surrounding the nucleus and the coma of a comet. This technique is effective because hydrogen emits strongly in the ultraviolet part of the spectrum, which cannot be observed from the ground due to the Earth's atmosphere blocking most ultraviolet wavelengths.

What Experimental Technique Was Used to Discover the Huge Hydrogen α\alphaα

What Experimental Technique Was Used to Discover the Huge Hydrogen $\alpha$