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18 HEALTH AND LABORATORY MAGAZINE

WHY THE ‘ICY

PLANETS’ ARE

DIFFERENT SHADES

OF BLUE?

They are the far-away ‘icy planets’
of our solar system. However two of
them glow a slightly different shade The mystery of why Uranus (left) appears pale blue and Neptune (right) a deeper, cobalt
of blue. hue may have finally been solved. The answer, scientists say, lies in the fact Uranus has a
haze layer in its atmosphere that is roughly double the thickness of Neptune, giving it a paler
colour.

Now the mystery of why visible wavelengths. and methane in their skies, frared spectra of the solar why Uranus appears to
Uranus appears paler than although hazes formed of system’s ‘ice giants’, Uranus have a paler blue colour
Neptune’s deeper, cobalt It acts to lighten the ap- other chemicals are also and Neptune, have fasci- to the human eye than
hue may have finally been pearance of the seventh thought to exist at different nated planetary astrono- Neptune’.
solved. planet from the sun, in a altitudes, too. mers for many years.
similar way to how tracing Naomi Rowe-Gurney, who
The answer, scientists paper over a picture makes The researchers believe ‘The atmospheres of the researches the atmos-
say, lies in the fact Ura- vibrant colours seem more these are likely created ice giants are observed to pheres of Uranus and Nep-
nus has a haze layer in its milky. when methane is broken have similar atmospheres tune at NASA’s Goddard
atmosphere that is roughly by ultraviolet radiation with similar tropospheric Space Flight Center, told
double the thickness of ‘This explains why Uranus from the sun, before being temperature profiles.’ the New Scientist: ‘Seeing
Neptune, giving it the much is a paler blue colour than remade into larger hydro- both planets successfully
lighter colour. Neptune,’ said the study’s carbons. They added: ‘Both planets compared directly in analy-
lead author Patrick Irwin, of appear blue or blu- sis is rare.
University of Oxford-led re- the University of Oxford. It is this methane that also ish-green to the naked eye,
searchers termed this the gives both Neptune and in contrast to the more ‘The authors state that
Aerosol-2 layer, which they Both Uranus and Neptune Uranus their blue appear- yellowish appearance of future observations will
said would look whitish at have hydrogen, helium ance, according to the Jupiter and Saturn. help to answer remaining
study’s authors, because questions and I am sure
methane absorbs red ‘We now know this blueness that the James Webb
light and leaves blue to be comes from a combination Space Telescope will help
reflected back. of this higher abundance of with this during the planned
gaseous methane, which observations of both plan-
The researchers created has strong absorption ets within the first year of
models of the atmos- bands in the infrared and operations.’
pheres of both worlds by red portion of the visible
using data from the Hubble spectrum.’ The research has been
Space Telescope and published in the journal
ground-based observa- The researchers explained Earth and Planetary Astro-
tories, as well as informa- that their modelling found physics.
tion from the Voyager 2 Uranus’ atmosphere to be
spacecraft. significantly thicker than
The thicker Aerosol-2 layer lightens the appearance of that of Neptune.
Uranus (shown in the diagram above), in a similar way to In their study, they wrote:
how tracing paper over a picture makes vibrant colours ‘The visible and near-in- This, they said, ‘explains
seem more milky.