Uranus, the second farthest planet from
the sun and the long-suffering butt of
the joke. Yes, let's get that out the
way. This oftforgotten orb, rarely
lorded like its larger cousins Saturn
and Jupiter, rolls around the solar
system on its side. It has only been
visited once, and even that was
fleeting. The Voyager 2 spacecraft sped
past on the 24th of January 1986 with
just a few hours of uplose observations.
For the last 40 years, this has been the
foundation of what we know. No other
spacecraft have even been close.
But that doesn't mean new discoveries
have stopped. Technological advances in
telescopy and fresh takes on old Voyager
2 data have revealed a raft of
remarkable new insights, some of which
might rewrite the textbooks. And just in
time, there's a perfectly aligned launch
window opening in as little as 5 years.
Whether or not we'll make a trip back to
the planet is yet to be seen. But as we
approach such a critical decade for
revisiting Uranus, it's time to get back
up to speed with this forgotten world
and unveil the latest findings. I'm Alex
catalog and show that sometimes new discoveries don't need new data.
Uranus is the seventh planet from the
sun and since its discovery from William
Herschel's back garden in 1781,
only 2.9 uranian years have passed. Each
lasting 84 Earth years, the next new
year is approaching in 2033.
This strange world is perhaps best known
for its near horizontal tilt. Its spin
axis is angled at 97.77°
to its orbital plane. So, it essentially
rolls its way around the sun. To put
that in context, Neptune's axis at 28°
is the next highest. This gives Uranus
the most extreme seasons in the solar
system. Each pole faces the sun
continuously for 42 years of polar day
followed by 42 years of polar night.
This was pretty much all we knew about
Uranus as 1985 came to a close. We
guessed it might be an ice giant and
were aware of five moons and a ring
system, but essentially this planet was
a mystery.
Then in 1986,
Voyager 2 arrived. flying past on its
way out of the solar system. Almost
instantly, numerous discoveries were
made.
This enigmatic planet was revealed to be
even colder than expected, challenging
our fundamental ideas of how planets
form and evolve. At -24°
C, Uranus's atmosphere holds the record
for the coldest temperature on any
planet in the solar system. Voyager 2
also found a magnetic field tilted in a
way we had never seen before. 11 new
moons and two new rings. Its iconic
imagery showed a calm and eerie blue
green world.
But recent observations and research
have built on this picture, refining and
in some cases redefining our
understanding of this sideways planet.
What's more, returning to Uranus has
been marked as the highest priority in
NASA's planetary science program for the
next decade. With this renewed interest,
let's dive into some of the most
remarkable findings of recent years.
Uranus is four times wider than Earth
with a diameter of 51,118
km and a mass that's 14.5 times greater
than our planets. These parameters can
be used to calculate its gravity, which
for Uranus is a comfortable 8.7 m/s
squared, about 89% of the gravity we
experience on Earth. Grouped with
Neptune as an ice giant, Uranus is
believed to have a rocky silica core,
likely much smaller than Earth's,
surrounded by a deep mantle of water,
ammonia, and methane ices. a misleading
term since its inner temperatures can
soar to nearly 5,000° C. It's much more
like a fluid ocean than ice, as we might
think of it.
This extreme heat and the immense
pressure at the base of the mantle, up
to 600 gigapascals, can break down the
abundant methane molecules and compress
the resulting carbon atoms to form
diamonds. A captivating picture, but is
it right? Voyager 2 data initially said
so, but new modeling published in the
journal Astronomy and Astrophysics in
2025 suggests that it's perhaps not
quite the whole story. The researchers
Luca Morph and Ravit Helled of the
University of Zurich took an agnostic
approach generating random models of the
interior contents of Uranus and its ice
giant neighbor Neptune. These were then
compared to observational data and
narrowed down accordingly with one major
surprise.
The results show that the possible
composition of Uranus is much more
varied and complex than previously
assumed. For example, the rock to water
ratio could be as low as 0.04,
making the planet almost entirely water
or as high as 3.92,
making it the complete opposite, namely
predominantly rock. This means that
Uranus and Neptune have the potential to
be rock giants instead of ice giants.
What's more, if the rock dominated
option holds up, it challenges our
fundamental models of solar system
formation.
But as the authors attest, this work is
theoretical. We'll only know for sure by
visiting the planet again. More on that
later. Continuing
out from the rocky core, the outermost
layer of Uranus is comprised mostly of
helium, hydrogen, and 2% methane with a
cloud layer on top. Methane absorbs red
light, leaving behind the distinctive
blue green hues Uranus is known for.
Voyager 2 during its 1986 flyby found
Uranus cold and tranquil with only faint
clouds and a dark spot. But this veil of
tranquility has been lifted thanks to
telescopes including KEK, Hubble, and
the James Web Space Telescope, revealing
a hidden dynamism.
In 2014, the WM KEK Observatory in
Hawaii detected eight huge storms on
Uranus's northern hemisphere. Such was
their intensity that for the first time
ever, amateur astronomers were able to
see details in the planet's atmosphere.
The largest white spot in this near
infrared image from the WM KEK telescope
is the brightest storm ever seen on the
planet at this wavelength of 2.2
microns. It's around twice as bright as
anything seen before. It accounted for
30% of all the light reflected by the
planet in this observation.
The cloud rotating into view in the
lower right also grew into a storm
spotted by amateur astronomers at
visible wavelengths
which was a lot of fun for the amateur
astronomers. Of course, having the right
Astramm 5 at checkout can even get 5% off their purchase.
Observations
by Hubble over a 20-year period found
that the polar regions become noticeably
more meteorologically active as the
planet moves through its uniquely long
seasons.
Despite the study lasting two decades,
Uranus was in northern spring for the
entirety of this time with the sun
starting at equinox over the equator and
moving towards the north pole as it
nears summer. The Hubble team's results,
published in 2025, found bright cloud
activity when the sun was closest to the
equator, with peak activity observed
near the 2007 equinox.
The haze and cloud structure changed
dramatically over the four observation
windows with aerosols in the atmosphere
thickening at the north pole as the
planet approaches the summer solstice,
which it will reach in 2030.
You can see this accumulation of
aerosols in these images. The North Pole
changes from dark in 2002 to highly
reflective in 2022 with complimentary
darkening of the South Pole as it moves
into winter's shadow. Together, this
shows that sunlight is directly altering
the formation of haze and clouds in the
uranian atmosphere.
The Hubble observations also identified
circulation patterns that drive seasonal
shifts, uncovering evidence of
atmospheric gases sinking at the poles
and upwelling elsewhere.
The persistence of this downwelling and
the changes in climate are driven by
Uranus's extreme axle tilt. It's the
only planet that receives more energy
from the sun at its poles than the
equator, and it experiences the most
radical seasonal changes in the solar
system. But it's not just the sun's
light that drives this. A team at
Imperial College London found that the
uranium thermosphere is also heated by
the solar wind. Again, this is the only
place in the solar system where this
seems to happen. But as the solar winds
pressure has been dropping since 1990,
Uranus has been cooling alongside it.
Despite these remarkable findings,
Uranus is still significantly less
volatile than its cousins Jupiter,
Saturn, and Neptune. They are famous for
their vast storms and swirling
atmospheres. And that's because these
are driven by internal heat left over
from the formation of these gas giants.
It's the slow release of this energy
that creates the turbulence they are so
well known for. Which brings us to one
of Uranus's great mysteries.
Why is it the coldest planet in the
solar system? What happened to the heat
left over from its formation?
Two recent studies, both published in
2025, revealed that Uranus does have its
own heat, but only releases a tiny
fraction of it, emitting about 15% more
energy than it receives from the sun. By
comparison, its neighbor Neptune emits
more than twice as much energy as it
receives. This extremely low heat flux
is more than just another oddity for the
oddball planet. It hints at a violent
past with consequences not just for its
climate and weather, but its fundamental
characteristics and even its moons.
Uranus's near horizontal 97.77°
tilt has long been thought to be a
consequence of a violent historical
collision, but we've only recently
started to uncover the full picture.
Highresolution computer simulations
published in the Astrophysical Journal
in 2018 by Jacob Kegaris at Thurm
University and his colleagues have
provided a more detailed picture of how
this could have happened and the
farreaching influence it had for the
planet. Their study ran more than 50
different impact scenarios in an attempt
to recreate the Uranus we recognize
today. The result confirmed that 3 to
four billion years ago, a young Uranus
was most likely dealt a glancing blow by
an object two to three times the size of
Earth, probably a protolanet made of
rock and ice. The impact would have
occurred over a remarkably short period.
In just a matter of hours, enough force
would have been delivered to reorient
Uranus's axis, knocking it to its side,
and it set in motion a series of events
that created the planet we see today.
The simulation show that most of the
protolanet was deposited in Uranus,
creating a hot, high entropy shell in
the icy interior. Highly disordered,
high entropy materials don't conduct
heat well. So, this layer acts like an
insulation, trapping heat deep inside
the planet and helping to explain the
low heat flux and extreme coldness we
see on Uranus today.
This unique interior structure may also
help explain Uranus's profoundly weird
magneettosphere.
Usually, these invisible magnetic
shields originate from the geometric
center of a planet, its core. But that's
not the case here. Voyager 2's original
flyby discovered that its magnetic field
is tilted by almost 59° from its
rotational axis and offset from the
planet center by a third of the planet's
radius. This magnetic misalignment
creates an asymmetric magneettosphere
with a magneetto tail that corkcrews
into space for millions of kilome. When
Voyager 2 flew past, the magneettosphere
actually appeared to be much smaller
than thought and this has baffled
scientists for decades. Recent
reanalysis of the original data led by
Jamie Jasinski at NASA JPL and published
in Nature Astronomy in 2024 finally
provided an answer. When Voyager
arrived, it was in the midst of some
violent space weather that compressed
the planet's magnetic field. Something
NASA couldn't have planned even if they
tried. The new study instead suggests
that the planet's magneettosphere is
actually even larger and more active and
variable than initially thought. The
reason for such a strange
magneettosphere isn't fully understood.
But it could be that fields don't
originate from the planet's core at all.
Rather, they come from the convecting
mantle influenced by the deposits left
by that ancient collision billions of
years ago. For us at least, this has had
one serious upside. The off-kilter
magneettosphere leads to stunning
sprawling auroras that do not align with
the poles like on Earth, Jupiter, or
Saturn. These phenomena have been imaged
by Hubble in both the visible and
ultraviolet parts of the spectrum. And
by studying a decade of these images,
scientists recently calculated Uranus's
rate of rotation with 1,000 times
greater accuracy than before. Their
technique revealed the planet completes
a full rotation in 17 hours 14 minutes
and 52 seconds, 28 seconds longer than
the estimate obtained by Voyager 2. And
I simply couldn't miss out including
this stunning representation. It shows
infrared auroras which after 30 years of
study were finally detected on Uranus in
2023 using the KEK 2 telescope.
But the consequences of Uranus's violent
past haven't ended yet.
At the time of impact, its largest moons
hadn't formed. Instead, the planet sat
amid a disc of stuff, for lack of a
better word, with the impact jettisoning
further rock and ice into orbit around
the planet. As this started to clump
together to form the five largest moons,
Uranus's new axle plane acted like a
gravitational tidal wave, pushing them
to the same tilt. As of now, Uranus has
29 confirmed moons, two more than when I
last made a video about the planet. Moon
28 is currently called by the rather
catchy title S2023 U1 and was discovered
in 2023 by Scott Shepard using the Las
Campanis Observatory in Chile. The most
recent addition, its 29th moon, was made
in February 2025 by using the James Webb
Space Telescope's NEAM. Designated S2025
U1, it is yet to be officially named.
Let me know if you have any great
suggestions for names in the comments.
This startling array of moons is divided
into three categories: 14 inner moons,
five major moons, and 10 irregular
satellites. Romantically they are named
after characters from English
literature. The major moons Miranda,
Ariel, Umbreel, Titania, and Oberon
feature diverse compositions dominated
by water, ice, and rocky material.
Studies published in 2025, it was a very
busy year for Uranus scientists, hint at
possible differentiated interiors with
liquid oceans sandwiched between rocky
cores and icy mantles. which of course
raises the tantalizing question of
whether they are habitable for life. But
again, only an actual visit could tell
us that
like its immediate neighbors Saturn,
Jupiter, and Neptune, Uranus has a ring
system. They are aligned with its tilted
spin axis. So during Voyager 2's
approach 40 years ago, they appeared
almost like a bullseye.
The rings are very young by solar system
standards, thought to be a mere 600
million years old, and they're believed
to have been formed by the breakup of a
small moon colliding with a meteorite or
a comet. Their most remarkable feature
is how dark they are. With an albido of
less than 2%, they are made of the
darkest material in the solar system.
What exactly that is is of yet unknown,
but scientists think it could be
particles of water ice mixed with
organics or methane ice singed black.
Against Uranus's bright exterior, the
rings are really difficult to discern.
So much so that they were discovered by
accident in 1977 thanks to a star
occultation. An event in which Uranus
moved in front of a star and the
subsequent dimming confirmed the
presence of the rings.
13 rings have now been imaged thanks to
Voyager 2 as well as the advanced
telescopy of Hubble, Kek 2, and the
James Web. They range from a few kilome
wide to roughly 100 km wide, and it's
unclear why some of the rings are kept
so narrow. Shepherd moons may help
maintain the structure of some of them,
but for most, the mechanics remain
obscure.
Excitingly, a rare stellar occultation
happened again in April 2025 with Uranus
passing in front of a star about 400
light-years from Earth. This led to a
coordinated effort to observe Uranus
like nothing done before. Led by
planetary scientists at NASA, Langley,
an international team of over 30
astronomers using 18 observatories
simultaneously trained their attention
on Uranus for about an hour. It was the
largest campaign ever organized and the
largest simultaneous observation of
Uranus since Voyager 2's 1986 flyby. The
nature of an occultation is perfect for
studying Uranus's atmosphere and rings.
Atmospheric findings are yet to be
released, but the precision of the ring
data, specifically the timings of each
occultation, have allowed scientists to
determine where Uranus is in its orbit,
updating its position by around 400 km.
This is critical information for sending
a physical mission, but I'll talk more
on that later. This unprecedented
coordination is just the beginning. Over
the next decade, Uranus is set to pass
between Earth and the galactic center of
the Milky Way. Prime opportunity to
carry out further occultation studies
with the best ever conditions lined up
for 2031.
The last few years have been a flurry of
publications and activity. Looking at
you 2025 focused on the strange seventh
blue green sideways planet revealing it
to be a dynamic world with a storied
past and enigmatic features. So much has
been learned since William Hershel stood
in his back garden looking through a
homemade telescope. And that's despite
Uranus and its neighbor Neptune being
the least visited planets in the solar
system. Even more discovery lies ahead
still.
The 2023 planetary science decod survey
has made a Uranus orbiter and probe
mission NASA's top planetary priority.
and the Chinese National Space
Administration have also proposed a
mission to the planet with Tanwin 4.
With the possibility of another visit on
the horizon, scientists will need to
look sharp as we are approaching a
critical window. 2031
and 2032 are optimal launch
opportunities. Thanks to planetary
alignments, a future spacecraft could
get a gravity assist from Jupiter,
shortening the journey by several years.
Mission objectives are set to include
mapping the planet's gravity and
magnetic fields over time, studying the
weather systems and atmospheric
composition, characterizing rings, and
investigating the potential habitability
of its moons. So stay tuned. The next
chapter of Uranus exploration is being
written as we speak.
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