Anna: G' day and welcome to Astronomy
AstroDailyPod. I'm Anna.
Avery: And I'm Avery. It's the weekend wrap for
Saturday 8th August, and this is one of those
rare weekends where the sky itself is the
headline. We are four days out from a total
solar eclipse and the peak of the Perseids
landing on the very same night.
Anna: We'll get you set for all of that in the sky
watch at the end. Both hemispheres, proper
local times and one eye safety rule.
None of us are allowed to skip.
But we start where the whole week has quietly
been pointing at the sun.
Avery: Then, um, three storeys at the find the week.
A rocket stage that finally hit The Moon, a
48 year old spacecraft that just bought
itself another year of life, and the rescue
mission that spent, uh, the week rescuing
itself. Let's go.
Anna: Here's the question that sounds simple and
isn't. What does the surface of the sun
actually look like up close? Not the
postcard, the fine detail right down at
the scale where the physics happens. This
week for the first time, we got to see it.
And the answer is it's covered in whirlpools.
Avery: Whirlpools on the sun.
Anna: Tiny ones, some only about 20
kilometres across, which on the sun is almost
microscopic. In a paper published Wednesday
in Nature, a team led by David
Kureads at the U.S. national Solar
Observatory in Hawaii, the biggest solar
telescope ever built, a four metre mirror
on Haleakala, zoomed in on the
edges of the sun's granules. And where
earlier telescopes saw a smooth, slightly
blurry boundary, Inoue saw
structure curling, breaking, wave
like swirls forming and dissipating
everywhere along the magnetic boundaries.
Avery: And, um, these have a name. They're not a
total surprise, physically.
Anna: Right, exactly right. And that's what makes
it satisfying rather than baffling. They're
called Kelvin Helmholtz instabilities.
If you've ever watched wind peel the top of
an ocean wave, or seen those rows of curling
cloud that look like a breaking sea in the
sky, that's the same effect. It happens
whenever two fluids slide past each other at
different speeds. Lord Kelvin and Hermann
Helmholtz described the math back around
1870.
Avery: So the physics is 150 years old. The
picture of it on the sun's surface is four
days old.
Anna: That's the whole storey in one line. We've
seen these swirls in Earth's clouds, in the
atmospheres of Jupiter and Saturn, even
hinted at high up in the sun's outer
corona. But never before down on the
visible surface, the Photosphere where the
solar wind and all that magnetic energy
actually originate. The resolution
simply wasn't there. Inui changed that.
Avery: Walk me through why the surface is the
important place to catch them.
Anna: Because that's where the sun's magnetic field
tangles with its boiling convection. Picture
the granules, those bright cells of hot
plasma, rising, cooling, sinking
like a pot of porridge on the boil at the
edges. Flows crash into each other, and the
magnetic field lines get squeezed together.
Bundle field lines tighter, and the field
gets stronger. The stronger field resists
the plasma flow. And that sudden change in
speed is exactly the shear you need to set a
Kelvin Helmh vortex spinning.
Avery: And they didn't just eyeball it and declare
victory.
Anna: No, this is the part I like. They ran the
same magnetic region through a state of the
art physics simulation, A model called
Maram, built purely from the laws of
physics. No fudging. And the simulated sun
grew the same swirls in the same places with
the same shapes. Observation and theory
shaking hands. The Max Planck team called the
agreement remarkable. And that's the word
that earns this a, uh, nature paper. Not we
saw something odd, but we saw it. We
understand why. And the model agrees.
Avery: So why should someone with feet firmly on the
ground care about micro whirlpools
93 million miles away?
Anna: Two reasons, and they're both big. The
first is one of the great unsolved puzzles in
solar physics. The corona problem. The
sun's surface is around 6,000 degrees.
Its outer atmosphere, the corona, is
millions of degrees, hundreds of times
hotter. Further away from the heat source.
That should be impossible. Like standing
back from a campfire and getting warmer.
Something is carrying energy upward and
dumping it into the corona. And these
ubiquitous little vortices are a very good
candidate for part of that pipeline.
Avery: And the second reason is the one that reaches
down and touches U.S. base weather.
Anna: Those same swirls could feed the buildup of
magnetic energy that the sun eventually
releases as flares and coronal mass
ejections. The blasts of charged
particles that, when they're aimed our way,
can knock satellites about, degrade GPS
and stress power grids. The next step
is to turn pattern recognition algorithms
loose on long runs of ENOYE data
to measure how much these instabilities
actually shift. Nail that number, and
you sharpen the models that forecast solar
storms.
Avery: Which is a lovely place to be starting an
eclipse week. Honestly, everyone's about to
point their attention at the sun anyway.
Anna: It really is. For decades, this was a
prediction on a chalkboard. This week, it
became a picture. The Sun's surface
isn't a smooth glowing ball, it's a
sea and it's full of breaking waves
from the sun to
Avery: the moon and to a storey. This show first
flagged back in the autumn. Early Wednesday
morning, a spent SpaceX Falcon 9 upper
stage slammed into the far western edge of
the moon near Einstein Crater at around half
past two in the morning US Eastern time.
Anna: This is the one astronomer Bill Grey had been
tracking since April.
Avery: The very one. Catalogue number
2025 010D.
Roughly four tonnes of hollow metal, about 12
metres long. It launched in January last
year, carrying two commercial lunar landers,
Firefly's Blue Ghost and I. Space's
resilience. Under NASA's Commercial Lunar
Programme, its job done, it was left
drifting. And for 19 months, sunlight
and gravity nudged it around cislunar space
until the numbers lined up on a collision
course.
Anna: And it hit at genuinely startling speed,
Avery: about 5,400 miles an hour,
seven times the speed of sound, releasing
energy like roughly three tonnes of TNT.
The catch for skywatchers, it came down on
sunlit ground, so any flash was washed out by
daylight. Nobody on Earth got the fireworks.
Anna: So how do we actually confirm it happened
and see the scar from orbit?
Avery: And this is where it gets good. NASA's Lunar
Reconnaissance Orbiter and South Korea's
Dhanuri spacecraft are retasking to
photograph the site. Because we know almost
exactly where and when it struck. We get
a rare before and after. A fresh crater
expected somewhere between 18 and 30
metres wide, appearing on a patch of moon we
already had mapped. I'll be honest, those
high resolution images aren't in hand yet.
They depend on lighting and orbital geometry
over the coming weeks. But the impact itself
is confirmed.
Anna: And there's a bigger point sitting underneath
the spectacle.
Avery: There is.
This is only the second known unintentional
lunar impact by a rocket stage. The first was
a Chinese Booster back in 2022. But the
traffic up there is climbing fast and there's
still no binding rulebook for disposing of
hardware on these high energy paths.
SpaceX says this stage was passivated by the
book and is now working with NASA on
prevention. Fittingly, the international
meeting that produced the latest
recommendations for the moon was held right
here in Sydney. The recommendations are real.
The requirements aren't there yet.
Anna: A new crater and a, uh, nudge to write some
rules before the next one.
Now to the most distant good news, Storey,
you'll hear all year. Voyager 2, launched
in 1977, now more than
21 billion kilometres away out
in Interstellar space has just been given
at least another full year of science by
engineers who can't touch it, can't send it
apart and have to wait about 19 and a
half hours just for a command to arrive.
Avery: And they've given the manoeuvre a wonderful
name.
Anna: They're calling it the Big Bang. Here's the
problem it Voyager runs on
plutonium radioisotope generators
that turn heat from decay into electricity
and that supply drops by about 4
watts every single year. It's a
spacecraft slowly running out of power. And
for years the fix has been to switch
instruments off one by one without action.
Voyager 2 would have had to shut down another
of its three remaining instruments before the
end of this year.
Avery: So why Big Bang? What's dramatic about a
power swap?
Anna: Because it all had to happen at once. They
switched off a set of power hungry devices
and swapped in lower power alternatives.
But the catch is that the very same power
also produces heat. And out there, near
absolute zero, if the wrong component gets
too cold, it freezes and dies
permanently. You can't do it gently, one
step at a time. The thermal sums only
balance if you throw the switches
simultaneously. As one of the engineers put
it, they couldn't afford to be wrong. And
it worked exactly to plan.
Avery: And Voyager 1 is next in the queue.
Anna: It is. The team is stepping through the same
process on Voyager 1 in the coming weeks. And
the early tests have gone smoothly. Two
probes, 48 years old, still
humanity's only instruments physically out in
interstellar space, kept alive by people
rewriting how the hardware is used from
13 billion miles back. That's not
a rescue. That ends the storey. The power
keeps falling. But it's another year of
listening to the space between the stars.
Avery: And now our, uh, running saga of the week.
The rescue mission that spent the week being
rescued. You'll remember the setup. NASA
Swift Observatory, 22 years old, a
first responder for gamma ray burst is
sinking. Its orbit is decaying and it can't
lift itself. And without help, it's likely to
re enter this spring, our time. Once it drops
below about 300 kilometres.
Anna: Enter link. Built at extraordinary
speed to go up and give Swift a boost.
Avery: A commercial servicing spacecraft from
Catalyst Space built clean sheet in about
nine months. Launched last month. First of
its kind. A private robot grabbing a
government satellite that was never designed
to be serviced, except that during
commissioning, Link itself tumbled into a
multi axis spin up to 9 degrees a
second. With two of its three reaction wheels
out of action and some loss in its cold gas
thrusters. The rescuer needed a rescue.
Anna: And this week is where that turned a corner.
Avery: It genuinely did. Using thruster
burns, the team has wrestled that spin all
the way down from 9 degrees a second, uh, to
1.47 degrees. And they're holding
it steady there. The D spin effectively is
one the mission has now shifted from a
stabilisation problem to a software one.
Because so much of the original attitude
control system is offline, they're preparing
a major flight software upgrade to restore
full control using what still works.
Anna: And only once that lands can the chase
actually begin.
Avery: Right, software update first, then the
phasing manoeuvres to line Link's orbit up
with Swift. Then a rendezvous and, uh, a
grapple with its three robotic arms targeted
around the end of August. If it all comes
off, Lynx slowly walks Swift back up toward
its old orbit over a couple of months, then
peels away and burns up itself. It's down
to the wire. But a week ago, this looked
close to lost. And today it looks like a
spacecraft catching its breath. Breath before
the hardest part.
Anna: We will absolutely keep you posted as that
end of August window comes up.
And so to the sky. And What a, uh, four days
we're heading into. On Wednesday 12th
August, two of the year's marquee events land
together. A, uh, total solar eclipse and
the peak of the Perseid meteor shower.
Avery: Let's be straight with everyone about who
sees what, because this one is lopsided.
Anna: It is. So let's do it. Honestly, the
total eclipse, the full daytime darkness,
corona blazing spectacle, belongs to the
far north. The path of totality crosses the
Arctic, eastern Greenland, western Iceland
and clips northern Spain and the very
northeast of Portugal near sunset. If you're
anywhere near there, you're in for one of the
sky's greatest sights, under two and a half
minutes of it.
Avery: And, um, for our North American listeners,
our largest audience, the honest picture is a
partial and only in one corner.
Anna: That's right. No part of North America sees
totality this time. But in the afternoon on
the 12th, Eastern Canada and the northeastern
United States get a genuine partial in parts
of Atlantic Canada, roughly half the sun
covered at maximum. A smaller bite across New
England and the Northeast further west, it
fades to little or nothing. If you're in
that eastern window, cheque local times for
your exact town. It's an afternoon event. And
dig out your eclipse glasses.
Avery: Which brings us to the rule we
Anna: never, ever skip the non
negotiable. To look at any partial phase
of the sun safely, you need proper solar
filters. That meet the ISO
123122 standard
certified eclipse glasses or a safe solar
viewer M ordinary sunglasses do not work
no matter how dark. Only someone standing
inside the path of totality may remove them
and only during the brief total phase.
Everyone seeing a partial, that's all of
North America and most of Europe keeps them
on the entire time. Damage to your eyes
is painless and permanent. Please don't risk
it.
Avery: And if you're nowhere near the track, which
includes all of us down here in the south,
NASA streams the whole thing live from about
a quarter past one eastern.
Anna: Now the Perseids that same night and here the
news is good for the northern half of the
world. The peak lies the night of the 12th
into the 13th and this year the peak is
essentially moonless. The eclipse falls on a
new moon so the sky is dark and the faint
meteors get their moment from the mid
northern latitudes after midnight that's
potentially dozens an hour under clear skies.
North America, Europe, this is your gift of
the week.
Avery: But the Perseids are a northern shower. The
radiant barely lifts above the horizon.
Anna: For those of us down here it barely clears
it. So from Sydney or Auckland you'll catch
only a stray few low in the north before
dawn. So here's what the southern hemisphere
actually gets and it's worth setting an alarm
for before sunrise. This week the morning
sky is stacked a long line of planets
Saturn, Mars, Uranus and
Neptunewith Jupiter low and Mercury
climbing strung across the pre dawn.
Venus is your brilliant evening star after
sunset and for the patient Comet
10P Tempel 2 is rising late in the
evening around half past nine. If you've got
binoculars and a dark
Avery: horizon so nobody misses out. North gets
the eclipse and the meteors. South gets the
planet parade and a comet and the livestream
is there for all of us.
Anna: Both hemispheres eyes up all week, just
protect them around that sun.
Avery: That's the weekend wrap for Saturday 8th
August. The Sun's hidden whirlpools, a
fresh crater on the moon, Voyager 2's
extra year and a rescue mission back on its
feet.
Anna: We're back with your daily fix on Monday and
all week we'll be counting down to that
eclipse and Perseid Wednesday. Find the full
back catalogue, the news feed and the
newsletter@uh astronomydailyio
and say hello@astronomydailypod
until Monday from Anna and me.
Avery: Look after those eyes and clear skies.