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Hello, and welcome to Astronomy Daily.
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You're listening to season five episode 42
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for Wednesday the 18th of February, 2026.
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And what a day to be a space fan.
0:31
Tonight, right now, in fact, the moon
0:33
is sliding so close to Mercury that it's actually
0:36
hiding it from view for Skywatchers
0:39
in parts of the Southern United States.
0:41
A genuine celestial magic trick happening as you listen.
0:45
And that's just one of six stories we're bringing you today.
0:48
We've got NASA's Artemis II on the verge
0:51
of a crucial fueling test.
0:53
A European rocket making a big move
0:55
in the satellite broadband race.
0:57
A genuinely new twist in the ongoing saga
1:00
of our interstellar visitor.
1:02
And two stories that I promise will make you rethink
1:04
some things you thought you knew about the solar system.
1:09
So Anna, let's start with the biggest space story of the week.
1:12
And honestly, the one that could define the year.
1:17
Yes, for anyone who needs a quick refresh,
1:20
Artemis II is NASA's first crude mission
1:23
around the moon since Apollo 17 in 1972.
1:27
Four astronauts, Reed Wiseman, Victor Glover, Christina
1:31
Koch, and Canada's Jeremy Hansen are preparing
1:34
to fly a 10-day loop around the moon and back.
1:37
No lunar landing, but a crucial proving flight
1:40
before we put boots on the surface.
1:43
And they are so close.
1:45
The rocket is sitting on path 39B
1:47
at Kennedy Space Center right now.
1:49
But before NASA will commit to a launch date,
1:52
they need to successfully do what's
1:54
called a wet dress rehearsal, a full practice countdown
1:58
where they actually load the rocket with fuel
2:00
and take it right to the edge of launch,
2:02
then drain it all out again.
2:05
They did that once already on February 3rd.
2:08
And it didn't go smoothly.
2:09
A liquid hydrogen leak cropped up,
2:12
the exact same kind of problem that plagued Artemis I three
2:16
The countdown was terminated at T minus five minutes
2:19
and 15 seconds, close, but not close enough.
2:23
Which pushed the February launch window off the table entirely.
2:28
NASA Administrator Jared Isaacman was fairly
2:30
philosophical about it.
2:32
He said, this is exactly why you do a rehearsal
2:34
to find these issues before you're flying with crew.
2:38
But the clock is ticking.
2:40
Since then, engineers have replaced two seals
2:42
and a clogged filter in the hydrogen fueling system.
2:45
They ran a partial confidence test
2:47
on February 12th to check the repairs.
2:50
And now, tomorrow, February 19th,
2:53
they begin tanking day for the second full wet dress rehearsal.
2:57
This is the one that counts.
2:59
If the test goes cleanly, no ad of limits
3:01
hydrogen concentrations, countdown proceeds all the way
3:05
to the terminal phase, NASA will analyze the data
3:08
and set a launch date.
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The current earliest possibility is March 6th.
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It's worth noting just how historic this mission is
3:15
beyond the moon return angle.
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Victor Glover will become the first person of color
3:20
to travel beyond low Earth orbit.
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Christina Koch will be the first woman.
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Jeremy Hansen will be the first non-American.
3:28
Every single person on that crew
3:30
is making history in their own right.
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So tomorrow is genuinely a day to watch.
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We'll be keeping a close eye on how the tanking goes
3:38
and we'll have updates as they come through.
3:40
All right, let's bring it back to Earth
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or rather to the sky above Earth.
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Because tonight is one of those rare evenings
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where if you happen to be in the right place
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and you look up at the right moment,
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you'll see something genuinely extraordinary.
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Two things, actually.
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First, the moon and Mercury.
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Tonight, February 18th,
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a slender one and a half day old crescent moon
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is passing extremely close to Mercury
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in the western sky just after sunset.
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And I mean extremely close.
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For observers along a narrow band of southern US states,
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we're talking Arizona, New Mexico, Texas, Louisiana,
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Mississippi, and Georgia.
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The moon will actually pass directly in front of Mercury
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and block it from view entirely.
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That's called an occultation.
4:27
Mercury literally disappears behind the moon's dark limb
4:31
and reappears on the other side.
4:33
For everyone else across North America and beyond,
4:36
it won't be a full occultation,
4:38
but you'll still see a dramatically close pairing.
4:41
East Coast observers will see Mercury
4:43
sitting just north of the moon as twilight falls.
4:46
By the time darkness reaches the west coast,
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the moon will have shifted to within
4:50
about one degree of the planet.
4:52
Venus hangs brilliantly below them
4:54
as a helpful reference point.
4:56
Now, the window is tight.
4:58
Mercury sets not long after the sun.
5:00
So you want to get outside as soon as the sky darkens.
5:04
Look low in the west, southwest.
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If you can spot Venus and you'll have no trouble doing that,
5:09
it's blazingly bright.
5:11
Mercury will be nearby.
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The moon makes it easy tonight.
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And if that weren't enough,
5:16
Jupiter watchers have a tree too.
5:18
Tonight, Ganymede, Jupiter's largest moon
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and the biggest moon in the entire solar system,
5:24
is transiting across Jupiter's face.
5:27
East Coast observers can see it underway
5:29
as soon as it gets dark.
5:30
It takes just over three hours to cross the disc
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and then Ganymede's shadow follows it across,
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creating that striking black dot effect on Jupiter's cloud tops.
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So tonight really is a two-for-one skywatching event.
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Mercury and the moon in the west at dusk,
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Jupiter and Ganymede in the southeast through the night.
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If you have binoculars or a small telescope,
5:54
Staying with today's news,
5:55
and this one happened literally today.
5:58
Europe's Arian 6 rocket has successfully launched
6:01
32 satellites into orbit for Amazon's project Kuiper.
6:06
For those not familiar with Kuiper,
6:08
Amazon has been quietly building
6:10
a large constellation of broadband internet satellites
6:13
designed to take on SpaceX's Starlink.
6:16
This is a big commercial play.
6:18
Starlink currently leads the market
6:19
with thousands of operational satellites,
6:22
but Amazon has the resources and ambition
6:24
to make this a genuine competition.
6:27
What's notable about today's launch
6:29
is that it used the most powerful configuration
6:33
flying with four strap-on boosters rather than two.
6:36
It was essentially a statement of capability
6:39
from the European side of the commercial launch industry.
6:42
This rocket can handle serious payloads.
6:45
There's also a bigger picture here.
6:47
Arian 6 has had somewhat of a turbulent road.
6:51
It came in behind schedule
6:52
and faced some early technical hurdles,
6:55
but launches like this,
6:56
winning commercial contracts
6:58
for a high-profile constellation like Kuiper,
7:00
are exactly what Europe needs
7:02
to keep its launch industry competitive
7:04
in an era dominated by SpaceX
7:06
and an increasingly capable Chinese launch sector.
7:10
The broadband satellite race
7:11
is one of the defining infrastructure stories
7:14
of this decade, I'd argue.
7:16
Starlink has already changed
7:17
what connectivity looks like
7:19
in remote areas and conflict zones.
7:21
Hyper, Amazon's one-web investments,
7:24
the Chinese Go on constellation,
7:26
they all point to a future
7:28
where low-earth orbit
7:29
becomes genuinely critical economic territory.
7:32
Today's launch is one tile
7:34
in that much larger mosaic.
7:36
32 satellites closer to that future.
7:39
Now, an update on our interstellar visitor
7:42
and I do mean update.
7:43
There is genuinely new information here,
7:46
happening right now.
7:47
I know we've given three eye atlas
7:49
a quite a run over recent episodes,
7:51
but this one earns its place today.
7:56
three eye atlas is only the third interstellar object
8:00
ever confirmed to pass through our solar system.
8:03
It arrived from outside our stellar neighborhood,
8:05
swung around the sun last October
8:07
and is now heading back out into the galaxy forever.
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We will never see this object again.
8:13
But here's what's happening right now.
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He says juice spacecraft,
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that's the Jupiter icy moon's explorer,
8:20
currently en route to Jupiter,
8:22
pass with an observational range
8:24
of three eye atlas back in November last year.
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Due to the challenging thermal conditions
8:29
during juices transit through the inner solar system,
8:32
the data I collected couldn't be downlinked straight away.
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That data is now being transmitted to Earth.
8:39
The window is February the 18th to the 20th today.
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these would be the closest ever observations
8:46
of an interstellar object by a spacecraft.
8:49
Now juice didn't do a dedicated flyby,
8:52
its trajectories locked in for Jupiter,
8:55
but even opportunistic observations
8:57
from its suite of cameras, spectrometers,
8:59
and particle detectors could give us a perspective
9:02
on three eye atlas that no Earth-phase telescope can provide.
9:07
And the data would complement
9:08
an extraordinary recent run of discoveries.
9:11
Hubble has directly imaged the nucleus for the first time.
9:15
Day WST detected methane in its atmosphere,
9:18
a molecule never before seen
9:20
in an interstellar object.
9:22
And the object is still spinning faster
9:24
than it was before its solar encounter,
9:27
a legacy of all that outgassing
9:29
as it swung close to the sun.
9:31
Three eye atlas is now about three and a half astronomical units
9:35
from the sun in the constellation Gemini.
9:37
It's fading, but still reachable
9:39
with a decent amateur telescope.
9:41
And it has one more big act to play,
9:44
a close pass by Jupiter in March,
9:46
which may trigger fresh outbursts
9:48
as Jupiter's tidal forces stress the nucleus.
9:51
An extraordinary object.
9:53
And the fact that we have a spacecraft data
9:55
downlink happening as we record today
9:57
makes it entirely current.
9:59
What report would juice found
10:00
as soon as a science team's released their analysis?
10:04
Deep time now, I genuinely love this next story
10:08
because it takes something you thought you understood,
10:10
Saturn's rings, and reframes
10:12
the entire origin of the system.
10:15
New research by Mattia Chouk at the City Intitude
10:18
about to be published in the Planetary Science Journal
10:21
proposes a dramatic two-stage catastrophe
10:24
that reshaped the entire Saturnian system
10:27
roughly 400 million years ago.
10:29
And I mean reshaped everything.
10:31
Titan, the rings, hiapidus, Hyperion,
10:35
all of it connected to one ancient collision.
10:38
Let's set the scene.
10:39
Saturn has puzzled planetary scientists for a long time.
10:43
Its axial tilts is an unusually steep 26.7 degrees.
10:48
You don't expect gas giants to form that way.
10:51
Titan is migrating away from Saturn
10:54
at a surprisingly rapid rate.
10:56
The moon hiapidus sits at an oddly inclined orbit
10:59
and the rings are far younger than the planet itself,
11:02
only a few hundred million years old, geologically speaking.
11:06
One thing after another that didn't quite add up.
11:09
Juke and colleagues ran simulations
11:11
and found a scenario that explains it all at once.
11:14
The key player is a moon they're calling proto-hyperion.
11:18
Saturn used to have this additional mid-sized satellite
11:21
orbiting in the outer system.
11:23
When Saturn spin orbit resonance
11:25
with the other planets in the solar system broke down,
11:28
proto-hyperion was destabilized.
11:30
It drifted inward and it collided with a proto-titan.
11:34
The merger of those two moons, roughly 400 million years ago,
11:38
set off a chain reaction.
11:41
Some of the collision debris accreted around
11:43
what would become today's Titan,
11:45
explaining why Titan's surface looks surprisingly young
11:48
despite the moon itself being ancient.
11:51
Titan absorbed new material
11:53
and essentially reset its surface.
11:56
Other debris from the collision
11:57
perturbed the inner moon system.
11:59
Titan's resonant gravitational interaction
12:02
with proto-dyone and proto-raya caused further instabilities.
12:06
More collisions, more debris.
12:08
Most of that material eventually re-accreted
12:11
into the inner moons we see today.
12:13
Mimus, Enceladus, Tethis, Dione, Raya.
12:17
But a fraction of it stayed dispersed.
12:19
That fraction became Saturn's rings.
12:22
And Hyperion, the small, oddly shaped walnut-like moon
12:26
that looks like it survived a very bad day.
12:29
According to the model, it actually did survive a very bad day.
12:34
It formed from the debris of that proto-hyperion
12:37
and proto-titan collision and was captured
12:40
into resonance with Titan.
12:42
The researchers note that in most of their simulations,
12:45
Hyperion was lost entirely.
12:48
Its survival in a relatively small number of runs
12:51
suggests the real system was genuinely close
12:54
to being quite different.
12:55
What I find compelling about this
12:57
is how elegantly one event connects everything.
13:01
The tilt of the whole planet, the age of the rings,
13:04
the orbits of biopetus and Hyperion,
13:07
Titan's migration rate.
13:09
One ancient merger explains it all.
13:12
Now, the researchers are careful to say
13:14
this is a hypothesis, not a confirmed history.
13:18
Simulations can be suggestive
13:20
without being definitive.
13:21
But NASA's Dragonfly mission is heading to Titan.
13:24
It launches in 2028 and arrives in 2034.
13:29
One of the things Dragonfly will investigate
13:31
is the age and history of Titan's surface.
13:34
If the surface shows evidence of that ancient resetting,
13:38
that would be a powerful confirmation.
13:40
400 million years of cosmic history
13:44
hiding in a walnut-shaped moon.
13:48
And finally, a story that will make you rethink
13:51
just how long it takes to get to Mars,
13:53
or at least how long it might take one day.
13:56
Russia's state nuclear corporation, Rosatom,
13:59
through its Troyes Institute near Moscow,
14:01
has been developing a nuclear-powered magna-plasma engine
14:05
and they're making a bold claim
14:07
that this technology could get a crude spacecraft
14:10
to Mars in 30 days.
14:13
To put that in context, a conventional chemical rocket
14:16
takes roughly eight months to reach Mars.
14:19
30 days would be a transformation, not just an improvement.
14:23
It would fundamentally change the feasibility
14:26
of human Mars missions, less radiation exposure
14:29
for the crew, less time in microgravity,
14:32
a completely different logistical calculus
14:34
for resupply and emergency scenarios.
14:37
The engine works by accelerating hydrogen
14:40
using electromagnetic fields rather than combustion
14:43
to a velocity of 100 kilometers per second.
14:47
That's roughly 22 times faster
14:50
than the exhaust velocity of a conventional chemical rocket.
14:53
The working body is plasma, charged particles,
14:56
and it's driven by an onboard nuclear reactor
14:59
that provides the sustained electrical power
15:02
the accelerator needs.
15:04
Importantly, this isn't a launch engine.
15:07
You'd still use conventional chemical rockets
15:09
to get off Earth's surface and into orbit.
15:12
The plasma system switches on once you're in space
15:15
for the interplanetary crews.
15:17
Smooth, continuous acceleration followed
15:20
by a long deceleration burn.
15:22
The prototype is currently running ground trials
15:25
inside a 14 meter vacuum chamber
15:27
designed to replicate deep space conditions.
15:30
The researchers say the engine has demonstrated
15:33
sufficient longevity over 2400 hours
15:36
for a Mars transportation operation.
15:39
A flight-ready prototype is targeted for 2030.
15:43
Now, and this is important, there are real caveats here.
15:47
No peer-reviewed data has been published yet.
15:49
The thrust is very low around six newtons.
15:53
Integrating a nuclear reactor into a crude spacecraft
15:56
is an enormous engineering challenge in itself
16:00
with regulatory, thermal, and radiation shielding hurdles
16:03
that remain largely unsolved publicly.
16:07
Bear points, but the broader context is genuinely interesting.
16:11
NASA is investing in its own plasma propulsion programs.
16:14
The Vazimir engine from Ad Astra Rocket Company in Texas
16:18
targets a Mars trip of 45 to 60 days.
16:22
China has plasma thruster research underway too.
16:25
There's a real multi-nation push
16:27
to solve the propulsion problem for deep space travel.
16:31
Chemical rockets got us to the moon,
16:33
getting to Mars regularly, safely,
16:36
and at human time scales requires something different.
16:40
This is where that search is heading.
16:42
Wherever it ultimately leads.
16:46
Even as an aspiration, that's a sentence we're sitting with.
16:50
And that's our six stories for season five episode 42.
16:54
What a lineup from a rocket on a launch pad in Florida
16:58
to a crescent moon's swallowing mercury,
17:01
to the debris of a 400 million year old collision
17:04
still orbiting Saturn.
17:06
And an interstellar comet sending us its last data
17:09
from the edge of the solar system.
17:11
While Russia dreams of getting to Mars in a month,
17:14
base never has a quiet week.
17:16
If tonight's sky events caught your attention,
17:19
there is still time to get outside.
17:21
Mercury and the moon in the west,
17:23
Jupiter and Ganymede in the southeast.
17:26
You have your orders.
17:27
And keep an eye on Artemis.
17:29
Tomorrow's fueling test is one of those days
17:31
where the news could come fast.
17:34
Thank you so much for spending part of your Wednesday
17:37
We'll be back tomorrow for more from the universe.
17:40
Until then, clear skies, everyone.
17:42
The sunny day, the star is the toll.
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The star is the toll.
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