Artemis, Pulsars, Big Crunch & City Killers

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Welcome to Astronomy Daily.

I'm Anna.

And I'm Avery.

It is Thursday the 19th of February, 2026.

And we are recording this episode

while NASA is literally fueling a rocket

at this very moment.

And we cannot wait to tell you about it.

That's right, this is one of those days

where space news isn't just something

that happened somewhere out there in the universe.

It is happening right now on a launch pad in Florida.

But that's not all.

Today, we're also asking what lurks in the darkness

between us and our nearest cosmic neighbors?

Could there be a cosmic clock ticking next

to the most extreme object in our galaxy?

And brace yourselves, is the universe actually going to end?

Plus, we have a story that will make you

want to check the sky tonight.

A warning from NASA that is genuinely a little unsettling.

And we're going to space with the music video.

All of that is coming up on Astronomy Daily.

Let's start with the big one.

And I mean big in every sense of the word.

As we speak, NASA's space launch system,

the most powerful rocket ever built,

is being loaded with more than 700,000 gallons

of cryogenic propellant at Launch Complex 39B

at Kennedy Space Center in Florida.

This is the second wet dress rehearsal for Artemis II,

the mission that will carry four astronauts

on a loop around the moon.

The first time humans have ventured to lunar distance

since Apollo 17 back in 1972.

The crew are Commander Reed Weisman, Pilot Victor Glover,

Mission Specialist Christina Cokes from NASA,

and Jeremy Hansen from the Canadian Space Agency.

Now, the reason they're doing this rehearsal

and the reason there have been so many eyes on it today

is that the first attempt back on the second

and third of February did not go as planned.

Engineers detected a liquid hydrogen leak during fueling,

which forced them to halt the test

before they could complete the full countdown sequence.

In the week since, technicians have replaced seals

around two fueling lines, swapped out a filter

and the ground support equipment,

and added an extra hour of buffer time

into the countdown to allow more room for troubleshooting.

It's the kind of painstaking, un-glamorous engineering work

that rarely makes headlines,

but it's exactly what keeps astronauts alive.

Today's rehearsal targets a simulated launch window opening

at 8.30 this evening, Eastern time.

The test is expected to run until around 12.30 Friday morning

and the stakes are high.

NASA has said it won't set a formal launch date

until after a successful wet dress rehearsal campaign.

March 6th remains the earliest possible crude launch date.

NASA Administrator Jared Isaacman put it well

when he said, we anticipated encountering challenges

that is precisely why we conduct a wet dress rehearsal.

These tests are designed to surface issues before flight.

The safety of the crew comes first.

So tonight, we watch and we wait.

We will be keeping a close eye on this one

and will bring you the results in tomorrow's episode.

Fingers crossed for a clean test.

No leaks and a March launch that puts humans

back in the vicinity of the moon

for the first time in over 50 years.

All right, from a rocket at Kennedy Space Center

to the absolute heart of our galaxy.

And this story is one of those discoveries

that if it's confirmed, could fundamentally change

how we understand the universe.

Researchers from Columbia University

working with the Breakthrough Listen Initiative,

which is best known for searching

for signs of intelligent life beyond Earth,

have announced the detection of a candidate millisecond pulsar

very close to Sagittarius A star.

That's the supermassive black hole sitting

at the center of the Milky Way,

roughly four million times the mass of our own sun.

So let's unpack what a pulsar is

because it's one of the most extraordinary objects

in the universe.

When a massive star reaches the end of its life

and explodes as a supernova,

what's left behind is an incredibly dense core

called a neutron star.

Some of those neutron stars spin rapidly

and emit beams of radio waves

like a cosmic lighthouse sweeping through space.

When those beams sweep past Earth,

we detect them as regular pulses, hence pulsar.

And what makes millisecond pulsar special

is their extraordinary precision.

They spin hundreds of times per second

with almost perfect regularity.

Scientists have called them the most accurate clocks

in the universe,

more stable than atomic clocks here on Earth.

This candidate, nicknamed BLPSR,

completes one full rotation every 8.19 milliseconds.

Now, here's why finding one near Sagittarius A star

is such a big deal.

A pulsar next to a 4 million solar mass black hole

would be operating in one of the most extreme

gravitational environments imaginable.

And Einstein's general theory of relativity

makes very specific predictions

about what happens to space and time

in such extreme environments.

Predictions that have never been tested

at this level of precision.

And if a pulsar is orbiting close to Sagittarius A star,

the black hole's gravity would warp space times so severely

that those precise pulsar pulses

would arrive at our telescopes with tiny,

but measurable distortions.

As researchers love co-bognav from Columbia put it,

any external influence on a pulsar

would introduce anomalies in the steady arrival of pulses,

which can be measured and modeled.

In other words, a confirmed pulsar next to a supermassive

black hole would be a natural laboratory

for testing Einstein's gearies

in the most extreme conditions possible.

It could also help us understand things

like the mass of Sagittarius A star,

the geometry of space time near a supermassive black hole,

and potentially even offer clues about dark matter.

Now, it's important to be clear,

this is still a candidate.

The team published their findings

in the astrophysical journal and breakthrough listen

has released all the observational data publicly.

So researchers around the world

can do independent analyses.

Confirmation will require extensive follow-up observations,

but the scientific community is buzzing.

This is the kind of discovery

that reshapes entire research programs if it holds up.

Keep watching the skies and the galactic center.

This story is far from over.

So we've talked about what's happening in Florida tonight

and what might be happening at the center of our galaxy.

Now let's zoom all the way out.

Farther than you've probably ever thought about,

and ask, how does the universe end?

For most of the past few decades,

the scientific consensus has been pretty clear.

The universe expands forever.

Dark energy, that mysterious force

making up roughly 68% of all the mass and energy

in the cosmos, was thought to be a constant,

relentlessly pushing everything apart.

Eventually, galaxies would drift so far from each other

that the night sky would go dark.

Stars would burn out.

Everything would fade into a cold, silent void.

Scientists call this the big freeze or heat death.

But new data is challenging that picture in a dramatic way.

Physicist Henry Tai at Cornell University

has published new calculations using data

from two of the world's most powerful dark energy

observatories, the dark energy survey in Chile

and the dark energy spectroscopic instrument in Arizona.

And his conclusion is striking.

The universe may be heading not for a freeze,

but for a crunch.

Here's how it works.

Both surveys are finding evidence

that dark energy isn't actually constant.

It appears to be weakening over time.

If that's true, then the force pushing the universe apart

is gradually fading.

And at some point, gravity takes over.

The expansion slows, stops, and then reverses.

Everything that has been flying apart

for billions of years begins falling back together.

A Tai's model introduces a hypothetical particle

called an ultralight axion,

combined with what's known as a negative cosmological constant

to explain how dark energy could behave this way.

The math suggests the universe is currently

about 13.8 billion years old and approaching

the halfway point of its total lifespan.

It would continue expanding for roughly

another 11 billion years, reach its maximum size,

and then begin to contract, ultimately collapsing

into a single point of unimaginable density.

The big crunch, total elapsed time,

approximately 33 billion years.

Now, before anyone starts updating their bucket list,

this is one model.

It's not yet scientific consensus.

There's healthy debate about how to interpret

the dark energy data and upcoming missions

from the European Space Agency's Euclid Telescope,

NASA's FIREX project, and the Veracirubin Observatory

will provide much better measurements over the coming years.

But the very fact that two independent observatories,

one in the southern hemisphere, one in the northern,

are converging on similar results

about dark energy evolving, that's significant.

As Tai himself put it, for the last 20 years,

people believed the universe would expand forever.

The new data may be telling us something very different.

The universe might be mortal after all.

Quite the thought to sit with on a Thursday evening.

And now, because apparently one existential revelation

isn't enough for one episode,

let's talk about city-killer asteroids.

Those two words together are doing a lot of work.

They really are.

So at the American Association for the Advancement

of Science Conference in Arizona this week,

NASA's Planetary Defense Officer,

and yes, that is a real job title,

Dr. Kelly Fast gave a presentation

that's been making headlines ever since,

and for good reason.

Dr. Fast explained that when it comes to asteroids,

there are essentially three categories of concern.

At the small end, things are hitting Earth all the time.

Meteors burning up in the atmosphere, the occasional fireball.

We're not particularly worried about those.

At the large end, the extinction level rocks,

the movie asteroid kind,

scientists are actually fairly confident about where those are.

We track them, we know their orbits.

It's the middle ground that keeps Dr. Fast up at night.

Asteroids in the range of 140 meters and larger,

large enough to devastate an entire city or a wide region,

but small enough to be difficult to detect

with current telescopes.

Her estimate, there are around 25,000 of these objects

in the vicinity of Earth's orbit.

And how many have we found?

About 40%.

Meaning there are potentially 15,000 city-killing space rocks

out there right now that we simply do not know about.

To add some context to that,

and to the challenge of actually doing something about it,

if we did spot one, Dr. Nancy Shabbat,

the planetary scientist who led NASA's Dart mission,

the spacecraft that successfully changed the orbit

of an asteroid back in 2022, was also at the conference.

She pointed out that Dart was a breakthrough demonstration,

but there isn't another one sitting on a launch pad

ready to go.

She specifically referenced the asteroid YR4,

which caused some anxiety earlier this year

with a small but not zero probability

of a lunar impact in 2032.

She said, if something like YR4 had been headed towards the Earth,

we would not have any way to go and deflect it actively

right now.

The hope on the horizon is the near-earth object

surveyor telescope, which is planned for launch next year.

Unlike conventional optical telescopes,

it uses thermal infrared signatures

to detect darker asteroids that are essentially invisible

to conventional instruments, potentially

a game changer for the detection side of the problem.

But Dr. Shabbat's point stands.

Detection is one thing.

Having an active ready-to-deploy deflection capability

is another, and that investment, she says,

is simply not being made at the level that needs to be.

Something worth thinking about, given that planetary defense

is probably the one area of space science

that is quite literally about survival.

Sobering stuff, let's come back down to Earth for a moment,

or rather, let's look up from it.

Here's something wonderful and wonderfully timely,

because this one is happening right now,

tonight, as you listen to this.

Mercury, the innermost planet of our solar system,

and the one most people have never actually seen

with their own eyes, is tonight reaching

what astronomers call its greatest eastern elongation.

That's the point in its orbit,

where it's at its maximum angular distance

from the sun as seen from Earth,

meaning it appears as far from the sun in our sky

as it ever gets.

And why does that matter for observers?

Because Mercury is normally incredibly difficult to spot.

It's always close to the sun in the sky,

so you're either trying to catch it just before sunrise

or just after sunset, with very little time

before it follows the sun below the horizon.

But at greatest elongation, you get the best window.

Tonight, look to the western horizon

shortly after sunset.

Mercury will be visible as a moderately bright point of light,

shining steadily rather than twinkling like a star.

You won't need any special equipment,

though binoculars will give you a much nicer view.

This is Mercury's first greatest elongation of 2026,

and the best evening viewing opportunity

will get for the year so far.

There's also a bonus tonight.

The crescent moon, Saturn, and Neptune

are all gathering in the same part of the sky.

With Saturn and Neptune very close together

near the western horizon.

Now Neptune will need a telescope,

and you'll need to wait until the sun is fully set.

Do not point any optical instrument

toward the horizon until the sun has cleared it completely.

But the overall scene is really quite beautiful this evening.

And for those of you keeping track

of the upcoming six planet parade on the 28th of February,

Mercury reaching greatest elongation tonight

is actually a key milestone in that buildup.

By the 28th, Mercury will have improved its position

enough to join Venus, Saturn, Jupiter, Uranus, and Neptune,

all visible in the same sky.

We'll have a full guide to that event closer to the date.

But tonight is your preview.

Go look west.

And now to close out the episode,

we have something that we absolutely love,

a reminder that even on a space station in orbit,

humans will find a way to celebrate.

The crew of China's Shenzu 21 mission,

currently living and working aboard the Tiangong space station,

have released a music video to mark the lunar new year,

the year of the horse, and honestly, it is delightful.

Filming a music video in microgravity is, as you might imagine,

a unique creative challenge.

Everything floats, hair floats, props float,

but the crew apparently embraced all of it.

And the result is one of those lovely, warm, deeply human moments

that cuts right through all the geopolitical complexity

of the space race and reminds you

that the people up there are just people,

celebrating a holiday with their families watching from below.

Tiangong, which means heavenly palace,

currently has a crew of three aboard,

following the Shenzu 21 mission.

China has been steadily expanding its space station program,

and moments like this one, shared with the world,

are a reminder of why humans go to space in the first place,

not just for science or national prestige,

but for the sheer joy of being up there.

Dongxi Fachaie to all of our listeners

celebrating the lunar new year.

May the year of the horse bring you good fortune

and hopefully fewer hydrogen leaks.

And on that note, that's your astronomy daily

for Thursday, February 19th, 2026.

What a lineup today, a live rocket fueling test,

a cosmic clock near a black hole,

the possible end of the universe, city killing asteroids,

Mercury in the evening sky, and a music video from orbit.

If you wanna follow along with the Artemis II fueling test

tonight, NASA has a live stream at nasa.gov.

We'll link everything in the show notes.

And if you spot Mercury tonight,

tag us on social media at Astro DailyPod.

We would love to see your photos.

Subscribe, leave a review if you're enjoying the show,

and we will be back tomorrow with the results

of tonight's fueling test.

Until then, keep looking up.

Clear skies, everyone.

The astronomy day, the star is the toe.

The star is the toe.

The star is the toe.

The star is the toe.

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