Speaker 1: You're listening to Astronomy Daily.
Speaker 2: I'm Anna and I'm Avery. It is Saturday, the seventh
of March twenty twenty six, and as usual, we have
a packed show for you today.
Speaker 1: We absolutely do. Here's a question to get you thinking.
Back in September twenty twenty two, NASA slammed a spacecraft
into an asteroid. You probably remember that, but did you
know that we only just confirmed something remarkable. That impact
didn't just nudge the asteroid, It actually changed the orbit
of an entire asteroid system around the Sun.
Speaker 2: For the first time in human history, we move the
celestial body's solar orbit. And that's just story one. We've
also got gravitational waves, a spacecraft emergency, an orbit, a
forty five year old theory biting the dust, our young
Sun blowing its very first cosmic bubble, and the gorgeous
double planet show. Intonight, sky, let's go.
Speaker 1: So let's kick off with the dark story, and I
think it deserves a moment to really sync in. We
already knew that Dart was a success. We knew it
shortened the orbit of dimorphous around its partner asteroid Ditamos
by about thirty three minutes. That was confirmed back in
twenty twenty two, but a new study published yesterday in
the journal Science Advances has revealed something even bigger.
Speaker 2: Right, because ditamos and dimorphous are gravitationally linked, they moved together,
and researchers have now confirmed that the debris blasted off
Dimorphous during that impact was so enormous We're talking over
a million kilograms of rock and dust, that it gave
the whole binary system an extra kick.
Speaker 1: And that extra kick was measurable. The orbital period of
the entire Ditamo system around the Sun shortened by zero
point one point five seconds. Now, I know that sounds tiny,
but this is the first time a human made object
has measurably changed the path of a celestial body around
our star.
Speaker 2: To even measure that, the team had to get incredibly creative.
They tracked what are called stellar occultations, moments when the
asteroid passes in front of a background star and briefly
blocks its light. Volunteers around the world contributed twenty two
of these observations between October twenty twenty two and March
twenty twenty five. Twenty two pinpoint moments of a star
blinking out and from those They derived the change of
zero point fifteen seconds in a seven hundred seventy day
solar orbit.
Speaker 1: The momentum enhancement factor turned out to be about two,
meaning the debris ejected by the impact roughly doubled the
total push given to the asteroid. Dart didn't just hit dimorphos,
it turned a dimorphous into a rocket, and.
Speaker 2: Thomas Statler, leads Sciences for Solar System Small Bodies at
NASA Headquarters, framed it perfectly. He said, a tiny change can,
and given enough time, grow into a significant deflection. This
result validates kinetic impact as a genuine planetary defense technique,
not just for nudging a moon, but for altering the
path of an entire binary system around the Sun.
Speaker 1: Lisas harrispacecraft, which launched in twenty twenty four, is expected
to arrive at the Ditamo system later this year to
study the aftermath of close, though the science from this
impact is very much still unfolding.
Speaker 2: Story two and it is a landmark one. The LGO
Virgocagra collaboration the LVK has just published the fourth edition
of the Gravitational Wave Transient Catalog known as GWTC four,
and the headline they've more than doubled the total number
of gravitational wave detections ever made.
Speaker 1: Before this release, the entire catalog contained ninety candidates from
three previous observing runs stretching back to twenty fifteen. New
catalog adds one hundred and twenty eight new events, all
detected during just the first nine months of the fourth
observing run between May twenty twenty three and January twenty
twenty four.
Speaker 2: So we've gone from ninety to two hundred and eighteen
in one update. And it's not just the quantity that's exciting,
it's the variety. The catalog includes the heaviest black hole
binary merger ever detected, with each black hole weighing in
at around one hundred and thirty times the mass of
our Sun.
Speaker 1: There's also a binary where both black holes are spinning
at roughly forty percent the speed of light, and there
are two new mixed mergers, a black hole colliding with
a neutron star. Each one of those is a treasure
trove for astrophysics.
Speaker 2: Daniel Williams, a researcher at the University of Glasgow and
LVK member, put it well. He said they're pushing into
new parts of parameter space, seeing things that are more massive,
spinning faster, and more astrophysically unusual than anything detect before.
Speaker 1: What I love about this is what it means for
testing Einstein. The catalog includes an event with one of
the loudest gravitational wave signals ever recorded GW two three
zero eight one four, and the team used it to
run precision tests of general relativity. It passed with flying colors,
but the fact that we're now running those tests on
events this extreme is remarkable.
Speaker 2: Bigro and its partners are currently in a maintenance break,
but a new six month observing run is expected to
begin in late twenty twenty six. Given how rapidly the
catalog is growing, that run could double it again.
Speaker 1: All right, story three, and this one has a genuine
element of suspense. Europe's Proba three mission is in trouble.
Issa confirmed yesterday that they have lost contact with one
of the two spacecraft that make up the Proba three mission.
Speaker 2: Let me explain what Proba three actually is, because it's
a fascinating concept. It launched from India back in December
twenty two, twenty four, and it consists of two separate
spacecraft designed to fly in extraordinarily precise formation about one
hundred and fifty meters apart. To create artificial solar eclipses
in space.
Speaker 1: One spacecraft, the occult, physically blocks the bright face of
the Sun. The other, the coronagraph, uses that shadow to
image the Sun's faint outer atmosphere, the corona, without being
blinded by the solar disc. And to make this work,
the two spacecraft must maintain alignment to within millimeter accuracy.
Speaker 2: It's an almost absurdly precise operation, and it was working.
In May of last year. The spacecraft achieved their landmark
formation flying test. In June, they captured the first ever
images of an artificial solar eclipse in space. It was
a genuine technological first.
Speaker 1: And then on the weekend of February fourteenth, something went wrong.
The CORONAFT spacecraft, the one doing the imaging experience hinst
an anomaly that prevented it from entering safe mode. Issa
describes it as a progressive loss of attitude. In other words,
the spacecraft slowly lost its orientation.
Speaker 2: As it drifted. Its solar panels moved away from the Sun,
the batteries drained, the spacecraft dropped into survival mode and
contact was lost. ESA says root cause is under investigation,
and they're exploring whether the companion occult or spacecraft can
be maneuvered closer to assist in recovery.
Speaker 1: Losing either spacecraft would effectively end the probe of three mission.
ESA says teams are working hard and they will provide
updates as new information becomes available. This is very much
a developing story. We'll keep following it.
Speaker 2: Story four is a classic example of a long held
scientific belief getting overturned. For forty five years, astronomers thought
they understood how stars like our Sun change as they age,
specifically how their rotation pattern evolved.
Speaker 1: The idea this our Sun rotates differentially. The equator takes
about twenty five days to complete one full rotation, while
the poles take about thirty five days. Equator faster, poles slower.
That's called solar type differential rotation, and scientists believed that
as stars slowed down over billions of years, they would
eventually flip the poles would start spinning faster than the
equator instead.
Speaker 2: That flip state was called antisolar differential rotation. Theoretical simulations
predicted it. No one had ever observed it, but the
model said it should happen, and for decades the lack
of observations was attributed to limitations in our telescope technology.
Speaker 1: But now researchers at Nagoya University in Japan have used Fugaku,
the country's most powerful supercomputer, to run the most detailed
simulations ever of stellar interiors, and the result is clear.
The flip doesn't happen.
Speaker 2: Key was resolution. Previous simulations were low resolution, and magnetic
fields faded out of the models entirely. At high resolution,
we're talking five point four billion grid points per simulated star,
the magnetic field stayed strong, and those magnetic fields, it
turns out, are what prevent the rotation from flipping.
Speaker 1: Professor Heidiyuki Haata, one of the co authors, set it simply,
turbulence and magnetism keep the equator spinning faster than the
poles throughout the star's life. The switch doesn't happen because
magnetic fields, which previous simulations missed, prevent it.
Speaker 2: And there's a bonus finding magnetic fields in solar type
stars weaken continuously throughout their lifetime with no revival In
old age, previous models had predicted a magnetic comeback that
doesn't happen either.
Speaker 1: This matters practically too. A corrected model of stellar rotation
helps us better understand the Sun's eleven year sunspot cycle
and could improve our predictions of how magnetic activity affects
the habitability of planets orbiting Sun like stars over billions
of years.
Speaker 2: Dory five and it's a lovely one. A real window
into our own Sun's distant past. NASA's Chandra X ray
observatory has captured the very first image of what's called
an astrosphere around the sun like star.
Speaker 1: Our Sun has a protective bubble around it, called the heliosphere,
created by the solar wind streaming outward and carving out
a cavity in interstellar space. It's enormous. It extends far
beyond the outer planets and shields the Solar System from
harmful galactic cosmic rays, but we've never been able to
photograph it from the outside.
Speaker 2: The star Chandra observed is called HD sixty one zero
zero five, and it sits about one hundred and twenty
light years away in the constellation Pupis. It has roughly
the same mass and temperature as our Sun, but it's
only about one hundred million years old. Our Sun is
around five billion years old, so HD six one zero
zero five is cosmically speaking a baby, and because.
Speaker 1: It's so young, its stellar wind is dramatically more powerful.
It blows about three times faster, and it's twenty five
times denser than the wind from our Sun today. That's
why its astrosphere is bright enough to detect an X rays.
The powerful wind collides with the surrounding interstellar dust and gas,
and that collision produces X ray emission that Chandra can detect.
Speaker 2: The astrosphere has a diameter roughly two hundred times the
distance between Earth and the Sun. Carry Lists of Johns
Hopkins University, who led the study, put it beautifully, We've
been studying our Son's heliosphere for decades, but we can
never see it from the outside. This is the closest
thing we have to a photograph of what our own
Sun's bubble look like several billion years ago.
Speaker 1: The star is also nicknamed the Moth because a surrounding
disc of dust forms a mothlike structure around it, and interestingly,
the dense dusty environment is actually part of why the
astrosphere is so visible here, making HD six one zero
zero five a uniquely ideal subject for this kind of observation.
Speaker 2: And we'll finish with some skywatching news because tonight and
tomorrow night offer something quite special. Venus and Saturn are
meeting up in the evening sky, and it's a treat
for anyone who can get outside shortly after sunset.
Speaker 1: Venus is already impossible to miss right now. It's shining
at magnitude minus three point nine, which makes it by
far the brightest object in the sky after the Sun
and moon. Tonight and tomorrow, Saturn sits close alongside it,
though considerably fainter at magnitude one point zero.
Speaker 2: The best time to look is about thirty minutes after sunset,
when Venus will be roughly seven degrees above the western horizon.
Binoculars will help a lot. Saturn should pop into view
easily near brilliant Venus. You'll have about seventy minutes before
both planets set, and.
Speaker 1: If you're pointing a telescope at Venus tonight, you're in
for an extra treat. The planet is currently showing a
ninety seven percent lit disc, almost fully illuminated from our perspective.
It's a gorgeous site. Neptune is also lurking nearby, just
over a degree from Saturn, though you'll need a telescope
to catch that one.
Speaker 2: So get outside this evening. If skies are clear, Venus
is your guide. Find that brilliant white beacon low in
the west, and Saturn will be right there waiting for you.
Speaker 1: And that's our show for today. Six stories from an
asteroid nudged around the Sun to a planet pairing up
Intonight's sky. It's a great time to be paying attention
to the universe.
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keep looking up clear skies, everyone.
Speaker 2: Sunday Starsz Starz