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Speaker 1: You're listening to Astronomy Daily.

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Speaker 2: I'm Anna and I'm Avery. It is Saturday, the seventh

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of March twenty twenty six, and as usual, we have

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a packed show for you today.

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Speaker 1: We absolutely do. Here's a question to get you thinking.

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Back in September twenty twenty two, NASA slammed a spacecraft

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into an asteroid. You probably remember that, but did you

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know that we only just confirmed something remarkable. That impact

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didn't just nudge the asteroid, It actually changed the orbit

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of an entire asteroid system around the Sun.

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Speaker 2: For the first time in human history, we move the

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celestial body's solar orbit. And that's just story one. We've

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also got gravitational waves, a spacecraft emergency, an orbit, a

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forty five year old theory biting the dust, our young

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Sun blowing its very first cosmic bubble, and the gorgeous

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double planet show. Intonight, sky, let's go.

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Speaker 1: So let's kick off with the dark story, and I

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think it deserves a moment to really sync in. We

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already knew that Dart was a success. We knew it

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shortened the orbit of dimorphous around its partner asteroid Ditamos

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by about thirty three minutes. That was confirmed back in

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twenty twenty two, but a new study published yesterday in

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the journal Science Advances has revealed something even bigger.

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Speaker 2: Right, because ditamos and dimorphous are gravitationally linked, they moved together,

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and researchers have now confirmed that the debris blasted off

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Dimorphous during that impact was so enormous We're talking over

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a million kilograms of rock and dust, that it gave

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the whole binary system an extra kick.

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Speaker 1: And that extra kick was measurable. The orbital period of

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the entire Ditamo system around the Sun shortened by zero

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point one point five seconds. Now, I know that sounds tiny,

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but this is the first time a human made object

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has measurably changed the path of a celestial body around

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our star.

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Speaker 2: To even measure that, the team had to get incredibly creative.

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They tracked what are called stellar occultations, moments when the

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asteroid passes in front of a background star and briefly

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blocks its light. Volunteers around the world contributed twenty two

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of these observations between October twenty twenty two and March

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twenty twenty five. Twenty two pinpoint moments of a star

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blinking out and from those They derived the change of

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zero point fifteen seconds in a seven hundred seventy day

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solar orbit.

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Speaker 1: The momentum enhancement factor turned out to be about two,

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meaning the debris ejected by the impact roughly doubled the

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total push given to the asteroid. Dart didn't just hit dimorphos,

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it turned a dimorphous into a rocket, and.

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Speaker 2: Thomas Statler, leads Sciences for Solar System Small Bodies at

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NASA Headquarters, framed it perfectly. He said, a tiny change can,

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and given enough time, grow into a significant deflection. This

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result validates kinetic impact as a genuine planetary defense technique,

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not just for nudging a moon, but for altering the

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path of an entire binary system around the Sun.

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Speaker 1: Lisas harrispacecraft, which launched in twenty twenty four, is expected

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to arrive at the Ditamo system later this year to

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study the aftermath of close, though the science from this

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impact is very much still unfolding.

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Speaker 2: Story two and it is a landmark one. The LGO

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Virgocagra collaboration the LVK has just published the fourth edition

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of the Gravitational Wave Transient Catalog known as GWTC four,

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and the headline they've more than doubled the total number

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of gravitational wave detections ever made.

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Speaker 1: Before this release, the entire catalog contained ninety candidates from

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three previous observing runs stretching back to twenty fifteen. New

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catalog adds one hundred and twenty eight new events, all

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detected during just the first nine months of the fourth

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observing run between May twenty twenty three and January twenty

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twenty four.

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Speaker 2: So we've gone from ninety to two hundred and eighteen

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in one update. And it's not just the quantity that's exciting,

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it's the variety. The catalog includes the heaviest black hole

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binary merger ever detected, with each black hole weighing in

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at around one hundred and thirty times the mass of

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our Sun.

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Speaker 1: There's also a binary where both black holes are spinning

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at roughly forty percent the speed of light, and there

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are two new mixed mergers, a black hole colliding with

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a neutron star. Each one of those is a treasure

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trove for astrophysics.

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Speaker 2: Daniel Williams, a researcher at the University of Glasgow and

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LVK member, put it well. He said they're pushing into

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new parts of parameter space, seeing things that are more massive,

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spinning faster, and more astrophysically unusual than anything detect before.

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Speaker 1: What I love about this is what it means for

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testing Einstein. The catalog includes an event with one of

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the loudest gravitational wave signals ever recorded GW two three

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zero eight one four, and the team used it to

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run precision tests of general relativity. It passed with flying colors,

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but the fact that we're now running those tests on

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events this extreme is remarkable.

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Speaker 2: Bigro and its partners are currently in a maintenance break,

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but a new six month observing run is expected to

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begin in late twenty twenty six. Given how rapidly the

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catalog is growing, that run could double it again.

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Speaker 1: All right, story three, and this one has a genuine

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element of suspense. Europe's Proba three mission is in trouble.

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Issa confirmed yesterday that they have lost contact with one

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of the two spacecraft that make up the Proba three mission.

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Speaker 2: Let me explain what Proba three actually is, because it's

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a fascinating concept. It launched from India back in December

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twenty two, twenty four, and it consists of two separate

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spacecraft designed to fly in extraordinarily precise formation about one

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hundred and fifty meters apart. To create artificial solar eclipses

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in space.

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Speaker 1: One spacecraft, the occult, physically blocks the bright face of

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the Sun. The other, the coronagraph, uses that shadow to

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image the Sun's faint outer atmosphere, the corona, without being

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blinded by the solar disc. And to make this work,

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the two spacecraft must maintain alignment to within millimeter accuracy.

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Speaker 2: It's an almost absurdly precise operation, and it was working.

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In May of last year. The spacecraft achieved their landmark

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formation flying test. In June, they captured the first ever

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images of an artificial solar eclipse in space. It was

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a genuine technological first.

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Speaker 1: And then on the weekend of February fourteenth, something went wrong.

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The CORONAFT spacecraft, the one doing the imaging experience hinst

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an anomaly that prevented it from entering safe mode. Issa

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describes it as a progressive loss of attitude. In other words,

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the spacecraft slowly lost its orientation.

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Speaker 2: As it drifted. Its solar panels moved away from the Sun,

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the batteries drained, the spacecraft dropped into survival mode and

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contact was lost. ESA says root cause is under investigation,

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and they're exploring whether the companion occult or spacecraft can

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be maneuvered closer to assist in recovery.

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Speaker 1: Losing either spacecraft would effectively end the probe of three mission.

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ESA says teams are working hard and they will provide

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updates as new information becomes available. This is very much

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a developing story. We'll keep following it.

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Speaker 2: Story four is a classic example of a long held

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scientific belief getting overturned. For forty five years, astronomers thought

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they understood how stars like our Sun change as they age,

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specifically how their rotation pattern evolved.

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Speaker 1: The idea this our Sun rotates differentially. The equator takes

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about twenty five days to complete one full rotation, while

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the poles take about thirty five days. Equator faster, poles slower.

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That's called solar type differential rotation, and scientists believed that

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as stars slowed down over billions of years, they would

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eventually flip the poles would start spinning faster than the

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equator instead.

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Speaker 2: That flip state was called antisolar differential rotation. Theoretical simulations

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predicted it. No one had ever observed it, but the

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model said it should happen, and for decades the lack

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of observations was attributed to limitations in our telescope technology.

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Speaker 1: But now researchers at Nagoya University in Japan have used Fugaku,

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the country's most powerful supercomputer, to run the most detailed

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simulations ever of stellar interiors, and the result is clear.

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The flip doesn't happen.

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Speaker 2: Key was resolution. Previous simulations were low resolution, and magnetic

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fields faded out of the models entirely. At high resolution,

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we're talking five point four billion grid points per simulated star,

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the magnetic field stayed strong, and those magnetic fields, it

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turns out, are what prevent the rotation from flipping.

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Speaker 1: Professor Heidiyuki Haata, one of the co authors, set it simply,

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turbulence and magnetism keep the equator spinning faster than the

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poles throughout the star's life. The switch doesn't happen because

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magnetic fields, which previous simulations missed, prevent it.

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Speaker 2: And there's a bonus finding magnetic fields in solar type

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stars weaken continuously throughout their lifetime with no revival In

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old age, previous models had predicted a magnetic comeback that

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doesn't happen either.

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Speaker 1: This matters practically too. A corrected model of stellar rotation

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helps us better understand the Sun's eleven year sunspot cycle

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and could improve our predictions of how magnetic activity affects

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the habitability of planets orbiting Sun like stars over billions

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of years.

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Speaker 2: Dory five and it's a lovely one. A real window

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into our own Sun's distant past. NASA's Chandra X ray

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observatory has captured the very first image of what's called

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an astrosphere around the sun like star.

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Speaker 1: Our Sun has a protective bubble around it, called the heliosphere,

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created by the solar wind streaming outward and carving out

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a cavity in interstellar space. It's enormous. It extends far

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beyond the outer planets and shields the Solar System from

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harmful galactic cosmic rays, but we've never been able to

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photograph it from the outside.

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Speaker 2: The star Chandra observed is called HD sixty one zero

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zero five, and it sits about one hundred and twenty

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light years away in the constellation Pupis. It has roughly

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the same mass and temperature as our Sun, but it's

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only about one hundred million years old. Our Sun is

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around five billion years old, so HD six one zero

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zero five is cosmically speaking a baby, and because.

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Speaker 1: It's so young, its stellar wind is dramatically more powerful.

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It blows about three times faster, and it's twenty five

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times denser than the wind from our Sun today. That's

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why its astrosphere is bright enough to detect an X rays.

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The powerful wind collides with the surrounding interstellar dust and gas,

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and that collision produces X ray emission that Chandra can detect.

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Speaker 2: The astrosphere has a diameter roughly two hundred times the

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distance between Earth and the Sun. Carry Lists of Johns

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Hopkins University, who led the study, put it beautifully, We've

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been studying our Son's heliosphere for decades, but we can

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never see it from the outside. This is the closest

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thing we have to a photograph of what our own

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Sun's bubble look like several billion years ago.

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Speaker 1: The star is also nicknamed the Moth because a surrounding

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disc of dust forms a mothlike structure around it, and interestingly,

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the dense dusty environment is actually part of why the

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astrosphere is so visible here, making HD six one zero

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zero five a uniquely ideal subject for this kind of observation.

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Speaker 2: And we'll finish with some skywatching news because tonight and

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tomorrow night offer something quite special. Venus and Saturn are

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meeting up in the evening sky, and it's a treat

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for anyone who can get outside shortly after sunset.

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Speaker 1: Venus is already impossible to miss right now. It's shining

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at magnitude minus three point nine, which makes it by

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far the brightest object in the sky after the Sun

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and moon. Tonight and tomorrow, Saturn sits close alongside it,

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though considerably fainter at magnitude one point zero.

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Speaker 2: The best time to look is about thirty minutes after sunset,

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when Venus will be roughly seven degrees above the western horizon.

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Binoculars will help a lot. Saturn should pop into view

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easily near brilliant Venus. You'll have about seventy minutes before

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both planets set, and.

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Speaker 1: If you're pointing a telescope at Venus tonight, you're in

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for an extra treat. The planet is currently showing a

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ninety seven percent lit disc, almost fully illuminated from our perspective.

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It's a gorgeous site. Neptune is also lurking nearby, just

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over a degree from Saturn, though you'll need a telescope

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to catch that one.

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Speaker 2: So get outside this evening. If skies are clear, Venus

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is your guide. Find that brilliant white beacon low in

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the west, and Saturn will be right there waiting for you.

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Speaker 1: And that's our show for today. Six stories from an

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asteroid nudged around the Sun to a planet pairing up

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Intonight's sky. It's a great time to be paying attention

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to the universe.

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Speaker 2: If you enjoyed today's episode, please subscribe wherever you're listening

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and leave us a rating or review. It genuinely helps

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a show reach more people.

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Speaker 1: You can find us at Astronomy Daily dot io for

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the blog and show notes, and follow us at astro

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Daily Pod on all the major social platforms. Until Monday,

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keep looking up clear skies, everyone.

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Speaker 2: Sunday Starsz Starz