Lunar Secret Unveiled, Galactic Waves Discovered, and SpaceX's Starship Countdown

0:00 Avery: Welcome to Astronomy Daily, the podcast that

0:03 brings you the universe, one story at a time.

0:05 I'm Avery.

0:06 Anna: And I'm Anna. Today we're journeying

0:09 from our own cosmic backyard to the

0:12 vast structures of our galaxy.

0:14 Avery: That's right. We'll be looking at surprising

0:16 new data from the Moon's far side. A

0:19 colossal wave of stars discovered in the

0:21 Milky Way, and an update on SpaceX's next

0:24 big launch.

0:25 Anna: And we'll wrap up with a look at the

0:27 invisible asteroids lurking closer to the

0:30 Sun. A potential threat yet we're only just

0:32 beginning to understand. Let's get started.

0:35 Avery: First up, Anna, uh, let's talk about the

0:37 Moon. We tend to think of it as this static,

0:40 unchanging rock. But China's Chang'

0:42 E6 mission is telling us a different story.

0:45 Anna: It certainly is. The rock and soil samples

0:48 returned from the far side are revealing a

0:50 fascinating thermal asymmetry. In

0:53 simple terms, the interior of the Moon's far

0:56 side, the side we never see from Earth, is

0:59 significantly cooler than the near side.

1:02 Avery: Cooler. How much cooler are we talking?

1:04 Anna: Around 180 degrees Fahrenheit

1:07 or 100 degrees Celsius cooler? That

1:10 might not sound like a huge number on a

1:12 planetary scale, but it's enough to explain

1:14 some long standing mysteries about the Moon's

1:17 two faces.

1:18 Avery: Like why the near side is covered in those

1:20 dark volcanic plains, the maria. While

1:23 the far side is so much more rugged and

1:25 cratered.

1:26 Anna: Exactly. A hotter nearside mantle would

1:29 have been more molten, leading to more

1:31 widespread and prolonged volcanic activity.

1:34 This heat also explains why the near side

1:36 crust is thinner. The cooler far side mantle

1:39 solidified earlier, resulting in a thicker

1:41 crust and far less volcanism.

1:43 Avery: So the big question is why? Why

1:46 would one side be so much hotter than the

1:49 other?

1:49 Anna: That's the billion dollar question. The

1:51 leading hypothesis is an uneven distribution

1:54 of heat producing radioactive elements like

1:57 uranium and thorium. For some reason,

2:00 these elements were concentrated on the near

2:02 side when the Moon was forming.

2:04 Avery: And how would that have happened?

2:05 Anna: There are a couple of compelling theories.

2:08 One suggests that a massive ancient impact

2:10 could have essentially splattered these

2:12 elements across one hemisphere. Another,

2:15 more dramatic theory posits that early in its

2:18 history, Earth had two moons and a

2:21 smaller companion moon had a slow motion

2:24 collision with the larger one, depositing its

2:27 element rich material onto what is now the

2:29 MIR side.

2:30 Avery: Wow. So the face of the Moon we see every

2:33 night might actually be the result of a

2:35 cosmic fender bender. It really highlights

2:37 how dynamic and violent the early solar

2:40 system was.

2:41 A truly incredible discovery from the Chang'

2:43 E6 mission.

2:45 Anna: From our closest neighbor to the grand scale

2:47 of our entire galaxy. Avery. Data

2:50 from the European Space Agency's Gaia space

2:53 telescope has revealed something truly

2:55 monumental.

2:57 Avery: Gaia is always turning up amazing things.

2:59 What has it found this time?

3:01 Anna: It's been described as a great wave of

3:03 stars. A colossal ripple moving

3:06 outwards from the center of the Milky Way.

3:08 We're talking about a structure that spans

3:10 tens of thousands of light years.

3:12 Avery: A wave of stars. What does that even

3:15 look like? Are the stars themselves moving in

3:18 a wave pattern, like water?

3:19 Anna: In a way, yes. This isn't a wave of light,

3:22 but a literal wave of motion. The

3:25 collective positions and velocities of

3:27 millions of stars. Stars are perturbed,

3:30 causing them to move up and down as this

3:32 ripple propagates through the galactic disk.

3:34 It's a subtle effect, but on a galactic

3:37 scale, it's enormous.

3:39 Avery: That's mind boggling. A wave that's tens

3:42 of thousands of light years across. What

3:44 could possibly cause something that huge?

3:47 Anna: The most likely culprit is a collision. Not a

3:50 recent one, but an event that happened

3:52 perhaps a few billion years ago. The thinking

3:54 is that a dwarf galaxy plunged through

3:57 the center of the Milky.

3:59 Avery: Way's disk like drop a stone into a pond.

4:01 But the pond is our galaxy, and the stone

4:04 is another, smaller galaxy.

4:06 Anna: That's the perfect analogy. The dwarf

4:09 galaxy's gravity would have punched through

4:11 the disk, setting off these ripples that

4:14 are still expanding outwards today.

4:17 It's a testament to the power of big data

4:20 in astronomy. By mapping out the 3D

4:23 motion of billions of stars, we can

4:26 uncover these hidden dynamics.

4:28 Avery: And does this wave affect us here in our

4:31 solar system?

4:32 Anna: That's a great question. We are likely caught

4:35 up in this wave, just like all the other

4:37 stars in our neighborhood. The effect on our

4:40 solar system's orbit is probably very small,

4:44 but it's a powerful reminder that we are part

4:46 of a much larger dynamic system

4:50 shaped by events that took place long before

4:52 the Earth even formed.

4:54 Avery: All right, let's bring it back a little

4:55 closer to home. It's time for an update from,

4:58 uh, SpaceX. Mark your calendars because they

5:01 are targeting October 13th for the

5:04 11th flight of the Starship Mega

5:06 Rocket Flight 11.

5:09 Anna: They are certainly keeping a rapid pace.

5:12 This will be another crucial test for the

5:14 most powerful rocket ever built. What are

5:17 the main objectives for this flight? Avery?

5:20 Avery: The mission profile will look very similar to

5:22 the successful Flight 10. The main goal is to

5:25 demonstrate reliability and reusability. Uh,

5:28 they'll launch the super heavy booster, will

5:30 separate and perform a boostback burn, aiming

5:33 For a soft splashdown in the.

5:34 Anna: Gulf of Mexico and the starship upper

5:37 stage.

5:38 Avery: The ship will continue on a suborbital

5:40 trajectory, Coasting for about an hour before

5:43 performing its own re entry and attempting a

5:46 controlled splashdown in the Indian Ocean.

5:48 They'll also be testing the payload bay door

5:51 again, this time by deploying some mock

5:53 Starlink satellites.

5:55 Anna: Deploying mach satellites is an important

5:57 step towards the vehicle becoming operational

6:00 for its primary mission. Launching the

6:03 next generation of Starlink.

6:05 Avery: Exactly. It's also worth noting that this

6:07 will be the final flight for the current

6:09 version 2 of the Starship vehicle.

6:12 The next flights will feature significant

6:15 upgrades aimed at even faster turnaround

6:17 times and greater reliability.

6:20 Anna: So it's both a validation of the current

6:22 design and a, uh, final farewell before

6:25 we see the next evolution of starship.

6:28 Each of these flights, even when they seem

6:31 repetitive, gathers an immense amount of

6:33 data that feeds directly into those future

6:36 improvements.

6:37 Avery: That's the key iteration we'll be watching on

6:40 October 13th to see if they can stick the

6:43 landing or at least to splashdown.

6:46 Anna: For our final story, we're looking at

6:48 something that's, um, a bit unsettling. The

6:50 idea of hitting dangers in our own solar

6:53 system. Astronomers are suggesting there

6:56 could be a large undiscovered population of

6:59 asteroids lurking near the orbit of

7:02 Venus.

7:03 Avery: Undiscovered asteroids are always a concern.

7:05 Why are these ones particularly hard to spot?

7:08 Are they very small or very dark?

7:11 Anna: It's neither of those actually. It's a

7:14 problem of location. These asteroids are

7:16 believed to be orbiting the sun in a

7:18 resonance with Venus. From our viewpoint

7:21 on Earth, this means they spend almost all

7:24 their time in the direction of the Sun.

7:27 Avery: Ah, uh, so they're lost in the glare. You

7:30 can't really point a telescope at the sun to

7:32 look for faint objects.

7:33 Anna: Precisely. It's like trying to spot a

7:36 firefly next to a searchlight. You ground

7:38 based telescopes are limited to searching the

7:41 sky at twilight, just after sunset

7:44 or before sunrise, which gives them a very

7:47 narrow window to hunt in that direction.

7:49 This creates a huge observational blind

7:52 spot.

7:53 Avery: So we have this potential swarm of asteroids

7:55 nearby, and we can barely see them. Should we

7:58 be worried? Do they pose a threat to Earth?

8:01 Anna: The potential is there. The models show

8:04 that the gravitational pull of Venus can

8:06 nudge these asteroids into chaotic orbits

8:09 over millions of years. Some of those

8:12 chaotic orbits could eventually intersect

8:15 with Earth's orbit, creating a collision risk

8:18 down the line.

8:19 Avery: So this isn't an immediate threat, but a long

8:22 term hazard we need to map out. Is there any

8:24 hope in finding them?

8:26 Anna: Yes, there is. Upcoming missions

8:28 are specifically designed to tackle this

8:31 problem. The Vera Rubin Observatory, with

8:34 its massive field of view, will be able to

8:37 survey the sky much more rapidly during

8:39 twilight. And even better,

8:42 NASA's NEO Surveyor mission will be a, ah,

8:45 space based infrared telescope.

8:48 Avery: A space telescope wouldn't be hampered by the

8:50 sun's glare in the same way, right?

8:53 Anna: Exactly. By operating in space

8:56 and observing in the infrared where asteroids

8:59 glow from the Sun's heat, NEO

9:01 Surveyor will be able to find these elusive

9:04 objects regardless of their position in the

9:06 sky. It's designed to fill in these dangerous

9:09 blind spots in our planetary defense network.

9:12 Avery: That's reassuring. It's a good reminder that

9:15 the sky isn't empty and we need to keep our

9:18 eyes open even in the places that are hardest

9:20 to look.

9:21 And that's all the time we have for today on

9:24 Astronomy Daily. We've journeyed from our two

9:26 face Moon to a great wave in the Milky Way,

9:29 checked in on Starship, and peered into the

9:31 Sun's glare for hidden asteroids.

9:34 Anna: It's a constant reminder that there are

9:36 always new discoveries to be made, both near

9:39 and far. Thanks so much for joining us.

9:43 Avery: You can find Astronomy Daily wherever you get

9:45 your podcasts or simply visit our website at

9:47 astronomydaily IO Be sure

9:50 to subscribe so you don't miss an episode.

9:52 Until next time, keep looking up and keep

9:55 wondering.