Stellar Stories: Mark Your Calendars for the Blood Moon, Hubble Tension Unravelled

0:01 Avery: Hello, and welcome to Astronomy Daily, the

0:04 podcast that brings you the biggest news from

0:06 across the cosmos. I'm Avery.

0:08 Anna: And I'm Anna. It's great to have you with us

0:11 today. We're marking our calendars for a

0:13 celestial event that will be seen by billion.

0:17 Avery: That's right. We'll also be diving into a

0:19 major cosmic puzzle, the Hubble

0:22 tension and how some brilliant astronomers

0:24 are trying to solve it.

0:26 Anna: Then we'll come back a little closer to home

0:28 to talk about Canada's plans to send its very

0:31 first RO over to the Moon. And finally,

0:34 a truly inspiring story about how an

0:37 amateur astronomer made a cosmic discovery

0:40 from his own backyard.

0:41 Avery: It's a packed show, so let's get started.

0:44 First up, Anna, tell us about this massive

0:47 event we should all be looking forward to.

0:49 Anna: Certainly, everyone should circle

0:52 September 7th and 8th, 2025,

0:55 on their calendars. On those dates, we're

0:57 going to be treated to a total lunar eclipse,

1:00 also known as a Blood Moon.

1:03 Avery: And this isn't just any eclipse. The

1:05 visibility for this one is incredible.

1:08 We're talking over 7 billion people

1:11 across Australia, Asia, Africa

1:14 and Europe will have a chance to see it. It's

1:17 a, uh, truly global event.

1:19 Anna: Exactly. For those who might be new to this,

1:22 a, uh, total lunar eclipse happens when the

1:24 Earth passes directly between the sun and

1:27 the Moon, casting a shadow on the lunar

1:29 surface.

1:30 Avery: And the Blood Moon nickname comes from that

1:32 amazing reddish colour the Moon takes on.

1:35 Right. It always looks so dramatic.

1:38 Anna: It does, and there's some beautiful physics

1:40 behind it. As sunlight passes through Earth's

1:43 atmosphere, the atmosphere scatters the blue

1:45 light, but allows red light to pass through

1:48 and reach the Moon. Essentially, the

1:51 Moon is being illuminated by all of the

1:53 sunrises and sunsets happening on Earth at

1:56 that moment.

1:57 Avery: That's such a poetic way to think about it.

1:59 So how long will we get to enjoy this

2:02 spectacle?

2:02 Anna: The entire event, from the moment the Earth's

2:05 shadow first touches the Moon until it

2:07 leaves, will last about five and a half

2:10 hours. The most spectacular part, the

2:13 totality when the Moon is fully in shadow,

2:16 will last for an impressive 1 hour and

2:18 22 minutes.

2:20 Avery: Plenty of time to get outside and take a

2:22 look. And as if that wasn't enough, there's

2:24 another eclipse, uh, happening right after

2:26 this, isn't there?

2:28 Anna: Yes. Just a couple of weeks later, on

2:30 September 21, 2025. This

2:33 time, it's a partial solar eclipse, where the

2:35 Moon will pass in front of the sun but won't

2:37 cover it completely. This one will be visible

2:40 from New Zealand, Antarctica and parts of

2:43 Australia. So it's a busy month for sky

2:45 watchers in the Southern Hemisphere.

2:47 Avery: Fantastic.

2:48 Well, from one cosmic measurement to another,

2:51 let's talk about the expansion of the

2:53 universe. This has been a source of some

2:56 major debate in astronomy, right, Anna?

2:58 Anna: A huge debate. It's a problem known as

3:01 the Hubble tension. Put simply, different

3:04 methods for measuring how fast the universe

3:06 is expanding are giving us different answers.

3:09 And the difference is significant enough that

3:12 it can't be easily dismissed.

3:14 Avery: So you have one group measuring the expansion

3:16 based on the early universe, like the cosmic

3:19 microwave background, and another group

3:21 measuring it based on objects in the more

3:23 modern universe, like supernovae. And their

3:26 numbers don't measure match precisely.

3:29 Anna: This discrepancy could mean one of two

3:31 things. Either our measurements are wrong,

3:34 or our fundamental understanding of physics

3:37 is incomplete. Now, a team of

3:40 Indian astronomers led by Professor Anupam

3:42 Bhardija has introduced a new method that

3:45 could help settle the debate.

3:47 Avery: And what's their new secret weapon?

3:49 Anna: They're using a specific type of star called

3:52 Mira variables. These are old

3:54 pulsating red giant stars that have a very

3:57 predictable relationship between their

3:59 pulsation period and their intrinsic

4:02 brightness. By measuring how bright they

4:04 appear from Earth, we can calculate their

4:06 distance with great accuracy.

4:09 Avery: So it's another standard candle, like the

4:11 supernovae we use, but a totally different

4:13 type of object. That's a great way to double

4:15 check our results. And what did they find?

4:18 Anna: Using data from the Gaia Space Telescope,

4:21 they've managed to calculate the Hubble

4:23 constant, that's the rate of expansion. With

4:26 a precision of 3.7%.

4:30 Their measurement aligns, uh, more closely

4:32 with the values from other modern universe

4:34 observations, like those using supernovae.

4:38 Avery: So this strengthens the case that the

4:39 discrepancy isn't just a measurement error.

4:42 The Hubble tension might be real. And that

4:44 means what?

4:46 Anna: It could point to new physics, something

4:49 we don't yet understand about the universe.

4:52 It could affect our calculations for the age

4:55 and size of the universe and

4:57 deepen the mystery of dark energy. This

5:00 discovery is a significant step in

5:03 refining our cosmic yardstick.

5:06 Avery: Incredible work from the edge of the

5:08 universe.

5:09 Let's bring it back to our own cosmic

5:11 neighbourhood. We're heading back to the

5:13 moon. And Canada is building the ride.

5:16 Anna: That's right. As part of the Artemis

5:18 programme, the company Canadensis Aerospace

5:21 is developing Canada's very first

5:24 lunar rover. It's a hugely

5:26 exciting project, scheduled for launch in

5:29 2029.

5:31 Avery: It's a compact little explorer, too, only

5:33 about 35 kilogrammes. So what's its

5:36 mission? What will it be looking for.

5:38 Anna: The rover is headed to the moon's south

5:41 polar region, which is a key area of

5:43 interest for scientists. Its primary mission

5:46 is to search for water ice. Finding

5:49 accessible water ice is considered the holy

5:52 grail for future lunar exploration.

5:55 Avery: Because if you have water, you have drinking

5:57 water. For astronauts, you can grow plants

6:00 and you can even split the H2O into hydrogen

6:03 and oxygen to make rocket fuel. It would be a

6:06 total game changer for establishing a long

6:08 term presence on the moon.

6:10 Anna: Exactly. The rover also has a second

6:12 objective to measure lunar radiation.

6:16 Understanding the radiation environment is

6:18 critical for ensuring the safety of future

6:21 astronauts. But it's not going to be an easy

6:24 job. The lunar surface is incredibly

6:27 hostile.

6:27 Avery: I'll say. The temperature swings are mind

6:30 boggling. The rover has to be built to

6:32 withstand everything from -200 degrees

6:35 Celsius in the shadows to a boiling

6:37 100 degrees Celsius in direct sunlight.

6:40 Anna: And then there's the lunar regolith, that

6:43 fine abrasive dust that gets into

6:46 everything. Navigating through it is a

6:49 major engineering challenge. It's a testament

6:52 to the team at Canadensis that they're taking

6:54 this on.

6:55 Avery: Absolutely. We'll be cheering it on in

6:58 2029.

6:59 Now for our final story. We're celebrating a

7:02 different kind of explorer. One without a

7:04 billion dollar budget, but with just as much

7:06 passion.

7:07 Anna: This is a wonderful story that really

7:10 highlights the incredible contributions of

7:13 amateur astronomers. It comes from

7:15 Switzerland, where an amateur named Joseph

7:18 Kaiser has discovered a small moon

7:21 orbiting an asteroid.

7:22 Avery: That's amazing. How on Earth does an amateur

7:25 astronomer spot something like that?

7:27 Asteroids are tiny and a moon orbiting one

7:30 would be even smaller.

7:31 Anna: He used a very clever technique called

7:34 stellar occultation. This is when an

7:37 object, in this case the asteroid, passes

7:40 in front of a distant star,

7:42 temporarily blocking its light.

7:44 Avery: Right. So he was watching the star, expecting

7:47 it to blink out for a moment as the main

7:49 asteroid, named 2001 PE40

7:52 passed.

7:53 Anna: Exactly. But what he observed was

7:56 something unexpected. After the main

7:59 asteroid passed and the star's light

8:01 returned, it disappeared a second time,

8:04 very briefly. That second blink

8:07 was caused by a smaller object

8:10 trailing the asteroid. Its own tiny

8:13 moon.

8:14 Avery: That is brilliant. What a moment that must

8:16 have been, realising what he'd seen. Do we

8:19 know anything about the size of these

8:21 objects?

8:21 Anna: We do. The main asteroid is about

8:24 12.6 kilometres long.

8:27 Its newly discovered moon is about

8:29 2.9 kilometres long and orbits at

8:32 a distance of just under 24 kilometres.

8:35 It's a significant find and a huge

8:38 achievement for amateur astronomy.

8:40 Avery: It really is. It goes to show that you don't

8:43 need to be a professional with a giant

8:44 observatory to make a real contribution to

8:46 science. All you need is patience and skill

8:49 and a clear night sky.

8:51 Anna: A perfect story to end on.

8:53 And that brings us to the close of another

8:55 episode of Astronomy Daily.

8:58 Avery: We covered a lot of ground today, from a

9:00 future blood moon for billions to a new way

9:02 of measuring our expanding universe, to

9:04 Canada's future lunar rover. And a

9:07 fantastic discovery by an amateur astronomer.

9:10 Anna: Thank you so much for joining us. We hope

9:13 you'll subscribe to the podcast so you don't

9:15 miss an episode, and please visit our

9:17 [email protected] for even more

9:20 news and all our back episodes.

9:22 Avery: Until next time, this has been Avery and

9:25 Anna.

9:26 Anna: Keep looking up. Uh.