00:00:00 --> 00:00:02 Avery: Welcome, listeners, to Astronomy Daily, the
00:00:02 --> 00:00:05 podcast that brings the cosmos down to Earth.
00:00:05 --> 00:00:06 I'm Avery.
00:00:06 --> 00:00:09 Anna: And I'm Anna. We have a fantastic
00:00:09 --> 00:00:12 show for you today, packed with news from our
00:00:12 --> 00:00:14 celestial neighborhood and the farthest
00:00:14 --> 00:00:15 reaches of the universe.
00:00:15 --> 00:00:17 Avery: That's right, we'll be looking up at the
00:00:17 --> 00:00:20 biggest supermoon of 2025,
00:00:20 --> 00:00:22 tracking an interstellar visitor as it zips
00:00:22 --> 00:00:25 past the sun and uncovering a strange
00:00:25 --> 00:00:27 atmospheric mystery on Mars.
00:00:27 --> 00:00:30 Anna: And to cap it all off, we'll be exploring a
00:00:30 --> 00:00:33 mind bending new the that asks, what if
00:00:33 --> 00:00:35 dark matter doesn't exist at all?
00:00:35 --> 00:00:37 Avery: It's going to be a, um, big one.
00:00:37 --> 00:00:40 Let's get started with a sight we can all
00:00:40 --> 00:00:42 look forward to in our own night sky.
00:00:42 --> 00:00:45 Anna: Indeed, after a year of seeing the Moon
00:00:45 --> 00:00:47 looking a bit smaller than usual, we're in
00:00:47 --> 00:00:49 for a treat next week.
00:00:49 --> 00:00:52 11:48pm Eastern Time on
00:00:52 --> 00:00:55 October 6, to be precise, which,
00:00:55 --> 00:00:57 if I've done my math correctly,
00:00:57 --> 00:00:59 corresponds to 3:48
00:01:00 --> 00:01:02 UTC on October 7th
00:01:03 --> 00:01:05 will see the biggest and brightest supermoon
00:01:05 --> 00:01:07 of 2025.
00:01:07 --> 00:01:10 Avery: I'm already marking my calendar. So for
00:01:10 --> 00:01:13 our listeners who might be new to this, what
00:01:13 --> 00:01:15 exactly makes a full moon a, uh,
00:01:15 --> 00:01:16 supermoon?
00:01:16 --> 00:01:19 Anna: It's all about the moon's orbit. It's not a
00:01:19 --> 00:01:21 perfect circle, it's an ellipse. So
00:01:21 --> 00:01:24 sometimes the Moon is at its farthest point
00:01:24 --> 00:01:26 from Earth, which we call apogee. And
00:01:26 --> 00:01:28 sometimes it's at its closest point, or
00:01:28 --> 00:01:31 perigee. A supermoon happens when a full
00:01:31 --> 00:01:33 moon coincides with its perigee.
00:01:33 --> 00:01:35 Avery: And that makes it look bigger and brighter in
00:01:35 --> 00:01:38 the sky. Right. I read it can appear up to
00:01:38 --> 00:01:41 14% larger and 30% brighter than a
00:01:41 --> 00:01:43 micro moon, which is when the full moon
00:01:43 --> 00:01:44 happens at apogee.
00:01:44 --> 00:01:47 Anna: Exactly. And we've just come through a period
00:01:47 --> 00:01:49 of micro moons, so the difference will be
00:01:49 --> 00:01:52 quite noticeable. This particular supermoon
00:01:52 --> 00:01:54 is also the Harvest Moon, which is the full
00:01:54 --> 00:01:57 moon closest to the autumnal equinox.
00:01:57 --> 00:01:59 Avery: The harvest Moon. That's the one that
00:01:59 --> 00:02:01 historically helped farmers bring in their
00:02:01 --> 00:02:04 crops. Because it rises so close to sunset,
00:02:04 --> 00:02:07 giving them extra light to work by, it often
00:02:07 --> 00:02:09 looks huge and orange on the horizon.
00:02:09 --> 00:02:12 Anna: That's the one. The orange color is due to
00:02:12 --> 00:02:14 the same effect that makes sunsets red. The
00:02:14 --> 00:02:16 light is passing through more of Earth's
00:02:16 --> 00:02:19 atmosphere. So next week we get a combination
00:02:19 --> 00:02:22 of things. The closest full moon of the year
00:02:22 --> 00:02:24 and the beautiful effect of the harvest moon,
00:02:25 --> 00:02:27 all making for a spectacular celestial event.
00:02:28 --> 00:02:30 Avery: From something we can see with our own eyes
00:02:30 --> 00:02:32 to something that requires a fleet of
00:02:32 --> 00:02:34 interplanetary spacecraft.
00:02:34 --> 00:02:37 Let's get an update on the interstellar comet
00:02:37 --> 00:02:38 3i Atlas.
00:02:38 --> 00:02:41 Anna: This is incredibly exciting.
00:02:41 --> 00:02:43 3i Atlas is only the third
00:02:43 --> 00:02:46 interstellar object we've ever detected
00:02:46 --> 00:02:48 passing through our solar system. The first
00:02:48 --> 00:02:51 was Oumuamua and The second was
00:02:51 --> 00:02:54 2i Borisov. These objects are
00:02:54 --> 00:02:56 cosmic messengers from other star systems.
00:02:57 --> 00:02:59 Avery: And the European Space Agency is pulling out
00:02:59 --> 00:03:02 all the stops to study this one. From now
00:03:02 --> 00:03:04 until early November, they're planning to use
00:03:04 --> 00:03:07 a trio of their spacecraft, the Mars
00:03:07 --> 00:03:10 Express and ExoMars Trace Gas Orbiter,
00:03:10 --> 00:03:13 which are both orbiting Mars, and the JUICE
00:03:13 --> 00:03:15 spacecraft, which is on its way to Jupiter.
00:03:16 --> 00:03:18 Anna: The reason this is such a unique opportunity
00:03:18 --> 00:03:21 is because of the comet's trajectory. As it
00:03:21 --> 00:03:24 makes its closest approach to the sun, it's
00:03:24 --> 00:03:26 going to heat up dramatically. This heating
00:03:26 --> 00:03:29 causes ices on its surface to sublimate,
00:03:29 --> 00:03:32 turn directly into gas, releasing dust
00:03:32 --> 00:03:34 and revealing the chemical composition of the
00:03:34 --> 00:03:35 comet's nucleus.
00:03:36 --> 00:03:38 Avery: So it's like unwrapping a gift from another
00:03:38 --> 00:03:41 star. And using three different spacecraft
00:03:41 --> 00:03:43 gives them a huge advantage, doesn't it?
00:03:43 --> 00:03:46 Anna: It certainly does. Each spacecraft has
00:03:46 --> 00:03:48 different instruments and will see the comet
00:03:48 --> 00:03:50 from a different vantage point. This
00:03:50 --> 00:03:53 triangulation allows scientists to build a
00:03:53 --> 00:03:56 much more complete 3D picture of the comet's
00:03:56 --> 00:03:59 activity and the mater its shedding. By
00:03:59 --> 00:04:01 studying the composition of this gas and
00:04:01 --> 00:04:03 dust, we can learn about the building blocks
00:04:03 --> 00:04:06 of planets in whatever distant star system
00:04:06 --> 00:04:07 this comet came from.
00:04:07 --> 00:04:09 Avery: It's a reminder of how interconnected the
00:04:09 --> 00:04:12 galaxy is. A piece of another solar system
00:04:13 --> 00:04:15 just passing through for a quick visit.
00:04:15 --> 00:04:16 Incredible.
00:04:17 --> 00:04:18 Anna: Absolutely.
00:04:19 --> 00:04:21 Now let's bring our focus a little closer to
00:04:21 --> 00:04:24 home, to our planetary neighborhood,
00:04:24 --> 00:04:27 Mars. Scientists have been puzzled
00:04:27 --> 00:04:30 by a mysterious surge in ozone
00:04:30 --> 00:04:33 that appears over its north pole during the
00:04:33 --> 00:04:33 winter.
00:04:33 --> 00:04:36 Avery: M ozone on Mars. I, uh, usually
00:04:36 --> 00:04:39 associate ozone with Earth's protective
00:04:39 --> 00:04:41 layer. Is it the same thing?
00:04:41 --> 00:04:43 Anna: It's the same molecule. Three
00:04:43 --> 00:04:46 oxygen atoms bonded together. But
00:04:46 --> 00:04:49 on Mars, its behavior is very different.
00:04:50 --> 00:04:53 Using the ExoMars Trace Gas Orbiter.
00:04:53 --> 00:04:55 The same one. Watching the comet,
00:04:56 --> 00:04:58 scientists noticed that ozone
00:04:58 --> 00:05:00 concentrations in the middle atmosphere
00:05:01 --> 00:05:03 spike during the winter inside the
00:05:03 --> 00:05:04 polar vortex.
00:05:05 --> 00:05:08 Avery: A, uh, polar vortex. We have those on
00:05:08 --> 00:05:11 Earth too. Basically a giant spinning cyclone
00:05:11 --> 00:05:12 of frigid air, right?
00:05:12 --> 00:05:15 Anna: Precisely. And on Mars, it
00:05:15 --> 00:05:17 gets incredibly cold inside this
00:05:17 --> 00:05:20 vortex, dropping below minus
00:05:20 --> 00:05:22 1, 130 degrees Celsius.
00:05:23 --> 00:05:25 This cold is the key to the mystery.
00:05:26 --> 00:05:29 Normally, water vapor in the atmosphere
00:05:29 --> 00:05:31 reacts with other chemicals to destroy
00:05:31 --> 00:05:32 ozone.
00:05:33 --> 00:05:35 Avery: But when it gets that cold, the water vapor
00:05:35 --> 00:05:38 freezes out, forming ice clouds.
00:05:38 --> 00:05:41 So with the water vapor gone, the.
00:05:41 --> 00:05:43 Anna: Ozone destroying chemical reactions Stop.
00:05:44 --> 00:05:46 And the ozone is allowed to build up to
00:05:46 --> 00:05:49 much higher concentrations than seen
00:05:49 --> 00:05:51 anywhere else on the planet.
00:05:52 --> 00:05:53 Avery: That's a clever piece of atmospheric
00:05:53 --> 00:05:56 detective work. What does this tell us about
00:05:56 --> 00:05:56 Mars?
00:05:57 --> 00:05:59 Anna: It gives us a new way to trace the
00:05:59 --> 00:06:02 circulation of gases in the Martian
00:06:02 --> 00:06:04 atmosphere. And more importantly,
00:06:05 --> 00:06:07 it helps us understand the history of water
00:06:07 --> 00:06:10 on Mars. By tracking where and
00:06:10 --> 00:06:13 when water vapor is present, we can build
00:06:13 --> 00:06:16 better models of Mars past climate and
00:06:16 --> 00:06:19 figure out where all its ancient water went.
00:06:20 --> 00:06:22 Avery: From a mystery on Mars to the biggest
00:06:22 --> 00:06:25 mystery in the entire cosmos. Ana, uh, we
00:06:25 --> 00:06:27 have to talk about this new theory that
00:06:27 --> 00:06:30 challenges the very existence of dark matter
00:06:30 --> 00:06:31 and dark energy.
00:06:31 --> 00:06:34 Anna: This is one of those ideas that could either
00:06:34 --> 00:06:36 be a dead end or completely
00:06:36 --> 00:06:39 revolutionized cosmology. The standard
00:06:39 --> 00:06:42 model of the universe called Lambda
00:06:42 --> 00:06:44 CDM tells us that about
00:06:44 --> 00:06:47 95% of the universe is made of
00:06:47 --> 00:06:50 two invisible components, dark
00:06:50 --> 00:06:51 matter and dark energy.
00:06:52 --> 00:06:54 Avery: Right. Dark matter provides the extra gravity
00:06:54 --> 00:06:57 needed to hold galaxies together. And dark
00:06:57 --> 00:06:59 energy is, ah, a force that's causing the
00:06:59 --> 00:07:02 universe's expansion to accelerate. We can't
00:07:02 --> 00:07:04 see them, but we infer their existence from
00:07:04 --> 00:07:04 their effects.
00:07:05 --> 00:07:08 Anna: Exactly. But physicist Rajendra
00:07:08 --> 00:07:11 Gupta, uh, from the University of Ottawa, has
00:07:11 --> 00:07:13 proposed a new model that gets rid of both.
00:07:14 --> 00:07:17 His idea is based on a combination of
00:07:17 --> 00:07:20 other theories, including one about tired
00:07:20 --> 00:07:23 light and another covariing
00:07:23 --> 00:07:24 coupling constants.
00:07:25 --> 00:07:27 Avery: Whoa, those are some heavy terms. Let's break
00:07:27 --> 00:07:30 that down. Covariing coupling
00:07:30 --> 00:07:32 constants. What does that mean?
00:07:32 --> 00:07:34 Anna: In simple terms? It means that the
00:07:34 --> 00:07:37 fundamental constants of nature, things like
00:07:37 --> 00:07:39 the strength of gravity or the
00:07:39 --> 00:07:42 electromagnetic force, might not actually
00:07:42 --> 00:07:45 be constant. They could be changing very,
00:07:45 --> 00:07:48 very slowly as the universe ages and
00:07:48 --> 00:07:49 expands.
00:07:49 --> 00:07:52 Avery: So if the strength of these forces changed
00:07:52 --> 00:07:54 over billions of years, how would that
00:07:54 --> 00:07:55 replace dark matter?
00:07:56 --> 00:07:58 Anna: Gupta's model suggests that these
00:07:58 --> 00:08:01 changing constants could create effects that
00:08:01 --> 00:08:04 we currently misinterpret as dark matter.
00:08:04 --> 00:08:07 For example, the way galaxies rotate
00:08:07 --> 00:08:10 much faster than they should, which is, uh, a
00:08:10 --> 00:08:12 key piece of evidence for Dark matter could
00:08:12 --> 00:08:15 be explained by these evolving physical
00:08:15 --> 00:08:17 laws instead of an unseen particle.
00:08:18 --> 00:08:21 The model also accounts for the accelerated
00:08:21 --> 00:08:24 expansion of the universe without needing
00:08:24 --> 00:08:24 dark energy.
00:08:25 --> 00:08:28 Avery: So we might not be living in a universe
00:08:28 --> 00:08:31 filled with mysterious dark stuff, but in a
00:08:31 --> 00:08:33 universe where the fundamental rules are
00:08:33 --> 00:08:36 slowly changing. That's a profound thought.
00:08:37 --> 00:08:39 Anna: It is. It's important to stress that
00:08:39 --> 00:08:42 this is still a very new and
00:08:42 --> 00:08:45 untested hypothesis. The vast
00:08:45 --> 00:08:47 majority of evidence still points towards the
00:08:47 --> 00:08:50 standard lambda CDM model. But
00:08:50 --> 00:08:53 it's a fascinating alternative that reminds
00:08:53 --> 00:08:55 us to keep questioning our assumptions.
00:08:56 --> 00:08:58 It shows that there are still huge
00:08:58 --> 00:09:01 fundamental questions about our universe left
00:09:01 --> 00:09:02 to answer.
00:09:02 --> 00:09:04 Avery: And that is a perfect place to wrap up for
00:09:04 --> 00:09:05 today.
00:09:05 --> 00:09:07 From a supermoon in our backyard to an
00:09:07 --> 00:09:09 interstellar comet, a Martian weather
00:09:09 --> 00:09:11 mystery, and a whole new way to think about
00:09:11 --> 00:09:14 the universe itself, it's been a.
00:09:14 --> 00:09:17 Anna: Whirlwind tour of the cosmos. Thank you so
00:09:17 --> 00:09:19 much for joining us on Astronomy Daily. If
00:09:19 --> 00:09:21 you'd like to see more details on these
00:09:21 --> 00:09:23 stories and more, please visit our
00:09:23 --> 00:09:26 website@astronomydaily.IO
00:09:26 --> 00:09:28 and check out our continually updated
00:09:28 --> 00:09:31 newsfeed. And while there, you may like to
00:09:31 --> 00:09:34 sign up for our free daily newsletter as
00:09:34 --> 00:09:34 well.
00:09:34 --> 00:09:37 Avery: Join us again tomorrow as we continue to
00:09:37 --> 00:09:39 explore the wonders of the universe. Clear
00:09:39 --> 00:09:41 skies, everyone. And remember to keep looking
00:09:41 --> 00:09:43 up, especially this week.