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