Anna: Welcome to Astronomy Daily, your regular dose
of the latest happenings in space and
astronomy news. I'm Anna.
Avery: And I'm Avery. We've got a fantastic lineup
for you today. Diving into everything from
the sheer number of stars in our galaxy to
tumbling asteroids, exciting updates from
China's space program, and even the detection
of a truly enigmatic dark object.
Anna: It's going to be a stellar episode. Pun
intended.
Let's kick things off with a question that's
probably. Probably crossed everyone's mind.
Just how many stars are there in the Milky
Way?
Avery: That's a great question, Anna. Uh, and the
answer is more than you can imagine.
Astronomers generally estimate around 100
billion stars in our galaxy. But it's a
number that really depends on a lot of
different factors.
Anna: 100 billion. Wow. And I imagine it's
incredibly difficult to count them from our
vantage point inside the galaxy. Right. All
that dust gets in the way.
Avery: Exactly. It's like trying to count trees from
inside a dense forest. So astronomers
often look to other galaxies, which are
easier to observe as a whole, to develop
their estimation methods.
Anna: One primary method involves studying the
luminosity of galaxies. Astronomers can
estimate the total light output of a galaxy.
And by understanding the typical luminosity
of different star types, they can infer the
total number of stars. This is often combined
with observations of a galaxy's mass inferred
from its rotation speed or the motion of its
stars, as more massive galaxies generally
contain more stars. Another approach
involves analyzing the stellar populations
within representative regions of a galaxy,
then extrapolating those findings to the
galaxy's full extent. While these methods
provide robust estimates, the numbers are
always subject to refinement as our
observational capabilities improve and our
understanding of stellar evolution and
galactic structures deepens. So the
exact number is always evolving, but our
estimates become more precise over time.
Avery: Moving on from the grand scale of galaxies,
let's zoom in to something a bit closer to
home. Asteroids. There's
fascinating new research about why some
asteroids spin smoothly and others
tumble chaotically.
Anna: Yes, this study is really shedding light on
their past. It suggests an asteroid's
rotation is largely determined by how
frequently it's impacted by other space
rocks. Which is quite an intuitive idea when
you think about it.
Avery: Absolutely. And it combines data from ESA's
GAIA mission Advanced Modeling and AI
spearheaded by Dr. Wen Honju from the
University of Tokyo. It's a great example of
interdisciplinary science, revealing the
physics of asteroid rotation and even. Even
their internal structure.
Anna: Uh, what's particularly interesting is the
interplay of two forces, collisions,
which cause the tumbling and internal
friction which tends to stabilize them into a
regular spin. This creates a sort of natural
boundary in asteroid populations.
Avery: That's a fascinating dynamic. So it's a
constant battle between disruptive forces and
stabilizing ones. What does this natural
boundary look like in terms of asteroid size
or composition? Smaller
asteroids, though easily tumbled by impacts,
tend to restabilize relatively quickly due to
their internal friction. It's like they have
a built in dampener for chaotic motion.
Anna: So the larger ones essentially shrug off most
minor collisions, maintaining their steady
spin. It takes a significant hit to disrupt a
truly massive asteroid. It's essentially
a size dependent threshold. For a small
asteroid, even a relatively minor impact can
induce tumbling. But its internal structure
quickly absorbs that energy, Allowing it to
settle back into a predictable spin. For
larger asteroids, their sheer mass and
gravitational integrity mean only a very
substantial energetic collision. Would impart
enough angular momentum to truly destabilize
their rotation for an extended period. And
crucially, this study also confirms the YORP
effect. That's the YORP effect as
a primary driver for rapid rotation in
smaller asteroids. It highlights how
radiation pressure can subtly reshape and
spin up these smaller bodies. Something less
influential on their larger, more massive
counterparts. And in case you're wondering
because I was and looked it up, YORP stands
for Yarkovsky, OKeefe, Radzievsky Paddock.
Honoring four scientists who contributed to
the understanding of these radiation driven
rotational changes in small bodies.
Avery: Thank you. I was going to ask, but that's
a good point about the YORP effect. Could you
elaborate a little more on how that radiation
pressure actually, actually works to spin up
these asteroids? It sounds quite subtle.
Anna: Essentially, as sunlight hits an asteroid, it
absorbs some of the energy and then re emits
it as heat. This re emitted heat carries a
tiny bit of momentum. If the asteroid has an
irregular shape or if its surface properties
vary, it will re emit heat unevenly.
This uneven re emission creates a very small
continuous torque or twisting force. That can
gradually increase or decrease the asteroid's
speed spin rate over long periods. It's a
subtle but powerful effect, Especially for
smaller bodies where their mass is not enough
to resist this gentle push.
Avery: Speaking of important research, let's pivot
to some exciting news from China's space
program. It's truly a dynamic time
with an accelerating launch cadence. And
commercial providers on the verge of their
maiden orbital flights.
Anna: That's fascinating. What's the latest from
the Tiangong Space Station?
Avery: Tiangong has been incredibly busy.
They recently completed their fourth
spacewalk, A significant milestone
they're also preparing for the Shenzhou 21
mission, which will bring new taikonauts to
the station, continuing long duration
scientific experiments. Switching gears
to deep space. New images have just
arrived from Tianwen 2. The probe is on
its way to the Near Earth asteroid Kamo
Oalewa, aiming for a sample return,
which would be a monumental achievement.
And on the commercial front, the competition
is heating up. We're seeing rapid progress in
launch vehicles and engine testing.
Landspace's powerful BF20 engine is
undergoing advanced tests. And Deep Blue
Aerospace's Lightning RS is also making
strides. Galactic Energy's Palace 1
is CAS Space's Lijian 2 and
Orient Space's Yin Li 2 are all nearing their
inaugural flights, promising to significantly
boost China's access to space.
Anna: That's incredible. What about China's crewed
lunar mission plans?
Avery: The Changcheng 10 rocket, crucial for
China's ambitious crewed lunar missions,
recently completed a successful tethered
ignition test. This is a critical step,
demonstrating its propulsion system's
readiness for human spaceflight and
future lunar landings. It really shows
their long term vision and commitment to deep
space exploration. So, as you can see, we
may not hear a lot from the Chinese space
program, but they are making rapid strides
and are far from being idle.
Anna: From ambitious missions to something far more
elusive, astronomers have recently detected
a, uh, mysterious dark object, not by its
light, but purely by its gravitational pull.
This is truly a groundbreaking discovery.
Avery: That's right, Ana. The leading candidates are
indeed a rogue black hole or neutron
star, which are both remnants of massive
stars. However, a less massive
possibility is an isolated brown dwarf,
a failed star that never quite ignited
fusion. The key here is free floating,
meaning it's not gravitationally bound to any
star moving independently through the galaxy.
Anna: That's a fascinating concept, free floating.
So this object is truly isolated, not
orbiting anything. And that's what makes it
so challenging to detect without
gravitational lensing. And this
detection method, known as microlensing, is
truly revolutionary. It works by observing
how the dark object's gravity warps the light
from a background star. As the object passes
in front of the star, it temporarily
brightens the background star's light, acting
like a cosmic magnifying glass. This
technique is incredibly sensitive to objects
that emit no light of their own.
Avery: This discovery is really pushing the
boundaries of what we can detect. It provides
crucial insights into the population of dark
compact objects in our galaxy. Objects that
don't emit light, but whose gravitational
influence is undeniable. It also
helps us refine our models of galactic
structure and, and even gives us clues about
the elusive nature of dark matter, especially
if these objects turn out to be primordial
black holes.
Anna: And that wraps up another fascinating journey
through the cosmos on Astronomy Daily. We've
covered a lot of ground today, from the
incredible dynamics of asteroids to
groundbreaking Chinese space missions and the
mysteries of dark objects.
Avery: And, um, thank you for joining us on
Astronomy Daily. For more space and
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