銀河の誕生に関する新発見
Hello everyone, welcome to SCIENSPOT. This podcast shines a spotlight on the latest scientific
technology from Japan. Your host is REN from SCIEN-TALK.
So everyone, our Milky Way galaxy and countless others shine brightly in the night sky. How
these galaxies were born and how they evolved is one of the biggest themes in astrophysics.
According to previous cosmological models and simulations, young galaxies formed relatively
early after the Big Bang, during the university's infancy, were expected to have a relatively
uniform, smooth, disk-like structure, formed by gas and dust gathering. You might imagine
them as flat, beautiful plates. However, the universe is far more profound than we
can imagine. This time, a research group including the University of Tokyo has made a surprising
discovery that significantly overturned this conventional wisdom about galaxy birth. This
main stars of this discovery are two cutting-edge telescopes, the James Webb Space Telescope
and the ALMA Telescope. The James Webb Space Telescope, which began full operation in 2022
高性能望遠鏡と若い銀河の観測
as a successor to the Hubble Space Telescope, is a high-performance, infrared-focused telescope
excellent at observing the very early universe. On the other hand, the ALMA Telescope, located
at an altitude of about 5,000 meters in the Atacama Desert in Chile, is a radio interferometer
consisting of 66 antennas, superb for observing the gas and dust where stars and planets are
formed. The research theme focused on the dim, young, rotating galaxy that existed approximately
900 million years after the Big Bang, when the universe was still very young. Previous
observations by the Hubble Space Telescope and even earlier James Webb telescopes hadn't
clearly resolved its internal structure, making it appear as a smooth disk. However,
in this study, they didn't just use high-performance telescopes. There was another crucial element,
the utilization of the gravitational lensing effect. This phenomenon occurs when this strong
gravity of a massive galaxy cluster in the foreground bends the light coming from a distant
galaxy, magnifying it like a natural magnifying glass. By combining this gravitational lensing
effect with the sensitivity and resolution of JWST and ALMA, they succeeded in observing
the internal structure of this galaxy in detail, achieving an incredibly high resolution
of just about 30 light-years. For reference, 30 light-years is a relatively close distance
even within our own galaxy. The internal structure of this young galaxy, previously thought to
be smooth, was revealed to be composed of at least 15 compact star clusters, clumped
together like a bunch of grapes. The researchers named this structure the Cosmic Grape. Interestingly,
despite this clumpy structure, the galaxy as a whole still exhibited a smooth rotational
motion of its gas. What's even more surprising is that this Cosmic Grape galaxy was a very typical
galaxy of that era, consistent with many other galaxies in terms of its size, mass, chemical
composition, and star formation activity. This means that this discovery wasn't just a chance
コズミックグレープの発見
encounter with a unique galaxy. It suggests that perhaps other early galaxies, which we've
so far seen as smooth, might also have a clumpy Cosmic Grape-like structure, but our current
telescopes simply haven't had the resolution to confirm it yet. This finding couldn't be reproduced
by previous simulations and compels us to rethink the fundamental mystery of how galaxies formed
and evolved in the universe. The discovery of the Cosmic Grape has revealed a new picture of
our galaxies, showing them to be surprisingly clumpy shortly after the Big Bang. This suggests
that the energy from the supernova explosion or black holes in the early stage of galaxy
formation might have been weaker than previously assumed, potentially prompting a significant
revision of our understanding of cosmic structure formation. It's truly like adding a new page to
the universe's history book. So that's all for today's SciencePod, and now for some news about
the podcast. This podcast is approaching its 50th episode, but starting in September, I expected to
be quite busy, so I'll be reducing the update frequency. I really didn't want to cut back,
but with 10 episodes a week in both Japanese and English, my schedule is getting a bit too
packed. So I'm planning to reduce the total to four episodes per week, two in Japanese and two in
English. My apologies to anyone who was looking forward to more frequent updates. Also, I'll be
traveling to Prague, Czech Republic starting tomorrow, so next week's episodes might also be
delayed. But the podcast will continue, so thank you for your continued support. I'd love for you
to listen to the podcast and post your thoughts with hashtag SciencePod. Thank you for listening,
and see you next time.
