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The Universe: Countless Wonders of the Milky Way (S2, E4) | Full Episode | History

HISTORY・28 minutes read

The birth and construction of the Milky Way galaxy, along with the presence of a supermassive black hole at its center, impact star formation and the galaxy's future collision with the Andromeda galaxy. Various telescopes and wavelengths aid astronomers in studying the galaxy's structure, star formation, and the impacts of black holes, providing insights into the universe's vast complexities.

Insights

  • The Milky Way galaxy, home to our solar system, is a dynamic environment where stars are born and die, with a central bulge housing a supermassive black hole that cannot be directly seen due to light not escaping it.
  • The Milky Way's collision with the Andromeda galaxy in the distant future, the slowing of star production due to gas depletion, and the formation of stars in the spiral arms all contribute to the ongoing evolution and transformation of our galaxy.

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Recent questions

  • How big is the Milky Way galaxy?

    The Milky Way is a hundred thousand light years in diameter and has a trillion times more mass than our sun.

  • What is at the center of the Milky Way galaxy?

    The Milky Way's central bulge houses a supermassive black hole that is four million times more massive than our sun.

  • How do astronomers study the Milky Way galaxy?

    Astronomers utilize radio waves to study the Milky Way due to cosmic dust blocking optical telescopes.

  • What is the significance of nebulae in the Milky Way?

    Nebulae in the Milky Way act as recycling centers, forming new stars from dispersed material.

  • How do high-velocity stars form in the Milky Way?

    High-velocity stars are created when a pair of stars interact with a black hole, leading to ejection.

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Summary

00:00

"Milky Way: Birth, Collision, Black Hole"

  • The birth of time, space, and matter occurred after an initial darkness.
  • The universe is a place of creation and destruction, with the Milky Way being just one galaxy among billions.
  • Two small galaxies are currently colliding with the Milky Way.
  • The Milky Way galaxy is a hundred thousand light years in diameter and has a trillion times more mass than our sun.
  • The Milky Way is under construction and is an active place where old stars die and new stars are formed.
  • Our solar system resides within the Milky Way's spiral arms.
  • The Milky Way galaxy is a barred spiral, with a central bulge mostly composed of stars between 10 and 11 billion years old.
  • The Milky Way's central bulge houses a supermassive black hole that is four million times more massive than our sun.
  • Black holes, including the one at the center of the Milky Way, cannot be seen directly due to light not being able to escape them.
  • The Milky Way is part of a local group of galaxies, with the Andromeda galaxy being another significant member.

11:37

"Galactic Ground Zero: The Milky Way"

  • Astronomers have located Galactic Ground Zero through a radio source in the constellation Sagittarius known as Sagittarius "A" star.
  • The black hole in the middle of our galaxy is spinning at a rate of about one spin per 11 minutes.
  • Central region stars caught in the black hole's gravity orbit it at about three million miles per hour.
  • The Milky Way's colossal forces at the galaxy's heart are negated by its unimaginable size.
  • The Milky Way galaxy is incredibly huge, with Earth being comparable to the size of a CD in comparison.
  • The galaxy's bustle and commotion are concentrated in the center, but the spiral arms have their own action where stars are being born.
  • Optical telescopes can't pierce the darkness of the Milky Way due to cosmic dust, necessitating the use of radio waves for study.
  • Radio astronomy was born when Karl Jansky discovered radio waves from the center of our galaxy in 1933.
  • Infrared cameras, like those on the Spitzer Space Telescope, allow astronomers to see through dust clouds and study celestial bodies.
  • Different wavelengths of the electromagnetic spectrum reveal different aspects of the galaxy, aiding astronomers in understanding its activity and shape.

22:50

Galaxies: Stars, Clusters, Nebulae, and Light

  • Stars in galaxies move around like bicycles in the Tour de France, sometimes clumping together in spiral arms and sometimes spreading out.
  • Giant globular clusters populate the galaxy's halo, while the galactic disc contains open or galactic clusters of young stars.
  • Open clusters are formed from giant clouds of dust and gas, with about 20,000 open clusters in the galaxy, the Pleiades being the closest to Earth.
  • The sun may have once been part of an open cluster, and the entire galaxy and universe are built from dust and gases.
  • Sunsets appear yellow, orange, or red due to air molecules scattering blue light and particles like dust absorbing blue light.
  • The blue sky is an optical illusion caused by shorter wavelengths of blue light being scattered more in the atmosphere.
  • Space is dark due to a lack of gas or dust particles reflecting light, with the galactic disc owing 15% of its mass to dust and gas.
  • Nebulae, like the Orion Nebula, are regions of cosmic dust and gas where stars are formed, with different types like emission, reflection, and dark nebulae.
  • Nebulae act as recycling centers in the galaxy, creating new stars from dispersed material from dying stars.
  • Gravity in spiral arms compresses gas clouds, leading to star formation, with massive stars often dying in the spiral arms due to their high luminosity and short lives.

34:14

Galactic collisions and black hole dynamics

  • Stars from other galaxies affect the Milky Way's spiral arms due to gravity.
  • X-ray telescopes helped identify the center of the Milky Way.
  • The X-ray emitter Sagittarius "A" star is linked to the supermassive black hole in the galaxy's center.
  • Stars near the black hole move at extremely high speeds, up to 10,000 kilometers per second.
  • The Milky Way's center contains about three to four million times the mass of the sun.
  • High-velocity stars are ejected by supermassive black holes, moving at 1.5 million miles per hour.
  • High-velocity stars are formed when a pair of stars stray too close to a black hole and one is captured while the other is ejected.
  • The Milky Way is on a collision course with the Andromeda galaxy, possibly merging in three to four billion years.
  • The Milky Way's star production has slowed down over time due to the depletion of gas, leading to a decrease in new star formation.
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