WEBVTT 1 00:00:03.399 --> 00:00:08.880 Welcome to Bedtime Astronomy. Explore the wonders of the cosmos with our soothing Bedtime 2 00:00:08.880 --> 00:00:14.759 Astronomy podcast. Each episode offers a gentle journey through the stars, planets, 3 00:00:14.800 --> 00:00:19.800 and beyond, perfect for unwinding after a long day. Let's travel through the 4 00:00:19.800 --> 00:00:23.519 mysteries of the universe as you drift off into a peaceful slumber under the night 5 00:00:23.519 --> 00:00:34.159 sky. The Milky Way our home galaxy. The Milky Way is the galaxy 6 00:00:34.280 --> 00:00:40.359 that contains our Solar System, along with billions of other stars, planets, 7 00:00:40.399 --> 00:00:46.920 and cosmic structures. It is one of the many galaxies in the observable universe 8 00:00:47.399 --> 00:00:54.119 and part of a larger structure called the Lania KaiOS Supercluster. In this podcast, 9 00:00:54.560 --> 00:01:00.359 we will explore the origin, structure, composition, and evolution of the 10 00:01:00.399 --> 00:01:04.359 Milky Way, as well as some of the fascinating phenomena and mysteries that it 11 00:01:04.439 --> 00:01:15.560 harbors. Origin and history. The Milky Way is estimated to be about thirteen 12 00:01:15.599 --> 00:01:21.200 point six billion years old, slightly younger than the age of the universe itself. 13 00:01:22.560 --> 00:01:26.359 It formed from the gravitational collapse of a large cloud of gas and dust 14 00:01:27.000 --> 00:01:33.959 shortly after the Big Bang. The first stars and clusters in the Milky Way 15 00:01:34.079 --> 00:01:38.319 were metal poor, meaning they had low amounts of elements heavier than hydrogen and 16 00:01:38.359 --> 00:01:47.560 helium. These stars enriched the interstellar medium with heavier elements through stellar nucleosynthesis and 17 00:01:47.719 --> 00:01:53.760 supernova explosions. The Milky Way gradually grew in size and mass by merging with 18 00:01:53.920 --> 00:02:05.079 smaller galaxies and accreting gas from the surrounding environment. The Milky Way has experienced 19 00:02:05.120 --> 00:02:12.199 several major events that shaped its history and appearance. About ten billion years ago, 20 00:02:12.599 --> 00:02:16.680 it collided with a galaxy called guy Enceladus, which triggered a burst of 21 00:02:16.759 --> 00:02:23.479 star formation and created the thick disk of the galaxy. About six billion years 22 00:02:23.520 --> 00:02:30.199 ago, it was perturbed by the passage of the Sagittarius dwarf spheroidal galaxy, 23 00:02:30.639 --> 00:02:37.240 a satellite galaxy that is still orbiting the Milky Way today. This caused ripples 24 00:02:37.319 --> 00:02:42.120 and waves in the disk of the galaxy and may have contributed to the formation 25 00:02:42.280 --> 00:02:49.199 of the spiral arms. About four point five billion years ago, thesolar system 26 00:02:49.360 --> 00:02:53.159 was born in the Orion arm of the galaxy, a minor arm located between 27 00:02:53.199 --> 00:03:00.560 the two major arms. The solar system has since completed about twenty The orbits 28 00:03:00.599 --> 00:03:05.400 around the center of the galaxy at a speed of about two hundred and twenty 29 00:03:05.479 --> 00:03:12.439 kilometers per second. The Milky Way is currently interacting with another large galaxy, 30 00:03:12.879 --> 00:03:17.199 the Andromeda Galaxy, which is about two point five million light years away. 31 00:03:19.599 --> 00:03:23.280 The two galaxies are approaching each other at a speed of about one hundred and 32 00:03:23.400 --> 00:03:30.680 ten kilometers per second and are expected to collide in about four billion years. 33 00:03:30.520 --> 00:03:37.080 The collision will result in a massive merger that will create a new elliptical galaxy, 34 00:03:37.639 --> 00:03:43.719 sometimes called Melcomta or Milk Drameda. The fate of the Solar System in 35 00:03:43.759 --> 00:03:47.199 this merger is uncertain, but it is likely that it will be ejected from 36 00:03:47.199 --> 00:03:54.919 its current position and move to a more distant and chaotic orbit. Structure and 37 00:03:55.000 --> 00:04:03.879 composition, the Milky Way is a barred spiral galaxy, meaning it has a 38 00:04:03.960 --> 00:04:11.280 central bar shaped structure composed of stars and spiral arms that extend from the ends 39 00:04:11.280 --> 00:04:16.040 of the bar. The bar is about twenty seven thousand light years long and 40 00:04:16.160 --> 00:04:20.920 is surrounded by a ring of gas and dust called the five kpc ring. 41 00:04:23.279 --> 00:04:29.199 The spiral arms are regions of higher density of gas and dust where star formation 42 00:04:29.439 --> 00:04:34.360 is more active. The Milky Way has two major arms, called the scutum 43 00:04:34.439 --> 00:04:41.160 Centaurus arm and the Perseus Arm, and two minor arms called the Normal Arm 44 00:04:41.279 --> 00:04:46.680 and the Sagittarius Arm. There are also smaller spurs and branches that connect the 45 00:04:46.879 --> 00:04:54.199 arms, such as the Orion arm where the Solar system is located. The 46 00:04:54.240 --> 00:04:59.319 Milky Way has a disc like shape with a diameter of about one hundred and 47 00:04:59.439 --> 00:05:03.720 seventy thre thousand light years and a thickness of about one thousand light years at 48 00:05:03.720 --> 00:05:11.240 the spiral arms. The disc is divided into two components, the thin disk 49 00:05:11.439 --> 00:05:16.319 in the thick disk. The thin disc contains younger and more metal rich stars 50 00:05:16.759 --> 00:05:21.879 and is the site of most of the star formation in the galaxy. The 51 00:05:21.920 --> 00:05:27.920 thick disk contains older and more metal poor stars and is the remnant of an 52 00:05:27.959 --> 00:05:33.480 ancient stellar population. The thin disk and the thick disk are separated by a 53 00:05:33.519 --> 00:05:39.920 scale height of about three hundred light years, meaning that the density of stars 54 00:05:40.040 --> 00:05:45.560 drops by half for every three hundred light years above or below the midplane of 55 00:05:45.560 --> 00:05:54.959 the disc. The Milky Way also has a spherical component called the halo that 56 00:05:55.000 --> 00:06:00.879 surrounds the disc. The halo contains globular clusters, which are dense groups of 57 00:06:00.879 --> 00:06:08.680 old stars that orbit the center of the galaxy. B halo also contains individual 58 00:06:08.720 --> 00:06:14.399 stars, mostly metal pore and low mass, that have high velocities and random 59 00:06:14.519 --> 00:06:19.040 orbits. Some of these stars are believed to be the oldest in the galaxy, 60 00:06:19.480 --> 00:06:25.720 dating back to the early stages of its formation. B halo has a 61 00:06:25.800 --> 00:06:30.600 diameter of about two hundred thousand light years in a mass of about ten percent 62 00:06:30.720 --> 00:06:35.720 of the disc. The center of the Milky Way is a region of high 63 00:06:35.720 --> 00:06:44.480 density and activity where a supermassive black hole resides. The black hole, called 64 00:06:44.600 --> 00:06:48.959 Sagittarius a asterisk, as a mass of about four million times that of the 65 00:06:49.000 --> 00:06:55.199 Sun and is surrounded by a rotating disk of gas and dust that feeds it. 66 00:06:56.560 --> 00:07:00.040 The black hole is also orbited by a cluster of stars, some of 67 00:07:00.079 --> 00:07:05.879 which have very close and fast orbits. The center of the galaxy is also 68 00:07:06.000 --> 00:07:13.079 the source of powerful emissions of radio, infrared, X ray and gamma ray 69 00:07:13.240 --> 00:07:18.399 radiation, as well as jets and winds of particles that influence the surrounding environment. 70 00:07:19.759 --> 00:07:25.600 The Milky Way is composed of different types of matter, both visible and 71 00:07:25.720 --> 00:07:32.199 invisible. The visible matter includes stars, gas, dust, and planets, 72 00:07:32.560 --> 00:07:39.319 which make up about fifteen percent of the total mass of the galaxy. The 73 00:07:39.439 --> 00:07:45.639 invisible matter includes dark matter and dark energy, which make up about eighty five 74 00:07:45.800 --> 00:07:51.199 percent of the total mass of the galaxy. Dark matter is a mysterious substance 75 00:07:51.279 --> 00:07:56.959 that does not interact with light, but as gravity and affects the motion of 76 00:07:57.079 --> 00:08:03.720 visible matter. Dark energy is a mysterious force that causes the expansion of the 77 00:08:03.800 --> 00:08:09.480 universe to accelerate. The nature and origin of dark matter and dark energy are 78 00:08:09.560 --> 00:08:16.240 unknown, but they are essential for explaining the structure and evolution of the galaxy 79 00:08:16.480 --> 00:08:28.040 and the universe evolution and future. The Milky Way is a dynamic and evolving 80 00:08:28.199 --> 00:08:35.879 system, constantly changing its shape, size, and composition. The galaxy is 81 00:08:35.000 --> 00:08:43.320 influenced by internal and external factors such as star formation and death, stellar feedback, 82 00:08:43.759 --> 00:08:52.480 galactic rotation, gravitational interactions, and cosmological expansion. The galaxy is also 83 00:08:52.679 --> 00:08:58.559 subject to various hazards and threats such as supernova explosions, gamma ray bursts, 84 00:09:00.120 --> 00:09:05.759 rogue stars and planets, and galactic collisions. The Milky Way is currently in 85 00:09:05.840 --> 00:09:11.799 a relatively stable and quiescent phase, with a moderate rate of star formation and 86 00:09:11.879 --> 00:09:18.919 a balanced budget of gas inflow and outflow. However, this situation may change 87 00:09:18.919 --> 00:09:26.840 in the future as the galaxy encounters new challenges and opportunities. Some of the 88 00:09:26.960 --> 00:09:31.679 possible scenarios for the future of the Milky Way are One, the Milky Way 89 00:09:31.720 --> 00:09:37.840 will continue to merge with its satellite galaxies such as the large and small Magellanic 90 00:09:37.919 --> 00:09:46.279 Clouds, the Sagittarius Dwarf, and the Canis Major Dwarf. These mergers will 91 00:09:46.320 --> 00:09:52.360 bring fresh gas and stars to the galaxy and trigger episodes of star formation and 92 00:09:52.480 --> 00:09:58.600 activity. However, they will also disrupt the structure and kinematics of the galaxy 93 00:10:00.120 --> 00:10:07.480 and create tidal streams and debris around it. Two, the Milky Way will 94 00:10:07.519 --> 00:10:13.480 collide with the Andromeda Galaxy as mentioned before, in about four billion years. 95 00:10:15.080 --> 00:10:18.679 This will be a major event that will transform the galaxy into a new and 96 00:10:18.840 --> 00:10:26.200 larger elliptical galaxy. The collision will induce a burst of star formation and activity, 97 00:10:26.600 --> 00:10:33.000 as well as gravitational waves and radiation. The collision will also affect the 98 00:10:33.039 --> 00:10:39.399 fate of the Solar System and other planetary systems, which may be ejected, 99 00:10:39.840 --> 00:10:48.919 captured, or destroyed by the merger. Three, the Milky Way will face 100 00:10:48.000 --> 00:10:56.399 the effects of the accelerating expansion of the universe driven by dark energy This will 101 00:10:56.440 --> 00:11:01.600 cause the galaxy to become more isolated and detached from other galaxies as the space 102 00:11:01.679 --> 00:11:09.039 between them grows faster than the speed of light. Eventually, the galaxy will 103 00:11:09.080 --> 00:11:13.360 lose contact and visibility with the rest of the universe and will only be able 104 00:11:13.440 --> 00:11:22.039 to observe its own gravitationally bound structures. The galaxy will also experience a cooling 105 00:11:22.240 --> 00:11:28.320 and dimming of its stars as they age and consume their fuel. The galaxy 106 00:11:28.360 --> 00:11:33.039 will enter a phase of heat death, where no more stars or planets can 107 00:11:33.120 --> 00:11:39.200 form, and all forms of energy and information will be lost. The Milky 108 00:11:39.240 --> 00:11:43.960 Way is a fascinating and complex system that offers us a glimpse into the history 109 00:11:45.080 --> 00:11:50.279 and diversity of the universe. It is also our home and our destiny, 110 00:11:50.639 --> 00:11:56.399 as we are part of it and influenced by it. By studying and exploring 111 00:11:56.440 --> 00:12:01.519 the Milky Way, we can learn more about ourselves and are placed in the cosmos.