英语听力：自然百科 穿越银河系的旅行 Through Milky Way—29

And every faint smudge of light you are looking at is a galaxy. For Richard Ellis, it's a galactic treasure trove. So much like an archaeologist/, we piece together history by digging into deeper and deeper layers. So a cosmologist like myself, uses

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—30

We've transported the earth 3 billion years into the future. The sky is dominated by a massive galaxy called Andromeda. The view looks peaceful enough. But whats about to happen is one of the greatest calamities in the universe. The clues lie in thes

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—32

A new galaxy is formed where, instead of the discs that the original galaxies have, where all the stars are going around more or less on a plane. Instead the stars are going every which way just like the elliptical galaxies that we see. And so we are

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—33

Venus is closer to the Sun, Mars is farther from the Sun. And there is a zone in between, the blazing hot furnace Venus, the frigid Mars. That zone in between we call a habitable zone and the earth lies smack in that thing where water would be in liq

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—34

One type of giant planet orbits very close to its star, we call them hot Jupiters because these Jupiter-like planets are so close that they are blowtorched by the intense heat from the star. The other sort of planet we have found is also bizarre. Wev

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—28

The first stars in our Milky Way were fearsome high-octane stars, burning their hydrogen fuel at tremendous rates, rushing through their life cycle. They like the rockslides. They live fast and die young. They run out of their fuel very quickly and e

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—27

But our time traveling isnt yet over. There is still the question of how the first galaxies kindled the very first stars. We are on a journey visiting the Dark Ages, a time over 12.5 billion years ago. The sight is spectacular. The sky is ablaze with

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—26

So what we are looking at is a region about 200 million light years across which is actually just a small part of our really big simulation that we call Bolshoi which is Russian for big. Everything that you see here is actually completely invisible.

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—25

What happens is that, first the dark matter forms the structure, the ordinary matter then follows the dark matter. The ordinary matter is hydrogen and helium at this stage. And the hydrogen and helium fall/ to the center of the dark matter halos that

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—24

Its extremely frustrating because this region, this time period holds within it, in some sense, the rose headstone of / galaxy formation. But there are clues as to what was happening inside those dense hydrogen clouds. Look back even further in time

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—23

But dark matter does more than simply holds galaxy like ours together. Astronomers think it binds the Milky Way into an extraordinary structure along with billions of other galaxies. To explore it, we'll take a journey to the very edge of the univers

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—21

Imagine the disc of our galaxy, if you just took a disc of stars and put it there, gravity would tend to make this disc collapse/ into itself and it would immediately just fall together. That is not what we see with the galaxy. Whats actually going o

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—22

All of the galaxies, all of the stars, and gas and dust and planets, and everything else that we can see with our greatest telescopes represent about half of one percent of whats actually/out there. The rest is invisible. It is mostly some mysterious

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—14

Its a stunning location, but its also mysterious. These stars are not just close together. They are on the move at enormous speeds. Going to the heart of a galaxy might not be the similar to going to an amusement park. The rides are some similar to h

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—15

Each tag is whipping around the center of the galaxy, the particular, the most striking thing you will notice is the motion of SO2.So SO2 goes on an incredible roller-coaster ride. It comes whipping around and then back out. Something with tremendous

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—16

The glowing region is the accretion disc, star debris falling inward, would turn round in the maelstrom heated by frictions to such high temperatures that it glows white hot. So at the center of our galaxy, we do have a black hole. We now know that t

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—20

They were once thought to mark the outer limits, but today astronomers believe the Milky Way galaxy is much bigger than what we can see. To understand why, we will travel to the stars of the outer galactic disc. Far from our usual place in space, we

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—9

Like nebulae which spawn stars, it is made of gas and dust. But that's where most similarities end. For Alex Filippenko, it represents an intriguing industrial zone within our galaxy where the elements from which our world is made or manufactured. Wh

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—10

To understand how these calamities occur, astronomers need to catch a massive star in its death throes. Astronomers are like detectives. We have to figure out what's going on in the universe, sometimes based on a minimum number of clues. And in the c

英语听力：自然百科 穿越银河系的旅行 Through Milky Way—11

Once theyve caught the light of a dying star with their state of our telescopes. The detective work can begin. We collect that light and we analyze it in great detail in order to determine whats going on, whats the chemical makeup of the star, whats