Name: 神秘的なブラックホール (Mysterious Black Holes)
Uploaded: 2021-01-14T05:14:34.000Z
Duration: 21 min 50 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

Intense stellar winds have sculpted a majestic castle of gas. Inside these giant columns,

Yet for the dying stars that set this process in motion, the consequences are grim.

Supernovae leave in their wake a range of bizarre objects. Among them, a tiny dense

You form an object that we call a neutron star, which is something that has the mass

of our sun, but a radius of only about six miles or so. That is a very compact object.

Every centimeter cubed of that mass has a mass of a hundred-million tons.

Because of its intense gravity, a neutron star is a perfect sphere, with a surface like

It has the mass of the star, but it only has the size of a city. And the structure of that

matter is that it's like ordinary matter, where there are electrons and so on orbiting

around, ah, ah, nuclei, but with all the electrons sort of squashed into the nuclei and the particles

So something that we think of as incredibly dense, like lead, is really mostly empty space.

And if you squish all the empty space out of it and get the nuclei right up next to

each other, that's something that has the density of a neutron star.

The existence of neutron stars was first proposed in the 1930s. It wasn't until the '60s that

Within the remnants of some supernovae, astronomers detected a presence that pulsed with radio

When these were discovered by a graduate student in England in the 1960s, the supervisor thought

that they should not announce the discovery for a few months, partly in order to check

the -- that it was a genuine astronomic object.

But also because of the possibility that this might be an alien signal. And in fact, the

code name for the object in the early days was LGM, to stand for Little Green Men.

The Crab Nebula is the shell of the same supernova that caught the attention of so many cultures

Deep within, astronomers found a pulsar, a neutron star that spins rapidly, emitting

Now scientists are using the Hubble Space Telescope to zero in on the pulsar -- The

star on the left. It is spewing waves of radiation that have etched circular patterns in the

Yet, some dying stars meet a fate that is stranger still. Nature, it seems, has contrived

Early in this century, Albert Einstein speculated about a star with such intense gravity that

absolutely nothing, not even light, escaped its grasp. He at once dismissed this prospect

The notion that you could squeeze something without limits, you know, right down to a

zero size, was considered basically absurd and offensive.

And so there was a sort of temperamental reaction against this idea of total gravitational collapse

What once seemed beyond reason now defines the frontiers of science. Astronomers believe

that when a large star explodes, enough matter can collapse into its core that it literally

If the mass of that core is large, is larger than about three times the mass of our sun,

nothing at the end can stop the final collapse. Gravity wins the final battle and the thing

From our vantage on earth, we define our universe by familiar criteria. But black holes defy

discovery. What after all can we detect of objects that emit no light?

The fact is we don't have enough cases where we really know what's going on to be able

We'd like to know, for example, if the black holes are a little different from the theory

and at the moment we're just at the stage of finding out whether there are good candidates

for black holes, things that we think can't be neutron stars, can't be white dwarfs, can't

The usual argument for a black hole is somebody shrugging and saying, "Well, what else can

In 1991, astronauts placed one of the milestones of modern science into orbit. The Compton

Gamma Ray Observatory monitors high-energy radiation that pummels our upper atmosphere.

In 1994, it picked up a sudden eruption in the Constellation Scorpius.

Astronomers around the world zeroed in on the source. A network of radio telescopes

stretching from the Caribbean to Hawaii recorded a rare specter.

This is the object that came into view. Matter rushing into it is sending out jets of intense

This week marks the culmination of a year-long effort to study the object. Teams in eight

countries are simultaneously training their most advanced technology on it, to discover

From a telescope in the Andes Mountains, in the heart of Chile, the astronomer Charles

Bailyn was the first to pinpoint its location.

Now he's venturing back to the observatory at Cerro Tololo -- to prove once and for all

It's the strange objects that always tell you the most about, ah -- about the universe

and about science. So, if you want to increase your knowledge of how gravity works, for example,

you don't look at things falling on the Earth, which we understand.

You look at the really, really strong gravitational fields that happen near black holes. Ah, and

those are the things where our current theories might possibly break down.

No one has ever proven conclusively the existence of a black hole. If ever there was an opportunity,

Looming within the dense star fields of our Milky Way, 10,000 light years away, this is

the brightest and most spectacular object of its kind. What's more, it's not alone.

A normal star circles the object in a dance of death. Gas from the star flows into the

object through a disk, while jets of radiation shoot from its poles.

So powerful is the object's gravity, that the companion star's shape is being distorted

and squashed, causing its appearance to dim, then brighten as it makes its orbit.

As it goes around, ah, the black hole, we're gonna start seeing the edge-on, rather than

So it's gradually going to get fainter because in the time we're watching it tonight it's

going to go, uh, from almost side-on to almost end-on.

Though Bailyn and his team can't view the object directly, they can study its companion.

If you remember in Alice in Wonderland there is a Cheshire Cat. The cheshire cat disappears

from view and only leaves its smile behind to be seen. Black holes have this property.

They disappear from the eye, but they leave their smile behind. They leave their gravitational

force behind and it is by that that we then see them and are able to infer their properties.

To prove that his subject is a black hole, Bailyn must measure its mass at at least three

times our sun. The only way he can do that is by studying the effect of its gravity on

It takes two-and-a-half days to make it all the way around, and in order to get that far,

ah, in that amount of time, it's got to go at several hundred kilometers a second, ah,