Week 6 - Lecture 1 The Time Machine, Part 1

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Do curso por Rutgers the State University of New Jersey

Analyzing the Universe

51 classificações

Rutgers the State University of New Jersey

Analyzing the Universe

51 classificações

Using publicly available data from NASA of actual satellite observations of astronomical x-ray sources, we explore some of the mysteries of the cosmos, including neutron stars, black holes, quasars and supernovae. We will analyze energy spectra and time series data to understand how these incredible objects work. We utilize an imaging tool called DS9 to explore the amazing diversity of astronomical observations that have made x-ray astronomy one of the most active and exciting fields of scientific investigation in the past 50 years. Each week we will explore a different facet of x-ray astronomy. Beginning with an introduction to the nature of image formation, we then move on to examples of how our imaging program, DS9, can aid our understanding of real satellite data. You will using the actual data that scientists use when doing their work. Nothing is "canned". You will be able to appreciate the excitement that astronomers felt when they made their important discoveries concerning periodic binary x-ray sources, supernovae and their remnants, and extragalactic sources that have shaped our understanding of cosmology.

Na lição

To the Ends of the Universe; Quasars, 3C273, and beyond

This week we wrap things up with trips to galaxies and exotic objects, seen long ago and far away. The mysterious quasars provide clues about the way our Universe is evolving in time. They are incredible objects (actually, come to think of it, what isn't incredible in the x-ray sky?) discovered almost exactly a half century ago, quite by accident. We will explore the astonishingly prodigious x-ray output of 3C 273, one of the nearest ones, at a mere 2.5 billion light years away.

Week 6 - Lecture 1 The Time Machine, Part 1 7:34

Lecture 2 The Time Machine, Part 2 23:03

Lecture 3 The Time Machine, Part 3 9:42

Lecture 4 The Time Machine, Part 4 20:57

Lecture 5 To the Ends of the Universe: The Cosmic Distance Scale -- Part II 20:20

Conheça os instrutores

Dr. Terry A. Matilsky
Professor
Physics and Astronomy

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Hi gang and welcome back to Analyzing the Universe.

One of the most remarkable and useful characteristics of our universe is that as

we look out into space, we are also looking backwards in time.

Since light travels about 186,000 miles in one second.

When we

look at the sun, whose distance is about 93 million miles,

we are seeing it as it was about eight minutes ago.

Thus, our astronomical observations can yield a history

of our universe by examining objects very far away.

However, we had no idea of the vastness and hence

antiquity of the universe ,until the 1920's when Edwin Hubble discovered some

innocuous appearing stars in a nebula or cloud called M31.

These objects were Cephei variable stars which we have encountered before,

and which have the unique feature that they all say, actually growing and

shrinking over a period of several days. Moreover the amount of time it takes

for these starts to pulsate is directly related to their intrinsic luminosity.

How bright they really are.

Once we know an objects true brightness it is a simple

matter to use it's apparent brightness to calculate it's distance from us.

It was

undoubtedly with a trembling hand that Hubble calculated the distance

to M31, our nearest spiral galaxy neighbor.

It was over one million light years away. Just

imagine light that can travel over seven times

around the world in one second takes over a million

years to reach us from M31. Thus,

when you go out on a clear Autumn night and find M 31 in the

Constellation of Andromeda you are seeing that object

as it actually was when the first human life creatures

began to walk the earth. With the knowledge

of the distance to far flung astronomical bodies, a wonderful side benefit emerged.

We were able to find the dimensions of an object from it's angular size in the sky.

We did this recently when we discussed Cass-A.

But here we'll calculate the size of M31. Modern, more accurate measurements

place it about two million light years away and its apparent

size in the sky is three degrees. About the same

apparent diameter as six full moons, placed side

by side. What is the size of the Andromeda Galaxy?

So we have a big skinny triangle.

The angle of opening is three degrees. Which is equal

to about 1 20th of a radian.

We have to get everything in units or non-units of radian so that we can make

the comparison of the size in the sky and distances together.

And we know we have six full moons

spanning M31. And if the

distance to M31 is 2 million

light years. Then this

distance here, the size

of andromeda actually is

going to be 2 million light

years divided by 20. Or

approximately 100,000

light years across. With this

awesome revelation about the size of the universe.

And some of its constituents and avalanche of

observations opened our eyes to yet more astounding facts.

With this study of other galaxies

and its exceedingly interesting relationship emerged.

The further a galaxy was away from us measured by the seffiad

variables and other techniques, the faster it appeared to be

moving, as measure from the doppler shift of it's spectral features.

It was as if the entire universe was somehow exploding into space.

The faster each piece was moving, the further it would

be away from anywhere else after a given amount of time.

Because of this unique relationship between velocity and distance,

known as the Hubble Law in honor of its discoverer, we now

had a new method for measuring distances to really remote objects.

All we need to do is measure the doppler red

shift from the energy spectrum and deduce the distance from a

very simply equation. Velocity equals

a constant H, the Hubble constant, times the

distance it is away. Here, H is the Hubble

constant and has been experimentally determined to be about

70 kilometers per second

per mega parsec. Thus for

each million parsecs in distance away from us, which is

about three million light years, the object's velocity

increases by 70 kilometers per second.

So for example, an object whose spectrum exhibits

a velocity of 500 kilometers per second, would be at a

distance of about 7 mega-parsecs from us. The

stage was now set for the discovery of the quasars.

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