Need some help with Astronmy homework

Can anyone help me answer this question? Please...

Why do astronomers get different looking images from uv, ir, and xray
satellite telescopes compared to visible light images from earth-based
telescopes?

Thanks!!

Christie wrote:

Can anyone help me answer this question? Please...

Why do astronomers get different looking images from uv, ir, and xray
satellite telescopes compared to visible light images from earth-based
telescopes?

Thanks!!

Differences in acquired imagery are mainly due to objects having different
surface temperature, spectrally dependent reflection, and
spectrally-dependent absorption from any intervening interstellar
material. Start by searching on "Planck" and "blackbody curve". If you
know how to use Excel, try programming up the blackbody curve as part of
your homework. The total radiance of an object increases with its surface
temperature. The peak radiance is given by 2897.8/(temperature in ºK).
Your body is about 300ºK, so you radiate the most energy at about 9.66
microns, in the long wave infrared band, and you radiate almost nothing in
the visible spectrum. The overhead sun can be modeled as roughly a 5900ºK
blackbody, which gives a peak radiance at 0.491 microns, and almost no
long wave infrared radiance. Telescopes use different sensors for
different spectral bands of interest, so the only objects imaged by a
given sensor are those that radiate or reflect in that particular sensor's
responsivity passband.

"Christie" wrote in message
...
Can anyone help me answer this question? Please...

Why do astronomers get different looking images from uv, ir, and xray
satellite telescopes compared to visible light images from earth-based
telescopes?

Thanks!!


Go read your textbook or ask your teacher. Thats what they get paid for and
stop trolling for people to do your homework!

Christie wrote:

Can anyone help me answer this question? Please...

Why do astronomers get different looking images from uv, ir, and xray
satellite telescopes compared to visible light images from earth-based
telescopes?

Thanks!!

Think about the sources of uv, ir, and xray radiation... what processes
create that radiation.

"Christie" wrote in message
...
Can anyone help me answer this question? Please...

Why do astronomers get different looking images from uv, ir, and xray
satellite telescopes compared to visible light images from earth-based
telescopes?

Hi Christie,

Glad to see someone be honest and just say it is for homework, rather than
posing as if they are very interested in what is obviously a homework
question :-)

First, get rid of the red herring. It isn't space-based vs. earth based. The
only difference for a satellite is it is above the atmosphere, which means
there isn't distortion or absortion. You could orbit a similar sized optical
scope and you would still have the same differences.

As for UV, think extremely hot. Very hot objects have most of their
radiation in the UV. The hotter they are, the bigger the magnitude
(brightness) difference in UV compared to visible light. As an object gets
hotter, the bulk of its radiation is emitted in shorter and shorter
wavelengths. Although it sounds counter-intuitive, the shorter wavelengths
contain more energy.

Then consider dust. Dust is opaque at visible wavelengths. But it is more
transparent at IR wavelengths. And, dust clouds absorb radiation and re-emit
it at IR.

That should get you started.

Clear Skies

Chuck Taylor
Do you observe the moon?
Try the Lunar Observing Group
http://groups.yahoo.com/group/lunar-observing/
Lunar Picture of the Day http://www.lpod.org/
************************************


Thanks!!

The answer to that question can fill a 100 page essay. Try Astronomy 6th
edition by Dinah L. Moche. That is a self teaching guide for astronomy that
will provide all of the answers.

On Mon, 22 Mar 2004 09:37:49 -0500, Christie wrote:

Can anyone help me answer this question? Please...

Why do astronomers get different looking images from uv, ir, and xray
satellite telescopes compared to visible light images from earth-based
telescopes?

Thanks!!

You're going to get a bunch of answers which may not satisfy your
curiosity or comprehension level. (You forgot to say what grade
you are in, and how much science you've had before.) Some will
assume that you are familiar with college level physics, while
others may think you are in sixth grade.

Without knowing this, lets try to put things in the simplest terms . . .

When we look at a rainbow, we see a number of colors that our eyes
can perceive. There are, however, a great many more colors that
our eyes cannot see. These include various shades of infrared (ir),
ultra-violet (uv) and x-rays, to name a few. And though we cannot
detect them directly, they are, none-the-less, very real.

Now, all material things interact with light. They reflect, absorb,
transmit or radiate light according to their particular physical
properties, AND the kind of light involved. When you look at the
campus at your school, you'll see a variety of colors in clothing,
buildings, sky, grass, trees, and so forth. But you are still seeing
only a limited number of colors. The universe is even more colorful
since it deals with light of many more hues than we can see.

In fact, the types of invisible light you mentioned are actually
groups of colors themselves. There are reddish-and bluish-xrays,greenish-
and orangish-ultraviolet waves, and . . . you get the
picture? At the moment, we don't have any cameras which can look at
the universe in all of the colors, all at once. We, and our machines,
are contrained to look at a small range of colors at a time.

You can see the effect for yourself if you have some pieces of colored
(transparent) cellophane (or photographic filters) to look through.
Look through a red filter, and you will mostly light and dark areas
where red is reflected (bright), or where it is not (dark). View the
same scene through a green or blue filter, and you see different areas
highlighted. Some of the brights are darker, and some of the dark areas
rather bright.

Since our detectors are only good for specific groups of color, it
should be no surprise that the views they see differ from one another
when the color group is different.

Hope this helps.
Larry G.



--
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

"LarryG" wrote in message
news
On Mon, 22 Mar 2004 09:37:49 -0500, Christie
wrote:

Can anyone help me answer this question? Please...

Why do astronomers get different looking images from uv, ir, and xray
satellite telescopes compared to visible light images from earth-based
telescopes?

Thanks!!

You're going to get a bunch of answers which may not satisfy your
curiosity or comprehension level. (You forgot to say what grade
you are in, and how much science you've had before.) Some will
assume that you are familiar with college level physics, while
others may think you are in sixth grade.

Without knowing this, lets try to put things in the simplest terms . . .

When we look at a rainbow, we see a number of colors that our eyes
can perceive. There are, however, a great many more colors that
our eyes cannot see. These include various shades of infrared (ir),
ultra-violet (uv) and x-rays, to name a few. And though we cannot
detect them directly, they are, none-the-less, very real.

Now, all material things interact with light. They reflect, absorb,
transmit or radiate light according to their particular physical
properties, AND the kind of light involved. When you look at the
campus at your school, you'll see a variety of colors in clothing,
buildings, sky, grass, trees, and so forth. But you are still seeing
only a limited number of colors. The universe is even more colorful
since it deals with light of many more hues than we can see.

In fact, the types of invisible light you mentioned are actually
groups of colors themselves. There are reddish-and bluish-xrays,greenish-
and orangish-ultraviolet waves, and . . . you get the
picture? At the moment, we don't have any cameras which can look at
the universe in all of the colors, all at once. We, and our machines,
are contrained to look at a small range of colors at a time.

You can see the effect for yourself if you have some pieces of colored
(transparent) cellophane (or photographic filters) to look through.
Look through a red filter, and you will mostly light and dark areas
where red is reflected (bright), or where it is not (dark). View the
same scene through a green or blue filter, and you see different areas
highlighted. Some of the brights are darker, and some of the dark areas
rather bright.

Since our detectors are only good for specific groups of color, it
should be no surprise that the views they see differ from one another
when the color group is different.

Hope this helps.
Larry G.

A question just occured to me. Now theoreticly we have a bottom limit to the
spectrum, the point where something is radiating no energy. Maybe a black
hole if you don't count Hawking radiation. But is there an upper limit. We
have Gamma waves and it seems to be a large portion of the spectrum. I mean
is it possible that there is something above gamma waves till you reach the
Plank scale or is everything above x-ray considered gamma?

On Tue, 23 Mar 2004 03:32:35 -0600, Fitzdraco wrote:

A question just occured to me. Now theoreticly we have a bottom limit to
the
spectrum, the point where something is radiating no energy. Maybe a black
hole if you don't count Hawking radiation. But is there an upper limit.
We
have Gamma waves and it seems to be a large portion of the spectrum. I
mean
is it possible that there is something above gamma waves till you reach
the
Plank scale or is everything above x-ray considered gamma?

As far as I know, we have no instruments to probe beyond gamma, or
even deal well with it spectroscopically, although a bubble-chamber
or other particle detector might come close.

And there is the matter of the granularity of space, time and the
particles thought to carry fundamental forces. Once the energy
becomes so high, it is likely to show signs of disconinuity.
Ultimately, super-high energy photons may resemble or produce
actual matter. But a physicist would really be more knowledgeable
of such things.

Cheers,
Larry G.




--
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

Larry G. wrote:
As far as I know, we have no instruments to probe beyond gamma, or
even deal well with it spectroscopically, although a bubble-chamber
or other particle detector might come close.

This might be a good time to point out that the various ranges of
electromagnetic radiation, which includes the gamma rays and X-rays
on one end as well as the radio waves on the other, are not precisely
defined.

Thus, for example, although gamma rays are generally considered to
be higher energy (that is, shorter wavelength and higher frequency)
EM radiation than X-rays, there are nonetheless so-called "hard" X-rays
that are shorter in wavelength and therefore higher in energy than some
"soft" gamma rays.

The reason for this weirdness is largely historical. X-rays were
discovered when Roentgen observed luminescence being produced by
radiation emitted from a cathode ray tube (that were not the cathode
rays themselves); gamma rays were discovered during the investigation
of radioactive substances. Both were found to be electromagnetic in
nature when they were diffracted by crystals, in 1914. However, by
that time, it had become customary to think of gamma rays as being
produced by nuclear processes (so are alpha rays--helium nuclei--and
beta rays--electrons), and X-rays not, and the distinction largely
continues.

In any event, there is no "upper end" to gamma radiation. They are
simply the highest energy EM radiation range we speak of. *If* there
came to be discovered a new phenomenon that emitted even higher energies
of EM radiation than are typically emitted by nuclear processes, we
might then cap the gamma radiation range and tack on the new range on
top, but that hasn't happened...yet.

As a matter of fact, it was hypothesized, early in the 20th century,
that cosmic rays were a form of EM rays even higher in energy than
typical gamma rays. This turned out to be untrue: cosmic rays are
small particles, mostly protons, accelerated by distant magnetic fields.
Compton discovered this by observing that different latitudes received
different cosmic ray fluxes, according to a function that could be
derived from the Earth's magnetic field. This established that the
cosmic rays were not electromagnetic rays (which aren't deflected by
a magnetic field), but were instead charged particles.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt