Transcript Viewing the Universe - Horace Mann Webmail

Viewing the Universe
Astronomers gather information about
objects throughout the universe by detecting
various kinds of energy given off by these
objects.
We call the various types of energy
electromagnetic radiation, or energy that can
travel through space in the form of waves.
The electromagnetic spectrum
includes radio waves, infrared
radiation, visible light, ultraviolet
radiation, x-rays and gamma rays.
Telescopes collect and focus
different types of electromagnetic
radiation
Radio astronomy image
Seyfert galaxy
NGC 4151
Infrared image of young planetary nebula known as
BD+303639
Visible image of four galaxies, known as
Hickson Compact Group 87 (HCG 87)
Ultraviolet image of the sun
ETACAR NEBULA USING X-RAY IMAGING
Pulsars in the Crab Nebula using Gamma Imaging
The Hubble Space Telescope is a
reflecting telescope with a mirror.
Because it is above our
atmosphere, it can collect images
with more detail.
The Hubble can also collect
ultraviolet and infrared radiation.
There are two types of visible light
telescopes
Refracting telescopes use a lens to focus light
Reflecting telescopes use a mirror to focus
the light.
Large modern telescopes are now all
reflecting telescopes.
When we pass visible light through a
prism, it is spread out to make a
continuous range of its different colors.
We call this
ROY G. BIV
Red, Orange, Yellow, Green,
Blue, Indigo and Violet
Most large telescopes include a
spectroscope to break visible light
from a stellar object into its
spectrum.
By comparing the star’s spectrum with the spectrum of
elements known on earth, we can infer which elements
are found in that star.
In the next week we will look at three
types of spectra
Continuous spectrum - all of the colors of the visible
spectrum
Emission spectrum - bright lines of color given off
when the gaseous state of an element is excited
Absorption spectrum - spectrum with black lines or
missing colors given off when light is passed
through a chemical.
We will also learn about the
apparent change in the
wavelengths of light that occurs
when an object is moving toward
or away from the Earth
This is called the Doppler effect.
If a star is approaching the Earth, the light
waves are pushed together. They appear
shorter that they really are. Shorter
wavelengths are characteristic of blue and
violet light. The spectrum appears to be
shifted slightly toward the blue end. We call
this a blue shift.
If a star is moving away, the light waves
expand, appearing longer than they really are.
We call this a red shift.
The more a spectrum is shifted, the faster a
star is moving.
The light from every distant
galaxy shows a red shift.
Every galaxy in the universe seems to be
moving away from the Earth. The universe is
expanding. Galaxies at the edge are racing
away. Galaxies closer to the center are
moving out at slower speeds.