Lecture 6

Question 1

Imaging

Answer 1

Taking pictures of astronomical objects (Eg. Planets, stars, galaxies)

Question 2

Spectroscopy

Answer 2

Breaking light into spectra, i.e. analyzing characteristic electromagnetic emission or absorption features of astronomical objects

Question 3

Timing

Answer 3

Measuring how light output varies with time ( or more generally, how emission of electromagnetic radiation varies with time)

Question 4

Imaging

Answer 4

Astronomical detectors usually record only one color of light at a time
Several images must be combined to make full color pictures
Can record forms of light our eyes can’t see

Question 5

Spectroscopy

Answer 5

A spectrograph separates the different wavelengths of light before they hit the detector
Graphing relative brightness of light at each wavelength shows the details in a spectrum

Question 6

Timing

Answer 6

A light curve represents a series of brightness measurements made over a period of time

Question 7

What are the most important properties of a telescope?

Answer 7

Collecting area determines how much light a telescope can gather
Angular resolution is the minimum angular separation a telescope can distinguish

Question 8

What are the 2 basic designs of telescopes

Answer 8

Refracting telescopes focus light with lenses
Reflecting telescopes focus light with mirrors
The vast majority of professional telescopes are reflectors

Question 9

What do astronomers do with telescopes

Answer 9

Imaging, Spectroscopy and Timing

Question 10

how does Earths Atmosphere affect ground based observations

Answer 10

The best ground bases sites for astronomical observing are

Calm
High
Dark
Dry

Question 11

Light Pollution

Answer 11

Scattering of human made light in the atmosphere is a growing problem for astronomy

Question 12

Where are the best observing sites

Answer 12

Atop remote mountains in hot, dry climate

Question 13

Transmission in Atmosphere

Answer 13

Only radio and visible light pass easily through Earths atmosphere
We need telescopes in space to observe other forms

Question 14

How can we observe invisible light?

Answer 14

A standard satellite dish is essentially a telescope for observing radio waves

Question 15

Radio telescopes

Answer 15

A radio telescope is like a giant mirror that reflects radio waves to a focus
The Arecibo radio telescope had a diameter of about 300 meters

Question 16

Infared and Ultraviolet Telescopes

Answer 16

Infared and Ultraviolet light telescopes operate like visible light telescopes but need to be above atmosphere to see all wavelengths

Question 17

X ray telescopes

Answer 17

X ray telescopes also need to be above the atmosphere
Focusing of X rays requires special mirrors
Mirrors are arranged to focus x ray photons through gazing bounces off the dish

Question 18

Gamma - Ray Telescopes

Answer 18

Gamma Ray telescopes also need to be in space
Focusing Gamma rays is extremely difficult, and high energy gamma rays are also rare

Question 19

How can we observe invisible light?

Answer 19

Telescopes for invisible light are usually modified versions of reflecting telescopes
Many of the telescopes used for observing invisible light are in space

Question 20

What kind of waves can be observed with ground based telescopes

Answer 20

Visible light and Radio waves