Astronomy 1020Spring_2015

Day-22Stellar Astronomy

Course Announcements• Exam-2: Fri. 3/20 Chapters 5 & 6• I will collect the L-T books at this time.• Drop “Proper Motion of a Star” lab• Smartworks Chapters 6: Due Mon. 3/23• Apr. 2 – Last day to drop a class.• Midterm grades are delayed until Thursday

• Based on Exam-1 and labs

• THURSDAY: Dark Sky Observing Session: 8:30pm at the Observatory. Map is on apsu.edu/astronomy

• WEATHER DEPENDENT

Spectrographs disperse the incoming light into its component wavelengths.

Lets astronomers study the spectrum of an object’s light.

The atmosphere does not transmit all light. Nearly all X-ray, ultraviolet, and infrared

wavelengths are blocked. Satellites are needed for these wavelengths.

Radio telescopes are large, steerable parabolic dishes with antennas.

Allow astronomers to study radio waves. Wavelengths of a centimeter to about 10 meters. Radio waves can pass through gas and dust.

Single radio telescopes have poor resolution due to the long wavelengths.

Interferometric arrays combine the signals from many telescopes, increasing resolution.

Two electromagnetic waves in the same location will produce interference.

The waves will either enhance or detract from each other, resulting in constructive or destructive interference.

This can result in spectral dispersion.

CONNECTIONS 6.2

Airborne observatories: raise the telescope above clouds and water vapor (infrared astronomy).

Satellites in orbit: detect wavelengths that the atmosphere blocks (ultraviolet and X-rays).

Can produce very sharp images (e.g., the Hubble Space Telescope).

Concept Quiz—Mountain Telescopes

Why do astronomers build telescopes on mountains?

A. to be closer to the objects they are observing

B. to minimize the effects of the atmosphere

C. to observe wavelengths such as X-rays or ultraviolet light

Spacecraft have visited or flown by all the classical planets.

Flybys and orbiters observe from afar. Landers, rovers, and atmospheric probes

are more direct, and some can return samples.

Particle colliders probe physics of protons, neutrons, neutrinos, and atomic nuclei.

Can help astronomers understand the early universe and structure formation.

In a few cases, astronomers capture things other than light:• Neutrinos—light subatomic particles that are

extremely difficult to detect.• Gravitational waves—distortions in

spacetime predicted by relativity.

Concept Quiz—Telescopes

Pick the incorrect answer: Why build telescopes onthe ground when we can launch them into space?

A. Ground-based telescopes are useful for studying visible and infrared light.

B. Ground-based telescopes get much higher resolution.

C. They are far cheaper to build and fix than space-based telescopes.

Computers are essential for astronomy. Help in data analysis. Simulations and models help to investigate

complex situations.

A microwave telescope provided more evidence for the Big Bang, revealing the presence of the cosmic microwave background radiation (CMB).

Technology and science are symbiotic.

New technological advances lead to new methods of scientific observation and experimentation.

New scientific discoveries spur improvements in instrumentation.

PROCESS OF SCIENCE

Exam-2 To Here