Astronomy 1010-HFall_2015Day-23

Planetary Astronomy

Course Announcements• How is the sunset/sunrise observing going?

• SW-chapter 6 posted: due Fri. Oct. 23

• 1st Quarter Observing night: Tuesday, Oct. 20; 7:30pm

Electronic detectors record photons on pixels. Photons create a signal in the array. CCDs = charge-coupled devices (such as

digital cameras).

The electronically recorded images can greatly exceed photographs in quality.

CCD = astronomer’s detector of choice.

Red Green

Blue

Red Green

Blue

Since it is meant to be separated we don’t call it an aberration. Instead, it is called dispersion

Spectrographs disperse the incoming light into its component wavelengths.

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

Diffraction is much more efficient at separating light into its colors than dispersion

Look closely enough at stars and they aren’t just points of light but rings, too

SpectrumBut visible light is only one type of electromagnetic radiation (light) emitted by stars Astronomers are truly interested in the entire spectrum of Light!

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

wavelengths are blocked. Satellites are needed for these wavelengths.

Consider This Class as Seen in Different Wavelengths of Light!

Orion in Infrared!

HST Views of Orion Nebula showing stars hidden in clouds

http://oposite.stsci.edu/pubinfo/pr/97/13/A.html

Observations at other wavelengths are revealing previously invisible sights

UV

Ordinary visible

Infrared

Map of Orion region

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.

Radio wavelength observations are possible from Earth’s surface

Long Wavelength…poor resolution

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 6.2CONNECTIONS 6.2