In p42 Visible light questions: 1.What colors are on the visible light spectrum? 2.What units are the wavelengths of light measured in? 3.What is the range of wavelengths of visible light? 4.Which color has the longest wavelength? 5.Which color has the shortest wavelength? 6.What color would you expect to see at a wavelength of 0.45 micrometers? 7.What color would you expect to see at a wavelength of 0.7 micrometers?

Fri 9/25 Next time: INB quiz #3 That’s me!

Hertzberg-Russel diagrams In the early 1900s, two astronomers -- Ejnar Hertzsprung in Denmark and Henry Norris Russell in America They used distance measurements to convert the APPARENT magnitude of each star into its ABSOLUTE magnitude. On a graph of absolute magnitude (luminosity) versus spectral type (temperature) most of the stars fell in a diagonal stripe - a pattern that became known as the MAIN SEQUENCE. It’s a plot of Surface Temperature vs. Luminosity Luminosity is the brightness of stars compared to the brightness of our sun as seen from the same distance. This graph became known as a "Hertzsprung-Russell" (or HR) diagram

The H-R Diagram of a Star Cluster All Stars born at the same time (within a couple million years, if a large molecular cloud), only differ in their mass Stars age at different rates, depending on their mass. More mass = faster evolution ab10_E.html

HR main sequence turnoff

Another Quick Overview First… Stars burn through their hydrogen, evolve off Main Sequence to become Red Giants, then die in various ways High mass stars evolve fast,… Low mass stars evolve slowly

Globular Cluster HR Diagram – 13 Billion Year Old Cluster!

Hertzberg-Russel diagrams Different kinds of HR diagrams look at different aspects of stars. Things to look at: Blue = hot temps, Red = low temps.

Herztsprung-Russell Diagram

Thru: pg 50 Hertzsprung Russell Diagram sheet.

Out p 53 Space Telescope Imaging Spectrograph Hubble’s Instruments Wide Field Camera 3 Advance Camera for Surveys Cosmic Origins Spectrograph Near Infared Camera and Multi-Object Spectrometer Fine Guidance Sensors -At the end of each arrow, write the function of the appropriate instrument. We collect all of this information about space by remote sensing with instruments. Some are sent into space on probes, space stations and orbiting telescopes. Some of the telescopes are in large observatories are on Earth but some(like the Hubble Telescope) are sent past our atmosphere. –Why is it better to collect data with instruments that are outside of the Earth’s atmosphere?