{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

# Lec29 - Class News F o r F r i M a y 8 Read Ch 22 Do Online...

This preview shows pages 1–8. Sign up to view the full content.

Class News For Fri. May 8: – Read Ch. 22 + Do Online Quiz 11 For Mon. May 11: – Read Ch. 23 + Do Online Quiz 12 – Extra Credit Project Due

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Summary: Doppler shift & Hubble’s law • Doppler shift: V = c Δλ / λ o – V= velocity – c = speed of light Δλ = λ - λ o =Doppler shift from rest wavelength λ o • Hubble’s law: V = H o d –d= distance; H o = Hubble’s constant
Pop quiz Suppose the Hubble constant is H o =60 (km/s)/Mpc, and you observe a galaxy for which spectral lines normally at a wavelength λ o =600 nm are found to be at λ =660 nm. 1. Is the galaxy moving toward or away from us? 2. About what speed is it moving? (Recall c=300,000 km/s). 3. According to Hubble’s law, what is its distance, in Mpc? 4. About how long ago did the light we see leave this galaxy?

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Pop quiz Suppose the Hubble constant is H o =60 (km/s)/Mpc, and you observe a galaxy for which spectral lines normally at a wavelength λ o =600 nm are found to be at λ =660 nm. 1. Is the galaxy moving toward or away from us? 2. About what speed is it moving? (Recall c=300,000 km/s). 3. According to Hubble’s law, what is its distance, in Mpc? 4. About how long ago did the light we see leave this galaxy? λ > λ o => redshift => away c Δ λ / λ o = 0.1c = 30,000 km/s d= 30,000/60 = 500 Mpc d=~ 500*3 = 1500 Mly => t= 1.5 billion years ago
The Age of the Universe In the context of an expanding Universe… H o tells us the rate at which galaxies are moving apart from one another so if we run he clock backward to when the galaxies were all at one point then 1/H o tells us how long it took the Universe to expand to its current size if the expansion rate is constant; so 1/H o only estimates age of Universe

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
The Age of the Universe Our best measurement of the Hubble Constant… comes from the Wilkinson Microwave Anisotropy Probe announced by NASA in February 2003 • H o = 71 km/s per Mpc This gives age of the Universe, 1/H o = 13.7 billion years
Lookback Time

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern