A105 Stars and Galaxies

News Quiz Today1st NovaSearch homework due Thursday First Exam on Thursday, Sept. 28

Today’s APOD

Announcements…• Kirkwood Obs. open Weds night 9:00 – 11:30

• Rooftop Session, Sept. 28, 8:30

Upcoming Events• Moon Festival at Kirkwood Obs.

–Wednesday, Oct. 4, 8:30-10:30–sponsored by the Asian Culture

Center

• Transit of Mercury–Nov. 8, 2:15 PM - Sunset

Space vs. Ground-Based Observatories

• Space-Based Advantages– Freedom from atmospheric blurring– Observe at wavelengths not transmitted by air

• Ground-Based Advantages– Larger collecting power– Equipment easily fixed

• Ground-Based Problems– Weather, humidity, and haze– Light pollution

Light Pollution

• artificial lighting threatens all observatories on the ground

• shield all outdoor lights

in 6-8 meter telescopes

WIYN TECHNOLOGY

8-10 Meter Telescopes Today• Keck TelescopesGemini North and

South• ESO’s Very Large

Telescope• Subaru• Hobby-Eberly

Telescope and SALT

• MMT Observatory• Magellan• Large Binocular

Telescope

The Twin Keck Telescopeson Mauna Kea

• Two 10-meter telescopes• “segmented” mirrors

– 36 hexagonal segments• Keck I in 1993; Keck II in 1996

ESO’s VLTCerro Paranal, Chile

Four 8.2 meter telescopes– Antu (the Sun)– Kueyen (the Moon)– Melipel (the Southern Cross)– Yepun (Venus - as evening star)

6.5-meter Telescopes

Magellan TelescopesTwin 6.5-m in Chile

Borosilicate honeycomb mirrors

MMT Observatory 6.5-m Telescopealso borosilicate honeycomblocated in southern Arizona

Large Binocular Telescope

Twin 8.4-meter mirrors on a single mount in

southern Arizona

Correcting for Correcting for the Earth’s the Earth’s

AtmosphereAtmosphere

• Even at wavelengths where the atmosphere is transparent, the atmosphere “blurrs” light– Why to stars “twinkle” (scintillation)?– The condition of the sky for viewing is referred to as

seeing– Distorted seeing can be improved by adaptive

optics

Adaptive Optics – Correcting distortions caused by the Earth’s Atmosphere

How does it work???

UH-88”, Courtesy W.Brandner, 0.65” seeing

4’40”

5”

>220 stars in 5”x5”

Gemini N/Hokupa’a-QUIRC (U of H/NSF)

The Power

ofAdaptive

Optics

• text

The importance of image quality

typical ground-based image

Hubble image

WIYN image

The Ring Nebula

New Telescopes to Answer New Questions

• 20 and 30-meter telescopes• 8-meter survey telescope• James Webb Space Telescope• Virtual Observatory

Adaptive Optics will be a key

component of 20 and 30 meter

telescopes

Lasers will produce artificial stars in the

sky to help focus starlight

• 8.4-meters• Triple-fold optical design• 3 billion pixel-camera• 30,000 gigabytes each night

LSSTLarge-apertureSynoptic

SurveyTelescope

Survey the sky each weekReal-time data analysis3 billion sources + transients

Beyond 30-meters

ESO’s Overwhelmingly

Large Telescope

How much do big telescopes cost?

Cost increases rapidly as the

diameter increases

Telescope Cost vs. Aperture0

20

40

60

80

100

120

140

0 5 10 15

Aperture in meters

Co

st (

mil

lio

ns

of

$$)

Homework ReviewHomework:

– www.astro.indiana.edu/novasearch

Preparing for the Exam• Take the 1st two practice tests on Oncourse• Review Key Terms, Questions for Review,

and “Test Yourself” at the back of each section we covered

• Sections: 1, 2, 3, (4), 5, 6, 10, 21, 22, 23, 24, 25, 26, 27, 30

• Also review class notes, essential facts, homeworks

• Test will ask you to APPLY what you know, not just to repeat back what you know!

The Sun! Units 49, 50, 52 News Quiz on Tuesday Homework Due EACH

THURS.EXAM THIS THURSDAY