Telescopes

Focus Question:

How do astronomers study light?

Telescopes

Tools for collecting and analyzing

electromagnetic radiation (light) in ways

beyond what we can do with our eyes alone

Properties of Telescopes

Aperture: how well the telescope can collect the light.

Larger aperture = more light collected (brighter image)

Resolution: The ability to distinguish small details of objects

http://www.ifa.hawaii.edu/users/lin/ast110-6/applets/angular_resol_car_lights.htm

Magnification: how much it can magnify the image.

Depends on combination of lenses/mirrors

Not as important

Optical Telescopes

Studying Visible light

Refracting Telescope

Perfected by Galileo

Uses lenses to gather and bend visible light

Can be a combination of convex (curved outward) or concave (curved inward) lenses

A primary lens collects light and sends it to a smaller secondary lens at the back of the telescope tube.

Not used much today

Primary Lens Secondary Lens

Refracting Telescope:

Yerkes Observatory

A 40 inch refracting telescope is located inside the Yerkes Observatory at University of Chicago.

It was created in 1897 and remains the largest refracting

telescope ever used.

Reflecting telescopes

First developed by Isaac Newton

Focus light by “bouncing” it off of mirrors

A Better Type of Reflector

A Cassegrain design uses a second mirror to reflect the

light back through a hole in the primary mirror

Invented in 1672, this design is the most common in

research telescopes today.

The detector(s) can be placed behind the mirror in a

convenient location for making adjustments

There are currently thirteen working telescopes near

the summit of Mauna Kea:

nine for optical and infrared astronomy

three for submillimeter wavelength (microwave) astronomy

one for radio astronomy

Mauna Kea Observatories

The Keck Observatory: A Ground-Based Optical Telescope

Mauna Kea, Hawaii

Twin telescopes with 10m wide mirrors that work together

World’s largest optical telescope until 2009 –

now the biggest single reflector is the Gran Telescopio Canarias (GTC) in Spain

Keck Headquarters

Astronomers don’t actually work at the telescopes on the

summit

They sit in the “remote operations room” in the town of

Waimea, about 2 hours away and the data is sent to a

computer

Model of Keck I

Primary Mirror

My new buddy David, who

works at both Keck

headquarters in Waimea

and at the telescopes on

Mauna Kea

The grass area

behind us

represents one

of the mirror

segments

Problems with Ground-based telescopes

Earth’s atmosphere reflects or absorbs certain

wavelengths

our atmosphere and magnetic field serves as a shield for x-

rays, gamma rays and most UV light

Earth’s atmosphere blurs images the bending of light by the atmosphere depends on the

temperature of the “air”

“twinkling” (shimmering) effect

“Light pollution” from artificial light sources make it

hard to see very faint objects in space

Getting Better Images

Telescopes are built on mountaintops so

that they are above much of the

atmosphere

Telescopes are built in remote areas

where there isn’t much artificial light

Modern ground-based telescopes use

two newtechnologies:

Interferometry

Adaptive Optics

Interferometry

Technique of using an array of telescopes to collect multiple beams of light at one time High resolution (detail)

Used to observe very distant or faint objects

Computer-controlled mirror supports adjust the mirror surface

many times per second to compensate for distortions by

atmospheric turbulence and increase resolution power

Adaptive Optics

Other Types of Telescopes

Beyond visible light

Beyond Visible Light…

Many modern day telescopes do not use visible light to

collect images

They collect other wavelengths of light from the

Electromagnetic Spectrum: radio waves, x-rays, infrared, etc

Ground-Based Radio Telescopes

A large dish or network of dishes focus the energy of

radio waves on to a small receiver

Largest telescopes ever constructed

Examples:

ALMA - Atacama Large Millimeter Array

Atacama desert in Chile

66 networked radio telescopes

VLA-Very Large Array

New Mexico

27 networked radio telescopes

Arecibo Observatory

Puerto Rico

Largest ever built-- 1000 ft across, 167 ft deep, covers 20 acres of land

Space-Based Telescopes

Space-Based Telescopes

Advantages:

No distortion by Earth’s atmosphere

Able to study all wavelengths of light

Disadvantages:

Expensive to launch and maintain

Difficult to repair

Short life span

Hubble Space Telescope

Launched in 1990, orbits

380 miles above Earth

Named for American Astronomer

Edwin Hubble (1889-1953) who

discovered the expansion of the

universe

Reflecting telescope - Collects

visible light, infrared, and ultraviolet

Primary mirror is 8 feet across

Chandra X-ray Telescope

NASA launched it in 1999

Orbits Earth 200 times higher

than Hubble

Resolving power: equal to reading

a road sign from 12 miles away

Contains special grazing-incidence

mirrors (because x-rays can pass

through normal mirrors)

Looks at quasars, binary stars, and

black holes

Spiral galaxy M106

Other Space Telescopes

Spitzer – infrared light

Fermi- Gamma Ray

Telescopes of the Future…

James Webb Telescope

A large infrared telescope

Will be launched in 2018

6.5 meter mirror

Longer wavelength

coverage and better

sensitivity than the

Hubble

Will observe galaxy &

star formation and

potential for life on

other planets

James Webb video clip

Building the JWST

Thirty Meter Telescope (TMT)

Proposed ground-based telescope with a 30-meter

primary mirror, the largest ever built

Planned for construction on Mauna Kea in 2015 but

delayed and surrounded in controversy after protesters

blocked the site

Incredible resolution would allow astronomers to study

very faint and distant objects and learn about:

Star formation

Exoplanets

Supermassive black holes

Evolution of the universe

http://www.cnn.com/2015/08/27/us/tmt-hawaii-telescope-

controversy/index.html

“A 30-meter telescope, operating in

wavelengths ranging from the ultraviolet to

the mid-infrared, is an essential tool to

address questions in astronomy ranging

from understanding star and planet

formation to unraveling the history of

galaxies and the development of large-scale

structure in the universe.” -- TMT

website

Potential Scientific Advancement

Mauna Kea is home to many archaeological burial sites

Shrines and temples are located near the summit

Modern Native Hawaiians continue to regard Mauna Kea with

reverence and many cultural and religious practices are still

performed there.

Cultural/religious beliefs

Community support: malama means “take care of” or “protect”

Land Rights: The upside-down Hawaiian Flag

symbolizes the belief that Hawaii was illegally

annexed by the US in 1959

$1.4 Billion construction project

Estimated 300 temporary construction jobs

120 permanent jobs once the facility opens

Hawaii’s economy has struggled since the 2008

crash

Greater financial impact

Possible damage to the habitat of the Wekiu bug, an indigenous

insect that was just recently removed from the endangered

species list

The Silversword plant species became an endangered species

due to cattle, sheep, and goats lower on the mountain

Potential for contamination of the Mauna Kea aquifer, which

supplies water to the east side of Hawaii Island

Environmental Impact

Should the TMT be built on Mauna Kea?

What do You think?

The Latest News…

As of October 30th, 2016 the TMT Board of Governors

has identified a site in the Canary Islands of Spain as the

primary alternative to Hawaii.

In January 2017, a state circuit court judge ordered a new

hearing allowing residents to contest the issuance of a

building permit on public lands

"Mauna Kea continues to be the preferred choice for the

location of the Thirty Meter Telescope, and the Board will

continue intensive efforts to gain approval for TMT in

Hawaii.”

http://www.hawaiinewsnow.com/story/31193881/thirty-

meter-telescope-officials-considering-sites-outside-of-

hawaii