Types of AstronomyHow we use different parts of the EMS to learn

about the Universe

The different forms of EM radiation are the same basic kind of energy

They differ by wavelength and frequency High frequency/short

wavelength(gamma) Low frequency/long wavelength

(radio)

The Electromagnetic SpectrumLow frequency & Long wavelength

High frequency &Short wavelength

We use many different wavelength of EM radiation in our everyday lives Medical imaging (Xrays) Sterilization (UV) Cooking (microwave) Communications (Radio) Visual displays (visible light)

We also use various EM radiation to learn about the universe

The Electromagnetic Spectrum

Visible light from nearby celestial objects have been observed for millenia

The Sun, planets, stars, comets, meteors, supernovae

Little was known about these objects, so myths grew around them

Basic patterns of motion over time were documented

These studies formed the basis of mathematics and Science

The Early Efforts

When lenses were invented, people started using them to improve the view of celestial objects

Galileo used a crude telescope (Looking Glass) to study the sky, and used his observations to differentiate the planets from the stars

He also identified and tracked the motion of sun spots, which allowed him to understand the rotation of the sun

Analyzing their motions led him to understand the Solar System’s true arrangement

Early Telescopes

As lenses became better, stronger lenses made larger images of objects in the sky (refracting telescope)

Refraction, however, made the images fuzzy Newton used mirrors to collect the light (the first reflecting

telescope) in late 1600’s Eliminated the refraction effect and got sharper images The larger the mirror the more light is collected Dimmer objects could be seen with larger mirrors…

Limits to Lenses

Keck Observatory on Mauna Kea in Hawaii Elevation 13,796 feet above sea level (2.6

miles!) Mirror is 10 meters in diameter Too large to fit into our classroom!

Largest Optical Telescope

No loss of energy to Earth’s atmosphere Outside most of the atmosphere, so no

background light to deal with Mirror is 2.4 meters in diameter Can observe visible light, near infrared, near

UV

Hubble Space Telescope

Optical Telescopes can observe Visible light Near Infrared Near Ultraviolet

Usable Wavelengths in Astronomy

OpticalTelescopes

Collects radio waves instead of light Uses a dish-shaped collector to gather the

waves Receivers then amplify the waves and detect

signals Larger the dish, the more waves collected Radio waves may be available while light waves are blocked

Radio Telescopes

The radio telescopes below are all located at the Haystack Observatory in Westford/Groton/Tyngsboro

They are used for studying the atmosphere, for tracking satellites in Earth orbits, changes in the Earth, and astronomical tasks, too!

Haystack Observatory

Haystack Observatory

Combining Observations

Use multiple modes toGet more complete image Visible light Radio waves Infrared Ultraviolet X-rays

Radio Telescopes can observe Most radio waves Longer microwaves

Very long wavelengths (10 meters +) are blocked by the Ionosphere

Usable Wavelengths in Astronomy

OpticalTelescopes

Radio Telescopes

The atmosphere only lets through certain forms of EM radiation

Visible light (obviously) Radio waves Microwaves NOT Infrared NOT Ultraviolet NOT X-rays NOT Gamma rays

Limitations from the Atmosphere

Limitations from the Atmosphere

Chandra Xray Observatory Launched July 1999 One of NASA’s four Great Observatories Uses stacked mirrors and a very slight angle

to focus Xrays Objects not visible can be detected

Xray Telescopes

NuStar Xray Observatory Launched June, 2012 Measures higher-energy X-rays (6-79 KeV)

than Chandra or other previous X-ray telescopes

July 27, 2012 – completed post-launch assessment

August 2012 starting to observe

Xray Telescopes

Xray Telescopes can observe Xrays!

Usable Wavelengths in Astronomy

OpticalTelescopes

Radio Telescopes

XrayTelescopes

Fermi Gamma Ray Space Telescope Launched June, 2008 One of NASA’s four Great Observatories Has LAT (Large Area Telescope) and Gamma-

ray Burst Monitor

Gamma Ray Telescopes

Gamma Ray Telescopes can observe Gamma Rays!

Usable Wavelengths in Astronomy

OpticalTelescopes

Radio Telescopes

XrayTelescopes

Gamma Ray

Telescopes

Using two or more telescopes at the same time to compare signals and get finer data on direction (resolution)

A specialized computer (Correlator) calculates information from the two receivers

Can be used with optical or radio scopes

Interferometry

Using two very widely spaced telescopes at the same time to compare signals

Used to measure changes in the Earth (Geodesy)

Can be thousands of miles apart Must have very accurate timers Worldwide project being set up to get image of the supermassive black hole at our galaxy’s center

VLBIVery Long Baseline Interferometry

Project coordinated by Haystack Observatory using radio telescopes around the world to create a network of sites/radio dishes to be able to resolve the Event Horizon of the supermassive black hole at the center of our galaxy, the Milky Way.

Sagittarius A* (pronounced “A star”) is optically invisible due to clouds of dust around the galactic core

Radio telescopes hope to take the first image of this object around 2016

EHTEvent Horizon Telescope

Have used radio telescopes in: Hawaii Arizona California

Demonstrated the capability of the technology

Now adding an additional site Atacama Desert, Chile (ALMA)

EHTEvent Horizon Telescope

EHTEventual Sites

Hawaii (Mauna Kea) California (CARMA Cedar Flat,CA) Arizona (Mt. Graham, AZ) Chile (ALMA Atacama, Chile) Mexico Spain France Antartica Greenland

EHTThe Goal