unit 4 tools of astronomy unit focus: information about the universe comes to earth through...
TRANSCRIPT
UNIT 4Tools of Astronomy
Unit Focus:
Information about the universe comes to earth through
electromagnetic waves of different wavelengths
Exploration 1
Observing the Universe
Essential Question 1:What can different types of
electromagnetic radiation reveal about astronomical objects?
The Astronomers Challenge
• Humans have only visited 1 body other than earth in our universe – the moon (1969)– Lunar soil was gathered and returned to earth for analysis
• Space Probes have landed on 4 other bodies in the solar system– Venus (1970)– Mars (1971)– 433 Eros – asteroid (2001)
Astronomers cannot simply gather a sample of a star or galaxy and bring to a laboratory on earth to analyze
What can we gather from objects in space?
LIGHTElectromagnetic Radiation
Some things we can “see”
Some things we can’t “see”
These things are either
1. Too far away and too dim or
2. Do not emit visible light
First Thoughts: Making Claims
1. Describe and/or draw what you might think the room around you would look like:
a. If you had eyes that could detect heat instead of visible light.
b. If you had eyes that could see x-rays.
2. Describe and/or draw what you think the night sky around you would look like:
a. If you had eyes that could detect heat instead of visible light.
b. If you had eyes that could see x-rays.
Activity 1: Gathering Evidence From a Scene
Key Concepts 1. A2. B
Objectives3. A4. B
1. Read FYI: Evidence and Inference
• Direct Evidence• Indirect Evidence• Inference
Examples of Direct Evidence
• Mass of astronomical objects in binary systems
• Luminosity – total power output of an object• Flux Density – power received per unit area
per wavelength
Examples of Indirect Evidence
• Existence due to gravitational effects (black holes, dark matter, dark energy)
• Mass (black holes)• Distance – Hubble’s Law
Inference
• Explanations for an observationExample:Observation: The grass on the schools front lawn
is wetInferences:
Checking In
1. What is the difference in direct and indirect evidence?
2. Describe how astronomers use inference and electromagnetic radiation to learn about astronomical objects.
Thoughts on the drawing
• Which car caused the collision?• In which direction where the cars moving
before the collision?• Your questions here!!! Develop 2 more Q’s.• Develop a theory explaining what happened in
the drawing.• Identify at least 3 pieces
of evidence to support your theory.
Pause and Reflect
1. Which pieces of evidence could you observe directly, and which would require inference?
2. Is inference always accurate? Explain.
3. Is direct observation always accurate. Explain.
The Light-Year (ly)
• The meter is just too small to use to represent astronomical distances
• We use many units specific to astronomy – Astronomical unit (AU): average distance between the sun and the
earth 1AU = 149,597,870.7 km – Light year: the distance light travels in one year
• Express light years in meters and kilometers.• The closest star to our solar system, Proxima Centuri, is 4.5 ly. How many
kilometers away is it? How long would it take humans to get there if traveling at 57,600 km/h (This is the speed of the New Horizons space craft that was launched in 2006 and is heading toward Pluto)
– Parsec (pc): distance corresponding to the parallax of one second. (we’ll discuss this later) 1pc = 3.26 ly
Activity 2 What does Electromagnetic Radiation Tell Us?
• Key Concepts1. A2. B
Objectives3. A4. B
Describe what part or feature of the image you think you are seeing
Pause and Reflect
1. How does seeing images of different types of electromagnetic radiation from an object help you understand more about the object?
Can you guess what I am?My radio emission is imaged below
I look a little different in X-ray
Here I am in optical
Pause and Reflect
1. Would you have recognized the object from just the first image (the radio image)?
2. Which type of electromagnetic radiation shows the object as your are accustomed to seeing it?
The Crab Nebula (M1)
• The crab nebula is a supernova remnant (SNR)• A SNR is the expanding shell of gas that is
ejected into space after a massive star reaches the end of it’s life and explodes.
• The Crab nebula exploded in 1054 AD. It was observed by the Chinese and Arabs and was known to the Chinese as the “guest star”
For each image, describe what features you can see that are not apparent in the other
images.
Pause and Reflect
1. How does seeing images of different types of electromagnetic radiation from an astronomical object help you understand more about the object?
How the Crab nebula got it’s name
• Drawing of the Crab Nebula by William Parsons, the Third Earl of Rosse.
• This drawing gave rise to the name "Crab Nebula". It was created using the 36-inch reflector at Birr Castle about 1844.
Activity 3: Discovering the Multi-wavelength Universe
Over the past few decades science organizations around the world have invested great amounts of money in building major
telescopes to observe various forms of electromagnetic radiation
STEP 1
• Read FYI: Observing Different types of Electromagnetic Radiation
X-Rays and Gamma (γ) Rays
• Highest-energy forms of electromagnetic radiation
• Produced by – material that is heated
to millions of degrees– often the result of
cosmic explosions– high speed collisions – or material moving at
extremely high speeds
• Led to the discovery of black holes
• Added to our understanding of SN, white dwarfs, and pulsars
• Observations of x and γ rays of the sun allow astronomers to study the hottest regions of the sun
BLAZAR 3C 273
Chandra (X-ray) Hubble (Optical)(Gamma Ray)
X – ray Images of the SunSOHO: Solar and Heliospheric Observatory
YOHKOHhttp://solar.physics.montana.edu/sxt/
Ultraviolet Radiation (UV-Rays)
Objects that strongly emit UV rays
• Very young massive stars• Some very old stars• Bright nebulae• Young white dwarf stars• Active galaxies• Quasars
UV-Rays provide information about the Interstellar Medium:
1. chemical composition2. Density3. Temperature
UV images of the Sun
SOHO UV imageIUE – International Ultraviolet Explorer Satellite
Ultraviolet ImagesUV image of Jupiter’s Moon Io during a
volcanic eruption Visible Image of Io
UV image of M101
• A spiral galaxy located about 16 million light years from the Earth in the constellation Ursa Major (the Great Bear).
• The bright sections of the image reveals regions where new stars are forming at a rapid rate,"
Visible light
Optical telescopes• Terrestrial
– Keck (10 meter) in HA
• Space based– Hubble Space Telescope (HST)
Allow us to determine• Composition• Motion• Temperature• Physical features
Infrared (IR)
Image: Spitzer Space Telescope
• NASA's newly named Spitzer Space Telescope has captured dazzling images of a dusty, spiral galaxy; a planet-forming disc; a glowing, stellar nursery and a young, buried star, demonstrating the power of its infrared eyes to spy hidden objects.
Top left: The dusty, star-studded arms of M81, a nearby spiral galaxy similar to our own, are illuminated in unprecedented detail. The image reveals Spitzer's ability to explore regions invisible in optical light.
Top right: A massive disc of dusty debris encircles a nearby star called Fomalhaut. Such discs are remnants of planetary construction; our own planet is believed to have formed out of a similar disc.
Bottom left: Resembling a flaming creature on the run, this image exposes the hidden interior of a dark and dusty cloud in the emission nebula IC 1396. Young stars previously obscured by dust can be seen here for the first time.
Bottom right: This Spitzer image transforms a dark cloud into a silky translucent veil, revealing the stellar winds from an otherwise hidden newborn star called HH46-IR. Spitzer's remarkable capacity to peer through cosmic dust allowed it to unveil this never-before-seen star.
MicrowaveWMAP: Wilkinson Microwave Anisotropy Probe
– NASA's Wilkinson Microwave Anisotropy Probe (WMAP) has mapped the Cosmic Microwave Background (CMB) radiation (the oldest light in the universe) and produced the first fine-resolution full-sky map of the microwave sky
– WMAP definitively determined the age of the universe to be 13.73 billion years old to within 1% (0.12 billion years) -as recognized in the Guinness Book of World Records!
– determination that ordinary atoms (also called baryons) make up only 4.6% of the universe (to within 0.1%)
– dark matter (not made up of atoms) make up 23.3% (to within 1.3%)
– dark energy makes up 72.1% of the universe (to within 1.5%), causing the expansion rate of the universe to speed up. Science Magazine 2003, "Breakthrough of the Year" article
Radio Waves (RF)
Radio waves• Have very low energy • Used to gather information
about:– Supernova– Quasars/blazars (activie
galaxies)– Pulsars– The interstellar medium– The big bang
Radio
The Whirlpool Galaxy (M51)
This radio images shows that the radio emission from the galaxy’s cold hydrogen gas (blue) extends well beyond the optical light emitted by its stars (Credit: NRAO/AUI, J. Uson).
Checking In
1. How do the different forms of electromagnetic radiation differ from one another?
2. Name four objects or processes that are better observed using a type of electromagnetic radiation other than visible.
M17 – an emission nebula
STEP 3
1. Go to the link under Investigating Tools of Astronomy: Exploration 1 Activity 3 on the IA Web Site, where you will encounter images and information about numerous observations of these objects
2. Find images and descriptions for your objects.– APOD: Astronomy Picture of the Day is a great
place to search for information about most astronomical objects
STEP 4
• Create a small poster or other type of display to show your object as it appears in as many types of electromagnetic radiation as you can find on the Web.
• Write a description to accompany your display that includes– The type of object and at least 2 important characteristics
such as distance, age, or distinguishing features– Features of the object that are evident from one type of
electromagnetic radiation but not from others– Questions you have about the object
STEP 5
• Read FYI: Astronomical Objects in Different Types of Electromagnetic Radiation.
Centaurus A
• When observed using certain types of EM is the largest object in the sky
• In order to understand more about Centaurus A astronomers examine it using each type of electromagnetic radiation
• They interpret the evidence that each type of EM radiation provides as they try to determine the nature and origin.
Checking In
1. For each type of electromagnetic radiation (x-ray, UV, visible, IR, and radio), describe features of processes that are observable using that type of radiation.
2. How do observations using multiple types of radiation tell a bigger story than just one type can?