GEARS Workshop WednesdayImaging DayAnd Fusion

2012

Warm Up• Online – and paper evaluation – • Please use what is in your own brain only.

Overview Slides• Introduction to imaging• Ds9 introduction and spectral line

identification• Atmospheric transparency• Fusion and formation of the elements

Images• Learn digital image basics and false color meaning• Learn a new software • Duplicate a press release• Identify some elements in some supernova• Make your color supernova image• Compare your color image to the press release!• Get data from other observations

Digital Image Basics• More pixels good? • What is false color?• Why do we need false color?

Ds9• First open image and play with software (use

instructions online)• File: Open (you can’t open the files by double clicking

on them)– Navigate to “My Computer”– Navigate to “E:” (or the name of your thumb drive)– Navigate to GEARS directory– Navigate to Data– Look for file

ds9• Make a press release• Get an X-ray image of galaxy cluster in sky• Get the same part of sky in visible light• Match up the coordinates so the 2 images are

lined up• Try to match color scheme of press release

• http://chandra.harvard.edu/resources/handouts/lithos/hydraA_low.pdf

Hydra• Composite including radio • http://chandra.harvard.edu/photo/2009/hydr

a/

Right Before Lunch Sharing• http://chandra.harvard.edu/edu/formal/index

.html• Other resources…

Atmospheric Transparency• Lab – there is a student worksheet for this –

but no instructions• What materials transmit which types of

radiation (aka light – the tool of the astronomer)?

• Which materials block or shield radiation?

Lab Instructions• Find out what materials allow light to pass

through and be detected• Note whether the material was a shield or a

transmitter• See the power point for stations

Discuss the Lecture Tutorial• You did it last night, right? • Pages 49-51. • Go through 1 – 3 and 4c. • Reflect back to Tuesday – NASA Great

Observatories. Which had to be in space?

Why do you need telescopes in space?

• Brainstorm –• Metacognate – what do you think your

students might think.

Is it distance?

Common misconception. distance

Example assessment• Which of the two proposals would you choose to

fund?• Project Rho: A UV wavelength telescope, placed high

atop Mauna Kea at 14,000 ft above sea level, which will be used to look at distant galaxies?

• Project Sigma: A visible wavelength telescope, place on a satellite in orbit around Earth, which will used to observe a pair of binary stars located in the constellation Ursa Major?

• Can you do the UV project effectively from ground? Why or why not?

• Is it cost effective to do visible astronomy from space? Especially for simple stellar observations.

• Why send satellites in space to do visible observations?

Chandra • Chandra telescope collected Xray light• Not just how many photons arrived at satellite• But also time of arrival (good for short lived

phenomena like gamma ray bursts)• Also the energy of the photons – so can

identify the atomic electronic transition (think fingerprint from Monday)

Make your own 3 color diagram

• That means something…

Concepts• Astronomers make 3 color diagrams to represent

3 pieces of information visually. For example, 3 different emission line features.

• Spectral lines are like fingerprints, they are unique to the element or molecule that emitted (or absorbed) them due to the unique electronic energy levels in each.

• Type Ia and Type II supernova remnants may appear similar in size and shape but have different spectral signatures due to the different progenitors.

Supernova instructions• Open ds9• Open chandraed virtual observatory• Open image assigned. (115 or 126)• Make a spectrum• Identify 3-5 strong lines using database • summarize the two types

Do if time/interest• Make 3 energy cuts – or filters• Make 3 color image • Compare your result to the press release (look

for 2007 or later) energy cuts and color choices

Spectral Line ID in X-ray• http://www.atomdb.org• Web Guide• Check your units carefully

Complexities in Real Data• Roman numeral notation = ionization notation we

teach minus 1• Which element/transition is it? – How do we know if it is Sulfur versus Fe XX?– Verification with other lines is best– Most abundant in universe is indicated in chart

• Do I use the EXACT wavelength?– What is the material is moving towards or away from us?

May be Doppler Shifted

Supernova Remnants• G292.0+1.8 & Tycho (left) – Saw from spectra

that they weren’t the same type of object

The astronomy of Supernova…Two types of starting pointsLead to explosionsLeading to remnants like you just sawBut with different compositions

Type 1a mass transferType 2 (II) high mass

Low Mass vs High Mass Progenitor

•

High Mass

Tycho – Type Ia• http://hubblesite.org/newscenter/archive/

releases/2004/34/

Core Collapse (on right)

Spectral Line ID in X-ray• http://www.atomdb.org• Need to remember/know that Fe XX means

Fe+19 (19 times ionized iron)• HI = neutral hydrogen• HII = singly ionized hydrogen

Different spectra• Due to different progenitors – original stars

that exploded were composed of different things

• In one – a white dwarf made of He or C with material – primarily H – explodes

• In other – Fe and others smooshing into one another

Differences

• Type Ia: – Strong Si, S, Ar, Ca, Fe–Weak O, Ne, Mg

• Type II – reverse• Complications – the lines are not all alone – but there is a continuous

emission signature at all colors! (not blackbody though)• Best way to deal with spectra is to account for the continuum using a model

– see http://chandra.harvard.edu/edu/formal/ X-ray Spectroscopy and Supernova Remnants lab online.

Research your students can do!

• http://cmarchesin.blogspot.com/2009/12/g292018-keplers-supernova-remnant.html

• Study with Chandra data – comparing shapes of remnants – Type Ia – symmetric, Type II not

• This study was on only 17 objects – your students could do more and see if trend holds

• How define symmetric?? Could be a discussion all by itself.

How to get data• By Obs ID from list• You saw obsid’s in press release images• If Obs ID is not in list – you can still get the image – go to middle area where there

is text and use search feature there.

Suppose the universe contained only low-mass stars. Would elements heavier than carbon exist?

a. Yes, all stars create heavier elements than carbon when they become a supernova.

b. Yes, but there would be far fewer heavier elements because high-mass stars form elements like iron far more prolifically than low-mass stars.

c. No, the core temperatures of low-mass stars are too low to fuse other nuclei to carbon, so it would be the heaviest element.

d. No, heavy elements created at the cores of low-mass stars would be locked away for billions of years.

e. No, fission reactions would break down all elements heavier than carbon.

Elements in us• Most of the heavy elements (everything except

hydrogen and helium) in the Earth were produceda) by stars that burned out before the Solar System

formed.b) in chemical reactions in the primitive oceans and

atmosphere.c) in nuclear reactions in the Sun.d) in the hot, dense, early universe.

Where do the elements come from?

• Big Bang = energy forms neutrons, protons, electrons and overwhelmingly hot and dense conditions are such that Hydrogen (which is only a proton anyway…), Deuterium, and Helium and Lithium nuclei form

• http://map.gsfc.nasa.gov/universe/bb_tests_ele.html

All other elements• Formed in main sequence stars• Or formed in explosions of stars called

supernova (supernovae is plural) • The supernova are needed to spread the

fusion products into space – otherwise trapped in stellar coreshttp://imagine.gsfc.nasa.gov/docs/teachers/elements/

Fusion – summary of chain of reactions – not the exact reaction

• Main sequence: 4 (1H) --> 4He + 2 e+ + 2 neutrinos + energy

• Hydrogen in core expended – fusion ends, collapse begins, heating and …

• 3 (4He) --> 12C + energy (Sun ends here…)• Helium in core expended – fusion ends,

collapse begins, heating and …• 12C + 12C --> 24Mg OR 12C + 4H --> 16O

E=mc2

• Where does the energy come from ?• Mass of four 1H > Mass of one 4He

Low Mass vs High Mass•

Really massive stars

Why is Fe so special?• Examining the binding curve in detail.

MIT OpenCourseware

Formation of the elements• Most of the heavy elements (everything except

hydrogen and helium) in the Earth were produceda) by stars that burned out before the Solar System

formed.b) in chemical reactions in the primitive oceans and

atmosphere.c) in nuclear reactions in the Sun.d) in the hot, dense, early universe.

Suppose the universe contained only low-mass stars. Would elements heavier than carbon exist?

a. Yes, all stars create heavier elements than carbon when they become a supernova.

b. Yes, but there would be far fewer heavier elements because high-mass stars form elements like iron far more prolifically than low-mass stars.

c. No, the core temperatures of low-mass stars are too low to fuse other nuclei to carbon, so it would be the heaviest element.

d. No, heavy elements created at the cores of low-mass stars would be locked away for billions of years.

e. No, fission reactions would break down all elements heavier than carbon.

Where does Uranium come from?

• How does the iron get out of the core?• Explosions• Are all explosions created equally?• Explosions leave a mess• Mess (nebula) can be swept up into new stars

Nebula

Tying back to supernova remnants

• We saw S, Si, Mg, O, Fe in the supernova remnants• Tycho – Type Ia (115)• The oxygen-rich supernova G292.0+1.8 contains a pulsar.

Type II • Type Ia and Type II remnants because the progenitors are different.

Type Ia remnants - from white dwarfs - usually show relatively strong Si, S, Ar, Ca, and Fe, and weak O, Ne, and Mg lines; Type II

remnants - from massive stars - generally have the reverse pattern. • (http://chandra.harvard.edu/xray_sources/pulsar_java.html )

• http://chandra.harvard.edu/edu/formal/stellar_ev/story/index.html

Core Collapse• http://en.wikipedia.org/wiki/

Type_II_supernova

• http://hyperphysics.phy-astr.gsu.edu/hbase/astro/snovcn.html

Classification – happened prior to knowing exact source!

• They are classified as Type I if they have no hydrogen lines in their spectra. The subclass type Ia refers to those which have a strong silicon line at 615 nm. They are classified as Ib if they have strong helium lines, and Ic if they do not. Type II supernovae have strong hydrogen lines. These spectral features are illustrated below for specific supernovae.

• http://chandra.harvard.edu/edu/formal/snr/bg.html • The elements and their relative abundances are different for Type Ia and

Type II remnants because the progenitors are different. Type Ia remnants - from white dwarfs - usually show relatively strong Si, S, Ar, Ca, and Fe, and weak O, Ne, and Mg lines; Type II remnants - from massive stars - generally have the reverse pattern. In addition to the composition of the ejecta, spectroscopy can show how much of the stellar material was convectively mixed during the supernova event by calculating the density and temperature of the ionizing gas that generates the spectral lines. However, spectroscopy of supernova remnants is not clear cut and drawing conclusions is complicated; it is sometimes difficult to determine if a remnant is Type II or Type Ia. The Chandra and XMM-Newton missions have inaugurated the era of true spatially resolved X-ray spectroscopy.

Spectrum on top of Brehmsstrahlung

Chandrasekhar limit• The maximum mass that can be supported by

electron degeneracy pressure against gravity• Chandrasekhar won Nobel Prize in 1983 with

William Fowler• http://nobelprize.org/nobel_prizes/physics/

laureates/1983/chandrasekhar-autobio.html • http://hyperphysics.phy-astr.gsu.edu/hbase/

astro/whdwar.html