page 1 lecture 6: telescopes and spacecraft claire max october 12 th, 2010 astro 18: planets and...

Lecture 6: Telescopes and SpacecraftLecture 6: Telescopes and Spacecraft

Claire MaxClaire MaxOctober 12October 12thth, 2010, 2010

Astro 18: Planets and Planetary Astro 18: Planets and Planetary SystemsSystems

UC Santa CruzUC Santa Cruz

Jupiter as seen by Cassini spacecraft

HomeworkHomework

• I fell behindI fell behind

• I will post homework shortlyI will post homework shortly

• It will be due a week from today, rather than It will be due a week from today, rather than this Thursday as I had promisedthis Thursday as I had promised

• Sorry!Sorry!

Lick Observatory Field Trip Nov 12Lick Observatory Field Trip Nov 12

• There will a field trip to Lick Observatory's Mount Hamilton There will a field trip to Lick Observatory's Mount Hamilton station on Fri Nov 12, 2010.station on Fri Nov 12, 2010.

• The trip is optional, and open only to students in ASTR 1, The trip is optional, and open only to students in ASTR 1, 18, and 70. We can only accommodate the first 40 students 18, and 70. We can only accommodate the first 40 students who sign up. who sign up.

• Sign up in person with Cathy Clausen in the Astronomy Sign up in person with Cathy Clausen in the Astronomy department office (ISB 211) and pay her $5 to reserve your department office (ISB 211) and pay her $5 to reserve your spot for the trip (no refunds if you don't show up). spot for the trip (no refunds if you don't show up).

• We will arrange transportation in UCSC vans. We will leave We will arrange transportation in UCSC vans. We will leave campus at 1:30PM and you should be back in your rooms campus at 1:30PM and you should be back in your rooms by midnight.by midnight.

• See class website for details.See class website for details.

Topics for this lectureTopics for this lecture

• Finishing up last Thursday’s lecture on light Finishing up last Thursday’s lecture on light and its interaction with matterand its interaction with matter

– Emission and absorption of light by atomsEmission and absorption of light by atoms– Concept of a spectrumConcept of a spectrum– Blackbody emission: how does shape of spectrum Blackbody emission: how does shape of spectrum

depend on temperature of the emitting body?depend on temperature of the emitting body?

• Telescopes on the ground and in spaceTelescopes on the ground and in space

Please remind me to take Please remind me to take a break at 12:45 pm!a break at 12:45 pm!

Emission of light by an atomEmission of light by an atom

Absorption of light by an atomAbsorption of light by an atom

© Nick Strobel

Continuous SpectrumContinuous Spectrum

• The spectrum of a common (incandescent) The spectrum of a common (incandescent) light bulb spans all visible wavelengths, light bulb spans all visible wavelengths, without interruption.without interruption.

Emission Line SpectrumEmission Line Spectrum

• A thin or low-density cloud of gas emits A thin or low-density cloud of gas emits light only at specific wavelengths that light only at specific wavelengths that depend on its composition and depend on its composition and temperature, producing a spectrum with temperature, producing a spectrum with bright emission lines.bright emission lines.

Absorption Line SpectrumAbsorption Line Spectrum

• A cloud of gas between us and a light bulb A cloud of gas between us and a light bulb can absorb light of specific wavelengths, can absorb light of specific wavelengths, leaving dark absorption lines in the spectrum.leaving dark absorption lines in the spectrum.

Chemical FingerprintsChemical Fingerprints

• Each type of atom has a unique spectral Each type of atom has a unique spectral fingerprint (a discrete set of spectral lines fingerprint (a discrete set of spectral lines at specific wavelengths)at specific wavelengths)

When do you see absorption lines? When do you see absorption lines? emission lines?emission lines?

© Nick Strobel

Thermal RadiationThermal Radiation

• Nearly all large or dense objects emit Nearly all large or dense objects emit thermal radiation, including stars, planets, thermal radiation, including stars, planets, you.you.

• Sometimes called “blackbody radiation”Sometimes called “blackbody radiation”

• An object’s thermal radiation spectrum An object’s thermal radiation spectrum depends on only one property: its depends on only one property: its temperature.temperature.

Properties of Thermal RadiationProperties of Thermal Radiation

1.1. Hotter objects emit more light/area at all Hotter objects emit more light/area at all frequencies.frequencies.

2.2. Hotter objects emit photons with a higher Hotter objects emit photons with a higher average energy (shorter wavelength).average energy (shorter wavelength).

Bluer color emitted light means Bluer color emitted light means hotter temperature of the matterhotter temperature of the matter

© Nick Strobel

Wien's law

λpeak =2.9 ×106

T (Kelvin) nm

Total flux emitted increases with Total flux emitted increases with temperature Ttemperature T

flux =F =σT 4 joules per sec per m2 of area

σ =Stefan−Boltzmann constant=5.67 ×10−8 joules sec−1 m−2K −4

Some things you can learn from a Some things you can learn from a spectrumspectrum

• Temperature and density of matter at the light sourceTemperature and density of matter at the light source

• Ionization stateIonization state

• Chemical composition Chemical composition – Example: ozone as sign of life on EarthExample: ozone as sign of life on Earth

• Presence of specific mineralsPresence of specific minerals– Example: Lunar Prospector spacecraft, ice on moonExample: Lunar Prospector spacecraft, ice on moon

• Structure of atmosphereStructure of atmosphere– Example: Neptune clouds, height of cloud layersExample: Neptune clouds, height of cloud layers

• Velocities of the material emitting or absorbing the Velocities of the material emitting or absorbing the light light

Topics for this lectureTopics for this lecture

• Finishing up last Thursday’s lecture on light Finishing up last Thursday’s lecture on light and its interaction with matterand its interaction with matter

• Telescopes and spacecraft: how we learn about Telescopes and spacecraft: how we learn about the planetsthe planets

– LensesLenses– Cameras and the eyeCameras and the eye– Telescope basics (optical, x-ray, radio telescopes)Telescope basics (optical, x-ray, radio telescopes)– Blurring due to atmospheric turbulence; adaptive Blurring due to atmospheric turbulence; adaptive

opticsoptics– Airborne telescopesAirborne telescopes– SpacecraftSpacecraft

✓✓

Telescopes: Main PointsTelescopes: Main Points

• Telescopes gather light and focus itTelescopes gather light and focus it– Larger telescopes gather more lightLarger telescopes gather more light– Telescopes can gather “light” at radio, infrared, visible, Telescopes can gather “light” at radio, infrared, visible,

ultraviolet, x-ray, ultraviolet, x-ray, γγ-ray wavelengths-ray wavelengths

• Telescopes can be on ground, on planes, in space Telescopes can be on ground, on planes, in space

• If Earth’s atmosphere weren’t turbulent, larger ground-If Earth’s atmosphere weren’t turbulent, larger ground-based telescopes would give higher spatial resolutionbased telescopes would give higher spatial resolution

– Adaptive optics can correct for blurring due to turbulenceAdaptive optics can correct for blurring due to turbulence

Every new telescope technology has resulted in Every new telescope technology has resulted in major new discoveries and surprisesmajor new discoveries and surprises

What are the two most important What are the two most important properties of a telescope?properties of a telescope?

1.1. Light-collecting area:Light-collecting area: Telescopes with a larger Telescopes with a larger collecting area can gather a greater amount collecting area can gather a greater amount of light in a shorter time.of light in a shorter time.

2.2. Angular resolution:Angular resolution: Telescopes that are larger Telescopes that are larger are capable of taking images with greater are capable of taking images with greater detail.detail.

Telescopes gather light and focus itTelescopes gather light and focus it

• Telescope as a “giant eye” Telescope as a “giant eye” – You can gather more light with a telescope, hence see fainter objectsYou can gather more light with a telescope, hence see fainter objects

Refracting telescope

Amount of light gathered is Amount of light gathered is proportional to proportional to areaarea of lens of lens

• Why area? Why area?

• ““Size” of telescope is usually described by Size” of telescope is usually described by diameter diameter dd of its primary lens or mirror of its primary lens or mirror

• Collecting area of lens or mirror = Collecting area of lens or mirror = ππ r r2 2 = = ππ (d/2) (d/2)2 2

versus

Light-gathering powerLight-gathering power

• Light-gathering power Light-gathering power area = area = ππ (d/2) (d/2)2 2

• Eye:Eye:– At night, pupil diameter ~ 7 mm, Area ~ 0.4 cmAt night, pupil diameter ~ 7 mm, Area ~ 0.4 cm22

• Keck Telescope:Keck Telescope:– dd = 10 meters = 1000 cm, Area = 7.85 x 10 = 10 meters = 1000 cm, Area = 7.85 x 1055 cm cm22

– Light gathering power is 1.96 million times that of the eye!Light gathering power is 1.96 million times that of the eye!

Refracting telescopes focus light Refracting telescopes focus light using “refraction”using “refraction”

• Speed of light is constant in a vacuumSpeed of light is constant in a vacuum

• But when light interacts with matter, it usually But when light interacts with matter, it usually slows down a tiny bitslows down a tiny bit

• This makes “rays” of light bend at interfacesThis makes “rays” of light bend at interfaces

Refraction animationRefraction animation

• http://www.launc.tased.edu.au/online/sciences/physics/refrac.html

http://www.launc.tased.edu.au/online/sciences/physics/refrac.html

A lens takes advantage of the A lens takes advantage of the bending of light to focus raysbending of light to focus rays

Focus – to bend all light waves coming from Focus – to bend all light waves coming from the same direction to a single pointthe same direction to a single point

Parts of the Human EyeParts of the Human Eye

• pupilpupil – allows light to – allows light to enter the eyeenter the eye

• lenslens – focuses light to – focuses light to create an imagecreate an image

• retinaretina – detects the – detects the light and generates light and generates signals which are sent signals which are sent to the brainto the brain

Camera works the same way: the Camera works the same way: the shuttershutter acts acts like the like the pupilpupil and the and the filmfilm acts like the acts like the retinaretina! !

The lens in our eyes focuses light The lens in our eyes focuses light on the retinaon the retina

Note that images are Note that images are upside down!upside down!

Our brains Our brains compensate!compensate!

Camera lens focuses light on film Camera lens focuses light on film or CCD detectoror CCD detector

Upside down

What have we learned?What have we learned?

• How does your eye form an image?How does your eye form an image?

– It uses refraction to bend parallel light rays It uses refraction to bend parallel light rays so that they form an image.so that they form an image.

– The image is in focus if the focal plane is at The image is in focus if the focal plane is at the retina.the retina.

• How do we record images?How do we record images?

– Cameras focus light like your eye and record Cameras focus light like your eye and record the image with a detector. the image with a detector.

– The detectors (CCDs) in digital cameras are The detectors (CCDs) in digital cameras are like those used on modern telescopeslike those used on modern telescopes

What are the two basic designs of What are the two basic designs of telescopes?telescopes?

• Refracting telescope:Refracting telescope: Focuses light with lensesFocuses light with lenses

• Reflecting telescope:Reflecting telescope: Focuses light with mirrorsFocuses light with mirrors

Cartoon of refracting telescopeCartoon of refracting telescope

Telescopes can use mirrors instead Telescopes can use mirrors instead of lenses to gather and focus lightof lenses to gather and focus light

• For practical reasons, For practical reasons, can’t make lenses can’t make lenses bigger than ~ 1 meterbigger than ~ 1 meter

• Can make mirrors Can make mirrors much larger than thismuch larger than this

– Largest single telescope Largest single telescope mirrors today are about mirrors today are about 8.5 m8.5 m

• Old-fashioned Old-fashioned reflecting telescope: reflecting telescope:

– Observer actually sat in Observer actually sat in “cage” and looked “cage” and looked downwarddownward

Mount Palomar (near San Diego): Mount Palomar (near San Diego): Prime focus cage and an inhabitantPrime focus cage and an inhabitant

• "NOTE: Smoking "NOTE: Smoking and drinking are and drinking are not permitted in not permitted in the prime focus the prime focus cage" (On web cage" (On web page of Anglo page of Anglo Australian Australian Telescope)Telescope)

• Until the 1970’s, Until the 1970’s, women weren’t women weren’t permitted either!permitted either!

Looking down the telescope Looking down the telescope tube from the top. Mirror is at tube from the top. Mirror is at

the bottom.the bottom.

More photos of Prime Focus Cage: More photos of Prime Focus Cage: things really things really havehave gotten better! gotten better!

Designs for Reflecting TelescopesDesigns for Reflecting Telescopes

Most of today’s reflecting Most of today’s reflecting telescopes use Cassegrain designtelescopes use Cassegrain design

• Light enters from topLight enters from top

• Bounces off primary Bounces off primary mirrormirror

• Bounces off Bounces off secondary mirrorsecondary mirror

• Goes through hole in Goes through hole in primary mirror to primary mirror to focusfocus

Examples of real telescopesExamples of real telescopes

• Backyard telescope:Backyard telescope:

– 3.8” diameter refracting lens3.8” diameter refracting lens– Costs ~ $300 at Amazon.comCosts ~ $300 at Amazon.com– Completely computerized: it will Completely computerized: it will

find the planets and galaxies for find the planets and galaxies for youyou

Largest optical telescopes in worldLargest optical telescopes in world

• Twin Keck Telescopes on top of Mauna Kea Twin Keck Telescopes on top of Mauna Kea volcano in Hawaiivolcano in Hawaii

36 hexagonal segments make up 36 hexagonal segments make up the full Keck mirrorthe full Keck mirror

Cleaning the Keck’s 36 segmentsCleaning the Keck’s 36 segments

One Keck segment (in storage)One Keck segment (in storage)

Future plans are even more Future plans are even more ambitiousambitious

Thirty Meter Telescope Keck Telescope

Future plans are even more Future plans are even more ambitiousambitious

People!

Concept of angular resolutionConcept of angular resolution

Car Lights

Angular resolution

• The ability to separate two objects.The ability to separate two objects.

• The angle between two objects decreases as your The angle between two objects decreases as your distance to them increases.distance to them increases.

• The smallest angle at which you can distinguish two The smallest angle at which you can distinguish two objects is your objects is your angular resolutionangular resolution..

How big is one "arc second" of How big is one "arc second" of angular separation?angular separation?

• A full circle (on the sky) contains 360 degrees A full circle (on the sky) contains 360 degrees or 2or 2ππ radians radians

– Each degree is 60 arc minutesEach degree is 60 arc minutes– Each arc minute is 60 arc secondsEach arc minute is 60 arc seconds

€

1 arc sec ×1 arc min

60 arc sec×

1 degree

60 arc min×

2π radians

360 degrees=

=2π

60 × 60 × 360radians = 4.8 × 10-6 radian = 4.8 μrad ≈ 5 μrad

or 1 μrad ≈ 0.2 arc sec

What does it mean for an object to What does it mean for an object to “subtend an angle “subtend an angle ” ?” ?

ΘΘ is the apparent angular size of the object is the apparent angular size of the objectΘΘ is the apparent angular size of the object is the apparent angular size of the object

Your eyeA

distant object

Angle Θ

““Small angle formula”Small angle formula”

• sin sin Θ Θ ~ ~ ΘΘ if if ΘΘ is << 1 radian is << 1 radian

• s = d sin s = d sin ΘΘ ~ d ~ d ΘΘ

• Example: how many arc sec does a dime subtend if it Example: how many arc sec does a dime subtend if it is located 2 km away?is located 2 km away?

dsθ

€

A dime is about 1 cm across, so

θ ≈s

d≈

1 cm

2 km×

1 km

1000 m×

1 m

100 cm=

1

2×10−5radians ×

1 μrad

10-6rad= 5 μrad =1 arc sec

Concept QuestionConcept Question

From Earth, planet A subtends an angle of 5 arc From Earth, planet A subtends an angle of 5 arc sec, and planet B subtends an angle of 10 arc sec, and planet B subtends an angle of 10 arc sec. If the radius of planet A equals the sec. If the radius of planet A equals the radius of planet B, thenradius of planet B, then

a) planet A is twice as big as planet B. a) planet A is twice as big as planet B.

b) planet A is twice as far as planet B. b) planet A is twice as far as planet B.

c) planet A is half as far as planet B. c) planet A is half as far as planet B.

d) planet A and planet B are the same distance. d) planet A and planet B are the same distance.

e) planet A is four times as far as planet B. e) planet A is four times as far as planet B.

What do astronomers do with What do astronomers do with telescopes?telescopes?

• Imaging:Imaging: Taking (digital) pictures of the sky Taking (digital) pictures of the sky

• Spectroscopy:Spectroscopy: Breaking light into spectra Breaking light into spectra

• Timing:Timing: Measuring how light output varies with Measuring how light output varies with timetime

ImagingImaging

• FiltersFilters are placed in are placed in front of a camera to front of a camera to allow only certain allow only certain colors through to colors through to the detectorthe detector

• Single color images Single color images are then are then superimposed to superimposed to form true color form true color images.images.

How can we observe invisible light?How can we observe invisible light?

• A standard A standard satellite dish is satellite dish is just a reflecting just a reflecting telescope for telescope for observing radio observing radio waves.waves.

How can we record images of How can we record images of nonvisible light?nonvisible light?

• Electronic detectors such as CCDs can Electronic detectors such as CCDs can record light our eyes can't see record light our eyes can't see

Infrared light, ultraviolet light, even x-raysInfrared light, ultraviolet light, even x-rays

• We can then represent the recorded light We can then represent the recorded light with some kind of color coding, to reveal with some kind of color coding, to reveal details that would otherwise be invisible to details that would otherwise be invisible to our eyesour eyes

"Crab Nebula" - supernova remnant "Crab Nebula" - supernova remnant where a star blew up 1000 yrs agowhere a star blew up 1000 yrs ago

Infra-red lightInfra-red light

Visible lightVisible light

X-raysX-rays

From above the

atmosphere

In principle, larger telescopes In principle, larger telescopes should give should give sharpersharper images images

• Concept of “diffraction limit”Concept of “diffraction limit”

– Smallest angle on sky that a telescope can resolveSmallest angle on sky that a telescope can resolve

– Numerically:Numerically:€

d =λ

D

⎛

⎝ ⎜

⎞

⎠ ⎟ radians

where λ = wavelength of light, D = telescope diameter in the same units as λ

€

diffraction limit = 2.5 ×105 wavelength of light

diam of telescope

⎛

⎝ ⎜

⎞

⎠ ⎟ arc seconds

In same units!In same units!

Image of a point source seen Image of a point source seen through a circular telescope mirrorthrough a circular telescope mirror

• At the “diffraction limit”, size of central spot ~ At the “diffraction limit”, size of central spot ~ λλ / D / D

Diffraction limit animation

Example of diffraction limitExample of diffraction limit

• Keck Telescope, visible lightKeck Telescope, visible light

• BUTBUT: Turbulence in the Earth’s atmosphere blurs : Turbulence in the Earth’s atmosphere blurs images, so even the largest telescopes can’t “see” images, so even the largest telescopes can’t “see” better than about 1 arc secondbetter than about 1 arc second

– A decrease of a factor of 1 / 0.0125 = 80 in resolution!A decrease of a factor of 1 / 0.0125 = 80 in resolution!

€

telescope diameter D = 10 meters

wavelength of light λ = 5000 Angstroms = 5 ×10-7meter

diffraction limit = 2.5 ×105( ) ×

5 ×10-7

10

⎛

⎝ ⎜

⎞

⎠ ⎟ arc seconds = 0.0125 arc second

Images of a bright star, ArcturusImages of a bright star, Arcturus

Lick Observatory, 1 m telescope

Long exposureimage

Short exposureimage

Diffraction limit of telescope

Snapshots of turbulence effects, Snapshots of turbulence effects,

Lick ObservatoryLick Observatory

These are all images of a star, taken with very short exposure times (100 milliseconds)These are all images of a star, taken with very short exposure times (100 milliseconds)

How to correct for atmospheric blurringHow to correct for atmospheric blurring

Measure details Measure details of blurring from of blurring from “guide star” “guide star” near the object near the object you want to you want to observeobserve

Calculate (on a Calculate (on a computer) the computer) the shape to apply shape to apply to deformable to deformable mirror to correct mirror to correct blurringblurring

Light from both guide Light from both guide star and astronomical star and astronomical object is reflected object is reflected from deformable from deformable mirror; distortions are mirror; distortions are removedremoved

Infra-red images of a star, from Lick Infra-red images of a star, from Lick Observatory adaptive optics systemObservatory adaptive optics system

With adaptive opticsNo adaptive optics

Deformable mirror is small mirror Deformable mirror is small mirror behind main mirror of telescopebehind main mirror of telescope

Mirror changes its shape because Mirror changes its shape because actuators push and pull on itactuators push and pull on it

• Actuators are glued to back of thin Actuators are glued to back of thin glass mirrorglass mirror

• When you apply a voltage to an When you apply a voltage to an actuator, it expands or contracts in actuator, it expands or contracts in length, pushing or pulling on the length, pushing or pulling on the mirrormirror

Neptune in infra-red light, Neptune in infra-red light, Keck Telescope adaptive opticsKeck Telescope adaptive optics

Without adaptive optics With adaptive optics

2.3

arc

sec

Movie of volcanoes on Jupiter’s moon Io, Movie of volcanoes on Jupiter’s moon Io, from Keck Telescope adaptive opticsfrom Keck Telescope adaptive optics

Volcanoes are glowing in infrared lightVolcanoes are glowing in infrared light


• The Keck Telescope in Hawaii has a diameter The Keck Telescope in Hawaii has a diameter of 10 m, compared with 5 m for the Palomar of 10 m, compared with 5 m for the Palomar Telescope in California. The light gathering Telescope in California. The light gathering power of Keck is larger by a factor ofpower of Keck is larger by a factor of

a)a) 2 b) 4 c) 15 d) 502 b) 4 c) 15 d) 50

• By what factor is Keck’s angular resolution By what factor is Keck’s angular resolution better than that of Palomar, assuming that better than that of Palomar, assuming that both are using their adaptive optics systems?both are using their adaptive optics systems?

a)a) 2 b) 4 c) 15 d) 502 b) 4 c) 15 d) 50

Reflecting telescopes work fine at Reflecting telescopes work fine at radio wavelengths tooradio wavelengths too

• The radio telescope at Green Bank, NCThe radio telescope at Green Bank, NC

Largest radio telescope fills a whole Largest radio telescope fills a whole valley in Puerto Ricovalley in Puerto Rico

Arecibo ObservatoryArecibo Observatory

SpectroscopySpectroscopy

• A spectrograph A spectrograph separates the separates the different different wavelengths of wavelengths of light before they light before they hit the detectorhit the detector

Diffractiongrating breakslight intospectrum

Detectorrecordsspectrum

Light from a starenters

Spectroscopy and the effect of Spectroscopy and the effect of spectral resolutionspectral resolution

• Graphing relative Graphing relative brightness of light brightness of light at each wavelength at each wavelength shows the details shows the details in a spectrumin a spectrum

• Higher spectral Higher spectral resolution = more resolution = more detail as a function detail as a function of wavelengthof wavelength

TimingTiming

• A light curve represents a series of brightness A light curve represents a series of brightness measurements made over a period of timemeasurements made over a period of time

Timing: Dust devils on Mars seen Timing: Dust devils on Mars seen from Spirit Roverfrom Spirit Rover

Want to buy your own telescope?Want to buy your own telescope?

• Buy binoculars first (e.g. 7x35) - you get much Buy binoculars first (e.g. 7x35) - you get much more for the same money.more for the same money.

• Ignore magnification (sales pitch!)Ignore magnification (sales pitch!)

• Notice: aperture size, optical quality, weight Notice: aperture size, optical quality, weight and portability.and portability.

• Product reviews: Astronomy, Sky & Telescope, Product reviews: Astronomy, Sky & Telescope, Mercury Magazines. Also amateur astronomy Mercury Magazines. Also amateur astronomy clubs.clubs.

Why do we need telescopes in Why do we need telescopes in space?space?

Why do we need telescopes in Why do we need telescopes in space?space?

a)a) Some wavelengths of light don’t get through Some wavelengths of light don’t get through the Earth’s atmospherethe Earth’s atmosphere

• Gamma-rays, x-rays, far ultraviolet, long infrared Gamma-rays, x-rays, far ultraviolet, long infrared wavelengthswavelengths

b)b) Going to space is a way to overcome blurring Going to space is a way to overcome blurring due to turbulence in Earth’s atmospheredue to turbulence in Earth’s atmosphere

c)c) Planetary exploration: spacecraft can actually Planetary exploration: spacecraft can actually go to the planets, get close-up informationgo to the planets, get close-up information

Depth of light penetration into Depth of light penetration into atmosphere at different wavelengthsatmosphere at different wavelengths

X-ray mirrors also concentrate light X-ray mirrors also concentrate light and bring it to a focusand bring it to a focus

• X-ray mirrors

Chandra spacecraft: x-ray telescopeChandra spacecraft: x-ray telescope

Types of space missionsTypes of space missions

• Earth orbitersEarth orbiters– Hubble and Chandra space telescopesHubble and Chandra space telescopes

• Planetary fly-bysPlanetary fly-bys– Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune so farMercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune so far

– New Horizons flyby of Pluto arrives July 14 2015 New Horizons flyby of Pluto arrives July 14 2015

• Planetary orbitersPlanetary orbiters– Venus, Mars, Jupiter, Saturn so far. Venus, Mars, Jupiter, Saturn so far.

– Soon: Mercury Messenger (March 2011)Soon: Mercury Messenger (March 2011)

• Probes and landersProbes and landers– Mars rovers: Spirit and OpportunityMars rovers: Spirit and Opportunity

– Mars landers: e.g. PhoenixMars landers: e.g. Phoenix

– Probes sent from orbiters of Venus, Mars, JupiterProbes sent from orbiters of Venus, Mars, Jupiter

– Titan lander (Huygens probe from Cassini spacecraft)Titan lander (Huygens probe from Cassini spacecraft)

Space missions carry telescopes, Space missions carry telescopes, other instruments as wellother instruments as well

• Typically planetary fly-bys and orbiters carry Typically planetary fly-bys and orbiters carry small telescopessmall telescopes

– If you are close, you don’t need super-good angular If you are close, you don’t need super-good angular resolutionresolution

• Other instruments:Other instruments:

– Particle analyzers, radio antennae, spectrographs, Particle analyzers, radio antennae, spectrographs, laser altimeters, dust detectors, .....laser altimeters, dust detectors, .....

– Mars rovers: probes to get rock samples and Mars rovers: probes to get rock samples and analyze themanalyze them

Hubble Space Telescope: clearer vision Hubble Space Telescope: clearer vision above atmospheric turbulenceabove atmospheric turbulence

Hubble can see UV light that doesn’t penetrate through atmosphere

Example of robotic planet exploration: Example of robotic planet exploration: Galileo mission to JupiterGalileo mission to Jupiter

(Artist's conception)(Artist's conception)

Spirit Rover on MarsSpirit Rover on Mars


• You are trying to decide whether to observe a new You are trying to decide whether to observe a new comet from a 10m telescope on the ground (without comet from a 10m telescope on the ground (without adaptive optics), or from the Hubble Space Telescope adaptive optics), or from the Hubble Space Telescope (diameter 2.4m).(diameter 2.4m).

• Which of the following would be better from the Which of the following would be better from the ground, and which from spaceground, and which from space

a)a) Ability to make images in ultraviolet lightAbility to make images in ultraviolet light

b)b) Spatial resolution of images in infrared lightSpatial resolution of images in infrared light

c)c) Ability to record images of a Ability to record images of a veryvery faint (distant) comet faint (distant) comet

Telescopes: The Main PointsTelescopes: The Main Points

• Telescopes gather light and focus itTelescopes gather light and focus it

• Telescopes can be on ground, on planes, in space Telescopes can be on ground, on planes, in space

• If Earth’s atmosphere weren’t turbulent, larger If Earth’s atmosphere weren’t turbulent, larger telescopes would give higher spatial resolutiontelescopes would give higher spatial resolution

– Adaptive optics can correct for blurring due to turbulenceAdaptive optics can correct for blurring due to turbulence

• Every new telescope technology has resulted in major Every new telescope technology has resulted in major new discoveries and surprisesnew discoveries and surprises

page 1 lecture 6: telescopes and spacecraft claire max october 12 th, 2010 astro 18: planets and...

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light of specific wavelengths

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