Nov 22nd 2008Institute of Physics, Liverpool FRONTIERS OF ASTROPHYSICS - giant telescopes, space missions and invisible wavelengths Michael Rowan-Robinson

Nov 22nd 2008 Institute of Physics, Liverpool

FRONTIERS OF ASTROPHYSICS- giant telescopes, space missions

and invisible wavelengths

Michael Rowan-RobinsonImperial College London


some frontier topics in astrophysics

• Black holesBlack holes

• The dusty universeThe dusty universe- dramatic starbursts in colliding galaxies- dramatic starbursts in colliding galaxies

• ExoplanetsExoplanets- the search for extraterrestial earths- the search for extraterrestial earths

• CosmologyCosmology- measuring the size and age of universe with 5% - measuring the size and age of universe with 5%

precisionprecision- a universe of dark matter, dark energy- a universe of dark matter, dark energy


Atmospheric transmission

first detection of electromagnetic radiation outside the optical band:

Herschel (1800) detectedinfrared radiation from the sun


X-ray astronomy

The first X-ray satellite, Uhuru (1970) detected X-rays from compact sources in binary systems (white dwarfs, neutron stars, black holes), from quasars (massive black holes) and from very hot gas in clusters of galaxies (100 million degrees)


HOW TO OBSERVE BLACK HOLES?

• Black holes give off no light from within the event horizon

• Must observe effects on environment near horizon, in particular:– VELOCITIES (matter speeds up near hole) – ACCRETION (matter being sucked into hole

and heated to X-ray temperatures)– REDSHIFT (time slows down near hole)

* Effect of Einstein’s General relativity *


Cygnus X-1, a 10 solar mass black hole in our Galaxy


X-ray spectra of black holes in Active Galactic

nuclei• Hypothesis: The

nucleus of an Active Galaxy contains a black hole being fed by an accretion disk. X-rays illuminate the disk inducing emission from iron.

• Prediction: shape of line distorted by huge velocities and gravitational shifts

Observer

X-rays


WE SEE THESE EFFECTS!• X-ray iron spectrum

from the ASCA satellite• Clear broadening and

redshift• Requires black hole

Tanaka et al. (1995)

ASCA

Line profile depends on:• Inclination• Inner radius• Outer radius• X-ray illumination pattern




AND THEY ARE COMMONNandra et al. (2007)

New spectra from XMM-Newton


the dusty universe IRAS 1983 - SPITZER, 2003


IRAS - star forming regions

constellation OrionLMC, the Large Magellanic Cloud


IRAS discovered ultraluminous infrared galaxies, forming stars 100-1000 times faster than our Galaxy, probably caused by mergers between two galaxies

this is an image of Arp 220

Uultraluminous infrared galaxies


Sombrero galaxy- end product of a galaxy merger


IC1396, the Elephant’s Trunk- a dark globule inside an emission nebula

- a pair of newly formed stars have created a cavity

- the animation shows how the appearance changes from the optical, where dust absorbs light to the infrared where the dust radiates


QuickTime™ and aMPEG-4 Video decompressor

are needed to see this picture.


IRAS - dust debris disks

IRAS also discovered dust debris disks around stars, confirmed by imaging with the Hubble Space Telescope, evidence for planetary systems in formation. Today over 200 exoplanets are known.


last week: HST image of exoplanet in Fomalhaut debris disk


The Exo-Planet Discovery Era

• <1995 Solar System planets• 1995 first extra-solar planet ( 51 Peg )

- Hot Jupiters! • 2008 ~300 exo-planets known• 2005-10 first Hot and Cool exo-Earths• 2010-15 Habitable Earths -- common or

rare?• 2020-30 Extra-solar Life? Are we

alone?


Exoplanet Discovery Methods• Doppler Star Wobbles: ~230

• Transits: 39

• Microlensing: 7


1995 First Doppler Wobble Planet: 51 Peg

P = 4.2 days (!) a = 0.05 AU T ~2000K m sin(i) = 0.5 mJ New class of planet:“Hot Jupiters” (how did these form ?)

Discovered by accident: Mayor & Queloz (1995)

Quickly confirmed: Marcy & Butler (1995)



WASP’s first 2 new Hot Jupiters

UK WASP Consortium: Belfast, St.Andrews, Keele, Open, Leicester, Cambridge, IAC, SAAO


Planetary, Brown-dwarf and substellar M-R relation

0.01

0.1

1

10

100

0.00001 0.0001 0.001 0.01 0.1 1 10 100 1000 10000

Log [ M/ M_Jup ]

Log [ R / R_Jup ]

RV discoveries

WASP

HAT

TrES

XO

OGLE

Baraffe2003, 5 Gyr

Baraffe1998, 5 Gyr

Fortney2007 1Gyr core00 a0.02

Fortney2007 4.5Gyr core10 a0.045

Fortney2007 Pure Ice

Fortney2007 Pure Rock

Solar-system planets

Fortney2007 Pure Iron

Gas Giant

Planets

Low-Mass Stars

Rock/Ice Planets

brown dwarfs, gas giants and rocky

planets


How to find Earths ? • Hot Earths: Transits from Space

– 2007-10 … CoRoT -- Launched 27 Dec 2006.

– 2009-15 … Kepler

– 2017 … PLATO

• Habitable Earths: Hard to Find

– Habitable Zone: T~300K liquid water on rocky planet surface

• Cool Earths: Gravitational Lensing

– 2004-14 … OGLE, PLANET/RoboNet, microFUN, MOA


CoRoT (CNES)

Launch 27 Dec 2006

CoRoT-Exo-1b:

P = 1.5 d

m sin(i) = 1.3 mJ

First CoRoT planet: 3 May

2007

€

σ ~ 10−3 t /min( )1/ 2

6 months/fiel

d


Space Transit Planet Catch

hothabitableJupiters

Earths

Pla

net

Siz

e (

r E)

Planet Temperature (K)

Too large?

Too small?

Too hot?

A few Earth-like Planets may be found.


OB-03-235 / MB-03-053 first microlens planet

OGLEalert€

m ~ 1.3 mJ

a ~ 3 AU

Bond et al. (2004)

2003

MOA OGLE


OB-05-390

€

m ~ 6 m⊕

a ~ 2.9 AU

Aug 2005

PLANET/RoboNet

OGLE MOA

OB-05-390

smallest cool planet


ESA: Darwin ~ 2020-30? infrared space interferometerdestructive interference cancels out the starlight

snapshot ~500 nearby systems study ~ 50 in detail


Life’s Signature: disequilibrium atmosphere

(e.g. oxygen-rich)

simulated Darwin spectrum

Which planet is

alive?


The distances of the galaxies

In 1924 Edwin Hubble used In 1924 Edwin Hubble used Cepheid variable stars to estimate Cepheid variable stars to estimate the distance of the Andromeda the distance of the Andromeda Nebula. It clearly lay far outside Nebula. It clearly lay far outside the Milky Way Systemthe Milky Way System.

This opened up the idea of a This opened up the idea of a universe of galaxies.universe of galaxies.


The expansion of the universe

Five years later he announced, based on distances to Five years later he announced, based on distances to 18 galaxies, that the more distant a galaxy, the faster it 18 galaxies, that the more distant a galaxy, the faster it is moving away from usis moving away from us

velocity/distance = constant, Hvelocity/distance = constant, Ho o (the Hubble (the Hubble law)law)

This is just what would be expected in an expanding This is just what would be expected in an expanding universe.universe.

The Russian mathematician Alexander Friedmann The Russian mathematician Alexander Friedmann had shown that expanding universe models are what had shown that expanding universe models are what would be expected according to Einstein’s General would be expected according to Einstein’s General Theory of Relativity, if the universe is homogeneous Theory of Relativity, if the universe is homogeneous (everyone sees the same picture) and isotropic (the (everyone sees the same picture) and isotropic (the same in every direction).same in every direction).


The Hubble Space Telescope

Key ProgramFollowing the first Following the first HSTHSTservicing mission, servicing mission, whichwhichfixed the telescopefixed the telescopeaberration, a largeaberration, a largeamount of HST amount of HST observing time was observing time was dedicated to dedicated to measuringmeasuringCepheids in distant Cepheids in distant galaxies, to try to galaxies, to try to measure the Hubblemeasure the Hubbleconstant accurately.constant accurately.


The HST Key program final result

log V

HHoo = 72 km/s/Mpc = 72 km/s/Mpc

uncertainty 10%uncertainty 10%

(Freedman et al 2001)(Freedman et al 2001)


Implications of the Hubble constant

HHoo is (velocity/distance) so has the dimensions of (1/time). is (velocity/distance) so has the dimensions of (1/time).

1/H1/Hoo is the expansion age of the universe (how old the is the expansion age of the universe (how old the Universe would be if no forces acting) = 13.6 billion yrsUniverse would be if no forces acting) = 13.6 billion yrs

For simplest model universe with only gravity acting, age ofFor simplest model universe with only gravity acting, age ofuniverse would be 9.1 billion years (gravity slows expansion)universe would be 9.1 billion years (gravity slows expansion)


The age of the universe

We can use the colours andWe can use the colours andbrightnesses of the stars inbrightnesses of the stars inglobular clusters to estimateglobular clusters to estimatethe age of our Galaxythe age of our Galaxy ~ 12 billion years~ 12 billion years

Long-lived radioactive isotopesLong-lived radioactive isotopesgive a similar answergive a similar answer

Allowing time for our Galaxy toAllowing time for our Galaxy toform, the age of the universe isform, the age of the universe is ~ 13 billion years~ 13 billion years


The age of the universe problem

• This is a problem for the simplest models, where gravity slows down the expansion

• To get consistency between the HST Key Program value of Ho and the observed age of the universe, we need to reverse the deceleration of the universe

• Something is pushing the galaxies apart


The discovery of the Cosmic Microwave Background, 1965

The discovery of the Cosmic Microwave Background (CMB) by

Penzias and Wilson in 1965, and the confirmation of its blackbody

spectrum by COBE in 1991, showed that we live in a hot Big

Bang universe, dominated by radiation in its early stages.


How much matter is there in the universe ?

The light elements D, He, LiThe light elements D, He, Li are generated from nuclearare generated from nuclear reactions about 1 minutereactions about 1 minute after the Big Bang. Theafter the Big Bang. The abundances turn out to abundances turn out to depend sensitively on thedepend sensitively on the density of ordinary matterdensity of ordinary matter in the universe.in the universe.

density ~ 4.10density ~ 4.10-28 -28 kg/cu m kg/cu m bb ~ 0.04 ~ 0.04


Evidence for Dark Matterthe speed at which starsthe speed at which starsorbit round a galaxy pointsorbit round a galaxy pointsto the existence of a haloto the existence of a haloof dark matter. of dark matter. sensitive surveys showsensitive surveys showthat this can not be due to that this can not be due to stars, or gas.stars, or gas.


Evidence for Dark Matter 2

images of clustersimages of clustersof galaxies withof galaxies withHST show arcsHST show arcsdue to gravitationaldue to gravitationallensing. These canlensing. These canbe used to weighbe used to weighthe cluster. Again,the cluster. Again,the cluster isthe cluster isdominated by darkdominated by darkmatter.matter.

Abell 2218


Large scale structureThe 3-dimensionalThe 3-dimensional distribution ofdistribution of galaxies showsgalaxies shows structure on structure on different scales.different scales.

This can be usedThis can be used to estimate theto estimate the average density average density of the universe.of the universe.In dimenionlessIn dimenionless units:units:

~ 0.27 ~ 0.27


Need for Dark Matter

So there is far more matter (So there is far more matter ( ~ 0.27 ) ~ 0.27 ) out there than can be accounted for by out there than can be accounted for by the stuff we are made of (the stuff we are made of (bb ~ 0.04). ~ 0.04).

85% of the matter in the universe is 85% of the matter in the universe is ‘dark’ matter (the neutralino ?)‘dark’ matter (the neutralino ?)

Particle Physicists hope to detect this at Particle Physicists hope to detect this at the Large Hadron Colliderthe Large Hadron Collider


Supernovae as Supernovae as Standard candlesStandard candles

Type Ia supernovae (explosionType Ia supernovae (explosionof a white dwarf star in a binary of a white dwarf star in a binary system) seem to be remarkably system) seem to be remarkably uniform in their light curves. uniform in their light curves. They behave likeThey behave like‘‘standard candles’ and can bestandard candles’ and can beused to estimate distances.used to estimate distances.


Distant Type Ia supernovae

Recently a breakthrough in search techniques,Recently a breakthrough in search techniques, using 4-m telescopes to locate new using 4-m telescopes to locate new supernovae, and supernovae, and 8-m telescopes plus the Hubble Space 8-m telescopes plus the Hubble Space Telescope to Telescope to follow them up, has resulted in the detectionfollow them up, has resulted in the detection of Type Ia supernovae at huge distances.of Type Ia supernovae at huge distances.


Evidence for dark energyOver 100 Type IaOver 100 Type Ia supernova have beensupernova have been found at redshifts 0.5-found at redshifts 0.5-1.51.5Comparing these to Comparing these to nearbynearby supernova, we find that supernova, we find that inin cosmological models cosmological models withwith matter only, the distant matter only, the distant supernovae are fainter supernovae are fainter than than expected for their expected for their redshift.redshift.

‘‘Dark energy’ is pushing Dark energy’ is pushing thethe galaxies apart.galaxies apart.

redshift, or distanceredshift, or distance


What is Dark Energy ? According to Einstein’s General Theory of Relativity, there can be an extra term in the equation for gravity, which on large scales turns gravity into a repulsive force (the ‘cosmological repulsion’)

This extra term, denoted , behaves like the energy density of the vacuum, hence ‘dark energy’

So far there is no particle physics explanation for this

dark energy


The CMB is incredibly smooth, to one part in 100,000, The CMB is incredibly smooth, to one part in 100,000, but the very small fluctuations, or ‘ripples’, first but the very small fluctuations, or ‘ripples’, first

mapped by the COBEmapped by the COBE

mission, are the precursors of the structure we see mission, are the precursors of the structure we see today.today.

They also tell us about the matter and energy present They also tell us about the matter and energy present in the early universein the early universe

Mapping the Cosmic Mapping the Cosmic Microwave Microwave BackgroundBackground


History of the universe


Origin of the universe there are speculations about the origin of the universethere are speculations about the origin of the universe

theoretical physicists are trying to unify gravitation (ie General theoretical physicists are trying to unify gravitation (ie General Relativity) andRelativity) and quantum theory into a single unified ‘theory of everything’quantum theory into a single unified ‘theory of everything’

current favourite is ‘string theory’, but so far this makes no current favourite is ‘string theory’, but so far this makes no predictions aboutpredictions about the observed universe, instead we have the ‘string landscape’the observed universe, instead we have the ‘string landscape’

one popular idea is ‘chaotic inflation’ - our universe arose out of a one popular idea is ‘chaotic inflation’ - our universe arose out of a vacuumvacuum fluctuation in an infinite fluctuating voidfluctuation in an infinite fluctuating void

in this picture there might be many parallel universes, each with in this picture there might be many parallel universes, each with differentdifferent properties - the ‘multiverse’properties - the ‘multiverse’

currently no evidence to support this idea, or the ‘anthropic currently no evidence to support this idea, or the ‘anthropic principle’, which isprinciple’, which is supposed to select which type of universe we find ourselves insupposed to select which type of universe we find ourselves in


Fate of the universe if the current consensus model, with a dominant role for dark if the current consensus model, with a dominant role for dark energy, isenergy, is correct, the fate of the universe is a bleak onecorrect, the fate of the universe is a bleak one

the distances between galaxies will increase at an ever-accelerating the distances between galaxies will increase at an ever-accelerating rate, butrate, but the horizon will remain fixed at more or less its current size, 13 the horizon will remain fixed at more or less its current size, 13 billion light yrsbillion light yrs

eventually, after 100 billion years, our Galaxy will have merged witheventually, after 100 billion years, our Galaxy will have merged with Andromeda and our other neighbours in the Local Group into a single Andromeda and our other neighbours in the Local Group into a single largelarge and dying galaxyand dying galaxy

there will be no other galaxies within our observable horizonthere will be no other galaxies within our observable horizon

eventually all star formation will cease, all stars will die, black holes eventually all star formation will cease, all stars will die, black holes willwill evaporate, and finally protons and neutrons will decayevaporate, and finally protons and neutrons will decay

as the Greek poet Sappho put it: ‘nothing will remain of us’as the Greek poet Sappho put it: ‘nothing will remain of us’


The unanswerable questions

• Is the universe spatially finite or Is the universe spatially finite or infinite ?infinite ?

- there is a horizon defined by how there is a horizon defined by how farfar light has travelled since the Big light has travelled since the Big BangBang

• What was there before the Big What was there before the Big Bang ?Bang ?

-our theories break down before we our theories break down before we can can extrapolate to the Big Bang itselfextrapolate to the Big Bang itself


James Webb Space Telescope how to detect z = 10 galaxies ?


ALMA, 2010

Documents

Nov 22nd 2008Institute of Physics, Liverpool FRONTIERS OF ASTROPHYSICS - giant telescopes, space missions and invisible wavelengths Michael Rowan-Robinson