The Hubble Space Telescope - the first 10 years

• Our only optical telescope in space– Why, when and how

• Observations– Planets– Stars– Galaxies– Cosmology

• The Next Generation Space Telescope

HST: .

• An Orbital Telescope (90mins/orbit)

• Launched April 24th ‘90

• Serviced mid-Dec ‘93

• Visible From Earth by Eye

The Launch: .• April 24th 1990

• Space Shuttle Mission ST-31

• 10x faster than a rifle bullet !

Overview: .

• 2.4 metre mirror

• Solar Panels for energy

• 4 instrument payload

• Comms

• Shutter

• Gyros

The Benefits of Space• No atmosphere = crystal sharp images

• No sky glow = very deep images

Hubble Trouble• But,to our horror we discovered Hubble’s

mirror was the wrong shape !

• In 1993 a service mission (ST-62) was sent up to replace some of the optics

• Since then its worked perfectly

• Here’s the difference >

Hubble Trivia• Named after Edwin Hubble who discovered

the expansion of the universe

• Project conceived in 1971

• Total cost around US $1 billion !

• Now Operational for 10 years

• Observed 14,000 objects

• Orbited the Earth 58,400 times

• Travelled 1.5 billion miles

• Can see back to when the Universe was 10% of its current age (13 billion years ago)

Where HST has been looking• This shows the places on the sky where

HST has looked. Milky-way across centre.

Our Solar System• In our Solar System are 9 planets: Mercury,

Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto plus an asteroid belt, Kuiper belt, moons and of course the sun.

• HST cannot look at Mercury because it is too close to the sun and would damage the telescope.

• It has looked at everything else though >>>

Our Solar System with HST

Comets• Comets are gigantic icy rocks which whiz

through the Solar System at v.high speeds.

• It is believed a comet killed the dinosaurs and the impact created the gulf of Mexico

• Thankfully Comet impacts are very rare.

• However: In 1995 a comet hit Jupiter !

The Impact of Fragment G

• Provided information on the rotation of Jupiter’s atmosphere, its thickness and its composition

Stars• Stars form from giant gas clouds floating in space

• The cloud first starts to collapse due to gravity

• When sub-clumps reach a sufficiently high density Nuclear fusion occurs bathing the region in radiation

• This radiation blows away any remaining dust

• Finally we’re left with a star cluster

• Eventually each star explodes (Supernovae)

• All that remains is a black hole, neutron star or white dwarf

• HST has looked at all stages of this process >>>

Stars: Gas Collapses

• The Trifid Nebula: A Stellar Nursery

• Gas is collapsing due to gravity and where it becomes dense enough stars are formed and nuclear fusion occurs

Stars: Stars Ignite

• The Eagle Nebula

• Radiation from the newly formed stars moulds the gas remaining into the spectacular gaseous pillars we see here

Stars: The First Stars

• An emerging star cluster: NGC3603

• As the gas is blown away the newly formed star cluster becomes visible

• At this stage the light is dominated by the very hot but short-lived blue stars

Stars: A Cluster is formed

• A Star Cluster

• As the hot blue stars burn out we are left with a star cluster. All remaining gas is now blown far away and this cluster will stay like this for many billions of years

Stars: Stellar Outflows

• Eta Carinae• Many stars form as

binary systems, during the course of their active phases mass is often transferred from one star to the other. If this matter is accreted too fast it squirts out of the poles of the secondary star

Stars: Supernova

• Superova: NGC6543

• Stars end their life-cycle by going Supernova or Nova depending on their initial mass

• The most massive go supernova and blow off their outer shell whilst the core collapses into a black hole

Stars: Planetary Nebulae

• The Spiral Nebula

• The shell of material blow off settles down and the remaining core can often pulsate if it is not massive enough to form a black hole

• Galaxies consist of about 1billion stars

• Once called “Island Universes”(Kant)

• 3 main types:– Ellipticals (Smooth, Old and Red)– Spirals (Bulge plus spiral arms)– Irregulars (Newly formed or interacting)

• HST allows us to look closely at the regions where stars form and to see their structure back to when the Universe was young

Galaxies

Galaxy Clusters

• Here we see a typical example of an elliptical galaxy (centre) and a spiral galaxy (right).

• Galaxies often form in groups of clusters. Here we see the nearby core of the Coma cluster of galaxies

Galaxies and star-formation• The smaller panel shows NGC4314 as viewed

from the ground. The larger panel shows the core as seen by HST. The purple and blue regions indicate where star clusters are forming

Peculiar Galaxies and mergers• Galaxies are believed start from small sub-clumps

which through merging build themselves up to giant ellipticals and spirals. Here we see the merger of two giant spirals which will one day become a giant elliptical. The core of each galaxy is seen in red and most likely each core contains a giant black hole.

• Our galaxy is on collision course with Andromeda and one day may look like this.

• The most famous single image is: The Hubble Deep Field (150 orbits of data)The Hubble Deep Field (150 orbits of data)

• It only covers 1millionth of the sky but:– It’s the deepest image ever taken of the Universe

looking back to when the Universe was: 1 billion years old (I.e., 10% of its current age)1 billion years old (I.e., 10% of its current age)

– In it we see that the most distant galaxies are very irregular unlike the spirals and ellipticals we see today=> GALAXIES FORMED VIA MERGERSGALAXIES FORMED VIA MERGERS

– With HST we finally see the main epoch of GALAXY FORMATION ~8billion years agoGALAXY FORMATION ~8billion years ago

The Hubble Deep Field

The Hubble Deep Field

• The Deepest image ever taken of our Universe

Galaxy Evolution• From the Hubble Deep Field we see that galaxies look

normal back until 30% of the age of the Universe at which point the number of Peculiars and mergers increases. This panel shows samples of galaxies at different ages

starting from today and stretching back until the Universe was 10% of its current age.

Cosmology• There are 4 numbers that define our universe

1) The Expansion Rate (Hubble Constant) 2) The Density of Matter 3) The Density of Radiation 4) The Density of Space-time

• The Hubble Space Telescope is measuring (1) the expansion rate of the universe today !

• The other parameters are being measured from other satellites which are looking at the Cosmic Microwave Background

An Analogy (Car=Universe)• Think of a car heading down the street out

of control with the brake, hand brake and accelerator all jammed on !

• We want to know whether it’s going to stop, get faster or stay at a constant speed !

• Whether this happens is determined by its current speed, and the battle between the brakes and the accelerator !

The Car and the Universe• The car is the Universe and we want to

know whether the Universe is going to stop expanding and recollapse or continue to expand for ever.– The Hubble constant is the cars speed right now– The density of matter is the footbrake– The density of radiation is the handbrake– The density of Spacetime is the accelerator

(also known as the Cosmological Constant)

• Measuring the Hubble Constant is a crucial step

• Aim, to measure the expansion rate of the Universe => the age of the universe!

• To do this we need a very accurate distance measurement, the velocity we already know

• But how do we measure distances ?

• Well some stars are known to pulsate at a rate which depends on their brightness.

• We can use this to calculate the distances to nearby galaxies.

• In the case M100 in the Virgo cluster

The HST Key Program

The Age of the Universe• All galaxies are moving away from us• The furthest galaxies move away faster• Hubble’s law => Universal Expansion• If we measure a galaxies speed and its

distance we can calculate how long it’s been travelling for (I.e., time=distance/velocity).

• All galaxies gives us the same answer !• This is an approximate* age of the Universe,

the point in space-time from which all matter originated (*as this ignores any braking and accelerating)

Calculating Distances

• If you move an object away it gets fainter

• Once its 10x further away it is 100x fainter

• Hence if we know how bright a star SHOULD be and we measure how bright it ACTUALLY is we can estimate the distance

• This relies on finding stars with KNOWN brightness and luckily their exist a class of star known as Cepheids which pulsate according to their brightness

• We can use these to measure distances

The Galaxy M100 The galaxy M100

lies in the nearby

Virgo cluster, we

know how fast

Virgo is moving

so now all we need

is its distance to get

the age of the

Universe

Finding the Cephieds To measure the distance we need to find Cepheids,

variable stars which pulsate according their brigthness. To do this we need to

observe M100 many

times and look for

stars whose

brightness varies

periodically. Here’s a

Cepheid found on the

outskirts of the galaxy

Monitoring their Brightness Once a Cepheid has been found we must measure its

brightness frequently to determine the period (which tells us its INTRINSIC brightness) and by comparing

this to its

APPARENT

brightness we can

estimate the

distance to M100.

Even with HST

this is very hard

Distance to M100

• Here’s the equation that we use:

m-M=5log(d)-5

m=The APPARENT Brightness in logarithmic units

M=The INTRINSIC Brightness in logarithmic units

d =The distance in parsecs (1parsec=3.3 light years)

• The APPARENT brightness we measure from the image, the INTRINSIC brightness we calculate from the PERIOD of the Cephied

• Eventually we get the crucial distance to M100

• HST provides a distance to M100 of: 16 Mpc = 50 million light years !16 Mpc = 50 million light years !

• From the ground we can measure the speed with which this galaxy is moving away: 1250 1250 km/s I.e., Every day M100 gets 108 million km/s I.e., Every day M100 gets 108 million km further away ! km further away !

• The ratio gives us the Expansion Rate of the Universe =78 km/s/Mpc78 km/s/Mpc

• It also gives an approximate age of the universe, remember t = d/v which gives about: 10 billion years10 billion years

The Hubble Constant

The Universe Today• Thanks to the Hubble Space Telescope we

have a picture in which our universe formed 10 billion years ago and 2 billion years into this the galaxies formed through mergers of smaller building blocks into the large and well ordered galaxies we see around us today - this new perspective into our Universe has only been possible by looking through the eye of the Hubble Space Telescope.

• So what is the next big question ?

The Fate of the Universe• Remember the Car hurtling our of control ?

– HST has measured its speed today

• We still have three more parameters to find– The Density of Matter = the footbrake– The Density of Radiation = the handbrake– The Density of Space-Time = the accelerator

• To measure these requires a combination of even more sophisticated telescopes and satellittes

NASA is planning an 8-metre telescope, a collecting area 11x large the the HST. To be launched in 2015. This will see even further and over larger chunks of sky. It will also see in other wavelengths and in particular the Infrared.

This telescope will

be sent into deep

space and a solar

shield will keep it

protected from the

sun

The Next Generation Space Telescope

Finally: my favourite image

• Gravitational Lensing by a Galaxy Cluster

THE END

• Cosmology and Astronomy is an exciting science entering a golden era of discovery. Soon we will know either the fate of the Universe or we’ll overturn the Big Bang model. Either way its an exciting time and an exciting place to be.

• HST Websites:– http://hubble.stsci.edu/– http://heritage.stsci.edu/– http://www.stsci.edu/– http://opposite.stsci.edu/pubinfo/picture.html