Peter Watson, Dept. of Physics

Beeps, Flashes, Bangs and Bursts.

Peter Watson

and Chirps.

Big stars work much faster:

Live fast, Die Young!

100,000 1,000,000 100,000100,000

3 hours!

Forever

Peter Watson

•Vast majority of stars are boring: “main-sequence” (aka middle-class) changing very slowly.

•Some oscillate: e.g Cepheids

•Large bright stars change by factor 3 in brightness

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Change colour, size, brightness

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•well understood: work by blocking mechanism

•very important since period is proportional to intrinsic brightness:

•i.e. measure the apparent brightness, the period tells you the actual brightness, so you know how far away it is

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• we get supernovae

• 6 visible in Milky Way over last 1000 years

• SN 1006: Brightest Supernova.

• Can see remnants of the expanding shockwave

If Stars are large....

Frank Winkler (Middlebury College) et al., AURA, NOAO, NSF

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Remnant of a very old SN

• Part of the veil nebula in Cygnus

Sara Wager

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Tycho’s Supernova in X-rays

(1572)

NASA / CXC / F.J. Lu (Chinese Academy of Sciences) et al.

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The Crab (M1)

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•Recorded by Chinese astronomers

"I humbly observe that a guest star has appeared; above the star there is a feeble yellow glimmer. If one examines the divination regarding the Emperor, the interpretation [of the presence of this guest star] is the following: The fact that the star has not overrun Bi and that its brightness must represent a person of great value. I demand that the Office of Historiography is informed of this."

Peter Watson

1054: Crab• X-rays (in blue)

• + Optical

• Tangled appearance due to trapped magnetic field

Peter Watson

•Recorded by Chinese astronomers as “guest star”

•May have been recorded by Chaco Indians in New Mexico

Moon

Crab

4 a.m. Tuesday 7th May 1054Would have been as bright as the

New moon

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•Large star runs out of fuel

•Collapses and heats up

•Outer part explodes out,

•Core gets compressed to neutron star or black hole

What happens to a star when it goes supernova?

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•Shock wave blows off outer layer of star at 1/10 speed of light

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•Most recent close one was SN1987a

•Must have blown up earlier, leaving ring of material, now illuminated by new shock wave

Peter Watson

Surprisingly…• Most (98%) of the

energy doesn’t come out as light…

• It’s neutrinos

• As the matter falls in, the nu’s stream out!

Image credit: TeraScale Supernova Initiative.

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Which we can see here…

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•We would like to catch supernovae before they explode: here are 3 possibilities

Eta Carinae blew off a lot of material 150 years ago: probably

pre-collapse now

Credit: J. Morse (U. Colorado), K. Davidson (U. Minnesota) et al., WFPC2, HST, NASA

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•The Crescent Nebula is a shell of gas surrounding a very hot and unstable central star WR 136

• Should undergo a supernova explosion in next million years.

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•NGC 3603: can see formation of stars

•contains Sher 25 surrounded by rings: proably pre-collapse

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•Nova: stars that repeatedly have minor explosions

•Always a close binary •material flows from one star to companion •triggers explosion

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Might look like this

Mark A. Garlick (Space-art.co.uk)

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•V838 Monocerotis: Not a nova, since star did not lose material, instead went to M~ -7 (brightest star in galaxy) by expanding and cooling very fast

•lit up dust from previous explosions

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•Large star runs out of fuel

•Collapses and heats up

•Outer part explodes out,

•Core gets compressed to neutron star or black hole

What happens to a star after it goes supernova?

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• Pulsars

• accidentally observed (1968) by Jocelyn Bell etc.

• Very regular radio pulses

• period of 2 ms up to 4 s

• Note that height of pulse is very irregular

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Best known is Crab.

Known to be supernova

remnant from in 1054

Pulsar at centre has period of

~1/30 s

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And you can even listen to them

• This is Vela

• And this is PSR 0329+54

Period of Crab measured to be 0.03308471603 s (i.e. stable to 1 part in billion)

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Magnetars: Vicki Kaspi McGill

• Magnetic field is ~ 1 billion x strength of MRI magnet

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•This shows how the X-ray pulses move through the nebula

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•Double Pulsar

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What pulses?• Now known to be neutron star: predicted by

Oppenheimer (yes, that one) in 1935.

• Density ~ atomic nucleus: dime would weigh 2000,000,000 tons!

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•Charged particles travel along magnetic field,

• can only escape from poles of neutron star.

•Hence "lighthouse"mechanism: we only “see” pulsar when mag. pole points towards us

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• No, because they would have to be oriented so that they point towards us

• Neutron Star forms from supernova, Period ~1/1000 s

• spins down

• magnetic field will weaken

• Disappear after 100,000 years

Do we see all the pulsars?

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This is how the Fermi satellite sees the sky, in gamma-rays

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Gamma-rays have huge energies

• Crab?

• OK: old supernova

• Vela?

• OK: old supernova

• Geminga?

• Huh? Second brightest object in γ-rays, almost invisible as a ordinary star

• Turns out to be very old neutron star

Geminga

Crab

Peter Watson

SS433• And some things are just weird!

• A cosmic lawn sprinkler

• jets come out at 1/5 of speed of light, but are made of cold hydrogen gas!

KIC 8462852 or WTF star ("Where's The Flux?")

• Produces 20% change in output over a matter of a few days

Why?

• Huge planet?

• Alien megastructures?

• Black Hole?

• Dark Star?

• Huge cloud of comets?

Alien megastructures

Peter Watson

A Jupiter-sized planet would cause a 1% drop in light on a regular basis

Comets?

But it’s also been dimming slowly anyway

Peter Watson

Black Holes• Invented by .....?

• Einstein!!!!!!!!!

Einstein was right: Astronomers confirm key theory on black holes

Historic First Images of a Black Hole Show Einstein Was Right (Again)

Daily Express

Space.com

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Unfortunately Einstein predicted black holes did not exist!

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The essential result of this investigation is a clear understanding as to why the "Schwarzschild singularities" do not exist in physical reality. …………… The "Schwarzschild singularity" does not appear for the reason that matter cannot be concentrated arbitrarily. And this is due to the fact that otherwise the constituting particles would reach the velocity of light.

Peter Watson

Black Holes• Invented by .....?

• Einstein

• Hawking!!!!!!!!!!!

• Well, actually he didn’t: first paper he wrote was in 1971 (and first interesting paper was 1974!)

Peter Watson

Black Holes• Invented by .....?

• Einstein

• Hawking

• John Wheeler

Wheeler first used the term in a talk he gave in 1967. He understood that in

reality they would be small and dense, with the implication that they might be

observable.

Peter Watson

Black Holes• Invented by .....?

• Einstein

• Hawking

• John Wheeler

• Karl Schwarzchild?

No, but he was the first person to solve Einstein’s equations for one

Peter Watson

Black Holes

• Invented by .....?

• Einstein

• Hawking?

• John Wheeler?

• Karl Schwarzchild?

• Well, actually, John Michell, rector of Thornhill Church in Yorkshire

• geologist?philosopher? astronomer? Seismologist?

• Polymath.

• presented his ideas on “dark stars” to the Royal Society in London in 1783.

Peter Watson

•A particle will escape from the earth if it has positive energy

•At the earth's surface, “escape velocity” is 11 km/s

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•However we can interpret this differently: what radius would the earth have for a given escape velocity?

•In particular, if the escape velocity is the speed of light c, nothing can escape.

•If the earth was 8 mm in radius, it would be a Black hole

•This is the Schwarzchild radius: roughly the black hole radius

Peter Watson

So planets are actually moving in "straight" lines in a curved space...

• "Lenses extend unwish through curving wherewhon till unwish returns on its unself" e.e.cummings

So what is a black hole like?• It warps space (and time) round it

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• What is a straight line?

Did you think a laser beam was straight?

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•One way to see a black hole: it’s black!

•If we are really lucky....(or unlucky) as a gap in the sky

Too Close to a Black Hole Credit & Copyright: Robert Nemiroff (MTU)<

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•Stuff falling in will become very hot and produce X-rays

•So want binary star, one invisible but heavy, producing lots of X-rays

First candidate is Cygnus X-1

Mass of primary star ~20Mo

Mass of invisible object M~9Mo

Power output in X-rays is 10,000 x total power output by sun!

PW

Note Stephen Hawking’s main claim to fame

• He bet Kip Thorne a year’s subscription to Penthouse that Cyg X-1 was NOT a BH Supernova-

Black Hole formation animation from Chandra

Why Einstein was wrong: BH’s are formed explosively

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•Then moving BH’s will produce a wave in space

•

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•Black Hole merger: The Caltech/Cornell SXS Collaboration

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•and these will radiate gravitational waves

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•And this is maybe where it is happening now:

•Two galaxies have collided and the black holes seem to be coalescing

3C75 X-rays from Chandra

U of R

One of the first attempts

• Giorgio Pappini at University of Regina

• Build cold quartz-crystal detector

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•Which we might be able to pick up on earth as gravitational waves

•This is LIGO: twin detectors in Louisiana and Washington

Peter Watson Peter Watson

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and they found a second one!

• Which you can listen to!

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Rainer Weiss Barry BarishKip Thorne

2017

Nobel Prize in Physics

Peter Watson

Found accidentally by Vela satellite (designed to look for γ's from nuclear explosions).

Gamma-ray bursters

Peter Watson

•Vary short (often less than 1/100 s!) intense bursts of γ-rays.

•Don’t repeat, don’t come from any known object

Seem to be massive explosions

in very distant galaxies

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• Common (about 1/week)

• Extremely energetic (energy ~ all stars in known universe concentrated into few seconds)

• No two the same!

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Scattered all over the sky

If they were local they would map out the Milky Way

Wikipedia

All the Gold you dreamed of….

But where did it c

ome

from????

????

PW

A long story……

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Mostly science has no dramatic moments: e.g. DNA

• isolated (Friderich Miescher) ~1885

• nucleotides identified Phoebus Levene ~ 1919

• "giant hereditary molecule" (Koltsov) ~ 1927

• Genetic material in T2 Phage (Hershey) ~1953

• X-ray diffraction show helix (Wilkins & Franklin) ~ 1953

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• DNA is two interlocked coils of amino-acids

====> Central Dogma: Watson & Crick 1953

Peter Watson

•Lived in Pisa

GALILEO (1564-1642)

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• Exploited (but didn’t invent) telescope

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• Moons of Jupiter: Jan 7/8th 1608

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Galileo shows BOTH Prolemy and Copernicus are • The earth is not the centre of the universe,

but more things than the sun can be the centre of orbits

• Need Newton to understand this

Peter Watson

This is his original notebook

Where does everything come from?

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To make heavy nuclei, just add protons & neutrons

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To start with, fusing light nuclei to make heavier nuclei GIVES us energy

• But after Iron, we need to add energy to create new nuclei

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•Type 1a Supernova

•Very rare (1/galaxy/century), very bright and they are all the same

•This is one in Centaurus A

Long straight bit of light curve is decay

of Co56 to Iron

Created in Big BangSmall Stars

Large stars & supernova

????????????????????????????

Where does everything come from? Cassiopeia A Supernova remnant from about 350 years ago

silicon red, sulphur yellowcalcium green iron purpleX-rays blue

Image Credit: NASA, CXC, SAO

neutron star

PW

Confused? An executive summary

• We don’t know where the heavy elements come from

• We don’t know what gamma-ray bursters (GRB’s) are

• We don’t know if gravitational waves travel at the speed of light

• We’ve never seen two stars collide!

PW

August 17, 2017, 12∶41:04 UTC• Gravitational Wave Signal seen

It all comes

together!

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1.7 s later,

Gamma-ray pulse

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Where is it?

Email your friends…

GW+EM Observatories MapApproximately 70 light-based observatories that detected the gravitational-wave event called GW170817. PW

Dark-Energy Camera in Chile finds it first!

NGC 4993: The Galactic Home of an Historic Explosion

Image Credit: NASA & ESA

In Hydra

PW

And that’s how the gold in your wedding ring was made!

Jastrow, Wikimedia

Approximately 10 Earth Masses of Gold and Platinum!

~10,000,000,000,000,000, 000,000,000 tonnes

Wedding ring, Byzantium, 7th c. AD, nielloed gold

NASA

What it looked like..

So in one day… 6000 people round the world

• Verified Einstein (gravitational waves exist and travel at the speed of light)

• Explained GRB’s as colliding neutron stars

• Observed a “kilonova” for the first time

• Showed us how elements are made

• A good day for al

l of us!