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Beeps, Flashes, Bangs and Bursts

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Beeps, Flashes, Big stars work much faster: Bangs and Bursts. 1,000,000 100,000 100,000 100,000 and Chirps. Forever Peter Watson 3 hours! Live fast, Die Young! Peter Watson, Dept. of Physics Change colour, size, brightness •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 Peter Watson Peter Watson If Stars are large.... • we get supernovae • 6 visible in Milky Way over last 1000 years •well understood: work by blocking mechanism • SN 1006: Brightest •very important since period is proportional to Supernova. intrinsic brightness: • Can see remnants of the expanding •i.e. measure the apparent brightness, the period tells shockwave you the actual brightness, so you know how far away Frank Winkler (Middlebury College) et it is al., AURA, NOAO, NSF Peter Watson Peter Watson Remnant of a very Tycho’s old SN Supernova • Part of the veil nebula in X-rays in Cygnus (1572) Sara Wager NASA / CXC / F.J. Lu (Chinese Academy of Sciences) et al. Peter Watson Peter Watson The Crab (M1) •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." PW Peter Watson 1054: Crab •Recorded by Chinese astronomers as “guest star” •May have been recorded by Chaco Indians in New • X-rays (in blue) Mexico • + Optical 4 a.m. Tuesday 7th May 1054 • Tangled Would have been as bright as the appearance due to New moon trapped magnetic field Moon Crab Peter Watson Peter Watson •Shock wave blows off outer layer of star at What happens to a star when 1/10 speed of light it goes supernova? •Large star runs out of fuel •Collapses and heats up •Outer part explodes out, •Core gets compressed to neutron star or black hole Peter Watson Peter Watson •Most recent close one was SN1987a Surprisingly… •Must have blown up earlier, leaving ring of • Most (98%) of the material, now illuminated by new shock energy doesn’t come wave out as light… • It’s neutrinos • As the matter falls in, the nu’s stream out! Image credit: TeraScale Supernova Initiative. Peter Watson Peter Watson Which we can •We would like to catch supernovae before see here… 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 Peter Watson Peter Watson •The Crescent Nebula is a shell of gas surrounding a •NGC 3603: can see formation of stars very hot and unstable central star WR 136 •contains Sher 25 surrounded by rings: • Should undergo a supernova explosion in next proably pre-collapse million years. Peter Watson Peter Watson •Nova: stars that repeatedly have minor explosions Might look like this •Always a close binary •material flows from one star to companion Mark A. Garlick (Space-art.co.uk) •triggers explosion Peter Watson Peter Watson •V838 Monocerotis: Not What happens to a star after a nova, since star did not lose material, it goes supernova? instead went to M~ -7 (brightest star in •Large star runs out of fuel galaxy) by expanding and cooling very fast •Collapses and heats up lit up dust from • Outer part explodes out, previous explosions • •Core gets compressed to neutron star or black hole Peter Watson Peter Watson • Pulsars • accidentally observed (1968) by Jocelyn Bell etc. Best known is Crab. • Very regular radio pulses Known to be • period of 2 ms up to 4 s supernova remnant from • Note that height of pulse is very irregular in 1054 Pulsar at centre has period of ~1/30 s Peter Watson Peter Watson And you can even listen to Magnetars: Vicki Kaspi McGill 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) • Magnetic field is ~ 1 billion x strength of MRI magnet Peter Watson Peter Watson •This shows how the X-ray pulses move Double Pulsar through the nebula • Peter Watson Peter Watson •Charged particles travel along magnetic What pulses? field, • Now known to be neutron star: predicted by • can only escape from poles of neutron star. Oppenheimer (yes, that one) in 1935. •Hence "lighthouse"mechanism: we only • Density ~ atomic nucleus: dime would weigh “see” pulsar when mag. pole points towards 2000,000,000 tons! us Peter Watson Peter Watson Do we see all the pulsars? This is how the Fermi satellite • No, because they would have to be oriented sees the sky, in gamma-rays 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 Peter Watson Peter Watson Gamma-rays have huge energies SS433 • And some things are just weird! • Crab? • A cosmic lawn sprinkler • OK: old supernova Geminga • jets come out at 1/5 of speed of light, but Vela? • Crab are made of cold hydrogen gas! • 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 Peter Watson Peter Watson KIC 8462852 or WTF star ("Where's Why? The Flux?") • Produces 20% change in • Huge planet? output over a matter of a few days • Alien megastructures? • Black Hole? • Dark Star? • Huge cloud of comets? Alien megastructures 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 Einstein was right: Astronomers • Invented by .....? confirm key theory on black holes Daily Express • Einstein!!!!!!!!! Historic First Images of a Black Hole Show Einstein Was Right (Again) Space.com Peter Watson Unfortunately Einstein predicted The essential result of this black holes did not exist! 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. PW PW Black Holes Black Holes • Invented by .....? • Invented by .....? • Einstein • Einstein • Hawking!!!!!!!!!!! • Hawking • Well, actually he didn’t: first paper he wrote was in • John Wheeler 1971 (and first interesting paper was 1974!) 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 Peter Watson Black Holes • Invented by .....? • Einstein Black • Invented by .....? • Hawking? Holes • Einstein • John Wheeler? • Hawking • Karl Schwarzchild? • John Wheeler • Well, actually, John Michell, rector of Thornhill Church in Yorkshire • Karl Schwarzchild? • geologist?philosopher? astronomer? Seismologist? • Polymath. No, but he was the first person to presented his ideas on “dark stars” to the Royal solve Einstein’s equations for one • Society in London in 1783. Peter Watson Peter Watson •A particle will •However we can interpret this differently: what escape from the radius would the earth have for a given escape earth if it has velocity? positive energy •In particular, if the escape velocity is the speed of •At the earth's light c, nothing can escape. surface, “escape velocity” is 11 •If the earth was 8 mm in radius, it would be a km/s Black hole •This is the Schwarzchild radius: roughly the black hole radius Peter Watson Peter Watson So what is a black hole like? • What is a straight line? • It warps space (and time) round it So planets are actually moving in "straight" lines in a curved space... Did you think a laser beam was straight? • "Lenses extend unwish through curving wherewhon till unwish returns on its unself" e.e.cummings Peter Watson Peter Watson •Stuff falling in will become very hot and produce X-rays •One way to see a black hole: it’s black! •If we are really lucky....(or unlucky) as a gap •So want binary star, one invisible but heavy, producing in the sky 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 Too Close to a Black Hole Credit & Copyright: Robert Nemiroff (MTU)< sun! Peter Watson Peter Watson Note Stephen Hawking’s Why Einstein was wrong: BH’s are formed explosively 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 PW •Then moving BH’s will produce a wave in space •Black Hole merger: The Caltech/Cornell SXS Collaboration • Peter Watson Peter Watson •And this is maybe where it is happening now: •and these will radiate gravitational waves •Two galaxies have collided and the black holes seem to be coalescing 3C75 X-rays from Chandra Peter Watson Peter Watson •Which we might be able to pick up on earth One of the first attempts as gravitational waves • Giorgio Pappini at •This is LIGO: twin detectors in Louisiana University of Regina and Washington • Build cold quartz- crystal detector U of R Peter Watson Peter Watson Peter Watson and they found a second Nobel Prize in Physics one! • Which you can listen to! 2017 Kip Thorne Rainer Weiss Barry Barish Peter Watson Peter Watson •Vary short (often less than 1/100 s!) intense Gamma-ray bursters bursts of γ-rays.
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