The The DangerDanger of Deadly Cosmic Explosions of Deadly Cosmic ExplosionsSupernovae and Gamma Ray BurstsSupernovae and Gamma Ray Bursts

John LearnedUH Physics & Astronomy, 4 May 2005

Stars Get OldStars Get Old

• Stars run out of fuel.• Smaller stars

– Long (billions of years) boring lives,

– Flash before senescence (like the sun).

• Big stars (10-100 sun mass), – Live fast (millions of years)– Die young, glorious display…

a supernovasupernova– Brighter than a galaxy for a

few days– More radiation than during

whole life of star

Sanduleak Sanduleak 69 69 202202

Large Magellanic Cloud Large Magellanic Cloud Distance 50 kpcDistance 50 kpc (160.000 light years)(160.000 light years)

Tarantula NebulaTarantula Nebula

Supernova 1987ASupernova 1987A 23 February 198723 February 1987

Georg Raffelt, Max-Planck-Institut für Physik, München, Germany

A Nearby Supernova Can Ruin Your Existence

• DeadlyDeadly from neutrinos within 30 light years.

• Atmosphere, weather, ruined.• Major extinctionMajor extinction.• Not much harm if furtherNot much harm if further.• SN material in sediments.• 1 SN/100 years in our galaxy • Close 1 per 100million years.• Good newsGood news: our neighbor

stars peaceful.• Bad newsBad news: when one does

show signs of blowing, time to migrate.

Gamma Ray BurstsGamma Ray Bursts

30 year mystery.

Brightest flashes seen.

Usually billions of light years away.

Jets from Supernovae?

Beaming factor: 340? 10,000?

Beams may reachacross galaxy.

Can happen here!

Eta Carinae Ready to Blow?Ready to Blow?

• Brightest star in galaxy – 4 million x sun

• Maybe still dangerous at 7000 light years

• Fortunately not pointednot pointed at us, we think.

• Other stars old too…

Recent “Soft GR Repeater” in Our Galaxy – SGR 1806-20, 12/27/04

• Brightest X-Ray burst– damaged satellites– affected radio.

• Across galaxy, maybe 50,000 light years away.

• Rotating neutron star, fantastic magnetic field.

• Spectacular, but not not lethally dangerous lethally dangerous – well, except for astronauts

maybe.

GRBs Can Zap Us from Across the Galaxy

• Narrow beam.• Enormous high energy

radiation• Penetrates underground and

underseas.• Equivalent to 1 kiloton TNT / 1 kiloton TNT /

kmkm22 over earth surface• Kills everything exposed.• Destroys atmosphere,

brings on nuclear winter.

Dar & DeRujula Astro-ph/0110162

The End May be in Sight!

• There areare galactic hazards to life on earth.

• Earth experienced some in the past.

• Explain lack of evident life in lack of evident life in galaxygalaxy?

• Cosmic disasters WILL WILL happenhappen eventually, within ~100 Million years.

• Keep watchKeep watch.• We shall have to leave earthleave earth

to survive, eventually.• But for now, everything is everything is

finefine, is fine, is fine….