The Virgo Cluster. Distance today: 20 Mpc (million parsecs) Distance in 100 years: 20 Mpc Mpc. (Oh well) Look-back time to Virgo Cluster:

Transcription

1

2

3 The Virgo Cluster Map by Jan Wisniewski Distance today: 20 Mpc (million parsecs) Distance in 100 years: 20 Mpc Mpc. (Oh well) Look-back time to Virgo Cluster: 1 parsec = 3.26 light-years Light goes 1 light-year in one year (surprise!) 20 million parsecs means we see the Virgo clutser as it was 65 million years ago. λ λ λ λ λ µ

4 z z 1 z observed original Measuring the Expansion Measure distance to get lookback time (how long the light took to reach us) Measure redshift to get amount of expansion over that time. Size Size Today The Future??? The Big Bang Back in time Today Forward in time Object Sun Alpha Centauri Andromeda Galaxy Quasar 3C273 at z=0.158 Galaxy at z=1 Seyfert Galaxy NGC1068 Age of Universe Lookback Time 8 minutes 4 years 2 million years 16 million years 2 billion years 7 billion years 13 billion years Size Looking at standard Size Today candles (Type Ia supernovae) far enough back in time, we discovered that the expansion of the Universe is accelerating! Today Accelerating Universe Low-mass Universe High-mass Universe Critical Mass Universe Years in the Past t Years from Today

5

6 The Big Rip The Big Chill It all depends on just how bizarre Dark Energy is! Size Size Today 1.0 The Big Crunch 0.5 Today Years in the Past t Years from Today A galaxy twice as far away increased its distance twice as much. d = change in distance during time of movie ( t) d Hubble Law d t H 0 d The Milky Way H 0 = current expansion rate of Universe = 71 km/s / Mpc Every Point is the Center!

7 z 1+z = z z v c (For v c) Compare to Cosmological redshift: = d d d d v t d 1 vt d v 1 d t 1 v c For nearby galaxies (out to a few hundred million light-years), the cosmologic redshift looks just like a doppler shift. The galaxies flying apart description is a local Universe approximation. The expansion of the Universe is an expansion of space itself. Galaxies get farther apart, much as do raisins in rising bread, pennies pasted on the surface of an expanding balloon, or paper clips on a stretching elastic band. As the Universe expands, the wavelengths of light expand at the same rate. The three dimensional space of the Universe can be intrinsically curved, but large-scale geometry is flat (Euclidean). (Whew!) The expansion of the Universe is accelerating, and indicates that the Universe is filled with Dark Energy. Here be Dragons t (s) z T GeV 10 8 GeV 1 TeV 10 MeV 100 ev Inflation, Grand Unification Electroweak Protons/Neutrons Elements Form,... The beginning? Unification Form Cosmic Neutrinos t z T 30 yr Dark Ages kyr 440 kyr 17 Myr 480 Myr 13.7 Gyr K 270 K 27 K 2.7 K First Stars and Quasars You End of Galaxy Are Cluster Formation Here Universe Becomes Transparent Matter Domination Nuclei Capture Electrons Cosmic Microwave Background Sun Forms

8 Opaque Universe Transparent Universe You Are Here Cosmic Microwave Background

9 Flat Closed: Looks Bigger Open: Looks Smaller

10