Dark Matter Da yang Jacob Daeffler

What do we mean by dark matter? Material whose presence can be inferred from its effects on the motions of stars and galaxies, but which cannot be seen directly because it emits little or no radiation. Material whose presence can be inferred from its effects on the motions of stars and galaxies, but which cannot be seen directly because it emits little or no radiation. Also know as missing mass. Also know as missing mass.

Contents of the Universe “ Normal ” Matter: ~ 4.4% “ Normal ” Matter: ~ 4.4% Normal Matter inside stars:~ 0.6% Normal Matter inside stars:~ 0.6% Normal Matter outside stars:~ 3.8% Normal Matter outside stars:~ 3.8% Dark Matter: ~ 25% Dark Matter: ~ 25% Dark Energy~ 71% Dark Energy~ 71%

Evidence for Dark Matter In Galaxies; In Galaxies; In Clusters of Galaxies. In Clusters of Galaxies.

Evidence for Dark Matter in Galaxies

With out Dark Matter The motion of stars in a galaxy should be like fixed points on turning disk. The motion of stars in a galaxy should be like fixed points on turning disk. The motion of planets in our solar system. The motion of planets in our solar system. OR

Scientist who first proved dark matter The first to provide evidence of and infer to the existence of a phenomenon that has come to be called "dark matter" was Swiss astrophysicist Fritz Zwicky, of the California Institute of Technology (Caltech) in The first to provide evidence of and infer to the existence of a phenomenon that has come to be called "dark matter" was Swiss astrophysicist Fritz Zwicky, of the California Institute of Technology (Caltech) in 1933.

Scientist who first proved dark matter He applied the virial theorem to the Coma cluster of galaxies and obtained evidence of unseen mass. When he compared this mass estimate to one based on the number of galaxies and total brightness he found there was 400 times more mass than expected. He applied the virial theorem to the Coma cluster of galaxies and obtained evidence of unseen mass. When he compared this mass estimate to one based on the number of galaxies and total brightness he found there was 400 times more mass than expected.

Rotation Curves Forty years after Zwicky a scientist named Vera Rubin found that most stars in galaxies orbit at roughly the same speed which means that their masses were more than the locations of the most stars. This says that more than fifty percent of the mass of galaxies is contained in a dark galactic halo. Forty years after Zwicky a scientist named Vera Rubin found that most stars in galaxies orbit at roughly the same speed which means that their masses were more than the locations of the most stars. This says that more than fifty percent of the mass of galaxies is contained in a dark galactic halo.

The visible portion of a galaxy lies deep in the heart of a large halo of dark matter

Evidence for Dark Matter in In Clusters of Galaxies We can measure the velocity of the galaxies in a cluster and from that velocity compute the mass and the mass is much larger than the mass of the stars

Does dark matter really exist? Our Options Dark matter really exists, and we are observing the effects of its gravitational attraction Dark matter really exists, and we are observing the effects of its gravitational attraction Something is wrong with our understanding of gravity, causing us to mistakenly infer the existence of dark matter Something is wrong with our understanding of gravity, causing us to mistakenly infer the existence of dark matter

YES! 1. Dark matter really exists, and we are observing the effects of its gravitational attraction 2. Something is wrong with our understanding of gravity, causing us to mistakenly infer the existence of dark matter Because gravity is so well tested, most scientists prefer option #1

Composition of Dark Matter Dark matter can be categorized by either baryonic or non-baryonic Dark matter can be categorized by either baryonic or non-baryonic Baryonic contains baryons which are protons and neutrons. Examples are non- luminous gas, MACHO’s (massive compact halo object) and brown dwarfs Baryonic contains baryons which are protons and neutrons. Examples are non- luminous gas, MACHO’s (massive compact halo object) and brown dwarfs

NonBaryonic Consists of nonbaryonic particles such as electrons and neutrinos Consists of nonbaryonic particles such as electrons and neutrinos Hot dark matter-nonbaryonic particles that move ultrarelativistically. Hot dark matter-nonbaryonic particles that move ultrarelativistically. Warm dark matter-nonbaryonic particles that movie relativistically. Warm dark matter-nonbaryonic particles that movie relativistically. Cold dark matter-nonbaryonic particles that move non-relativistically. Cold dark matter-nonbaryonic particles that move non-relativistically.

Types of Dark Matter Ordinary Dark Matter (MACHOS) Ordinary Dark Matter (MACHOS) Massive Compact Halo Objects: Massive Compact Halo Objects: dead or failed stars in halos of galaxies Extraordinary Dark Matter (WIMPS) Extraordinary Dark Matter (WIMPS) Weakly Interacting Massive Particles: Weakly Interacting Massive Particles: mysterious neutrino-like particles

Role of Dark Matter in galaxy formation ↓ Gravity of dark matter is what caused protogalactic clouds to contract early in time Dark matter is still pulling things together After correcting for Hubble’s Law, we can see that galaxies are flowing toward the densest regions of space

Summary What is Dark Matter; What is Dark Matter; Evidence of Dark Matter; Evidence of Dark Matter; Composition of Dark Matter; Composition of Dark Matter; Types of Dark Matter; Types of Dark Matter; Role of Dark Matter in galaxy formation Role of Dark Matter in galaxy formation