Caty Pilachowski Mini-University 2013 Our Milky Way in Space and Time

Our Journey…  Where in the Galaxy Are We?  The Local Neighborhood  Top Milky Way Destinations!  The Dark Heart of the Galaxy  Formation of the Milky Way  Our Galaxy in the Cosmos

Where Are We???

A Thin Disk of Stars 100,000 Light Years

What Is a Light Year?   The distance light travels in one year (about 6 trillion miles)   Light travels at 186,000 miles per second The Moon is 1 light-second from Earth The Sun is 8 light-minutes from Earth The nearest star, Proxima Centauri, is four light years from the Sun

Disk Bulge Halo Hot Young Stars Spiral Arms Dust Lanes Galactic Center The Sun Light takes 100,000 years to cross the Milky Way Our Home

Meet the Neighbors  Proxima Centauri  Alpha/Beta Centauri  Most nearby stars are small, dim and cool

100 Light Years

500 Light Years Polaris

Orion Nebula Distance: ~1300 light years X

Orion Nebula Distance: ~1300 light years X

Pillars of Creation Lower density gas has been eroded away, leaving pillars of higher density gas where stars are forming Lower density gas has been eroded away, leaving pillars of higher density gas where stars are forming Eagle Nebula with Hubble X

Crab Nebula  The remnant of an exploded star  The explosion was recorded in 1054 CE ESO X

Ring Nebula  The remnant of a dying star  The ring will fade, and the central star will become a white dwarf X WIYN

Globular Cluster  Messier 3  Age – 13 billion years  500,000 stars WIYN X

Cygnus X-1  A binary star containing a black hole  Mass from the star is pulled into the black hole X

The Galactic Center! In visual light, this region is hidden from us by gas and dust that dim the light by a factor of 10 billion!

The Galactic Center in Infrared Light The dust is transparent to infrared light, and we can see through the gas and dust to observe the Galactic Center

The Galaxy hosts a super- massive black hole at its heart!  Orbits of stars around the central mass is consistent with a 4 million solar mass object at the Galactic Center

Massive Black Hole!  Detected in infrared, radio, and x-ray light  Mass 4 million times the Sun’s mass  Growing slowly through accretion  All big galaxies host central black holes

A Gas Cloud Approaches the Black Hole!  The cloud will pass within 36 light hours next month (July)  ~3 Earth masses  ~2000 miles per sec Animation!

The Universe Contains Many Spiral Galaxies We learn about our Milky Way from other galaxies

Forming the Milky Way Galaxies like the Milky Way form from the consolidation of many primordial gas clouds Galaxies like the Milky Way form from the consolidation of many primordial gas clouds Collisions of gas clouds create bursts of star formation to shape the Galaxy Collisions of gas clouds create bursts of star formation to shape the Galaxy

The Milky Way Is Still Growing  Nearby dwarf galaxy discovered in 1994 in the direction of Sagittarius  Distance about 88,000 light years  Merging with the Milky Way

Galaxy’s “New” Tidal Stream  Sagittarius orbits the Milky Way  The orbital period is about a billion years  “Tidal stream” of stars from Sagittarius circles the Milky Way

The Local Group  The Milky Way is part of a small group of galaxies known as the local group  Andromdea Galaxy  Milky Way Galaxy  Triangulum Galaxy  Many small ones 2.5 million light years

Galaxy Collision!

The Local Group Is Part of an EVEN BIGGER Group  The Local Group is part of the Virgo Super Cluster of Galaxy Groups

Newly Discovered Galaxy!  The Leo P galaxy was just discovered here at IU using the WIYN Telescope  Five million light years from the Milky Way  Undisturbed, in an empty part of nearby space

Our Home in the Cosmos