1. Galaxies, Supernovas, & Black Holes
By: Vanessa Koniecki
EDU 370

2. General Galaxy Information
Galaxies are vast systems of stars that populate the Universe.1
Typically contain several million to some trillion stars.3
They also contain various types of star clusters and nebulae.3
star cluster=Globular clusters are gravitationally bound concentrations of approximately ten thousand to one million stars.3
nebulae= clouds of dust or gas4

3. General Galaxy Information II
Our own Milky Way galaxy is just one of the billions of galaxies now known to exist.4
A typical galaxy is 100,000 light-years in diameter. 4
The nearest giant neighbor is the Andromeda Galaxy, a spiral galaxy, and is about 2-3 million light years distant.3

4. Types of Galaxies
Spiral ~75%
Lenticular
Elliptical 20%
Irregular 5%

5. Types of Galaxies II8

6. Types of Galaxies III
Some elliptical galaxies show no evidence of having formed stars since a brilliant epoch early in cosmic history, while spiral and irregular galaxies have been making stars briskly over their entire lifetimes.6
Some galaxies produce most of their energy deep in the infrared, and some are so diffuse and faint as to be barely detectable against the faint glow of the Earth's night sky.6

7. Hubble Approaches 'Final Frontier'
Several expert teams have at last identified what may turn out to be some of the earliest star-forming galaxies. These faint sources, circled in the image above, illustrate how astronomers can begin to explore when the first galaxies formed and what their properties might be.2

8. A Galactic 'Late Bloomer'
NASA's Hubble Space Telescope has snapped a view of what may be the youngest galaxy ever seen.2

9. Spitzer's Legacy
NASA's Spitzer Space Telescope has captured infrared images of the "Whirlpool Galaxy" (M51), revealing strange structures bridging the gaps between the dust-rich spiral arms, and tracing the dust, gas and stellar populations in both the bright spiral galaxy and its companion.2

10. The Milky Way Galaxy We are part of the Milky Way Galaxy.1
Diffuse band of light crossing the night sky.1
A flattened disk of stars with a central bulge.1
Our own galaxy can be traced at least fifty thousand light-years from its nucleus, and we know of many galaxies much larger yet.6
1610: Galileo observed the Milky Way with his new telescope.1
1750: Thomas Wright1
Picture motivated by theological considerations
Wright made no new observations.
Thin spherical shell of stars with Sun about midway inside the shell.
Look along the tangent: broad band of stars
Look along thin part: few stars

11. The Milky Way Galaxy II

12. The Milky Way Galaxy III
1755: Immanuel Kant1
Misread a newspaper account of Wright's model.
Also made no observations.
Lens-shaped disk of stars rotating about its center.
Other "nebulae" are distant, rotating milky ways like ours.
Later became known as the "Island Universe" Hypothesis
1785: William & Caroline Herschel
Counted stars along 683 lines of sight using their 48-inch telescope.
Assumed all stars are the same luminosity, and that they could see to the edges of the system.
Flattened Milky Way ("grindstone")
Sun very near the center.

13. The Milky Way Galaxy IV 1901 thru 1922: Jacobus Kapteyn1
Used photographic star counts
Estimated distances statistically based on parallaxes & proper motions of nearby stars.
Neglected interstellar absorption of starlight.
Flattened disk 15 kpc across & 3 kpc thick with the Sun slightly
off center.

14. The Milky Way Galaxy V 1915 thru 1921: Harlow Shapley1
Harvard Astronomer
Noticed two facts about Globular Clusters:
Uniformly above & below the Milky Way.
Concentrated on the sky toward Sagittarius.
Observations:
Measured Globular Cluster distances from RR Lyrae stars
Mapped the cluster distribution in space.

15. The Milky Way Galaxy VI

16. The Milky Way Galaxy VII1
Shapley's Results
Globular clusters form a subsystem centered on the Milky Way.
The Sun is 16 kpc from the MW center.
MW is a flattened disk ~100 kpc across
Right basic result, but too big:
Shapley ignored interstellar absorption
Caused him to overestimate the distances.

17. The Milky Way Galaxy VIII1
The Problem of Absorption!
Absorption of Starlight by Interstellar Dust:
Interstellar space is filled with gas and dust
Dust absorbs/scatters light, making distant objects look fainter.
If left unaccounted for, it leads to overestimates of Luminosity distances.
Plagues all attempts to map the Milky Way:
Shapley & Kapteyn thought it was small.
Trumpler (1930) showed it was significant.

18. The Milky Way Galaxy VIIII1
Present Picture
Largely Shapley's model, corrected for the effects of interstellar absorption.
A flattened disk of stars with a central bulge.
~25 kpc in diameter and ~1 kpc thick
Sun is ~8 kpc from the center in Sagittarius
Galactic Center and much of the disk is obscured by dust in the plane of the Galaxy

19. The Milky Way Galaxy X3

20. Black Holes
A region of space-time from which nothing can escape, even light.5
It is impossible to see a black hole directly because no light can escape from them; they are black.5
If a neutron star is too large, the gravitational forces overwhelm the pressure gradients and a collapse cannot be halted. The neutron star continues to shrink until it finally becomes a black hole.5

21. Black Holes II Two Types Of Black Holes7
Non-rotating, spherically symmetric black hole, first postulated by Schwarzschild.
A rotating, spherical black hole, predicted in 1964 by the New Zealand mathematician Roy Kerr.
Schwarzschild Black Hole7
If you envision the simplest three-dimensional geometry for a black hole, that is a sphere (known as a Schwarzschild black hole), the black hole's surface is known as the event horizon.

22. Black Holes III

23. Black Holes IV
As we round the giant hot blue star, we see its tiny companion, a black hole whose gravity is so intense that it is stripping the outer layers of gas from the star.2

24. Supernovas
When a large star has burnt all its fuel it explodes into a supernova.5
The leftover material collapses down to an extremely dense object known as a neutron star.5
A supernova occurs in our galaxy once every 300 years, and in neighboring galaxies about 500 neutron stars have been identified.5

25. Supernovas II
The most recent event of this kind was observed in 1987 when a star weighing the equivalent of 20 suns blew up in a neighboring galaxy 160,000 light years away.7
If after such an explosion, the remaining material is greater than 1.4 solar masses, it will contract into an unimaginably dense core made solely of neutrons. Neutron stars are so dense a teaspoonful would weigh 100 million tons!7
If the star's final mass exceeds much beyond 2 solar masses, there is no outward force that can resist gravity. The core continues to collapse to a critical size or circumference beyond which there is only one fate: to form a black hole.7

26. Supernova III

27. Supernova Remnant Turns 400
This combined image -- from NASA's Spitzer Space Telescope, Hubble Space Telescope, and e Chandra X-ray Observatory -- unveils a bubble-shaped shroud of gas and dust that is 14 light-years wide and is expanding at 4 million miles per hour (2,000 kilometers per second).2

28. A Question 1 A galaxy is comprised of:
several million to some trillion stars.
several hundred stars.
several thousand stars.
several stars. A

29. C Question 2 We are part of the: Andromeda Galaxy. Papillon Galaxy.
Milky Way Galaxy.
Sombrero Galaxy. C

30. D Question 3 The most common type of galaxy is a/an: irregular galaxy.
lenticular.
elliptical.
spiral. D

31. D Question 4 A black hole is: impossible to see directly.
a region of space-time from which nothing can escape, even light.
a shrunken neutron star.
all of the above. D

32. A Question 5 The collapsed material from a supernova is known as:
a neutron star.
a black hole.
a planet.
useless crap. A

33. Question 6
When a large star has burnt all its fuel it explodes into a:
neutron star.
black hole.
supernova.
galaxy. C

34. C Question 7 A supernova occurs about once every: 3 million years.

35. Question 8
Did you like my cool pictures?
Yes!
All of the above. D

36. Works Cited
1- Introduction to Stars, Galaxies, & the Universe by Prof. Richard Pogge 2-
3- Galaxies
4- Types of Nebulae

37. Works Cited II 5- Introduction to Black Holes 6- Galaxies
6- Galaxies
7- A Black Hole is Born
8- The Hubble Tuning Fork