1. An Astronomer at the Mount Wilson Observatory in California.
Edwin Hubble
An Astronomer at the Mount Wilson Observatory in California.

2. The Milky Way Galaxy

3. Hubble Space Telescope
Named in Honor of Astronomer Edwin Hubble
Launch Date April 24, 1990
Mission Ends: ~2010
The size of a tractor-trailer
375 miles above Earth
Orbital period around Earth:
96-97 minutes

5. Edwin Hubble
In the 1920’s, Edwin Hubble discovered that what appeared to be “stars” from earth were actually galaxies.
Some nebulae, or large clouds of dust and gas, were actually discovered by Hubble to be galaxies beyond even our Milky Way.

6. Definition
A galaxy is a group of stars held together by gravity.

7. Classification Hubble classified galaxies according to their shape.
Elliptical
Spiral
Barred-spiral
Irregular

8. Elliptical Galaxies Old Little or No Gas or Dust Emit Radio Waves
Classified with the letter E
Sample Shapes…

11. The brightest object is NGC 4881, an elliptical galaxy in the outskirts of the Coma Cluster (a great cluster of galaxies).

12. Spiral Galaxies Have Young, Hot Stars Have a lot of Gas & Dust
Arms spiral out from the center
Classified with the letter S
Spiral Galaxy NGC 4414
The Key Project team used this view of the spiral galaxy to help calculate the expansion rate of the universe.
They were also able to calculate the distance to this galaxy (~60 million light-years).

14. The Whirlpool Galaxy

16. Clusters of infant stars formed a ring around the core of the barred-spiral galaxy NGC 4314.
This stellar nursery is the only lace in the entire galaxy where new stars are being born.

17. Spiral Galaxy NGC 7742

18. Here are two spiral galaxies
Here are two spiral galaxies. The larger galaxy, NGC 2207, is on the left; the smaller one, IC 2163 is on the right.
Strong gravitational forces from NGC 2207 have distorted the shape of the smaller galaxy.
Someday, these two galaxies will become one.

19. Barred-Spiral Galaxies
Central bar shape, made of stars
Arms spiral out from the elongated center
Classified with the letters SB
The Milky Way galaxy is an example of a barred-spiral galaxy

20. Irregular Galaxies These Galaxies Have No Dominant Shape
No rotational symmetry
Tend to be Patchy
Classified with the letter I
This is a picture of two galaxies, called the Antennae.

21. Cartwheel Galaxy – located 500 million light-years from Earth in the constellation Sculptor.
The ring-like feature is a direct result of a smaller intruder galaxy that careened through the core of the host galaxy.
Like a rock tossed into a lake, the collision sent a ripple of energy into space, plowing gas & dust in front of it.
Expanding at 200,000mph, this cosmic tsunami leaves in its wake a firestorm of new star creation.

22. Hubble’s Law
Hubble discovered that all galaxies are receding from the Earth with velocities that increase in proportion to their distance from us.
This discovery showed that the universe is expanding. Hubble proved Einstein right!

23. Farthest Known Galaxy
An international team of astronomers may have set a new record iin discovering what is the most distant known galaxy in the universe.
Located an estimated 13 billion light-years away.
This galaxy was identified by combining the power of NASA’s Hubble Space Telescope & CARA’s W. M. Keck Telescopes on Mauna Kea in Hawaii. These telescopes were aided by a natural lens…
Galaxy cluster Abell 2218 is acting as a powerful lens, magnifying all galaxies lying behind the cluster core. The lensed galaxies are all stretched along the cluster’s center and some of them are multiply imaged. Those multiple images usually appear as a pair of images with a third – generally fainter – counter image, as is the case for the very distant object.
The color of the lensed galaxies is a function of their distances and types. The orange arc is an elliptical galaxy, the blue arcs are star-forming galaxies, and the encircled very red air is the newly discovered star-forming galaxy.

24. The Eagle Nebula

25. Photo Credits All Images taken from:

26. Andromeda Galaxy
The largest visible galaxy (200,000 ly in diameter), Andromeda has the most stars of any local group galaxy, about 300 billion compared with our 200 billion stars.

27. Strange Galaxies
The Sombrero Galaxy

28. What types of galaxies can you see in this Hubble mosaic?

29. Major Types of Galaxies
Most galaxies are spiral, elliptical (giant or dwarf), or irregular galaxies. At right is the Large Magellanic Cloud, an irregular galaxy orbiting the Milky Way.

30. Strange Galaxies
Some galaxies are difficult to classify, like the Ring Galaxy, which is an odd spiral. The Sombrero Galaxy is a normal spiral, but looks odd in our side view. Some strange galaxies are the result of collisions with other galaxies. These collisions don’t mean stars hit one another…they just get mixed up.