Exploring the Universe, Galaxies

What were some things you noticed about the cards you sorted yesterday? How were the cards from yesterday different from the cards last week when we looked at Solar System objects? Discuss at your table.

Look at your cards and again sort them by their distances. Quickly place them in the same categories.

What cards are less than one light year away? 3 cards: #2, #31, #36 What are these objects? Comets Everything in the Solar System is located within approximately one light year from Earth.

Find the cards that are in this distance. Only cards #2, #31, #36 are the only cards categorized within one light year away. That means that all other cards are located outside our Solar System. What cards are between 1 to 100,000 light years away? 21 cards, #’s 1, 3, 6, 7, 8, 9, 10, 11, 12, 15, 17, 19, 22, 23, 26, 27, 28, 29, 32, 33, and 34. These objects are outside our Solar System, but within our galaxy, The Milky Way. One of BILLIONS. A galaxy is a huge collection of stars, gas, and dust-all bound together by gravity.

What cards fit into this category? Just one 5 There is a large area of space surrounding our galaxy. About a dozen small galaxies lie in this area. They are mostly satellites of the Milky Way All other galaxies besides the Milky Way are further away.

What cards fit into this category? 11 cards: #’s 4, 13, 14, 16, 18, 20, 21, 24, 25, 30, and 35. These are all galaxies. Each galaxy is like a cosmic island of stars and other objects, surrounded by and separated from other galaxies by vast stretches of space. Objects we find in our galaxy are like the objects that make up these distant galaxies.

The dot in the center is us. The dots around us are the billions of stars in our galaxy, outside our solar system. Between 100,000 and 1,000,000 light years away are no other large galaxies like ours, but there are a few small galaxies. Other large galaxies would be more than a meter away. The next closest galaxy is actually 2.5 meters away, about 2.5 million light years.

Our Solar system and billions of other stars make up or galaxy, the Milky Way. The Milky Way and billions of other galaxies are in the universe. Large distances in space separate objects in the Universe.

Now we will be looking at only galaxies. Put the rest of the cards away and keep out card #’s 4, 13, 14, 16, 18, 20, 21, 24, 25, 30, 35. Lay them out on your table for the whole group to see.

Galaxy names come from different sources. In the past, names came from those who found them. Today, they are given a number based on the catalog they are found in. Think back to Messier. Card #4 is called M31 because it is #31 in the Messier catalog. It is also known The Andromeda Galaxy. Some galaxies are descriptive. Can you find Whirlpool #13 Black eye #16 Sombrero #20 Antennae #24, this is actually a pair of merging galaxies

Galaxies are huge collections of stars, gas and dust-all held together by gravity. A typical galaxy will have billions of stars. What categories should we use to sort our galaxies? Discuss

Spiral: Have a main core of stars, with branches (or arms) of dust, gas, and stars spiraling outward from its core. The Milky Way is a spiral galaxy. Card #’s 4, 13, 16, 20, 21 and 30.

Elliptical: Basically football-shaped arrangements of stars with very little visible dusty material. Card #18 is an example.

Irregular: Can not be categorized as either elliptical or spiral. Card #14 is an irregular galaxy Card #24 shows a pair of merging galaxies that have not been classified.

Space Science Sequence 6–8 © 2008 The Regents of the University of California Permission granted to purchaser to photocopy for classroom use.

The image was taken by The Hubble Space Telescope. It is called an Ultra Deep Field because it gives one of the deepest or farthest looks into space ever seen (as of 2007) The galaxies in this image are even further away than in the cards you sorted. Most of these galaxies are over 100 times further away.

The Hubble Space Telescope also know as HST is the best instrument scientists have for seeing the farthest and faintest objects in the Universe with the best detail. The HST orbits above Earth’s atmosphere at about 500 km. Because of this, it does not experience atmospheric interference as do ground based telescopes on earth. The HST obtained the Ultra Deep Field image by collecting light from a small portion of the sky for about a million seconds. (About 11 days) It was pointed at a place with few Milky Way stars. Most of the objects seen in this image are galaxies. This image represents a very small portion of the sky.

Light is the primary tool available to gather evidence about distant objects. Scientists analyze the light coming from these distant objects to learn more about them. The Hubble Ultra Deep Field shows us objects that are billions of light years away. Don’t forget that a light year is the distance a light is able to travel in one year. That means that the image shows what the objects looked like billions of years ago when light first left the objects.

The light coming to us from a distant object shows us how that object appeared in the past, when the light first left it. The more distant an object, the longer it takes light from that object to reach us, and the farther back in time we ae looking into the universe’s past.

Space Science Sequence 6–8 © 2008 The Regents of the University of California Permission granted to purchaser to photocopy for classroom use.

The tiny square you see covers about the same amount of sky as shown in the picture. It would take about 13 million squares like this to cover the sky. Some of the images you see are stars. We will try not to count these. Stars will appear to have four points because of the way the light bends when it gets to a telescope. The pictures are divided into grids. What grids contain stars? 2 in B1 1 in c4 1 on the border of c2 and c3 Can you see any galaxy types like elliptical or spiral?

Each team of two will count all the galaxies in their one square on the grid. Use a ruler to mark your grid. Assume every speck is a galaxy unless it is a star. We will average or results and get a total for this image. Remember, our image only covers 1/13,000,000 of the entire sky. We have to take our class total and multiply by 13,000,000! Could our estimate be off? Why?

5IU