Lesson Review Complete the table by placing a check mark in the correct column. multicolumn(1)(|c|)( TYPES OF GALAXIES ) & Irregular galaxy & Spiral galaxy multicolumn(1)(|c|)( Characteristic ) & & 1. Rounded & & 2. No definite shape & & 3. Thick center and flattened arms & & 4. Made up of billions of stars & & 5. Least common type of galaxy & & 6. Contains the oldest stars & & 7. One typed is barred & & 8. Smaller and fainter than other types of galaxies & & 9. Main features of the universe & & 10. Has a nucleus made up of bright stars & & 11. Milky Way is one & &

# Explanation<br />Galaxies are massive systems composed of stars, stellar remnants, interstellar gas, dust, and dark matter, all bound together by gravity. They are fundamental to our understanding of the universe's structure and evolution. Galaxies come in various shapes and sizes, typically classified into three main types: elliptical, spiral, and irregular.<br /><br />Elliptical galaxies (E) are characterized by their rounded, elliptical shape. They typically have a smooth, featureless light distribution and contain older, redder stars. They lack the distinct spiral arms found in spiral galaxies and do not have much interstellar gas or dust, which means they have low rates of star formation.<br /><br />Spiral galaxies (S) have a flat, disk-like shape with a bulging central nucleus and multiple spiral arms extending from the nucleus. The Milky Way, our home galaxy, is an example of a spiral galaxy. Spiral galaxies contain both old and young stars, with active star formation occurring in their spiral arms.<br /><br />Irregular galaxies (I) do not have a definite shape like elliptical or spiral galaxies. They are often chaotic in appearance, with neither a nuclear bulge nor spiral arms. Irregular galaxies may contain abundant gas and dust and often experience intense star formation.<br /><br />Now, let's complete the table based on these characteristics:<br /><br />1. Rounded: This is a characteristic of elliptical galaxies.<br />2. No definite shape: This applies to irregular galaxies.<br />3. Thick center and flattened arms: This describes spiral galaxies.<br />4. Made up of billions of stars: All types of galaxies have this characteristic.<br />5. Least common type of galaxy: This could vary, but elliptical galaxies are often considered less numerous than spiral galaxies.<br />6. Contains the oldest stars: Elliptical galaxies typically contain older stars.<br />7. One type is barred: This refers to a subtype of spiral galaxies known as barred spiral galaxies.<br />8. Smaller and fainter than other types of galaxies: This can apply to dwarf elliptical galaxies, which are a subset of elliptical galaxies.<br />9. Main features of the universe: All galaxies are main features of the universe.<br />10. Has a nucleus made up of bright stars: This is a characteristic of spiral galaxies.<br />11. Milky Way is one: The Milky Way is a spiral galaxy.<br /><br /># Answer<br />\begin{array}{|c|c|c|c|}<br\ />\hline\ \multicolumn{4}{|c|}{TYPES\ OF\ GALAXIES}\ \\<br\ />\hline\ Characteristic\ &\ Elliptical\ galaxy\ &\ Spiral\ galaxy\ &\ Irregular\ galaxy\ \\<br\ />\hline\ 1.\ Rounded\ &\ \checkmark\ &\ &\ \\<br\ />\hline\ 2.\ No\ definite\ shape\ &\ &\ &\ \checkmark\ \\<br\ />\hline\ 3.\ Thick\ center\ and\ flattened\ arms\ &\ &\ \checkmark\ &\ \\<br\ />\hline\ 4.\ Made\ up\ of\ billions\ of\ stars\ &\ \checkmark\ &\ \checkmark\ &\ \checkmark\ \\<br\ />\hline\ 5.\ Least\ common\ type\ of\ galaxy\ &\ &\ &\ \\<br\ />\hline\ 6.\ Contains\ the\ oldest\ stars\ &\ \checkmark\ &\ &\ \\<br\ />\hline\ 7.\ One\ type\ is\ barred\ &\ &\ \checkmark\ &\ \\<br\ />\hline\ 8.\ Smaller\ and\ fainter\ than\ other\ types\ of\ galaxies\ &\ \checkmark\ &\ &\ \\<br\ />\hline\ 9.\ Main\ features\ of\ the\ universe\ &\ \checkmark\ &\ \checkmark\ &\ \checkmark\ \\<br\ />\hline\ 10.\ Has\ a\ nucleus\ made\ up\ of\ bright\ stars\ &\ &\ \checkmark\ &\ \\<br\ />\hline\ 11.\ Milky\ Way\ is\ one\ &\ &\ \checkmark\ &\ \\<br\ />\hline<br\ />\end{array}