1. What makes up the Universe?

2. Planets and planetoids Planetary systems Stars and star systems
Subatomic particles
Atoms
Planets and planetoids
Planetary systems
Stars and star systems
Nebulas
Galaxies
Cluster
Supercluster
Review of previous lecture
Focus on galaxies, nebulas, stars, Solar System, planetoids

3. What is a galaxy? Galaxies are collections of stars
with a common gravitational center.
Shown in the background is an artist’s visualization of the predicted collision between Andromeda at left (largest galaxy in our cluster) and the Milky Way at right.
Andromeda and the Milky Way by Hubble Space Telescope.

4. There are 4 kinds of galaxies: Spiral Barred spiral Elliptical
Irregular
Background shows the Perseus cluster which contains over 500 galaxies.
Perseus cluster of galaxies. scienceblogs.com

5. Spiral galaxy – central bulge of old stars with arms of young stars
These galaxies are near the Virgo constellation and are on a collision course. Such collisions do not mean that the stars themselves actually hit each other (galaxies are mostly empty space, the distances between stars immense). But the gravitational forces tend to alter the shapes of the galaxies. (Imagine a giant washing machine in which the clothes themselves do not touch each other but their shapes are distorted by the tug and pull of the swirling water.)
Colliding spiral galaxies in Arp apod.nasa.gov

6. Barred spiral galaxy – central rod of old stars with arms of young stars
Our own galaxy, the Milky Way, is a barred spiral.
Hubble observes NGC

7. Elliptical galaxy – spherical cluster of mostly old stars
The central image is Messier 60, the 3rd brightest galaxy in the Virgo cluster (a cluster composed of ~1,300 galaxies). Messier 60 has a mass 1 trillion times that of the Sun. At its center is a black hole measuring 4.5 billion solar masses. (the millions of stars composing a galaxy is kept together by the powerful gravitational force of a black hole).
Odd galaxy couple on space voyage.

8. Irregular galaxy – no recognizable shape
Shown here is NGC 1569, a dwarf irregular galaxy (very small galaxies are called dwarves). Galaxies contain nebulas which may become centers of star birth (star clusters). This happens when nearby stars go supernova. The bright clusters of blue stars shown above are recently born.
Starburst in a dwarf irregular galaxy. apod.nasa.gov

9. What is a nebula? Nebulas are clouds of gas and dust.
They are the birthplace of stars and galaxies.
Shown in the background is the Carina Nebula, one of the largest regions of star birth ever seen. The “pillars” are hydrogen gasses rising up because of the energy released by newly born stars in their insides. The nebula is classified as a dark nebula (it is composed mainly of cold hydrogen gas that does not produce its own light).
Pillar and jets.

10. There are 4 kinds of nebulas: Emission Reflection Dark Planetary
Shown in the background is the Lagoon Nebula, an emission nebula.
Hubble’s lagoon. apod.nasa.gov

11. Emission nebula – produces its own light Emission nebula
The gas particles themselves produce light by rubbing each other: friction = heat = glow.
Shown here is the Trifid Nebula. It contains 3 kinds the most prominent is the red emission nebula; next, one can see at right of center the blue of a reflection nebula; the dark lanes separating the cloud into 3 (hence the name trifid) are dense dark nebulas.
Nebulas are rarely just one type- they often contain many types in one cloud.
Emission nebula – produces its own light
Emission nebula
A beautiful Trifid. apod.nasa.gov

12. Reflection nebula – reflects the light of neighboring stars
This cloud (known as IC 349) is close to the Pleiades Star Cluster on of whose stars, Merope (not shown in the image but it’s light rays are visible streaming from the upper right corner) is ‘blowing away’ the cloud. The energy released by a star is like a wind that affects nearby objects. In this instance, the cloud appears distorted by Merope’s stellar wind. The pillars or spikes pointing toward the starlight are more massive dust particles that are harder to blow away.
A pile of dust resting on your outstretched palm will look like this after a vigorous effort to blow it away.
Reflecting Merope. apod.nasa.gov

13. Dark nebula – blocks the light of stars behind it
Made of dense, cold and dark hydrogen gas, these clouds block the light from objects behind them. In this case, the Horsehead nebula blocks the light of the bright IC 434 nebula behind it.
Visible at the head’s crown is a newly born star.
Hubble observes the popular Horsehead nebula.

14. Planetary nebula – clouds of star material exhaled by a dying star
The dying star is shedding off its outer envelope of gases as it begins to collapse on itself. At the center of such a cloud is usually a white dwarf. Shown here is the ESO , a planetary nebula in the Sagittarius Constellaion (the Archer).
Hubble observes glowing, fiery shells of gas.

15. What is a star? Balls of hot gasses
Produce own light through nuclear fusion
A star is a ball of hot gasses that can produce their own light through nuclear fusion. Two atoms of hydrogen collide to form one atom of Helium and a burst of energy (don’t teach the difference between deuterium and tritium or the details of the nuclear reaction involved).
Andromeda and the Milky Way by Hubble Space Telescope.

16. There are 7 Star types: Oh Boy A Failing Grade Kills Me Hot Cold Young
Blue
Red
Small
Large
There may be stars in between but most stars fall into these 7 types.
Perseus cluster of galaxies. scienceblogs.com

17. www.cmso.info. Two types of life cycles:
For stars of the same size like our own (yellow dwarf), there is a quiet death to a white dwarf.
Bigger stars die in a spectacular explosion called a supernova. If the star is very large, it becomes a black hole. Smaller stars become neutron stars.
* There is no need to go into greater detail (that is for high school)

18. What is the Solar System?
The Solar System is the star system
which has Sol for its center.
There are other Solar Systems out there and the term “Solar System” is actually a proper noun. The common noun is star system. Our star system’s center is Sol, hence the proper name Solar System. To date, astronomers have discovered 50 plus other star systems near our own (in the Milky Way).

19. Where is our Solar System?
There are about 300 billion stars in our galaxy. And there at least 100 trillion galaxies in the Universe.
The Milky Way. popchassid.com

20. Parts of the Solar System Sol Inner planets Asteroid belt
Outer planets
Kuiper Belt
Oort Cloud
The Solar System is a flat disk surrounded by a shell of planetoids (the Oort Cloud). The plane on which the disk lies is called the ecliptic plane.
The Solar System. solarsystem.nasa.gov

21. Solar sytsem. spaceplace.nasa.gov
Shown here are the planets. Note the location of the asteroid belt, the inner planets, and the outer planets. Pluto, Makemake and Eris are three of the more popular KBOs (Kuiper Belt Objects).
Solar sytsem. spaceplace.nasa.gov

22. Inner planets – Rocky planets (Mercury, Venus, Earth, Mars)
Thin atmosphere
Thick, rocky layers
Metallic cores
These are also called Terran planets (Terra is the ancient name of Earth) because there structure is similar to Earth’s.

23. The Inner Planets. www.astronomy.ie
Pluto is shown for comparison.
The Inner Planets.

24. Outer planets – Gas giants (Jupiter, Saturn, Uranus)
Thick atmosphere
Thin rocky layers
Small metallic cores
They are also called Jovian planets since they are like Jupiter in structure.

25. The Outer Planets. www.astronomy.ie
Inner planets and Pluto shown for comparison.
The Outer Planets.

26. The Solar System. www.astronomy.ie
The Sun and the planets (Pluto shown for comparison).
The Solar System.

27. How do planets move?
Axial tilt
Rotation
Revolution

28. Axial tilt. en.wikipedia.org
Axial tilt is the N-S orientation of a planet. It determines its seasons. Earth and Venus have similar tilts, hence similar seasons (climate). Uranus on the other hand, is lying on its side so half the year is summer (when the North is facing the Sun).
Axial tilt. en.wikipedia.org

29. Rotating Earth. superiorplatform.com
Night and day occurs as a result of a planet’s rotational motion. The day part faces the Sun.
Rotating Earth. superiorplatform.com

30. Revolving planet. oncirculation.com
A year is one complete revolution. Planets with faster revolutions have shorter years.
Revolving planet. oncirculation.com

31. Solar System in motion. myweb.rollins.edu
A year is one complete revolution. Planets with faster revolutions have shorter years.
Solar System in motion. myweb.rollins.edu

32. What is a planetoid? A planetoid is a rocky body orbiting the Sun.
It is smaller than a planet.
Planetoids are also known as asteroids.

33. Asteroid belt – region filled with rocky bodies orbiting the Sun
Astronomers believe that the belt used to be occupied by a large rocky planet that was smashed into bits in the earlier stages of the Solar System’s birth. Earth and Jupiter are the only planets shown in the diagram.
The asteroid belt.

35. Kuiper belt – outer region of planetoids orbiting the Sun (includes Pluto)
Planetoids in the Kuiper Belt are called Kuiper Belt Objects (KBO). Some recently discovered ones are bigger than Pluto (the most famous planetoid that used to be a planet). In fact, there is one that astronomers are debating on whether to name as the 9th planet.
The Kuiper Belt. heasarc.nasa.gov

36. Oort Cloud – outermost group of planetoids forming a “shell” around the Sun
The Solar System is a flat disk surrounded by a shell of planetoids (the Oort Cloud). The plane on which the disk lies is called the ecliptic plane.
Shown here is the Oort Cloud surrounding the Solar System.
The Oort Cloud is the birthplace of comets.
The Oort Cloud. spaceplace.nasa.gov

37. What are comets? Orbit of a comet. www.nasa.gov
The Oort Cloud is the birthplace of comets. Usually, the planetoids in the cloud just drift along a circular orbit round Sol. Sometimes however, they bump into each other and when one of them gets knocked off course, then it starts moving towards the Sun in a very eccentric (highly elongated) orbit. A comet is born!
Orbit of a comet.

38. Comets. spaceplace.nasa.gov
A comet is a ball of rock and ice orbiting the Sun in a highly eccentric orbit.
A comet’s tail appears as it nears the Sun.
Comets. spaceplace.nasa.gov

39. Comet Lovejoy seen over Santiago de Chile
Comet Lovejoy seen over Santiago de Chile. It can be seen from Earth every 622 yrs (next sighting will be on the year 2633)
Comets. neo.ssa.esa.int