Astronomy

Since the beginning of time, astronomers have attempted to study

the movements of the stars and planets.

                                        

Long, long ago…• Ptolemy thought the

Earth was the center of the universe.

• This was considered the geocentric way of thought.

• Ptolemy also thought that we were not moving.

Helio---what?

• In 1500 AD, Copernicus said the Sun was the center of the universe (heliocentric viewpoint).

• Copernicus also said that the planets were orbiting in a circular pattern.

• In 1609, Kepler proved Copernicus was wrong about the orbits. The planets orbit in an elliptical pattern instead of a circular pattern.

• Galileo proved that Copernicus was right about the Sun being the center of the our solar system.

• Galileo created a telescope that allowed him to prove these theories.

Ptolemy’s geocentric view…• The Church supported

this view and did not support future views of Copernicus, Kepler, and Galileo.

• Galileo was even put under house arrest for his findings.

Sunspots and Moons

• Galileo observed the Sun through his telescope and saw that the Sun had dark patches on it that we now call sunspots (he eventually went blind, perhaps from damage suffered by looking at the Sun with his telescope). He saw these spots moving, so he realized that the Sun must be rotating. He thought that if the Sun was moving, we probably were rotating on an axis.

• Galileo observed 4 points of light that changed their positions with time around the planet Jupiter. He concluded that these were objects in orbit around Jupiter. Indeed, they were the 4 brightest moons of Jupiter, which are now commonly called the Galilean moons (Galileo himself called them the “Medician Stars”).

The Phases of Venus• Galileo used his telescope to show that Venus went

through a complete set of phases, just like the Moon. This was probably the most important observation that Galileo made, because this proved that Venus was revolving around the Sun.

• In the old system of thinking, Venus should always be in crescent phase as viewed from the Earth. In the Copernican system, Venus should exhibit a complete set of phases as viewed from the Earth because it is illuminated from the center of its orbit.

What else Galileo saw…

• Galileo saw that the planets were disks, not points of light, as seen through the telescope.

• He saw that the great "cloud" called the Milky Way (which we now know to be the disk of our spiral galaxy) was composed of enormous numbers of stars that had not been seen before.

• He observed that the planet Saturn had "ears". We now know that Galileo was observing the rings of Saturn, but his telescope was not good enough to show them as more than extensions on either side of the planet.

• Galileo saw that the Moon was not smooth, as had been assumed, but was covered by mountains and craters.

Stuff in space…

• Asteroids are chunks of rock and metal that are commonly found in a belt between Mars and Jupiter.

• Meteoroids are smaller than asteroids.

• What do you call a meteoroid that falls to the Earth?

• It is a meteorite.

• Comets are frozen balls of gas, rock, and ice.

• Why do comets have a tail when they are near the Sun? They are melting.

How many planets have we found?

• This latest discovery (May 2015) brings the confirmed count of planets outside our solar system to 1,021.

• Most of these planets are smaller than Neptune, which is almost four times the size of Earth.

• Launched in March 2009, Kepler is the first NASA mission to find potentially habitable Earth-size planets. Discoveries include more than 4,600 planet candidates.

Kepler is actually a special type of telescope housed on a spacecraft…

Planets in our system:• My very excellent mother just served us nachos.• Name the planets of our galaxy, in order.

Dwarf planets include: Ceres, Eris, Haumea, Makemake, and

Pluto• Eris is just slightly larger than

Pluto and takes 557 years to make a very skewed orbit of the Sun. Ceres is between Mars and Jupiter. Two other dwarf planets include Haumea and Makemake.

• The new definition of "planet": A body that circles the sun without being some other object's satellite, is large enough to be rounded by its own gravity (but not so big that it begins to undergo nuclear fusion, like a star) and has "cleared its neighborhood" of most other orbiting bodies.

This artist's concept shows dwarf planets Eris, Pluto and Ceres in comparison to Earth. Pluto's moon Charon also is shown.

Galileo mission

• http://solarsystem.nasa.gov/galileo/

Go to sizes of planets…• Astronomers are searching for a planet similar to Earth, with water (so that it could

support life). • Two methods to detect planets are commonly used: the wobble method and the transit

method.• The wobble method is based on planets that are as massive as Jupiter. Massive planets

pull on their stars, making them wobble like a large dog who walks its owner. You can often tell that a dog is walking it’s owner without seeing the dog, as you watch the person being pulled this way and that. This is how scientists detect massive planet that are far away. They look for stars that are wobbling. The less massive planets do not produce such a visible pull on their stars, however, so another method is used.

• The transit method looks for stars that are smaller than our Sun (red dwarfs). As a smaller (less massive) planet passes in front of the star, it causes a brief dimness of the star due to the eclipse or transit of the planet. We can detect a less massive planet passing in front of a less massive star from far away. NASA has launched the Kepler telescope just to search for transit planets (launched in 2009). http://www.kepler.arc.nasa.gov/http://www.kepler.arc.nasa.gov/

Rotate means to spin on the axis.• A planet’s rotation

time may vary, so the length of a day will vary too.

• Venus’ rotation time is much slower than ours, so the days are longer there.

Seasons are caused by…?

• Seasons are caused by the Earth’s tilt on its axis.

• March 21 marks our Vernal Equinox.

• June 21 is the beginning of our Summer Solstice (most daylight hours in Northern Hemisphere).

• Sept 23 marks our Autumnal Equinox and Dec 22 marks our Winter Solstice.

So, are the seasons the same in both the Northernand Southern Hemispheres?

No seasons???• Mercury, Venus,and Jupiter

have no axial tilt, so they also have no seasons.

• Mars has colder winters and warmer summers than Earth.

• Distance from the Sun can also determine seasons. (Pluto has cold and colder weather; Uranus has years of day and years of night due to its tilt.

How long is a day on Venus?

• Try going to Venus for a day; you could get everything and more done in one day!

• One day on Venus is equal to 243 Earth days.

• Why?

What causes a year?

• A revolution is the movement of a planet all the way around the Sun.

Phases of the moon

• The Sun’s light is reflected off the moon in phases due to the moon’s rotation.

• Waxing phases are the ones you see as the moon goes to the Full Moon phase.

• Waning phases are the ones you see as the moon goes to the New Moon phase.

• http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level2/moonlight.html

• WAX ON (karate kid) means there is more (more wax); to wane is to get smaller.

What an awesome wave, dude!

• The gravitational pull of the moon and the Earth, and the difference between those two forces cause the tides.

• The net force can be seen in the diagram, which causes the squashed appearance.

I can’t see you…

In a lunar eclipse, what can’t you see?• The Earth blocks our view of the

moon.• The next total lunar eclipse that will

be visible from North America will be on September 28, 2015.

• Eclipses in 2016March 9: Total solar eclipseMarch 23: Penumbral lunar eclipseSeptember 1: Annular solar eclipseSeptember 16: penumbral lunar eclipse

• .

How far is it to the closest star?• One astronomical unit

is 93,000,000 miles.• This is the distance

from the Earth to the Sun.

How far is that star…?• One light year is about 5.8

trillion miles.

• A light year is the distance that light can travel in a vacuum in a year.

• What is a vacuum?

• Proxima Centauri is the next closest star to Earth.

• Four point two light years away means that you are seeing the way it looked 4.2 light years ago. (5.8 trillion times 4.2). (one trillion = 1 one and 12 zeros)

From baby star to old star…

• Stars have stages of growth just like we do.

• Newborn stars are called Nebula.

• Being a star is all about the race between gravity and burning of gases (hydrogen and helium).

You’re a protostar!

• The second stage of a star is called a protostar.

• During this stage, the pressure causes the temperature to rise to 27 million degrees F, high enough for fusion to begin.

Main sequence star• In the third stage, the

hydrogen of the star is turned into helium in a process called fusion.

• This gives the star energy.

• As the hydrogen runs out, so does the star.

• This takes millions or billions of years, depending on the mass of the star.

• Our Sun is in this stage.

What’s your mass anyway?

• Low mass stars will become white dwarfs. Our Sun will become a white dwarf.

• Medium mass stars will become red giants, planetary nebulas, and then white dwarfs.

• High mass stars will become supergiants, supernovas, and black holes or neutron stars.

Go to star sizes…

• Twinkle, twinkle little star• You’re a ball of gas that’s very far.• Thirty two light years in the sky.• Ten parsecs (32.6 light years) which is really high.• Helium, carbon, and hy-dro-gen,• Fuse to make our starry friend.• When it enters supernova stage, it explodes with

burst of rays.• And if the star’s mass is big and bold, it will

become a black hole!

How can we find a star?• Stars give off

electromagnetic radiation---radio waves, infrared rays, visible light, UV waves, x rays and gamma rays.

• Astronomers can now detect a type of star by the type of radiation it gives off.

Radio telescopes help astronomers detect waves from space.

GBT in Pocahontas County, WV

I can’t see you…

• In a solar eclipse, the moon blocks our view of the Sun. Our next partial solar eclipse will be on Oct 23, 2014.

Welcome to my galaxy…

• Edwin Hubble was an astronomer in the 1920’s who discovered that galaxies are moving and that the universe is expanding.

• The Hubble telescope is used in space today, and will be replaced by the Webb telescope in the near future.

Galaxies are classified by various shapes.

• They may be spirals, barred spirals, lenticular, ellipticals or irregular clusters.

The Milky Way is a spiral galaxy.

• Our next closest galaxy is Andromeda, yet it is twice the size of our galaxy.

• There are billions of galaxies in space; each galaxy contains hundreds of thousands of stars.

Galaxies are never alone.

• They are usually connected with other galaxies by gravity.

• Clusters of galaxies can be as small as two galaxies orbiting each other.

• There is no end to the amount of galaxies in a cluster. A view from within the

Milky Way Galaxy.

Our universe…

• The Milky Way galaxy is part of a cluster called the local group, which includes 40 different galaxies.

• The local group is part of a super cluster called the Virgo Cluster, which contains over 2,000 galaxies.

The International Space Station

• The station, built by 5 different groups, is about 361 feet across (a football field). http://www.youtube.com/watch?v=0OxoEnzAhFg&list=PLiuUQ9asub3RHqKdK_XZSZ8I_981UPhvX&index=3