Stars Galaxies the Electromagnetic Spectrum Electromagnetic Waves n

Stars, Galaxies & the Electromagnetic Spectrum

Electromagnetic Waves n n Produced by the movement of electrically charged particles Can travel in a “vacuum” (they do NOT need a medium). This is why you can see the Sun and stars-their light reaches Earth through the vacuum of space. Travel at the speed of light Also known as EM waves

The Electromagnetic Spectrum includes radio waves, infrared waves, visible light, ultraviolet rays, X-rays and gamma rays n The only waves in the spectrum that we can see are visible light waves; all other waves are invisible to us but are all around us all the time. n n n Light can behave like a wave or like a particle. A “particle” of light is called a photon.

Low frequency High frequency

Radio Waves n n Longest wavelength EM waves Uses: TV broadcasting n AM and FM broadcast radio n Avalanche beacons n Heart rate monitors n Cell phone communication n

Microwaves n n Wavelengths from 1 mm- 1 m Uses: Microwave ovens n Bluetooth headsets n Broadband Wireless Internet n Radar n GPS n

Infrared Radiation n n Wavelengths in between microwaves and visible light Uses: Night vision goggles n Remote controls n Heat-seeking missiles n

Visible Light n n n Only type of EM waves able to be detected by the human eye Red light is the lowest frequency light Violet is the highest frequency light

Ultraviolet n n Shorter wavelengths than visible light Uses: Black lights n Sterilizing medical equipment n Water disinfection n Security images on money n

X-rays n n Tiny wavelength, high energy waves Uses: Medical imaging n Airport security n Inspecting industrial welds n

Gamma Rays n n Smallest wavelengths, highest energy EM waves Uses Food irradiation n Cancer treatment n Treating wood flooring n

Telescopes n n Telescopes are instruments that allow us to view distant objects. They use forms of energy in the electromagnetic spectrum to view these objects.

Using the Electromagnetic Spectrum in Space (3: 02)

Refracting Telescopes n n n Refracting telescopes use a curved lens to gather and focus light. This convex lens is a piece of transparent glass, curved so the middle is thicker than the edges. Draw and label the refracting telescope in fig. 2 on page 710 of the

Reflecting Telescopes n n n The first reflecting telescope was built by Isaac Newton in 1668. A reflecting telescope uses a curved mirror to collect and focus light. The larger the mirror, the more light the telescope can collect. The largest telescopes are reflecting telescopes. Draw and label the reflecting telescope in fig. 2 on page 710

Radio Telescopes n n Devices used to detect radio waves from objects in space. Most have curved, reflective surfaces that focus radio waves the way reflecting telescopes focus light. The larger the radio telescope the more radio waves it can collect. n Other types of telescopes collect the shorter waves such as gamma rays, X-rays, and ultraviolet n

Observatories n n n A building that contains one or more telescopes. However, some observatories are located in space. One of the best observatory sites on Earth is on the top of Mauna Kea, a dormant volcano, on the Island of

Advanced Telescopes n n Many large optical telescopes are equipped with systems that improve the quality of their images. Some are equipped with computers for automatic adjustments, and lasers.

Telescopes in Space n n n The Hubble Telescope is a reflecting telescope with a mirror 2. 4 meters in diameter. Because it orbits Earth above the atmosphere, it can produce very detailed images. Hubble images have changed how astronomers view the universe. The most recent addition to NASA’s lineup of telescopes in space is the Spritzer Space Telescope launched in 2003. It produces images in the infrared portion of

Images from the Hubble Telescope

Measurement in Space n Parallax: apparent shift in the position of an object when viewed from two different locations n Measures the distance of stars from Earth that are relatively close n Light Years: unit of measurement for large distances in space n Distance light travels in 1 year n Light travels 300, 000 km/s or 9. 5 trillion km /year n Proxima Centauri: closest star to Earth (other than the Sun)

Let’s compare the sizes of planets, stars and galaxies!!! n http: //www. cleanvideosearch. co m/media/action/yt/watch? v=HE heh 1 BH 34 Q

Relative Sizes of Stars

Proxima Centauri (0: 47)

Nebula n Large cloud of gas, plasma, and dust within a galaxy n n Typically a few lightyears wide Two types: Diffuse nebula n Planetary nebula n

Diffuse Nebula n Gas and dust particles are spread out and irregular n Provides the raw materials that will form new stars ØA star is born by fusion of hydrogen at 10 million K q K→ Kelvin→ º above zero

Planetary Nebula n n Forms when a star dies and throws off some of its outer material to form a cloud of gas, dust, and plasma Does not contain enough material to create a new star

Life Cycle of Stars Video (2: 17)

Life Cycle of a Star n Main sequence star: hydrogen fueled star Makes up about 90% of stars n Our Sun is a main sequence n Two types n n Low mass – remains a main sequence star longer and are smaller in size n High mass – goes through main sequence much faster and are much larger in size

Life Cycle of a Low Mass Star n Giants: fueled by helium from a low mass star n Outer layers are cool and expands with a carbon core Planetary nebula: occurs as the core collapses on itself and shells of gas are thrown outward n White dwarf: outer layer of gases escapes into space, core contracts leaving a hot dense small star n

Life Cycle of a High Mass Star n Super giant: fueled by helium from a high mass star n n Outer layers cool and expands with an iron core Super nova: iron core collapses and the star explodes n n Neutron star: collapsed core of a super giant with extremely high density Black hole: tremendously big supernova that collapses to a point of no volume

Neutron Stars and Black Holes ( 2: 43)

Brightness of Stars. Apparent Brightness n n Apparent brightness- how bright a star seems as seen from Earth due to its distance from Earth Can’t be used to tell how much light a star actually gives off. Just as a flashlight looks brighter the closer it is to you, a star will look brighter the closer it is to Earth. Our Sun looks bright just because it is close.

Brightness of Stars. Absolute Brightness n n Absolute brightness- the brightness the star would have if it were a standard distance from Earth The brightness of stars can vary tremendously. The brightest stars are more than a billion times brighter than the dimmest stars! Use a flow chart to show the cycle of a star. See pages 728 -729 of the science textbook.

The Color of Stars (1: 56)

Galaxies huge collection of stars, gas, & dust n Galactic cluster: a group of gravitationally bound galaxies--n n They are the largest gravitationally bound celestial bodies in the universe.

Three Types of Galaxies n Elliptical n Spiral n Irregular

Galaxies (1: 39)

Elliptical n Range from spherical to elliptical No typical size or brightness n Contains old, cool, red stars and small amounts of gas and dust, so no new stars are forming n Most common type n

Spiral n stars arranged in two or more spiral arms Ex. Milky Way and Andromeda n New blue stars form in the arms n Center is often a bulging disk of older red stars n Barred spiral: sub-group with a vast straight bar of stars lying across the center with a spiral arm at n

Irregular n lack regular pattern and shape, and are small and faint n Mixture of young and old stars with lots of gas and dust for new star formation

The Structure of the Milky Way (4: 34)

Our Galaxy - The Milky Way n Normal Spiral About 100, 000 light-years in diameter n Contains between 200 billion & 400 billion stars n About 14 billion years old n 3 basic parts: n Bulge n Disk n Halo n

Central Bulge n n n Core of the galaxy made mostly of older stars Small amounts of gas and dust Very little star formation

Disk Flattened area containing the spiral arms that are pinwheeled shaped n Contains lots of gas and dust with younger stars n Our solar system is located on the Orion Arm 25, 000 lightn

Halo n n Sphere of gas and stars surrounding the central bulge and disk Thought to be 100’s of thousands of light-years across Oldest stars in the galaxy Dark matter: does not produce or reflect light • Has a gravitational effect that can be detected • Believed to be the most common material in the Milky Way

Dark Matter Video (0. 42)

What is the Big Bang Theory? n n n Astronomers theorize the universe began billions of years ago. At that time, the part of the universe we can see was no larger than a period at the end of sentence. According to the big bang theory, the universe formed in an instant, in an enormous explosion.

Moving Galaxies n n In 1920, Edwin Hubble studied the spectrums of many galaxies and determined they were moving away from us indicating the universe is expanding. Hubble found a relationship between the distance to a galaxy and its speed. Hubble’s Law states the farther away a galaxy is the faster it is moving away from us. Hubble’s Law strongly supports the big bang

Cosmic Background Radiation n n In 1965, two American physicist accidently detected faint radiation on their radio telescope. Scientists later determined this was left over thermal radiation from the big bang. This would have been distributed in all directions at the big bang. If astronomers can approximate how fast the universe is expanding, they can infer how old the universe is. Astronomers estimate the universe to be about 14 to 17 billion years old.