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Galaxies and Stars

Galaxies and Stars. Galaxies. Galaxies are collects of millions, billion, and even trillions of stars bound together by Gravity. We live in the Milky Way Galaxy. We’re located about midway between the galaxy’s edge and its center. There are three types of galaxies based on their shape.

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Galaxies and Stars

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  1. Galaxies and Stars

  2. Galaxies • Galaxies are collects of millions, billion, and even trillions of stars bound together byGravity. • We live in the Milky Way Galaxy. We’re located about midway between the galaxy’s edge and its center. • There are three types of galaxies based on their shape.

  3. Spiral Galaxies • Spiral galaxies usually have arms that contain gas and dust. It has a bluish-tint and disk shape, Since new stars have a bluish tint. The gas and dust is essential for new star formation. • Spiral galaxies are younger galaxies.

  4. The Milky Way A view of the Milky Way from the southern hemisphere - towards the centre of our galaxy

  5. Elliptical Galaxies • Spherical or egg shaped galaxies. They are similar to the bulge in a spiral galaxies but with no disk. The stars are old and little gas and dust is present. • These are older galaxies. Giant Elliptical Galaxies M87

  6. Irregular Galaxies • Irregular galaxies are small with no bulge and an ill-defined shape. • Contain little gas and dust—no new stars are formed. Large Magellenic Cloud AAO

  7. Star TypesSUPER GIANTS • Super Giants are extremely large stars that create elements as heavy as iron. • Stars 1.4 times the mass of the sun become super giants. • Because of their size, these stars produce successively heavier elements until their cores become iron. • The formation of the iron core signals the beginnings of its violent death.

  8. Red Giants are large reddish stars late in their life cycle. In their cores, Red Giants fuse helium into carbon and oxygen. While the outer layers are cool, the core will reach high temperatures. White Dwarfs are small very dense stars that remain after fusion in a red giant stops. The remaining core becomes the white dwarf. A dim ember about the size of Earth but extremely dense. The dwarf sun will slowly cool, producing no more energy until eventually it becomes a black dwarf. Red Giants and White Dwarfs

  9. As Earth's Sun is of one solar mass, it is expected to become a red giant in about five billion years. It will become sufficiently large to engulf the current orbits of some of the solar system's inner planets, possibly including Earth's]. The gravitational pull of the Sun will have weakened by then due to its loss of mass, and it is possible that Earth may escape to a wider orbit . The fate of the Earth with regard to the size of the expanding Sun is still hotly debated in the scientific community. Mercury and Venus will almost certainly be swallowed up by the Sun when it turns into a red giant.

  10. White Dwarf

  11. Super Nova • A powerful explosion that occurs when a massive star dies. • When fusion stops, there is no longer any outward pressure to balance the gravitational force. • The star’s core collapses, and then rebounds with shock waves that blow the star’s outer layers away from the core. fusedweb.pppl.gov/.../5.Plasmas/ Graphics/Sun/Layers. if

  12. If the core of a super nova has a mass of 1.3 – 3.0 times that of the sun, it can become a neutron star. Neutron stars are only a few kilometers in diameter but are very massive. If the core after a super nova has a mass greater than 3 times that of the sun, it will collapse to form an even stranger object—a black hole. A black hole consists of matter so massive and compressed that nothing, not even light can escape its gravity. Black holes have a powerful gravitational influence on objects around them. Neutron Stars and Black Holes

  13. Feasting Black Hole Blows Bubbles • A monstrous black hole's rude table manners include blowing huge bubbles of hot gas into space. At least, that's the gustatory practice followed by the supermassive black hole residing in the hub of the nearby galaxy NGC 4438. The other bubble, emanating from below the dust band, is barely visible, appearing as dim red blobs in the close-up picture of the galaxy's hub (the colorful picture at right).

  14. A Black Hole

  15. THE DEATH OF SUN-LIKE STARS(with a mass up to 1 1/2 times that of the Sun)

  16. THE DEATH OF HUGE STARS(from 1.5 to 3 times the mass of the Sun)

  17. THE DEATH OF GIANT STARS

  18. In this stunning picture of the giant galactic nebula NGC 3603, the Hubble telescope's crisp resolution captures various stages of the life cycle of stars in one single view. This picture nicely illustrates the entire stellar life cycle of stars, starting with the Bok globules and giant gaseous pillars (evidence of embryonic stars), followed by circumstellar disks around young stars, and progressing to aging, massive stars in a young starburst cluster. The blue super-giant with its ring and bipolar outflow [upper left of center] marks the end of the life cycle.

  19. Classifying Stars • Stars of different temperatures radiate different colors of light. • Blue or Blue-white –hottest stars • Red—coolest stars • Others—yellow to orange Starlight is passed through a spectrograph to produce a spectrum. The spectrum contains sharp, dark lines. These lines indicate that some of the light is absorbed as it passes through the star’s outer regions. Studying the spectrum allows astronomers to determine the elements in the star, the temperature, and the size of its magnetic field.

  20. Spectral Classification of Stars (Surface temperature is the temperature in the middle of a star’s photosphere.)

  21. Absolute Magnitude • A star’s absolute magnitude is the brightness the star would have if it were at a standard distance from Earth. • To find a star’s absolute magnitude, an astronomer must first find out the star’s apparent magnitude and its distance from Earth. The astronomer then can calculate the stars brightness if it were at a standard distance from Earth. • Apparent Magnitude • A star’s apparent magnitude is its brightness as seen from Earth. • Astronomers can measure apparent magnitude fairly easily using electronic equipment. • You cannot tell how much light a star gives off just by its apparent magnitude.

  22. When stars are grouped according to brightness, the result is a band called the Main Sequence. Stars that do not fit into the main sequence are classified as giants, super giants, and white dwarfs.

  23. Brightnessdepends on the size, type and distance a star is from Earth. • Some stars appear brighter than others. A large hot star produces more light than a cool star. This large star would appear brighter than a cool star at the same distance. • To compare the actual brightness of stars, astronomers calculate what their brightness would be if the stars were the same distance from Earth. The Hubble Space Telescope's view of M32. Credits: NASA and Thomas M. Brown, Charles W. Bowers, Randy A. Kimble, Allen V. Sweigart (NASA Goddard Space Flight Center) and Henry C. Ferguson (Space Telescope Science Institute).

  24. Sirius is the brightest star in the Canis Major System. It appears so bright because it is only 9 ly away. Polaris—the current North Star Ursa Minor Constellation

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