galaxies. galaxies a galaxy is a huge region of space that contains hundreds of billions of stars,...
Post on 27-Dec-2015
225 Views
Preview:
TRANSCRIPT
GalaxiesGalaxiesA galaxy is a huge region of space that A galaxy is a huge region of space that
contains hundreds of billions of stars, contains hundreds of billions of stars, planets, glowing nebulae, dust, empty planets, glowing nebulae, dust, empty space, and possibly black holes.space, and possibly black holes.
Galaxies began when large clouds of Galaxies began when large clouds of gas and dust started to shrink as a gas and dust started to shrink as a result of their gravity.result of their gravity.
GalaxiesGalaxies
Galaxies are held together by gravity. Galaxies are held together by gravity.
According to Hubble’s Law, galaxies According to Hubble’s Law, galaxies are moving away from one another.are moving away from one another.
100 billion or so exist in the universe100 billion or so exist in the universe..
Shapes of GalaxiesShapes of Galaxies
Hubble categorized these shapes or Hubble categorized these shapes or basic schemes of galaxies:basic schemes of galaxies:
1. Spiral1. Spiral
2. Elliptical (nearly circular)2. Elliptical (nearly circular)
3. Irregular3. Irregular
Spiral GalaxiesSpiral Galaxies
Arms tightly wound around galaxy, like a Arms tightly wound around galaxy, like a pinwheelpinwheel
A group of objects in center (stars and A group of objects in center (stars and possibly a black hole)possibly a black hole)
Surrounded by a halo and an invisible Surrounded by a halo and an invisible cloud of matter.cloud of matter.
Spiral GalaxiesSpiral Galaxies
Rotating – which forms armsRotating – which forms arms
May lose arms and become ellipticalMay lose arms and become elliptical
Examples: Milky Way and Andromeda Examples: Milky Way and Andromeda GalaxiesGalaxies
Elliptical GalaxiesElliptical Galaxies
Can be round, oval, flattened or sphericalCan be round, oval, flattened or spherical
Resembles the nucleus of a spiral galaxy Resembles the nucleus of a spiral galaxy without the armswithout the arms
Very little gas or dustVery little gas or dust
Elliptical GalaxiesElliptical Galaxies
Mostly older starsMostly older stars
Collect into globular clustersCollect into globular clusters
Examples: Maffei 1, M32Examples: Maffei 1, M32
Irregular GalaxiesIrregular Galaxies
Neither spiral or ellipticalNeither spiral or elliptical
Disk, but no spiral armsDisk, but no spiral arms
Caused by the formation of new stars in Caused by the formation of new stars in the galaxy or by the pull of neighboring the galaxy or by the pull of neighboring gravitational fieldsgravitational fields
Irregular GalaxiesIrregular Galaxies
In some irregular galaxies one can see In some irregular galaxies one can see individual stars, nebulae, and clustersindividual stars, nebulae, and clusters
Mixture of old and new starsMixture of old and new stars
Large amounts of gas and dustLarge amounts of gas and dust
Examples: Large and Small Magellanic Examples: Large and Small Magellanic CloudsClouds
Barred Spiral GalaxiesBarred Spiral Galaxies
Spirals with bright bar Spirals with bright bar of gas down center.of gas down center.
Lenticular GalaxiesLenticular Galaxies
Consists of bulge and Consists of bulge and disk with little or no disk with little or no new star formation.new star formation.
Example: Spindle Example: Spindle GalaxyGalaxy
Parts of a GalaxyParts of a Galaxy
The galaxy is made up of two visible The galaxy is made up of two visible components:components:
1. Disk1. Disk
2. Bulge2. Bulge
Parts of a Galaxy – The DiskParts of a Galaxy – The Disk
Contains clouds of gas and dust called Contains clouds of gas and dust called nebulaenebulae
In a spiral galaxy, most stars are in the In a spiral galaxy, most stars are in the diskdisk
Open Cluster (Galactic Clusters) are Open Cluster (Galactic Clusters) are younger, asymmetric groups of stars. younger, asymmetric groups of stars.
Parts of a Galaxy – The DiskParts of a Galaxy – The Disk
An example of a An example of a galactic cluster is galactic cluster is Pleiades (M45)Pleiades (M45)
Parts of a Galaxy - BulgeParts of a Galaxy - Bulge
A large squashed sphere surrounding the A large squashed sphere surrounding the galaxy’s centergalaxy’s center
Contains older starsContains older stars
Not very much gas or dustNot very much gas or dust
One fifth of the total light comes from the One fifth of the total light comes from the bulgebulge
Parts of a Galaxy - BulgeParts of a Galaxy - Bulge
The bulge can be used to determine the The bulge can be used to determine the age of the galaxyage of the galaxy
Above and around the bulge are globular Above and around the bulge are globular clusters – hundreds of thousands of stars clusters – hundreds of thousands of stars bound in a tight spherical swarmbound in a tight spherical swarm
Parts of a Galaxy - BulgeParts of a Galaxy - Bulge
An example of a An example of a globular cluster is globular cluster is M13 (Hercules M13 (Hercules Globular Cluster)Globular Cluster)
The Milky Way GalaxyThe Milky Way Galaxy
Over 100 billion stars and possibly a black Over 100 billion stars and possibly a black hole in the center.hole in the center.
Has star clusters, planets, glowing Has star clusters, planets, glowing nebulae, dust and empty space.nebulae, dust and empty space.
Older stars and globular cluster near the Older stars and globular cluster near the centercenter
The Milky Way GalaxyThe Milky Way Galaxy
Younger stars and galactic clusters in diskYounger stars and galactic clusters in disk
One hundred thousand (100,000) light One hundred thousand (100,000) light years in diameter. Ten thousand (10,000) years in diameter. Ten thousand (10,000) light years thicklight years thick
Our solar system is located on the Orion Our solar system is located on the Orion Arm – 30,000 light years from the center.Arm – 30,000 light years from the center.
The Milky Way GalaxyThe Milky Way Galaxy
Part of the Local Group of galaxies with 30 Part of the Local Group of galaxies with 30 others. (Andromeda is also part of this others. (Andromeda is also part of this group)group)
Astronomers use radio and infrared Astronomers use radio and infrared telescopes to “see” the center of the galaxytelescopes to “see” the center of the galaxy
We can’t actually “see” the center of the We can’t actually “see” the center of the galaxy because of dust and gas!galaxy because of dust and gas!
The Milky Way GalaxyThe Milky Way Galaxy
The Milky Way is getting larger because it The Milky Way is getting larger because it is “eating” the Large Magellanic Cloud. Its is “eating” the Large Magellanic Cloud. Its stars are being added to the Milky Way.stars are being added to the Milky Way.
The Milky Way is falling toward the The Milky Way is falling toward the Andromeda Galaxy and both are feeling Andromeda Galaxy and both are feeling the tug of the great the tug of the great Virgo ClusterVirgo Cluster, which , which is 50 million light years away.is 50 million light years away.
Andromeda Galaxy (M31)Andromeda Galaxy (M31) Can only be seen by astronomers in the Can only be seen by astronomers in the
Northern hemisphereNorthern hemisphere
2.2 million light years away2.2 million light years away
Can see without a telescope, appears as a faint Can see without a telescope, appears as a faint fuzzy patchfuzzy patch
About the same size as the Milky WayAbout the same size as the Milky Way
Two times more massive than the Milky WayTwo times more massive than the Milky Way
Large and Small Magellanic CloudsLarge and Small Magellanic Clouds
Can only be seen by astronomers in the Can only be seen by astronomers in the Southern HemisphereSouthern Hemisphere
The two closest galaxies to the Milky Way The two closest galaxies to the Milky Way (Less than 200,000 light years away)(Less than 200,000 light years away)
Visible to the naked eyeVisible to the naked eye
Large and Small Magellanic CloudsLarge and Small Magellanic Clouds
Relatively small and irregular in shapeRelatively small and irregular in shape
Only five percent of the mass of the Milky Only five percent of the mass of the Milky WayWay
Large Magellanic is being “eaten” by the Large Magellanic is being “eaten” by the Milky WayMilky Way
Messier Catalog SystemMessier Catalog SystemCharles Messier was looking for comets.Charles Messier was looking for comets.
Made a list of star clusters, galaxies and Made a list of star clusters, galaxies and nebula so that he would not mistake them nebula so that he would not mistake them for comets.for comets.
Listed 110 objects, including 32 galaxies Listed 110 objects, including 32 galaxies by 1780.by 1780.
Andromeda – M31Andromeda – M31
top related