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---------------------- 1804 - Our Milky Way
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- The Milky Way in the night sky stretching across the heavens is the structure of our Galaxy viewed edge-on. We get the image of a spiral galaxy which the Milky Way is, by seeing other galaxies thought to be similar.
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- We are slowly gathering the 3-D picture of our home by viewing it from the inside and having much of our vision blocked by dust clouds.
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- Using dust-penetrating infrared telescopes we have brought our own Galaxy into better focus. The central component is called the “ Bulge”. It is a vast football-shaped star cloud seen nearly end on. Our Galaxy became classified as a “ Barred Spiral Galaxy”.
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- Our Sun, and us too, lie 27,200 lightyears from the Galaxy center. We are 30% of the way out to the edge of the disk and 90 lightyears above the Galaxy’s midplane. It takes 240,000,000 years for our Solar System to complete 1 orbit around the Galaxy center. Since we are only 4,500,000,000 years old that means we have made only 18 trips to date ( 4500 / 240).
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- During each Galaxy orbit we have moved above and below the galactic plane.
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- Our closest star is Proxima Centauri which is 4.22 lightyears away. There are 400,000,000,000 stars in the Galaxy. Most are classified as “ M-Dwarf stars emitting very little visible light. M-Dwarfs burn dim but they will be shining for billions of years after our Sun dies.
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- Brown Dwarf stars are smaller still, between 1.2 and 7% of Solar Mass. There are 50 known stars within 16 lightyears but only 10% of them are visible to the naked eye. Of the 100 brightest stars 30% lie with 100 light-years.
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---------------------------- Sirius ------------------ 8.6 lightyears
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---------------------------- Procyon ---------------- 11 lightyears
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---------------------------- Vega ------------------- 25 lightyears
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---------------------------- Formalhaut ------------ 25 lightyears
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---------------------------- Castor ------------------- 52 lightyears
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---------------------------- Aldebaran --------------- 65 lightyears
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---------------------------- Regulus ----------------- 77 lightyears
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- All of these stars are 7 times Solar Mass and 10,000 times the Solar Luminance. All will burn rapidly and end as Supernovae before our Sun dies.
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- The unknown mass in the Universe is known as “ Dark Matter”. That is inside our Galaxy. Outside our Galaxy there are 85 other galaxies collectively known as the Local Group of galaxies. The Group spans a distance of 10,000,000 lightyears.
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- Dwarf Irregular galaxies have just a few thousand stars gravitationally coupled. Two of these are known as the Large and Small Megellanic Clouds. They are 160,000 and 200,000 lightyears away. Close enough that our Galaxy is collecting their material ( gas and dust ) depriving the Megellanic Clouds of their star forming ability. Our large Galaxy is the cannibal consuming our smaller companions.
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- The smallest galaxy, “ Seque 2” is 1/500 our size, 114,000 lightyears away, which is less than the diameter of the Milky Way and only 200,000 Solar Mass.
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- A typical galaxy has mass indicating 10 times more Dark Matter than visible matter.
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- There is a halo of gas around the Andromeda Galaxy that extends halfway to the Milky Way. The gas contains elements of carbon, oxygen, and silicon. Our two galaxies will merge in another 5 billion years.
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- Of the 85 or so galaxies in our Local Group only 3 have evidence of a massive Blackhole at their center. A galaxy must exceed 1,000,000,000 Solar Mass to host a Blackhole . Most of the 85 local galaxies are less than 100,000,000 Solar Mass.
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- Placing 1,000 Milky Ways end to end spans 100 million lightyears which is the size of the Virgo Supercluster of galaxies, 10^18 Solar Mass, that is mostly Dark Matter.
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- Distant galaxies ( M106) with water vapor pulses of microwave radiation are called ‘Masers”. These pulses can be used in distance measurements. Cepheid variable stars also emit pulses used in distance measurements. All these measurements modify our 2-D vision of galaxies into a 3-D map.
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- Now turning from looking outside our Galaxy to looking inside towards the center. At the center is a 4,000,000 Solar Mass Blackhole. It is named Sagittarius A* Star. The mass of this Blackhole was discovered by tracking the stars that are orbiting. it. Here is the math involved.
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------------------------- p^2 = 4 * pi^2 a^3 / G ( m1 + m2)
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------------------------ m1 = 5.9*10^11 a^3 / p^2
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----------------------- p = orbital period of the star
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----------------------- a = radius of the star’s orbit
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----------------------- G = 6,67*10^-11 m^3 / ( kg * sec^2)
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---------------------- m1 = mass of the much more massive body.
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- Orbiting he Blackhole are the dense cores of stars, filaments of hot magnetic gas, clouds of cold gas, dust scattered remains of dense massive stars, all crammed around the Blackhole about 230 lightyears across.
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- Chandra X-Ray, NuSTAR and SWIFT telescopes have detected evidence of this Blackhole as it is swallowing stars. Bright flares in hard X-rays. The X-ray radiation is thought to be coming from Magnetars, which are Neutron stars with intense magnetic fields. White Dwarf stars are stealing material from companion stars and other smaller Stellar Mass Blackholes.
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- Observing other galaxies is even easier then trying to study our Galaxy from the inside. There is just too much material to look through between us and the 24,900 lightyears distance to the galactic center’s Blackhole.
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- Markarin 231 is the nearest galaxy to Earth hosting a Quasar powered by two central Blackholes orbiting each other. Mrk 231 is 600,000,000 lightyears away.
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- The surrounding hot gas would glow in ultraviolet rays except the glow of the dusty disk drops off at the center. The disk has a big doughnut hole encircling the Blackholes. It is believed to be two Blackholes orbiting each other in 1.2 years.
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- The merge is evidenced by the host galaxies’ asymmetry and the long tidal tails of young blue stars.
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- The star formation rate of Mrk231 is 100 times greater that our Milky Way’s. The in falling gas fuels the Blackhole and the gas turbulence creates the new star formation.
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- The binary Blackholes are expected to spiral together and collide within a few hundred thousand years. These spiraling masses are ideal for creating “ gravitational waves”. These exist in theory but have yet to be discovered. Mrk231 central Blackholes are 150,000,000 Solar Mass with a smaller companion Blackhole of 4,000,000 Solar Mass.
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- Stay tuned an announcement will be made shortly.
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-Other reviews available upon request:
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- #1321 Milky Way’s Gamma Ray Bubbles
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- #1703 - Star streamers created as galaxies pull off stars.
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- #1526 - Galaxy Center is a pin ball machine.
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- #855 - Calculating the mass of the Galaxy’s Blackhole.
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- #1348 - A Galactic Journey around the Milky Way
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- #1228 - How many stars are in the Universe?
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--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
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- to: ------- jamesdetrick@comcast.net ------ “Jim Detrick” -----------
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----- 707-536-3272 ---------------------- Thursday, January 7, 2016 -----
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