All About The Milky Way Galaxy and Our Solar System

all about milky way

Let’s take a tour of the local solar system and review data about the Milky Way Galaxy in order to familiarize ourselves with the local space that we exist in!

The Milky Way Galaxy

milkywayThe Milky Way Galaxy is a spiral galaxy; our sun and solar system are a small part of it. Most of the stars that we can see are in the Milky Way Galaxy. The main plane of the Milky Way looks like a faint band of white in the night sky. The Milky Way is about 100,000 light-years in diameter and 1,000 light-years thick. There are about 2 x 10 (11) stars in the Milky Way. This spiral galaxy formed about 14 billion years ago. It takes the sun roughly 250 million years to orbit once around the Milky Way. The Earth is about 26,000 light-years from the center of the Milky Way Galaxy. The major arms of the Milky Way galaxy are the Perseus Arm, Sagittarius Arm, Centaurus Arm, and Cygnus Arm; our Solar System is in a minor arm called the Orion Spur.

Observation data

Type: SBbc (barred spiral galaxy)
Diameter: 100,000 light years
Thickness: 1,000 light years (stars)
Number of stars: 200 to 400 billion
Oldest known star: 13.2 billion years
Mass: 5.8 × 1011 M
Sun’s distance to galactic center: 26,000 ± 1,400 light-years
Sun’s galactic rotation period: 220 million years (negative rotation)
Spiral pattern rotation period: 50 million years
Bar pattern rotation period: 15 to 18 million years
Speed relative to CMB rest frame: 552 km/s

The Milky Way galaxy is the spiral galaxy we call home, as do roughly 100 billion other stars. It looks very much like other spiral galaxies when viewed from above. There are spiral arms and a bright central part. The Sun is far from the center of the Galaxy, halfway to the edge of the Galaxy along the Orion spiral arm. The Sun is revolving around the center of the Galaxy at a speed of half a million miles per hour, yet it will still take 200 million years for it to go around once.

Do you feel like you are moving at that speed through space? If you did, you would certainly need a seat belt! When we run, we feel the wind on our bodies because there are molecules which make up the air that push against our bodies. But there are very few molecules in the space between the stars. So there is nothing to push against our planet so that we “feel” like we are rushing around at half a million miles per hour.

Our Solar System

Our solar system is one of natural beauty and the home of the human race.

The Planets


Mercury-60584068The planet Mercury is very difficult to study from the Earth because it is always so close to the Sun. Even at elongation, it is never more than 28 degrees from the Sun in our sky. It is the second smallest planet (it was believed to be the smallest until the discovery that Pluto is actually much smaller than originally thought), and also the fastest in its orbit since it is the innermost planet. In fact, the name Mercury derives from its speed in moving around its orbit. Until the 1960s, Venus was often considered a “twin sister” to the Earth because Venus is the nearest planet to us, and because superficially the two planets seem to share many characteristics.


Planet_Venus_2007The Planet Venus In earlier times, there was considerable speculation concerning the possibility of life on Venus, sometimes with rather elaborate characteristics. In 1686 a French “man of letters”, Bernard de Fontenelle, wrote that I can tell from here. what the inhabitants of Venus are like; they resemble the Moors of Granada; a small black people, burned by the sun, full of wit and fire, always in love, writing verse, fond of music, arranging festivals, dances, and tournaments every day.(Quoted in National Geographic, June, 1975)

Now apart from the fact that this description is rather unremarkable because it sounds like everyday student life around a great University like ours, it turns out that Monsieur de Fontenelle was quite incorrect about Venus and its conjectured inhabitants. Modern views of Venus In the last 30 years we have learned a great deal about our “sister” planet, and we now know that almost nothing on Venus is like that on the Earth. Much of the previous misconception can be traced to the difficulty of observing Venus because it is always covered with a thick cloud layer. In the past 3 decades astronomers have learned how to peer through that cloud layer and unlock many of the secrets of this nearby but previously not well known planet.


earth_pacificThe Earth is certainly the most familiar human planet, though it has only been a few hundred years since we fully realized it was a planet. We begin our study of objects in the Solar System with the Earth because it is interesting in its own right, and it provides a test of many observing techniques that we wish to use for other objects in the Solar System. The Earth is, at least by human standards, a beautiful planet, as the following images indicate.


Mobius is a beautiful blue and white ball that orbits the sun along the same orbitational flow as we do but it is hidden behind the sun opposite us and that is why we have not been able to see Mobius. It is the sister planet of our own planet Earth and could be called the third planet from the Sun. It is the largest of the inner planets. Mobius & Earth are the only planet known to support life and are the only planets to have liquid water upon the surface.


The-planet-marsThe “Red Planet” is named after the Roman god of war because it commonly appears with a reddish tinge when viewed in our sky. It has always held a fascination for those interested in the possibility of life on other planets.


Jupiter-IoJupiter is by far the largest of the planets. It is more than twice as massive as all other planets combined; if it had been only about 100 times more massive at birth (not so much by astronomical standards) it would have become a star instead of a planet. Then the Solar System might be a double star system instead of a single star with a planetary system. Jupiter has features very different from terrestrial planets. Its composition is more like that of stars, and if it has any solid surface it is hidden deep at its center: Jupiter is apparently almost entirely gas and liquid. It also has an internal energy source and enormous magnetic fields. Finally, the 4 largest moons of Jupiter (the Galilean Moons) are sufficiently interesting in their own right that they are among the most studied objects in the Solar System.


saturnSaturn, the second most massive planet, and the most distant planet known to the ancients, is one of the most beautiful sites in the Solar System, as witnessed by the adjacent image. The most striking feature of Saturn is the spectacular ring system. Although this feature is no longer unique, since we now know that all the Gas Giant planets have rings, the rings of Saturn are much more elaborate than those of any of the other planets. Saturn shares many features with its even larger Gas Giant neighbor Jupiter, but has various unique features in its own right.


Uranus2Uranus, the first planet discovered in modern times. It was found accidentally by William Herschel while he was searching the sky with a telescope in 1781. It had actually been seen many times before but dismissed as a star.
Uranus is largely hydrogen and helium, but (like Neptune) contains higher proportions of heavy elements than Jupiter or Saturn, and is covered with clouds. Our only direct spacecraft observation of Uranus came from Voyager 2 in 1986.


neptune_voy2The Planet Neptune is like Uranus in many ways, but has its own unique features. Because of Pluto’s highly elliptical orbit, it is currently the most distant planet from the Sun, at a separation of about 30 Astronomical Units. Neptune has been particularly challenging to study from the ground because its disk is small and badly blurred by the Earth’s atmosphere at that distance. In spite of this, ground-based astronomers had learned a great deal about this planet since its position was first predicted by Adams and Leverrier in 1845. However, our most detailed information about Neptune has come from the Voyager 2 flyby in 1989.

2004 DW

The Planet 2004 DW could even be larger than Pluto’s moon, Charon which is 1,300km (810 miles) across. It has an orbit that is much larger than Pluto’s, being, on average, 2.4 billion km (1.5 billion miles) further out. Astronomers believe that there are many more so-called “Kuiper Belt Objects” awaiting discovery in the cold, dark, outer reaches of the Solar System. The Kuiper Belt (KB) is a region inhabited by small worlds of rock and ice. It is similar in some ways to the Asteroid Belt – a region of rocky debris between Mars and Jupiter. However, the KB contains a hundred times more material than all the asteroids put together.


PlutoFlickrThe Planet Pluto, which was discovered in 1930, is but a dot of light in even the largest Earth-based telescopes. Pluto is 2/3 the size of Earth’s moon but 1,200 times farther away, which makes viewing surface detail as difficult as trying to read the printing on a golf ball located thirty-three miles away (more info). The adjacent movie made from recent Hubble Space Telescope computer enhanced images (Ref) indicates that we are finally beginning to resolve some detail on the surface of this distant planet.


The planet Quaoar is the 11th planet in the meridian solar system . Its orbit is different than the other planets in our solar system. The surface of Quaoar is barren it consists mainly of hard rock and ice there is a light atmosphere around the planet Quaoar but it’s not fit for humans. There are no life forms on the surface of Quaoar it is a dead planet and you could say the planet Quaoar is a large rock trapped in the darkness of the Kuiper belt in an orbit around our sun.


The planet Sedna is the second most reddish planetary body in the Solar System, after Mars. Although inclined by only around 11.9 degrees from the ecliptic where the eight major planets orbit, Sedna’s distant orbit is extremely elliptical indicating that its formation and orbit may have been influenced by a passing nearby star during the early years of the Solar System, when Sol formed out of a molecular cloud with many other closeby stars around 4.6 billion years ago. There is indirect evidence (an unexpectedly slow 40-day rotation) that Sedna has its own moon, which astronomers hope to confirm with the Hubble Space Telescope (more information and images from NASA. The icy object will move closer to the Sun over the next 72 years — to 76 AUs of Sol — before receding back towards the inner Oort Cloud.

Icy Worlds Beyond Pluto

kuiper-1Roughly 1,000 Kuiper Belt objects have been discovered orbiting beyond Neptune since the first was found in 1992. Now researchers are suggesting that these icy objects — considered to be leftover building blocks of the solar system — are much smaller than was originally thought. The key is albedo, a measure of how much light an object reflects. Using a presumed albedo of four percent, which is the figure for comets, astronomers had calculated the size of the Kuiper Belt objects, and believed there were more than 10,000 KBOs with diameters greater than 100 kilometers (62 miles), compared to 200 asteroids known to be that large in the main asteroid belt between Mars and Jupiter.


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