Milky Way

Actually where we are?

If you go to a dark spot, away from the bright city lights, and look up, you should be able to see the Milky Way as a cloudy band stretching across the sky. It really does look like spilt milk spread across the sky. But if you take a telescope and examine it more closely, you'll see that the clouds are actually the collective light from thousands of stars.

Since we're embedded inside the Milky Way, we're seeing our home galaxy edge-on, from the inside. To get a better idea, grab a dinner plate and take a look at it edge on, so you can't see the circular shape of the galaxy. You can only see the edge of the plate.

The Earth is located in the Solar System, and the Solar System is located about 25,000 light-years away from the core of the galaxy. This also means that we're about 25,000 light-years away from the outer edge of the Milky Way. We're located in the Orion Spur, which is a minor arm located in between the two major galactic arms

Appearance from Earth

All the stars that the eye can distinguish in the night sky are part of the Milky Way Galaxy, but aside from these relatively nearby stars, the galaxy appears as a hazy band of white light arching around the entire celestial sphere. The light originates from stars and other material that lie within the galactic plane. Dark regions within the band, such as the Great Rift and the Coalsack, correspond to areas where light from distant stars is blocked by dark nebulae. The Milky Way has a relatively low surface brightness due to the interstellar medium that fills the galactic disk, which prevents us from seeing the bright galactic center. It is thus difficult to see from any urban or suburban location suffering from light pollution.

The center of the galaxy lies in the direction of Sagittarius, and it is here that Milky Way looks brightest. From Sagittarius, the Milky Way appears to pass westward through the constellations of Scorpius, Ara, Norma, Triangulum Australe, Circinus, Centaurus, Musca, Crux, Carina, Vela, Puppis, Canis Major, Monoceros, Orion and Gemini, Taurus, Auriga, Perseus, Andromeda, Cassiopeia, Cepheus and Lacerta, Cygnus, Vulpecula, Sagitta, Aquila, Ophiuchus, Scutum, and back to Sagittarius. The fact that the Milky Way divides the night sky into two roughly equal hemispheres indicates that the Solar System lies close to the galactic plane.

What is The Milky Way?

The Milky Way is the galaxy which is the home of our Solar System together with at least 200 billion other stars (more recent estimates have given numbers around 400 billion) and their planets, and thousands of clusters and nebulae, including at least almost all objects of Messier's catalog which are not galaxies on their own (one might consider two globular clusters as possible exceptions, as probably they are just being, or have recently been, incorporated or imported into our Galaxy from dwarf galaxies which are currently in close encounters with the Milky Way: M54 from SagDEG, and possibly M79 from the Canis Major Dwarfdwarf). All the objects in the Milky Way Galaxy orbit their common center of mass, called the Galactic Center.

The Milky Way is believed to be more than 13 billion years old, which is estimated to be virtually as old as the entire Universe itself. The Milky Way galaxy is actually just one of billions of galaxies contained within the Universe, although very little is currently known about its seemingly infinite galactic counterparts.

The Milky Way galaxy has a whopping circumference of roughly 250-300 thousand light years! Within the main body of the Milky Way there are estimated to be between 200 and 400 billion stars. The Earth’s solar system is believed to exist very close to the Galaxy’s galactic plane, due to the fact that the Milky Way essentially divides the night sky into two virtually equal hemispheres.

What you should know the minimum of the Milky Way
The Milky Way is an example of a barred spiral galaxy. It measures approximately 100,000 light years across and it's only 1,000 light years thick; although, it's more thick at the core where the galaxy bulges out. If you could fly out of the Milky Way in a rocket and then look back, you'd see a huge spiral shaped galaxy with a bar at the center. At the ends of this bar, there are two spiral arms which twist out forming the structure of the Milky Way.

Scientists now estimate that in roughly three billion years, the Milky Way galaxy w i ll actually collide with the Andromeda Galaxy, which is very slowly working its way towards u s at a modest speed of about 1,800 kilometers per minute.

Observation data
Diameter = 100,000 light years
Thickness = 1,000 light years
Number of stars = 100–400 billion
Oldest known star = 13.2 billion years
Mass = 5.8 × 1011 M (solar mass)
Sun's distance to galactic center = 25,000 light years
Sun's galactic rotation period = 250 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 (cosmic microwave background)

Links
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