January 19, 2020 – Surveying the Milky Way

Do you own property?  Has it been surveyed?  Has it been surveyed again?  Did the surveys agree?

In my experience the possibility of two surveys not agreeing is good.  Why?  Change.  Change in how surveys are done, change in technology, sometimes a previous owner moved the markers, or someone made a mistake in the first place.  If this is challenging in a few acres, just imagine the difficulty with surveying our Milky Way!

We live on one small planet in a solar system that disappears in the landscape of our immediate neighborhood within the Milky Way.  How can we possibly determine the size, shape, and configuration of our home galaxy?

Good thing there are very smart folks taking on this challenge.  If it were up to me, I’d go back to bed.

The Greeks called it galaxias kyklos or “milky circle”, translated into Latin as via lactea, “milky way”.  It was the Greek Democritus, sometime around 350 BC, who first suggested the Milky Way was composed of stars.  His suggestion wasn’t taken too seriously by the rest of the world.  Then Galileo Galilei resolved the hazy light into stars with his telescope in 1610 and confirmed Democritus’s idea.  William Herschel first mapped it in 1785.  He studied stellar distributions and plotted their positions, concluding the Milky Way is a disk-shaped object.  He was on the right track.

Until Edwin Hubble observed that other disk-shaped nebulae were full of stars, the Milky Way was considered our entire universe. We then realized we lived in one of many such nebulae, now called galaxies.

Astronomers began plotting positions of star collections, clusters of young stars and concentrations of hydrogen gas and by 1954 had the first crude sketch of the Milky Way’s shape.  By the mid 1970’s we had a good but incomplete picture of our galaxy’s spiral shape.  Using radio telescope and microwave data astronomers have been able to see how bands of dust, gas, and stars curve into spiral arm shapes, even arm extensions called spurs.  Data from the Spitzer Space Telescope, in the infrared, can penetrate dense dust and reveal structure within the central portions of our galaxy.  From this they have been able to plot the shape of the Milky Way.

We live in what’s called a barred-spiral galaxy, a common galaxy shape.  The bar is thought to be formed by stars caught up by resonance in the Milky Way’s rotation.  Astronomers have named 9 spiral arms so far and we live in the Local/Orion Arm.  The Milky Way also has two huge bubbles/bulges of plasma emanating from the center, perpendicular to the galactic disk.

Now let me get back to the county engineer’s website and GIS maps for my property.

What’s in the Sky?

January 20; dawn; east:  A crescent Moon, Antares, and Mars form a triangle before sunrise

January 26/27; night; high/north:  Telescopic Comet PanSTARRS (C/2017 T2) is just north of the Double Cluster