What object is this?

Goal: To learn about Mercury Objectives: 1) To learn about Mercury’s Surface 2) To learn about what we can learn about Mercury from its interior 3) To learn about Mercury’s orbital and rotation quirks 4) To look at lots of new and beautiful Mercury images 5) To understand how Relativity plays a role in Mercury’s orbit. If time remains: Telescope properties.

What object is this? This is Mercury, and it does look a lot like the moon. This tells us a lot about Mercury.

What does this tell us about Mercury? Mercury has no real atmosphere. The surface of Mercury is heavily cratered. This means that the surface of Mercury is very old (4 billion years old) and geologically dead.

Mercury’s surface Most of Mercury’s surface is flat. However there are mile high cliffs called scarps which are miles long. There are also long faults as shown on the right.

What formed the cliffs? The cliffs are a result of cooling. The core of Mercury cooled so much early in its history that the planet shrunk by a few kilometers. The faults are another signature of this ongoing shrinking.

Why such a large core and small mantel? Since Mercury formed very close to the sun Mercury was only able to obtain dense materials with high melting and vaporization points such as iron. Also, it would seem that Mercury was impacted by a large object and that the resultant impact removed most of its mantel. Density 5.427 g/cm3

Orbital and Rotational stuff Orbital period: 88 days Rotational period: 59 days Due to tidal interactions with the sun, Mercury rotates 3 times every two times it orbits the sun. So, on mercury, a “day” (“day” meaning the time elapsed between sunrises) is actually 2 Mercurial years (176 earth days).

Long rotation + no atmosphere = HOT daytimes. Gets as high as 700 K (800 F) COLD nighttimes 100 K (-280 F)

Newest images: Messenger APOC

NASA

Spider!

Other quirks Highly elliptical orbit which is tilted from the ecliptic plane by 7 degrees. Always very close to the sun in the sky of the earth, so is very hard to photograph. Both probes where sent to Mercury at the same part of the Mercurial day, so we have only imaged half of Mercury to any decent details.

Final Quirk Since Mercury is so close to the sun, its orbital velocity is about 38 km/s. It is also further into the gravitational well of the sun. This does not sound like much, but this means that Mercury’s orbit has to be corrected for used Einstein’s laws of relativity. The correction is small, 37 arcseconds per century.

Special Relativity Clocks progress at a rate RELATIVE to their position in space. Velocity slows the progress of an object’s clock so that: Tobject = Tuniverse / gamma Gamma = 1 / (1 – v2/c2)1/2

General Relativity Mass warps space. Time is relative to space. Therefore masses warp time also! Tobject = Tuniversal / (1 – rs / r)1/2 Where rs is the Schwarzschild radius (the radius of the event horizon of a black hole) rs = 1.5 km * Mass of object / Mass of our sun

Mercury conclusion: Mercury has an old cratered surface which looks much like the moon. Mercury has a strange orbit and rotation which creates huge temperature extremes. Mercury is so close to the sun that its orbit differs by 37 arcseconds per century from what you expect.

Telescope properties: Which telescope property do you think is the most important? Collecting area Magnification Resolution