19 - Methods to See Really Big Things from Really Far Away (w/ Emma Raich!)

19. Methods to See Really Big Things from Really Far Away

Last week we discussed seeing objects that are atomically small. Seemingly atomically small from our naked eyes on Earth, it can be incredibly challenging to see entire planets in the universe. Today, we will discuss astronomy, planets and stars, current ways to see these objects, and how round the Earth is. Let’s learn to be scientifically conversational.


General Learning Concepts

1)    What are some things that astronomers look for?

a.    What is an astronomer? An individual who seeks an understanding of how the universe works. This ranges from examining planets to stars to systems of galaxies to the entire universe. There are, of course, people who do this who are not astronomers but would rather be called engineers, programmers, cosmologists, or otherwise. [2]

b.    What is a planet? Definition as of 2006: it must orbit around the sun; be massive enough to have gravity force a spherical shape; large enough that gravity has cleared away objects of similar sizes. These rules refer to our own planet and the lines get fuzzy with exoplanets (planets not in our own solar system).

c.     What is a star? Sphere of hot glowing gas. They produce their own light and energy by undergoing nuclear fusion. They’re a fundamental building block of galaxies as they manufacture and distribute periodic elements like carbon, nitrogen, and oxygen.

d.    Galaxy: The galaxy that we live in is known as the Milky Way. A galaxy is a collection of gas, dust, and billions of stars and solar systems all held together by gravity. There are galaxies that are spiral-shaped (think a pinwheel!) like ours. There are also small, smooth, oval shaped galaxies. There are galaxies that are blob shaped (irregular).

e.    The Universe: Oh boy, a mixture of science and philosophy! The definition spins it as all existing matter and space as a whole. Cosmologists think the universe was created during the big bang (13.8 billion years ago) and is continually expanding. https://www.nasa.gov/audience/forstudents/k-4/home/F_What_is_the_Universe.html

2)    How did ancient astronomers see these objects?

a.    Early record keeping: Looking up at the sky! Record keeping was done fastidiously and the stars moved in predictable ways with enough data. ~1600 BC, Babylonians recorded positions of planets, times of eclipses, and so on. This was also seen in Chinese, Central American, and North European cultures. [2]

b.    Stars vs Planets: Stars moved in very predictable paths or very little due to the distance from the earth that they are. Planets moved in far less predictable patterns and were named planets because they were “wanderers” in Greek.

c.     Early telescopes: The telescope is commonly associated with Galileo, but the earliest known existing telescope came from a patent application in Holland in 11608 by Dutch spectacle maker Hans Lippershay (for making and distributing an instrument that would allow one to see distant objects as if they were nearby). Galileo did, however, first use the telescope for astronomy in 1609, first with a telescope that could magnify things 3 times and then with another that could magnify objects 20 times. He was capable of more capably observing the moon, discovered four satellites of Jupiter, observed a supernova, verified phases of Venus, and discovered sunspots. All from a 20x increase!

d.    Hubble Space Telescope: Difficulties with doing very precise astronomy from your backyard are apparent. Starlight is distorted (bent) by the Earth’s atmosphere, like looking at an object through a glass of water. Unfortunately, ground-based telescopes are subject to the same issues. This resulted in the development and eventual launch (1990) of the Hubble Space telescope. NASA says that Hubble has the pointing accuracy of .007 arcseconds, which is like being able to shine a laser beam on President Roosevelt’s head on a dime about 200 miles away. [2]

3)    What are current techniques to see these objects?

a.    Very Large Telescope: An advanced optical telescope that consists of four main telescopes and four smaller telescopes that can be used independently or combined to be a single, larger telescope. It’s on the Earth’s surface and uses advanced optics to be able to correct for the atmospheric haze; that is, the light of the star hits earth and wobbles and we correct for that by adding a mirror that is capable of wobbling. We can find out how much wobble to correct for by shining a laser at an improbably perfect star in the atmosphere. It has been used to take pictures of exoplanets, clocking in speeds of exoplanet’s rotations, and probed exoplanet atmospheres.

b.    Multi-star Wavefront Control: In general, to be able to see planets around stars, astronomers use something called a coronagraph (which blocks out the star’s glare, awlloing for seeing faint light reflected off the planet). There are difficulties seeing exoplanets in systems that have more than one star because it is not practical to use more than one coronagraph. This technique only requires a deformable mirror (which is almost always present in modern coronagraphs) to be able to remove light from more than one star.

4)    Fun Tidbits

a.    Astrobiology: Are we alone in the universe? Astrobiologists work to study life beyond our planet, often asking questions like how life originated, evolved, in what environments and at which extremes, and what life might look like elsewhere. Sometimes, this work overlaps with early earth research like the famous Urey-Miller experiment. [2]

i.    A spark, simulating lightning, provided the energy to break down molecules [flask of a chemical solution of methane, ammonia, hydrogen and water] in the simulated atmosphere. The molecules, which mixed with water vapor from a simulated ocean and underwent further chemical reactions, eventually formed amino acids, a key component of life.

b.    The Earth is Round: Eratosthenes (276 BC), a Greek mathematician, heard that in Syene (a city south of Alexandria) there were no vertical shadows cast at noon on the summer solstice. The sun was exactly overheard. In Alexandria, at that same day, there was a shadow that measured around 7 degrees. That meant that if there wasn’t one in Syene, the earth must have a curvature. The idea had been given by Pythagoras around 500 BC. Eratosthenes used these measurements to roughly calculate the circumference of the Earth, and he was very close. (40,000 km vs 40,030 km).

5)    Solicited Questions

a.    Why is the universe still expanding? This is a tricky topic. From our perspective, we can only observe so far. Paul Sutter (astrophysicist at The Ohio State University, who hosts podcasts like ‘Ask a Spaceman’ and ‘RealSpace’) says that from our perspective the universe seems to be expanding around us. Meanwhile, if we moved to Andromeda, it still would look like we would be at the center of the universe. He says going even farther, if you went as far as you possibly could from where we were, you’d still think that. He says that every galaxy is receding from every other galaxy (in simple terms). He uses common analogies that galaxies are like raisins in a loaf of bread as the bread is rising in the oven. Space is expanding, and galaxies come along for the ride. The issue is that there isn’t the air that the bread is rising into; that the entire universe is the surface of that bread. He goes on to recommend his specific podcast “What’s the point in talking about science” on Ask A Spaceman.