1900’s-Today: Continued

And now we bring you the second part of our history of the 1900s.

Objects or expanding our knowledge of the Universe, who discovered them:

With all these new discoveries, theories, and fancy technologies we must have found more about the Universe, and we did. One object would be the pulsar, discovered by Jocelyn Bell Burnell and Anthony Hewish.  Burnell wasn’t given direct credit until later despite being the actual discoverer.  But either way, the discovery came around 1968.  It was even thought to be some sort of alien, being called Little Green Men (LGM), but after looking at the radio data, they found what we now call a pulsar, appropriate since they spin so quickly that they appears to pulse in milliseconds.  There is also the quasar, discovered by Allan Rex Sandage and Thomas Matthews.  Technically it wasn’t discovered by one or two people, but only found after many people spent many years from the 1940’s to 1962 looking at many many spectral and radio sources.  Both objects show how radio astronomy allowed us to gain a greater insight into the different objects of our universe.

One of the most famous objects to be detected is the black hole.  Technically a black hole can’t be directly seen since it would theoretically appear black as surrounding space, but possible systems and waves of energy created by gravity should be able to detected.  The first person to apply modern physics to one of these very dark objects was Karl Schwarzschild, who found that the mass of the progenitor star (the star that the black hole came from) is linked to the distance that a black hole’s gravity would have an effect.  The black hole actually has some significant betting and arguing behind it.  As stated, Chandrasekhar made a mass limit that was fairly controversial, but with work, people found that a neutron star would have a separate limit which would create a black hole if exceeded.  Stephen Hawking bet that the first strong candidate for a black hole, the X-ray binary system Cygnus X-1 which was found by Thomas BoltonLouise Webster, and Paul Murdin in 1972, would not be one. Hawking is known for making other bets and failing, like betting with John Preskill against Kip Thorne that radiation from a black hole would create an apparent loss of information (he eventually gave up on this), and also betting against the Higgs boson.  But the man did discover Hawking radiation and did very important theoretical work despite suffering from an impairing motor neuron disease.

You can clearly see here that you cannot see this.

Another very famous discovery was that not only was the Universe expanding like Hubble thought, but it is accelerating as a result of dark energy, something that we don’t exactly understand.  This discovery was made in 1998 by  Saul Perlmutter, Brian Schmidt, and Adam Riess, using data on Type Ia supernovae collected by Schmidt and Nicholas Suntzeff.  The name took a cue from dark matter, as both are placeholders to show their very interesting effects for which we can’t quite find something specific that would create the effect.

There is so much going on with the universe as a whole that we have yet to state the full structure of our very own Solar System.  To start we have Planet X, or Pluto (now a dwarf planet).  The man who discovered this officially is Percival Lowell, more of an 1800’s man, but he started the lookout for it in 1906, so we figure he belongs here.  However, Clyde Tombaugh was the one who really found it, in 1930. Funny how with that we have effectively reached the edge of our Solar System.  Well, not really, since  Gerard Kuiper discovered the Kuiper belt, a ring of rocky objects around our solar system, and Jan Oort discovered the Oort Cloud, a giant cloud around the Kuiper belt that is almost a sphere of comet-like objects.  Oort also created some of the earliest evidence of dark matter and improved radio astronomy.  Now, does this mean that we have finally learned everything to know about the Solar System?  No, that would be no fun.

The whole Solar System, very different from the system thought up by Ptolemy. Thankfully no 80+ epicycles.

Besides all this, two other interesting objects were discovered.  One is the brown dwarf; discovered in 1988 by Eric Becklin and Ben Zuckerman.  These are “stars”, put in quotes because they haven’t had the mass to start fusion.  The other major objects we have discovered are exoplanets, officially discovered also in 1988 by Bruce CampellG. A. H. Walker, and Stephenson Yang.  The reason we mention these two at the same time is because they were thought to be the same thing.  Research until 1990 was done to further prove the difference between brown dwarfs and exoplanets, but science always needs further confirmation, so it took until 2003 with some new fancy technology to make it pretty official.  But now where does that lead us?  You see, there is this situation with Pluto.  Finding all these different lower mass objects outside our solar system, we found planets orbiting close to the Sun that are as massive as Jupiter, along with many others.  That, it being different from other planets in size and orbit, and the discovery of another dwarf planet named Eris which is more massive and about the size of Pluto created the debate.  Poor lonely Pluto, but it’s scientific progress.

There is also the idea of popular science.  This was around for a long time, but with the advent of television, movies, and improved speed of print, science could be delivered to a far broader audience.  With magazines there were Popular Science and New Scientist.  With literature there were the big three, Isaac Asimov, Arthur Clarke, and Robert Heinlein.  With television there were Carl Sagan and Bill Nye.  All of this was readily available to people, both as inspiration and for learning.  A last well-known scientist would be Neil deGrasse Tyson, for supporting NASA and taking after Carl Sagan’s Cosmos to teach many about the grand Universe we live in.

As we said, Astronomers (and looking to the name of this blog, Neil deGrasse Tyson specifically) are quotable: “I think of space not as the final frontier but as the next frontier. Not as something to be conquered but to be explored.”

Organizations and general new technologies:

A variety of organizations were formed for space research and to teach the public about Astronomy.  One was the American Association of Variable Star Observers (AAVSO) formed in 1911 for amateur and professionals alike to come together and search the skies.  There was the International Astronomical Union (IAU)  started in 1919.  Yes, the people responsible for Pluto’s demotion, but a unified international organization to meet on issues like these is certainly important.  Next there is the National Aeronautics and Space Administration (NASA), which was founded in 1958, after the US decided that a Space Race was on with the Soviets.  This was some race, even getting men to the moon.  But even with that, “NASA spin-off technologies”, such as kevlar, water purification, and LEDs, stemmed from the research.  Another organization was Search for Extraterrestrial Intelligence (SETI), set up since 1984.  This organization searches everywhere for signs of life, using the Drake Equation, developed by Frank Drake, to show what possibilities to look at when searching for life.

Man on the Moon

An example of how NASA did something very awesome.

There were many technological advancements like the Mount Wilson Observatory.  By the very same man who built the Yerkes Observatory, George Ellery Hale, this was built with the Hooker and Hale telescopes.  The importance to this was that from 1917 to 1948 it was the largest reflecting telescope in the world.  In addition to that, it was built in mountains near Pasadena, which had improved visibility because of smog trapped over Los Angeles.  It was most famously used by Russell for star classification and by Hubble for his major calculations.

But after 1948?  Telescopes could be built bigger, created for specific purposes, and the creation of satellites created a completely new view of space. To start, radio astronomy was mainly ground-based, because sending equipment to space is very difficult, costly, time-consuming, and dangerous if repairs are needed.  So, if fine radio images can be taken here on Earth, they will be.  An example of this is the Very Large Array or VLA, which has detected objects from galaxies to quasars to pulsars.  There was also High precision parallax collecting satellite or Hipparcos.  Launched from 1989 to 1993 by the European Space Agency, this has taken measurements for the parallax of just about 100,000 stars.  The next space telescope launched in 1990 was the famous Hubble Space Telescope.  It has shown parts of space unknown to us with the most detail ever seen.  It actually had an imperfection with the mirror, which was eventually repaired, but that’s why we like our radio telescopes here on the ground.  Speaking of that telescopes on the ground, there are still many that are made for use on Earth.  An example would be the Very Large Telescope or VLT.  It is indeed large,  four reflecting telescopes each with a mirror 8.2 meters in diameter.  It was set up in 1999 in the Atacama Desert of Chile since that would allow for far better observations than near a city with pollution (both light and air).  To show how useful it was, it was the reason scientists can show stars around the supermassive black hole at the center of the Milky Way and revealing the first exoplanet to be discovered.

Another major space telescope was the Chandra X-ray Observatory, searching the skies as of 1999.  This marvel launched by NASA has searched the skies in the X-ray range to show a variety of objects, such as a pulsar in the Crab Nebula.  Yet another major space telescope was the Spitzer Space Telescope, launched by NASA in 2003.  It has imaged a variety of objects in the infrared range.  The next space observatory to be launched was Kepler.  As we said, Kepler had a satellite named after him for being awesome, and his namesake has been searching the skies for exoplanets since 2009, finding over 2,000 candidates, with about 200 being similar to Earth.  Another notable space telescope which hasn’t been launched yet is the James Webb Space Telescope, being launched by NASA in 2018 as Hubble’s successor.  For comparison, Hubble had a 2.4 meter mirror and Spitzer an 85 cm mirror, while the James Webb will have an 8 mirror meter optimized for infrared observations, so it should be able to show a whole new perspective of space.

See Explanation.  Clicking on the picture will download the highest resolution version available.

M1. See, the Messier catalog is helpful, and so are space telescopes at giving us a whole new perspective of it. From: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP) at NASA’s astronomy picture of the day (apod)


TL;DR — This was quite a bit of history to discuss.  But it is Astronomy, so there is certainly more.  This was to give an overview of the vocabulary, people, and Astronomy in general.  Now we can explore even deeper into the Universe and how it works.  But what is expected in Astronomy and what are the problems after looking at all these people?  It is:

1. Astronomy is really awesome, it can relate to anyone’s imagination.  It is so abstract and great to write, talk, or think about since it is discusses the skies and stars, we can’t reach it yet, but it shows how most subjects can be tied together.  It can even be useful with a variety of satellite or material technologies developed.

2. Astronomers do the work, it’s not often that a eureka moment occurs as much as data, predictions, and models are created to show a probable event either before or after collecting data for it.  It may not sound as exciting, but it actually is more amazing to be able to do that if you think about it.

3. Dark matter, dark energy, quasars, black holes, and many objects even within our own solar system still are not completely understood.

4. Lots Of Acronyms. Or LOA.


For more on this go to: http://heasarc.gsfc.nasa.gov/docs/heasarc/headates/1900.html





1900’s-Today: Modern Astronomy, the people, the problems

Now that we have been moving so fast across time, perhaps things will appear to start going slower (hopefully explained in a future relativity post).  The 1900’s has created a lot of mind-blowing problems to discuss in our interpretation of the Universe.  We’ll get into the whole shabang from the Big Bang to now, but the amount of information to cover from the 1900’s to now cannot really be covered in one post, since such a massive amount did happen.  Luckily, not enough to ignite fusion.  So we split the 1900’s, perhaps by fission, into three parts.

General discoveries of principles:

Sir James Jeans and Lord Rayleigh developed the Rayleigh-Jeans Law, of course.  Rayleigh in 1900 and Jeans in 1905 attempted to predict the relationship between wavelength and temperature for blackbodies.  This worked with high wavelengths, but failed catastrophically when it got to lower wavelengths because it showed something called the “Ultraviolet catastrophe.”  No, this doesn’t mean Ultraviolet rays were predicted to cause some major problem for humans, but it did show that by Ultraviolet or lower wavelengths the energy should be infinite.  With that logic, rays from the Sun or any star should have infinite energy, which is untrue, because then there would be infinite energy in the Universe and spectroscopic data would show infinite temperatures for stars.  Oh, also the Earth or any planet wouldn’t be habitable.  Most of these statements contradict the data we have (and the fact that we are still alive).  Still, another step for science.

To continue from the work of Balmer and all the other people who developed spectroscopy there are two other notables.  They are Theodore Lyman and Friedrich Paschen.  They both found spectral lines for the emission spectrum of Hydrogen at different wavelengths.  Lyman found it in UV wavelengths.  Paschen, presumably a passionate man, found the lines in the infrared wavelength.  Hot stuff!  

To continue from Pickering and his “computers” there are three other extremely important women in Astronomy to discuss.  The first is Antonia Maury, who created an early catalog of stellar spectra to help classify them.  Unfortunately, her explanation of the different spectral line widths wasn’t liked by Pickering, so she took a leave for almost 10 years.  She did come back and analyze the spectral lines of the binary star Beta Lyrae,  but she may deserve more credit than it sounds since Ejnar Hertzsprung found value in her work for identifying giant and dwarf stars.  Henrietta Swan Leavitt cataloged over 2,000 Cepheid variables, half of the known amount during the time.  She also developed the period-luminosity relationship, which was used by Hubble and many others as a method of calculating how far a Cepheid was by comparing its apparent magnitude to the absolute magnitude corresponding to its period.  That is up there with one of the most important discoveries in Astronomy and distance calculation.  Lastly, there is Annie Jump Cannon.  She improved upon the theory of stellar spectra.  She created the mnemonic “Oh Be A Fine Girl, Kiss Me”, showing the stellar classes O, B, A, F, G, K, M.  Again, still used and very important.  Sadly, the three women weren’t given all the credit they deserved at the time, and the same went for pay.

“Computers” possibly as important as the computers we use to make this post or to read it with

No Astronomy history discussion is complete without Edwin Hubble.  They say he could have either been an amazing boxer or basketball player, but instead he went into Astronomy.  This is why we make the tough decisions in life.  At the time the latest technology was photographic plates, which had to be examined manually.  But using them he found many Cepheid variables, and he proved they were outside our galaxy using distance calculations courtesy of Leavitt.  He also classified a variety of galaxies, and he found that they were different in distance, shape, and brightness.  This is called the Hubble tuning fork since it looks like a tuning fork, and it doesn’t just sound good, it works well enough to still be used.  The most famous of his discoveries is calculating Hubble’s Law in 1929 by looking at the redshift of other galaxies and calculating how fast away things are moving relative to us.  Using this he was able to create an estimate for the age of the universe, and he showed it was expanding.  Besides being famous, he also gets a very nice telescope which showed us such detailed photos that they can almost let us look back in time by looking into the far edge of the universe (our background happens to be part of the Hubble Ultra Deep Field).

Ejnar Hertzsprung and Henry Norris Russell are known mostly for developing the Hertzsprung-Russell or H-R Diagram.  This will certainly be discussed in another post since besides showing Astronomers’ love of relationships (they are quite romantic), it visually links luminosity, mass, radius, spectral type, stellar evolution, and most qualities we can tell about a star.  Hertzsprung used Leavitt’s work on Cepheids and checked it with parallax to calibrate the relationship.  With work put into stellar classes, he found stars had different qualities and stellar evolution could be linked.  He also used Maury’s work to show color-magnitude diagrams that link width in stellar spectra to density and size.  Russell’s major contribution is the stellar evolution part. With Heinrich Vogt, he showed that mass and chemical composition, but essentially mass, determine the evolution of a star.  In general, Russell introduced much of atomic physics to Astronomy which helped develop astrophysics.

Arthur Eddington is known for many things.  To start he theorized the interior of stars and in 1914 explained how Cepheid variables pulsate.  He also found the Eddington Luminosity,  showing the luminosity of a star while it is in hydrostatic equilibrium, which is when the radiation pressure outwards matches gravitational attraction of mass inwards.  This means he would of course by 1924 explain the mass-luminosity relationship showing that mass and luminosity produced by a star are related.  Eddington also used a Solar eclipse to prove that light is bent from the Sun, major evidence of relativity.  He may have need some of his derivations corrected and tried mistakenly correcting others sometimes, but within 10 years he made three extremely important discoveries to Astronomy.  We do try to explain things well in this blog, but to quote Eddington himself, “Not only is the universe stranger than we imagine, it is stranger than we can imagine.”

Yes, light bends. Also, relativity confuses you and us. Either way, the Solar eclipse is cool.

When we mentioned that Eddington incorrectly argued against other people, mainly we are talking about Subrahmanyan Chandrasekhar.  He is mostly known for the Chandrasekhar limit (1.44 solar masses), which explains the mass limit for white dwarfs.  It also explains how type Ia supernovae are created.  So this discovery was of course criticized by Eddington, who didn’t believe pure mathematical derivation could describe something as massive as a star, especially when it involved quantum mechanics which were not completely understood.  But Chandrasekhar was right in the end, and he even has the Chandra X-Ray Observatory named after him.

Next we shall tune in to Karl Guthe Jansky, the main person to develop radio Astronomy.  By detecting radio waves from the Milky Way Galaxy he showed that a giant dish could be used to detect a variety of objects.  Radio Astronomy has revealed many astronomical objects, since energy can be radiated in all different parts of the electromagnetic spectrum.  It can also be used to detect and calibrate distances, so it is a truly top-notch, or should we say large wavelength, discovery.  Bell Labs should also be noted since not only did Jansky make his discovery there, but much of modern technology was developed there.  He gets all sorts of radio Astronomy-related things named after him, from a unit to a prize.

Jansky’s method of radio Astronomy, not a fancy dish, but it does the job

It may be as confusing as relativity at times, but it has to be mentioned (in fact, it even conflicts with general relativity, which shows how the universe is just confusing).  Everything in science must be approached, so we shall look at the development of Quantum mechanics.  Some main people would be Max Planck, Albert Einstein, Erwin Schrodinger, J. Robert Oppenheimer, Richard Feynman and Werner Heisenberg, in no particular order.  Quantum mechanics shows how particles interact, how light seems to be both a wave and a particle, how classical explanations of physics don’t work on a quantum scale, how position and momentum cannot be both determined at the same time, and pretty much showing how we can always screw with physics just a bit more.  Of course, it isn’t all about cats, so how does this relate to Astronomy?  For one it solved problems like how Wien’s Law and the Rayleigh-Jeans Laws didn’t work, because Planck came along and decided that it isn’t an ultraviolet catastrophe.  In general, theories about stars eventually involve things on an atomic scale, so quantum forces should be considered in how a star forms or how light travels.

Another thing to mention is that by this point we still weren’t totally sure where light from the Sun, and stars in general, came from.    Luckily, we have a whole slew of scientists to thank for figuring this one out.  To start we have F. W. Atson who developed measurements of atoms; his work was used by Eddington to theorize fusion.  Next Hans Bethe, who is given the most credit, gave greater proof that Hydrogen fused into Helium to create enough energy to light up the Sun.  But there is still more.  Since stars have different compositions someone, namely Carl Friedrich Freiherr von Weizsäcker, showed that carbon, nitrogen, and oxygen are involved in fusion for higher mass stars.  Last to note was some heavy news from Fred Hoyle who said that iron can’t fuse into heavier elements, even with such high energies.

Basically, they explained this.

Another person on this long list is Walter Baade.  He looked to the stars, so much so that he found that there were differences between Cepheid variables.  This is linked with the discovery of stellar populations (that he also discovered), that a star’s age affects its composition and overall older and newer stars can be differentiated.  With this, he found that certain Cepheid had different periods, which would change most calculations done before the time that used the variable stars to calibrate distances.  This is why Astronomers must always check their work.

If one read the “Preparing for Competition” part of this blog one may have noticed a certain statement about Swiss Cheese.  But a more important Swiss Astronomer is Fritz Zwicky.  With Walter Baade he coined the term “supernova”, was the first to theorize neutron stars, and proposed that Type Ia supernovae could be used as a “standard candle.”  What this means is that these supernovae can be used to map out extremely large distances because they are all very similar.  Zwicky did work on a galactic scale, literally, since he did work about galaxies, their size, and their mass.  Knowing from Einstein that light mass can bend light he discovered gravitational lensing with galaxies in 1937, which means that we can sometimes see behind galaxies or show that we may have distortions in our views of galaxies.  But even with this he still has his most famous discovery of dark matter.  You know, the other thing they are looking for over at CERN.  Zwicky used something called the virial theorem to show that there is certain mass in galaxies that can’t be seen.  It’s pretty important considering it could make up more of the universe than the regular matter we are made of.

The Coma Cluster, used by Zwicky for finding dark matter. For being called a coma it surely made Astronomers more awake.

With discoveries about galaxies comes another woman, Vera Rubin.  Despite being denied to Princeton, she was able to go to Cornell to gain a higher level degree in her passion of Astronomy.  After trying to decide on a topic, she took to galaxy rotation rates.  It was expected that similar to our own Solar System, the rotation rates would be slower on the outside of the disk of the galaxy than the center.  But after taking spectroscopic data she and her adviser, Kent Ford, found that the edges of galaxies rotated pretty much as fast as the center.  At first it was surprising, but after looking at other galaxies and at the observations made by Zwicky she found further evidence for dark matter.

Chushiro Hayashi was a Japanese astrophysicist, so we know he did something awesome.  He made a contribution to the Alpher-Bethe-Gamow or αβγ paper, which showed how elements were created in the Big Bang and which ones would be more abundant.  He showed that something called electron-positron pairs, which were present in the early universe, should be taken into account.  This led to a more accurate proportion of the presence of elements like Helium.  But besides this his more eponymous discoveries are the Hayashi track and Hayashi contraction, which shows that the evolution of protostars, or stars that are just beginning to develop (not necessarily as cute as babies sadly), can be plotted on an H-R diagram.  The Hayashi contraction itself is when a protostar condenses into a main sequence star;  he showed the temperature at which protostars would maintain hydrostatic equilibrium.

1800-1900: Developing a New Understanding of Physics in Astronomy

After a large amount of data, theorizing, and screwing with physics we come to the 1800’s.  Here we bring further data/discoveries, but we also come to a point where physics starts to really become confusing.  Especially when we throw in calculus because, well, it’s integral.  The advent of spectroscopy and discoveries about Optics shed light on many aspects of stars and Astronomy.  Lastly, there were some shocking aspects of electricity and magnetism that had to be looked into.

To start we still have the Herschel family.  William Herschel’s son, John Herschel, was a prominent Astronomer in his own respect.  He wrote about chemicals and photography in 1819, and in 1822 he published a minor work on calculating eclipses of the moon.  But more importantly, Herschel worked with double or binary stars.  He made a whole catalog of them (taken from his father’s work on calculating parallax), and also studied the common center of gravity for a binary system.  One of his most important discoveries was that a force coming from the Sun seemed to be acting on Halley’s Comet, leading to the discovery of solar winds.  After this foray into Astronomy, Herschel continued his work with photography.  He is never actually recognized as its inventor, but he did coin the word “photograph” in 1839.

From all the results of John Herschel’s work on photography, someone had to go and use it.  That man would be Henry Draper.  In 1880, he took the first picture of a nebula (the Orion nebula to be exact).  His overall contribution to Astronomy is improving upon astronomical photography and combining this with photographing stellar spectra.  This was essential to the fantastic vistas provided today; the banner on the top of this blog wouldn’t exist if it wasn’t for the many great high-quality photos of nebulae.

We can now go closer (let’s call this a blueshift) to Christian Doppler.  Usually, he is noted for discovering the Doppler principle/effect/shift, but he’s most notable for that since he didn’t do too much more.  Some of the things he found about it were actually incorrect, but nonetheless, it was an extremely important principle.

Now we will discuss the important discoveries made in spectroscopy during this time.  It really started with Joseph von Fraunhofer in 1814.  He found that dark lines were created when light from a continuous spectrum was absorbed.  Fraunhofer found that light from the Sun had these lines, and by comparing the solar spectra to lines created by gaseous elements, he showed that the Sun was really a hot sphere of gases.  About 50-60 years later, Gustav Robert Kirchhoff and Robert Wilhelm Bunsen explained the cause of these lines.  Kirchhoff is also known for his work with thermochemistry and thermal emission. From this we go to William Huggins. We are unsure whether he was the most huggable man as his name may suggest, but he developed the technique of spectroscopy to look at the stars and accurately show their composition.  This combined with the Doppler Effect created a fantastic new way to look to stars and their properties.

All the Fraunhofer lines from the Sun, just not on one line since that wouldn’t fit

Hopefully we’ve excited you (like hydrogen electrons), since Johann Jakob Balmer is the next man who worked with the up-and-coming field of spectroscopy.  His main accomplishment is the Balmer series of Hydrogen spectral lines.  This shows that Hydrogen has certain spectral line emissions in the visible wavelength, and they can be calculated.  This is important in connecting measurements of the Doppler effect on an object with spectral lines, or it can show the presence of Hydrogen in an object.  Interestingly, by the time Balmer published his very important papers he was 60, and 72 by the time he finished publishing his work, so it’s never too late to do something great.  In addition to him, it is necessary to mention Johannes Rydberg, who showed that the spectral lines produced by atoms can be related and their energies can be found using a formula he created.  The reason we mention Rydberg is that Balmer created his own formula to show the Balmer series, but it was actually a special case of the Rydberg formula.

There are three last people who did some physics-related nonsense. They are Ludwig Boltzmann, Josef Stefan, and Wilhelm Wien.  This nonsense was all about blackbodies (objects that emit energy “perfectly”) and stars are generally treated as blackbodies.  Stefan showed how to determine the power of the radiation emitted by a blackbody and determined the approximate temperature of the Sun.  Boltzmann, a student of Stefan, showed how this can be found mathematically, and also predicted a variety of atomic properties.  Lastly, there is Wien who developed a law that shows that the wavelength emitted by a blackbody changes with temperature.  Altogether, these people did some hot stuff.

Then there is Williamina Fleming.  She was a housemaid to Edward Pickering until one day Pickering got fed up with his male assistants at the Harvard Observatory, and legend has it, declared that his maid could do a better job.  She did.  Fleming classified over TEN THOUSAND stars according to the strength of their hydrogen spectral lines (this classification would be improved by Annie Jump Cannon in the 1900s).  She also discovered many nebulae, novae, and variable stars, including the famous Horsehead Nebula, but she was denied credit for the discovery.  Fleming was later put in charge of the Harvard Computers, also known as “Pickering’s harem”, a group of women who worked as human computers and made many important discoveries in astronomy.

The Horsehead Nebula. Not that easy to find!

Now that we have gotten past a majority of the physicists there was still work being done with distances and planets.

Friedrich Bessel is credited with observing over 3,000 stars, but more importantly, he was one of the first people to use parallax to find the distance to a star.  Parallax is possibly one of the most useful tools in any Astronomer’s arsenal since it is so simple to use, and so important that it will be explained separately in a later post.

Johann Gottfried Galle is next mentioned mainly because he found Neptune using data from Urbain LeVerrier (who may be more important since he also predicted its orbit), but it is nonetheless the last planet of our Solar system.  He also found and studied  414 comets and a crater on the moon.  For this, Galle has a ring of Neptune named for him.  On the subject of Neptune, it is also worthy to mention William Lassell, who discovered Neptune’s largest moon Triton.

To continue with the moon-discovering, Asaph Hall found Mars’ moons Phobos and Deimos, named for gods of fear and terror.  But the only thing that’s scary in this situation is why it took so long.  This is because these moons are REALLY small, as in only a few kilometers across.  Besides this, Hall found the orbits of satellites for other planets, double stars, the rotation of Saturn, and the mass of Mars.

The last thing to mention would be the Yerkes Observatory in Chicago, made in 1897.  It was a giant refracting telescope, able to take vast collections of photographic plates.   This is considered almost a transition to modern Astronomy, because the telescope was state-of-the-art technology and could be used to get the best and brightest photos of space.

The telescope at the Yerkes Observatory. A person doesn’t look like much compared to it!

Other people to mention:

  • Samuel Heinrich Schwabe – Effectively found the sunspot cycle
  • James Clerk Maxwell – One of the most famous physicists of the 1800’s, best known for his equations involving electricity, light, and magnetism.  He also predicted Radio waves and explained that Saturn’s rings weren’t solid or fluid, but rather a bunch of small, separate, solid particles.
  • Lord Kelvin and Hermann Von Helmholtz – worked with star formation, created the Kelvin-Helmholtz mechanism to explain how stars produce energy through gravitational collapse

For more you can go to:

1600-1800: Bringing Order to the Heavens

We go to the observatory in France and listen to the stories of science, reaching for the stars.

Thus we continue our exploration of the universe.

A lot can happen in 200 years.  Certainly people know of a variety of revolutions (American, French, etc.) that occurred.  What of science?  Through these years many discoveries are notable in the sciences.  Possibly from Kepler we could call it a Scientific Revolution!

We will split this into the 1600’s and the 1700’s, where we discuss a variety of people.  A majority of the discoveries involve the Solar System, but these years made some stellar improvements to Physics as well.


At this time the telescope was improved by a variety of people, which allowed for a growth in our knowledge of the Solar System and its contents.  Gregory James designed the first reflecting telescope known as the Gregorian telescope.  The first actual refracting (Galilean) telescope was made by the Dutch Hans Lippershey, Zacarias Janssen and Jacob Metius who created lenses.  Refracting telescopes like the ones Galileo made and used were more common and used by ancient Astronomers.  Now reflecting telescopes are used more since it was found eventually that lenses had limitations in viewing objects.  John Flamsteed cataloged over 3000 stars, such an enormous number that the catalog was even needed by Newton and Halley.  There is also Christiaan Huygens, a famous physicist who worked with telescopes and Optics to find Saturn’s rings and its moon Titan.  For this he gets a spacecraft named after him, which  is fittingly supposed to visit Saturn.

Cassini-Huygens spacecraft

Artist’s rendition of Saturn and spacecraft.

Another famous Astronomer who worked with Huygens was Giovanni Domenico Cassini.  The spacecraft that was named for Huygens is actually called the Cassini-Huygens since Cassini also made multiple observations of Saturn and Titan.  He was actually more of an Astronomer than Huygens, since he ended up observing four of Saturn’s moons, discovered the Great Red Spot of Jupiter with Robert Hooke, and found differential rotation in Jupiter’s atmosphere.  Cassini and Jean Richer even managed to use parallax to calculate the distance to Mars, an important use of a method of distance calculation (which will be explained later).

So yes, there were definitely people besides Galileo, Newton, and Kepler who were important during the 1600’s.


But the 1700’s had some extremely important people as well.  One of the most important would be Charles Messier.  By looking at the sky for comets, he found many comet-like objects that weren’t actually comets.  For this he made a catalog of 110 objects, most of which turned out to be nebulae and star clusters.  This catalog could be said to be as important as the telescope since it organizes the objects and explains where they are; that surely puts us in our place!  This list is still used by Astronomers today, especially amateur Astronomers, and for the Science Olympians out there you would know it from some of the Deep Sky Objects.  We have this man to thank for helping make our lives somewhat easier in finding information on them.  Messier sadly doesn’t have any fancy satellites named for him.  He just gets a crater, and a whole catalog of objects with his name tacked on instead.

Entire Messier catalog

^ This whole thing.

Next is Edmond Halley.  Now, we all know about the famous Halley’s Comet.  He got his name attached to one of the world’s most famous comets for calculating the orbit of that very comet.  No easy task since he figured it out by looking to four observations and their calculated orbits that weren’t all his own.  He sadly didn’t see his prediction come true for the comet’s next appearance, but Halley did many other things too.  Similar to Messier, he constructed a catalog of stars of the Southern Hemisphere for 341 stars and observed the transit of Mercury across the Sun.  Halley may have also persuaded Newton to publish some of his works on celestial mechanics.  He also looked towards the famous Transit of Venus to determine the distance from the Sun to the Earth.

Pierre-Simon Laplace was an important mathematician and Astronomer.  He made a lot of math, but this is an Astronomy blog, so we’ll ignore most of his math work.  He restated the “nebular hypothesis” of the origin of the solar system, which pretty much says that a giant cloud of stuff (hydrogen and whatnot) condensed into a star with dust forming the planets as well.  Laplace also was one of the first scientists to theorize black holes and gravitational collapse.  Yes, he theorized black holes almost 100 years before modern physicists did, by working with a man named John Michell who also described gravity’s effects on light.  Of course, Michell himself was one of the first to propose binary stars, so obviously these people were pretty intelligent for their day.

Lastly is the Herschel family.  The family was more known for its music, but there were three famous for Astronomy.  Possibly the most famous is William Herschel.  By reading books on Astronomy and Optics, he learned to become a skilled telescope maker and sky observer by creating mirrors for observation.  Herschel also investigated the proper motion of stars, and from this he discovered that our solar system is moving.  He proposed that other universes exist, hinting at the idea of multiple galaxies.  He’s most well-known for discovering Uranus and two major moons of the planet.  Yes, by 1781 there were still undiscovered planets, but we can thank this man for an inappropriate planet-related joke.  For all this Herschel was able to meet Napoleon (yes, that Napoleon), Laplace, and Messier.  It’s appropriate that Herschel met Messier since Herschel made his own catalog of objects, and in the same year that he discovered Uranus he received a copy of Messier’s catalog which spurred on his interests.  But there isn’t really a better reward than getting a satellite named after you.  Oh wait, Herschel got one of those too. It works in the infrared range. Because he discovered infrared light.

William and Caroline Herschel

P. Fouché. Caroline Herschel Taking Notes as Her Brother William Observes on March 13, 1781, the Night William Discovered Uranus, (Brooklyn Museum)

To continue with his family, he had a sister.  Caroline Herschel was sick with Typhus from a young age.  Despite surviving this she wasn’t able to do much in the opinion of her father since she couldn’t grow any taller.  Since her brother had sympathy for her, she had multiple discussions with him about Astronomy, and eventually she decided to help him.  Caroline made a major contribution to the discovery of Uranus with her brother, but she also did her own observations with a small telescope and found a total of 8 comets in 11 years along with 3 nebulae.  Discovering comets and nebulae may not sound so significant, but many Astronomers at the time (including the notable Messier) were searching for these objects. Caroline Herschel is recognized as the first woman with a scientific position specifically in Astronomy and received a pension for it.  There may be no satellite named directly for her, but she certainly showed that despite not learning as much, she was a capable observational Astronomer.  This is especially unique since she lived in a time where women were expected to be married off and become housewives.

Others to mention:

  • Johann Heinrich Lambert – First to propose Milk Way’s disk-like shape
  • Johann Daniel Titius – Found asteroid belt and with Johann Elert Bode created a law for the distances of planets
  • Giuseppe Piazzi – Discovered the dwarf planet Ceres and has a crater named for him
  • Heinrich Wilhelm Matthias Olbers – Calculated comet orbits, discovered asteroids and proposed the existence of the asteroid belt.  Most famous for Olbers’ Paradox, which states that since the night sky is dark, the universe and the number of stars in it cannot be infinite and static.  This contributes to support of the Big Bang model that the universe is always changing.
  • Ole Rømer – had to be mentioned both for the fancy O and for measuring the speed of light, which was improved on by James Bradley
  • Leonhard Euler  Said incorrectly that light must travel through an “aether”.  But to make up for this, he calculated the orbits of comets, the parallax of the Sun, and tons of other useful math (or maths for our British readers).  Also, his last name is pronounced similar to “Oyler” or “Oiler”, please don’t make the mistake.  A Geometry or math(s) teacher may be mad if you do.
  • Alexander von Humboldt – first detailed study of Leonid Meteor Shower

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Kepler’s Laws

Tycho Brahe was a man with an awesome moustache:

Evidence he was a man with an awesome moustache, possibly a crazy, crazy man

Despite this, this post is titled “Kepler’s Laws” since Brahe’s version of the Solar System is both confusing and wrong, but he did have one.  So, we will give him credit for creating the data used by Johannes Kepler (Brahe’s assistant, shown below), who found some fascinating aspects in the orbits of planets in our Solar System.  Kepler was given the task of understanding the orbit of Mars by Brahe†, but little did Brahe know, Kepler would be making some laws now, and they are quite eccentric.

A man also with a moustache (obviously it helps with Astronomy), but maybe the beard helped make him slightly less crazy than Brahe

Before we go into Kepler’s laws a major aspect of them is the ellipse.  These have a few important properties, essentially being non-perfect circles.  The more “ellipse-like” and unequally round an ellipse is, the more eccentric it is,  going from zero (a circle, a special kind of ellipse) to one (a parabola, not an ellipse).  The orbits of bodies around stars tend to be elliptical, since it is difficult to make things perfectly circular in nature.  Interestingly, the orbits of planets in our Solar System are oddly less elliptical than orbits normally would be.  Confusingly, this would then be called “less eccentric”.  Another aspect of ellipses is the major and minor axes, the major being longer than the minor.

There are three laws of Planetary Motion.

1. The ellipses:

Kepler noticed that Copernicus had planets which had circular orbits  with epicycles, both of which made no sense compared to the models he constructed.  With work, Kepler found that the orbits were actually ellipses, with planets orbiting around the Sun at one focus, as shown below.

2. The perihelion and aphelion:

Kepler next found that the area created over equal times between a planet and the Sun is equal around the ellipse.  A planet moves faster near perihelion (when it is closest to the Sun) and slower near aphelion (when it is furthest from the Sun).  This is shown below, greatly exaggerated:

3. A relation forms:

Lastly, the ratio of the squares of the revolutionary periods for two planets is equal to the ratio of the cubes of their semimajor axes.  Far easier shown is: 

where the 1 to the bottom right of the letter represents the quantities for one planet, and the 2 to the bottom right of the same letter represents the quantities for the second planet.  P is revolutionary period, and R is the semimajor axis or half the major axis of the ellipse.

To conclude, the man is quite important.  It is incredibly impressive that he could create highly accurate laws describing large bodies without even technically using a telescope (he used Brahe’s data from sextant observations), such that it can be taught in schools. It may not sound good that there is more to test on because of him, but it is better than  keeping presumptions that create inaccuracies in our interpretation of the universe.  Now it may not seem as necessary, since we can take far better images of space, but whenever Astronomers try to look into space, a model or predictions are made (good science requires hypothesizing and planning).  Kepler’s Laws can be used to check a model of ANY TWO ORBITING BODIES.  He is so respected he even has a satellite named for him looking for planets outside our Solar System.


† Luckily for Kepler and modern astronomy, Mars has one of the most eccentric orbits in the Solar System.


TL;DR — After looking towards the Copernican Model and using Brahe’s data, Kepler was able to greatly help Astronomy with his three laws of Planetary Motions, which help for explaining motions of any two orbiting bodies.  Essentially, instead of circles, he found that planets revolve around the Sun in an ellipse, and he made certain relations from this.

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A Brief History of Astronomy

It’s a warm summer evening in ancient Greece. You stare up at the stars, noticing that they appear to move together across the sky, but there are a few pesky “wandering” stars that seem to have changed their positions since your last observations a few nights ago…

Thus began the scientific study of astronomy.

Plato hypothesized that all celestial bodies moved at constant rates in circular orbits around the Earth — a geocentric universe. The stars were attached to a huge, rotating “celestial sphere”. This agreed with observations that stars always remained in the same place relative to each other.†  However, the retrograde motion of planets (i.e. they appeared to move backwards) threw a bit of a wrench into the works. Originally it was suggested that each planet simply orbited the Earth on a sphere of its own, much like the fixed stars did, but this model just didn’t match up with observations. Hipparchus fixed the problem temporarily by suggesting that each planet orbited on a deferent and also moved on an epicycle, but his model became more and more inaccurate as time went on. Ptolemy further complicated matters by moving Earth away from the exact center of the deferents and adding equants which the epicycles would orbit at a uniform speed…

Ptolemaic Model

A planet moves on an epicycle (small circle) along a deferent (aka “orbit”, the big circle). The epicycle revolves around the equant (black dot), while Earth is offset from the center of the orbit (x).

He wasn’t right either, but his geocentric theory was accepted for nearly the next 2000 years without much complaint — whenever observations disagreed with the Ptolemaic model, the model was “fixed” by adding more circles in order to better match the data (it eventually required 80+ circles).

The Greek astronomer Aristarchus proposed a heliocentric universe at some point around 250 BC, but no one really supported him and heliocentrism was basically consigned to the junkyard of scientific ideas until Nicolaus Copernicus came along in the 1500s. Annoyed by the complexity of the Ptolemaic model and all its circles, Copernicus suggested that a heliocentric model would make everything much less complicated. In the Copernican model, all the planets orbited the Sun in perfect circles — while this model explained many old problems (including retrograde motion), it too had to use epicycles to make theory agree with actual observations. Copernicus knew that his theory disagreed with the geocentric teachings of the powerful Catholic Church, so he waited until the end of his life to formally publish his findings in a book titled Revolutions.

Retrograde Motion

The Copernican Model provided an easy explanation for retrograde motion (Earth is green, Mars is red).

Nearly a century later, Galileo published Dialogue, which compared the geocentric and heliocentric models in a mock philosophical debate, with heliocentrism undoubtedly coming out on top. The Catholic Church was understandably ticked off at Galileo for publishing this (and he had already published other works contradicting Church teachings), so they convicted him of heresy and sentenced him to house arrest to shut him up. Around the same time, Johannes Kepler used data collected by Tycho Brahe to formulate his three Laws of Planetary Motion, which really did make everything MUCH simpler. However, one casualty of Kepler’s Laws was the idea that planets orbited in perfect circles — instead, he discovered that they revolved around the sun in ellipses. How revolutionary!


† We now know that’s exactly not true, because stars move through space more or less independently of each other, but the effect wouldn’t have been noticeable to the Ancient Greeks.


TL;DR — The Greeks proposed a geocentric model of the universe based on what they observed, and basically everyone agreed with geocentrism until the model became ridiculously complicated in order to fit the data. Copernicus found that heliocentrism was a much more elegant solution; other scientists like Galileo and Kepler supported the Copernican Model in both their writings and their work.