Why the Neutron Star Collision was an Important Observation

I am going to take a moment to actually talk about astrophysics (I know, it's a shock! To actually talk about what I do).

Back on August 17th the LIGO gravity wave observatory detected gravity waves from the collision of two neutron stars. This was quickly followed by the detection of a gamma ray burst by the Fermi space telescope, and then a host of other observations from other telescopes. This event quickly became the most heavily observed single event in astronomy. There are several good general reviews of what happened that are very accessible to the average reader (NY Times, NPR, Veritasium, and one more in depth from Phys.org, there is also a whole webpage about the detection with links to many papers).

So I won't go over the basics because you can get that from other sources, but I will talk about some of the more technical implications to the detection.

First, gold. Gold is very important in astronomy because it is very heavy and hard to make. Usually astronomers ignore the different types of elements, we are usually only concerned about hydrogen and helium. There is a joke in astronomy that the astronomer's periodic table of elements is the simplest one since we only have three elements, hydrogen, helium, and "metals". We refer to everything that is not hydrogen and helium and metals (that includes decidedly non-metallic elements like nitrogen, oxygen, carbon, and neon). It keeps things simple.

But when it comes to metals we are concerned with what we call metallicity, that is the relative amount of metals compared to hydrogen and helium. Because hydrogen and helium make up a combined 98% of the mass of the universe, on a cosmological scale everything else is just a rounding error. But on smaller scales (small, as in the size of a cluster of galaxies) the amount of metals becomes important. Except for a tiny amount of lithium, everything that is not hydrogen and helium was produced inside stars, one way or another.

When a star goes through its life cycle it will return a significant amount of mass back into the interstellar medium in the form of stellar winds. For a large star with an initial mass of 10-20 times the mass of the sun, the star may return 80-90% of its mass to the interstellar medium in the form of stellar winds, or a nova or even a supernova. So while a star may start out as almost entirely hydrogen and helium when it forms, the gas that returns to the interstellar medium will be slightly enriched with metals, that is, the metallicity will go up. This enriched gas that has been returned to the interstellar medium will go on to form a second generation of stars, which will still be almost entirely hydrogen and helium, but now with a tiny fraction more of metals. The process will repeat, and each time it does the gas will become more enriched with metals. In order to have enough metals that rocky planets such as the earth can form the gas must go through at least 20 star formation and enrichment cycles. To date, the highest metallicity ever observed in a star is about three times the metallicity of the sun.

Because of something called the nucleon binding energy only elements up to iron can be produced in the conventional way inside of stars. Anything heavier than iron needs to be produced in another way because it is en endothermic reaction and requires huge amounts of energy. Some heavy elements are produced in supernovas but there is a subtle problem with that. While there certainly is enough energy in a supernova explosion to produce the heavier elements, most of the mass that is blown off in a supernova is hydrogen. It would take an immense amount of energy and a string of complex, and highly improbably reactions to convert that much hydrogen into elements as heavy as gold and lead.

In nuclear physics there are two processes which can produce heavier elements, named the r-process and the s-process (unimaginatively the r and s stand for rapid and slow respectively). The s-process takes less energy and a much lower neutron flux, and can happen over long time scales. In the s-process heavy elements are built up slowly one neutron at a time, and allows for neutrons to decay into protons.

The r-process requires huge amounts of energy, and a truly astronomical neutron flux. A parent element is bombarded with a huge number of neutrons to make an extremely unstable isotope. The only thing keeping it from decaying into smaller elements is the rate at which neutrons are bombarding the nucleus. While a supernova has enough energy for the r-process, there is a distinct lack of neutrons to achieve the neutron flux necessary for the r-process to take place. It does happen, just not at a high enough rate to explain the amount of gold, lead, uranium, and other really heavy elements we observe in the universe. So while normal stellar processes can explain the carbon, oxygen, and nitrogen we see, and novas and supernovas can explain the amount of aluminum, iron, nickle, and zinc we see, neither of those can explain the amount of gold, silver, lead, and uranium we see.

This is where merging neutron stars come in. In the collision there certainly is enough energy for the nucleosynthesis to take place, and because there are two massive sources of neutrons being ripped apart, the problem of meeting the minimum neutron flux is solved. But up until now we had no hard confirmation of neutron star mergers, much less finding evidence of r-process production of heavy elements. It has been suspected for years, but only with the LIGO detection and the followup observations of the nova remnant has this been confirmed. With the detection of r-process reactions in the remnant of the merger we can now conclude that almost all of the gold, uranium and other very heavy elements come from neutron star mergers.

Below is an updated periodic table of elements that shows where each element comes from. Some come from more than one source, but you can see just how many elements were detected in the neutron star merger. The purple shows elements from neutron star mergers. It is much more than gold. This is why the detected merger was so important. It showed us where many of the heavy elements came from like gold, silver, lead, platinum, iodine, bismuth, tin, uranium, and many more.

From Wikipedia. You can see a larger version here.

For my own research this does not change what I am doing. While most very heavy elements come from neutron star mergers, most metals come from normal stellar process that are already accounted for in my models. The detection of the merger does not change the overall metallicity, but it does slightly change the relative ratios of the different metals. But this change is not significant enough to impact what I do. The overall metallicity is extremely important, but the heavy elements are still too rare to make any difference. This could be more relevant to those who work on rocky planet formation, and also nucleosynthesis in interstellar space. But my work does not get down to that level of refinement. I work on fairly large objects where individual stars, and even supernovas are below the level of my resolution. So while it is exciting, it does not affect my work directly, but at some point someone may provide a slight modification to some of the models that I use that may change a few of the minor outputs.

Science Problems in the Kolob Theorem

A number of people have asked me to expound upon my first and second reviews of the book The Kolob Theorem (KT). I am hesitant to do this because there are many things in the KT that are obviously incorrect to me, but for those who do not spend a good portion of their time studying and learning astronomy then these errors are not so obvious. Thus it may take a bit of explaining, but if you are interested then read on.

[Again a strong note: I will not speak about the theological implications of the Kolob Theorem. This is only to point out that the book uses some very shaky science to establish its claims. I will again point out that this book was not written by an astronomer. There is a reason why no LDS astronomer has written a book like this, and that is because we recognize that we do not know enough about God, or the universe for a book like this to be written.]

The main text of the KT starts on page 24 (at least in the version that I have access to, linked above). There are a few pages of introductory material before, with some pictures and I will get to those, but my analysis starts on page 25.

I will start near the bottom with the quote by Fred Hoyle. First off, Fred Hoyle was a well known astronomer in his day (he is credited with inventing the phrase "the big bang") but between the publication of his book, Frontiers of Astronomy, in 1955 and the publication of the KT in 2005, our understanding of astronomy has changed more in those 50 years than in the previous 200 years. Yes it really has changed that much. So to rely on an astronomy text book published in 1955 to establish a speculative theory in 2005 automatically places the KT on shaky ground.

Quoting Fred Hoyle Dr. Hilton states:

"The stars in the elliptical galaxies and the stars in the nuclei of the spirals are old stars like the stars in the globular clusters. In contrast, the highly luminous blue giants and super giants are young stars. Young stars are found only in the arms of the spirals."

Our theory would require such a distinction, for the stars in the nucleus must be of a celestial type created first and those of the outer regions of a terrestrial or telestial type and created later.

So the structure that Dr. Hilton sets up for his first corollary, that is central to his entire theory, requires older stars created first to be in the center of galaxy with progressively younger stars as you move out from the center. While it is true that there are many old stars in the center of the galaxy, there are also many old (and in some cases older) stars out in the disk of the galaxy away from the center. The question of where stars form, and how many and how fast they form is still a major area of research. But to illustrate the point here are two pictures of galaxies that are actively forming stars in their center regions.

NGC 3079: The center of the galaxy is an active star forming region. The star formation is actually so strong that it is pushing gas from the center out of the disk of the galaxy. Image credit: NASA and G. Cecil (UNC, Chapel Hill).

M 82: This is actually a composite of images taken from three different telescopes. The green-yellow is from the visible light, the blue is X-rays, the red is infrared. The plane of the galaxy goes from bottom left to top right, but the bright red and blue that is perpendicular to it is hot gas that has been blown out of the galaxy from recent star formation in the center. Image credit: NASA/JPL-Caltech/STScI/CXC/UofA/ESA/AURA/JHU.

As can be seen from the above images there is star formation (and A LOT of it) that happens in the center of the galaxy. Despite what Fred Hoyle states, young stars are not only found in the spiral arms of galaxies. There are plenty of young stars there, but there are even more young stars in the center of galaxies, it's just that they are packed closer together and are mixed with more older stars. As a matter of fact the oldest stars that we can track are found in Globular Clusters (such as M 80), which are most definitely not in the galactic center.

Now on to page 26! (Yes, I have only covered one page.)

Dr. Hilton quotes astronomer Joseph Ashbrook to make the case that there is a dense cluster of old stars in the center of the Milky Way. He sates:

"The core of the Milky Way Galaxy would also possess a tightly packed system of ancient, huge stars in the very heart of the galaxy".

Two things here, he quotes Ashbrook, who may have been a great astronomer (and I can detect nothing wrong with anything Dr. Ashbrook says), but the referenced paper comes from 1968, and the title of the paper refers to Andromeda as a "nebula", not a galaxy. I will get to that in a moment. But the main problem here is that Dr. Hilton is confusing the fact that there is a high amount of stellar mass in the center of the galaxy with there being very massive ("huge") stars in the center of the galaxy. At about this point I probably lost about 98% of my readers and your eyes are glazing over. Stay with me.

So what is the difference between a high amount of stellar mass and a high number of massive stars. Let me explain it like this. Consider two groups of people, groups A and B. In group A the total mass of the group is 20,000 lbs. In group B the total mass is 15,000 lbs. Which group is "bigger". Depends on what you mean by "bigger". It turns out that group A is a group of 300 elementary school students, group B is a NFL football team. Which group is "bigger" now that you know that? Overall the school kids are "more massive" than the football players, but taken individually the football players are 2-8 times more massive than the children. So just because there is a lot of mass in a group of people doesn't mean that the individual people are massive. It means that there could be a lot of them.

The same thing with stars. Just because there is a lot of stellar mass (Dr. Hilton quotes the figure of 10% of the total mass of the galaxy) in the center of the Milky Way, doesn't mean that the individual stars are "huge". As a matter of fact, having "huge" stars would actually be detrimental to his theory, because it turns out that the youngest, most recently formed stars are the most massive, while the oldest, slowest burning stars are the smallest. It seems counterintuitive, but this is precisely the type of mistake that Dr. Hilton makes again and again that undermines his theory. So the "ancient" stars cannot be "huge". In fact the oldest stars would probably be about the same size as our sun, just a lot older.

Next Dr. Hilton moves into a black hole and never makes it out. He gives a definition of a black hole as:

"A black hole is defined as a compact energy source of enormous strength of the order of a billion solar masses".

How can I explain how this definition sounds to a professional astronomer. Assume you had had just finished reading an article about an election in England and read that a new prime minister had been appointed. You turn to me and ask, "What does that mean, 'to be appointed prime minister'?" And I respond, "That is when the Pope comes and crowns the prime minster and puts him on the throne of England." There happens to be a British citizen who over hears this who promptly goes into convulsions and runs screaming from the room, yelling something about "Ignorant Americans". As ridiculous as my statement that a prime minister is "appointed" by being crowned by the Pope is, Dr. Hilton's definition of a black hole is just as ridiculous. It's the kind of thing that keeps astronomy professors up at night fearing that their students may go out into the world and give definitions like that. If you want to know what a black hole is try Wikipedia.

When it comes to black holes there are two types. Stellar black holes that have a mass approximately equal to that of the sun, and super massive black holes that have a mass ranging from 1,000,000 to 10,000,000,000 times the mass of the sun (1e6-1e10 M_sun). Stellar mass black holes are all over the place, while super massive black holes are slightly more rare. It is assumed that at the heart of every galaxy, dwarf galaxy, galaxy remnant, compact dwarf galaxy, and ultra compact dwarf galaxy is a super massive black hole. Dr. Hilton later wonders if it is possible that there is a super massive black hole at the center of the Milky Way. Well he doesn't have to wonder since we have already found it! In fact we found it in 1974! (For someone who uses out of date materials he sure missed this one.)

Here is a plot of the orbits of the stars surrounding the Milky Way's central black hole (know as Sagittarius A*):

Source: Wikipedia.

So continuing on, Dr. Hilton tries to tie in the motion of the stars around the central black hole to "rotation" (a key word from the Book of Abraham, he is trying so hard to make the connection, but this isn't going to do it despite his best efforts). He states:

"One measurement of the radial velocities near the nucleus of Galaxy M 84, in the area of Virgo, shows a speed of rotation of 400 kilometers per second at a distance of only 25 light years from the center."

Wow! 400 km/s that sounds fast! For comparison the sun is doing a positively leisurely 220 km/s in its gentle stroll around the Milky Way. But just a second, where did this 400 km/s number come from. These velocities were measured in M84 (also known as NGC 4374) which is about 60 million light years away, i.e. too far to resolve individual stars. So this velocity is more likely a velocity dispersion, that is a difference in velocities averaged over many thousands of stars, this is not the actual velocity of the stars. The max velocity of an individual star is about half of that, so about 200 km/s, which is about how fast the sun is moving. He tries to make something of this much later (chapter 5), but the motions of stars gets very complex, and I'm not going to get into that. Let's just say that you have to distinguish between the motion of individual stars and the motion of the overall galaxy, and sometimes that can be a very tricky thing. Think of the difference between the motion of individual water molecules and the motion of ocean waves. They are not necessarily the same thing.

On page 26 he mentions "Galaxy 87" I assume he means M87, or Messier 87. Messier was the name of an astronomer who spent his time looking at the stars and made a catalog off all the interesting things he saw in his telescope that weren't stars or planets. He made a list 110 "Messier objects" in 1771 that kept interfering with his hunt for comments. Little did he know that he made one of the most important astronomical object catalogs that would define observational astronomy for the next 200 years.

Wow, we are only 3 pages into the text and I already want to quit. I'll mention one more thing.

On page 27 he mentions a star 3000 times the size of the sun. He uses the word size, but fails to understand the fine distinctions he just ran rough shod over. The "3000 times the size of the sun" here obviously refers to physical size, meaning radius, and not mass. There are no stars out there with a mass 3000 times the mass of the sun. Some astrophysicists think that you can get up to 70 or 80 times the mass of the sun, but generally upper cut off value is 40 times the mass of the sun, and those stars are very few and far between. So to have a star that is "3000 times the size of the sun" must refer to physical size, or radius. With stars, it is very tricky to match physical size with mass. They don't always correlate the way you would think. This is another case as I mentioned previously where this is precisely the type of mistake that Dr. Hilton makes again and again that undermines his theory. You see, black holes are the smallest things out there. The vast majority of them are smaller than the earth, and are even smaller than Pluto. It's just that they have a lot of mass in a very small space.

OK to finish off I'll just leave my remaining notes in their raw format. I only got to page 33 (starting on 24) before I gave up and decided that if I went on this post would be way too long.

p. 28 J Ruben Clark quote (concept of galaxy has changed since then, other galaxies were known as extragalactic nebula, other galaxies were still known as extragalactic nebulae until the mid 1950's, and there are even a few references to them in the 1960's. concept of galaxy not pinned down until 1960's.)

p. 29 A galaxy is self gravitating. It's a concept that has it's finer issues.

p. 33 Fred Hoyle again, yes there is dust in the center! Star formation! Lot's of it. Need dust to form stars. No dust, no new stars, it's that simple. Where ever there is dust there are stars forming. Where ever stars are forming there is dust. Dust in the galaxy is a very complex issue. It is no where near as simple as he makes it out to be. There are entire books written on dust in the Interstellar Medium.

Andromeda--How the picture was made--mention false coloring
http://apod.nasa.gov/apod/ap040718.html
http://www.robgendlerastropics.com/M31Page.html
http://www.robgendlerastropics.com/M31Pagegrey.html

Link to false coloring of images.
http://hubblesite.org/gallery/behind_the_pictures/meaning_of_color/

In the end the science issues are so dense and numerous that it is impossible to extract them from the book and from his theory. The only thing to do is to scrap the whole thing and do something else.

References

Joseph Ashbrook, The Nucleus of the Andromeda Nebula, Sky and Telescope, February 1968
Bok and Bok, The Milky Way 5th Edition, Harvard University Press, Cambridge, MA, 1981
Fred Hoyle, Frontiers of Astronomy, New York, Harpers, 1955

Yes I have been neglecting my blog

It is true, I have been neglecting my blog. I have plans for brief reviews of ancient astronomy in the Book of Abraham, more posts about names in the Book of Mormon, and ancient rituals of conversion detailed in the Book of Mormon. But right now my time has been consumed with getting my code to work for my research. The other day I cleaned up two files that I had been working on for some time and I removed all the lines of code that I didn't need. All together I think I removed over 4,000 lines of code. It took me a few days to work through it and determine what I need and what I don't need.

In the meantime I uploaded a video of one of my simulations that I did as a proof of concept. I did this simulation to show my advisor that my fixes to the code are working and that more time should be devoted to the approach that I have been taking. He was impressed.

Here is the description that goes along with the video:

This is a short video that I made of a simulation that was done as a proof of concept. It shows a fractal distribution of density in the center of a star forming galaxy. This simulation is done using the MHD code Athena. The box size covers 1 kpc in each dimension and has a grid size of 128 in each dimension. The star forming region injects mass and energy into the center region of the simulation.

The proof of concept is for a flux fixer that allows the code to handle high kinetic energy situations where the total kinetic energy is a significant fraction of the total energy.

The visualization was done using Paraview.

My Plan

I thought that I should layout my plan for research in the near future. Part of my research for my senior thesis included looking into a way of explaining flat rotation curves without including dark matter as a generating gravitational potential. I was looking into a claim that by using GR the flat rotation curves could be reproduced without including dark matter as a correcting term. While the particular method I looked into had some problems there was one paper that I stumbled across that showed that using GR they could give a slight correction to the rotation curves before they needed to include dark matter.

In conjunction with this there was a paper published by several astronomers giving a correction to the amount of normal baryonic matter present in a galaxy. They did this using surveys of the number of face of galaxies versus the number of edge on galaxies and saw that there was a discrepancy, there were more face on than edge on. Thus they concluded that there must be more dust in the galactic halo than they previously thought. This added another correction to the mass, and the assumed amount of dark matter, in a galaxy.

So my plan is to take all these corrections and add them up and see if it amounts to a significant correction to the amount of dark matter that must be present in a galaxy. If this holds then it will also add a correction to the amount of normal and dark matter in galaxy clusters. This will additionally change everything else.

There is also a theory out there that attempts to explain dark energy in a new way. Essentially the argument goes that we might actually live in a "cosmic bubble" of low density space. If this were true then it would create the illusion of an accelerating universe. So it would be possible to explain what we see in terms of what we already know instead of making an appeal to some unknown type of matter. The idea that lead to the introduction of dark energy was the Copernican idea that the universe is for the most part homogeneous, that is, where we live does not have any unique properties that makes it different from the rest of the universe. This idea continues on with the statement that the universe is homogeneous on a large scale.

But what if there is some local inhomogeneities? This leads me to think of another guiding principle. Always try to explain what we see in terms of what we know, without making an appeal to some unknown stuff with unknown properties. What we know is stronger than what we do not know. A known is (almost) always a better explanation than an unknown. So if we make an assumption that leads us to conclude that there is something unknown governing the universe and determining what we see, then perhaps we need to rethink that assumption or how we are applying that assumption.

So I plan to investigate these things and see if I can't make sense of what we see in terms of what we already know without making an appeal to things unknown.