A Cosmic Collision

October 17, 2017
There was an interesting joint announcement today from the LIGO, Virgo, and Fermi telescope teams, and one that will have great value to the astrophysics community. For the first time, all three simultaneously detected a neutron star collision and were able to collect data regarding both its gravitational wave signature and its gamma-ray signature. This new data will provide for interesting new studies on the physics of neutron stars and on the origin of several heavier elements in the Universe.

In our galaxy and in the Universe at large, stars are constantly being formed in various sizes, masses, and temperatures. Each have their own interesting properties and life cycles. As these stars get older, they can shed their outer layers and leave only a dense core of heavy elements in a superheated plasma. If the core is very heavy it can collapse down to a black hole. But if it is a little lighter, then the nuclear repulsion between nuclei can prevent this collapse and instead leave a superdense mass of neutrons. This object is called a neutron star.

In this particular system, located roughly 130 million lightyears away in the Hydra constellation, there were two neutron stars that were orbiting each other. Due to their mass, they were each slowly losing energy to gravitational waves, which in turn caused their orbits to slowly decay and the two massive stars slowly approached each other. Eventually they had lost so much energy that the two neutron stars collided in a violent reaction, and scattered their contents throughout their region of the Universe.

As a result of this collision, both gravitational waves and high energy gamma-rays were sent out into space. Those emissions traveled for 130 million years, before being detected on Earth on August 17, 2017. LIGO and VIRGO used their large interferometers to detect the gravitational waves, while the Fermi telescope detected the gamma rays.

However the collision did not only produce gravitational and electromagnetic emissions. Astronomers pointed their telescopes toward the location of the collision and were able to detect large quantities of heavier elements such as gold, mercury, platinum and uranium. This immediately solves one of the lingering mysteries of astrophysics, as the source of these elements in the galaxy were not known before. Lighter elements are forged in the nuclear fusion reactions inside stars, but these processes are not energetic enough or efficient enough to produce heavier elements in significant quantities. It was previously suspected that neutron stars could be the source, but this one collision has now proven that to be true. It would appear from the early data that neutron star collisions could be the source of more than half of the heavy elements in the Universe!

This is an amazing discovery, and for many astronomers and astrophysicists this will be their career highlight. The data from this collision will likely be analyzed for decades to come, in the same way as the 1987 supernova that is still being studied thirty years later. And it makes this year's selection of the LIGO team has the Nobel Prize recipients even more appropriate!

Congratulations to all of the scientists involved in both the detection of the signal and the subsequent studies and analysis. This is an amazing discovery, and one that will have a significant impact on the future of physics!
 

And The Prize Goes To...

October 3, 2017
The 2017 Nobel Prize in physics was announced today, and as expected it was awarded to Rainer Weiss, Barry Barish, and Kip Thorne their work in developing the LIGO experiment that recently made the first detection of a gravitational wave. The experiment itself was an amazing piece of engineering, and its ability to detect and study gravitational waves is going to make it a very important tool in the future for understanding the Universe.

Just over a century ago Einstein published the general t...
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Nobel Predictions 2017

October 3, 2017
Once again we are at the most important week of the year for the scientific community, the week of the Nobel Prize announcements. This year there are a few serious contenders for the physics prize, and they all involve very interesting fields of research.

The leading candidate for the prize this year is probably the LIGO experiment, which last year detected the first gravitational waves. Since then they have confirmed the detection with two more gravitational waves and just recently detected t...
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The Nobel Prize

October 2, 2017
It is that time of year again - the week of the Nobel Prize announcements!

As usual, there is a significant amount of discussion and debate in the scientific community as to who will receive this year's prizes. And also as so often happens, there is no clear frontrunner for the prize this year.

Before I start making predictions though, I must take a moment to make clear who will not be winning. After last year's predictions I received a few communications from people who were unhappy that their...
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Constraining the Seesaw

September 29, 2017
A few days ago I wrote a brief review of the Seesaw Model of particle physics. Being a theorist, I forgot to mention that the motivation for that review was a new set of results from the experimental community that constrains such models. And so I thought that today I would give a few details on these new results.

In the model I reviewed, known as a Type-I model, each of the species of neutrino that are part of the Standard Model are partnered with a second, very heavy neutrino that provides a...
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The Seesaw Model

September 26, 2017
Neutrinos are very mysterious particles. They do not carry electric or magnetic charge, and so they do not interact very much with anything else. In fact we are constantly being showered with neutrinos from space that fly straight through us without interaction, and in fact straight through the entire Earth without even being slowed down. They are so difficult to detect that the weak nuclear decays that generate them were at first thought to be violating energy and momentum conservation since...
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The End of Cassini

September 15, 2017
After twenty years of studying the planet Saturn, the working life of the Cassini spacecraft will come to an end in the next few hours. On Friday, September 15, 2017 at about 7:55 am EDT, NASA will crash the probe into the surface of Saturn and end its mission.

As far back as the 1980s astronomers from around the world were making plans to send a probe to the gas giant, Saturn. We had already explored both Mars and Venus, and the Voyager probes had made flybys of the outer planets, but Saturn ...
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The HL-LHC

September 14, 2017
As students around the world return to school, or start college, or begin new coursework and training of other kinds, particle physicists are also starting new things in the form of new data runs from the Large Hadron Collider. The LHC has already produced evidence of the Higgs boson, and added further constraints to many other theories of nature. The next data run could easily find evidence of dark matter, dark energy, or even hidden higher dimensions in the Universe.

However the topic of tod...
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Back To School

September 5, 2017

Some loyal readers will recognize this entry as a repeat from the last three years. Each year it gets a good response, and kudos from my readers, and so as before I must appease my loyal followers...

To all the students starting University, enjoy this time of your life. Long ago when I started, a prof told me that this is the start of your real education. Now you get to choose your own courses and your own field of study. It is entirely up to you to decide what to do with this chance.

I know fr...


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Free Software

September 5, 2017
With the arrival of September, students around the world will be returning to classes this week. And for those who are starting out at college or university, one of the most important considerations is how to live on a budget. These are the years when one has little or no income, but must bear the expenses of living independently for the first time. While giving advice on living on a budget is far too expansive to cover in this blog, I can tackle one small aspect of student life by providing ...
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About Me


Dr. Chris Bird I am a theoretical physicist & mathematician, with training in electronics, programming, robotics, and a number of other related fields.

   


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