Well, we are finally back in the observatory after a week at COSPAR 2018. Ok, ok, Pasadena is only about 60 miles away, but for me doing the traffic on the dreaded 210 freeway everyday is just not going to happen, so staying at a hotel in Pasadena is the only way to go. So, lets now talk about more cosmic rays, including the Pevatron at the center of the Milky Way, and some IR photos from new IR camera.
One of the takeaways from COSPAR 2018 for me was the very high energy spectrum that is observed for incoming cosmic rays. There were many interesting presentations on all aspects of space research including planets and solar physic and SETI and galactic chemistry, but it was those presentations on cosmic rays that best fit with my studies at the moment. Hearing about the measurements of the incoming cosmic rays and how that shows that some come from sources within the Milky Way and others, mostly of much higher energy, come from outside our galaxy, was most interesting.
There has been a long suspicion that the most energetic cosmic rays probably originate at the galactic center where the massive black hole might be able to accelerate particles to very high energies. It is true and observations confirm that some cosmic rays originate at the galactic center, but other measurements, like those reported on in the blog post of July 22, 2018, show that very high energy cosmic rays come from outside our galaxy.
One interesting discovery coming from the galactic center is the so called Pevatron. Check out the image below taken from the HESS Collaboration as put to us by an article from astrobites.org.
|The "Pevatron" in the Milky Way center as observed by HESS (Source: Kelly Malone, astrobites.org)|
This is a great time to go over again how cosmic rays from the "Pevatron" and other sources are detected. This discovery was made with HESS gamma ray telescope array located in Namibia. The gamma rays, generated at the source in the Milky Way, travel all the way to Earth, pretty much in straight line of sight paths. When they reach the upper atmosphere they interact with gas molecules and generate a shower of light called Cherenkov radiation. This light is in the visible wavelength range and is picked up by the telescope array. Other space based sensors, like the AMS onboard the ISS, receive and detect the gamma rays directly. Other ground based detectors see the end result of high speed particles, mostly protons, colliding with air molecules in the upper atmosphere and then the resulting shower of decay products and particles are seen on the ground.
|The HESS gamma ray telescope array in Namibia (Source: HESS Collaboration)|
When we consider the energy spectrum of observed cosmic rays we must use exponential notation because of the wide energy range. The so called "Pevatron" observed at the center of the Milky Way has energies measured in petaelectron volts, which is, in scientific notation, equal to units of 10^15 electron volts. Energy in the PeV range is about 1000 times higher than that possible to achieve at the Large Hadron Collider (LHC) at CERN, which can achieve energies up to a dozen or so Tera electron volts (TeV). Yet, the energy of the highest recorded cosmic rays are some 1000 times and even 10,000 times higher up to the exa electron volt (EeV) range. If you have forgotten all of this base 10 nomenclature, you can check out the chart below.
|Powers of Ten and prefixes and common English words (Source: Wikipedia)|
Ok, I hope to do some more physicist wannabe type homework on the physical mechanism involved in accelerating particles to these high energies. We know that these processes are described as following a "power law", which means the number of events declines linearly, on a log-log plot, with the energy; that is the higher the energy, the fewer the number of observed particles. We also know that these same processes that accelerate particles, such as protons, primarily, can also generate gamma rays, so the whole process can be quite complicated and the wide range of energies says that there are probably multiple types of processes generating the cosmic rays.
So, we should have "fun" looking into all of that, but not now. For now, let's review again some more infrared (IR) images taken with a new camera. You may recall that in the previous post of July 21, 2018, an infrared image of this Resident Astronomer was shown, courtesy of the NASA vendor display set up at COSPAR 2018. Well, now after getting excited about doing some IR observing, we have obtained a small IR camera made by Seek Thermal that just attaches to your ordinary cell phone and can take IR images with 156 x 206 pixel resolution. It has a focus knob, but I can't seem to make much use of it.
|This little accessory camera by Seek Thermal takes IR images with 156 x 206 pixel resolution (Source: Palmia Observatory)|
So check out these initial images of the observatory staff. Astronomer Assistant Willow was camera shy and hid and did not want to be photographed. The image of Resident Astronomer Peggy shows her with what almost looks like a "third eye." Hmm, I always knew she was special, but I'm not quite sure what it means. Resident Astronomer Peggy conjectures that the "third eye" is just the result of her wearing glasses up until the photo was taken and we are just seeing the effects of the nose bridge which created its own hotspot. Hmm, ok, maybe so, but I'll just stick to my safe story of her being special!
|Resident Astronomer Peggy in IR using new Seek Thermal camera (Source: Palmia Observatory)|
|Astronomer Assistant Danny in IR using new Seek Thermal cameral (Source: Palmia Observatory)|
|Astronomer Assistant Ruby in IR using new Seek Thermal camera (Source: Palmia Observatory)|
|Resident Astronomer George in IR using new Seek Thermal camera (Source: Palmia Observatory)|
These are the first four images taken with this new tool. It is not clear if we can use this little camera and do any astronomical viewing or not, but at least we can play around with it.