Follow up from the untimely ended course Leaving the Solar System.
Please share with anyone interested.
I will provide the answers to questions below with a delay of a few days.
We have talked extensively about the speed of light, how incredibly fast it is, how James Maxwell from his equations realised that it must be a constant and how that inspired Albert Einstein to develop his Special Theory of Relativity.
Here is a novel demonstration of the speed of light, with help of the fastest camera on the planet.
In the lecture Beyond the Visible we discuss how astronomers can observe all parts of the Electro-Magnetic spectrum. The most energetic part of the spectrum is called Gamma radiation. Ernest Rutherford discovered various forms of "radiation" using Uranium as the source. He called two forms "alpha" and "beta" radiation, not knowing what that really was. Shortly thereafter yet another form of radiation was discovered which was then called "gamma" radiation. Watch this excellent explanation of what these forms of radiation are here.
Question: which of these three forms of radiation are EM-radiation and which are particles?
Answer: Alpha and Beta radiation are particles (He nucleus and electron resp.). Gamma radiation is EM radiation. Interesting to note that gamma radiation can only originate from nuclear processes. Electron energy jumps do not give enough energy for gamma ray photons.
The chief lecture we missed, but is there for you to explore is the one on Exoplanets. After reading that lecture do you really want to get your hands dirty with Exoplanet research? Well you and your whanau got time on your hands now anyway. Here is a great tutorial. It looks like the Kepler K2 data download still works, so give it a try to do real science!
Comparing Kepler and TESS
Both missions are designed to find exoplanets with the transit method. But what are the main differences between the Kepler primary mission (2009 – 2013) and TESS (2018 – present)?
Answer: TESS: only bright stars. Observes large part of the sky but only for 27 days per sector. Kepler: has been staring at a small portion of the sky and could also observe faint stars.
In the lecture we haven’t discussed the technique of microlensing in great detail. MOA is a cooperation between Japanese astronomers and Canterbury University which operates a telescope at Mount John near Tekapo. http://www.phys.canterbury.ac.nz/moa/index.html Advantage of the technique is that it works on larger distances than other methods, but the main disadvantage is that it only works on chance alignment.
A good article on this technique can be found here.
Today a very easy question regarding exoplanets (it's Sunday after all :-)).
How many exoplanets?
Using the NASA catalogue what is the current tally of exoplanets found? (link to the catalogue in the handout).
Answer: 4141 confirmed exoplanets as of 29 March. See https://exoplanets.nasa.gov/exoplanet-catalog/
Recently (March 2020) it has been big news reported by ESO that a planet has been found where it rains liquid iron. That must be a very hot planet! What is the name of that planet and which observatory and with which instrument was this discovery made? Follow the link in the handout.
Answer: Planet is WASP-76b, the observatory is the VLT (Very Large Telescope) at Paranal, Chile and the particular instrument is called ESPRESSO.
Travel to the Stars
The last lecture in the course and one of my favourites. Such a pity that we cannot have a face-to-face discussion about this topic. First we discuss the basic physics of space travel, the distances, acceleration needed and how much energy that requires. So how realistic is it to think of travelling to even the nearest stars such as Alpha Cen and Barnard’s star?
An important aspect is to be able to accelerate once in space. Electric propulsion systems are developed for this. A successful example was the Ion engine aboard the DAWN spacecraft that visited asteroid Vesta and dwarf planet Ceres.
Read more about this and other systems in this article and watch this Dawn mission video.
Famous people such as Stephen Hawking and many other scientists believe in the Breakthrough star shot mission.
In the lecture I have discussed the amount of energy required for the lasers that they need. Do you believe this is realistic? Your call.
For more watch this video,
and dig deep if you want with this science paper.
Space Travel and Special Relativity
This is the last paragraph in the course handout. Time dilation as a consequence of the Special Theory of Relativity is often cited as the “solution” for deep space travel. This is then illustrated with the famous Twin Paradox.
You can go a little bit deeper than a coffee table discussion if you read this article in the Scientific American.
A very good discussion about the relativistic effects of a constantly accelerated journey to Alpha Centauri, is in the first 12 minutes of this video made by Professor David Kipping of the Cool Worlds Lab at the Department of Astronomy at Columbia University.
This half hour video takes you much further than Alpha Centauri and also much deeper into the effects of relativity on constant accelerated space travel, but it is really worth it.
Before we finish this blog this weekend let us go back to our memorable lecture Physics of Spectroscopy.
We started with the question what light is. Newton theorised that light are “corpuscles” . Then Eric Young came along and created the double slit experiment. We did that in class with my laser pointer; only one wavelength of light. We discussed that if you use white light (e.g. from the Sun) that you will see bright areas made up of rainbows. This is because this interference effect is slightly different for each wavelength.
Here is a great video on Young’s Experiment by my favourite YouTube channel Veritasium. Young convinced all scientists that we finally had the answer that light is a wave phenomenon. Until Einstein wrote one of four papers in 1905, on the Photo Electric Effect… Haha.
Question: Young’s double slit experiment demonstrates two principal effects of light that give these results. One is about the bending of the light at the edge of each slit and the other creates the bright and dark areas on the wall. Which two effects are that? (Hint: use the link in the handout).
Answer: Bending by diffraction and creating the pattern with interference. See here.
Warp Drive and Aliens: Bryan Gaensler Public Lecture This is the last item in this blog.
Finally, if you have an hour and twenty minutes to spare you can watch this interesting lecture with the above title at the Perimeter Institute.
And with that, ponder what you have learned in this course Leaving the Solar System and go back if you wish to the lectures and handouts on this website.
The immediate future is uncertain and it is doubtful if there will be any courses next school term but the next course to take is Exploring the Milky Way whenever it happens.
Our course program will be updated as soon as we know more. I will then also email participants in this course and those who signed up for either of the courses planned for next term.
Stay safe everybody!