In recent years there has been increased interest amateur aerospace engineering with more and more individuals thinking it might be fun to give it a try. The CubeSat, originally proposed in 1999, is simply a cubic satellite with each edge only being 10 cm long. They normally contain simple commercial electronics and weigh no more that 1.5 kilo each. Normally they get thrown out of space station or dropped off as part of the payload on a rocket. They can carry a wide variety of scientific equipment (although only one or two at a time) and are perfect both for people wanting to learn about a bit of engineering and also researchers who want to perform simple mass studies in an astrophysical environment.
Chondrites are meteorites that are composed almost completely of rock, rather than metal. To be more specific a chondrite requires a large percentage of its volume to be made of chondrules, round grains made of nonmetallic minerals a few millimetres in diameter which are then completely surrounded and bound by a matrix of grains only a few micrometres in diameter. The abundance of elements within chondrites is very similar to the abundance ratios in the atmosphere of the sun. This leads to the conclusion that the asteroids were formed from the collecting of dust particles in the early solar system, before any of the planets had had a chance to form.
The multijunction solar cells are those with multiple junction connecting n doped and p doped materials. A normal solar cell only has one p-n boundary which electrons are promoted across by the solar radiation and their return is movement of charge which is the electricity. The advantage of multijunction (also known as tandem) solar cells is that they can be designed so each junction is optimised for a different wavelength of light. This means that overall the the solar cell is more efficient over a greater range of wavelengths. Triple-junction solar cells, such as indium-gallium-phosphourous, gallium-arsenic, germanium (InGaP/GaAs/Ge) solar cells are found a particular use in space exploration.
Over a year ago in a weekly roundup I vaguely mentioned the hypothetical particle called the axion. This particle is the end result of a series of theories to explain the possible asymmetry between real and antimatter during interactions of the weak force. The primary search for these particles is the CERN Axion Solar Telescope (CAST) which, as axions are believed to be created in stars, constantly monitors the sun. Using a massive superconducting magnet axions will hopefully be converted into X-rays which can then be much more easily detected. The exact specifications of the telescope are often altered in order to look in different mass and energy ranges. In the most recent data gathering session from 2013 to 2015 they actually repeated a previous search done nearly a decade earlier but now with the sensitivity improved three times over the already considerable amount. The range of interest for this study was between two and seven keV and the count rate was recorded for the various energy X-rays induced by the incoming particles.
Our star is quite unique even if its size and colour are not taken into account. This is because the more we search the universe the more we realise that stars are more likely to form in binary pairs rather than on their own, a fact explained normally through the conservation of angular momentum. There were even suggestions that our Sun may have a partner that comes by in a wide orbit every so often, although this seems questionable at best. Of course, the high population of binary stars means, somewhere in the universe, there’s going to be a planet at least somewhat similar to Earth in one of these systems.
Alfvén waves, named after the man who suggested them in 1942, are waves that exist in conductive fluids. Normally they are talked about when it comes to plasmas but they were originally shown to exist in mercury as this too is a conductive liquid that a magnetic field can permeate. The magnetic field acts as the restoring force for the oscillations that make the Alfvén waves exist in the first place. For an ideal Alfvén wave the particles receive no energy as the wave propagates and this is close enough to being true for a significant amount of the time. However, as the oscillations increase in speed, or the wave decreases in size, it can begin to excite the ions through the production of its own electric and magnetic fields. This naturally results in a loss of energy from the wave and is actually one of the most important mechanisms is solar physics for the transfer of energy from electromagnetic waves to the kinetic energy of particles.
Stars are well known to have magnetic fields surrounding them like many planets do. These magnetic fields are generated due to the movement of the plasma, which is of course charged, inside the star. It is through a series of convection currents that the dynamic action of the plasma keeps going and so the magnetic field remains. As magnetic fields themselves exert forces on plasma this creates a very interesting effect where without a density change the internal pressure of the star can change. This is one of the aspects that makes the modelling of stars as perfect gasses a foolish task. Although it was believed for some time that the swirling plasma must cause the magnetic fields recent observations have shown that even the calmer, static regions of the Sun maintain a magnetic field over them.