5-Mar-2018: World-first air-breathing electric thruster
In a world-first, an ESA-led team has built and fired an electric thruster to ingest scarce air molecules from the top of the atmosphere for propellant, opening the way to satellites flying in very low orbits for years on end.
ESA’s GOCE gravity-mapper flew as low as 250 km for more than four years thanks to an electric thruster that continuously compensated for air drag. However, its working life was limited by the 40 kg of xenon it carried as propellant – once that was exhausted, the mission was over. Replacing onboard propellant with atmospheric molecules would create a new class of satellites able to operate in very low orbits for long periods.
Air-breathing electric thrusters could also be used at the outer fringes of atmospheres of other planets, drawing on the carbon dioxide of Mars, for instance. This project began with a novel design to scoop up air molecules as propellant from the top of Earth’s atmosphere at around 200 km altitude with a typical speed of 7.8 km/s.
An air-breathing engine works by collecting the sparse air at the edge of the atmosphere and compresses it to a point that it becomes thermalized ionized plasma. It then fires out the plasma using an electric charge to achieve thrust. An air breathing thruster could keep a satellite operational for extended periods of time if it only uses the air around it for fuel instead of propellants.
This Air-Breathing Electric Thruster (ABET) does not operate in complete vacuum, but works in low Earth orbit (LEO) – altitude of 2,000 km or less– notes the ESA. At LEO, the air is scarce, but not entirely absent. In fact, there is enough air to cause a drag on spaceships and satellites. This is why there are on-board engines installed on satellites to correct course every time it moves out of position.
7-Mar-2018: A new state of matter created
An international team of physicists have successfully created a “giant atom” and filled it with ordinary atoms, creating a new state of matter termed “Rydberg polarons. These atoms are held together by a weak bond and is created at very cold temperatures.
It uses ideas from two different fields: Bose Einstein Condensation and Rydberg atoms. A BEC (Bose Einstein Condensate) is a liquid-like state of matter that occurs at very low temperatures. A BEC can be perturbed to create excitations which are akin to ripples on a lake. Here, researchers have used a BEC of strontium atoms.
Electrons in an atom move in orbits around the nucleus. A ‘Rydberg atom’ is an atom in which an electron has been kicked out to a very large orbit. These have interesting properties and have been studied for a long time.
In this work, researchers used laser light on a BEC of strontium atoms so that it impinges on one strontium atom at a time. This excites an electron into a large orbit, forming a Rydberg atom. This orbit is large enough to encircle many other strontium atoms inside it.
As the electron moves around many strontium atoms, it generates ripples of the BEC. The Rydberg atom becomes inextricably mixed with these ripples and forms a new super-atom called a ‘Rydberg polaron’.
Our universe is believed to be filled with a mysterious ‘dark matter’ which exerts a gravitational force on other matter. Some theories of dark matter postulate that it is a cosmic Bose Einstein Condensate, perhaps composed of an as-yet-unknown type of particle. If we are indeed living in an invisible all-pervading Bose Einstein Condensate, this experiment can suggest ways to detect it.
30-Nov-2017: China’s DAMPE probe looks for decayed dark matter particles in space
A Chinese satellite which was sent to the skies to look for evidence of the annihilation or decay of dark matter particles in space has detected unexpected and mysterious signals in its measurement of high-energy cosmic rays, bringing scientists closer to proving the existence of the invisible matter. The mysterious dark matter is believed to comprise a quarter of universe.
The satellite, Dark Matter Particle Explorer (DAMPE), also called Wukong or “Monkey King”, has measured more than 3.5 billion cosmic ray particles with the highest energy up to 100 tera-electron-volts (TeV), including 20 million electrons and positrons, with unprecedented high energy resolution, Xinhua reported.
Precise measurement of cosmic rays, especially at the very high energy range, are important for scientists to look for traces of dark matter annihilation or decay, as well as to understand the universe’s most energetic astrophysical phenomena, such as pulsars, active galaxy nuclei and supernova explosions.
Dark matter is one of the great riddles of physics. While normal matter – making up the stars and planets and so on – is understood to account for just four percent of the mass-energy density of the universe, dark matter is believed to make up a quarter, yet its nature is unknown and yet to be detected. Its existence has been postulated through observations of the cosmos and, though elusive, it is key to the formation of the galaxies and structure of the universe.
DAMPE, short for DArk Matter Particle Explorer, was designed to look for clues to support one hypothesis for dark matter, which claims it consists of weakly interacting massive particles, or WIMPs. The idea for DAMPE was to collect the high energy cosmic ray electrons and anti-matter counterpart positrons, which are emitted by phenomena such as supernovae and pulsars.