Now the unique results are helping to place the descent of Huygens in a global context, and to investigate the upper layers of Titan’s atmosphere.
This artist’s impression shows the ‘light curve’ produced by a star passing behind Titan, Saturn’s biggest moon. When such occultation events take place, the light from the star is blocked out. Because Titan has a thick atmosphere, the light does not ‘turn off’ straight away. Instead, it drops gradually as the blankets of atmosphere slide in front of the star, as the light-curve drawn here shows. The way the light drops tells astronomers about the atmosphere of Titan. The peak at the centre of the light curve represents the bright flash occurring at the very middle of the occultation. This is due to the fact that Titan’s atmosphere acts as a lens, making the light emitted by the star passing behind converge into a focal point and produce the flash.
Occasionally Titan passes directly in front of a distant star. When it does so, the light from the star is blocked out. Because Titan has a thick atmosphere, the light does not 'turn off' straight away. Instead, it drops gradually as the blankets of atmosphere slide in front of the star. The way the light drops tells astronomers about the atmosphere of Titan.
By pure chance on 14 November 2003, fourteen months before Huygens’ historic descent through Titan's atmosphere, Titan passed in front of two stars, just seven and a half hours apart. Bruno Sicardy, Observatoire de Paris, France, organised expeditions to record the occultations, as such events are called.
The first occultation was visible just after midnight from the Indian Ocean and the southern half of Africa. The second could be seen from Western Europe, the Atlantic Ocean, Northern and Central Americas. Teams of astronomers set up along the occultation tracks.
Sicardy was looking for one observation in particular. "Titan's atmosphere acts like a lens, so at the very middle of the occultation, a bright flash occurs," explains Sicardy. If Titan's atmosphere were a perfectly uniform layer, the central flash would be a pinprick of light, visible only at the very centre of the planet's shadow. However, comparing the results from many telescopes, Sicardy found that the central flash fell across the Earth in a triangular shape.
"It is like the light falling through a glass of water and making bright patterns on the table. The focused light is not perfectly round because the glass is not a perfect lens," says Sicardy. Analysing the shape of the flash showed that Titan’s atmosphere was flattened at the north pole. This was because at the time of the occultation, Titan's south pole was tilted towards the Sun. This warmed the atmosphere there, causing it to rise and move towards the north of the moon, where the atmosphere cooled and sank towards the surface.
There was one other key discovery that the occultation data allowed Sicardy and his team to make. A fast moving, high altitude wind (above 200 kilometres) was blowing around Titan at latitude of 50 degrees north. They estimated that it was moving at 200 metres per second (or 720 kilometres per hour) and would encircle the planet in less than one terrestrial day.
"It is like the jet stream on Earth," says Sicardy, "Furthermore, we told the Huygens team to expect some bumps near 510 kilometres altitude, due to a narrow and sudden temperature variation."
Indeed, Huygens was jolted by exactly such a layer during its 14 January 2005 entry. "A temperature inversion was indeed detected by the accelerometers during entry at this very altitude" says Jean-Pierre Lebreton, Huygens project scientist.
The work does not stop there. Even though the Huygens descent took place almost two years ago, the understanding of its data continues to provide key insights into Titan.
Jean-Pierre Lebreton | alfa
First Juno science results supported by University of Leicester's Jupiter 'forecast'
26.05.2017 | University of Leicester
Measured for the first time: Direction of light waves changed by quantum effect
24.05.2017 | Vienna University of Technology
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy