Hubble ziet extreem ver sterrenstelsel in piepjong heelal

Astronomen hebben met ruimtetelescoop Hubble een sterrenstelsel gevonden dat 480 miljoen jaar na de oerknal al bestond.

Daarmee is het stelsel het verst van ons verwijderde en het vroegst ontstane sterrenstelsel dat we tot nu toe hebben waargenomen. Bijzonder is echter vooral dat het om maar één stelsel gaat. Op basis van eerdere waarnemingen zou je er namelijk minstens een paar verwachten.

Waar het bij dit onderzoek om draait, is de vraag wanneer de eerste sterrenstelsels in ons inmiddels 13,7 miljard jaar oude heelal ontstonden. Om die te beantwoorden, is het van belang om voor allerlei verschillende tijdstippen na de oerknal het aantal stelsels te ‘turven’. Hoeveel sterrenstelsels waren er één miljard jaar na de oerknal? Hoeveel 750 miljoen jaar na de oerknal? Enzovoort.

Een beperking daarbij is dat hoe verder je het verleden in wilt gaan, hoe dieper je het heelal in moet kijken. Dat is een gevolg van het gegeven dat licht tijd nodig heeft om afstanden te overbruggen. Zo heeft zonlicht acht minuten nodig om de aarde te bereiken, met als gevolg dat we de zon zien zoals hij acht minuten geleden was. Kijken we naar de veel verder weg gelegen sterren aan de nachtelijke hemel, dan zien we die zoals ze jaren geleden waren. En willen we het heelal zien zoals het enkele honderden miljoenen jaren na de oerknal was, dan moeten we nóg veel verder kijken; zo ver als nodig is om ervoor te zorgen dat licht dat in de gewenste periode werd uitgezonden ons nu bereikt.

Sterrenkundige Rychard Bouwens van de Universiteit Leiden en collega’s hebben dat laatste gedaan, voor het tijdstip van 480 miljoen jaar na de oerknal. Daartoe lieten ze de Hubble Space Telescope met een in mei 2009 geïnstalleerde infraroodcamera 87 uur naar hetzelfde plekje aan de hemel turen. De reden daarvoor: het gaat hier om objecten op zulke grote afstanden, dat je een extreem lange belichtingstijd nodig hebt om er nog íéts van te kunnen zien. De oogst van deze onderneming, zoals gezegd: één enkel sterrenstelsel. (Tenminste, daar lijkt het op; er is een geschatte kans van 20 procent dat we met iets anders te maken hebben.)

Wat deze vondst interessant maakt, is dat eerdere waarnemingen van 630 miljoen jaar na de oerknal enkele tientallen sterrenstelsels aan het licht brachten, terwijl er voor de periode van 900 tot 1200 miljoen jaar na de oerknal zelfs enkele duizenden zijn gevonden. Oftewel: hoe langer na de oerknal, hoe meer sterrenstelsels. Logisch ook; toen het heelal ontstond, waren er geen sterrenstelsels, enkele miljarden jaren later waren er talloze; in de tussentijd moeten ze dus stukje bij beetje zijn ontstaan. Maar trek je die trend door naar het verleden, dan zou je bij 480 miljoen jaar na de oerknal op zijn minst een paar sterrenstelsels verwachten – niet ééntje-of-misschien-zelfs-geen.

De conclusie die we uit dit gebrek aan sterrenstelsels kunnen trekken: in de periode van 480 miljoen jaar na de oerknal tot enkele honderden miljoenen jaren later ontstonden sterrenstelsels rapper dan verwacht. En: het stelsel dat Bouwens en collega’s hebben gevonden, zou weleens een van de eerste exemplaren van ons heelal kunnen zijn.

Bronnen: Nature, Astronomie.nl
Beeld: G. Illingworth/R. Bouwens/HUDF09 Team/ESA/NASA

How to land humans on an asteroid

AENEA mission patch

 

25 January 2011
After a year of intensive studies, young engineers from Europe faced an unusual but challenging task on the future space exploration: can you safely transport humans to a near-Earth asteroid in an international endeavour?

The virtual mission was called AENEA – Human Exploration of a Near Earth Asteroid – and it came to completion last week during the fifth international Master SEEDS (Space Exploration and Development Systems) event at ESTEC, in Noordwijk, The Netherlands.
ESA supported this academic course to educate young engineers for industries that wish to establish their role in the international space arena.
The day before their presentations, the pupils had the opportunity to visit many of the ESTEC facilities and found the state-of-the-art Concurrent Design Facility particularly relevant to their mission design.  

Their presentations was preceded with an overview of ESA exploration activities – the Lunar Lander, Advanced Reentry Vehicle and Expert – by the head of Transportation and Exploration, Bruno Gardini.
ESA astronaut Frank De Winne, the first European commander of the International Space Station, also took to the stage and presented a well-received overview of his OasISS mission.
It was not an easy task to design a mission to transport humans safely to a near-Earth asteroid, performing extravehicular activities on its surface, scientific experiments and technological tests to extend the scientific knowledge and capabilities in space exploration and utilisation.
“The students have matured over the one-year period and developed a professional capability to handle engineering problems with a system mind”, said the SEEDS Educational Project Manager, Prof. Ernesto Vallerani.
“Now they are prepared to enter the industrial world with specific competences, engaged in advance space activities.”
 

	AENEA presentation ceremony

A multisite study

A number of elements were identified and developed to accomplish AENEA’s overall mission requirements. A few of the elements were studied in detail: mission analysis, robotic system, communications, guidance navigation control, heavy launch vehicles, transportation modules, reaction control cystems and crew habitation systems.
Work on this mission design was performed in each of the three locations (Germany, France and Italy) under the close supervision of their professors and experts from industry as well as academia.
The type of work the students performed was equivalent to pre-Phase-A, leading to the definition of a space infrastructure to support the exploration mission objectives.
 

For the duration of their studies, the students attended preparatory courses in Torino: “Understanding Space: Introduction to Space basic Concepts” and “Learning Space Systems: Fundamentals of Space Engineering”. They undertook an intensive period of preliminary design and subsequently engaged in six months of project work in Toulouse, Bremen and Torino.
Thanks to this course, young and enthusiastic people from Europe have found a role in the international space exploration initiative. Their reinforced engineering skills are needed to develop the space systems and to follow in the footsteps of their older colleagues.
Video feed of the presentation can be seen here.
 bron: esa

New material blocks light from exhibiting diffraction.

By Chris Lee | Last updated about 18 hours ago

NIST

I admit this failing: I am an optics geek, and all things light-related tend to get me... um... excited. But arecent paper in Nature Photonics presented a result that most people will find very startling: researchers have created a material which prevents light from exhibiting diffraction.

Some of you with experience in optics may be thinking that this is nothing special, because you have heard of solitons. For those of you who haven't heard of solitons, let me introduce you to them and then explain why this is not a typical soliton.

The sort of spatial soliton that most people refer to involves a wave that compensates for its own diffraction. The way this works is that the laser light has an intensity profile that is most intense near the center and least intense in the wings. If you send it through a material that is nonlinear, it will face a refractive index that will depend on the light intensity. The result is that the light creates a lens as it moves. The lens focuses the light while the natural diffraction of the light beam causes it to expand. At the right intensity, the two balance out and the light beam continues to move through the material without expanding.

But the size of the light beam that you put into the material is not the same as the light beam that you get out, since it will contract to some diameter that allows the focusing effect to balance diffraction. This size depends on how bright the light field is as well. A bright light field will contract to a smaller diameter than a weaker light field.

How does this differ from the research in the Nature Photonics paper? In the new material that the researchers made, there is no mechanism by which the diffraction is compensated. Instead, the material simply doesn't allow diffraction to occur—we will get to how this occurs later—meaning that the light field can't expand or contract. Indeed, what you put in is exactly what you get out, independent of the light intensity, making this very different from a normal soliton.

Now we get to the difficult part: how does this come about? The material consists of potassium, tantalum, and niobate, along with some impurities of copper and lithium. As the material cools after it is mixed, it creates a bunch of different regions that have slightly different arrangements in their crystalline structure, resulting in nanometer sized regions that have slightly different linear and nonlinear optical responses. The size and order of these regions depends on how fast the mix is cooled, so with some experimentation, the researchers can control the nonlinear optical properties of the material.

The end result is that, for some cooling rates, the researchers create a material that doesn't have any of the expected self focusing because the nonlinear properties vary on too fine a scale. Instead, the way the refractive index changes depends on how fast the brightness of the laser beam changes as we move out from the center of the laser beam—a property referred to as the gradient. Usually, this is very weak, but the random and very fine structure of the ceramic allows this gradient effect to dominate.

The critical thing about the gradient is that, for all normal laser beams, it is independent of the maximum intensity of the laser beam. So, it doesn't matter how intense the laser beam is, it will always form a spatial soliton that is exactly like the input beam.

The question then becomes: what do we use it for? I am not sure that the authors of the paper have a clear idea about this either. They mention possibilities for imaging, because if you focus the light at the entrance of the material, it is still focused on exiting, but I'm not quite sure how this would help. Nevertheless, it is a very cool development, and I suspect that applications will follow.

Nature Photonics, 2011

Bron: http://arstechnica.com/science/news/2011/01/new-material-blocks-light-from-exhibiting-diffraction.ars

Met dank aan lucas pellens en http://www.aquilalommel.tk/

Over de ISS...

Op 15 december 20:09 uur zal om 19:09 GMT (16 december om 01:09 Baikonur tijd), ESA-astronaut Paolo Nespoli vliegen op een Sojoez naar het internationale ruimtestation (ISS) voor een zes maanden durende missie. Het ISS is nu voltooid en ongeveer 50% van het ISS onder druk modules zijn 'made in Europe'. Dit verhaal geeft de huidige status van onze internationale buitenpost op de baan. Meer achtergrond informatie is te vinden op: http://www.esa.int/esaHS/iss.html