Spinning matter sends out two types of X-ray.

Spinning matter sends out two types of X-ray.

A powerful jet of plasma shoots out of the black hole 3C273 in this image from the Chandra X-ray telescope.
© NASA/CXC/ SAO/H. Marshall et al.
Black holes spew out X-rays in two distinct ways, astronomers have shown. Being able to separate the components of X-ray signals should help astronomers understand how black holes work.

Scientists had predicted that the jets and disk of matter that surround a black hole would emit different patterns of radiation. But this is the first time that observations of the two types of X-rays have been teased apart.

Black holes are enigmatic beasts. By definition, they cannot be observed directly, as even light cannot escape from their gravitational hold. But astronomers can observe the intense radiation emitted by material as it is sucked into the void. X-rays are the brightest component of that radiation, emitted by matter passing close to the 'event horizon', the point of no return as you approach a black hole.

As dust and gas is sucked into a black hole, it forms a doughnut-shaped disk that swirls around the centre before falling in. Friction heats up the ions and electrons in the disk to around 10,000 °C, generating X-rays in the process.

Although most of the material is ultimately dragged into the black hole, some of it is spat out by the hole's strong magnetic field instead, creating two tight jets pointing in opposite directions. In these jets, electrons spiral through the magnetic field at close to the speed of light, generating X-rays in the same way that electrons moving back and forth in a radio transmitter generate radio waves.

Astronomers predict that the disk should produce lower energy X-rays than the jets. But no one had ever been able to show for sure which of the X-rays picked up by telescopes came from which source. "Nobody has been able to see them both working together until now," says Giorgio Palumbo, an astrophysicist from the University of Bologna, Italy.

Cosmic digestion

Palumbo and his colleague, Paola Grandi from the Italian National Research Council's Cosmic Physics and Space Astrophysics Institute in Bologna, studied data collected by the Italian-Dutch spacecraft BeppoSAX between 1996 and 2001. BeppoSAX was repeatedly pointed at a black hole, called 3C273, in a galaxy 3 billion light years from Earth. They report their findings in this week's edition of Science1.

They found that different parts of the X-ray signal varied in intensity over two separate timescales. By comparing data collected over several years, they were able to tease out which X-rays contributed to which component.

The researchers hope the result will help astronomers interpret the X-rays coming from other black holes too, revealing for example, how changes to a black hole's disk affect its jets. "It will give us clues about how exactly a black hole chews up matter and spits it out," says Palumbo.

Bron: http://www.nature.com/news/2004/0411...041101-12.html

[Miles]

Waarom worden er nooit samenvattingen van dergelijke stukjes gemaakt.

[GinnyPig]

Komt er op neer dat er twee verschillende processen rondom een zwart gat voor verschillende soorten rontgenstraling zorgen (met verschillende golflengtes dus). Namelijk door de wrijving van materie onderling in de accretieschijf, en door de versnelling van elektronen in de 'jets' van het zwarte gat.

N.B. wanneer een zwart gat met een andere ster een dubbelstersysteem vormt, kan het zwarte gat materie van de ster opzuigen. Deze materie valt echter niet direct in het zwarte gat, maar circuleert juist om het zwarte gat heen vanwege behoud van impulsmoment (net als het water dat niet direct een afvoerput in stroom). Het vormt op die manier een schijf: de accretieschijf. In die schijf kan de temperatuur flink oplopen wat dus de eerste oorzaak van rontgenstraling is. Verder kan invallende materie nog worden "weggeschoten" in de vorm van zogeheten jets. Dit komt door het magnetisch veld van het zwarte gat, alhoewel de precieze oorzaak nog niet helemaal bekend is. Geladen deeltjes die door een magnetisch veld bewegen zullen ook straling uitzenden. Dat is dus de andere oorzaak welke wordt genoemd.


De jets zijn de 2 bundels boven en onder het zwarte gat. Het blauwe geval is de accretieschijf.

ok en wat is nu precies de bedoeling van dit topic? Leuke ontdekking

[McCaine]

Lucky Luciano schreef op 05-11-2004 @ 18:21 :
ok en wat is nu precies de bedoeling van dit topic? Leuke ontdekking

Ja, precies dat, lijkt me.