Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

XMM-Newton reveals X-rays from gas streams around young stars

01.06.2007
XMM-Newton has surveyed nearly two hundred stars under formation to reveal, contrary to expectations, how streams of matter fall onto the young stars’ magnetic atmospheres and radiate X-rays.
The results defy astronomers’ expectations, as the streams of falling matter interact with the hot corona, cooling it, while the ejected streams of gas heat up in shocks as they are ejected from the star.

The new XMM-Newton results paint a dramatic picture of the role magnetic fields play in star formation. “Star formation is a battle between gravity and everything else,” says Manuel Guedel, Paul Scherrer Institut, Villigen, Switzerland, who leads a large project addressing magnetic activity in young stars within the constellation of Taurus.

Star formation results in a complicated system in which the young star is surrounded by a disc of gas and dust. This matter then follows one of three different routes. It finds its way onto the star through magnetic funnels, or stays in the disc to form planets, or is thrown clear of the system in a wind or jet created by the overall magnetic field.

With the help of ESA’s X-ray observatory XMM-Newton, Guedel and his 25 international colleagues are now ready to report new details from the front line.

They used XMM-Newton to target stars in the nearby Taurus Molecular Cloud. This vast cloud in space is one of the star - forming regions nearest to Earth and contains over 400 young stars.

Most of these stars are still accumulating matter, a process known as accretion. As falling matter strikes the surface of the star, it typically doubles the temperature of the surface from 5000 Kelvin to 10 000 Kelvin. This produces an excessive amount of ultraviolet radiation emitted by the star and detected by XMM-Newton’s Optical Monitor. Astronomers had thought that the same shock waves that caused the emission of the ultraviolet excess should also produce an excess of X-rays.

Confusingly enough, previous observations seemed to show that young stars that still accrete matter give off less X-ray emission. To investigate this mystery, amongst several others, ESA approved a large programme of observations with XMM-Newton. The space-borne observatory investigated the densest regions of the Taurus Molecular Cloud for a total of more than 7 days.

The new results from XMM-Newton propose a solution to the mystery. In addition, they bring forward unanticipated discoveries. “We have not seen the expected X-rays that the shocks should produce on the surface of some stars,” says Guedel.

Instead, XMM-Newton’s spectrometers revealed a new and subtle feature suggesting that the falling material cooled the hot X-ray emitting atmosphere of the young stars, suppressing the emission of X-rays.

In certain cases, namely in the more heavily accreting stars, the suppression of the X-rays was such that the team realised that an additional process was at work in these objects. In addition to cooling the outer stellar atmosphere, the gas streams falling onto the star were so dense that they absorbed most of the X-rays that the star’s atmosphere had emitted.

Although such dense streams of gas should also contain dust that would obscure the star at visible wavelengths, the star is seen shining brightly. So what happens to this dust? The team can propose an answer to this as well. “The dust is heated so much by the radiation from the star, that it is vaporised before it can fall on the star,” says Guedel.

The strong X-ray suppression allowed the team to discover yet another X-ray source associated with the same stars coming from relatively cool gas that does not suffer from absorption. "This emission must come from outside the accretion streams," says Guedel. The team interprets the X-rays as evidence that some gas streams ejected by the star form shock waves that heat up very strongly.

The work gives astronomers powerful new insight into the tremendous forces at work in star formation.

Norbert Schartel | alfa
Further information:
http://www.esa.int/esaSC/SEMX379RR1F_index_0.html

More articles from Physics and Astronomy:

nachricht Studying fundamental particles in materials
17.01.2017 | Max-Planck-Institut für Struktur und Dynamik der Materie

nachricht Seeing the quantum future... literally
16.01.2017 | University of Sydney

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Water - as the underlying driver of the Earth’s carbon cycle

17.01.2017 | Earth Sciences

Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

17.01.2017 | Materials Sciences

Smart homes will “LISTEN” to your voice

17.01.2017 | Architecture and Construction

VideoLinks
B2B-VideoLinks
More VideoLinks >>>