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

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: LaserTAB: More efficient and precise contacts thanks to human-robot collaboration

At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.

Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...

Im Focus: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Fraunhofer ISE Pushes World Record for Multicrystalline Silicon Solar Cells to 22.3 Percent

25.09.2017 | Power and Electrical Engineering

Usher syndrome: Gene therapy restores hearing and balance

25.09.2017 | Health and Medicine

An international team of physicists a coherent amplification effect in laser excited dielectrics

25.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>