Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Infrared Halo Frames a Newborn Star

28.08.2003


The DC303.8-14.2 globule

A small and dark interstellar cloud with the rather cryptic name of DC303.8-14.2 is located in the inner part of the Milky Way galaxy. It is seen in the southern constellation Chamaeleon and consists of dust and gas. Astronomers classify it as a typical example of a "globule".

As many other globules, this cloud is also giving birth to a star. Some years ago, observations in the infrared spectral region with the ESA IRAS satellite observatory detected the signature of a nascent star at its centre. Subsequent observations with the Swedish ESO Submillimetre Telescope (SEST) at La Silla (Chile) were carried out by Finnish astronomer Kimmo Lehtinen. He revealed that DC303.8-14.2 is collapsing under its own gravity, a process which will ultimately result in the birth of a new star from the gas and dust in this cloud.



Additional SEST observations of the millimetre emission of carbon monoxide (CO) molecules demonstrated a strong outflow from the nascent star. A small part of the gas that falls inward onto the central object is re-injected into the surrounding via this outward-bound "bipolar stream".

The structure of DC303.8-14.2

The left panel in PR Photo 26a/03 shows the DC303.8-14.2 globule as it looks in red light. This image was obtained at wavelength 700 nm and has been reproduced from the Digitized Sky Survey (DSS) [1]. It covers a sky region of 20 x 20 arcmin2, or about 50% of the area of the full moon. The dust particles in the cloud reflect the light from stars, causing the cloud to appear brighter than the adjacent sky.

The brightness distribution over the cloud depends mostly on three factors connected to the dust. The first is the distribution of dust grains in the cloud, the way the dust density changes with the distance from the centre of the cloud. The second is the relative amount of light that is reflected by the dust particles. The third indicates the dominant direction in which the dust particles scatter light; this is dependent on the geometry of the grains and their preferred spatial alignment. Accurate observations of the brightness distribution over the surface of a globule allow an investigation of these properties and thus to learn more about the structure and composition of the cloud.

From the image obtained in red light (left panel in PR Photo 26a/03) it appears, somewhat surprisingly, that the brightest area of DC303.8-14.2 is not where there is most dust. Instead, it takes the form of a bright ring around the centre. This rim corresponds to a region where the intensity of the light from stars behind the cloud is reduced by a moderate factor of 3 to 5 when passing through the cloud and where the light-scattering efficiency of the dust grains in the cloud is the highest.

Observing with ISAAC on the VLT

In order to study the structure of DC303.8-14.2 in more detail, Kimmo Lehtinen and his team of Finnish and Danish astronomers [2] used the near-infrared imaging capabilities of the ISAAC multi-mode instrument on the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory (Chile). Under good observing conditions, they obtained a mosaic image of this cloud in several near-IR wavelength bands, including the J- (centered at wavelength 1.25 µm), H- (1.65) and Ks-bands (2.17). These exposures were combined to produce images of DC303.8-14.2, two of which are shown in PR Photo 26a/03 (middle and right panels).

The middle image shows the central part of the globule in the H-band. A bright rim is clearly detected - this is the first time such a ring is seen in infrared light around a globule.

This rim has a smaller size in infrared than in visible light. This is because the absorption of infrared light by dust particles is smaller than the absorption of visible light. More dust is then needed to produce the same amount of scattering and to show a rim in infrared light. The infrared rim will therefore show up in an area where the dust density is higher, i.e. closer to the centre of the cloud, than the visible-light rim.

Similar rings were also detected in the J- and Ks-band images and, as expected, of different sizes. Thus the mere observation of the size (and shape) of a bright rim already provides information about the internal structure of the cloud. In the case of DC303.8-14.2, a detailed evaluation shows that the dust density of the centre is so high that any visible light from the nascent star in there would be dimmed at least 1000 times before it emerges from the cloud.

Getting a bonus: Jets from a young star

As an unexpected and welcome bonus, the astronomers also detected several jet- and knot-like structures in the Ks-band image (right panel in PR Photo 26a/03), near the IRAS source. The area shown represents the innermost region of the cloud (65 x 50 arcsec2, or just 1/500 of the area of the DSS image to the left).

Several knot-like structures on a line like a string of beads are clearly seen. They are most probably regions where the gas ejected by the young stellar object rams into the surrounding medium, creating zones of compressed and hot molecular hydrogen. Such structures are known by astronomers as "Herbig-Haro objects", cf. ESO PR 17/99.

More information

A general description of the methods used to study and model surface brightness observations of small dark clouds in given in a basic paper by Kimmo Lehtinen and Kalevi Mattila in the research journal Astronomy & Astrophysics (Vol. 309, p. 570 1996). The results presented here will be published in a forthcoming paper in Astronomy & Astrophysics.

Notes

[1]: The Digitized Sky Survey was produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions.

[2]: The team is composed of Kimmo Lehtinen, Kimmo Mattila from the Observatory of the University of Helsinki (Finland), Petri Väisänen from ESO/Chile and Jens Knude from the Observatory of the University of Copenhagen (Denmark). P. Väisänen is also affiliated with the University of Helsinki.

Contact
Kimmo Lehtinen
Observatory, University of Helsinki
Finland
Phone: +358-0-19122909
email: kimmo.lehtinen@helsinki.fi

Dr. Kimmo Lehtinen | ESO
Further information:
http://www.eso.org/outreach/press-rel/pr-2003/phot-26-03.html
http://www.eso.org/outreach/press-rel/pr-2003/phot-26a-03-preview.jpg

More articles from Physics and Astronomy:

nachricht First Juno science results supported by University of Leicester's Jupiter 'forecast'
26.05.2017 | University of Leicester

nachricht Measured for the first time: Direction of light waves changed by quantum effect
24.05.2017 | Vienna University of Technology

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: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

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....

Im Focus: A quantum walk of photons

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....

Im Focus: Turmoil in sluggish electrons’ existence

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...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

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...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>