Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


In the planetary nursery

Astronomers determine the mass of the disk of gas and dust surrounding the star TW Hydrae

The disk surrounding the young star TW Hydrae is regarded as a prototypical example of planetary nurseries. Due to its comparatively close proximity of 176 light-years, the object plays a key role in cosmological birth models.

The birthplace of planets: New measurements that Thomas Henning from the Max Planck Institute for Astronomy in Heidelberg assisted in carrying out have resulted in a greater mass for the disk of gas and dust surrounding the young star TW Hydrae than previously assumed. The illustration depicts an artist’s conception of the disk. © Axel M. Quetz (MPIA)

Using the Herschel Space Telescope, researchers including Thomas Henning from the Max Planck Institute for Astronomy in Heidelberg have, for the first time, determined the mass of the disk very precisely. The new value is larger than previous estimates and proves that planets similar to those of our solar system can form in this system. In addition, the observations are an example of how, in the world of science, not everything can be planned for.

Where Egyptologists have their Rosetta Stone and geneticists their Drosophila fruit flies, astronomers studying planet formation have TW Hydrae: A readily accessible sample object with the potential to provide foundations for an entire area of study. TW Hydrae is a young star with about the same mass as the Sun. It is surrounded by a protoplanetary disk: a disk of dense gas and dust in which small grains of ice and dust clump to form larger objects and, eventually, into planets. This is how our Solar System came into being more than 4 billion years ago.

What is special about the TW Hydrae disk is its proximity to Earth: at a distance of 176 light-years from Earth, this disk is two-and-a-half times closer to us than the next nearest specimens, giving astronomers an unparalleled view of this highly interesting specimen – if only figuratively, because the disk is too small to show up on an image; its presence and properties can only be deduced by comparing light received from the system at different wavelengths (that is, the object's spectrum) with the prediction of models.

In consequence, TW Hydrae has one of the most frequently observed protoplanetary disks of all, and its observations are a key to testing current models of planet formation. That's why it was especially vexing that one of the fundamental parameters of the disk remained fairly uncertain: The total mass of the molecular hydrogen gas contained within the disk. This mass value is crucial in determining how many and what kinds of planets can be expected to form.

Previous mass determinations were heavily dependent on model assumptions; the results had significant error bars, spanning a mass range between 0.5 and 63 Jupiter masses. The new measurements exploit the fact that not all hydrogen molecules are created equal: Some very few of them contain a deuterium atom – where the atomic nucleus of hydrogen consists of a single proton, deuterium has an additional neutron. This slight change means that these "hydrogen deuteride" molecules consisting of one deuterium and one ordinary hydrogen atom emit significant infrared radiation related to the molecule's rotation.

The Herschel Space Telescope provides the unique combination of sensitivity at the required wavelengths and spectrum-taking ability ("spectral resolution") required for detecting the unusual molecules. The observation sets a lower limit for the disk mass at 52 Jupiter masses, with an uncertainty ten times smaller than the previous result. While TW Hydrae is estimated to be relatively old for a stellar system with disk (between 3 and 10 million years), this shows that there is still ample matter in the disk to form a planetary system larger than our own (which arose from a much lighter disk).

On this basis, additional observations, notably with the millimetre/submillimetre array ALMA in Chile, promise much more detailed future disk models for TW Hydrae – and, consequently, much more rigorous tests of theories of planet formation.

The observations also throw an interesting light on how science is done – and how it shouldn't be done. Thomas Henning explains: "This project started in casual conversation between Ted Bergin, Ewine van Dishoek and me. We realized that Herschel was our only chance to observe hydrogen deuteride in this disk – way too good an opportunity to pass up. But we also realized we would be taking a risk. At least one model predicted that we shouldn't have seen anything! Instead, the results were much better than we had dared to hope."

TW Hydrae holds a clear lesson for the committees that allocate funding for scientific projects or, in the case of astronomy, observing time on major telescopes – and which sometimes take a rather conservative stance, practically requiring the applicant to guarantee their project will work. In Henning's words: "If there's no chance your project can fail, you're probably not doing very interesting science. TW Hydrae is a good example of how a calculated scientific gamble can pay off."


Prof. Dr. Thomas Henning,
Max Planck Institute for Astronomy, Heidelberg
Phone: +49 6221 528-200
Fax: +49 6221 528-339
Email: henning@­
Dr. Markus Pössel,
Max Planck Institute for Astronomy, Heidelberg
Phone: +49 6221 528-261
Email: poessel@­
Background information
Whenever astronomers want to estimate the abundance of some compound, they search for characteristic light announcing the compound's presence. But this doesn't work for molecular hydrogen, as hydrogen molecules do not emit detectable radiation.
Original publication
E. A. Bergin, Th. Henning et al.
An Old Disk That Can Still Form a Planetary System
Nature, 31 January 2013

Prof. Dr. Thomas Henning | Max-Planck-Institute
Further information:

More articles from Physics and Astronomy:

nachricht Finding the lightest superdeformed triaxial atomic nucleus
20.10.2016 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

nachricht Innovative technique for shaping light could solve bandwidth crunch
20.10.2016 | The Optical Society

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: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Novel mechanisms of action discovered for the skin cancer medication Imiquimod

21.10.2016 | Life Sciences

Second research flight into zero gravity

21.10.2016 | Life Sciences

How Does Friendly Fire Happen in the Pancreas?

21.10.2016 | Life Sciences

More VideoLinks >>>