New position - jobs available

LMU logo I have started my new position at the Ludwig-Maximilians-University Munich (LMU) two weeks ago. My new group will be funded by the European Research Council and the LMU. Both postdoc and PhD positions will be available. For more go to the job advertisement page.
Comments

ERC Starting Grant

html5 logo I am thrilled to announce that I was awarded an ERC Starting Grant 2016. Stay tuned for upcoming advertisements for postdoc and PhD positions!
Comments

Press Releases on TW Hya and HL Tau

image credit: Carrasco-Gonzalez et al.; Bill Saxton, NRAO/AUI/NSF The last two weeks were busy - we released two press releases, both happened to be about observed substructure in disks.
The first one is on the iconic HL Tauri disk that we observed with the EVLA at optically thin wavelengths where we resolved a possible clump in the innermost ring.
For more information, you can read The second press release is about our ALMA observations of the TW Hya disk. These are pretty much the highest resolution observations ALMA can do aimed at the closest disk to us. Observations in the foreseeable future will not get much better than this. We found surprising ringed substructure, that is several ring/gap features, much narrower than seen in HL Tau. In addition to that, the inner gap that was predicted from analysis of the spectral intensity distribution before was finally imaged and found to be of 1 AU size. It is exciting to consider that these are likely the signposts of planets forming in the innermost regions of the system.

You can check out image credit: image credit: S. Andrews (Harvard-Smithsonian CfA), ALMA (ESO/NAOJ/NRAO)
Comments

Colder than expected

image credit: Digitized Sky Survey 2/NASA/ESA, inset: ESO/NASA/ESA The image to the left shows a circumstellar disk that is nick named "the flying saucer". The star in the center of the disk is not seen directly, because the thick dusty disk is exactly seen from the side (it is the dark line in the image) and it absorbs all the light that the star shines directly at us. The bright regions above and below that dark line is light that scatters off small dust grains above and below the disk. In addition to being so exactly edge-on, there is another peculiar arrangement: the disk is in front of a cloud of dust and gas. This special arrangement allowed us to directly measure the temperature of the dust using the ALMA telescope array.
It is commonly believed that dust in circumstellar disks, even far away from its central star, cannot be colder than about 15 degrees above absolute zero because there is always interstellar radiation that heats the dust particles to this minimum temperature. With this in mind, our measurements came as a surprise: we measured a dust temperature of only 7 degrees above absolute zero! There are some possible ways to explain this, but they all indicate that the dust grains have different shapes or different optical properties from what was commonly assumed.
Why does that matter? If we want to understand where planets can form and how large they can become, we need to know how much material is out there, in other words, we need to weight the disk. The methods to measure the masses of disks however rely on the knowledge of the dust temperature and other properties of the dust. Our measurements show that the dust seems to be quite different from what astronomers assumed it to be so far and they highlight why understanding the physics of those small dust particles is such an important part of understanding the origins of planets.

MPIA press release: English | German
ESO press release: English | German
Comments

Pre-transition Disks

image credit: P. Pinilla The origin of pre-transition disks, disks around young stars that consist of an outer and an inner dust ring, have puzzled researchers for decades. The inner rings seem to live very long, even though scientists did not think this could be possible. Our recent paper, published in Astronomy & Astrophysics, proposes a solution to this puzzle: the outer ring constantly supplies the inner ring, but it does so without being seen: the material is transported in only few large grains that are not easily detected. Therefore the regions between the rings do appear to be empty. Once the dust particles have reached the hot inner regions close to the star, they loose the water ice that binds them together and consequently, they break up into many small pieces. It is these small pieces we see close to the star as a second, inner hot ring of dust. Our paper was featured on Astronomie.nl (Dutch).
Comments

Press Release

image credit: NASA/JPL-CALTECH/T. PYLE (SSC) In our recent Astrophysical Journal Letter, we suggested that not all gaps that are seen in protoplanetary disks need too be caused by planets, but that some of them could be due to some sort of "cosmic illusion". A press release for our letter was issued by the Harvard-Smithsonian Center for Astrophysics. It was also picked up by Astronomy Magazine, Discovery.com, Astronews.com (German), AstroBiology Magazine, and many others.
Comments

New Website Design

html5 logo I updated my website design to modern, responsive HTML5. Amongst the changes are also blog comments which are now enabled. Feel free to use them to mention any issues you might have or to let me know what you think of the design.
Comments

Atlanta - IAUS315

Atlanta Last week I was at the IAU Symposium 315 "Young Stars and Planets Near the Sun" in Atlanta, GA where I presented an invited review on "Grain Growth and Evolution from Primordial to Debris Disks". Talk slides will be on the meeting website shortly.
Comments