NOVA: Moving Shadows around Planet-Forming Star

[bystander]

Astronomers See Moving Shadows Around Planet-Forming Star
Netherlands Research School for Astronomy (NOVA) | 2017 Nov 09

[img3=" Astronomers took a 'photo' of the star HD 135344B and the disk for several days. They used the SPHERE instrument at the Very Large Telescope in Chile. The star itself is removed from the picture. (c) Tomas Stolker (University of Amsterdam)"]http://www.astronomie.nl/media/medialib ... adows.jpeg[/img3][hr][/hr]

A team of mainly Dutch astronomers has observed moving shadows on a dust disk around a star. On multiple days they took a 'photo' of the star and its disk. They used the SPHERE instrument, partially built in the Netherlands, on the Very Large Telescope in Chile. Probably, processes in the inner disk cast their shadows at the outer disk. ...

The discovery builds on an earlier publication in which the researchers made one image of the disk. By making multiple images, the astronomers clearly saw variations in the shadows. As a result, they could study the shadows in more detail.

The astronomers observed the shadows near the star HD135344B. That's a young star at a distance of about 450 light years of the earth. The dust disk around the star shows striking spiral arms. The researchers suspect that they are caused by one or more heavy protoplanets that will evolve into Jupiter-like worlds. ...

Variable Dynamics in the Inner Disk of HD 135344B Revealed
with Multi-Epoch Scattered Light Imaging - Tomas Stolker et al

• arXiv.org > astro-ph > arXiv:1710.02532 > 06 Oct 2017

[sallyseaver]

Researchers made a case that planets (which are on the order of 10^4 km - 10^5 km wide) can affect large-scale modifications in a circumstellar disk which has a size on the order of 10^13 km to 10^14 km (80 au to 150 au).
https://www.nasa.gov/feature/goddard/sp ... ve-planets

I haven't read the research paper, but I don't buy it. With gravity dropping off as the inverse square of distance, and given the angular momentum that all particles in the circumstellar disk have, I don't see a protoplanet being able to affect gaseous matter, dust and rocks beyond about 10^4 km distant, maybe 10^5 km at the most.

Here are 2 other young star objects along with the same one above imaged by SPHERE
https://storage.googleapis.com/mass-vor ... o1640a.jpg

It seems to me that the more we learn about young star objects, the more we see that does not match up with the current theory.

[sallyseaver]

I thought about this more. I think that the scale between a planet and the protostellar disk beyond 1 au from the center, is like the relationship between a pea and the clouds in the sky. [How different is the atmosphere from the outer region of a protostellar disk?] We can see clouds, just like we can see the gases of a protostellar disk. A pea is about .5 cm. Clouds are present between 6 and 25 km above the surface of the earth. If you were able to connect a pea to a long length of string and spun it around and around in an open space under cloud cover, would you expect to affect clouds in the sky? The scale of difference between the pea (5 x 10^-3 m) and a cloud covering of 100s of kilometers wide at a distance of 6-25 km (6-25 x 10^3 m) above the pea is 10^6. I don't think an even more dense atmosphere would matter. The pea would swing through the air and its surrounding disturbance could be measured at what distance do you think? Maybe a meter above and below the orbiting pea? This is a scale difference of about 10^3. And such a disturbance would not be able to be seen at large distances comparable to the light years that we are away from the young star object in the image.

A whole bunch of smaller rocks that are in the process of aggregating into a planet would have even less power to affect the gases of the protostellar disk, since they are smaller masses with similar angular velocity.

The scale difference between a protoplanet and the gases at a distance that make up the spiral arms in the image are even greater than 10^6. So I take it back, I don't think that protoplanets can gravitationally affect gases at a distance of 10^4 to 10^5 greater than its diameter. I know that fluid dynamics can get pretty complex, but a computer simulation that has a pea-like protoplanet-sized bunch of mass affecting a huge protostellar disk of gas goes beyond credibility.

Please provide the reasoning for why planets can affect the ripples in a protoplanetary disk, when a pea spinning in an open space would not affect ripples in the clouds at 6-25 km above. What am I missing and why do you accept this research?

[neufer]

Please provide the reasoning for why planets can affect the ripples in a protoplanetary disk, when a pea spinning in an open space would not affect ripples in the clouds at 6-25 km above. What am I missing and why do you accept this research?

Planets can't affect the ripples in this protoplanetary disk.

However, "heavy protoplanets" can project shadows onto this protoplanetary disk.

[sallyseaver]

However, "heavy protoplanets" can project shadows onto this protoplanetary disk.

According to the research paper that you reference in your first post says that the research is based on a spatial resolution of 6.4 au, that is 6.4 x 1.5 x 10^11 m = 9.6 x 10^11 m or about 1 x 10^12 m... per pixel. The abstract says that the shadows are cast by localized density enhancements.

What assumptions are you making about a "heavy protoplanet" with respect to Jupiter? I think we are talking about a planetesimal with nearby asteroids that are gravitationally moving towards the planetesimal. Is this correct? The whole diameter of Jupiter is about 1.4 x 10^8.* What size are you projecting for the planetesimal at the point of growth that it is in with surrounding asteroids? Do you really think that it could cast a shadow that is about 10^6 (10 x 10 pixels) times larger than it is?

The abstract says "Possible mechanisms that may cause asymmetric variations in the optical depth through the atmosphere of the inner disk include turbulent fluctuations, planetesimal collisions, or a dusty disk wind, possibly enhanced by a minor disk warp." So I don't think that there is really a conclusion here that protoplanets are responsible for the shadows. Looking more closely at this, do you agree?

Planets loom large in our minds as objects of interest, but in actuality the mass of all planets in our solar system fit in the rounding error of the Sun's mass relative to the total system's mass; the Sun has 99.86% of the mass of the total system. At the optical resolution (such as 6.4 au) that we see remote protostars, the dark or transparent "lanes" cannot possibly be due to the relatively minuscule protoplanets.

Where are the honest space scientists that are going to recognize that the new, better observations of young star objects are actually showing up anomalies which call for a new paradigm?

____________________________________________
*Jupiter is an oblate spheroid with an equatorial radius of 71,492 km. If it the same mass was in a sphere, the mean equatorial radius would be 69,911 km. So an astronomical body of Jupiter's size has a diameter of about 1.4 x 10^8 m (even if it is a lot more dense).

[sallyseaver]

Following are some more young star objects in progression of star system development.



1) Spiral AFGL 3068 in our galaxy [The line is a photographic artifact of a near-field star.] This image was taken in near infra-red wave lengths, so the blueish color of the spirals indicates cold temperatures and the brown in the center indicates warm temperature. | Image Credit: ESA, Hubble, R. Sahai (JPL), NASA http://apod.nasa.gov/apod/ap161211.html and “A Binary-Induced Pinwheel Outflow from the Extreme Carbon Star AFGL 3068” by Mark Morris, R. Sahai, K. Matthews, J. Cheng, et. al., Intl. Astronomical Union, 2006

Click to view full size image

2) This image, captured with the Atacama Large Millimeter/submillimeter Array (ALMA) features a protoplanetary disc surrounding the young stellar object Elias 2-27, some 450 light years away. "ALMA, for the first time, was able to peer deep into the mid-plane of a disk and discovered the clear signature of spiral density waves." Paper detailing Elias 2-27: http://science.sciencemag.org/content/3 ... /1519.full

[sallyseaver]

3) Young Star Object: V883 Orionis
Credit: ALMA (ESO/NAOJ/NRAO)/L. Cieza

The dark band in the middle of the disk is in the neighborhood of 35-70 au, based on visual inspection given the parameters of the image.

Click to view full size image

4) Observations from the ALMA telescope in Chile revealed spinning jets of material (green) ejecting from inside the accretion disk around a young star, which ALMA could picture at a resolution of 8 astronomical units. A model of the solar system is included in the lower left for scale.
Credit: ALMA (ESO/NAOJ/NRAO)/Lee et al.
https://www.space.com/37294-protostar-g ... urger.html

At a later stage, we can see a dark space in a different dimension, vertically, as the protostellar disk separates along the spin axis.

[sallyseaver]

5) Infrared image from Subaru Telescope shows a gap between the center area (that has a black cover over the bright central light) and the protostellar disk, with an arm of gas extending from the outer disk to the inner region. And there is an asymmetric dip on the left.
An arcsecond is 1/3600 of a degree (˚).
Credit: The Graduate University for Advanced Studies and the National Astronomical Observatory of Japan
https://phys.org/news/2013-02-infrared- ... ition.html

A gap of 72.5 au that is completely clear of debris except for one flow-path (called an "arm" here) is not due to minuscule protoplanets. The "dip" is an indication of ongoing vortex motion.

[MargaritaMc]

I haven't read the research paper,

Why?

VARIABLE DYNAMICS IN THE INNER DISK OF HD 135344B REVEALED WITH MULTI-EPOCH SCATTERED LIGHT IMAGING
Tomas Stolker, Mike Sitko,et al
ABSTRACT
We present multi-epoch Very Large Telescope/Spectro-Polarimetric High-contrast Exoplanet REsearch observations of the protoplanetary disk around HD 135344B (SAO 206462). The J -band scattered light imagery reveal, with high spatial resolution (41mas, 6.4au), the disk surface beyond 20au. Temporal variations are identied in the azimuthal brightness distributions of all epochs, presumably related to the asymmetrically shading dust distribution in the inner disk. These shadows manifest themselves as narrow lanes, cast by localized density enhancements, and broader features which possibly trace the larger scale dynamics of the inner disk. We acquired visible and near-infrared photometry which shows variations up to 10% in the JHK bands, possibly correlated with the presence of the shadows. Analysis of archival Very Large Telescope Interferometer/PIONIER H -band visibilities constrain the orientation of the inner disk to i =18°.2(+3.4, -4.1) and PA = 57°.3 ±5°.7, consistent with an alignment with the outer disk or a minor disk warp of several degrees. The latter scenario could explain the broad, quasi-stationary shadowing in N-NW direction in case the inclination of the outer disk is slightly larger. The correlation between the shadowing and the near-infrared excess is quantified with a grid of radiative transfer models. The variability of the scattered light contrast requires extended variations in the inner disk atmosphere (H/r ≥ 0:2). Possible mechanisms that may cause asymmetric variations in the optical depth ( Δτ ≤ 0.1) through the atmosphere of the inner disk include turbulent fluctuations, planetesimal collisions, or a dusty disk wind, possibly enhanced by a minor disk warp. A fine temporal sampling is required to follow day-to-day changes of the shadow patterns which may be a face-on variant of the UX Orionis phenomenon.

Free download of whole paper available here:
https://arxiv.org/abs/1710.02532

NB. The ≥ and ≤ in the above quotation should be a composite of < or > and ~ but my keyboard doesn't have these symbols

[sallyseaver]

I haven't read the research paper,

Why?

VARIABLE DYNAMICS IN THE INNER DISK OF HD 135344B REVEALED WITH MULTI-EPOCH SCATTERED LIGHT IMAGING
Tomas Stolker, Mike Sitko,et al
ABSTRACT
We present multi-epoch Very Large Telescope/Spectro-Polarimetric High-contrast Exoplanet REsearch observations of the protoplanetary disk around HD 135344B (SAO 206462). The J -band scattered light imagery reveal, with high spatial resolution (41mas, 6.4au), the disk surface beyond 20au. Temporal variations are identied in the azimuthal brightness distributions of all epochs, presumably related to the asymmetrically shading dust distribution in the inner disk. These shadows manifest themselves as narrow lanes, cast by localized density enhancements, and broader features which possibly trace the larger scale dynamics of the inner disk. We acquired visible and near-infrared photometry which shows variations up to 10% in the JHK bands, possibly correlated with the presence of the shadows. Analysis of archival Very Large Telescope Interferometer/PIONIER H -band visibilities constrain the orientation of the inner disk to i =18°.2(+3.4, -4.1) and PA = 57°.3 ±5°.7, consistent with an alignment with the outer disk or a minor disk warp of several degrees. The latter scenario could explain the broad, quasi-stationary shadowing in N-NW direction in case the inclination of the outer disk is slightly larger. The correlation between the shadowing and the near-infrared excess is quantified with a grid of radiative transfer models. The variability of the scattered light contrast requires extended variations in the inner disk atmosphere (H/r ≥ 0:2). Possible mechanisms that may cause asymmetric variations in the optical depth ( Δτ ≤ 0.1) through the atmosphere of the inner disk include turbulent fluctuations, planetesimal collisions, or a dusty disk wind, possibly enhanced by a minor disk warp. A fine temporal sampling is required to follow day-to-day changes of the shadow patterns which may be a face-on variant of the UX Orionis phenomenon.

Free download of whole paper available here:
https://arxiv.org/abs/1710.02532

NB. The ≥ and ≤ in the above quotation should be a composite of < or > and ~ but my keyboard doesn't have these symbols

Thank you MargaritaMc. Yes, I did read the abstract and download the paper later, after my first post. You will see that I responded to neufer with more details from the abstract. The reason why I had not read it in my first post was: a) availability of time... and b) it seemed to be one more article that overlooks the scale difference between protoplanets and their protostellar disk. (it's sort of a hot button issue with me these days.)