"Planet formation captured in photo"

[Spinnor]

From BBC news,

http://www.bbc.com/news/science-environment-29932609#

"The clearest ever image of planets forming around an infant star has been taken by the Alma radio telescope.

In a vast disc of dust and gas, dark rings are clearly visible: gaps in the cloud, swept clear by brand new planets in orbit.

The sun-like star at the centre, HL Tau, is less than a million years old and is 450 light years from Earth in the constellation Taurus.

The image was made possible by Alma's new high-resolution capabilities.

Because the process of planet formation takes place in the midst of such a huge dust cloud, it can't be observed using visible light."

Is science cool or what!

 

[Torbjorn_L]

Astounding observation! oo)

And also potentially illuminating on the system formation process.

- To make the planets that we see current models show that the formation process must be very quick, happening before the protoplanetary disk gas can disperse much.

"The authors do find a solution to the problem of insufficient mass by examining Class I protoplanetary disks. The solid mass distribution of these disks is shown in violet in Figure 2, and they clearly provide sufficient mass to build the planetary systems of all sizes. This means that the planet formation process must start very quickly, with dust already beginning to coalesce into planetesimals during the brief class I phase."

[ http://astrobites.org/2014/10/13/planet-formation-on-a-budget/ ]

"Class I protostars constitute roughly 10% of the complete Taurus-Auriga sample and have typical lifetimes of ~ 0.3 Myr (Offner & McKee 2011);".

"If accretion and mass loss remove a significant fraction of the solids from a class I disc, then the disc will not contain enough material to produce the known exoplanets. However, the time scales for agglomeration and radial transport of solids through the disc are much shorter than the time scales for accretion and mass loss. Thus, it seems plausible that known physical processes can concentrate the solids into large planetesimals while gas accretes onto the central star and is ejected in jets and winds."

[ http://arxiv.org/pdf/1409.7021v1.pdf ]

- The Kepler sample derives statistically from two different populations, a set with 6 +/-2 planets per star (which our own system belongs to), and an equally large set with 1 planet per star.

That could be explained by secular evolution, where in the majority of systems ejection of planets by other planets happens over time until there is a lone survivor. [ http://arxiv.org/pdf/1410.4192v1.pdf ] Which is bad news for astrobiology (my interest), but not too bad since some of the Kepler systems are reasonably old or of unknown age, and since nomad planets can support subsurface life for a very long time.

The young HL Tau system has ~ 7 planets (see the accompanying video on the web), which fits neatly into the Kepler statistics and into its possible explanation both.