If true, Oort Cloud comets are samples of the Sun's protoplanetary disk
that have been expelled to great distances and stored in deep freeze (10 Kelvins) for the age of the solar system.
Now, in a major discovery, scientists have detected the "water snow line" - the region where the temperature drops sufficiently low for snow to form - in a protoplanetary disk
around a young star.
The high contrast images made possible by observations with HiCIAO revealed the surprising details of PDS 70's protoplanetary disk
They theorized that depending on the size and structure of the constituent dust particles in the protoplanetary disk
, the radio waves emitted by the star should have "unique" polarization signatures.
Beichman cites three possible sources of this dust: asteroids smashing into each other, comets evaporating, and material drifting in from the outer edge of the original protoplanetary disk
The currently accepted theory on how giant planets in our solar system formed, known as core accretion, states a planet is formed around the young star in a protoplanetary disk
made primarily of hydrogen, helium, and particles of ices and dust composed of other chemical elements.
To explain the odd find, theorists proposed that the planet formed far from its star but then migrated closer, spiraling through the protoplanetary disk
of gas and dust that once swirled around its sun.
"Planet migration" is expected when the original protoplanetary disk
of gas and dust is still massive enough to exert a gravitational effect.
The extended arcs of dust or rock eclipsing KH 15D could be part of the star's protoplanetary disk
, a doughnut-shaped distribution of gas, dust, and ice that surrounds many young stars and contains the raw material to form planets, comets, and asteroids (SN: 5/4/02, p.
A research paper detailing the findings from the observations appeared Monday in the journal (http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.117.251101) Physical Review Letters under the title "Ringed Structures of the HD 163296 Protoplanetary Disk
Revealed by ALMA."
Scientists have known that planets form in a broad disk of dust and gas surrounding a star, a so-called "protoplanetary disk
." However, the composition of these special disks as well as the process by which they give rise to planets have remained a mystery.
Computer simulations of this random process done with different Jupiters, protoplanetary disk
masses, and stellar companions, show that some rocky planets acquire less than 10% of an Earth's worth of water while others are literally drowned with more than 10 to 100 oceans of water.