Warps drive disruptions in planet formation in young planetary systems


Date:
February 3, 2022
Source:
University of Warwick
Summary:
A new study demonstrates the impact of passing stars, misaligned
binary stars and passing gas clouds on the formation of planets
in early star systems.



FULL STORY ==========================================================================
A new study from the University of Warwick demonstrates the impact of
passing stars, misaligned binary stars and passing gas clouds on the
formation of planets in early star systems.


========================================================================== Scientists have modelled how cosmic events like these can warp
protoplanetary discs, the birthplaces of planets, in the early evolution
of solar systems.

Their results are published today in the Astrophysical Journalin a study
funded by The Royal Society and the Engineering and Physical Sciences
Research Council, part of UK Research and Innovation.

Solar systems are formed from protoplanetary discs, massive spinning
clouds of gas and dust that will eventually coalesce into the array of
planets that we see in the Universe. When these discs are young they
form spiral structures, with all their dust and material dragged into
dense arms by the massive gravitational effect of the disc spinning.

But astronomers have found a surprising number of protoplanetary discs
that, despite being massive enough to have a spiral structure, show no
evidence of one. The University of Warwick team have been investigating
what might prevent a disc from forming a spiral structure.

PhD student Sahl Rowther from the University's Department of Physics
created a three-dimensional hydrodynamical simulation of a normal,
flat self-gravitating disc using a technique called smoothed-particle hydrodynamics. To this, he added different levels of curvature to the
disc to warp it, to study the impact on the disc's spiral structure. In
all but the smallest warps, the spiral structure disappeared.

The spiral structure in a protoplanetary disc is vital for the formation
of planets through Gravitational Instability and the results improve
our understanding of how solar systems evolve.



========================================================================== Co-author Dr Rebecca Nealon, Stephen Hawking Fellow in the Department of Physics, said: "Warps will inhibit planet formation through Gravitational Instability, in the sense that these spiral structures, which fragment
into clumps that eventually form planets, are where the disc structure
will be disrupted. Anything that disturbs that spiral structure makes
it harder for that clumping to occur and harder for the planets to form
via Gravitational Instability." The scientists explain that the warp
heats up the disc by inducing small perturbations to the velocity of the
gas as it orbits. The gas needs to be cool in order to clump together,
so in heating up the disc the spiral arm structure is wiped out.

There are a number of ways that a protoplanetary disc can be warped. A
few examples include; if a large object, such as a star, passes nearby
in a flyby encounter; if the disc surrounds a binary star system that
orbits out of alignment with the disc; or if a nearby source of gas
accretes onto the disc.

In recent years, evidence of warped protoplanetary disc has grown significantly, suggesting that they are more common in the Universe
than previously thought. It also provides a potential explanation for
the large number of massive protoplanetary discs that do not show a
spiral structure.

Dr Nealon adds: "Normally we think of these discs forming in isolation,
but that's not really the case. It's a chaotic neighbourhood, with lots
of stars nearby, and you might have a star that passes close by and that gravitational interaction is enough to cause this warp.

"Once we started getting observations of warped discs, we had to start considering warps in our modelling. We need a greater consideration of
warps in protoplanetary disc evolution and understanding that warps can
impact existing disc evolution mechanisms and physics. We need to consider
how warps affect all the factors in planetary formation." Sahl Rowther
said: "This study combines two physical effects that haven't been combined before, the physics of self-gravitating discs with the warp. This is
important because self-gravitating discs have been studied for a while
and it's a well-established field. Warps are a much more recent idea.

"We have modelled this in the most simple way possible to allow us
to be really sure about what we've done, and to easily demonstrate it." ========================================================================== Story Source: Materials provided by University_of_Warwick. Note: Content
may be edited for style and length.


========================================================================== Related Multimedia:
*
Impact_of_a_warp_as_it_wipes_out_the_spiral_structure_of_a_protoplanetary
disc ========================================================================== Journal Reference:
1. Sahl Rowther, Rebecca Nealon, Farzana Meru. Warping Away
Gravitational
Instabilities in Protoplanetary Discs. The Astrophysical Journal,
2022; 925 (2): 163 DOI: 10.3847/1538-4357/ac3975 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220203122938.htm

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