ALMA captures stirred-up planet factory

Date:
August 3, 2020
Source:
National Radio Astronomy Observatory
Summary:
Planet-forming environments can be much more complex and chaotic
than previously expected. This is evidenced by a new image of the
star RU Lup, made with the Atacama Large Millimeter/submillimeter
Array (ALMA).



FULL STORY ========================================================================== [ALMA image of the | Credit: ALMA (ESO/NAOJ/NRAO), J. Huang and
S. Andrews; NRAO/AUI/NSF, S. Dagnello] ALMA image of the planet-forming
disk around the young star RU Lup. The inset image (lower left, red disk)
shows a previous (DSHARP) observation of the dust disk with rings and
gaps that hint at the presence of forming planets. The new observation
shows a large spiral structure (in blue), made out of gas, that spans
far beyond the compact dust disk.

Credit: ALMA (ESO/NAOJ/NRAO), J. Huang and S. Andrews; NRAO/AUI/NSF, S.

Dagnello [ALMA image of the | Credit: ALMA (ESO/NAOJ/NRAO), J. Huang and
S. Andrews; NRAO/AUI/NSF, S. Dagnello] ALMA image of the planet-forming
disk around the young star RU Lup. The inset image (lower left, red disk)
shows a previous (DSHARP) observation of the dust disk with rings and
gaps that hint at the presence of forming planets. The new observation
shows a large spiral structure (in blue), made out of gas, that spans
far beyond the compact dust disk.

Credit: ALMA (ESO/NAOJ/NRAO), J. Huang and S. Andrews; NRAO/AUI/NSF, S.

Dagnello Close Planet-forming environments can be much more complex and
chaotic than previously expected. This is evidenced by a new image of the
star RU Lup, made with the Atacama Large Millimeter/submillimeter Array
(ALMA).


==========================================================================
All planets, including the ones in our Solar System, are born in disks
of gas and dust around stars, so-called protoplanetary disks. Thanks to
ALMA we have stunning high-resolution images of many of these planet
factories, showing dusty disks with multiple rings and gaps that hint
at the presence of emerging planets. The most famous examples of these
are HL Tau and TW Hydrae.

But disks are not necessarily as neatly arranged as these initial dust observations suggest. A new ALMA image of RU Lup, a young variable star in
the Lupus constellation, revealed a giant set of spiral arms made of gas, extending far beyond its more well-known dust disk. This spiral structure
-- resembling a 'mini-galaxy' -- extends to nearly 1000 astronomical
units (au) from the star, much farther away than the compact dust disk
that extends to about 60 au.

Previous observations of RU Lup with ALMA, which were part of the Disk Substructures at High Angular Resolution Project, already revealed
signs of ongoing planet formation, hinted by the dust gaps in its protoplanetary disk.

"But we also noticed some faint carbon monoxide (CO) gas structures that extended beyond the disk. That's why we decided to observe the disk around
the star again, this time focusing on the gas instead of the dust," said
Jane Huang of the Center for Astrophysics, Harvard & Smithsonian (CfA)
and lead author on a paper published today in the Astrophysical Journal.

Protoplanetary disks contain much more gas than dust. While dust is
needed to accumulate the cores of planets, gas creates their atmospheres.

In recent years, high resolution observations of dust structures have revolutionized our understanding of planet formation. However, this new
image of the gas indicates that the current view of planet formation
is still too simplistic and that it might be much more chaotic than
previously inferred from the well-known images of neatly concentric
ringed disks "The fact that we observed this spiral structure in the
gas after a longer observation suggests that we have likely not seen
the full diversity and complexity of planet-forming environments. We
may have missed much of the gas structures in other disks," added Huang.

Huang and her team suggest several scenarios that could possibly explain
why the spiral arms appeared around RU Lup. Maybe the disk is collapsing
under its own gravity, because it is so massive. Or maybe RU Lup is
interacting with another star. Another possibility is that the disk is interacting with its environment, accreting interstellar material along
the spiral arms.

"None of these scenarios completely explain what we have observed,"
said team- member Sean Andrews of CfA. "There might be unknown processes happening during planet formation that we have not yet accounted for in
our models. We will only learn what they are if we find other disks out
there that look like RU Lup." This research is presented in a paper
titled "Large-scale CO spiral arms and complex kinematics associated
with the T Tauri star RU Lup," by J. Huang et al., in the Astrophysical Journal.

The team is composed of Jane Huang, Sean M. Andrews, Karin I. O"berg and
David J. Wilner (Center for Astrophysics | Harvard & Smithsonian), Megan Ansdell (NASA HQ), Myriam Benisty (Universidad de Chile/IPAG France),
John M. Carpenter (Joint ALMA Observatory Chile), Andrea Isella (Rice University), Laura M.

Pe'rez (Universidad de Chile), Luca Ricci (California State University Northridge), Jonathan P. Williams (University of Hawaii), and Zhaohuan
Zhu (University of Nevada).


========================================================================== Story Source: Materials provided by
National_Radio_Astronomy_Observatory. Note: Content may be edited for
style and length.


========================================================================== Related Multimedia:
* Images_of_the_planet-forming_disk_around_the_young_star_RU_Lup ========================================================================== Journal Reference:
1. Jane Huang, Sean M. Andrews, Karin I. O"berg, Megan Ansdell, Myriam
Benisty, John M. Carpenter, Andrea Isella, Laura M. Pe'rez,
Luca Ricci, Jonathan P. Williams, David J. Wilner, Zhaohuan
Zhu. Large-scale CO Spiral Arms and Complex Kinematics Associated
with the T Tauri Star RU Lup. The Astrophysical Journal, 2020;
898 (2): 140 DOI: 10.3847/1538- 4357/aba1e1 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200803140010.htm

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