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Simin Tong @simintong.bsky.social · 07/09/2026

Finally, Serpens still has a few surprises 👀 We identify two protoplanetary disks with very large inner cavities (~90 au), including one with a strong asymmetry. What created these structures? We still don’t know. 🧵(n/n)

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Simin Tong @simintong.bsky.social · 07/09/2026

Their lack of Gaia detections, strong 2D clustering, and low masses may indicate young, embedded systems whose disks experienced strong tidal truncation earlier in their evolution. (9/n)

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Simin Tong @simintong.bsky.social · 07/09/2026

In Ophiuchus, the low dust masses are mainly driven by sources without Gaia memberships, and this cannot be simply explained by the stellar mass dependence. (8/n)

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Simin Tong @simintong.bsky.social · 07/09/2026

Disks in Ophiuchus and Corona Australis appear unexpectedly low in dust masses for their young ages (Cazzoletti+2019; Williams+2019). However, when we only consider high-confidence members in a given region identified by Gaia, their dust masses are broadly consistent with their ages. (7/n)

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Simin Tong @simintong.bsky.social · 07/09/2026

Beyond Serpens, we find that Ophiuchus is genuinely very dense, while the major region of Corona Australis is also relatively dense given its relatively old age (>5 Myr; Esplin & Luhman 2022). (6/n)

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Simin Tong @simintong.bsky.social · 07/09/2026

Serpens is extended along the line of sight, so converting from 2D to 3D substantially lowers its inferred density. Even accounting for missing members is unlikely to make Serpens dense enough for stellar encounters to strongly affect its disks. (5/n)

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Simin Tong @simintong.bsky.social · 07/09/2026

We revisited the stellar densities of nearby star-forming regions using Gaia distances for individual stars. This allows us to measure their 3D stellar densities, rather than the projected 2D surface densities. We find that Serpens is much less dense in 3D. (4/n)

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Simin Tong @simintong.bsky.social · 07/09/2026

But our survey, along with the earlier study led by Alexa Anderson, finds that the dust disk masses in Serpens are similar to those in Lupus and Taurus, two young regions with much lower stellar densities (Fig 6 in Anderson+2022). So, is Serpens really that dense? (3/n)

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Simin Tong @simintong.bsky.social · 07/09/2026

Serpens has long been considered denser than many nearby young star-forming regions (e.g. Megeath+2016, their Fig. 15). Such high stellar densities could lead to more frequent encounters between star–disk systems, potentially truncating disks and reducing their dust masses. (2/n)

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Reposted by Simin Tong

Exoplanet Courier @exocourier.bsky.social · 04/09/2026

[2609.03759] Simin Tong et al.: Disk survey in the Serpens star-forming region: Environmental effects in nearby star-forming regions. link

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University of Leicester, Physics & Astronomy @physicsuol.bsky.social · 19/05/2026

Huge congratulations to the SMILE team, including the team in Leicester who built its ultra-lightweight X-ray optics! SMILE measures how Earth’s magnetic field responds to the solar wind, helping to reduce the worst effects of solar storms before they strike 🔭🎢 le.ac.uk/news/2026/ma...

le.ac.uk

UK plays leading role as landmark mission launches to unlock secrets of Earth’s magnetic shield | News | University of Leicester

SMILE launches to provide first complete picture of how Earth’s magnetic field responds to the solar wind, improving predictions of solar storms that disrupt GPS, communications and power grids.

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Reposted by Simin Tong

RAS Journals @rasjournals.bsky.social · 12/01/2026

Published in #MNRAS: "Turbulence and dust fragility in protoplanetary discs", Tong et al. This is Fig. 3: for the caption & to read the paper please visit academic.oup.com/mnras/articl... @royalastrosoc.bsky.social @academic.oup.com

Continuum images of GM Aur in ALMA Bands 6 (⁠lambda = 1.3 mm, upper panels) and 4 (⁠lambda = 2.1 mm, lower panels). The left columns are for sky-plane images adopted from J. Huang et al. (2020), and the right columns are for corresponding deprojected images. Beam sizes are denoted as ellipses at the left corners in panels of the sky plane images. Resolution and sensitivity of these data are reported in the caption of Fig. 2. We remind the readers that GM Aur is shown as a representative example of multiple-ringed discs seen in multiwavelength observations, and reproducing the GM Aur disc is not the aim of this study.

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Elisabeth Matthews @elisabethastro.bsky.social · 11/12/2025

The MPIA call for summer interns is now live! This is a great opportunity for bachelors & masters students from anywhere in the world to come an complete a three month, fully funded research project in beautiful Heidelberg. Check it out here: www.mpia.de/en/careers/i...

mpia.de

Summer internships

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Reposted by Simin Tong

Sera Markoff @profsera.bsky.social · 11/12/2025

⭐️✨🔭Please help us get the message out about the 7th annual international ASPIRE program at @api.uva.nl. This summer 2026 school provides astronomy research experience for talented MSc students from countries where opportunities to move into a PhD program are limited. Applications are due 17 Dec! ⭐️✨🔭

aspire.science.uva.nl

ASPIRE

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Reposted by Simin Tong

University of Leicester, Physics & Astronomy @physicsuol.bsky.social · 11/11/2025

🔭🧪🎢 PhD Project focus: Understanding protoplanetary disc evolution We're advertising this project with Prof Richard Alexander, making simulations of accretion of planet-forming discs onto their star. For details of all our PhD projects look here: le.ac.uk/study/resear... 🔭🧪🎢

Artist’s impression of a disc wind dispersing a planet-forming disc around a young star. Credit ESO / M. Kornmesser.

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Simin Tong @simintong.bsky.social · 23/10/2025

Just saw it🙈 I was away from social media for a while. But thanks for advertising our work!

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Reposted by Simin Tong

Richard Alexander @richardalexander.bsky.social · 30/09/2025

New paper, led by @physicsuol.bsky.social PhD student @simintong.bsky.social. Simin looked at the rings we see in planet-forming discs, and combined new models with multi-wavelength ALMA observations to understand the underlying physical properties of the dust and gas. 🔭 arxiv.org/abs/2509.24818

Fig.3 from Tong et al. (2025), showing ALMA observations of the GM Aur protoplanetary disc at 1.3mm (Band 6) and 2.1mm (Band 4). Left panels are the sky-plane images from Huang et al. (2020); right panels show the same observations de-projected.

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Simin Tong @simintong.bsky.social · 19/06/2025

Or just more available time after getting rid of your PhD student 🤣

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Simin Tong @simintong.bsky.social · 19/06/2025

Curious what science project motivates you to learn Python 😂

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Simin Tong @simintong.bsky.social · 28/03/2025

I guess it is pizza with nothing 😂 all other pizza has ingredients showing below.

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Reposted by Simin Tong

Richard Alexander @richardalexander.bsky.social · 12/02/2025

@simintong.bsky.social is giving a talk (remotely) on our new paper (👇🏻) at the "Pebbles in Planet Formation" conference in Tokyo this week. [Simin's talk is on Thursday morning; for those attending online, it's overnight Wed/Thu in Europe, or Wed evening in the US.] 🔭 indico2.riken.jp/event/5012/

Conference poster for "Pebbles in Planet Formation", Toyko, 10-13 Feb 2025.

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Simin Tong @simintong.bsky.social · 11/02/2025

Recovered now. It was down a few weeks ago also, but was not during the working hours in our time zone.

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Reposted by Simin Tong

Richard Alexander @richardalexander.bsky.social · 10/02/2025

New paper, by Leicester PhD student @simintong.bsky.social. Simin presents a new set of models which show that compact protoplanetary discs are a natural consequence of so-called ``dead zones'': regions where disc turbulence is low. 🔭 arxiv.org/abs/2502.04452

arxiv.org

Compact protoplanetary discs can be produced by dead zones

Radially compact protoplanetary discs (<=50 au) are ubiquitous in nearby star-forming regions. Multiple mechanisms have been invoked to interpret various compact discs. In this paper, we propose that ...

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Exoplanet Courier @exocourier.bsky.social · 10/02/2025

[2502.04452] Simin Tong & Richard Alexander: Compact protoplanetary discs can be produced by dead zones. link

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