Weekly Update from the Open Journal of Astrophysics 13/06/2026

It’s Saturday again so it’s time for another update of activity at the Open Journal of Astrophysics. Since the last update we have published a further three papers, bringing the number in Volume 9 (2026) to 122 and the total so far published by OJAp up to 570.

I will continue to include the posts made on our Mastodon account (on Fediscience); these announcements also show the DOI for each paper.

The first paper to report this week, published on Thursday 11th June, is “Dancing Streams In Merging Halos: Stellar Streams in a MW–LMC-like merger” by (all based in the USA): Sachi Weerasooriya (Carnegie Observatories), Tjitske Starkenburg (Northwestern U.), Emily C. Cunningham (Columbia U.) & Kathryn V. Johnston (Flatiron Institute). This article explores how galaxy mergers, like the Milky Way-Large Magellanic Cloud merger, significantly alter the properties and structures of stellar streams, challenging the recovery of their initial orbits. It is in the folder marked Astrophysics of Galaxies.

The overlay for this paper is here

You can find the officially accepted version on arXiv here and the announcement on Fediverse here:

https://fediscience.org/@OJ_Astro/116730200889106529

The second paper for this week, also published on Thursday 11th June but in the folder Cosmology and Nongalactic Astrophysics is “X-SORTER (X-ray Survey Of meRging clusTErs in Redmapper): X-ray and Spectroscopic Characterization of 12 Optically Selected Galaxy Cluster Merger Candidates” by Christopher Hopp, David Wittman, Rodrigo Stancioli, Zhuoran Gao & Faik Bouhrik (UC Davis) and Scott Adler (Rochester), all based in the USA. The X-SORTER program identifies merging galaxy clusters to study dark matter interactions, using optical indicators and X-ray observations. This method efficiently identifies active clusters suitable for detailed dark matter studies.

The overlay for this one looks like this:

The official version of the paper can be found on arXiv here and the Fediverse announcement here:

https://fediscience.org/@OJ_Astro/116730279994960097

The third and final paper of the week, published on Friday 12the June in the folder Earth and Planetary Astrophysics, is “JCMT Constraints on the Early-Time HCN and CO Emission and HCN Temporal Evolution of 3I/ATLAS” by Jason T. Hinkle (U. Illinois, USA) and 6 others based in the USA and Chile. This article presents observations of the third Interstellar Object, 3I/ATLAS, providing early sub-mm constraints on its activity. The findings suggest a steeper production rate slope than typical Solar System comets.

The overlay for this one is here:

The final, accepted version can be found on arXiv here and the Mastodon announcement is here:

https://fediscience.org/@OJ_Astro/116735805179724489

And that concludes this week’s update. It has been a slow week on the publishing front, but the main reason is that we have a big backlog of papers accepted but waiting for the authors to put their final versions on arXiv and we can’t do anything about that! I’ll do another update next Saturday.

This is a really interesting result [1]! We knew Comet 3I/ATLAS was an interstellar object because of its orbit, but the precise measurements done with ALMA by a team lead by a Ph.D. student (Luis E. Salazar Manzano from the University of Michigan), and supervised by Chilean assistant professor Teresa Paneque-Carreño [3], really show that its chemistry does not belong in our solar system.

In particular, the team found that 3I/ATLAS contains *at least 30 times* the proportion of semi-heavy water* found in comets from our own Solar System, which clearly indicates a different chemical history. The chemical processes leading to the enrichment of HDO usually require environments colder than about 30 Kelvin, which means the solar system in which 3I/ATLAS originated was colder than ours.

And this could be found because ALMA could observe the comet right after its perihelion, quite close to the sun, but observable with a radio telecope!

*Semi-heavy water [4] is water made with one atom of the most common isotope of hydrogen (protium), one atom of Deuterium (the next most common isotope of hydrogen, containing one proton and one neuron), and oxygen. It is sometimes called HDO, with D standing for Deuterium, or ¹H²HO. Compare with heavy water, which is made of two atoms of Deuterium and Oxygen, or D₂O (or ²H₂O).

#ALMA #AtacamaLargeMillimeterArray #AtacamaLargeMillimeterSubmillimeterArray #Comet3IATLAS #SolarSystemFormation #InterstellarObjects

[1] https://www.almaobservatory.org/en/press-releases/alma-reveals-interstellar-comet-3i-atlas-formed-in-a-far-colder-world-than-our-own/
[2] https://lsa.umich.edu/astro/people/graduate-students/lesamz.html
[3] https://terepaneque.com/info_english/
[4] https://en.wikipedia.org/wiki/Semiheavy_water