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Denis Erkal

@derkal.bsky.social
534 followers 255 following 126 posts

Astrophysicist working on dark matter, near-field cosmology, and galaxy formation. All opinions are my own. He/him.

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Denis Erkal @derkal.bsky.social · 08/09/2026
See openai.com/index/navier... for OpenAI’s description of how they solved the problem. What can we do in Astro with tools like this?🧪☄️
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Denis Erkal @derkal.bsky.social · 08/09/2026
Holy forking shit. This is seriously impressive. Some controversy here since Levent Alpöge and Tristan Buckmaster solved this problem with AI as well (see mastodon.social/@tristanbuck...) and their solution has been fed into Codex. But either way, amazing what humans with AI can do!🧪☄️
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Denis Erkal @derkal.bsky.social · 23/07/2026
One week left to apply for this position on stellar streams. Happy to answer any questions so please let me know! aas.org/jobregister/...
aas.org
Research Fellow in Stellar Streams | American Astronomical Society
The University of Surrey is a global community of ideas and people, dedicated to life-changing education and research.  We are ambitious and have a bold vision of what we want to achieve - shaping our...
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Oliver Newton @musicalneutron.bsky.social · 14/07/2026
Come and work at Surrey! 😀
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Denis Erkal @derkal.bsky.social · 14/07/2026
And now the AAS job link: aas.org/jobregister/.... Please let me know if you have any questions about the position! 🔭☄️🧪
aas.org
Research Fellow in Stellar Streams | American Astronomical Society
The University of Surrey is a global community of ideas and people, dedicated to life-changing education and research.  We are ambitious and have a bold vision of what we want to achieve - shaping our...
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Michelle Collins @runningastronomer.bsky.social · 10/07/2026
A great opportunity to come work with Denis, Eugene and the Surrey Astro team! 🧪☄️🔭
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Denis Erkal @derkal.bsky.social · 10/07/2026
Interested in a 3 year postdoc working on stellar streams and dark matter? Come join our amazing Astro group in Surrey to work with me and Eugene Vasiliev. Details here and the deadline is July 30th. Let me know if you have any questions! jobs.surrey.ac.uk/vacancy.aspx... 🧪🔭☄️
jobs.surrey.ac.uk
Job Vacancy at the University of Surrey: Research Fellow in Stellar Streams
The University of Surrey is a global community of ideas and people, dedicated to life-changing education and research. We are ambitious and have a bold vision of what we want to achieve - shaping ours...
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Denis Erkal @derkal.bsky.social · 29/06/2026
Interested in working on stellar streams in the UK? I’ll be posting a 3 year postdoc position to work with me and Eugene Vasiliev on measuring dark matter subhalo properties with streams in a few days. Interviews will be in early August with a start date of October 1st. 🧪☄️
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Emily Hunt @emily.space · 24/06/2026
The group in Surrey is absolutely lovely (I visited them last month) so I can highly recommend them!
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Payel Das @payeldas.bsky.social · 24/06/2026
Want to join Surrey Astro? Get in touch if you want to learn more.
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Denis Erkal @derkal.bsky.social · 15/06/2026
Interested in applying for Astro fellowships in the UK? Come to Surrey! We are a fun group and will help you hone your application. Our deadline for ERF/URF consideration is July 8th. For more details of all the fellowships and how to contact us, see www.surrey.ac.uk/astrophysics... 🔭☄️
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Denis Erkal @derkal.bsky.social · 11/06/2026
Here’s our press release about Arrakihs! Lots of cool science will hopefully come out of it and I’m especially excited about what can be done with the long streams it will detect. 🔭☄️🧪 www.surrey.ac.uk/news/esa-off...
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Denis Erkal @derkal.bsky.social · 10/06/2026
Forgot the tags! 🔭☄️🧪
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Denis Erkal @derkal.bsky.social · 10/06/2026
The Arrakihs mission has been adopted as ESA's next F-class mission, with an expected launch in 2030! It will look at the low surface brightness outskirts of 80 Milky Way-like galaxies. www.esa.int/Science_Expl...
esa.int
ESA adopts galactic archaeology mission Arrakihs
The European Space Agency’s (ESA) Science Programme Committee has adopted the Arrakihs mission. Planned for launch by the end of 2030, Arrakihs will capture the faint light from nearby galaxy haloes. ...
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Laura Lopez @ohdearz.bsky.social · 13/11/2025
Honored to receive the 2026 American Physical Society Edward A. Bouchet Award! To see how the DEI ban in Ohio influences our university, please see the OSU announcement of the award (left) vs the actual APS citation for the award (right).
Lopez receives physics award
Laura Lopez, a professor in the Department of Astronomy, is the recipient of the 2026 Edward A. Bouchet Award from the American Physical Society. The award honors Lopez’s pioneering contributions to X-ray astronomy, as well as her transformative leadership of mentoring programs for undergraduates, graduate students and postdocs.Laura A. Lopez, The Ohio State University
2026 recipient, Edward A. Bouchet Award
For pioneering contributions to X-ray astronomy, including foundational studies of supernova remnants, compact objects, and stellar feedback in galaxies, and for transformative leadership in advancing equity and inclusion in physics through innovative mentorship programs, national advocacy, and unwavering support for students from historically marginalized communities.
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NSF–DOE Rubin Observatory @rubinobservatory.org · 24/10/2025
We come with receipts🧾 Tidal tails are cosmic “receipts” of galactic drama, showing who collided with whom. Rubin's camera is sharp enough to catch wind of even the faintest intergalactic tea. No need to worry about "pics or it didn't happen" with Rubin keeping a close eye 😎 🔭🧪
A sprawling field of galaxies fills the deep black of space, dotted with glowing stars and colorful smudges of light. Near the top, a smooth golden elliptical galaxy glows like polished stone, linked by delicate, taffy-like streams of stars to nearby galaxies below—evidence of ancient cosmic collisions.
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Marcel S. Pawlowski @8minutesold.bsky.social · 09/10/2025
Paper day! My PhD student Mariana Júlio, with @readdark.bsky.social, @pengfeili.bsky.social and others, studies the internal dynamics of dwarf galaxies and finds they don't agree with the Radial Acceleration Relation, challenging the dark matter alternative MOND. arxiv.org/abs/2510.06905 🔭☄️🧪 1/7
arxiv.org
The radial acceleration relation at the EDGE of galaxy formation: testing its universality in low-mass dwarf galaxies
A tight correlation between the baryonic and observed acceleration of galaxies has been reported over a wide range of mass ($10^8 < M_{\rm bar}/{\rm M}_\odot < 10^{11}$) - the Radial Acceleration Rela...
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Denis Erkal @derkal.bsky.social · 30/09/2025
4MOST’s social media account is live! First light expected on October 21st! (1pm UK time) 🔭🧪
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Michael Merrifield @astromikemerri.bsky.social · 20/09/2025
Let us name those who should take responsibility for this situation. The senior management of universities failed to negotiate a sustainable system of funding, and then sleep-walked into mess. But will they be held accountable? Of course not. www.theguardian.com/education/20...
theguardian.com
Quarter of UK university physics departments at risk of closing, survey finds
Four out of five making staff cuts as physicists say findings are ‘great concern’ for UK’s leadership in important areas
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Denis Erkal @derkal.bsky.social · 22/08/2025
Here’s the Cygnus loop with a Seestar S50. It’s so big that one mosaic won’t fit it so I stitched two of them together. The total exposure is about 4 hours. It would be cool to go even wider and deeper. 🔭
Picture of the Cygnus loop showing lots of stars and thin clouds of gas which came from a supernova explosion
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Stephen Green @stephenrgreen.bsky.social · 17/08/2025
@aircanada.bsky.social
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Stephen Green @stephenrgreen.bsky.social · 17/08/2025
Stranded in Italy thanks to Air Canada. They say by email that they can't find any flights in the next three days and offer a refund -- ignoring EU 261/2004 regulations that they have to rebook on *any* airline. They do not answer the phone. AC has absolute contempt for its customers and employees.
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The StarXiv ✨ podcast @starxiv.bsky.social · 04/08/2025
Episode 17 has dropped! Tune in to hear Payel & Michelle talk about about a dark matter subhalo detection, the problem(s) with super massive black holes, massive star clusters in the Sparkler, speedy white dwarfs and more! 🔭☄️ starxiv.com/2025/08/04/e...
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Denis Erkal @derkal.bsky.social · 24/07/2025
Anyone else notice any weird unit issues with Google lately? (3e19 m)/(1 kpc) gives 55.7 instead of ~1. Not good if you like using Google for quick unit conversions 🔭
Screen shot of a Google search showing (3e19 m)/(1 kpc) gives 55.7
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Michele Bannister @astrokiwi.bsky.social · 02/07/2025
New potential interstellar object in the South: 168 hr arc but e already 9+/-1. H=11. Follow-up encouraged! 🔭
cneos.jpl.nasa.gov
Scout: NEOCP Hazard Assessment
NASA's Near-Earth Object (NEO) web-site. Data related to Earth impact risk, close-approaches, and much more.
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Paul McMillan @mcmillan-astro.bsky.social · 30/06/2025
Non-hot take: The "AI will kill us" discourse was a distraction from the real problem: it removes the young end of the skilled knowledge workforce. They are harder to train, because AI can do it for them. They can't get jobs, because AI can do it for their bosses. www.theguardian.com/business/202...
theguardian.com
Number of new UK entry-level jobs has dived since ChatGPT launch – research
Vacancies for graduate jobs, apprenticeships, internships and junior jobs with no degree requirement have dropped 32%, Adzuna finds
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Denis Erkal @derkal.bsky.social · 26/06/2025
Come join us at Surrey! Please get in touch with questions on any of the fellowships (junior to senior), and if you're interested but not sure what you're eligible for, contact me. 🔭
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Denis Erkal @derkal.bsky.social · 23/06/2025
Wow, look at that increase in depth!
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NSF–DOE Rubin Observatory @rubinobservatory.org · 23/06/2025
Introducing...your sneak peek at the cosmos captured by NSF–DOE Vera C. Rubin Observatory! Can you guess these regions of sky? This is just a small peek...join us at 11am US EDT for your full First Look at how Rubin will #CaptureTheCosmos! 🔭🧪 #RubinFirstLook ls.st/rubin-first-look-livestream
A sprawling, textured field of galaxies scattered across the deep black of space. It is filled with the delicate smudges and glowing cores of galaxies of many shapes, sizes and colors, as well as the bright multi-colored points of stars. The image focuses on a collection of interacting galaxies connected by delicate streams of stars. At top center lies a large elliptical galaxy that is dense and smooth, like a polished stone glowing with golden light. Like delicate spider silk or stretched taffy, these stellar bridges link the large elliptical to the few larger galaxies beneath, evidence of past collisions.

All throughout the image, thousands of galaxies gather in clusters or are spread throughout, like glittering gems strewn on a table. Some are sharp-edged and spiral, like coiled ribbons; others round and diffuse, like polished pebbles. Still others are just smudges of various colors against the black of space. The background is peppered with pinpoint stars in reds, yellows, and blues, crisp against the velvet black. A cosmic tapestry of glowing tan and pink gas clouds with dark dust lanes. In the upper right, the Trifid Nebula resembles a small flower in space. Its soft, pinkish gas petals are surrounded by blue gas, and streaked with dark, finger-like veins of dust that divide it into three parts. It radiates a gentle, misty glow, diffuse and soft like the warmth of breath on a cold hand. To the lower left, the much larger Lagoon Nebula stretches wide like a churning sea of magenta gas, with bright blue, knotted clumps sprinkled throughout where new stars are born. Both nebulae are embedded in a soft tan backdrop of gas that is brighter on the left than on the right, etched with dark tendrils of dust and sprinkled with the pinpricks of millions of stars.A sprawling, textured field of galaxies scattered across the deep black of space. It is filled with the delicate smudges and glowing cores of galaxies of many shapes, sizes and colors, as well as the bright multi-colored points of stars. To the lower left is a region filled with the hundreds of golden glittering gems of a distant galaxy cluster. In the foreground, below and right of center, two blue spiral galaxies look like eyes beneath the entangled mass of a triple galaxy merger in the upper right. A few bright blue points of foreground stars pierce the glittering tapestry.

All throughout the image, thousands of galaxies gather in clusters or are spread throughout, like glittering gems strewn on a table. Some are sharp-edged and spiral, like coiled ribbons; others round and diffuse, like polished pebbles. Still others are just smudges of various colors against the black of space. The background is peppered with pinpoint stars in reds, yellows, and blues, crisp against the velvet black.
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Denis Erkal @derkal.bsky.social · 17/06/2025
Considering a senior UK fellowship (ERF, URF)? We have a great group at Surrey and our internal deadline for the ERF is July 8th. We are looking for a light-touch application: CV and 1 page research statement. I'm the contact person, so send questions/material to me www.ukri.org/what-we-do/d... 🔭
ukri.org
Ernest Rutherford Fellowships
Ernest Rutherford Fellowships (ERF) enables early career researchers with clear leadership potential to establish a strong, independent research programme. They encourage talented researchers in UK un...
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Denis Erkal @derkal.bsky.social · 01/06/2025
Really good set of slides about how Nazi scientists did very little to combat the Nazi party
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Chris Lintott @chrislintott.bsky.social · 17/04/2025
An astonishing headline reporting on new observations from a team led to Nikku Madhusudhan claims they’ve found ‘hints of life’ on a planet orbiting a dwarf star some 124 light years away. What’s going on? (1/n) www.bbc.co.uk/news/article... 🔭 🧪
bbc.co.uk
Promising hints of life found on distant planet K2-18b
Scientists find new but tentative evidence that a faraway world orbiting another star may be home to life.
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Peter Coles 🏳️‍🌈 🏳️‍⚧️ 🇮🇪 @telescoper.bsky.social · 13/04/2025
Bullying at Cambridge University There's a long article in today's Observer about bullying at Cambridge University, which I encourage you to read, as it shows that the scale of the bullying problem in Cambridge is very worrying. I'll just emphasize a couple of things here. One is that Cambridge…
telescoper.blog
Bullying at Cambridge University
There's a long article in today's Observer about bullying at Cambridge University, which I encourage you to read, as it shows that the scale of the bullying problem in Cambridge is very worrying. I'll just emphasize a couple of things here. One is that Cambridge University is due to elect a new Chancellor this year and, as is mentioned in the Observer, Professor Wyn Evans of the Institute of Astronomy is planning to stand as a candidate on an anti-bullying platform.
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Denis Erkal @derkal.bsky.social · 12/04/2025
I tried to image the Palomar 5 globular cluster with a Seestar S50 for 3 hours. The cluster is the middle of this image and some of the faintest stars have Gaia G mags of ~17.5 and the right proper motions to be Pal 5 stars. 🔭
Seestar image of Palomar 5 showing a few bright stars and many faint stars
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Denis Erkal @derkal.bsky.social · 04/04/2025
Great book review by @chanda.bsky.social about another disappointing physicist, Roger Penrose, who didn’t treat their family or female students well.
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Denis Erkal @derkal.bsky.social · 31/03/2025
Spent 4 hours on NGC 4631 (top galaxy, aka Whale galaxy) and NGC 4656 (bottom galaxy, aka Hockey stick galaxy) with a seestar last night. The hook in NGC 4656 is due to an interaction with other galaxies in the group. 🔭
Image of two galaxies. The whale galaxy on the top is a long edge-on disk. The bottom galaxy, the hockey stick galaxy, shows a sharp hook due to an interaction with another galaxy in the group.
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Denis Erkal @derkal.bsky.social · 29/03/2025
Today’s solar eclipse from the southern UK. It was taken with a seestar 50. I was very impressed how well it kept the sun centered in the timelapse! 🔭 youtube.com/shorts/f-wsa...
Photo of the eclipse during showing a part of the sun obscured by the moon. Looks a bit like a Pac-Man
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Denis Erkal @derkal.bsky.social · 29/03/2025
Reposting to 🔭
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ARRAKIHS @arrakihs-mission.eu · 28/03/2025
Denis Erkal (@derkal.bsky.social), one of our contributors, is an expert in galaxy modeling at the @uniofsurrey.bsky.social He has given a talk focused on the Milky Way’s formation and dark matter properties 🌌 #ARRAKIHS #GalaxyModels #DarkMatter #MilkyWay
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Denis Erkal @derkal.bsky.social · 21/03/2025
Paper day with a paper led by Connor Hainje: arxiv.org/abs/2503.15589. We studied how different the Sagittarius stream would look in self-interacting dark matter. In SIDM, ram pressure can evaporate Sgr's dark matter halo, leading to rapid mass loss, which changes the stream morphology. 1/ 🔭 🧪
arxiv.org
Effects of Dark Matter Self Interactions on Sagittarius and Its Stream
This work explores how assumptions regarding the particle-physics nature of dark matter can alter the evolution of the Sagittarius (Sgr) dwarf spheroidal galaxy and its expansive stellar stream. We ru...
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Denis Erkal @derkal.bsky.social · 02/03/2025
I also got this nice image of the Orion Nebula. The framing options are quite nice on the seestar and are great for large objects on the sky. 🔭
Image of the Orion Nebula showing a bright cloud in the center and stars in the outskirts.
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Denis Erkal @derkal.bsky.social · 02/03/2025
I played a bit more with our department’s seestar and got this image of M3. The AIdenoise seems to pick out the stars resolved in the original image quite well. 🔭
Image of the M3 globular cluster which shows a dense clump of stars in the middle of the field and a lower density of stars from the Milky Way farther away
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Sean Carroll @seanmcarroll.bsky.social · 15/02/2025
Congratulations to Bob Wald for winning the Albert Einstein medal! physicalsciences.uchicago.edu/news/article...
physicalsciences.uchicago.edu
Robert Wald awarded 2025 Albert Einstein Medal | News | Physical Sciences Division | The University of Chicago
The UChicago Physical Sciences Division fosters an inclusive and creative research environment and shapes the next generations of scientists and mathematicians.
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Denis Erkal @derkal.bsky.social · 30/01/2025
Had some fun tonight learning how to use one of our department’s seestar telescopes. They’re super easy to set up and use. I think our students will enjoy imaging galaxies with these! 🔭
Image of the whirlpool galaxy
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Prof Stephen Serjeant @stephenserjeant.bsky.social · 28/01/2025
UK universities desperately need the government to wake up to the crisis unfolding in the higher education sector. Income has been throttled for a decade and now parts are dying
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European Space Agency @esa.int · 15/01/2025
The ESA #Gaia mission has delivered the best Milky Way maps to date and taken its last starlight before spacecraft retirement 🔭 www.esa.int/Science_Expl...
A model image of what our home galaxy, the Milky Way, might look like face-on: as viewed from above the disc of the galaxy, with its spiral arms and bulge in full view. In the centre of the galaxy, the bulge shines as a hazy oval, emitting a faint golden gleam. Starting at the central bulge, several glistening spiral arms coil outwards, creating a perfectly circle-shaped spiral. They give the impression of someone having sprinkled pastel purple glitter on the pitch-black background, in the shape of sparkling, curled-up snakes.A model image of what our home galaxy, the Milky Way, might look like edge-on, against a pitch-black backdrop. The Milky Way’s disc appears in the centre of the image, as a thin, dark-brown line spanning from left to right, with the hint of a wave in it. The line appears to be etched into a thin glowing layer of silver sand, that makes it look as if it was drawn with a coloured pencil on coarse paper. The bulge of the galaxy sits like a glowing, see-through pearl in the shape of a sphere in the centre of this brown line
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Denis Erkal @derkal.bsky.social · 15/01/2025
Farewell Gaia! It’s impressive how much we’ve learned from just 33 months of data and I can’t wait to see what else is hiding in the full data!
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Denis Erkal @derkal.bsky.social · 11/12/2024
Congratulations to my PhD student Madison Walder on her successful viva!
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Michele Bannister @astrokiwi.bsky.social · 25/11/2024
New submitted paper day! Led by @redshiftless.bsky.social, with me, @chrislintott.bsky.social, Simon Portegies Zwart, and four of the postgrad students in our group. We explore a beautiful new phenomena: what happens to interstellar objects as they drift out from their star & wander the Galaxy? 🔭🧪🧵
arxiv.org
He awa whiria: the tidal streams of interstellar objects
Upcoming surveys are likely to discover a new sample of interstellar objects (ISOs) within the Solar System, but questions remain about the origin and distribution of this population within the Galaxy...
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Denis Erkal @derkal.bsky.social · 19/11/2024
Two postdoc positions on gravitational waves at Nottingham with Stephen Green 🔭
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