169. A billion radial velocities: DR3 includes 33 million radial velocities. DR4, in 2025, should have 100 million. A recent study has derived 125 million (of much lower accuracy) from the low-res BP/RP spectra, with perhaps 1–2 billion in the future. wix.to/nWiwd2f

2/ Called BH3, the #BlackHole was discovered by ESA Gaia 🛰️ because it imposes an odd wobbling motion on the star orbiting it ⭐️⚫️ Ground-based telescopes, including ESO’s #VLT 🔭, then found its mass to be 33 times that of the Sun. Artist’s animation of the system 👇

Paper day: arxiv.org/abs/2404.11604 We show that Gaia BH3 is part of the ED-2 star cluster. The update astrometry puts GaiaBH3 in excellent agreement with the orbit of ED-2. Using some ESO data we got last period we also show that ED-2 is very likely a disrupted globular cluster

Galactic map of #StellarStreams detected in the ESA Gaia dataset. Each star in the stream represents an actual Gaia source, color-coded by heliocentric distance (as computed by the STREAMFINDER algorithm): blue for nearer (~1 kpc) and red for distant (>~30 kpc).

Our paper on the discovery of five dwarf galaxies around the galaxy NGC 253, found by Giuseppe Donatiello in the DESI Survey deep imaging, is available today in: arxiv.org/pdf/2405.03769. This result gives new insights on the presence of a satellite plane in this Sculptor group spiral.

A talk I gave for the "International Astronomical Union (IAU) Commission H1 - The Local Universe" seminar, on the topic "Atlas of Milky Way mergers created using the ESA Gaia dataset". youtu.be/soabSPRFims?t=…

A webinar I gave Swinburne University of Technology, hosted by Prof. Duncan A. Forbes, on "The LMS1 stellar stream: A very metal-poor fossil remnant of our Galaxy's formation". youtube.com/watch?v=6mtrAz…

Paper day! With Viktor Hrannar Jónsson looking at velocities of stars in the Milky Way's warp. We find that they just don't match the picture of a steadily precessing warp where we see it today. arxiv.org/abs/2405.09624

The paper I have been working on for a while is out! In this one I predicted the detectability of Globular Clusters in the full 6-year Euclid survey! And then tested detection models and size measurement using the first ERO data on the Fornax Cluster! arxiv.org/abs/2405.14015

What stellar substructures does Gaia map? This visualisation of the Milky Way by Stefan Payne-Wardenaar / Khyati Malhan highlights globular clusters, dwarf galaxies and stellar streams. Notice also Shakti & Shiva, subjects of a recent story: esa.int/Science_Explor… youtu.be/YQDfdpT6yZ4

Paper thread!! This was up on arXiv a bit over a week ago: arxiv.org/abs/2405.13124 We show here the dynamical analysis of the first spectroscopic follow-up of extremely metal-poor stars using photometric metallicities based on Gaia XP CaHK magnitudes run on Pristine survey model

The Gaia-Sausage/Enceladus stars, which were previously hypothesized to have originated from an ancient (8-11 Gyrs ago) merger event, likely came from a more recent (< 3 Gyrs ago) event, now dubbed as the Virgo Radial Merger (VRM).

Evolution of merger stars in the (Lz, E) space of a Milky Way analog in the TNG 50 cosmological simulation. youtube.com/watch?v=qGNtSW…

The GD-1 stream surrounded by a "stellar cocoon" in the DESI Survey data! By Monica Valluri et al.

A schematic overview of MW-mass satellite systems in Local group and beyond (taken from arxiv.org/pdf/2404.14498) #dwarfgalaxies2024 conference in #Durham

In our new paper today (arxiv.org/abs/2407.20483), we report the catalog and photometry of the extragalactic tidal streams found in Dark Energy Survey as part of the Stellar Stream Legacy Survey. A comparison of the stream frequency with cosmological models is coming very soon!

Our paper made it to the “Selections from 2024” series that looks back at some of the most-read AAS journal articles published in 2024!

Today marks Gaia's end of observations: cosmos.esa.int/en/web/gaia/en…. Gaia now performs a set of technology tests to help future missions: cosmos.esa.int/en/web/gaia/te…. The most up to date view of our Milky Way was created thanks to Gaia, with much more to come with #GaiaDR4 + #GaiaDR5.

Milky Way’s Metal-Poor Stars display Chemical Transition near the Solar Radius. Accepted in ApJL. arxiv.org/abs/2508.08360 Results obtained using the data from ESA Gaia and APOGEE Survey .