Only a handful of observations truly constrain the nature of dark matter, which is why dozens of different physical models are still viable. Several of the most popular alternatives predict that dark matter halos slowly “thermalize” over time, gradually changing shape and expanding until they form a central region of nearly constant density -- a core. This transformation would not occur if the dark matter particles were completely collision-less, as assumed in the standard model. Therefore, the presence or absence of such a core provides a powerful way to distinguish between the standard

The Near-Infrared Spectrometer and Photometer (NISP) on board the Euclid space mission has obtained near-infrared (NIR) spectra of millions of objects, including hundreds of ultracool dwarfs (UCDs). Euclid observations retrieve images and slitless spectra simultaneously. This observing mode marks a new era in the discovery of new objects, such as L- and T-type dwarfs, which can be found from direct identification through the H2O and CH4 absorption bands. NISP spectral resolution (R ∼ 450) is enough to classify the objects by the spectral type using known standard templates. Q1 provided more