MPI für Radioastronomie<p>✨During the <a href="https://astrodon.social/tags/Christmas" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Christmas</span></a> season, we often think of <a href="https://astrodon.social/tags/wonders" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>wonders</span></a> and the invisible🪄 that connects our world. Did you know that scientists are searching for an invisible wonder - but in the <a href="https://astrodon.social/tags/universe" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>universe</span></a>? 🌌 <a href="https://astrodon.social/tags/Axions" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>Axions</span></a>, the promising candidates for Dark Matter (DM)🖤, are ultra-light particles with masses around 10⁻²² eV and wavelengths of about one kiloparsec (~ 3x10¹⁶ km).</p><p>Particles with similar properties to axions are called "axion-like particles" (ALPs). 💡ALPs, which include ultra-light axions, can alter <a href="https://astrodon.social/tags/light" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>light</span></a> polarization – meaning the alignment of <a href="https://astrodon.social/tags/lightwaves" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>lightwaves</span></a>. During an internship with us, Sarah searched for such phenomena in low-frequency <a href="https://astrodon.social/tags/LOFAR" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>LOFAR</span></a> data 📡 from the pulsar PSR J0332+5434. Low frequencies📉 are ideal, as the ionosphere – an electron layer in the Earth's atmosphere 🌍, caused by solar radiation – creates interference that can be removed from low-frequency LOFAR data through calibration.</p><p>According to theories, axions apperars in strong magnetic fields, such as in <a href="https://astrodon.social/tags/stellar" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>stellar</span></a> cores, where they can escape because they interact very weakly with normal matter. Just like DM 🖤.</p><p>Similarly, pulsars have extremely strong static magnetic fields. When cosmic ALPs enter a strong <a href="https://astrodon.social/tags/magneticfield" class="mention hashtag" rel="nofollow noopener noreferrer" target="_blank">#<span>magneticfield</span></a>, they can be converted into photons – that is, light 🌟 – and thus become detectable, if ultra-light axions exist.</p><p>Currently, there are three methods for searching for ALPs:<br>1️⃣ Helioscopes for solar ALPs (e.g. IAXO, 🖥️ 1) ☀️,<br>2️⃣ Haloscope searches in the galactic halo 🌌 (e.g. observing radiopulsars, 🖥️ 2), and<br>3️⃣ Generating ALPs in the lab 🔬 (e.g. ALPS II, <span class="h-card" translate="no"><a href="https://helmholtz.social/@DESY" class="u-url mention" rel="nofollow noopener noreferrer" target="_blank">@<span>DESY</span></a></span> , 🖥️ 3).<br>© S.Pappert, E.Moerova | MPIfR</p>