Wed 16 Jul 13:15: Chasing the First Stars With Outliers
he OUTLIERS project aims to find and study the most ancient stars in our Galaxy — stars that formed shortly after the Big Bang. These stars carry unique chemical fingerprints that tell us about the very first generations of stars, the first supernovae, and the early stages of galaxy formation. Although extremely rare and faint, they can still be found today thanks to the combined power of Gaia — which maps the positions and motions of over a billion stars — and new large spectroscopic surveys like DESI , WEAVE, and 4MOST. OUTLIERS uses this data to select and follow up the most promising candidates. By studying these stellar fossils in detail, we hope to answer long-standing questions about how the first stars formed, what elements they created, and how the Universe evolved in its earliest phases.
- Speaker: David Aguado, Instituto de Astrofísica de Canarias
- Wednesday 16 July 2025, 13:15-13:45
- Venue: Hoyle Lecture theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: Cristiano Longarini.
Hubble Snaps Galaxy Cluster’s Portrait
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Hubble Snaps Galaxy Cluster’s Portrait This NASA/ESA Hubble Space Telescope image features the galaxy cluster Abell 209. ESA/Hubble & NASA, M. Postman, P. KellyA massive, spacetime-warping cluster of galaxies is the setting of today’s NASA/ESA Hubble Space Telescope image. The galaxy cluster in question is Abell 209, located 2.8 billion light-years away in the constellation Cetus (the Whale).
This Hubble image of Abell 209 shows more than a hundred galaxies, but there’s more to this cluster than even Hubble’s discerning eye can see. Abell 209’s galaxies are separated by millions of light-years, and the seemingly empty space between the galaxies is filled with hot, diffuse gas that is visible only at X-ray wavelengths. An even more elusive occupant of this galaxy cluster is dark matter: a form of matter that does not interact with light. Dark matter does not absorb, reflect, or emit light, effectively making it invisible to us. Astronomers detect dark matter by its gravitational influence on normal matter. Astronomers surmise that the universe is comprised of 5% normal matter, 25% dark matter, and 70% dark energy.
Hubble observations, like the ones used to create this image, can help astronomers answer fundamental questions about our universe, including mysteries surrounding dark matter and dark energy. These investigations leverage the immense mass of a galaxy cluster, which can bend the fabric of spacetime itself and create warped and magnified images of background galaxies and stars in a process called gravitational lensing.
While this image lacks the dramatic rings that gravitational lensing can sometimes create, Abell 209 still shows subtle signs of lensing at work, in the form of streaky, slightly curved galaxies within the cluster’s golden glow. By measuring the distortion of these galaxies, astronomers can map the distribution of mass within the cluster, illuminating the underlying cloud of dark matter. This information, which Hubble’s fine resolution and sensitive instruments help to provide, is critical for testing theories of how our universe evolved.
Text Credit: ESA/Hubble
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Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD
- Hubble Space Telescope
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Focusing in on Gravitational Lenses
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NASA’s James Webb Space Telescope Inspects Cat’s Paw
NASA’s James Webb Space Telescope team released this image of the Cat’s Paw Nebula on July 10, 2025, in honor of the telescope’s third anniversary. Webb’s NIRCam (Near-Infrared Camera) revealed never-before-seen structural details and features: Massive young stars carve away at nearby gas and dust, while their bright starlight produces a bright nebulous glow represented in blue. As a consequence of these massive stars’ lively behavior, the local star formation process will eventually come to a stop.
Take a tour through this section of the Cat’s Paw Nebula.
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Fri 18 Jul 11:30: Dust grains across the universe: JWST and ALMA insights from cosmic noon to the early universe
Abstract not available
- Speaker: Irene Shivaei (CAB, Madrid)
- Friday 18 July 2025, 11:30-12:30
- Venue: Ryle Seminar Room, KICC + online.
- Series: Galaxies Discussion Group; organiser: Sandro Tacchella.