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Simulating supermassive black holes: from event horizon to cosmic web and back again

Abstract not available

• Speaker: Martin Bourne (Hertfordshire)
• Friday 07 March 2025, 11:30-12:30
• Venue: Ryle Seminar Room, KICC + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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arXiv:2502.18651v1 Announce Type: new Abstract: In this second paper on the variability survey of central stars of planetary nebulae (CSPNe) using ZTF, we focus on the 11 long-timescale variables with variability timescales ranging from months to years. We also present preliminary analyses based on spectroscopic and/or photometric follow-up observations for six of them. Among them is NGC 6833, which shows a 980 day periodic variability with strange characteristics: 'triangle-shaped' brightening in $r$, $i$, and WISE bands but almost coincidental shallow dips in the $g$-band. We speculate this to be a wide but eccentric binary with the same orbital period. Long-period near-sinusoidal variability was detected in two other systems, NGC 6905 and Kn 26, with periods of 700 days and 230 days, respectively, making them additional wide-binary candidates. The latter also shows a short period at 1.18 hours which can either be from a close inner binary or pulsational origin. We present CTSS 2 and PN K 3-5 which show brightening and significant reddening over the whole ZTF baseline. A stellar model fit to the optical spectrum of CTSS 2 reveals it to be one of the youngest post-AGB CSPN known. Both show high-density emission-line cores. These appear to be late thermal pulse candidates, currently evolving towards the AGB phase, though alternative explanations are possible. We then present recent HST/COS ultraviolet spectroscopy of the known wide-binary candidate LoTr 1 showing that the hot star is a spectroscopic twin of the extremely hot white dwarf in UCAC2 46706450. We think that the long photometric period of 11 years is the binary orbital period. Finally, we briefly discuss the ZTF light curves of the remaining variables, namely Tan 2, K 3-20, WHTZ 3, Kn J1857+3931, and IPHAS J1927+0814. With these examples, we present the effectiveness of the von Neumann statistics and Pearson Skew-based metric space in searching for long-timescale variables.

arXiv:2502.18651v1 Announce Type: new Abstract: In this second paper on the variability survey of central stars of planetary nebulae (CSPNe) using ZTF, we focus on the 11 long-timescale variables with variability timescales ranging from months to years. We also present preliminary analyses based on spectroscopic and/or photometric follow-up observations for six of them. Among them is NGC 6833, which shows a 980 day periodic variability with strange characteristics: 'triangle-shaped' brightening in $r$, $i$, and WISE bands but almost coincidental shallow dips in the $g$-band. We speculate this to be a wide but eccentric binary with the same orbital period. Long-period near-sinusoidal variability was detected in two other systems, NGC 6905 and Kn 26, with periods of 700 days and 230 days, respectively, making them additional wide-binary candidates. The latter also shows a short period at 1.18 hours which can either be from a close inner binary or pulsational origin. We present CTSS 2 and PN K 3-5 which show brightening and significant reddening over the whole ZTF baseline. A stellar model fit to the optical spectrum of CTSS 2 reveals it to be one of the youngest post-AGB CSPN known. Both show high-density emission-line cores. These appear to be late thermal pulse candidates, currently evolving towards the AGB phase, though alternative explanations are possible. We then present recent HST/COS ultraviolet spectroscopy of the known wide-binary candidate LoTr 1 showing that the hot star is a spectroscopic twin of the extremely hot white dwarf in UCAC2 46706450. We think that the long photometric period of 11 years is the binary orbital period. Finally, we briefly discuss the ZTF light curves of the remaining variables, namely Tan 2, K 3-20, WHTZ 3, Kn J1857+3931, and IPHAS J1927+0814. With these examples, we present the effectiveness of the von Neumann statistics and Pearson Skew-based metric space in searching for long-timescale variables.

Nature, Published online: 26 February 2025; doi:10.1038/s41586-024-08565-9

Emplacement of the north polar cap of Mars is investigated by combining viscoelastic deformation calculations and observations, showing that it formed over the last 1.7–12.0 Myr atop a stiff lithosphere and high-viscosity mantle (1022 Pa s), and that glacial isostatic adjustment could be further constrained.

Nature, Published online: 27 February 2025; doi:10.1038/d41586-025-00597-z

Two US probes launched today, one laden with a drill and a hopper looking for lunar water.

arXiv:2502.17556v1 Announce Type: new Abstract: We present optical-to-near infrared (NIR) photometry and spectroscopy of the Type Ia supernova (SN Ia) 2024epr, including NIR spectra observed within two days of first light. The early-time optical spectra show strong, high-velocity Ca and Si features near rarely-observed velocities at $\sim$0.1$c$, and the NIR spectra show a \CI\ "knee." Despite these high-velocity features at early times, SN~2024epr evolves into a normal SN Ia, albeit with stronger peak-light Ca absorption than other SNe Ia with the same light curve shape. Although we infer a normal decline rate, $\Delta m_{15}(B)=1.09\pm0.12$ mag, from the light-curve rise, SN 2024epr is a Branch "cool" object and has red early-time colors ($g-r\approx0.15$ mag at $-10$ days). The high velocities point to a density enhancement in the outer layers of the explosion, but thick-shell He-detonation models do not match the smoothly rising light curve or lack of He in our early-time NIR spectra. No current models (e.g., delayed detonation or thin He shell double detonation) appear to reproduce all of the observed properties. Such constraints are only possible for SN 2024epr from the earliest optical and NIR observations, highlighting their importance for constraining SN Ia models. Finally, we find several other SNe Ia with intermediate mass elements at $\sim$30\,000 km s$^{-1}$ within days after the explosion that evolve into otherwise normal SNe Ia at peak light, suggesting the early-time spectra of SNe Ia may hide a broad diversity of observational characteristics.

arXiv:2502.17556v1 Announce Type: new Abstract: We present optical-to-near infrared (NIR) photometry and spectroscopy of the Type Ia supernova (SN Ia) 2024epr, including NIR spectra observed within two days of first light. The early-time optical spectra show strong, high-velocity Ca and Si features near rarely-observed velocities at $\sim$0.1$c$, and the NIR spectra show a \CI\ "knee." Despite these high-velocity features at early times, SN~2024epr evolves into a normal SN Ia, albeit with stronger peak-light Ca absorption than other SNe Ia with the same light curve shape. Although we infer a normal decline rate, $\Delta m_{15}(B)=1.09\pm0.12$ mag, from the light-curve rise, SN 2024epr is a Branch "cool" object and has red early-time colors ($g-r\approx0.15$ mag at $-10$ days). The high velocities point to a density enhancement in the outer layers of the explosion, but thick-shell He-detonation models do not match the smoothly rising light curve or lack of He in our early-time NIR spectra. No current models (e.g., delayed detonation or thin He shell double detonation) appear to reproduce all of the observed properties. Such constraints are only possible for SN 2024epr from the earliest optical and NIR observations, highlighting their importance for constraining SN Ia models. Finally, we find several other SNe Ia with intermediate mass elements at $\sim$30\,000 km s$^{-1}$ within days after the explosion that evolve into otherwise normal SNe Ia at peak light, suggesting the early-time spectra of SNe Ia may hide a broad diversity of observational characteristics.

Title to be confirmed

Abstract not available

• Speaker: Adrien La Posta (University of Oxford)
• Monday 19 May 2025, 15:00-16:00
• Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
• Series: Cosmology Lunch; organiser: Louis Legrand.

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4 min read

Preparations for Next Moonwalk Simulations Underway (and Underwater)

A new international study partially funded by NASA on how Mars got its iconic red color adds to evidence that Mars had a cool but wet and potentially habitable climate in its ancient past.

Mosaic of the Valles Marineris hemisphere of Mars projected into point perspective, a view similar to that which one would see from a spacecraft. The distance is 2500 kilometers from the surface of the planet, with the scale being .6km/pixel. The mosaic is composed of 102 Viking Orbiter images of Mars. The center of the scene (lat -8, long 78) shows the entire Valles Marineris canyon system, over 2000 kilometers long and up to 8 kilometers deep, extending form Noctis Labyrinthus, the arcuate system of graben to the west, to the chaotic terrain to the east. Many huge ancient river channels begin from the chaotic terrain from north-central canyons and run north. The three Tharsis volcanoes (dark red spots), each about 25 kilometers high, are visible to the west. South of Valles Marineris is very ancient terrain covered by many impact craters.NASA

The current atmosphere of Mars is too cold and thin to support liquid water, an essential ingredient for life, on its surface for lengthy periods. However, various NASA and international missions have found evidence that water was abundant on the Martian surface billions of years ago during a more clement era, such as features that resemble dried-up rivers and lakes, and minerals that only form in the presence of liquid water.

Adding to this evidence, results from a study published February 25 in the journal Nature Communications suggest that the water-rich iron mineral ferrihydrite may be the main culprit behind Mars’ reddish dust. Martian dust is known to be a hodgepodge of different minerals, including iron oxides, and this new study suggests one of those iron oxides, ferrihydrite, is the reason for the planet’s color.

The finding offers a tantalizing clue to Mars’ wetter and potentially more habitable past because ferrihydrite forms in the presence of cool water, and at lower temperatures than other previously considered minerals, like hematite. This suggests that Mars may have had an environment capable of sustaining liquid water before it transitioned from a wet to a dry environment billions of years ago.

“The fundamental question of why Mars is red has been considered for hundreds if not for thousands of years,” said lead author Adam Valantinas, a postdoctoral fellow at Brown University, Providence, Rhode Island, who started the work as a Ph.D. student at the University of Bern, Switzerland. “From our analysis, we believe ferrihydrite is everywhere in the dust and also probably in the rock formations, as well. We’re not the first to consider ferrihydrite as the reason for why Mars is red, but we can now better test this using observational data and novel laboratory methods to essentially make a Martian dust in the lab.”

Laboratory sample showing simulated Martian dust. The ochre color is characteristic of iron-rich ferrihydrite, a mineral that provides crucial insights into ancient water activity and environmental conditions on Mars. The fine-powder mixture consists of ferrihydrite and ground basalt with particles less than one micrometer in size (1/100th diameter of a human hair) (Sample scale: 1 inch across).Adam Valantinas

“These new findings point to a potentially habitable past for Mars and highlight the value of coordinated research between NASA and its international partners when exploring fundamental questions about our solar system and the future of space exploration,” said Geronimo Villanueva, the Associate Director for Strategic Science of the Solar System Exploration Division at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and co-author of this study.

The researchers analyzed data from multiple Mars missions, combining orbital observations from instruments on NASA’s Mars Reconnaissance Orbiter, ESA’s (the European Space Agency) Mars Express and Trace Gas Orbiter with ground-level measurements from NASA rovers like Curiosity, Pathfinder, and Opportunity. Instruments on the orbiters and rovers provided detailed spectral data of the planet’s dusty surface. These findings were then compared to laboratory experiments, where the team tested how light interacts with ferrihydrite particles and other minerals under simulated Martian conditions.

“What we want to understand is the ancient Martian climate, the chemical processes on Mars — not only ancient — but also present,” said Valantinas. “Then there’s the habitability question: Was there ever life? To understand that, you need to understand the conditions that were present during the time of this mineral’s formation. What we know from this study is the evidence points to ferrihydrite forming and for that to happen there must have been conditions where oxygen from air or other sources and water can react with iron. Those conditions were very different from today’s dry, cold environment. As Martian winds spread this dust everywhere, it created the planet’s iconic red appearance.”

Whether the team’s proposed formation model is correct could be definitively tested after samples from Mars are delivered to Earth for analysis.

“The study really is a door-opening opportunity,” said Jack Mustard of Brown University, a senior author on the study. “It gives us a better chance to apply principles of mineral formation and conditions to tap back in time. What’s even more important though is the return of the samples from Mars that are being collected right now by the Perseverance rover. When we get those back, we can actually check and see if this is right.”

Part of the spectral measurements were performed at NASA’s Reflectance Experiment Laboratory (RELAB) at Brown University. RELAB is supported by NASA’s Planetary Science Enabling Facilities program, part of the Planetary Science Division of NASA’s Science Mission Directorate at NASA Headquarters in Washington.

By William Steigerwald

NASA Goddard Space Flight Center, Greenbelt, Maryland

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Details Last Updated Feb 24, 2025 EditorWilliam SteigerwaldContactLonnie Shekhtmanlonnie.shekhtman@nasa.govLocationNASA Goddard Space Flight Center Related Terms

• The Solar System
• Mars

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Asteroid 2024 YR4 had reached a 3.1% likelihood of impact but further data has rendered it negligible

It was a discovery that led to panic-inducing headlines: a giant asteroid found to be hurtling towards Earth that, while unlikely to wipe out life, could do some serious damage.

But now the world can breathe a sigh of relief. After the odds of a future collision rose earlier this year, the likelihood of an impact is now so low as to be negligible.

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The best chance to see as many as possible will be after sunset on Tuesday, Wednesday and Thursday.

2025 Scott Lectures - Lecture 2 Title tbc

Abstract not available

Refreshments will be served after the lecture

• Speaker: Professor Mikhail Lukin, Harvard University
• Wednesday 05 March 2025, 16:00-17:00
• Venue: Ray Dolby Auditorium, Ray Dolby Centre, Cavendish Laboratory, JJ Thomson Avenue, CB3 0US.
• Series: Scott Lectures; organiser: Leona Hope-Coles.

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Astrochemical Origins of Planetary Habitability

Abstract not available

• Speaker: Karin Öberg, Harvard University (Department of Astronomy)​
• Wednesday 14 May 2025, 16:00-17:00
• Venue: East Seminar Room, Ray Dolby Centre.
• Series: LCLU Seminars; organiser: Selen Etingü.

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Since a potentially hazardous asteroid was detected in December, tens of others objects have come close to Earth.

Uplifting Massive Graphs from Minkowski to de Sitter

Identifying useful flat-space limits for cosmological correlators—where they can be expressed in terms of observables in Minkowski space—is nontrivial due to their scale-invariant nature. In this talk, I present a massive flat-space limit in which cosmological correlators, induced by the exchange of heavy fields, can be expressed in terms of massive Feynman graphs in flat space. As a phenomenological application, I apply this flat space limit to compute specific one-loop contributions from heavy fields to primordial non-Gaussianity.

• Speaker: Sadra Jazayeri (Imperial College)
• Monday 03 March 2025, 13:00-14:00
• Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
• Series: Cosmology Lunch; organiser: Thomas Colas.

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This NASA/ESA Hubble Space Telescope reveals clouds of gas and dust near the Tarantula Nebula, located in the Large Magellanic Cloud about 160,000 light-years away.ESA/Hubble & NASA, C. Murray

The universe is a dusty place, as this NASA/ESA Hubble Space Telescope image featuring swirling clouds of gas and dust near the Tarantula Nebula reveals. Located in the Large Magellanic Cloud about 160,000 light-years away in the constellations Dorado and Mensa, the Tarantula Nebula is the most productive star-forming region in the nearby universe, home to the most massive stars known.

The nebula’s colorful gas clouds hold wispy tendrils and dark clumps of dust. This dust is different from ordinary household dust, which may include bits of soil, skin cells, hair, and even plastic. Cosmic dust is often comprised of carbon or of molecules called silicates, which contain silicon and oxygen. The data in this image was part of an observing program that aims to characterize the properties of cosmic dust in the Large Magellanic Cloud and other nearby galaxies.

Dust plays several important roles in the universe. Even though individual dust grains are incredibly tiny, far smaller than the width of a single human hair, dust grains in disks around young stars clump together to form larger grains and eventually planets. Dust also helps cool clouds of gas so that they can condense into new stars. Dust even plays a role in making new molecules in interstellar space, providing a venue for individual atoms to find each other and bond together in the vastness of space.

New observations have dramatically reduced the chances of asteroid 2024 YR4 hitting Earth in 2032, lowering the risk to minimal levels, but its extraordinarily close approach will offer astronomers the chance to examine it in detail

Nature, Published online: 21 February 2025; doi:10.1038/d41586-025-00552-y

Objects that could strike the planet will be spotted more regularly as new asteroid-hunting telescopes come online.

2025 Scott Lectures - Lecture 3 Title tbc

Abstract not available

• Speaker: Professor Mikhail Lukin, Harvard University
• Thursday 06 March 2025, 11:00-12:00
• Venue: Ray Dolby Auditorium, Ray Dolby Centre, Cavendish Laboratory, JJ Thomson Avenue, CB3 0US.
• Series: Scott Lectures; organiser: Leona Hope-Coles.

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