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Astronomy and Astrophysics

The study of celestial objects and cosmic phenomena, including stellar evolution, galaxies, cosmology, exoplanets, gravitational waves, and observational astronomy techniques

30 papers

Papers

Science opportunities with solar sailing smallsats

This paper proposes the "Sundiver" concept, advocating for small, solar-sailing spacecraft to enable fast, low-cost exploration of the deep solar system, including missions to outer planets, asteroids, and interstellar space. It meticulously outlines numerous science opportunities across heliophysics, planetary science, and astrophysics. The authors emphasize that while some missions are feasible with current technology, the full realization of the "Sundiver" paradigm requires significant advancements in sail materials, power systems, and autonomous in-flight assembly.

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Astronomy and Astrophysics Oct 10, 08:55 PM

3I/ATLAS: In Search of the Witnesses to Its Voyage

This study investigates the past trajectory of interstellar object 3I/ATLAS, finding that none of the identified stellar encounters over the past 10 million years significantly perturbed its orbit or could account for its origin. While 3I/ATLAS's kinematics are consistent with a thin-disk population, the exact source of its ejection into interstellar space remains unknown. The analysis highlights the challenges in reconstructing long-term trajectories due to data incompleteness and sensitivity to Galactic models.

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Astronomy and Astrophysics Oct 06, 05:29 PM

Cohomogeneity-1 solutions in Einstein-Maxwell-dilaton gravity

This paper presents an effective method to reduce the complex field equations of Einstein-Maxwell-dilaton gravity in higher dimensions to a more manageable one-dimensional system. Using this simplified framework, the author successfully derives new generalized solutions, such as an interpolating solution between Reissner-Nordström and Bertotti-Robinson, and provides simpler derivations for known spacetimes, revealing an additional curvature singularity in the planar Anti-de Sitter naked singularity case.

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Astronomy and Astrophysics Oct 05, 02:41 PM

JWST's first view of the most vigorously star-forming cloud in the Galactic center Sagittarius B2

Using the James Webb Space Telescope (JWST), astronomers observed Sagittarius B2, the most active star-forming cloud in the Milky Way, and discovered a significantly higher number of previously hidden massive stars and ionized regions, indicating that the total star formation in this extreme environment has been severely underestimated. The observations also revealed a complex, multi-layered structure within the cloud, with different regions exhibiting distinct stages of stellar evolution.

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Astronomy and Astrophysics Sep 27, 07:13 PM

Effort.jl: a fast and differentiable emulator for the Effective Field Theory of the Large Scale Structure of the Universe

This paper introduces Effort.jl, a new software package designed to emulate the Effective Field Theory of Large-Scale Structure (EFTofLSS). Effort.jl boasts impressive speed and integrates with gradient-based sampling methods, allowing for rapid analysis of large cosmological datasets like BOSS and the PT-Challenge simulations.

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Astronomy and Astrophysics Sep 16, 06:45 PM

A remarkable Ruby: Absorption in dense gas, rather than evolved stars, drives the extreme Balmer break of a Little Red Dot at z = 3.5

This paper analyzes JWST observations of a distant galaxy called "The Cliff." The authors find that standard models of galaxy formation can't explain its unique light signature, particularly an extremely strong drop-off in brightness at a specific wavelength. They propose an alternative model: a supermassive black hole surrounded by dense gas, a "black hole star," which might better explain the observations.

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Astronomy and Astrophysics Sep 12, 04:50 PM

The Feasibility of a Spacecraft Flyby with the Third Interstellar Object 31/ATLAS from Earth or Mars

This paper explores the possibility of sending a spacecraft to the interstellar object 3I/ATLAS. Launching from Earth shortly after the comet's discovery would be very difficult due to the high energy requirements, but a launch from Mars might be feasible. A Mars-based spacecraft could potentially be redirected to fly by 3I/ATLAS, offering a unique scientific opportunity.

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Astronomy and Astrophysics Sep 09, 05:59 PM

The existence and distribution of photon spheres near spherically symmetric black holes: a geometric analysis

Using a geometric approach, this study proves that stable and unstable photon spheres near spherically symmetric black holes must alternate, with each type of sphere sandwiched between two spheres of the opposite type. This leads to a new proof that the difference between the number of stable and unstable photon spheres is always -1. The work is limited to idealized, non-rotating black holes.

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Astronomy and Astrophysics Sep 03, 05:46 PM

JWST detection of a carbon dioxide dominated gas coma surrounding interstellar object 3I/ATLAS

Observations of interstellar object 3I/ATLAS using the James Webb Space Telescope reveal a coma rich in carbon dioxide, with a CO 2 /H 2 O ratio much higher than typical Solar System comets. This might indicate a different formation environment for 3I/ATLAS, potentially in a CO 2 -rich region of its parent protoplanetary disk or in a low metallicity environment.

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Astronomy and Astrophysics Aug 26, 06:33 PM

GWTC-4.0: Updating the Gravitational-Wave Transient Catalog with Observations from the First Part of the Fourth LIGO-Virgo-KAGRA Observing Run

The LIGO-Virgo-KAGRA collaboration has more than doubled the size of its gravitational wave transient catalog, adding 128 new candidates from the first part of their fourth observing run. These new candidates are primarily from binary black holes and neutron star-black hole mergers, including some of the most massive black holes observed so far. Two new NSBH signals were also observed, one of which had its source properties analyzed for the first time in this catalog.

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Astronomy and Astrophysics Aug 26, 09:09 AM

DESI Dark Energy Time Evolution is Recovered by Cosmologically Coupled Black Holes

This study proposes that dark energy could be explained by cosmologically coupled black holes, which grow in mass in sync with the universe's expansion. They found that this model generally agrees with data from the Dark Energy Spectroscopic Instrument (DESI) on sound waves in the early universe, but there are differences at low redshifts. This theory could potentially explain the "missing baryon" problem and low neutrino mass estimates from DESI.

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Astronomy and Astrophysics Aug 24, 07:37 PM

Rieger, Schwabe, Suess-de Vries: The Sunny Beats of Resonance

This paper proposes that the gravitational pull of planets, particularly Venus, Earth, and Jupiter, influences solar activity cycles such as Rieger, Schwabe, and Suess-de Vries cycles. However, the study mainly relies on correlations and simplified models, without a clear causal link. The validity and significance of some of the claimed periodicities in solar activity are also subject to ongoing debate in the scientific community.

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Astronomy and Astrophysics Aug 21, 07:00 PM

Observation of an ultra-high-energy cosmic neutrino with KM3NeT

The KM3NeT neutrino telescope has detected an exceptionally high-energy muon neutrino, with an estimated energy exceeding 100 PeV. This is the highest energy neutrino observed to date, suggesting the existence of unknown or poorly understood cosmic accelerators or processes. Further data and more refined calibration of the detector are needed to confirm the observation and pinpoint the source.

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Astronomy and Astrophysics Aug 19, 12:28 PM

Arecibo Wow! I: An Astrophysical Explanation for the Wow! Signal

This paper suggests that the "Wow!" signal may have come from a brief brightening of a cold hydrogen cloud in our galaxy, potentially triggered by a magnetar flare, and amplified by a phenomenon called superradiance. This natural explanation challenges the extraterrestrial hypothesis but introduces a new possible source of false positives for SETI. The lack of a repeat signal remains the biggest hurdle to definitively confirming any explanation.

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Astronomy and Astrophysics Aug 15, 09:58 AM

Simultaneous visible spectrophotometry of interstellar object 3I/ATLAS with Seimei/TriCCS

Observations of the interstellar object 3I/ATLAS suggest a reddish surface similar to D- or Z-type asteroids in our solar system, although more data are needed to confirm this. The lightcurve data obtained over 2.3 hours likely show instrumental artifacts rather than true variations in brightness, leaving the object's rotation period uncertain. Comparisons with other observations highlight the challenges in consistently measuring these objects and the possibility of real surface changes.

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Astronomy and Astrophysics Aug 15, 09:58 AM

Worlds Next Door: A Candidate Giant Planet Imaged in the Habitable Zone of α Cen A. I. Observations, Orbital and Physical Properties, and Exozodi Upper Limits

Using JWST, researchers found a candidate giant exoplanet (S1) orbiting Alpha Centauri A. Subsequent observations did not detect S1, possibly due to its orbital motion. If confirmed as a planet, this would be the closest directly-imaged exoplanet found to date, and the detection methodology also yielded significantly improved upper limits on exozodiacal dust in the star system.

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Astronomy and Astrophysics Aug 09, 08:58 PM

Is the Interstellar Object 31/ATLAS Alien Technology?

The paper analyzes the trajectory and characteristics of interstellar object 3I/ATLAS, hypothesizing that it could be alien technology. However, the evidence presented is circumstantial and alternative explanations are possible. The analysis suggests 3I/ATLAS's close approaches to several planets and its perihelion on the opposite side of the Sun to Earth as potentially significant, but these could also be natural occurrences.

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Astronomy and Astrophysics Aug 09, 12:41 PM

Indication for a Compact Object Next to a LIGO–Virgo Binary Black Hole Merger

Analysis of gravitational wave data from GW190814 suggests the presence of a third compact object near the merging binary black holes, potentially influencing their orbital motion. The finding is based on observing a slight acceleration in the gravitational wave signal, but further research is needed to confirm this interpretation due to limitations in signal strength and potential for alternative explanations. If true, this discovery could have implications for our understanding of black hole formation in dense environments like active galactic nuclei.

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Astronomy and Astrophysics Aug 09, 09:17 AM

Hubble Space Telescope Observations of the Interstellar Interloper 31/ATLAS

Observations of interstellar interloper 3I/ATLAS using the Hubble Space Telescope reveal that the object is smaller than initially estimated, with a nucleus radius less than 2.8 km. The object is active and releasing dust at a rate of 6-60 kg/s, potentially driven by sublimation of ices. The coma morphology suggests anisotropic mass loss predominantly towards the Sun.

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Astronomy and Astrophysics Aug 08, 01:53 PM

Worlds Next Door: A Candidate Giant Planet Imaged in the Habitable Zone of α Cen A. I. Observations, Orbital and Physical Properties, and Exozodi Upper Limits

Using JWST, researchers observed Alpha Centauri A and found a candidate giant planet in the habitable zone, however it was only observed once and hasn't been seen since. The non-detection of exozodiacal dust around the star sets a new sensitivity record, showing that any dust there is at least 5-8 times fainter than the dust in our solar system. If confirmed, this planet would be the closest, coldest, and oldest imaged planet around a sun-like star.

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Astronomy and Astrophysics Aug 07, 01:37 PM

Gravitational Bounce from the Quantum Exclusion Principle

This paper proposes a model within standard general relativity where the universe originates from the collapse and bounce of a finite, closed region of matter. The bounce arises from a "ground state" characterized by constant energy density and negative degeneracy pressure, leading to an inflationary expansion phase and potentially explaining dark energy as a boundary effect of the finite universe.

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Astronomy and Astrophysics Jul 28, 07:10 PM

The role of the Lorentz force in sunspot equilibrium

This paper investigates the role of the Lorentz force in maintaining the equilibrium of sunspots, specifically focusing on the often-neglected azimuthal direction. Combining observations and 3D MHD simulations, the study finds that despite the complex magnetic field structure, both the umbra and penumbra of sunspots are very close to azimuthal magnetohydrostatic equilibrium, helping explain their longevity.

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Astronomy and Astrophysics Jul 18, 04:40 PM

The SunPy Project: Open Source Development and Status of the Version 1.0 Core Package

This paper describes the first stable release (version 1.0) of the SunPy core package, a community-developed, open-source Python library for solar physics data analysis. SunPy provides tools for data search and retrieval, visualization, coordinate transformations, and analysis, leveraging the broader scientific Python ecosystem to facilitate advanced solar research.

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Astronomy and Astrophysics Jul 14, 06:47 AM

Lunar impact crater identification and age estimation with Chang'E data by deep and transfer learning

This study used deep and transfer learning with Chang'E data to identify lunar impact craters, resulting in a database of 117,240 craters (more than 10x previous counts) and estimated ages for nearly 19,000 large craters. This method offers a robust and automated approach for lunar crater studies, surpassing previous methods in quantity and potentially accuracy, paving the way for improved lunar chronology and geologic understanding.

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Astronomy and Astrophysics Jul 14, 06:47 AM