Geoff Marcy

We report on three optically bright, ∼16th mag, point sources within 10 arcsec of each other that vanished within 1 h, based on two consecutive exposures at Palomar Observatory on 1952 July 19 (POSS I Red and Blue). The three point sources have continued to be absent in telescope exposures during 71 yr with detection thresholds of ∼21st mag. We obtained two deep exposures with the 10.4-m Gran Telescopio Canarias on 2023 April 25 and 27 in r and g band, both reaching magnitude 25.5 (3σ). The three point sources are still absent, implying they have dimmed by more than 10 mag within an hour back in 1952. When bright in 1952, the most isolated transient source has a profile nearly the same as comparison stars, implying the sources are subarcsec in angular size and they exhibit no elongation due to movement. This triple transient has observed properties similar to other cases where groups of …

Improving our understanding of planetary system architectures, and especially the relationship between Earth-like planets and giant planets, is a major goal of the US astronomical community. A long-term RV study of stars that host small, transiting planets discovered by the NASA Kepler mission is uniquely suited to measure the occurrence of giant planets in a homogeneous sample of stars that are known to contain small planets. We present the results of the Kepler Giant Planet Survey, in which we measured 3,241 RVs of 56 Kepler planet-hosting stars over the past 12 years using Keck-HIRES. Our sample was giant-blind, meaning we had no prior knowledge of which systems would contain giant planets. We announce 17 non-transiting companions, updated masses and densities of 28 transiting planets, and preliminary results about the relationship between small, transiting planets and their massive companions.

Despite the importance of Jupiter and Saturn to Earth's formation and habitability, there has not yet been a comprehensive observational study of how giant exoplanets correlate with the architectural properties of close-in, sub-Neptune-sized exoplanets. This is largely because transit surveys are particularly insensitive to planets at orbital separations≳ 1 au, and so their census of Jupiter-like planets is incomplete, inhibiting our study of the relationship between Jupiter-like planets and the small planets that do transit. To investigate the relationship between close-in, small and distant, giant planets, we conducted the Kepler Giant Planet Survey (KGPS). Using the WM Keck Observatory High Resolution Echelle Spectrometer, we spent over a decade collecting 2844 radial velocities (RVs; 2167 of which are presented here for the first time) of 63 Sunlike stars that host 157 transiting planets. We had no prior knowledge of which …

Astronomers occasionally detect an object having unexpected shape, unexplainable photometry, or unprecedented spectra that are inconsistent with our contemporary knowledge of the universe. Upon careful assessment, many of these anomalies are discarded as mere noise, contamination, or faulty analysis. But some anomalies survive scrutiny to yield new astronomical objects and physical processes. Examples of validated anomalies include quasars, pulsars, and periodic Doppler shifts of Sun-like stars caused by the gravitational pull of orbiting planets. Other anomalies persist as mysteries, including Fast Radio Bursts, dark energy, 'Oumuamua as an alien spaceship, and simultaneously vanishing stars. Advanced technological life may present astronomers with anomalies that require carefully designed observations from multiple vantage points simultaneously and with real-time spectroscopy.

The Galactic plane was searched for transient, monochromatic light at optical and near-IR wavelengths to detect pulses shorter than 1 s. An objective-prism Schmidt telescope of 0.28-m aperture and a CMOS camera were used to observe 973 square deg, with 8864 exposures of 1-s each, within a strip 2.1 deg wide along the Galactic plane, from Galactic longitude −4 deg to +248 deg. All exposures were analysed for transient, monochromatic sources using a ‘difference image’ algorithm that yielded 11 candidate sources. All 11 sources were found to be associated with either astrophysical emission-line objects or aircraft with subsecond blinking lights. Our survey ‘rediscovered’ many Wolf–Rayet stars, M dwarf flare stars, and planetary nebulae. It also identified an aircraft, of unknown type, that apparently had a nearly monochromatic lamp and a xenon lamp. This survey would have revealed optical and near-IR …

A search was conducted for laser signals, both sub-second pulses and continuous emission, from the regions of the sky opposite Proxima and Alpha Centauri. These regions are located at the foci of the gravitational lensing caused by the Sun, ideal for amplifying transmissions between our Solar system and those two nearest stellar neighbours. The search was conducted using two objective prism telescopes operating with exposure times of 0.25 s, enabling detection of sub-second laser pulses coming from the solar gravitational foci. During 6 months in 2020 and 2021, 88 000 exposures for Proxima Cen and 47 000 exposures for Alpha Cen were obtained. No evidence was detected of light pulses or continuous laser emission in the wavelength range of 380–950 nm. We would have detected a laser having a power of just 100 W, for a benchmark 1-m laser launcher that was diffraction-limited and located at …

The Vanishing & Appearing Sources during a Century of Observations (VASCO) project investigates astronomical surveys spanning a time interval of 70 years, searching for unusual and exotic transients. We present herein the VASCO Citizen Science Project, which can identify unusual candidates driven by three different approaches: hypothesis, exploratory, and machine learning, which is particularly useful for SETI searches. To address the big data challenge, VASCO combines three methods: the Virtual Observatory, user-aided machine learning, and visual inspection through citizen science. Here we demonstrate the citizen science project and its improved candidate selection process, and we give a progress report. We also present the VASCO citizen science network led by amateur astronomy associations mainly located in Algeria, Cameroon, and Nigeria. At the moment of writing, the citizen science project has carefully examined 15,593 candidate image pairs in the data (ca. 10% of the candidates), and has so far identified 798 objects classified as “vanished”. The most interesting candidates will be followed up with optical and infrared imaging, together with the observations by the most potent radio telescopes.

A search for laser light from the directions of Alpha Centauri A and B was performed by examining 15 362 optical, high-resolution spectra obtained between 2004 and 2018. None of the spectra exhibit laser emission lines. The threshold was 10 per cent of the continuum intensity of the spectra of both stars at all wavelengths between 3850 and 6900 Å. This search would have revealed optical laser light from the directions of Alpha Cen B if the laser had a power of at least 1.4–5.4 MW (depending on wavelength) and was positioned within the 1 arcsec field of view (projecting to 1.3 au), for a benchmark 10-m laser launcher. For Alpha Cen A, the laser power must be three times greater for detection. Lasers of smaller aperture would also have been detected but would require more power. Considering all optical surveys, a growing desert is emerging in the search for extraterrestrial technology.