迷你月球 2024 PT$_5$ 的发现与表征

Establishing Earth's Minimoon Population through Characterization of Asteroid 2020 CD$_3$

We report on our detailed characterization of Earth's second known temporary natural satellite, or minimoon, asteroid 2020 CD3. An artificial origin can be ruled out based on its area-to-mass ratio and broadband photometry, which suggest that it is a silicate asteroid belonging to the S or V complex in asteroid taxonomy. The discovery of 2020 CD3 allows for the first time a comparison between known minimoons and theoretical models of their expected physical and dynamical properties. The estimated diameter of 1.2+0.4-0.2 m and geocentric capture approximately a decade after the first known mini…

Characterization of Temporarily-Captured Minimoon 2020 CD$_3$ by Keck Time-resolved Spectrophotometry

We present time-resolved visible spectrophotometry of minimoon 2020 CD$_3$, the second asteroid known to become temporarily captured by the Earth-Moon system's gravitational field. The spectrophotometry was taken with Keck I/LRIS between wavelengths 434 nm and 912 nm in $B$, $g$, $V$, $R$, $I$ and RG850 filters as it was leaving the Earth-Moon system on 2020 March 23 UTC. The spectrophotometry of 2020 CD$_3$ most closely resembles the spectra of V-type asteroids and some Lunar rock samples with a reddish slope of ~18$\%$/100 nm between 434 nm and 761 nm corresponding to colors of $g$-$r$ = 0.6…

微型月亮2024 PT$_5$在可见光与近红外波段的多历元光谱-光度表征

Multi-epoch spectro-photometric characterization of the minimoon 2024 PT$_5$ in the visible and near-infrared

本文通过晴明和凯克望远镜的多波段测光观测，确定微型月亮2024 PT$_5$处于翻滚状态、属于S型复合体小行星，并测得反照率约0.26，支持其月球溅射物起源。

Dynamical evolution of near-Earth asteroid 1991 VG

The discovery of 1991 VG on 1991 November 6 attracted an unprecedented amount of attention as it was the first near-Earth object (NEO) ever found on an Earth-like orbit. At that time, it was considered by some as the first representative of a new dynamical class of asteroids, while others argued that an artificial (terrestrial or extraterrestrial) origin was more likely. Over a quarter of a century later, this peculiar NEO has been recently recovered and the new data may help in confirming or ruling out early theories about its origin. Here, we use the latest data to perform an independent ass…

Detection of a Satellite of the Trojan Asteroid (3548) Eurybates -- A Lucy Mission Target

We describe the discovery of a satellite of the Trojan asteroid (3548) Eurybates in images obtained with the Hubble Space Telescope. The satellite was detected on three separate epochs, two in September 2018 and one in January 2020. The satellite has a brightness in all three epochs consistent with an effective diameter of d2 =1.2+/-0.4 km. The projected separation from Eurybates was s~1700-2300 km and varied in position, consistent with a large range of possible orbits. Eurybates is a target of the Lucy Discovery mission and the early detection of a satellite provides an opportunity for a sig…

The Phosphene Controversy: Is it Phosphene? Is there life on Venus?

On 14th September 2020, the Royal Astronomical Society made an official statement coupled with a webminar on the discovery of phosphine on Venus. Single-line millimetre-waveband spectral detections of phosphine (with a signal-to-noise ratio of $\approx$ 15$σ$) from the JCMT and ALMA telescopes indicated a phosphine abundance of 20 ppb (parts per billion), 1000 times more than that on the Earth. Phosphine is an important biomarker and immediate speculation in the media about indicators of life being found on Venus followed. This article presents an analysis of the study and the results on the o…