Near-Earth Asteroids posed a threat to human civilization,making their monitoring crucial.As the demand for asteroid detection technology increased,precise detection of these celestial bodies became an urgent task to ...Near-Earth Asteroids posed a threat to human civilization,making their monitoring crucial.As the demand for asteroid detection technology increased,precise detection of these celestial bodies became an urgent task to understand their characteristics and assess potential impact risks.To improve asteroid detection accuracy and efficiency,we proposed an advanced image processing method and a deep learning network for automatic asteroid detection.Specifically,we aligned star clusters and overlaid images to exploit asteroid motion rates,transforming them into object-like trajectories and improving the signal-to-noise ratio.This approach created the Asteroid Trajectory Image Data set under various conditions.We modified CenterNet2 network to develop AstroCenterNet by integrating Multi-channel Histogram Truncation for feature enhancement,using the SimAM attention mechanism to expand contextual information and suppress noise,and refining Feature Pyramid Network to improve low-level feature detection.Our results demonstrated a detection accuracy of 98.4%,a recall of 97.6%,a mean Average Precision of 94.01%,a false alarm rate of 1.6%,and a processing speed of approximately 17.86 frames per second,indicating that our method achieves high precision and efficiency.展开更多
When a planet is ejected from its star-planet system due to dynamical interactions,its satellite may remain gravitationally bound to the planet.The Chinese Space Station Telescope(CSST)will be capable of detecting a l...When a planet is ejected from its star-planet system due to dynamical interactions,its satellite may remain gravitationally bound to the planet.The Chinese Space Station Telescope(CSST)will be capable of detecting a large number of low-mass free-floating planet events(FFPs)from a bulge microlensing survey.We assess the feasibility of detecting satellites(a.k.a.,exomoons)orbiting FFPs by simulating CSST light curves and calculating the detection efficiency as a function of satellite-to-planet mass ratios(q)and projected separations(s)in units of the Einstein radius.For a Neptune-class FFP in the Galactic disk with a Sun-like star as the microlensed source,CSST can detect Earth-mass satellites over a decade of separations(∼0.01-0.1 au)and has sensitivity down to Moon-mass satellites(q∼10^(−3))at s^(∼1).CSST also has some sensitivity to detect Moon-mass satellites at s∼2(∼0.02 au)orbiting an Earth-mass FFP in the disk.CSST has substantially reduced sensitivity for detecting satellites when the source star is an M dwarf,compared to a Sun-like source.We also calculate the satellite detection efficiency for the dedicated microlensing survey of the Roman Space Telescope(Roman),which demonstrates greater sensitivity than CSST,particularly for M-dwarf sources.Notably,some of the Neptune-Earth systems detectable by CSST and Roman may exhibit significant tidal heating.展开更多
The atomic and molecular compounds of cometary ices serve as valuable knowledge into the chemical and physical properties of the outer solar nebula, where comets are formed. From the cometary atmospheres, the atoms an...The atomic and molecular compounds of cometary ices serve as valuable knowledge into the chemical and physical properties of the outer solar nebula, where comets are formed. From the cometary atmospheres, the atoms and gas-phase molecules arise mainly in three ways:(i) the outgassing from the nucleus,(ii) the photochemical process, and(iii) the sublimation of icy grains from the nucleus. In this paper, we present the radio and millimeter wavelength observation results of Oort cloud non-periodic comet C/2022 E3(ZTF) using the Giant Metrewave Radio Telescope(GMRT) band L and the Atacama Large Millimeter/submillimeter Array(ALMA) band 6. We do not detect continuum emissions and an emission line of atomic hydrogen(H I) at rest frequency 1420 MHz from this comet using the GMRT. Based on ALMA observations, we detect the dust continuum emission and rotational emission lines of methanol(CH_(3)OH) from comet C/2022 E3(ZTF). From the dust continuum emission, the dust production(Afρ) activity of comet ZTF is 2280 ± 50 cm. Based on LTE spectral modeling, the column density and excitation temperature of CH_(3)OH toward C/2022 E3(ZTF) are(4.50 ± 0.25) × 10^(14)cm^(-2)and 70 ± 3 K respectively. The integrated emission maps show that CH_(3)OH was emitted from the coma region of the comet. The production rate of CH_(3)OH toward C/2022 E3(ZTF) is(7.32 ± 0.64) × 10^(26) molecules s^(-1). The fractional abundance of CH_(3)OH with respect to H2O in the coma of the comet is 1.52%. We also compare our derived abundance of CH_(3)OH with the existence modeled value, and we see the observed and modeled values are quite similar. We claim that CH_(3)OH is formed via the subsequential hydrogenation of formaldehyde(H2CO) on the grain surface of comet C/2022 E3(ZTF).展开更多
基金funded by the National Science and Technology Major Project(2022ZD0117401)the National Defense Science and Technology Innovation Special Zone Project Foundation of China(grant No.19-163-21-TS-001-067-01)support was provided by the Chinese Academy of Sciences(CAS)“Light of West China”Program(No.2020-XBQNXZ-016 and No.2022-XBQNXZ-016).
文摘Near-Earth Asteroids posed a threat to human civilization,making their monitoring crucial.As the demand for asteroid detection technology increased,precise detection of these celestial bodies became an urgent task to understand their characteristics and assess potential impact risks.To improve asteroid detection accuracy and efficiency,we proposed an advanced image processing method and a deep learning network for automatic asteroid detection.Specifically,we aligned star clusters and overlaid images to exploit asteroid motion rates,transforming them into object-like trajectories and improving the signal-to-noise ratio.This approach created the Asteroid Trajectory Image Data set under various conditions.We modified CenterNet2 network to develop AstroCenterNet by integrating Multi-channel Histogram Truncation for feature enhancement,using the SimAM attention mechanism to expand contextual information and suppress noise,and refining Feature Pyramid Network to improve low-level feature detection.Our results demonstrated a detection accuracy of 98.4%,a recall of 97.6%,a mean Average Precision of 94.01%,a false alarm rate of 1.6%,and a processing speed of approximately 17.86 frames per second,indicating that our method achieves high precision and efficiency.
基金supported by the National Natural Science Foundation of China(grant No.12133005)the China Manned Space Program with grant No.CMS-CSST-2025-A16.S.D.acknowledges the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘When a planet is ejected from its star-planet system due to dynamical interactions,its satellite may remain gravitationally bound to the planet.The Chinese Space Station Telescope(CSST)will be capable of detecting a large number of low-mass free-floating planet events(FFPs)from a bulge microlensing survey.We assess the feasibility of detecting satellites(a.k.a.,exomoons)orbiting FFPs by simulating CSST light curves and calculating the detection efficiency as a function of satellite-to-planet mass ratios(q)and projected separations(s)in units of the Einstein radius.For a Neptune-class FFP in the Galactic disk with a Sun-like star as the microlensed source,CSST can detect Earth-mass satellites over a decade of separations(∼0.01-0.1 au)and has sensitivity down to Moon-mass satellites(q∼10^(−3))at s^(∼1).CSST also has some sensitivity to detect Moon-mass satellites at s∼2(∼0.02 au)orbiting an Earth-mass FFP in the disk.CSST has substantially reduced sensitivity for detecting satellites when the source star is an M dwarf,compared to a Sun-like source.We also calculate the satellite detection efficiency for the dedicated microlensing survey of the Roman Space Telescope(Roman),which demonstrates greater sensitivity than CSST,particularly for M-dwarf sources.Notably,some of the Neptune-Earth systems detectable by CSST and Roman may exhibit significant tidal heating.
文摘The atomic and molecular compounds of cometary ices serve as valuable knowledge into the chemical and physical properties of the outer solar nebula, where comets are formed. From the cometary atmospheres, the atoms and gas-phase molecules arise mainly in three ways:(i) the outgassing from the nucleus,(ii) the photochemical process, and(iii) the sublimation of icy grains from the nucleus. In this paper, we present the radio and millimeter wavelength observation results of Oort cloud non-periodic comet C/2022 E3(ZTF) using the Giant Metrewave Radio Telescope(GMRT) band L and the Atacama Large Millimeter/submillimeter Array(ALMA) band 6. We do not detect continuum emissions and an emission line of atomic hydrogen(H I) at rest frequency 1420 MHz from this comet using the GMRT. Based on ALMA observations, we detect the dust continuum emission and rotational emission lines of methanol(CH_(3)OH) from comet C/2022 E3(ZTF). From the dust continuum emission, the dust production(Afρ) activity of comet ZTF is 2280 ± 50 cm. Based on LTE spectral modeling, the column density and excitation temperature of CH_(3)OH toward C/2022 E3(ZTF) are(4.50 ± 0.25) × 10^(14)cm^(-2)and 70 ± 3 K respectively. The integrated emission maps show that CH_(3)OH was emitted from the coma region of the comet. The production rate of CH_(3)OH toward C/2022 E3(ZTF) is(7.32 ± 0.64) × 10^(26) molecules s^(-1). The fractional abundance of CH_(3)OH with respect to H2O in the coma of the comet is 1.52%. We also compare our derived abundance of CH_(3)OH with the existence modeled value, and we see the observed and modeled values are quite similar. We claim that CH_(3)OH is formed via the subsequential hydrogenation of formaldehyde(H2CO) on the grain surface of comet C/2022 E3(ZTF).
