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A population of dust-enshrouded objects orbiting the Galactic black hole 期刊论文
NATURE, 2020, 577 (7790) : 337-+
作者:  Witze, Alexandra
收藏  |  浏览/下载:29/0  |  提交时间:2020/07/03

The central 0.1 parsecs of the Milky Way host a supermassive black hole identified with the position of the radio and infrared source Sagittarius A* (refs.(1,2)), a cluster of young, massive stars (the S stars3) and various gaseous features(4,5). Recently, two unusual objects have been found to be closely orbiting Sagittarius A*: the so-called G sources, G1 and G2. These objects are unresolved (having a size of the order of 100 astronomical units, except at periapse, where the tidal interaction with the black hole stretches them along the orbit) and they show both thermal dust emission and line emission from ionized gas(6-10). G1 and G2 have generated attention because they appear to be tidally interacting with the supermassive Galactic black hole, possibly enhancing its accretion activity. No broad consensus has yet been reached concerning their nature: the G objects show the characteristics of gas and dust clouds but display the dynamical properties of stellar-mass objects. Here we report observations of four additional G objects, all lying within 0.04 parsecs of the black hole and forming a class that is probably unique to this environment. The widely varying orbits derived for the six G objects demonstrate that they were commonly but separately formed.


  
Highly porous nature of a primitive asteroid revealed by thermal imaging 期刊论文
NATURE, 2020, 579 (7800) : 518-522
作者:  Quinn, Robert A.;  Melnik, Alexey, V;  Vrbanac, Alison;  Fu, Ting;  Patras, Kathryn A.;  Christy, Mitchell P.;  Bodai, Zsolt;  Belda-Ferre, Pedro;  Tripathi, Anupriya;  Chung, Lawton K.;  Downes, Michael;  Welch, Ryan D.;  Quinn, Melissa;  Humphrey, Greg;  Panitchpakdi, Morgan;  Weldon, Kelly C.;  Aksenov, Alexander;  da Silva, Ricardo;  Avila-Pacheco, Julian;  Clish, Clary;  Bae, Sena;  Mallick, Himel;  Franzosa, Eric A.;  Lloyd-Price, Jason;  Bussell, Robert;  Thron, Taren;  Nelson, Andrew T.;  Wang, Mingxun;  Leszczynski, Eric;  Vargas, Fernando;  Gauglitz, Julia M.;  Meehan, Michael J.;  Gentry, Emily;  Arthur, Timothy D.;  Komor, Alexis C.;  Poulsen, Orit;  Boland, Brigid S.;  Chang, John T.;  Sandborn, William J.;  Lim, Meerana;  Garg, Neha;  Lumeng, Julie C.;  Xavier, Ramnik J.;  Kazmierczak, Barbara, I;  Jain, Ruchi;  Egan, Marie;  Rhee, Kyung E.;  Ferguson, David;  Raffatellu, Manuela;  Vlamakis, Hera;  Haddad, Gabriel G.;  Siegel, Dionicio;  Huttenhower, Curtis;  Mazmanian, Sarkis K.;  Evans, Ronald M.;  Nizet, Victor;  Knight, Rob;  Dorrestein, Pieter C.
收藏  |  浏览/下载:97/0  |  提交时间:2020/05/13

Carbonaceous (C-type) asteroids(1) are relics of the early Solar System that have preserved primitive materials since their formation approximately 4.6 billion years ago. They are probably analogues of carbonaceous chondrites(2,3) and are essential for understanding planetary formation processes. However, their physical properties remain poorly known because carbonaceous chondrite meteoroids tend not to survive entry to Earth'  s atmosphere. Here we report on global one-rotation thermographic images of the C-type asteroid 162173 Ryugu, taken by the thermal infrared imager (TIR)(4) onboard the spacecraft Hayabusa2(5), indicating that the asteroid'  s boulders and their surroundings have similar temperatures, with a derived thermal inertia of about 300 J m(-2) s(-0.5) K-1 (300 tiu). Contrary to predictions that the surface consists of regolith and dense boulders, this low thermal inertia suggests that the boulders are more porous than typical carbonaceous chondrites(6) and that their surroundings are covered with porous fragments more than 10 centimetres in diameter. Close-up thermal images confirm the presence of such porous fragments and the flat diurnal temperature profiles suggest a strong surface roughness effect(7,8). We also observed in the close-up thermal images boulders that are colder during the day, with thermal inertia exceeding 600 tiu, corresponding to dense boulders similar to typical carbonaceous chondrites(6). These results constrain the formation history of Ryugu: the asteroid must be a rubble pile formed from impact fragments of a parent body with microporosity(9) of approximately 30 to 50 per cent that experienced a low degree of consolidation. The dense boulders might have originated from the consolidated innermost region or they may have an exogenic origin. This high-porosity asteroid may link cosmic fluffy dust to dense celestial bodies(10).


Thermal imaging data obtained from the spacecraft Hayabusa2 reveal that the carbonaceous asteroid 162173 Ryugu is an object of unusually high porosity.


  
Bias Correction of Airborne Thermal Infrared Observations Over Forests Using Melting Snow 期刊论文
WATER RESOURCES RESEARCH, 2019, 55 (12) : 11331-11343
作者:  Pestana, Steven;  Chickadel, C. Chris;  Harpold, Adrian;  Kostadinov, Tihomir S.;  Pai, Henry;  Tyler, Scott;  Webster, Clare;  Lundquist, Jessica D.
收藏  |  浏览/下载:21/0  |  提交时间:2020/02/16
snow  forest temperature  drone  thermal infrared  unmanned aircraft systems  calibration  
Improved Assessment of Atmospheric Water Vapor Content in the Himalayan Regions Around the Kullu Valley in India Using Landsat-8 Data 期刊论文
WATER RESOURCES RESEARCH, 2019, 55 (1) : 462-475
作者:  Varade, D.;  Dikshit, O.
收藏  |  浏览/下载:9/0  |  提交时间:2019/04/09
water vapor  orthographic correction  split window method  Landsat-8  thermal infrared  Himalaya  
Vertical Profiles of Ice Cloud Microphysical Properties and Their Impacts on Cloud Retrieval Using Thermal Infrared Measurements 期刊论文
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 2018, 123 (10) : 5301-5319
作者:  Khatri, Pradeep;  Iwabuchi, Hironobu;  Saito, Masanori
收藏  |  浏览/下载:16/0  |  提交时间:2019/04/09
ice cloud  thermal infrared  ICAS  CALIPSO  CloudSat  retrieval  
Exploring the Utility of IASI for Monitoring Volcanic SO2 Emissions 期刊论文
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 2018, 123 (10) : 5588-5606
作者:  Taylor, Isabelle A.;  Preston, James;  Carboni, Elisa;  Mather, Tamsin A.;  Grainger, Roy G.;  Theys, Nicolas;  Hidalgo, Silvana;  Kilbride, Brendan McCormick
收藏  |  浏览/下载:20/0  |  提交时间:2019/04/09
SO2  IASI  satellite observation  volcanic emissions  thermal infrared spectra  
Topographical and Local Time Dependence of Large Stationary Gravity Waves Observed at the Cloud Top of Venus 期刊论文
GEOPHYSICAL RESEARCH LETTERS, 2017, 44 (24)
作者:  Kouyama, T.;  Imamura, T.;  Taguchi, M.;  Fukuhara, T.;  Sato, T. M.;  Yamazaki, A.;  Futaguchi, M.;  Murakami, S.;  Hashimoto, G. L.;  Ueno, M.;  Iwagami, N.;  Takagi, S.;  Takagi, M.;  Ogohara, K.;  Kashimura, H.;  Horinouchi, T.;  Sato, N.;  Yamada, M.;  Yamamoto, Y.;  Ohtsuki, S.;  Sugiyama, K.;  Ando, H.;  Takamura, M.;  Yamada, T.;  Satoh, T.;  Nakamura, M.
收藏  |  浏览/下载:33/0  |  提交时间:2019/04/09
Venus  atmosphere  stationary waves  Akatsuki  thermal infrared  
A fast hybrid (3-D/1-D) model for thermal radiative transfer in cirrus via successive orders of scattering 期刊论文
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 2017, 122 (1)
作者:  Fauchez, Thomas;  Davis, Anthony B.;  Cornet, Celine;  Szczap, Frederic;  Platnick, Steven;  Dubuisson, Philippe;  Thieuleux, Francois
收藏  |  浏览/下载:11/0  |  提交时间:2019/04/09
cirrus  3-D radiative transfer  thermal infrared  scattering by ice crystals