Globally, 2020 was the hottest year on record, effectively tying 2016, the previous record. Overall, Earth’s average temperature has risen more than 2 degrees Fahrenheit since the 1880s. Temperatures are increasing due to human activities, specifically emissions of greenhouse gases, like carbon dioxide and methane.
Video credit: NASA’s Goddard Space Flight Center/Scientific Visualization Studio/Kathryn Mersmann (USRA): Lead Producer/Katie Jepson (USRA): Lead Producer/Jessica Merzdorf (Telophase): Lead Writer/Sofie L. Bates (Intern): Lead Writer/Peter H. Jacobs (NASA/GSFC): Public Affairs Officer/Gavin A. Schmidt (NASA/GSFC GISS): Lead Scientist/Lesley Ott (NASA/GSFC): Scientist/Lori Perkins (NASA/GSFC): Lead Visualizer/Trent L. Schindler (USRA): Visualizer/Jefferson Beck (USRA): Producer/Kathleen Gaeta (GSFC Interns): Producer/Jacob Richmond (NASA/GSFC): Public Affairs Officer
A brown dwarf is a type of substellar object that has a mass between the most massive gas giant planets and the least massive stars, approximately 13 to 80 times that of Jupiter (MJ).
Unlike main sequence stars, brown dwarfs do not acquire enough mass to trigger sustained nuclear fusion of ordinary hydrogen (1H) into helium in their cores. For this reason brown dwarfs are sometimes referred to as failed stars. They are, however, thought to fuse deuterium (2H), and to fuse lithium (7Li) if their mass is > 65 MJ. The minimum mass required to trigger sustained hydrogen-burning forms the upper limit of the definition currently used by the International Astronomical Union, while the deuterium-burning minimum mass of ~13 MJ forms the lower limit of the class, below which lie the planets.
It is also debated whether brown dwarfs would be better defined by their formation process rather than by theoretical mass limits based on nuclear fusion reactions. Under this interpretation brown dwarfs are those objects that represent the lowest-mass products of the star formation process, while planets are objects formed in an accretion disk surrounding a star. The coolest free-floating objects discovered such as WISE 0855, as well as the lowest-mass young objects known like PSO J318.5−22, are thought to have masses below 13 MJ, and as a result are sometimes referred to as planetary mass objects due to the ambiguity of whether they should be regarded as rogue planets or brown dwarfs. There are planetary mass objects known to orbit brown dwarfs, such as 2M1207b, MOA-2007-BLG-192Lb, and 2MASS J044144b.
Astronomers classify self-luminous objects by spectral class, a distinction intimately tied to the surface temperature, and brown dwarfs occupy types M, L, T, and Y. As brown dwarfs do not undergo stable hydrogen fusion they cool down over time, progressively passing through later spectral types as they age.
Video credit: NASA’s Goddard Space Flight Center/Scott Wiessinger (USRA): Animator/Scott Wiessinger (USRA): Producer/Ashley Balzer (ADNET): Science Writer/Claire Andreoli (NASA/GSFC): Public Affairs Officer
The Graphite-Epoxy Motor (GEM) is a series of solid rocket boosters fueled by HTPB and produced by Northrop Grumman Innovation Systems with a carbon-fiber-reinforced polymer casing. GEM series boosters were previously used on the Delta II, Delta III, and Delta IV. They will fly on the Atlas V and Vulcan.
The GEM-63XL is about 5 feet longer than the regular GEM-63 and will be used on the Vulcan launch vehicle starting in 2021. GEM-63XL offers higher performance at almost half the cost of the AJ-60A boosters currently being used on the Atlas V.
Sending the first Artemis mission to the Moon in preparation for human missions, landing a new rover on Mars, and launching the James Webb Space Telescope into space, expanding our ability to see deep into the universe, are just a few of the things NASA has planned for 2021.
On December 9, 2020, Starship serial number 8 (SN8) completed a high-altitude flight test as it successfully ascended, transitioned propellant, and demonstrated a first-of-its-kind controlled aerodynamic descent and landing flip maneuver – which will enable landing where prepared surfaces or runways do not exist, including the Moon, Mars, and beyond.
The Exploration Upper Stage (EUS) is being developed as a large second stage for Block 1B of the Space Launch System (SLS), succeeding Block 1’s Interim Cryogenic Propulsion Stage. It will be powered by four RL10-C3 engines burning liquid oxygen and liquid hydrogen to produce a total of 440 kN (99,000 lbf) thrust. As of February 2015, the SLS Block 1B will provide thrust of 105 t (103 long tons; 116 short tons). The EUS is expected to first fly on Artemis IV in 2025.
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