OrbitalHub

NASA dicit:

Globular clusters are extremely dense stellar systems, which host stars that are closely packed together. These systems are also typically very old — the globular cluster at the focus of this study, NGC 6397, is almost as old as the universe itself. This cluster resides 7,800 light-years away, making it one of the closest globular clusters to Earth. Due to its very dense nucleus, it is known as a core-collapsed cluster.

At first, astronomers thought the globular cluster hosted an intermediate-mass black hole. These are the long-sought “missing link” between supermassive black holes (many millions of times our Sun’s mass) that lie at the cores of galaxies, and stellar-mass black holes (a few times our Sun’s mass) that form following the collapse of a single massive star. Their mere existence is hotly debated. Only a few candidates have been identified to date.

The researchers used previous estimates of the stars’ tiny proper motions (their apparent motions on the sky), which allow for determining their true velocities within the cluster. These precise measurements for stars in the cluster’s core could only be made with Hubble over several years of observation. The Hubble data were added to well-calibrated proper motion measurements provided by the European Space Agency’s Gaia space observatory which are less precise than Hubble’s observations in the core.

Video credit: NASA’s Goddard Space Flight Center/Paul Morris: Lead Producer/Music: “Glass Ships” by Chris Constantinou [PRS] and Paul Frazer [PRS] via Killer Tracks [BMI] and Universal Production Music/Visual Credits: Artist’s Impression of the Black Hole Concentration in NGC 6397/Video credit: ESA/Hubble, N. Bartmann/Callout of the Black Hole Concentration in NGC 6397/Video credit: ESA/Hubble, N. Bartmann/Artist Rendition of Gaia Spacecraft/Image credit: ESA, C. Carreau

Wikipedia dicit:

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

NASA dicit:

The Crab Nebula has been studied by people since it first appeared in Earth’s sky in 1054 A.D. Modern telescopes have captured its enduring engine powered by a quickly spinning neutron star that formed when a massive star collapsed. The combination of rapid rotation and a strong magnetic field generates jets of matter and anti-matter flowing away from its poles, and winds outward from its equator. For the translation of these data into sound, which also pans left to right, each wavelength of light has been paired with a different family of instruments. X-rays from Chandra X-ray Observatory (blue and white) are brass, optical light data from Hubble Space Telescope (purple) are strings, and infrared data from Spitzer (pink) can be heard in the woodwinds. In each case, light received towards the top of the image is played as higher pitched notes and brighter light is played louder.

Video credit: NASA/CXC/SAO/K.Arcand, SYSTEM Sounds (M. Russo, A. Santaguida)

NASA dicit:

NASA’s Dawn spacecraft captured pictures in visible and infrared wavelengths, which were combined to create this false-color view of a region in 57-mile-wide (92-kilometer-wide) Occator Crater on the dwarf planet Ceres (in the main asteroid belt between Mars and Jupiter). Here, recently exposed brine, or salty liquids, in the center of the crater were pushed up from a deep reservoir below Ceres’ crust. In this view, they appear reddish.

Seen here is Cerealia Facula (“facula” means bright area), a 9-mile-wide (15-kilometer-wide) region with a composition dominated by salts. The central dome, Cerealia Tholus, is about 1.9 miles (3 kilometers) across at its base and 1,100 feet (340 meters) tall. The dome is inside a central depression about 3,000 feet (900 meters) deep.

Dawn’s mission is managed by NASA’s Jet Propulsion Laboratory, a division of Caltech, for the agency’s Science Mission Directorate in Washington. Dawn is a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. JPL is responsible for overall Dawn mission science. Northrop Grumman in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team.

Video credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

NASA dicit:

Scientists using NASA’s telescope on an airplane, the Stratospheric Observatory for Infrared Astronomy, discovered water on a sunlit surface of the Moon for the first time. SOFIA is a modified Boeing 747SP aircraft that allows astronomers to study the solar system and beyond in ways that are not possible with ground-based telescopes. Molecular water, H2O, was found in Clavius Crater, one of the largest craters visible from Earth in the Moon’s southern hemisphere. This discovery indicates that water may be distributed across the lunar surface, and not limited to cold, shadowed places.

Video credit: NASA’s Ames Research Center

Wikipedia dicit:

Dark matter is hypothesized to be a form of matter thought to account for approximately 85% of the matter in the universe and about a quarter of its total mass–energy density or about 2.241×10−27 kg/m3. Support for its presence is drawn from a variety of astrophysical observations, including gravitational effects that under current theories of gravity do not make sense, unless more matter is present than can be seen. For this reason, the hypothesis has been created that dark matter exists, is abundant in the universe, and has had a strong influence on its structure and evolution. The name is due to the fact that by all observations, should dark matter exist, it does not appear to interact with the electromagnetic field, which means it does not absorb, reflect or emit electromagnetic radiation, and is therefore difficult to detect.

Primary support for dark matter comes from calculations showing that many galaxies would fly apart, or that they would not have formed or would not move as they do, if they did not contain a large amount of unseen matter. Other lines of evidence include observations in gravitational lensing and in the cosmic microwave background, along with astronomical observations of the observable universe’s current structure, the formation and evolution of galaxies, mass location during galactic collisions, and the motion of galaxies within galaxy clusters. In the standard Lambda-CDM model of cosmology, the total mass–energy of the universe contains 5% ordinary matter and energy, 27% dark matter and 68% of a form of energy known as dark energy. Thus, dark matter constitutes 85% of total mass, while dark energy plus dark matter constitute 95% of total mass–energy content.

Because dark matter has not yet been observed directly, if it exists, it must barely interact with ordinary baryonic matter and radiation, except through gravity. Most dark matter is thought to be non-baryonic in nature; it may be composed of some as-yet undiscovered subatomic particles. The primary candidate for dark matter is some new kind of elementary particle that has not yet been discovered, in particular, weakly interacting massive particles (WIMPs). Many experiments to directly detect and study dark matter particles are being actively undertaken, but none have yet succeeded. Dark matter is classified as “cold”, “warm”, or “hot” according to its velocity (more precisely, its free streaming length). Current models favor a cold dark matter scenario, in which structures emerge by gradual accumulation of particles.

Video credit: NASA’s Goddard Space Flight Center/Paul Morris (USRA): Lead Producer/Cassandra Morris: Voice over Talent/Visualizations and Additional Footage: ESA/Hubble — Gravitational Lensing Animation/ESA/Hubble — Gravitational Lensing Simplified Visualization/R. Wesson/ESO — Very Large Telescope Footage