OrbitalHub

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

NASA dicit:

In 2017, NASA’s Hubble Space Telescope captured an image of a huge wing-shaped shadow cast by a fledgling star’s unseen, planet-forming disk. The young star, called HBC 672, is casting the shadow across a more distant cloud in a star-forming region—like a fly wandering into the beam of a flashlight shining on a wall.

Video credit: NASA’s Goddard Space Flight Center/Paul Morris (USRA): Producer / Editor/Visualization Credit: NASA, ESA, and A. James and G. Bacon (STScI)/Jason Steele [ ASCAP ]/Soundcast Music [ SESAC ] and Universal Production Music.

Wikipedia dicit:

K2-18b was identified as part of the Kepler space telescope program, one of over 1,200 exoplanets discovered during the “Second Light” K2 mission. The discovery of K2-18b was made in 2015, orbiting a red dwarf star (now known as K2-18) with a stellar spectral type of M2.8 about 124 light-years (38 pc) from Earth. The planet was detected through variations in the star’s light curve caused by the transit of the planet in front of the star as seen from Earth. The planet was designated “K2-18b” as it was the eighteenth planet discovered during the K2 mission. The predicted relatively low contrast between the planet and its host star would make it easier to observe K2-18b’s atmosphere in the future.

In 2017, data from the Spitzer Space Telescope confirmed that K2-18b orbits in the habitable zone around K2-18 with a 33-day period, short enough to allow for observations of multiple K2-18b orbital cycles and improving the statistical significance of the signal. This led to widespread interest in continued observations of K2-18b.

Later studies on K2-18b using the High Accuracy Radial Velocity Planet Searcher (HARPS) and the Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrographs (CARMENES) instruments also identified a likely second exoplanet, K2-18c, with an estimated mass of 5.62±0.84 M⊕ in a tighter, 9-day orbit, but this additional planet has not yet been confirmed, and may instead be due to stellar activity.

Video credit: NASA Goddard

Wikipedia dicit:

Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass one-thousandth that of the Sun, but two-and-a-half times that of all the other planets in the Solar System combined. Jupiter is one of the brightest objects visible to the naked eye in the night sky, and has been known to ancient civilizations since before recorded history. It is named after the Roman god Jupiter. When viewed from Earth, Jupiter can be bright enough for its reflected light to cast shadows, and is on average the third-brightest natural object in the night sky after the Moon and Venus.

Jupiter is primarily composed of hydrogen with a quarter of its mass being helium, though helium comprises only about a tenth of the number of molecules. It may also have a rocky core of heavier elements, but like the other giant planets, Jupiter lacks a well-defined solid surface. Because of its rapid rotation, the planet’s shape is that of an oblate spheroid (it has a slight but noticeable bulge around the equator). The outer atmosphere is visibly segregated into several bands at different latitudes, resulting in turbulence and storms along their interacting boundaries. A prominent result is the Great Red Spot, a giant storm that is known to have existed since at least the 17th century when it was first seen by telescope. Surrounding Jupiter is a faint planetary ring system and a powerful magnetosphere. Jupiter has 79 known moons, including the four large Galilean moons discovered by Galileo Galilei in 1610. Ganymede, the largest of these, has a diameter greater than that of the planet Mercury.

Video credit: NASA Goddard

Wikipedia dicit:

2I/Borisov, originally designated C/2019 Q4 (Borisov), is the first observed interstellar comet and the second observed interstellar interloper after ʻOumuamua. 2I/Borisov has a heliocentric orbital eccentricity of 3.36 and is not bound to the Sun. The comet passed through the ecliptic of the Solar System at the end of October 2019, and made its closest approach to the Sun at just over 2 AU on 8 December 2019. In November 2019, astronomers from Yale University said that the comet (including coma and tail), was 14 times the size of Earth, and stated, “It’s humbling to realize how small Earth is next to this visitor from another solar system.” In the middle of March, 2020, the comet was observed to fragment; and later, in April, even more evidence of fragmentation was reported.

Video credit: NASA

NASA dicit:

This Hubble time-lapse movie shows the orbits of some of Saturn’s icy moons as they circle the planet over an 18-hour period. The video is composed of 33 Hubble snapshots of the planet, taken June 19 to 20, 2019, by the Wide Field Camera 3.

Saturn’s signature rings are still as stunning as ever. The image reveals that the ring system is tilted toward Earth, giving viewers a magnificent look at the bright, icy structure. Hubble resolves numerous ringlets and the fainter inner rings.

This image reveals an unprecedented clarity only seen previously in snapshots taken by NASA spacecraft visiting the distant planet. Astronomers will continue their yearly monitoring of the planet to track shifting weather patterns and identify other changes. The second in the yearly series, this image is part of the Outer Planets Atmospheres Legacy (OPAL) project. OPAL is helping scientists understand the atmospheric dynamics and evolution of our solar system’s gas giant planets.

Video Credit: NASA