A cross-section of a 3D simulation replicating a scenario for the impact that formed the Moon, showing a roughly Mars-mass impactor grazing an Earth-like target at a 45-degree angle. The simulation uses over 100 million particles, colored by their internal energy, related to their temperature.
This is one of more than 300 simulations that scientists at Durham University in the United Kingdom, alongside researchers at NASA’s Ames Research Center in California’s Silicon Valley, ran to develop a way to predict how much atmosphere is lost from a wide range of collisions between rocky objects, presented in a new study.
An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917, but was not recognized as such. The first confirmation of detection occurred in 1992. This was followed by the confirmation of a different planet, originally detected in 1988. As of 1 April 2021, there are 4,704 confirmed exoplanets in 3,478 systems, with 770 systems having more than one planet.
There are many methods of detecting exoplanets. Transit photometry and Doppler spectroscopy have found the most, but these methods suffer from a clear observational bias favoring the detection of planets near the star; thus, 85% of the exoplanets detected are inside the tidal locking zone. In several cases, multiple planets have been observed around a star. About 1 in 5 Sun-like stars have an “Earth-sized” planet in the habitable zone. Assuming there are 200 billion stars in the Milky Way, it can be hypothesized that there are 11 billion potentially habitable Earth-sized planets in the Milky Way, rising to 40 billion if planets orbiting the numerous red dwarfs are included.
The least massive planet known is Draugr (also known as PSR B1257+12 A or PSR B1257+12 b), which is about twice the mass of the Moon. The most massive planet listed on the NASA Exoplanet Archive is HR 2562 b, about 30 times the mass of Jupiter, although according to some definitions of a planet (based on the nuclear fusion of deuterium), it is too massive to be a planet and may be a brown dwarf instead. Known orbital times for exoplanets vary from a few hours (for those closest to their star) to thousands of years. Some exoplanets are so far away from the star that it is difficult to tell whether they are gravitationally bound to it. Almost all of the planets detected so far are within the Milky Way. There is evidence that extragalactic planets, exoplanets farther away in galaxies beyond the local Milky Way galaxy, may exist. The nearest exoplanets are located 4.2 light-years (1.3 parsecs) from Earth and orbit Proxima Centauri, the closest star to the Sun.
Juno is a NASA space probe orbiting the planet Jupiter. It was built by Lockheed Martin and is operated by NASA’s Jet Propulsion Laboratory. The spacecraft was launched from Cape Canaveral Air Force Station on 5 August 2011 UTC, as part of the New Frontiers program. Juno entered a polar orbit of Jupiter on 5 July 2016 UTC, to begin a scientific investigation of the planet. After completing its mission, Juno will be intentionally deorbited into Jupiter’s atmosphere.
Juno’s mission is to measure Jupiter’s composition, gravitational field, magnetic field, and polar magnetosphere. It will also search for clues about how the planet formed, including whether it has a rocky core, the amount of water present within the deep atmosphere, mass distribution, and its deep winds, which can reach speeds up to 620 km/h (390 mph).
Juno is the second spacecraft to orbit Jupiter, after the nuclear powered Galileo orbiter, which orbited from 1995 to 2003. Unlike all earlier spacecraft sent to the outer planets, Juno is powered by solar arrays, commonly used by satellites orbiting Earth and working in the inner Solar System, whereas radioisotope thermoelectric generators are commonly used for missions to the outer Solar System and beyond. For Juno, however, the three largest solar array wings ever deployed on a planetary probe play an integral role in stabilizing the spacecraft as well as generating power.
Video credit: NASA/JPL-Caltech/SwRI/UVS/ULiège/Bonfond
NASA’s Juno mission to Jupiter has made an unexpected discovery about a different planet – Mars. Juno scientists discovered that Martian dust may be the source of a sky phenomenon known as the zodiacal light.
Look up to the night sky just before dawn, or after dusk, and you might see a faint column of light extending up from the horizon. That glow is the zodiacal light, or sunlight reflected toward Earth by a cloud of tiny dust particles orbiting the Sun.
Astronomers have long thought that the dust is brought into the inner solar system by asteroids and comets. But now, a team of Juno scientists argues that the planet Mars may be the source. The discovery resulted from dust particles slamming into the Juno spacecraft during its journey from Earth to Jupiter. Juno’s expansive solar panels unintentionally became the biggest and most sensitive dust detector ever built. Impacts on the solar panels provided important clues to the origin and orbital evolution of the dust, resolving some of the mysterious variations observed in the zodiacal light.
Video credit: NASA’s Goddard Space Flight Center/Dan Gallagher (USRA): Lead Producer/Michael Lentz (USRA): Lead Animator/Kel Elkins (USRA):Lead Data Visualizer/Lonnie Shekhtman (ADNET): Writer/Rani Gran (NASA/GSFC): Public Affairs Officer/John Connerney (NASA/GSFC): Scientist/David Agle (JPL): Support/Aaron E. Lepsch (ADNET): Technical Support/Original musical score by Vangelis, used with permission.
As a planet moves around its host star, it exerts a tiny gravitational tug that shifts the star’s position a bit. This can pull the distant star closer and farther from a perfect alignment. Since the nearer star acts as a natural lens, it’s like the distant star’s light will be pulled slightly in and out of focus by the orbiting planet. By picking out little shudders in the starlight, astronomers will be able to infer the presence of planets.
Xallarap is parallax spelled backward. Parallax relies on motion of the observer – Earth moving around the Sun – to produce a change in the alignment between the distant source star, the closer lens star and the observer. Xallarap works the opposite way, modifying the alignment due to the motion of the source.
While microlensing is generally best suited to finding worlds farther from their star than Venus is from the Sun, the xallarap effect works best with very massive planets in small orbits, since they make their host star move the most. Revealing more distant planets will also allow us to probe a different population of worlds.
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
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