2019
November
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Saturn is the new King of Moons – and you can help name the moons just discovered!

The fact that a planet – like the Earth – has only one single companion, is rather unusual in our Solar System. With 79 moons, the giant planet Jupiter previously had the most moons. Now, it’s been surpassed by Saturn, which changed from having 62 to 82 moons in one fell swoop. The new moons around the ringed planet were discovered using the Subaru telescope on Mauna Kea in Hawaii.

Each of the newcomers has a diameter of about 5 km (3 miles). Seventeen of the twenty are orbiting Saturn in the wrong direction, in what is called a retrograde orbit, that is, in the direction opposite the rotation of the planet. The other three complete their circuit around Saturn the proper way, that is, they have prograde orbits. The fact that the moons were only just discovered is due not only to their small sizes, but also to their wide orbits. Only two of the prograde moons are relatively close to Saturn and need about two years to complete one orbit (the Earth’s moon takes one month). The other 18, in contrast, need more than three Earth years to complete their orbits.

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A planet that shouldn’t exist

GJ 3512 is a red dwarf. The star is about 31 light-years from us and has only 12% the mass of the Sun. But as far as the size of its companions go, GJ 3512 doesn’t hold back. As a German and Spanish research team has discovered, it has a gas giant with a mass of almost half our Jupiter. “Such stars should actually only have Earth-sized planets or at most super-Earths with slightly more mass,” says Professor Christoph Mordasini of the Physics Institute at the University of Bern, discussing plausible scenarios for the formation of the large exoplanet with his team. “In contrast, GJ 3512b is a giant planet with a mass approximately half as large as that of Jupiter, and thus at least one order of magnitude more massive than the planets predicted by theoretical models for such small stars.”

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Our second interstellar visitor has a name: 2I/Borisov

Were we being too loud, or did they just want to see Earth before it’s too late? Our Solar System is apparently becoming a popular destination point with extrasolar tourists. All jokes aside: After ‚Oumuamua at the end of 2017, astronomers have apparently just photographed our second interstellar object, which is currently moving toward the Sun.

The object was first discovered on August 30th. That night, amateur astronomer, Gennadi Borisov, found a comet-like object (initially called C/2019 Q4) in the skies over Crimea using his self-built 0.65-m telescope. At that time, it featured a coma and has since also developed a short tail. One week later, observatories all across the world had confirmed the discovery. The comet is moving on a hyperbolic trajectory at 150,000 km/h toward the Sun from an angle of 40 degrees to the ecliptic. Thus, after ‚Oumuamua (which is now considered an asteroid), it is the second interstellar object, and the first interstellar comet, seen in our system.

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New NASA simulations: what it’s like around a black hole

A black hole grows by being fed from a so-called accretion disk that supplies it with fresh matter. This disk is made up of plasma, ionized gas that orbits in continuous spirals around the black hole at high speeds. This plasma is constantly heated by internal collisions.

To an observer, however, an accretion disk won’t look like a classic disk (like, for example, Saturn’s rings). This is because a black hole generates such an unbelievably large force of gravity that radiation from the rear part of the disk becomes distorted as it moves toward the observer. Now, researchers at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, have reenacted this in impressive, mesmerizing computer simulations.

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Exo-Io: volcanic exomoon in orbit around WASP-49 b?

WASP-49 is a yellow dwarf star, somewhat smaller than the Sun and, in the grand scheme of the universe, just as unimportant as our own home star, so that up to now it hasn’t even been given a proper name. Astronomers also know it as “2MASS J06042146-1657550” or “TYC 5936-2086-1.” The fact that it also has the relatively short and catchy name of WASP-49 is thanks to the “Wide Angle Search for Planets”: WASP is an international cooperation that operates two autonomous telescopes. In 2011, researchers analyzing data from these telescopes discovered a planet orbiting this star, 550 light-years from Earth in the constellation of Lepus (the hare).

WASP-49 b is somewhat larger than our Jupiter. It is, however, what is called a “hot Jupiter.” WASP-49 b orbits its host star once every three days at a distance of 0.037 astronomical units (Earth is 30 times farther away from the Sun). It is so close to its star that it must be extremely hot. Researchers now think there is a moon in this rather inhospitable area. This exomoon – a moon outside of our own Solar System – would be an extreme version of Jupiter’s moon Io, thus, an exo-Io.

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Water vapor in the atmosphere of an inhabitable rocky planet

There’s no shortage of water in the universe. Water molecules have even been found in the cold interstellar medium. After hydrogen, water is the second most abundant substance in the atmosphere of hot gas planets. Neptune, Uranus, and their siblings in space are not called ice giants for no reason – they also contain a large amount of water ice.

On rocky planets, water could be a sign of good conditions for life. This, however, would also depend on where the water is located. Researchers already think that some planets have large quantities of water due to their densities. But a deep ocean extending across an entire celestial body wouldn’t be very suitable for life as we know it (and that’s the only form of life that we can talk about with some certainty).

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