OrbitalHub

NASA dixit:

“When exoplanet scientists first spotted patterns in disks of dust and gas around young stars, they thought newly formed planets might be the cause. But a recent NASA study cautions that there may be another explanation: one that doesn’t involve planets at all. An alternative explanation suggests the dust and gas in the disk can form the patterns themselves when they interact with starlight.

When high-energy UV starlight hits dust grains, it strips away electrons. Those electrons collide with and heat nearby gas. As the gas warms, its pressure increases and it traps more dust, which in turn heats more gas. The resulting cycle, called the photoelectric instability (PeI), can work in tandem with other forces to create some of the features astronomers have previously associated with planets in debris disks.

A 2013 study suggested PeI could explain the narrow rings seen in some disks. The model also predicted that some disks would have arcs, or incomplete rings, which weren’t directly observed in a disk until 2016. The new simulation includes an additional new factor: radiation pressure, a force caused by starlight striking dust grains. Light exerts a minute physical force on everything it encounters. This radiation pressure propels solar sails and helps direct comet tails so they always point away from the Sun. The same force can push dust into highly eccentric orbits, and even blow some of the smaller grains out of the disk entirely. The new research modeled how radiation pressure and PeI work together to affect the movement of dust and gas, and also found that the two forces manifest different patterns depending on the physical properties of the dust and gas.”

Music credit: “Hyperborea” from Killer Tracks

Video credit: NASA’s Goddard Space Flight Center/Scott Wiessenger

NASA dixit:

“Observations by NASA’s Swift spacecraft, now renamed the Neil Gehrels Swift Observatory after the mission’s late principal investigator, have captured an unprecedented change in the rotation of a comet. Images taken in May 2017 reveal that comet 41P/Tuttle-Giacobini-Kresak — 41P for short — was spinning three times slower than it was in March, when it was observed by the Discovery Channel Telescope at Lowell Observatory in Arizona. The abrupt slowdown is the most dramatic change in a comet’s rotation ever seen.

Comet 41P orbits the Sun every 5.4 years. As a comet nears the Sun, increased heating causes its surface ice to change directly to a gas, producing jets that launch dust particles and icy grains into space. This material forms an extended atmosphere, called a coma.

Ground-based observations established the 41P’s initial rotational period at about 20 hours in early March 2017 and detected its slowdown later the same month. The comet passed 13.2 million miles (21.2 million km) from Earth on April 1, and eight days later made its closest approach to the Sun. Swift’s Ultraviolet/Optical Telescope imaged the comet from May 7 to 9, revealing brightness variations associated with material recently ejected into the coma. These slow changes indicated 41P’s rotation period had more than doubled, to between 46 and 60 hours.

UVOT-based estimates of 41P’s water production, coupled with the body’s small size, suggest that more than half of its surface area contains sunlight-activated jets. That’s a far greater fraction of active real estate than on most comets, which typically support jets over only about 3 percent of their surfaces. Astronomers suspect these active areas are favorably oriented to produce torques that slowed 41P’s spin.

Such a slow spin could make the comet’s rotation unstable, allowing it to begin tumbling with no fixed rotational axis. This would produce a dramatic change in the comet’s seasonal heating and may result in future outbursts of activity.”

Music credit: “Valley of Crystals” from Killer Tracks

Video credit: NASA’s Goddard Space Flight Center/Scott Wiessinger

NASA dixit:

“Astronomers studying the star RZ Piscium have found evidence suggesting its strange, unpredictable dimming episodes may be caused by vast orbiting clouds of gas and dust, the remains of one or more destroyed planets.

Young stars are often prodigious X-ray sources. Observations using the European Space Agency’s XMM-Newton satellite, show that RZ Piscium is, too. Its total X-ray output is roughly 1,000 times greater than our Sun’s. Ground-based observations show the star’s surface temperature to be about 9,600 degrees Fahrenheit (5,330 degrees Celsius), only slightly cooler than the Sun’s. They also show RZ Piscium is enriched in the tell-tale element lithium, which is slowly destroyed by nuclear reactions inside stars and serves as a clock indicating the elapsed time since a star’s birth.

Ground-based telescopes also reveal large amounts of dust and hydrogen-rich gas in the system, suggesting that large blobs of this material are orbiting the star and causing the brightness dips.

The best explanation that accounts for all of the available data, say the researchers, is that the star is encircled by debris representing the aftermath of a disaster of planetary proportions. It’s possible the star’s tides may be stripping material from a close substellar companion or giant planet, producing intermittent streams of gas and dust, or that the companion is already completely dissolved. Another possibility is that one or more massive gas-rich planets in the system underwent a catastrophic collision in the astronomically recent past.”

Music: “Frozen Wonder” from Killer Tracks

Video credit: NASA’s Goddard Space Flight Center/CI Lab

NASA dixit:

“These 4K visualizations show the Moon’s phase and libration at hourly intervals throughout 2018, as viewed from the Northern and Southern Hemispheres. Each frame represents one hour. In addition, this visualization shows the moon’s orbit position, sub-Earth and subsolar points, distance from the Earth at true scale, and labels of craters near the terminator.”

Ernie Wright (USRA): Lead Visualizer

John Keller (NASA/GSFC): Scientist

Noah Petro (NASA/GSFC): Scientist

Music Credits: Killer Tracks: “Illuminating” – Kelly McCollough; “Touching Clouds” – Kelly McCollough; “Euphoric Glow” – Andrew Skeet, Andrew Britton, David Goldsmith; “Just Beyond” – Kelly McCollough.

Video credit: NASA’s Goddard Space Flight Center/David Ladd (USRA)

NASA dixit:

“Our solar system now is tied for most number of planets around a single star, with the recent discovery of an eighth planet circling Kepler-90, a Sun-like star 2,545 light years from Earth. The planet was discovered in data from NASA’s Kepler space telescope.

The newly-discovered Kepler-90i — a sizzling hot, rocky planet that orbits its star once every 14.4 days — was found by researchers from Google and The University of Texas at Austin using machine learning. Machine learning is an approach to artificial intelligence in which computers “learn.” In this case, computers learned to identify planets by finding in Kepler data instances where the telescope recorded signals from planets beyond our solar system, known as exoplanets.”

Video credit: NASA Ames Research Center

NASA dixit:

“NASA’s Parker Solar Probe is in the midst of intense environmental testing at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in preparation for its journey to the Sun. These tests simulate the noise and shaking the spacecraft will experience during its launch from Cape Canaveral, Florida, scheduled for 2018.

Parker Solar Probe’s integration and testing team must check over the spacecraft and systems to make sure everything is still in optimal working condition after experiencing these rigorous conditions – including a check of the solar arrays, which will provide electrical power to the spacecraft.

Parker Solar Probe will explore the Sun’s outer atmosphere and make critical observations that will answer decades-old questions about the physics of stars. The resulting data will also help improve how we forecast major eruptions on the Sun and subsequent space weather events that can impact life on Earth, as well as satellites and astronauts in space. The mission is named for Eugene N. Parker, whose profound insights into solar physics and processes have helped shape the field of heliophysics.”

Joy Ng (USRA): Producer

Sarah Frazier (ADNET SYSTEMS): Writer

Lee Hobson (APL): Videographer

Music credit: ‘Push Away’ by Andrew Michael Britton [PRS], David Stephen Goldsmith [PRS], Mikey Rowe [PRS] from Killer Tracks.

Video credit: NASA’s Goddard Space Flight Center