High-resolution Images Of Pluto Taken By NASA’s New Horizons Spacecraft.

This image shows knots of cold, dense interstellar gas where new stars are forming. These Free-floating Evaporating Gaseous Globules (frEGGs) were first seen in Hubble’s famous 1995 image of the Eagle Nebula. Because these lumps of gas are dark, they are rarely seen by telescopes. They can be observed when the newly forming stars ignite, their intense ultraviolet radiation eroding the surrounding gas away and letting the denser, more resistant frEGGs remain. These frEGGs are located in the Northern Coalsack Nebula in the direction of Cygnus.

Credit: NASA, ESA, and R. Sahai (Jet Propulsion Laboratory); Processing: Gladys Kober (NASA/Catholic University of America)

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The Rift.

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Characteristics of the moons of Saturn

Saturn has 62 natural satellites. Here are some features of some of its moons, with mountains, valleys, and striking marks on their surfaces, often marked by asteroid bombardments causing small, huge craters.

Iapetus -  Equatorial ridge

Iapetus’s equatorial ridge was discovered when the Cassini spacecraft imaged Iapetus on 31 December 2004. Peaks in the ridge rise more than 20 km above the surrounding plains, making them some of the tallest mountains in the Solar System. The ridge forms a complex system including isolated peaks, segments of more than 200 km and sections with three near parallel ridges. 

Tethys - Odysseus crater

Odysseus is the largest crater on Saturn’s moon Tethys. It is 445 km across, more than 2/5 of the moon’s diameter, and is one of the largest craters in the Solar System.

Tethys - Ithaca Chasma

Ithaca Chasma is a valley (graben) on Saturn’s moon Tethys, named after the island of Ithaca, in Greece. It is up to 100 km wide, 3 to 5 km deep and 2,000 km long, running approximately three-quarters of the way around Tethys’ circumference, making it one of the longer valleys in the Solar System. Ithaca Chasma is approximately concentric with Odysseus crater. 

Tethys - Red arcs

Unusual arc-shaped, reddish streaks cut across the surface of Saturn’s ice-rich moon Tethys in this enhanced-color mosaic. The red streaks are narrow, curved lines on the moon’s surface, only a few miles (or kilometers) wide but several hundred miles (or kilometers) long.

Rhea - Inktomi crater

Inktomi, also known as The Splat, is a prominent rayed impact crater 47.2 kilometres (29.3 mi) in diameter located in the southern hemisphere of Saturn’s moon Rhea.

Mimas - Herschel Crater

Herschel is a huge crater in the leading hemisphere of the Saturnian moon Mimas, on the equator at 100° longitude. It is so large that astronomers have expressed surprise that Mimas was not shattered by the impact that caused it. It measures 139 kilometres (86 miles) across, almost one third the diameter of Mimas. If there were a crater of an equivalent scale on Earth it would be over 4,000 km (2,500 mi) in diameter – wider than Canada – with walls over 200 km (120 mi) high.

Enceladus - Surface with fractures

Close up of one of the ‘tiger stripes” or fissures called Baghdad Sulcus. Both heat and occasional geysers issue from this formidable crack. Some of the material coating the landscape may be snow condensed from vapor. This closeup of the surface of Enceladus on November 21, 2009, viewed from approximately 1,260 miles (2,028 kilometers) away. 

Dione - Contrasts

This image from NASA’s Cassini spacecraft shows a part of Dione’s surface that is covered by linear, curving features, called chasmata. One possibility is that this stress pattern may be related to Dione’s orbital evolution and the effect of tidal stresses over time. This view looks toward the trailing hemisphere of Dione. 

Learn more: Iapetus, Tethys, Rhea, Mimas, Enceladus and Dione.

Images: NASA/JPL-Caltech

Why Won’t Our Parker Solar Probe Melt?

This summer, our Parker Solar Probe will launch to travel closer to the Sun than any mission before it, right into the Sun’s outer atmosphere, the corona.

The environment in the corona is unimaginably hot: The spacecraft will travel through material with temperatures greater than 3 million degrees Fahrenheit. 

So…why won’t it melt? 

The Difference Between Heat and Temperature

Parker Solar Probe was designed from the ground up to keep its instruments safe and cool, but the nature of the corona itself also helps. The key lies in the difference between heat and temperature.

Temperature measures how fast particles are moving, while heat is the total amount of energy that they transfer. The corona is an incredibly thin and tenuous part of the Sun, and there are very few particles there to transfer energy – so while the particles are moving fast (high temperature), they don’t actually transfer much energy to the spacecraft (low heat).

It’s like the difference between putting your hand in a hot oven versus putting it in a pot of boiling water (don’t try this at home!). In the air of the oven, your hand doesn’t get nearly as hot as it would in the much denser water of the boiling pot. 

So even though Parker Solar Probe travels through a region with temperatures of several million degrees, the surface of its heat shield will reach only about 2,500 F.

The Heat Shield

Of course, thousands of degrees Fahrenheit is still way too hot for scientific instruments. (For comparison, lava from volcano eruptions can be anywhere between 1,300 to 2,200 F.) 

To withstand that heat, Parker Solar Probe is outfitted with a cutting-edge heat shield, called the Thermal Protection System. This heat shield is made of a carbon composite foam sandwiched between two carbon plates. The Sun-facing side is covered with a specially-developed white ceramic coating, applied as a plasma spray, to reflect as much heat as possible.

The heat shield is so good at its job that even though the Sun-facing side of the shield will be at 2,500 F, the instruments in its shadow will remain at a balmy 85 F.

Parker Solar Probe Keeps its Cool

Several other designs on the spacecraft help Parker Solar Probe beat the heat. 

Parker Solar Probe is not only studying the Sun – it’s also powered by it. But even though most of the surface area of its solar arrays can be retracted behind the heat shield, even that small exposed segment would quickly make them overheat while at the Sun.  

To keep things cool, Parker Solar Probe circulates a single gallon of water through its solar arrays. The water absorbs heat as it passes behind the arrays, then radiates that heat out into space as it flows into the spacecraft’s radiator. 

It’s also important for Parker Solar Probe to be able to think on its feet, since it takes about eight minutes for information to travel between Earth and the Sun. If we had to control the spacecraft from Earth, by the time we knew something went wrong, it would be too late to fix it. 

So Parker Solar Probe is smart: Along the edges of the heat shield’s shadow are seven sensors. If any of these sensors detect sunlight, they alert the central computer and the spacecraft can correct its position to keep the sensors – and the rest of the instruments – safely protected behind the heat shield.

Over the course of its seven-year mission, Parker Solar Probe will make 24 orbits of our star. On each close approach to the Sun, it will sample the solar wind, study the Sun’s corona, and provide unprecedentedly close up observations from around our star – and armed with its slew of innovative technologies, we know it will keep its cool the whole time. 

Parker Solar Probe launches summer 2018 on its mission to study the Sun. Keep up with the latest on the mission at nasa.gov/solarprobe or follow us on Twitter and Facebook.

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A Mesmerizing Model of Monster Black Holes

Just about every galaxy the size of our Milky Way (or bigger) has a supermassive black hole at its center. These objects are ginormous — hundreds of thousands to billions of times the mass of the Sun! Now, we know galaxies merge from time to time, so it follows that some of their black holes should combine too. But we haven’t seen a collision like that yet, and we don’t know exactly what it would look like. 

A new simulation created on the Blue Waters supercomputer — which can do 13 quadrillion calculations per second, 3 million times faster than the average laptop — is helping scientists understand what kind of light would be produced by the gas around these systems as they spiral toward a merger.

The new simulation shows most of the light produced around these two black holes is UV or X-ray light. We can’t see those wavelengths with our own eyes, but many telescopes can. Models like this could tell the scientists what to look for. 

You may have spotted the blank circular region between the two black holes. No, that’s not a third black hole. It’s a spot that wasn’t modeled in this version of the simulation. Future models will include the glowing gas passing between the black holes in that region, but the researchers need more processing power. The current version already required 46 days!

The supermassive black holes have some pretty nifty effects on the light created by the gas in the system. If you view the simulation from the side, you can see that their gravity bends light like a lens. When the black holes are lined up, you even get a double lens!

But what would the view be like from between two black holes? In the 360-degree video above, the system’s gas has been removed and the Gaia star catalog has been added to the background. If you watch the video in the YouTube app on your phone, you can moved the screen around to explore this extreme vista. Learn more about the new simulation here. 

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.

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