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This Is What We Know About Black Holes In Advance Of The Event Horizon Telescope’s First Image

“For hundreds of years, humanity has expected black holes to exist. Over the course of all of our lifetimes, we’ve collected an entire suite of evidence that points not only to their existence, but to a fantastic agreement between their expected theoretical properties and what we’ve observed. But perhaps the most important prediction of all — that of the event horizon’s existence and properties — has never been directly tested before.

With simultaneous observations in hand from hundreds of telescopes across the globe, scientists have finished reconstructing an image, based on real data, of the largest black hole as seen from Earth: the 4 million solar mass monster at the center of the Milky Way. What we’ll see on April 10 will either further confirm General Relativity or cause us to rethink all that we believe about gravity. Eager with anticipation, the world now awaits.”

The Event Horizon Telescope will, on April 10 (tomorrow, at the time of this writing), release an image two years in the making: of the event horizon of the black hole at the Milky Way’s center. Many will look at this as the first definitive proof that black holes truly exist, but we mustn’t forget all the (overwhelming!) evidence we already have in hand. There is a ton that we already know about black holes that has been demonstrated observationally, and all of it is in spectacular agreement with what we theoretically expect.

On the eve of the Event Horizon Telescope’s big announcement, take some time to get a little perspective, and learn what we already know about black holes!

Pulsar planets are planets that are found orbiting pulsars, or rapidly rotating neutron stars. The first such planet to be discovered was around a millisecond pulsar and was the first extrasolar planet to be confirmed as discovered.

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Greatest Hits — Craters We Love

Our solar system was built on impacts — some big, some small — some fast, some slow. This week, in honor of a possible newly-discovered large crater here on Earth, here’s a quick run through of some of the more intriguing impacts across our solar system.

1. Mercury: A Basin Bigger Than Texas

Mercury does not have a thick atmosphere to protect it from space debris. The small planet is riddled with craters, but none as spectacular as the Caloris Basin. “Basin” is what geologists call craters larger than about 186 miles (300 kilometers) in diameter. Caloris is about 950 miles (1,525 kilometers) across and is ringed by mile-high mountains.

For scale, the state of Texas is 773 miles (1,244 kilometers) wide from east to west.

2. Venus: Tough on Space Rocks

Venus’ ultra-thick atmosphere finishes off most meteors before they reach the surface. The planet’s volcanic history has erased many of its craters, but like almost any place with solid ground in our solar system, there are still impact scars to be found. Most of what we know of Venus’ craters comes from radar images provided by orbiting spacecraft, such as NASA’s Magellan.

Mead Crater is the largest known impact site on Venus. It is about 170 miles (275 kilometers) in diameter. The relatively-flat, brighter inner floor of the crater indicates it was filled with impact melt and/or lava.

3. Earth: Still Craters After All These Years

Evidence of really big impacts — such as Arizona’s Meteor Crater — are harder to find on Earth. The impact history of our home world has largely been erased by weather and water or buried under lava, rock or ice. Nonetheless, we still find new giant craters occasionally.

A NASA glaciologist has discovered a possible impact crater buried under more than a mile of ice in northwest Greenland.

This follows the finding, announced in November 2018, of a 19-mile (31-kilometer) wide crater beneath Hiawatha Glacier – the first meteorite impact crater ever discovered under Earth’s ice sheets. 

If the second crater, which has a width of over 22 miles (35 kilometers), is ultimately confirmed as the result of a meteorite impact, it will be the 22nd largest impact crater found on Earth.

4. Moon: Our Cratered Companion

Want to imagine what Earth might look like without its protective atmosphere, weather, water and other crater-erasing features? Look up at the Moon. The Moon’s pockmarked face offers what may be humanity’s most familiar view of impact craters.

One of the easiest to spot is Tycho, the tight circle and bright, radiating splat are easy slightly off center on the lower-left side of the full moon. Closer views of the 53-mile (85 kilometer)-wide crater from orbiting spacecraft reveal a beautiful central peak, topped with an intriguing boulder that would fill about half of a typical city block.

5. Mars: Still Taking Hits

Mars has just enough atmosphere to ensure nail-biting spacecraft landings, but not enough to prevent regular hits from falling space rocks. This dark splat on the Martian south pole is less than a year old, having formed between July and September 2018. The two-toned blast pattern tells a geologic story. The larger, lighter-colored blast pattern could be the result of scouring by winds from the impact shockwave on ice. The darker-colored inner blast pattern is because the impactor penetrated the thin ice layer, blasting the dark sand underneath in all directions.

6. Ceres: What Lies Beneath

The bright spots in Ceres’ Occator crater intrigued the world from the moment the approaching Dawn spacecraft first photographed it in 2015. Closer inspection from orbit revealed the spots to be the most visible example of hundreds of bright, salty deposits that decorate the dwarf planet like a smattering of diamonds. The science behind these bright spots is even more compelling: they are mainly sodium carbonate and ammonium chloride that somehow made their way to the surface in a slushy brine from within or below the crust. Thanks to Dawn, scientists have a better sense of how these reflective areas formed and changed over time — processes indicative of an active, evolving world.

7. Comet Tempel 1: We Did It!

Scientists have long known we can learn a lot from impact craters — so, in 2005, they made one themselves and watched it happen.

On July 4, 2005, NASA’s Deep Impact spacecraft trained its instruments on an 816-pound (370-kilogram) copper impactor as it smashed into comet Tempel 1.

One of the more surprising findings: The comet has a loose, “fluffy” structure, held together by gravity and contains a surprising amount of organic compounds that are part of the basic building blocks of life.

8. Mimas: May the 4th Be With You

Few Star Wars fans — us included — can resist Obi Wan Kenobi’s memorable line “That’s no moon…” when images of Saturn’s moon Mimas pop up on a screen. Despite its Death Star-like appearance, Mimas is most definitely a moon. Our Cassini spacecraft checked, a lot — and the superlaser-looking depression is simply an 81-mile (130-kilometer) wide crater named for the moon’s discoverer, William Herschel.

9. Europa: Say What?

The Welsh name of this crater on Jupiter’s ocean moon Europa looks like a tongue-twister, but it is easiest pronounced as “pool.” Pwyll is thought to be one of the youngest features we know of on Europa. The bright splat from the impact extends more than 600 miles (about 1,000 kilometers) around the crater, a fresh blanket over rugged, older terrain. “Fresh,” or young, is a relative term in geology; the crater and its rays are likely millions of years old.

10. Show Us Your Greatest Hits

Got a passion for Stickney, the dominant bowl-shaped crater on one end of Mars’ moon Phobos? Or a fondness for the sponge-like abundance of impacts on Saturn’s battered moon Hyperion (pictured)? There are countless craters to choose from. Share your favorites with us on Twitter, Instagram and Facebook.

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

Take me back to California 🌴❤️

NASA Astronauts And Satellites Capture Breathtaking Images Of An Awakening Volcano From Space

“Volcanoes are some of the most fascinating but also dangerous and deadly natural disasters. Fortunately, with appropriate monitoring, they’re one of the most easily mitigated classes of disasters as well. There are approximately 1,500 potentially active volcanoes on Earth at any time, which doesn’t include undersea volcanoes that have not reached the surface or inactive ones that might surprise us.

Only by continuously monitoring the entire Earth at the appropriate resolutions and cadences can we hope to truly minimize the risk to human life and property. Attempts to cut back on this endeavor harm and endanger us all, while an awareness and appreciation for what Earth observing brings us is our greatest asset. May the beauty of these pictures point the way to the most important truth: that comprehensive knowledge and more information are absolutely key to optimally navigating the challenges of being human on our living planet Earth.”

Just a few days ago, on June 22, 2019, a volcano that hadn’t erupted in nearly a century suddenly sprang to life, belching out waves of ash and volcanic gas high into the stratosphere and posing severe threats to nearby life. But far more at-risk were airplanes, which routinely fly through the region where volcanic ash particles were spewed by this eruption. Due to our full suite of Earth observatories, with an assist from astronauts aboard the International Space Station and ground-based monitoring, we were able to minimize the danger and avoid significant damage. Without NASA’s commitment to Earth monitoring, a commitment that’s continually fighting off attempted cuts, mitigating the risks of volcanic eruptions would be hamstrung by humanity’s greatest danger: willful ignorance.

Come take a look at the spectacular story of the recent eruption of Raikoke volcano, and learn why Earth observing is so important in the process!

Working too hard, feeling overwhelmed by family responsibilities, or dealing with an ongoing challenge? 

Maybe it’s time to turn your attention back to yourself and to your own self-care. Although we often brush it aside, self-care is not optional if you want to be happy and healthy.

All cats are beautiful 🐱❤️

Ask Ethan: Where Is The Center Of The Universe?

“I am wondering how there isn’t a center of the universe and how the cosmic background radiation is [equally] far away everywhere we look. It seems to me that when the universe expands… there should be a place where it started expanding.”

Ah, the old center of the Universe question. If the Big Bang happened a long time ago, and we see galaxies moving away from us faster and faster the farther away they are, then where did the Big Bang happen? Where did the expansion start?

It seems like such a simple question, but it turns out this is the wrong question to be asking. The way space and the expanding Universe works is very different from the picture most of us have in our heads, which is much more like an explosion than like an expansion. Yet there’s a very large suite of evidence that points us away from an explosion.

Instead of asking *where* the Big Bang occurred, we should be asking *when* the Big Bang occurred. It makes a lot more sense when you think about it in those terms. Come and find out why.

HiPOD (31 August 2018) Dunes in South Xainza Crater

   – They look so innocent… (270 km above the surface. Black and white is less than 5 km across; enhanced color is less than 1 km.)

NASA/JPL/University of Arizona