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Gamma-ray Bursts: Black Hole Birth Announcements

Gamma-ray bursts are the brightest, most violent explosions in the universe, but they can be surprisingly tricky to detect. Our eyes can’t see them because they are tuned to just a limited portion of the types of light that exist, but thanks to technology, we can even see the highest-energy form of light in the cosmos — gamma rays.

So how did we discover gamma-ray bursts? 

Accidentally!

We didn’t actually develop gamma-ray detectors to peer at the universe — we were keeping an eye on our neighbors! During the Cold War, the United States and the former Soviet Union both signed the Nuclear Test Ban Treaty of 1963 that stated neither nation would test nuclear weapons in space. Just one week later, the US launched the first Vela satellite to ensure the treaty wasn’t being violated. What they saw instead were gamma-ray events happening out in the cosmos!

Things Going Bump in the Cosmos

Each of these gamma-ray events, dubbed “gamma-ray bursts” or GRBs, lasted such a short time that information was very difficult to gather. For decades their origins, locations and causes remained a cosmic mystery, but in recent years we’ve been able to figure out a lot about GRBs. They come in two flavors: short-duration (less than two seconds) and long-duration (two seconds or more). Short and long bursts seem to be caused by different cosmic events, but the end result is thought to be the birth of a black hole.

Short GRBs are created by binary neutron star mergers. Neutron stars are the superdense leftover cores of really massive stars that have gone supernova. When two of them crash together (long after they’ve gone supernova) the collision releases a spectacular amount of energy before producing a black hole. Astronomers suspect something similar may occur in a merger between a neutron star and an already-existing black hole.

Long GRBs account for most of the bursts we see and can be created when an extremely massive star goes supernova and launches jets of material at nearly the speed of light (though not every supernova will produce a GRB). They can last just a few seconds or several minutes, though some extremely long GRBs have been known to last for hours!

A Gamma-Ray Burst a Day Sends Waves of Light Our Way!

Our Fermi Gamma-ray Space Telescope detects a GRB nearly every day, but there are actually many more happening — we just can’t see them! In a GRB, the gamma rays are shot out in a narrow beam. We have to be lined up just right in order to detect them, because not all bursts are beamed toward us — when we see one it’s because we’re looking right down the barrel of the gamma-ray gun. Scientists estimate that there are at least 50 times more GRBs happening each day than we detect!

So what’s left after a GRB — just a solitary black hole? Since GRBs usually last only a matter of seconds, it’s very difficult to study them in-depth. Fortunately, each one leaves an afterglow that can last for hours or even years in extreme cases. Afterglows are created when the GRB jets run into material surrounding the star. Because that material slows the jets down, we see lower-energy light, like X-rays and radio waves, that can take a while to fade. Afterglows are so important in helping us understand more about GRBs that our Neil Gehrels Swift Observatory was specifically designed to study them!

Last fall, we had the opportunity to learn even more from a gamma-ray burst than usual! From 130 million light-years away, Fermi witnessed a pair of neutron stars collide, creating a spectacular short GRB. What made this burst extra special was the fact that ground-based gravitational wave detectors LIGO and Virgo caught the same event, linking light and gravitational waves to the same source for the first time ever!

For over 10 years now, Fermi has been exploring the gamma-ray universe. Thanks to Fermi, scientists are learning more about the fundamental physics of the cosmos, from dark matter to the nature of space-time and beyond. Discover more about how we’ll be celebrating Fermi’s achievements all year!

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Lunar Eclipse 2019

Image Credit: Zachary Wells

Often times you look at really pretty images of Supernova remnants (what is left after a supernova explosion) and are blown away by their magnificence. But the sad truth is that there are not a lot of these supernovas that we can observe in such great detail.

On the bright side, in general there are lots of supernovas to observe in the universe. And the above is a spectacular time-lapse of the Supernova SN 2015F illustrating how the Luminosity of a Supernova varies with time. 

More:

Star snapped before and after nova explosion-BBC

Supernovas and Supernova remnants - Images

The Opportunity to Rove on Mars! 🔴

Today, we’re expressing gratitude for the opportunity to rove on Mars (#ThanksOppy) as we mark the completion of a successful mission that exceeded our expectations.  

Our Opportunity Rover’s last communication with Earth was received on June 10, 2018, as a planet-wide dust storm blanketed the solar-powered rover’s location on the western rim of Perseverance Valley, eventually blocking out so much sunlight that the rover could no longer charge its batteries. Although the skies over Perseverance cleared, the rover did not respond to a final communication attempt on Feb. 12, 2019.

As the rover’s mission comes to an end, here are a few things to know about its opportunity to explore the Red Planet.

90 days turned into 15 years!

Opportunity launched on July 7, 2003 and landed on Mars on Jan. 24, 2004 for a planned mission of 90 Martian days, which is equivalent to 92.4 Earth days. While we did not expect the golf-cart-sized rover to survive through a Martian winter, Opportunity defied all odds as a 90-day mission turned into 15 years!

The Opportunity caught its own silhouette in this late-afternoon image taken in March 2014 by the rover’s rear hazard avoidance camera. This camera is mounted low on the rover and has a wide-angle lens.

Opportunity Set  Out-Of-This-World Records

Opportunity’s achievements, including confirmation water once flowed on Mars. Opportunity was, by far, the longest-lasting lander on Mars. Besides endurance, the six-wheeled rover set a roaming record of 28 miles.

This chart illustrates comparisons among the distances driven by various wheeled vehicles on the surface of Earth’s moon and Mars. Opportunity holds the off-Earth roving distance record after accruing 28.06 miles (45.16 kilometers) of driving on Mars.

It’s Just Like Having a Geologist on Mars

Opportunity was created to be the mechanical equivalent of a geologist walking from place to place on the Red Planet. Its mast-mounted cameras are 5 feet high and provided 360-degree two-eyed, human-like views of the terrain. The robotic arm moved like a human arm with an elbow and wrist, and can place instruments directly up against rock and soil targets of interest. The mechanical “hand” of the arm holds a microscopic camera that served the same purpose as a geologist’s handheld magnifying lens.

There’s Lots to See on Mars

After an airbag-protected landing craft settled onto the Red Planet’s surface and opened, Opportunity rolled out to take panoramic images. These images gave scientists the information they need to select promising geological targets that tell part of the story of water in Mars’ past. Since landing in 2004, Opportunity has captured more than 200,000 images. Take a look in this photo gallery.

From its perch high on a ridge, the Opportunity rover recorded this image on March 31, 2016 of a Martian dust devil twisting through the valley below. The view looks back at the rover’s tracks leading up the north-facing slope of “Knudsen Ridge,” which forms part of the southern edge of “Marathon Valley

There Was Once Water on Mars?!

Among the mission’s scientific goals was to search for and characterize a wide range of rocks and soils for clues to past water activity on Mars. In its time on the Red Planet, Opportunity discovered small spheres of the mineral hematite, which typically forms in water. In addition to these spheres that a scientist nicknamed “blueberries,” the rover also found signs of liquid water flowing across the surface in the past: brightly colored veins of the mineral gypsum in rocks, for instance, which indicated water flowing through underground fractures.

The small spheres on the Martian surface in this close-up image are near Fram Crater, visited by the Opportunity rover in April 2004.

For more about Opportunity’s adventures and discoveries, see: https://go.nasa.gov/ThanksOppy.

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Created using still images taken by the Cassini spacecraft during it’s flyby of Jupiter and while at Saturn. Shown is Io and Europa over Jupiter’s Great Red Spot.

NASA/JPL-Caltech/SSI/CICLOPS/Kevin M. Gill

Take your time. You’ll get it.

420 more like 440 lol stay in tune, guys