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The Mystery of the "Space Roar"

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In 2009, scientists at NASA's Goddard Space Flight Center sent a machine called ARCADE into space on a giant balloon, in search of radiation from the universe's earliest stars. ARCADE (Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission) carried seven sensors that picked up electromagnetic radiation like radio waves. The plan was to lift it far enough up to prevent the Earth's atmosphere from interfering. Then, the finely-tuned instrument could detect faint radio signals from ancient stars.

Instead, ARCADE detected a huge amount of radio noise—six times louder than scientists had predicted—which has since come to be known as the "space roar." And while there are some theories, we still don't know what's causing it.

Space Sounds

Of course, space isn't roaring in any way that our ears could hear. But there are objects in the universe—including some galaxies—which emit radio waves via synchrotron radiation.

According to Dale Fixsen, a University of Maryland research scientist and a member of the ARCADE team, NASA had built devices that detected radio noise before. These worked by looking at one point in the sky, and then at another nearby one for contrast. These instruments were useful for detecting radio-emitting galaxies and supernovas, because they measured the difference between two points. But they couldn't detect the roar.

"If there's a uniform source [of synchrotron radiation], those instruments are blind to it," Fixsen tells mental_floss.

On the other hand, ARCADE used a "large beam" that searched 7 percent of the sky. Because of the large area it searched, and its high-precision sensors, it was the first instrument we've built that could discover the roar.

But it couldn't find out everything. Fixsen says that synchrotron radiation has a characteristic spectrum. And since every source of the radiation displays this same spectrum, ARCADE couldn't discover what was roaring.

Roar Theories

Fixsen says that synchrotron radiation usually comes hand in hand with infrared radiation. We've already measured the amount of infrared radiation that the Milky Way emits with the COBE satellite, and according to Fixsen, with our galaxy's level of infrared, it doesn't look like the Milky Way is the source of the synchrotron radiation for the "space roar."

"The relationship is tight for all galaxies we've measured," Fixsen says. "It should hold true for our galaxy as well."

On the other hand, theorists think that we've detected almost all the sources of this radiation outside our galaxy. And we know that none of these sources is causing the "roar."

According to Fixsen, there are a few possible explanations. First, the "roar" could be coming from the earliest stars. The first stars didn't have any dust—because the first dust in the universe was formed within those stars. This could have let those stars create a lot of synchrotron radiation, without a correspondingly high amount of infrared.

Second, the radiation might be coming from gases in large clusters of galaxies—Fixsen says that it would be difficult for the instruments we've used up until now to detect radiation from these.

Third, it could be coming from dim, but extremely plentiful, radio galaxies. Individually, they would be too quiet for us to detect, but en masse they might be loud enough to create the "roar."

Future plans

But while there are some plausible theories, we still don't have any data to tell us which one is right. Fixsen says that there's been talk about flying ARCADE again (it's currently living in the Goddard Space Flight Center). Or they might use an instrument on the ground next time; Fixsen says they could use the data from the ARCADE mission to calibrate it, and avoid interference from the atmosphere.

But for now, what NASA wrote in its 2009 press release is still true: "The source of this cosmic radio background remains a mystery."

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Space
SpaceX's Landing Blooper Reel Shows That Even Rocket Scientists Make Mistakes
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SpaceX's Falcon 9 rocket launches.
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On March 30, 2017, SpaceX did something no space program had done before: They relaunched an orbital class rocket from Earth that had successfully achieved lift-off just a year earlier. It wasn't the first time Elon Musk's company broke new ground: In December 2015, it nailed the landing on a reusable rocket—the first time that had been done—and five months later landed a rocket on a droneship in the middle of the ocean, which was also unprecedented. These feats marked significant moments in the history of space travel, but they were just a few of the steps in the long, messy journey to achieve them. In SpaceX's new blooper reel, spotted by Ars Technica, you can see just some of the many failures the company has had along the way.

The video demonstrates that failure is an important part of the scientific process. Of course when the science you're working in deals with launching and landing rockets, failure can be a lot more dramatic than it is in a lab. SpaceX has filmed their rockets blowing up in the air, disintegrating in the ocean, and smashing against landing pads, often because of something small like a radar glitch or lack of propellant.

While explosions—or "rapid unscheduled disassemblies," as the video calls them—are never ideal, some are preferable to others. The Falcon 9 explosion that shook buildings for miles last year, for instance, ended up destroying the $200 million Facebook satellite onboard. But even costly hiccups such as that one are important to future successes. As Musk once said, "If things are not failing, you are not innovating enough."

You can watch the fiery compilation below.

[h/t Ars Technica]

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Space
Here's Where You Can Watch a Livestream of Cassini's Final Moments
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It's been a road trip like no other. After seven years and 2.2 billion miles, the NASA orbiter Cassini finally arrived at the Saturn system on June 30, 2004. Ever since, it's been capturing and transmitting valuable data about the distant environment. From sending the Huygens probe to land on the moon Titan to witnessing hurricanes on both of the planet's poles, Cassini has informed more than 3000 scientific papers.

It's been as impressive a mission as any spacecraft has ever undertaken. And tomorrow, Cassini will perform one last feat: sacrificing itself to Saturn's intense atmosphere. Project scientists are deliberately plunging it into the planet in order to secure just a little more data—and to keep the spacecraft, which is running low on fuel, from one day colliding with a Saturnian moon that might harbor life.

Because it won't have time to store anything on its hard drive, Cassini will livestream its blaze of glory via NASA. The information will be composed mostly of measurements, since pictures would take too long to send. Instead, we'll get data about Saturn's magnetic field and the composition of its dust and gas.

"As we fly through the atmosphere, we are able to literally scoop up some molecules, and from those we can figure out the ground truth in Saturn’s atmosphere," Scott Edgington, a Cassini project scientist, told New Scientist. "Just like almost everything else in this mission, I expect to be completely surprised."

The action will kick off at 7 a.m. EDT on Friday, September 15. Scientists expect to say goodbye to Cassini less than an hour later. 

While you wait for Cassini's grand finale, you can check out some essential facts we've rounded up from Saturn experts. And keep your eyes peeled for a full recap of Cassini’s historic journey: Mental Floss will be in the control room at the Jet Propulsion Laboratory in Pasadena, California, to offer a firsthand account of the craft's final moments in space. 

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