On a clear night sky, you might spot an occasional shooting star or even glimpse the fast-moving International Space Station as it circles the Earth.

But there are a lot of other objects up there too, including a massive new Japanese x-ray telescope called Hitomi that broke up a few weeks ago, and hundreds of tiny four-inch cube-shaped satellites ("cubesats") that are filling an ever more crowded orbital playground.

Now a group of astrophysical researchers say they can track bits of broken satellites and space junk using regular optical telescopes to record flashes of sunlight that reflect off these wandering probes. This week, they have been watching several big chunks of Hitomi as they tumble uncontrollably through space.

"As these things are going across the sky, they flash as the sunlight reflects on them," said Aroh Barjatya, associate professor of engineering physics at Embry-Riddle Aeronautical University in Daytona Beach, Fla. "Using photometry, we wrote a piece of code that centers them and measures the brightness of the object. When you are looking at controlled satellite, the brightness curve behaves in a known way. When you look at Hitomi, it's tumbling up and down. It has spin rate."

The team shot this video of one chunk of Hitomi flashing as stars pass by using a high-speed camera mounted on a telescope, and this video of the main body of Hitomi.

"It's as if a mirror were spinning in space," said Forrest Gasdia, a graduate student at Embry-Riddle, who made the observations this month.

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Barjatya said the group's observatory is specializing in tracking small cubesats -- many of them inexpensive, short-lived probes launched by university researchers that might fall through the cracks of the Pentagon's space junk tracking system.

"There are hundreds of universities launching them each year," Barjatya said. "We are potentially putting a lot of orbiting objects in the sky, many can breakup and fail and destroy other satellites. It hasn't happened. But as we put more and more up there, there is that possibility."

Barjatya says that half of the cubesats have lost contact with their operators. With a better optical tracking system, he hopes that provide more information about their fate.

The Pentagon's Joint Space Operations Center at Vandenberg Air Force Base is currently tracking 23,000 objects in space using radar and optical cameras. Their position are posted on this website each day.

JSpOC spokesman Capt. Nick Mercurio agreed that the space above Earth is getting more crowded. Every day, more than 3,000 automated messages are sent out to satellite operators about drifting debris or other satellites that may pose a risk. JSpOC is currently tracking 11 separate pieces of Hitomi since its breakup on March 26, Mercurio said, and has made five notifications warning other spacecraft operators that these bits are getting close to existing satellites.

PHOTOS: Satellite 'Flock' Launched From ISS Cubesat Cannon

In 2015, nearly 150 satellites had to be moved from their orbit to avoid colliding with something else. Astronauts aboard the ISS had to boost its orbit four times last year to avoid trouble.

"Low earth orbit is congested," Mercurio said. "Things are moving at 17,500 miles per hour and it can get dangerous. A two-centimeter ball bearing has same impact (energy of a) Jeep Wrangler driving at 70 miles per hour."

The Embry-Riddle team says they hope to improve their imaging capabilities with spectroscopic cameras that will be able to analyze the light reflecting off the space debris to determine whether it's a solar panel, piece of Teflon, aluminum or other kind of metal.

This article was provided by Discovery News.

A strange Y-shaped feature stretches like a tentacled monster across the icy surface of Saturn's moon Enceladus in a new image from NASA's Cassini spacecraft.

The giant, sinuous "Y," which appears at the boundary between sunlight and darkness in the photo, is a tectonic feature related to stresses in the icy shell of Enceladus, NASA officials said.

Such "Y-shaped discontinuities" likely arise "when surface material attempts to push northward, compressing or displacing existing ice along the way," NASA officials wrote Monday (April 18) in a description of the image. 

"Star Trek Continues" is exactly what it sounds like: A fan-made science fiction series that picks up where the original "Star Trek" TV show left off, putting Kirk, Spock and the rest of the starship Enterprise's crew through a whole new set of adventures in the final frontier. The cast — made up of of talented voice- and stage-actor Trek fans, including Vic Mignogna as executive producer (and Kirk) — works on an exact-replica set, evoking the original show's performances to create what feels like lost episodes from the series itself.

Since its debut in 2013, "Star Trek Continues" has published five episodes online, and the sixth will premiere in May. (Episode 7 is nearly done as well.) The project's crowdfunding campaign to finish Episode 7's post-production phase and film three more episodes is live on Indiegogo until May 4. 

Space.com caught up with Mignogna to talk about the show he calls his "love letter" to the original series, the key to "Star Trek" storytelling and what's to come in the next two episodes of the web series. (Plus, Space.com's own Karl Tate explores the set in this Trek-tastic new video.)

Space.com: How did "Star Trek Continues" begin?

Vic Mignogna: I've loved the original series of "Star Trek " ever since I was a little boy; I used to eat, sleep and breathe that show, basically. I would make my own uniforms and make my own props, and use my parents' movie camera to round up kids in the neighborhood to shoot little episodes. That show really inspired me when I was 10, 11, 12 years old, 13, 14.

Over the years, I have been developing skills in filmmaking and acting, and all different elements of production, and a few years ago I helped another fan production — I directed an episode for another fan production, and I kind of got bitten by the bug again. So I got a bunch of friends together and we all poured a lot of love and money and sweat and time and effort and talent into starting this web series. And people have really enjoyed it. We've got over 4 million views now, and have won a dozen awards, and people seem to really, really be enjoying it and it's very gratifying.

Space.com: How long did it take from the idea's inception to the first episode going up online?

Mignogna: We started out by releasing some little 3- to 5-minute dramatic vignettes introducing the world to our crew and the actors that were going to be playing those iconic roles, and we released three of those vignettes. They're all online, they're on our YouTube channel. They were basically a preview while we were finishing building all the sets and getting ready to shoot the first episode.

To date, we've been around three years and we've got six episodes: five online, released. The sixth one is done and will be premiering in May at Megacon, and the seventh episode is also done and will be premiering in the fall.

Space.com: Has the project grown in scale over time?

Mignogna: The project already started at its beginning at a higher level of quality than people had heretofore seen in fan production. But I will say with every episode, I feel like our cast and crew have gotten better and better. When we released a first episode, a lot of people were like, "Wow, how could you do any better than this?" And then we would release the second one and people would say, "Oh my gosh, I don't know how you did it, but this one's even better." And then the third one, they would say, "Oh my gosh, this one's even better, and the fourth one's even better, and the fifth one's even better!" So in different ways I think we are improving, but from the very beginning our quality level was extremely high. [See the Evolution of the Starship Enterprise in Photos]

Space.com: How do you decide on the specific plots or issues to focus on for particular episodes?

Mignogna: The original series' stories were very compelling stories that many times had an ethical theme or a moral plot or point or a social commentary, and so I was committed from the very beginning to telling those kinds of stories. And that's exactly what we've done. If you watch our episodes, you'll find that one of the things that makes [them] feel so much like the original series is that we tell very thought-provoking, intriguing, passion-filled stories.

Space.com: Can you say what's coming up in episodes six and seven?

Mignogna: I will tell you this: Our next episode is going to be so groundbreaking, nobody has ever done anything like this. I don't want to give away too much, but I will tell you that the engineering room will be featured prominently. It will be making its screen debut in Episode 6.

Gigi Edgley, who was one of the main characters in Farscape, is our guest star for this episode. And let me just say that there was an element that they incorporated into several episodes of the original series, and no fan production has done this to the degree that we're doing it in Episode 6.

And I will tell you that Episode 7 has already completed shooting. It's a wonderful, very, very thought-provoking episode about a very topical issue, and [I'm] very, very proud of that episode as well.

Space.com: What has been the most difficult part of producing the show?

Mignogna: Oh, my gosh, everything. I have to tell you, whenever you set out to do something at this level of quality, there are so many moving parts, and if you watch our episodes you see that there are tons and tons of elements to this production. Getting the lighting just right, getting the costumes just right, casting it, makeup, camera teams, sound team, props, art direction — there are dozens of moving parts that all have to come together to make it work, and I am so very, very proud of the team that I've assembled. The reason that we're able to do this quality-level work at a fraction of what it would normally cost is because everybody is basically doing it for virtually nothing. They're doing it because they love the original series of "Star Trek," they have a passion for it and they want to pay tribute to it the same way I do.

Space.com: What was it like putting together the replica sets?

Mignogna: The partial bridge was the only thing that had been built of all these sets when we partnered up [to work with another "Star Trek" fan production's set]. And then my director of photography, Matt Busey, did all of the diagrams and architectural drawings for all of the rest of the soundstage. And then a bunch of local volunteers, and just really good "Star Trek" fans, came together, including myself, and we all spent several months building all of the rest of the sets, and then three years ago we shot our first episode on those sets. So now — "Star Trek Continues" is the sole owner of those sets — we call our studio Stage 9, which is named after the soundstage where the original series was shot.

Our cast and crew come together at least twice a year to shoot episodes on those sets. They were patterned after the original series soundstage, and I would say that they were within inches of perfectly accurate to the original sets. [How 'Star Trek' Technology Works (Infographic)]

Space.com: Was there anything particularly hard to put together?

Mignogna: The pieces that were scattered all around the original soundstage were pieces from the 1960s; those pieces don't exist anymore. We need[ed] to come up with our own way to recreate and reproduce those pieces. And I'm very proud of the job we've done, doing so.

Let me say, as amazing as our sets are, at the end of the day, the sets are just a backdrop to the story. If the story isn't any good, if the acting isn't any good, then it really doesn't matter how accurate the sets are. The only reason that our sets need to be accurate is so the audience will immediately accept the setting as the original-series Enterprise or the original series of "Star Trek," and then allow us to tell them a good, thought-provoking story. That's one thing that a lot of fan productions miss. A lot of fan productions build really nice sets, or they make nice costumes, but those things are merely a vehicle to tell a good story. As far as "Star Trek Continues" is concerned, story, story, story is king. That's the most important thing.

Email Sarah Lewin at slewin@space.com or follow her @SarahExplains. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.

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The sound of merging supermassive black holes does not saturate the universe.

For the past decade, scientists with the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration have been listening for a constant "hum" of low-frequency gravitational waves.

Theoretical work suggests that this hum — generated by collisions involving supermassive black holes, which contain millions or billions of times more mass than the sun — should be detectable at Earth. NANOGrav hasn't heard the hum yet, a new study reveals, but this lack of detection is an interesting result in its own right, revealing new details of how galaxies might evolve and merge, team members said. [The Search for Gravitational Waves in Pictures]

Galactic gravitational wave detectors

Gravitational waves — cosmic ripples that distort the fabric of space-time itself — were first predicted by Albert Einstein in his theory of general relativity in 1916.

The first direct detection of these ripples was announced earlier this year, by researchers with the Laser Interferometer Gravitational-Wave Observatory (LIGO) project. The waves spotted by LIGO radiated outward from a cosmic crash between two black holes that were 29 and 36 times the mass of the sun, respectively. 

The $1 billion LIGO experiment bounces a laser beam between mirrors that are positioned at either end of two 2.5-mile-long (4 kilometers) arms. If a gravitational wave passes through the detector, the length of one of these arms will change ever so slightly compared to the other, affecting the arrival time of the laser light by a fraction of a second.

NANOGrav works on the same general principle, but it uses pulsars — dead stars that spin rapidly, up to hundreds of times each second — instead of Earth-based laser beams. And it hunts for supermassive black holes.

Pulsars emit beams of radiation from their magnetic north and south poles. If a pulsar happens to be aligned with Earth just right, astronomers will see flashes of its radiation, just as observers can see beacons of light from a lighthouse. These flashes can contain evidence of gravitational waves.

"As the gravitational wave transits the Milky Way, it stretches and squashes space-time, making the pulsars and the Earth jiggle," Chiara Mingarelli, an astronomer from the California Institute of Technology in Pasadena, told Space.com. "And we can measure that jiggle by looking at changes in the arrival time in the pulses."

Two pulsars "are like the interferometer arms on LIGO, but instead of being 4 kilometers long, they're 3,000 light-years long,” Mingarelli added. "A pulsar timing array is really a galactic-scale gravitational-wave detector." 

NANOGrav currently monitors 54 pulsars throughout the Milky Way using the Green Bank Telescope in West Virginia and the Arecibo Observatory in Puerto Rico, the two most sensitive radio telescopes operating at the necessary frequencies. Team members are hoping to hear a distinctive low-frequency sound.

"Whereas LIGO has this high-pitched chirp, pulsar timing arrays have a low growl from all these supermassive black holes combined," Mingarelli said. [What Colliding Black Holes Sound Like (Video)]

Why the silence?

When two galaxies collide, the supermassive black holes at the cores of each sink to the center of the newly created megagalaxy and swirl around one another. Scientists think that, over time, the black holes' orbits shrink, allowing them to merge and form an even more gigantic supermassive black hole.

But there's a problem with this scenario. While it’s easy to imagine how two supermassive black holes could come to orbit one another, astronomers struggle to model how the behemoths cross the final parsec (about 3.2 light-years) of space between each other to merge. In order to fall toward each other, the black holes have to radiate away energy — but exactly what that energy looks like, and how it changes as the black holes come closer together, is relatively unknown.

The simplest model predicts that black holes merge via gravitational-wave radiation for that entire final parsec. If that's the case, the supermassive black holes would radiate so many gravitational waves that a background "hum" should have been detected by now. But the new analysis of NANOGrav's nine-year dataset did not detect any such background.

However, that result isn’t surprising, said study co-author Justin Ellis, an astronomer at NASA's Jet Propulsion Laboratory in Pasadena.

"Most people in the field didn't really believe the optimistic model," Ellis told Space.com.

The likelihood that the background noise is relatively weak means that the physics involved are a little messier — and more interesting, researchers said.

There are two possible interpretations of the failure of the NANOGrav collaboration to detect any telltale noise until now. The first is that merging supermassive black holes shrink in their orbits because they interact with stars and gas. If the black holes slingshot stars away from the center of the galaxy, for example, that could cause them to lose the necessary energy and slouch toward the center. This would cause them to merge faster and emit less gravitational-wave radiation.

The other possibility is that the black holes spiral toward each other so slowly — on timescales longer than the age of the universe — that they essentially never merge.

"It’s weird to think that the centers of galaxies just have these massive binaries that just can't get together, but it's possible," Mingarelli said.

Within these models are many knobs that theorists can turn, Ellis said. Researchers can play with how quickly and efficiently supermassive black holes merge via interacting with gas and dust, slingshotting stars away from the center or simply emitting gravitational-wave radiation.

"It's a big parameter space, and this is the first study that can start to cut out some of the edges of that parameter space and limit how far the knobs can be turned," Ellis said.

The new study was published in The Astrophysical Journal.

Follow Shannon Hall on Twitter @ShannonWHall. Follow us @Spacedotcom, Facebook or Google+. Originally published on Space.com.