Do Advanced Civilizations Communicate with Neutrinos?

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It’s one of the biggest questions in all humanity: are we alone in the Universe? Either way, the answer is significant. And so, scientists are searching for intelligence out there. Huge arrays of radio telescopes, like the Allen Array scan the skies for radio broadcasts. And researchers have also proposed that aliens might be using lasers to communicate with us. A Russian researcher is proposing another way that aliens might be communicating with us – with neutrinos.

To borrow a quote from the Hitchhiker’s Guide to the Galaxy, “Space is big. You just won’t believe how vastly, hugely, mind- bogglingly big it is.” When you’re attempting to communicate across the vast distances of space, you need huge amounts of energy. Just look at a star, even though it’s generating an incomprehensible amount of energy every second, the brightness drops dramatically with distance.

Instead of broadcasting in all directions, the other strategy is to focus your communications towards a specific location. A targeted beam of radio waves or laser light towards another star still requires an enormous amount of energy, but it’s less.

To save energy, alien civilizations might not be using radio or optical light at all, they might be communicating in a completely different way, with neutrinos.

Researcher Z. K. Silagadze at the Budker Institute of Nuclear Physics and Novosibirsk State University recently posted this idea to the Arxiv pre-press mailing list. His article is called SETI and Muon Collider.

It might sound like science fiction, but scientists are starting to understand how to generate beams of neutrinos – by creating beams of muons. Beams of these unstable particles can be generated in large particle accelerators. The muon beam decays quickly into a focused beam of neutrinos that can travel for light years and still remain remarkably coherent. A beam fired at relatively nearby star Tau Ceti, 12 light-years away, would open up to about 600 astronomical units across – enough to bathe the whole system in neutrinos that could be tracked back to a specific source star.

Finding neutrinos here on Earth is difficult. We’ve got an incredible amount of neutrinos stream towards us from the Sun. In fact, you’ve got billions of neutrinos passing through your body every second and you never feel them because never interact. It takes a huge vat of water, protected underground from other radiation and a suite of sensitive detectors. And even then, they only turn up a few thousand neutrinos a year.

In fact, a neutrino can pass through light-years of pure lead and not even notice.

But there are some advantages. Neutrino detectors are omnidirectional – they don’t have to be targeted in a specific direction to “tune in” a signal coming from a star. If the stream of neutrinos is passing through the Earth, we should be able to detect it, and then track back the source after the fact.

Neutrino detectors are also sensitive to many different energy levels. They don’t have to scan specific frequencies, they can detect high energy neutrinos as easily as low-energy ones.

According to Silagadze, the newly developed IceCube neutrino observatory being built in Antarctica should have the sensitivity to spot neutrinos generated on purpose by alien civilizations – whether they’re targeting us specifically, or we’re just overhearing their conversations.

It has been suggested that advanced civilizations might deliberately choose neutrinos for communications because it shuts out the very young, and not mature civilizations from the galactic conversation.

But give us a few years, and we’ll be listening.

Original Source: Arxiv

That Dark Stuff, Matter and Energy

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Being a very hands-on-type person, I have a hard time wrapping my brain around the concepts of dark energy and dark matter. These are invisible, hypothetical stuffs that cosmologists tell us make up a combined 96% of the universe. These ubiquitous substances are unlike anything we’re familiar with. They don’t emit or reflect enough electromagnetic radiation to be detected directly, but their presence is inferred by the gravitational effect they have on everything we can see. So, scientists are trying to determine if dark energy and dark matter are really there, and if so, what they’re made of. A couple of studies have come out recently dealing with dark energy and dark matter. One study released says that what we think might be dark energy may only be tiny whiskers of carbon materials, formed in the early days of the universe. And a new experiment tried to determine if dark matter is made of particles called axions.

Andrew Steele and Marc Fries from the Carnegie Institution say that what we thought was dark energy may just be a haze of tiny whiskers of carbon, strewn across the universe and perhaps those whiskers — and not dark energy — would dim faraway objects such as supernovae. Scientists proposed the dark energy hypothesis a decade ago in part to explain the unexpected dimness of certain stellar explosions.

The researchers report discovering an unusual new form of carbon in minerals within meteorites dating from the formation of the solar system. They believe the “graphite whiskers� were likely produced from hot, carbon-rich gases that formed near stars and were blown into interstellar space by solar winds or supernovae. A thin haze of the whiskers in space would affect how light of different wave-lengths pass through space. The researchers postulated that light of near-infrared wavelengths would be particularly affected—the same wavelengths whose dimming first led to the dark energy model.

Things like these graphite whiskers have been proposed previously to possibly explain observations where dimming appeared, but the presence of any types of materials in space has never been confirmed previously, said Steele and Fries. With their discovery in the meteorite, the pair added, researchers can test the whiskers’ properties against theories and observations.

Dark matter: To make hypothetical matter, you might just need a little dash of hypothetical particles. How about axions? Axions are theoretical particles that have a small mass, about 500 million times lighter than an electron. Additionally, according to theory, an axion should have no spin. A group from the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois designed an experiment to try to find axions.

They set up a magnetic field and shot a lazer into it. A “wall� was placed in the middle of the magnetic field as well. It was thought that the magnetic field would possibly change some of the photons from the laser into axions. The wall would stop the photons, but the axions would emerge on the other side.

They tried four different configurations of their system, unfortunately, the experiment found no evidence of new particles. But, they were able to exclude some constraints or regions where this type of particle could or could not exist.

And the data from the Fermilab experiment is still being examined. Scientist William Wester is optimistic about the role he and his colleagues are playing. “We did a serious measurement and excluded a region,� he says. “If our small experiment helps heighten awareness and leads to more experimental efforts, even using other techniques as well, it will be a huge benefit that we have done this.�

The group believes that maybe with a stronger magnetic field, it might be worth trying their experiement again.

This brings to mind something that I heard cosmologist Michael Turner say: “If I succeed in confusing you about dark matter and dark energy, then I will have brought you up to where the experts are.â€?

Original News Sources:
World Science
Physorg.com release

Book Review: A Dictionary of Astronomy

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Dictionaries, as guides, ensure everyone uses words in a like manner. Specialized dictionaries allow more complete coverage for particular fields. Ian Ridpath has updated A Dictionary of Astronomy that, as the title implies, gives definitions to much of the astronomer’s vernacular. It’s as unexciting as any reference text but as valuable as any fine resource.

Spoken words allow people to readily communicate. Being able to convey abstract ideas and images separates humans from other species and raises us to be the most technically accomplished. This, coupled with our unending curiosity and inventiveness, keeps our language growing and morphing.

One would think that, with all this change, a dictionary is counter-productive. Yet, we need a common basis when communicating, and Ridpath’s dictionary provides such. In this book, explanations describe over 4200 entries. These can be generally and almost evenly divided into: technical, proper names and personal names. Definitions for each can be as succinct as a few words or as voluminous as a couple of pages. However, most are at a moderate paragraph in length. And, as with most dictionaries, the explanations are adequate, being neither fluffy nor abbreviated. An omission is the lack of any help with pronunciation. A nice addition, though, is a clever method that clearly indicates when an explanation has words or expressions that are themselves defined elsewhere in the book. Hence, this dictionary does wonderfully as the ready reference it needs to be.

In regard to this dictionary’s scope, Ridpath has kept it closely aligned to astronomy. There’s no ingress from rocketry or space flight aside from a table of the Apollo flights in the appendix. And only the slightest allowance is made for special terms from physics. Yet, many common words arise, though with definitions appropriated purely for this field. Consider the moustache, a small, very bright point in solar active regions. Personal favourites include; almucantar, gnomon and regmaglypt. Finding these and others is simply a matter of using the leading and trailing entries shown at the top of each page. Thus, as the dictionary is to clarify and standardize, this dictionary meets this measure.

This dictionary is a good reference for a generalist who only occasionally dips their toes into astronomy. Also, for a specialist in one realm of astronomy, like telescopes, who’s perhaps weak in others, like comet compositions, this book will speed the process. Of course, for anyone who has a suspect memory and wants a quick verification of an astronomical term, this book will do just fine.

One thing, this is the second edition. Ridpath mentions he enlisted the assistance of many specialists to review entries. Presumably this has increased the quality. However, I’m unable to make any comparison to the first edition, as I’m without a copy.

Ready fingertips grab for references whenever questions arise. Astronomy has its own broad set of particular terms. Ian Ridpath’s book, A Dictionary of Astronomy is ready to be of service when those fingers want to go walking. It’s one more valuable tool to keep people talking in harmony.

Read more reviews or purchase a copy online from Amazon.com.

Podcast: What is the Shape of the Universe?

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Some of the biggest questions in the universe depend on its shape. Is it curved? Is it flat? Is it open? Those may not make that much sense to you, but in fact it’s very important for astronomers. So which is it? How do we know? How did we figure it out? Why does it matter?

Click here to download the episode

What is the shape of the Universe? – Show notes and transcript

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

Measure Light Pollution and Help Save Our Dark Skies

It’s a stunning photo… And one we all recognize. At this point in time, more than half of the Earth’s population lives in or near a city and the results shine clearly from space. The crime is not energy consumption, over-population or even global warming. It’s the loss of one of our greatest natural resources… The starry night sky.

Light pollution effects more than just our ability to see the stars at night. Take a walk along the coastlines. It may be hard to believe, but hatching sea turtles aren’t able to get their bearings due to beachfront lighting. Even the aquatic ecosystems are effected! But it’s not just at the waters edge. Birds find it difficult to make
nesting choices and many species have difficulty breeding under over-lighted conditions. Can you imagine how much light changes disturb the habits of nocturnal animals and night-loving plants? Just as important and the Sun shining its life giving light on the Earth, so we are balanced by darkness.

I’m not hear to preach to you about light pollution. Outdoor lighting is used for many reasons, like security, sporting events and even advertising. However, by making just a few small changes – intelligent choices – on how we use that light we can help to preserve the stars for generations to come. You can learn more just by visiting the International Dark Sky Association and taking a few minutes to read.

Right now, you can do science a favour just by taking a few minutes out of your evening and having a look at the night sky from your location. It’s just as easy as finding Orion and counting the stars you see! In a effort to collection information from people the world over, GLOBE (Global Learning and Observations to Benefit the Environment) is asking for your help. It’s a great way for teachers, students, parents and even people just like you and me to participate in a real science effort. Visit the G.L.O.B.E. at Night pages for more information and join us in a world-wide effort!

Earth and Moon, As Seen From Mars

This picture was released a couple of days ago, but since it’s so special, it deserves a post on Universe Today. And besides, everyone secretly likes to look at pictures of themselves. And this is a picture of us: it’s the Earth and the moon, as seen from Mars. From the Mars Reconnaissance Orbiter, to be exact, and it was taken by the HiRISE Instrument on board, the High Resolution Imaging Science Experiment. That’s the same camera that gave us the images of the avalanche on Mars, so the capabilities of this instrument are quite spectacular. This image was snapped back in October 2007, from a distance of 142 million kilometers, and if you look closely, you can make out a few features on Earth.

The west coast outline of South America is at lower right on Earth, although the clouds are the dominant features. In fact, the clouds were so bright, compared with the Moon, that they almost completely saturated the filters on the HiRISE camera. The people working on HiRISE say this image required a fair amount of processing to make a such a nice-looking picture. Yes, I agree, we are looking quite nice.

The phase angle is 98 degrees, which means that less than half of the disks of the Earth and Moon have direct illumination from the sun; that’s the reason we only see about half of each object. The scientists working on HiRISE say they would be able to image the Earth and moon when they are fully illuminated, but only when they are on the opposite side of the sun from Mars. However, then the distance would be much greater and the image would show less detail.

At this distance, this HiRISE image has a scale of 142 km/pixel, giving the Earth diameter about 90 pixels and the Moon diameter 24 pixels.

And now, back to the target that HiRISE was originally designed for: Mars. Here’s a very colorful (and false color) image that highlights the different minerals in Nili Fossae on Mars, one of the potential landing sites for the Mars Science Laboratory rover. From the CRISM instrument, the on-board spectrometer, scientists can discern that this area on Mars contains iron and magnesium, minerals that also contain water.
Nili Fossae on Mars.  Image Credit: NASA/JPL/University of Arizona

Original News Source: HiRISE Web page

A One-Way, One-Person Mission to Mars

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Will humans ever really go to Mars? Let’s face it, the obstacles are quite daunting. Not only are there numerous, difficult, technical issues to overcome, but the political will and perseverance of any one nation to undertake such an arduous task just can’t be counted on. However, one former NASA engineer believes a human mission to Mars is quite doable, and such an event would unify the world as never before. But Jim McLane’s proposal includes a couple of major caveats: the trip to Mars should be one-way, and have a crew of only one person.

McLane worked at NASA for 21 years before leaving in 2007 to work for a private engineering firm. Being able to look from afar at NASA’s activities has given him a new perspective, he says.

But McLane was still at NASA when he originally had an idea for a one-way, one-person mission to Mars. He calls his proposal the “Spirit of the Lone Eagle,” in deference to Charles Lindbergh’s solo flight from New York to Paris in 1927.

McLane’s idea came from his acquaintance with a Russian cosmonaut. “I noticed the cosmonaut seemed to be a slightly different type of person than the American astronaut,” McLane said. “Cosmonauts are primarily pilots, and like test pilots, they are very focused on getting the job done. The current American astronauts are picked for things such as their speaking ability and social skills, and most of them have advanced degrees. But the cosmonaut struck me as an adventurous, get-things-done-type person, like our original astronauts back in the 1960’s.”

A return to the “get it done” attitude of the 1960’s and a goal of a manned landing within a short time frame, like Apollo, is the only way we’ll get to Mars, McLane believes. Additionally, a no-return, solo mission solves many of the problems currently facing a round-trip, multiple person crew.

“When we eliminate the need to launch off Mars, we remove the mission’s most daunting obstacle,” said McLane. And because of a small crew size, the spacecraft could be smaller and the need for consumables and supplies would be decreased, making the mission cheaper and less complicated.

While some might classify this as a suicide mission, McLane feels the concept is completely logical.

“There would be tremendous risk, yes,” said McLane, “but I don’t think that’s guaranteed any more than you would say climbing a mountain alone is a suicide mission. People do dangerous things all the time, and this would be something really unique, to go to Mars. I don’t think there would be any shortage of people willing to volunteer for the mission. Lindbergh was someone who was willing to risk everything because it was worth it. I don’t think it will be hard to find another Lindbergh to go to Mars. That will be the easiest part of this whole program.”

And like Apollo, such a mission would stimulate new technology and reinvigorate science. McLane feels a mission to Mars should be international in scope, encompassing contributions from multiple nations to represent a milestone for the whole human race.

Mars mission.  Image Credit:  NASA

“I think people have forgotten how exciting the Apollo program was, and this would bring that excitement back,” he said. “And it wasn’t just here in the US; the whole world was excited. This enthusiasm would be the greatest effect of a program that places a man on Mars, over and above anything else, whether it makes jobs, or stimulates the economy, or creates technology spinoffs. We’re all humans and the idea of sending one of our kind on a trip like that would be a wonderful adventure for the entire world. The whole world would get behind it.”

And the whole world would be watching, said McLane, so it wouldn’t be as if the lone astronaut would be completely by himself. “You would have constant communication,” he said. “The astronauts on the International Space Station have an army of people on earth keeping track of what they are doing. They really have no peace. Somebody is constantly planning and monitoring their activities. I don’t think being lonely will be much of a problem on a mission to Mars.”

Of course McLane’s hope is the solo astronaut would be joined by others shortly in the future. Orbital mechanics provides a desirable launch window from Earth to Mars every 26 months. “This person wouldn’t be there by himself for very long. It’s just returning home that would be impossible,” he said. Another option McLane has offered is a one-man and one-woman crew, possibly creating an Adam and Eve-type situation.

Unmanned landers would carry living accommodations, supplies and communication equipment to Mars’ surface before the human mission would even launch. The best location on Mars would be a low, sheltered area, perhaps at the bottom of a canyon, which would provide protection from radiation and weather, as well as the highest possible atmospheric pressure.

While technical issues abound for even the simplest human mission to Mars, McLane says technical issues didn’t deter the Apollo program, and they shouldn’t deter a mission to another planet.

“I can remember during the early days of the Apollo program, there were even many more technical issues than we face today in going to Mars,” said McLane. “People don’t realize that, or have forgotten that fact. Several things were tremendous unknowns back then, any one of which could have been a showstopper for a human moon landing.”

McLane said the early designers of the Apollo spacecraft gambled that in 3 or 4 years, high powered transistors and small guidance computers would be developed. That was the only way the spacecraft would be lightweight enough to land on the moon. “It was almost science fiction, but someone thought it could be done in just a few years, and sure enough the technology was perfected in time to make the mission possible,” he said.

James C. McLane.  Image Credit:  courtesy James McLane
Image: Jim McLane during his career at NASA.

While Apollo 11 astronaut Buzz Aldrin and noted author and physicist Paul Davies have also advocated a one-way trip to Mars, in our risk-averse society most people look askance at such an idea.

Even though explorers in the past traveled, for example, to the south or north pole, knowing they might never return, and thousands of immigrants moved to the US in the 18- and 1900’s, knowing they would never see their homeland again, the human psyche has seemingly changed enough that a one-way ticket off the planet is not acceptable. According to psychologist Molly Dooley from Springfield, IL, it might take a major crisis on Earth for humans to seriously consider such a mission. “Usually it’s the disenfranchised that are willing to take those kinds of risks,” she said. “When our present situation no longer works for us, we become more willing to take risks. The difference between the folks who are interested and those who aren’t is their attachment to their current situation.”

McLane says the main reason NASA hasn’t been able to focus on a human mission to Mars is simple: NASA doesn’t get nearly enough money. “This has been the case for many years,” he said. “They didn’t get enough money to fix problems with the shuttle, and they’ve always been chronically short of money. How we fund NASA is a big handicap, since every year, NASA has to go begging to Congress for funds and justify their budget. The Chinese space program, on the other hand, has an advantage in that they budget their projects in five-year increments. If we really want to go somewhere, we’ll have to change how NASA gets its money.”

But McLane thinks NASA is at fault for not even considering a one-way mission to Mars. “For over forty years they’ve studied all sorts of options, but haven’t admitted to ever looking at a one-way mission to Mars,” he said. “We shouldn’t be stuck on this rock forever. I believe it’s in our human nature to try to go somewhere else, and we’ve almost worn this world out. I think now is the time to reach out and go somewhere else to start with a clean slate. There is no reason not to try.”

Looking Down the Barrel of A Gamma Ray Burst

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A team of astronomers from the University of Sydney in Australia have been keeping an eye on a binary star system called Wolf-Rayet 104, located in the constellation Sagittarius. Wolf-Rayet stars are hot, gargantuan, older stars that are losing their masses, and astronomers consider these stars as ticking bombs: they could go supernova at any time within the next few hundred thousand years. That’s a relatively short fuse for astronomers. Images of this system from the Keck Telescope show an almost perfect spiral nebula formed by the two stars orbiting each other as they each blow off streams of gas. The way this system is spinning caught the eyes of these astronomers, who say Earth could be in the line of fire when the system blows.

Usually, a supernova explosion would be harmless at interstellar distances like the 8000 lightyears that this system lays from Earth, and it would just provide an impressive show for stargazers. But astronomers say the only way WR 104 could appear as an almost perfect spiral is if those of us on Earth were looking down the spin-axis of the system. Astronomer Peter Tuthill says that sometimes, supernovae focus their energy into a narrow beam of very destructive gamma-ray radiation along the axis of the system. A gamma-ray burst is a super-duper supernova that sometimes happens to massive stars, like the ones in WR 104.

As of now, no one can say for sure when the system will go supernova, or how massive and powerful the explosion might be. But the way these two stars are spinning about each other has astronomers thinking this system won’t provide just a run-of-the-mill explosion.

And an intensive gamma-ray burst at that distance could possibly be harmful to life on Earth.

But right now, this is all speculation, and more study on this system is needed before anyone needs to get worried. And this is all definitely very fascinating.

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“I used to appreciate this spiral just for its beautiful form, but now I can’t help a twinge of feeling that it is uncannily like looking down a rifle barrel,” says Dr. Peter Tuthill.

With a sequence of 11 different images, the astronomers were able to portray how the spiral nebula of this system is rotating in a circle every 8 months.

Original News Source: University of Sydney Press Release

HiRISE Captures Stunning Images of Mars Avalanches in Action

A Mars Avalanche, taken by NASAs HiRISE instrument on the Mars Reconnaisance Orbiter (Credit: NASA/HiRISE)

Magnificent images of avalanches of ice and rock in the northern polar regions of Mars have been captured by NASA Mars Reconnaissance Orbiter’s (MRO) High Resolution Imaging Science Experiment (HiRISE). These images are not of landslides that have happened in the past, they are actual Mars avalanches happening at the moment of observation. This rare event will be of tremendous value to Mars scientists currently analysing the effects of seasons on the landscape and will provide information on the geological activity of the planet…

This event occurred along a scarp (a distinct cliff, with a steep runoff) around the North Polar Region where surface ice can be found in large quantities. The HiRISE instrument was being used to assess seasonal changes around the North Pole when four areas of activity were seen along the scarp. HiRISE was witness to something more familiar on Earth than on Mars: avalanches.

This particular scarp is a high cliff over 700 m (2300 ft) tall and slopes at over 60 degrees. A mixture of ice, rock and dust can be seen, frozen in time, as it is plummeting down the slope, ejecting a plume of dust as the debris begins to settle on the gentle slope at the bottom of the cliff. The ejected cloud is approximately 180 meters across and extends about 190 meters beyond the base of the cliff. It is worth noting that the clouds are large 3D structures reaching into the Martian atmosphere and not 2D patterns on the surface (shadows from the plume can be seen to the lower left of the clouds of dust).

Mars polar region including scarp where avalanches were discovered - approximate locations of avalanches ringed (credit: NASA/JPL/UA)

The Martian landscape does not change very much over millions of years. Unlike the Earth, Mars does not have a thick, eroding atmosphere blasting away at the surface features. The lack of water also reduces these erosion effects. Mars also has very little geological activity as core reactions are thought to have slowed or even stopped – there is therefore very little tectonic movement, no major earthquakes and no evidence for present volcanic activity.

So what caused these avalanches? HiRISE scientists have some ideas:

  • Disappearance of carbon dioxide frost, dislodging rocks.
  • Expansion and contraction of ice due to seasonal temperature differences.
  • Small Mars-quakes.
  • A nearby meteorite impact.
  • Vibrations from other avalanches causing other avalanches along the scarp

Detail of the avalanches occurring along the scarp (credit: NASA/JPL/UA)

It seems most likely that the trigger may be down to seasonal changes. As the North Polar Region heats up (progressing toward summer), solid carbon dioxide (“dry ice”) may be subliming, weakening rocks around the edge of the cliff. The same could be said for the thermal expansion and contraction of water ice as the seasonal air temperature becomes warmer or cooler.

Whatever the cause, we are very lucky to have captured this event, the science collected from these observations will be critical to understanding how the Martian landscape can change very rapidly. The HiRISE instrument continues to return the most magnificently detailed images of the Red Planets surface, these observations of Mars avalanches will certainly go into the Mars Reconnaissance Orbiter’s Hall of Fame…

Source: HiRISE Project Site

Tracking Debris from US Spy Satellite USA 193; Delays to Rocket Launch

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The shoot down of US spy satellite USA 193 was condemned by some quarters of the international community. However, the fact remains, this was a resounding success for the US military. Observers of the operation to destroy the potentially dangerous satellite likened it to “trying to fire a missile through the eye of a needle”. After all, the dead satellite was orbiting at a height of about 250 km, and the satellite-killing missile was fired from a boat; assuring impact with an object the size of a small bus was never going to be easy. But the mission was a success and the satellite disintegrated into bits (no bigger than a football). Now the task of tracking the debris is under way, and the fallout from last months fireworks are impacting the scheduled launch of other space missions…

According to CelesTrak, there are 52 catalogued bits of USA 193 orbiting the Earth. The pieces range in altitude from 167 km (at the closest approach) to over 2,600 km (at apogee – the highest point of orbit) and they are being tracked with great accuracy (pictured above).
Plot showing the projected lifetime of the USA 193 space debris (credit: CelesTrak)
The 5,000 pound (2,300 kg) satellite apparently disintegrated into many small pieces of debris, each no bigger than the volume of a football (equivalent to a circle with a diameter of 20 cm). Anything smaller than 10 cm cannot be tracked with any degree of accuracy, so an analysis by CelesTrak (pictured left) shows the upper and lower bounds of debris that can be tracked and how long they are likely to stay in orbit.

As a rule, larger pieces of debris will remain in orbit for longer, whilst the smaller objects will have less momentum to stay above the Earths atmosphere. As can be seen, most of the debris can be expected to burn up through atmospheric re-entry within 30 days, but there is a massive difference in the lifetime of the remaining 10 cm debris when compared with the 20 cm debris. The remaining 5% of large chunks of satellite are projected to stay in orbit for 50 days longer than their smaller cousins.

Tracking these bits of debris is an arduous task, but the monitoring continues. The destruction of USA 193 has influenced the scheduled launch of rockets since February 20th, and disruption is likely to continue should these larger pieces of debris pass through spacecraft launch windows. The launch of a US National Reconnaissance Office NROL-28 reconnaissance satellite last Friday from Vandenberg Air Force Base in California, has been postponed for two weeks until the USA 193 debris poses no threat of collision.

Universe Today coverage of the demise of satellite USA 193:

Original Source: CelesTrak