Friday, February 20, 2015

Who Speaks for Earth? The Controversy over Interstellar Messaging

Who Speaks for Earth? The Controversy over Interstellar Messaging:



War of the Worlds


The prospect of alien invasion has sent shivers down the spines of science fiction fans ever since H. G. Wells published his classic “The War of the Worlds” in 1897. Drawing on the science of his times, Wells envisioned Mars as an arid dying world, whose inhabitants coveted the lush blue Earth. Although opponents of METI seldom explicitly invoke the spectre of alien invasion, some do believe that we must take into account the possibility that extraterrestrials may mean to harm us. The illustration from Well’s novel shows a Martian fighting machine attacking the British warship HMS Thunderchild.
(credit: Henrique Alvim Correa, 1906, for the novel “The War of the Worlds”)
Should we beam messages into deep space, announcing our presence to any extraterrestrial civilizations that might be out there? Or, should we just listen? Since the beginnings of the modern Search for Extraterrestrial Intelligence (SETI), radio astronomers have, for the most part, followed the listening strategy.


In 1999, that consensus was shattered. Without consulting with other members of the community of scientists involved in SETI, a team of radio astronomers at the Evpatoria Radar Telescope in Crimea, led by Alexander Zaitsev, beamed an interstellar message called ‘Cosmic Call’ to four nearby sun-like stars. The project was funded by an American company called Team Encounter and used proceeds obtained by allowing members of the general public to submit text and images for the message in exchange for a fee.


Similar additional transmissions were made from Evpatoria in 2001, 2003, and 2008. In all, transmissions were sent towards twenty stars within less than 100 light years of the sun. The new strategy was called Messaging to Extraterrestrial Intelligence (METI). Although Zaitsev was not the first to transmit an interstellar message, he and his associates where the first to systematically broadcast to nearby stars. The 70 meter radar telescope at Evpatoria is the second largest radar telescope in the world.

In the wake of the Evpatoria transmissions a number of smaller former NASA tracking and research stations collected revenue by making METI transmissions as commercially funded publicity stunts. These included a transmission in the fictional Klingon language from Star Trek to promote the premier of an opera, a Dorito’s commercial, and the entirety of the 2008 remake of the classic science fiction movie “The Day the Earth Stood Still”. The specifications of these commercial signals have not been made public, but they were most likely much too faint to be detectable at interstellar distances with instruments comparable to those possessed by humans.

Zaitsev’s actions stirred divisive controversy among the community of scientists and scholars concerned with the field. The two sides of the debate faced off in a recent special issue of the Journal of the British Interplanetary Society, resulting from a live debate sponsored in 2010 by the Royal Society at Buckinghamshire, north of London, England.



Alexander L. Zaitsev- Chief scientist of the Russian Academy of Science’s Institute of Radio Engineering and Electronics, and head of the group that transmitted interstellar messages using the Evpatoria Planetary Radar telescope. (credit: Rumin)


Alexander L. Zaitsev- Chief scientist of the Russian Academy of Science’s Institute of Radio Engineering and Electronics, and head of the group that transmitted interstellar messages using the Evpatoria Planetary Radar telescope. (credit: Rumin)
Modern SETI got its start in 1959, when astrophysicists Giuseppe Cocconi and Phillip Morrison published a paper in the prestigious scientific journal Nature, in which they showed that the radio telescopes of the time were capable of receiving signals transmitted by similar counterparts at the distances of nearby stars. Just months later, radio astronomer Frank Drake turned an 85 foot radio telescope dish towards two nearby sun-like stars and conducted Project Ozma, the first SETI listening experiment. Morrison, Drake, and the young Carl Sagan supposed that extraterrestrial civilizations would “do the heavy lifting” of establishing powerful and expensive radio beacons announcing their presence. Humans, as cosmic newcomers that had just invented radio telescopes, should search and listen. There was no need to take the risk, however small, of revealing our presence to potentially hostile aliens.

Drake and Sagan did indulge in one seeming exception to their own moratorium. In 1974, the pair devised a brief 1679 bit message that was transmitted from the giant Arecibo Radar Telescope in Puerto Rico. But the transmission was not a serious attempt at interstellar messaging. By intent, it was aimed at a vastly distant star cluster 25,000 light years away. It merely served to demonstrate the new capabilities of the telescope at a rededication ceremony after a major upgrade.

In the 1980’s and 90’s SETI researchers and scholars sought to formulate a set of informal rules for the conduct of their research. The First SETI Protocol specified that any reply to a confirmed alien message must be preceded by international consultations, and an agreement on the content of the reply. It was silent on the issue of transmissions sent prior to the discovery of an extraterrestrial signal.



David Brin- Space scientist, futurist consultant, and science fiction writer (credit: Glogger)


David Brin- Space scientist, futurist consultant, and science fiction writer (credit: Glogger)
A Second SETI Protocol was to have addressed the issue, but, somewhere along the way, critics charge, something went wrong. David Brin, a space scientist, futurist consultant, and science fiction writer was a participant in the protocol discussion. He charged that “collegial discussion started falling apart” and “drastic alterations of earlier consensus agreements were rubber-stamped, with the blatant goal of removing all obstacles from the path of those pursuing METI”.


Brin accuses “the core community that clusters around the SETI Institute in Silicon Valley, California”, including astronomers Jill Tartar and Seth Shostak of “running interference for and enabling others around the world- such as Russian radio astronomer Dr. Alexander Zaitsev” to engage in METI efforts. Shostak denies this, and claims he simply sees no clear criteria for regulating such transmissions.

Brin, along with Michael A. G. Michaud, a former U.S. Foreign Service Officer and diplomat who chaired the committee that formulated the first and second protocol, and John Billingham, the former head of NASA’s short lived SETI effort, resigned their memberships in SETI related committees to protest the alterations to the second protocol.

The founders of SETI felt that extraterrestrial intelligence was likely to be benign. Carl Sagan speculated that extraterrestrial civilizations (ETCs) older than ours would, under the pressure of necessity, become peaceful and environmentally responsible, because those that didn’t would self-destruct. Extraterrestrials, they supposed, would engage in interstellar messaging because of a wish to share their knowledge and learn from others. They supposed that ETCs would establish powerful omnidirectional beacons in order to assist others in finding them and joining a communications network that might span the galaxy. Most SETI searches have been optimized for detecting such steady constantly transmitting beacons.

Over the fifty years since the beginnings of SETI, searches have been sporadic and plagued with constant funding problems. The space of possible directions, frequencies, and coding strategies has only barely been sampled so far. Still, David Brin contends that whole swaths of possibilities have been eliminated “including gaudy tutorial beacons that advanced ETCs would supposedly erect, blaring helpful insights to aid all newcomers along the rocky paths”. The absence of obvious, easily detectable evidence of extraterrestrial intelligence has led some to speak of the “Great Silence”. Something, Brin notes, “has kept the prevalence and visibility of ETCs below our threshold of observation”. If alien civilizations are being quiet, could it be that they know something that we don’t know about some danger?

Alexander Zaitsev thinks that such fears are unfounded, but that other civilizations might suffer from the same reluctance to transmit that he sees as plaguing humanity. Humanity, he thinks, should break the silence by beaming messages to its possible neighbors. He compares the current state of humanity to that of a man trapped in a one-man prison cell. “We”, he writes “do not want to live in a cocoon, in a ‘one –man cell’, without any rights to send a message outside, because such a life is not INTERESTING! Civilizations forced to hide and tremble because of farfetched fears are doomed to extinction”. He notes that in the ‘60’s astronomer Sebastian von Hoerner speculated that civilizations that don’t engage in interstellar communication eventually decline through “loss of interest”.

METI critics maintain that questions of whether or not to send powerful, targeted, narrowly beamed interstellar transmissions, and of what the content of those transmissions should be needs to be the subject of broad international and public discussion. Until such discussion has taken place, they want a temporary moratorium on such transmissions.



Seth Shostak- SETI Institute radio astronomer (credit: B D Engler)


Seth Shostak- SETI Institute radio astronomer (credit: B D Engler)
On the other hand, SETI Institute radio astronomer Seth Shostak thinks that such deliberations would be pointless. Signals already leak into space from radio and television broadcasting, and from civilian and military radar. Although these signals are too faint to be detected at interstellar distances with current human technology, Shostak contends that with the rapid growth in radio telescope technology, ETCs with technology even a few centuries in advance of ours could detect this radio leakage. Billingham and Benford counter that to collect enough energy to tune in on such leakage; an antenna with a surface area of more than 20,000 square kilometers would be needed. This is larger than the city of Chicago. If humans tried to construct such a telescope with current technology it would cost 60 trillion dollars.


Shostak argues that exotic possibilities might be available to a very technologically advanced society. If a telescope were placed at a distance of 550 times the Earth’s distance from the sun, it would be in a position to use the sun’s gravitational field as a gigantic lens. This would give it an effective collecting area vastly larger than the city of Chicago, for free. If advanced extraterrestrials made use of their star’s gravitational field in this way, Shostak maintains “that would give them the capacity to observe many varieties of terrestrial transmissions, and in the optical they would have adequate sensitivity to pick up the glow of street lamps”. Even Brin conceded that this idea was “intriguing”.

Civilizations in a position to do us potential harm through interstellar travel, Shostak contends, would necessarily be technologically advanced enough to have such capabilities. “We cannot pretend that our present level of activity with respect to broadcasting or radar usage is ‘safe’. If danger exists, we’re already vulnerable” he concludes. With no clear means to say what extraterrestrials can or can’t detect, Shostak feels the SETI community has nothing concrete to contribute to the regulation of radio transmissions.

Could extraterrestrials harm us? In 1897 H. G. Wells published his science fiction classic “The War of the Worlds” in which Earth was invaded by Martians fleeing their arid, dying world. Besides being scientifically plausible in terms of its times, Wells’ novel had a political message. An opponent of British colonialism, he wanted his countrymen to imagine what imperialism was like from the other side. Tales of alien invasion have been a staple of science fiction ever since. Some still regard European colonialism as a possible model for how extraterrestrials might treat humanity. The eminent physicist Steven Hawking thinks very advanced civilizations might have mastered interstellar travel. Hawking warned that “If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans”.

Though dismissing Hawking’s fears of alien invasion as an “unlikely speculation”, David Brin notes that interstellar travel by small automated probes is quite feasible, and that such a probe could potentially do harm to us in many ways. It might, for example, steer an asteroid onto a collision course with Earth. A relatively small projectile traveling at one tenth the speed of light could wreak terrible damage by simply colliding with our planet. “The list of unlikely, but physically quite possible scenarios is very long” he warns.

Diplomat Michael Michaud warns that “We can all understand the frustration of not finding any signals after fifty years of intermittent searching” but “Impatience with the search is not a sufficient justification for introducing a new level of potential risk for our entire species”.

METI critics David Brin, James Benford, and James Billingham think that the current lack of results from SETI warrants a different sort of response than METI. They call for a reassessment of the search strategy. From the outset, SETI researchers have assumed that extraterrestrials will use steady beacons transmitting constantly in all directions to attract our attention. Recent studies of interstellar radio propagation and the economics of signaling show that such a beacon, which would need to operate on a vast timescale, is not an efficient way to signal.

Instead, an alien civilization might compile a list of potentially habitable worlds in its neighborhood and train a narrowly beamed signal on each member of the list in succession. Such brief “ping” messages might be repeated, in sequence, once a year, once a decade, or once a millennium. Benford and Billingham note that most SETI searches would miss this sort of signal.

The SETI Institute’s Allen telescope array, for example, is designed to target narrow patches of sky (such as the space around a sun-like star) and search those patches in sequence, for the presence of continuously transmitting beacons. It would miss a transient “ping” signal, because it would be unlikely to be looking in the right place at the right time. Ironically, the Evpatoria messages, transmitted for less than a day, are examples of such transient signals.

Benford and Billingham propose the construction of a new radio telescope array designed to constantly monitor the galactic plane (where stars are most abundant) for transient signals. Such a telescope array, they estimate, would cost about 12 million dollars, whereas a serious, sustained METI program would cost billions.

The METI controversy continues. On February 13, the two camps debated each other at the American Association for the Advancement of Science conference in San Jose, California. At that conference David Brin commented “It’s an area where opinion rules, and everyone has a fierce opinion”. In the wake of the meeting a group of 28 scientists, scholars, and business leaders issued a statement that “We feel the decision whether or not to transmit must be based on a worldwide consensus, and not a decision based on the wishes of a few individuals with access to powerful communications equipment”.

References and Further Reading:

J. Benford, J. Billingham, D. Brin, S. Dumas, M. Michaud, S. Shostak, A. Zaitsev, (2014) Messaging to Extraterrestrial Intelligence special section, Journal of the British Interplanetary Society, 67, p. 5-43.

The SETI Institute

D. Brin, Shouting at the cosmos: How SETI has taken a worrisome turn into dangerous territory.

F. Cain (2013) How could we find aliens? The search for extraterrestrial intelligence (SETI), Universe Today.

E. Hand (2015), Researchers call for interstellar messages to alien civilizations, Science Insider, Science Magazine.

P. Patton (2014) Communicating across the cosmos, Part 1: Shouting into the darkness, Part 2: Petabytes from the Stars, Part 3: Bridging the Vast Gulf, Part 4: Quest for a Rosetta Stone, Universe Today.



About 

Paul Patton is a freelance science writer. He holds a Bachelor's degree in physics from the University of Wisconsin Green Bay, a Master's degree in the history and philosophy of science from Indiana University, and a Doctorate in neuroscience from the University of Chicago. He has been interested in space, astronomy, and extraterrestrial life since early childhood.

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Learn About Venus, The Hothouse Planet Near Earth

Learn About Venus, The Hothouse Planet Near Earth:



False color radar topographical map of Venus provided by Magellan. Credit: Magellan Team/JPL/NASA


False color radar topographical map of Venus provided by Magellan. Credit: Magellan Team/JPL/NASA
Venus was once considered a twin to Earth, as it’s roughly the same size and is relatively close to our planet. But once astronomers looked at it seriously in the past half-century or so, a lot of contrasts emerged. The biggest one — Venus is actually a hothouse planet with a runaway greenhouse effect, making it inhospitable to life as we know it. Here are some more interesting facts about Venus.

1. Venus’ atmosphere killed spacecraft dead very quickly.

You sure don’t want to hang around on Venus’ surface. The pressure there is so great that spacecraft need shielding to survive. The atmosphere is made up of carbon dioxide with bits of sulfuric acid, NASA says, which is deadly to humans. And if that’s not bad enough, the temperature at the surface is higher than 470 degrees Celsius (880 degrees Fahrenheit). The Soviet Venera probes that ventured to the surface decades ago didn’t last more than two hours.

2. But conditions are more temperate higher in the atmosphere.

While you still couldn’t breathe the atmosphere high above Venus’ surface, at about  50 kilometers (31 miles) you’ll at least find the same pressure and atmosphere density as that of Earth. A very preliminary NASA study suggests that at some point, we could deploy airships for humans to explore Venus. And the backers suggest it may be more efficient to go to Venus than to Mars, with one large reason being that Venus is closer to Earth.



Artist's conception of the High Altitude Venus Operational Concept (HAVOC) mission, a far-out concept being developed by NASA, approaching the planet. Credit: NASA Langley Research Center/YouTube (screenshot)


Artist’s conception of the High Altitude Venus Operational Concept (HAVOC) mission, a far-out concept being developed by NASA, approaching the planet. Credit: NASA Langley Research Center/YouTube (screenshot)
3. Venus is so bright it is sometimes mistaken for a UFO.

The planet is completely socked in by cloud, which makes it extremely reflective to observers looking at the sky on Earth. Its brightness is between -3.8 and -4.8 magnitude, which makes it brighter than the stars in the sky. In fact, it’s so bright that you can see it go through phases in a telescope — and it can cast shadows! So that remarkable appearance can confuse people not familiar with Venus in the sky, leading to reports of airplanes or UFOs.

4. And those clouds mean you can’t see the surface.

If you were to look at Venus with your eyes, you wouldn’t be able to see its surface. That’s because the clouds are so thick that they obscure what is below. NASA got around that problem when it sent the Magellan probe to Venus for exploration in the 1990s. The probe orbited the planet and got a complete surface picture using radar.



Artist's impression of the surface of Venus Credit: ESA/AOES


Artist’s impression of the surface of Venus Credit: ESA/AOES
5. Venus has volcanoes and a fresh face.

Venus has fresh lava flows on its surface, which implies that volcanoes erupted anywhere from the past few hundred years to the past three million years. What this means is there are few impact craters on the surface, likely because the lava flowed over them and filled them in. While scientists believe the volcanoes are responsible, the larger question is how frequently this occurs.

6. Venus has a bizarre rotation.

Venus not only rotates backwards compared to the other planets, but it rotates very slowly. In fact, a day on Venus (243 days) lasts longer than it takes the planet to orbit around the Sun (225 days). Even more strangely, the rotation appears to be slowing down; Venus is turning 6.5 minutes more slowly in 2014 than in the early 1990s. One theory for the change could be the planet’s weather; its thick atmosphere may grind against the surface and slow down the rotation.



Artist's conception of Venus Express doing an aerobraking maneuver in the atmosphere in 2014. Credit: ESA–C. Carreau


Artist’s conception of Venus Express doing an aerobraking maneuver in the atmosphere in 2014. Credit: ESA–C. Carreau
7. Venus has no moons or rings

The two planets closest to the Sun have no rings or moons, which puts Venus in the company of only one other world: Mercury. Every other planet in the Solar System has one or the other, or in many cases both! Why this is is a mystery to scientists, but they are doing as much comparison of different planets as possible to understand what’s going on.

8. Venus appears to be a spot where spacecraft go to extremes.

We briefly mentioned the Venera probes that landed on the surface, but that’s not the only unusual spacecraft activity at Venus. In 2014, the European Space Agency put an orbiter – that’s right, a spacecraft not designed to survive the atmosphere — into the upper parts of Venus’ dense atmosphere. Venus Express did indeed survive the encounter (before it ran out of gas), with the goal of providing more information about how the atmosphere looks at high altitudes. This could help with landings in the future.



About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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Astrophotos: The February 2015 ‘Black’ Moon

Astrophotos: The February 2015 ‘Black’ Moon:



The February 2015 new Moon over Antelope Valley, California. Credit and copyright: Gavin Heffernan.


The February 2015 new Moon over Antelope Valley, California. Credit and copyright: Gavin Heffernan.
As our David Dickinson noted in his recent article, a new term is “creeping into the popular astronomical vernacular: that of a ‘Black Moon’.” This is the New Moon version of a Blue Moon, and is either:

  1. A month missing a Full or New Moon… this can only occur in February, as the lunar synodic period from like phase to phase is 29.5 days long. This last occurred in 2014 and will next occur in 2018.
  2. The second New Moon in a month with two. This can happen in any calendar month except February.
  3. And now for the most convoluted definition: the third New Moon in an astronomical season with four.
The February 18th New Moon met the requirements expressed in rule 3. The fourth New Moon of the season falls on March 20th, just 13 hours before the northward equinox on the same date.

But no matter what the occasion, there are always astrophotographers out to grab pictures, and here are some shared with Universe Today via email and on our Flickr page.




The sliver of the February 2015 new 'black' Moon. Credit and copyright: Héctor Barrios.


The sliver of the February 2015 new ‘black’ Moon. Credit and copyright: Héctor Barrios.


The less than 24-hour old Moon on February 19, 2015, as seen from Toronto, Canada. Credit and copyright: Michael Watson.


The less than 24-hour old Moon on February 19, 2015, as seen from Toronto, Canada. Credit and copyright: Michael Watson.


The Moon, Mars and Venus. Credit and copyright: Neil Ghosh.


The Moon, Mars and Venus. Credit and copyright: Neil Ghosh.
And remember, tonight you can see a close conjunction of the Moon, Venus and Mars. Here’s how you can photograph the event, and make sure to share your photos with Universe Today!

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How Can Space Travel Faster Than The Speed Of Light?

How Can Space Travel Faster Than The Speed Of Light?:



What would you see at the speed of light/


Light speed is often spoken of as a cosmic speed limit… but not everything plays by these rules. In fact, space itself can expand faster than a photon could ever hope to travel.
Cosmologists are intellectual time travelers. Looking back over billions of years, these scientists are able to trace the evolution of our Universe in astonishing detail. 13.8 billion years ago, the Big Bang occurred. Fractions of a second later, the fledgling Universe expanded exponentially during an incredibly brief period of time called inflation. Over the ensuing eons, our cosmos has grown to such an enormous size that we can no longer see the other side of it.

But how can this be? If light’s velocity marks a cosmic speed limit, how can there possibly be regions of spacetime whose photons are forever out of our reach? And even if there are, how do we know that they exist at all?

The Expanding Universe

Like everything else in physics, our Universe strives to exist in the lowest possible energy state possible. But around 10-36 seconds after the Big Bang, inflationary cosmologists believe that the cosmos found itself resting instead at a “false vacuum energy” – a low-point that wasn’t really a low-point. Seeking the true nadir of vacuum energy, over a minute fraction of a moment, the Universe is thought to have ballooned by a factor of 1050.

Since that time, our Universe has continued to expand, but at a much slower pace. We see evidence of this expansion in the light from distant objects. As photons emitted by a star or galaxy propagate across the Universe, the stretching of space causes them to lose energy. Once the photons reach us, their wavelengths have been redshifted in accordance with the distance they have traveled.



Two sources of redshift: Doppler and cosmological expansion; modeled after Koupelis & Kuhn. Credit: Brews Ohare.


Two sources of redshift: Doppler and cosmological expansion; modeled after Koupelis & Kuhn. Bottom: Detectors catch the light that is emitted by a central star. This light is stretched, or redshifted, as space expands in between. Credit: Brews Ohare.
This is why cosmologists speak of redshift as a function of distance in both space and time. The light from these distant objects has been traveling for so long that, when we finally see it, we are seeing the objects as they were billions of years ago.

The Hubble Volume

Redshifted light allows us to see objects like galaxies as they existed in the distant past; but we cannot see all events that occurred in our Universe during its history. Because our cosmos is expanding, the light from some objects is simply too far away for us ever to see.

The physics of that boundary rely, in part, on a chunk of surrounding spacetime called the Hubble volume. Here on Earth, we define the Hubble volume by measuring something called the Hubble parameter (H0), a value that relates the apparent recession speed of distant objects to their redshift. It was first calculated in 1929, when Edwin Hubble discovered that faraway galaxies appeared to be moving away from us at a rate that was proportional to the redshift of their light.



Fit of redshift velocities to Hubble's law. Credit: Brews Ohare


Fit of redshift velocities to Hubble’s law. Credit: Brews Ohare
Dividing the speed of light by H0, we get the Hubble volume. This spherical bubble encloses a region where all objects move away from a central observer at speeds less than the speed of light. Correspondingly, all objects outside of the Hubble volume move away from the center faster than the speed of light.

Yes, “faster than the speed of light.” How is this possible?

The Magic of Relativity

The answer has to do with the difference between special relativity and general relativity. Special relativity requires what is called an “inertial reference frame” – more simply, a backdrop. According to this theory, the speed of light is the same when compared in all inertial reference frames. Whether an observer is sitting still on a park bench on planet Earth or zooming past Neptune in a futuristic high-velocity rocketship, the speed of light is always the same. A photon always travels away from the observer at 300,000,000 meters per second, and he or she will never catch up.

General relativity, however, describes the fabric of spacetime itself. In this theory, there is no inertial reference frame. Spacetime is not expanding with respect to anything outside of itself, so the the speed of light as a limit on its velocity doesn’t apply. Yes, galaxies outside of our Hubble sphere are receding from us faster than the speed of light. But the galaxies themselves aren’t breaking any cosmic speed limits. To an observer within one of those galaxies, nothing violates special relativity at all. It is the space in between us and those galaxies that is rapidly proliferating and stretching exponentially.

The Observable Universe

Now for the next bombshell: The Hubble volume is not the same thing as the observable Universe.

To understand this, consider that as the Universe gets older, distant light has more time to reach our detectors here on Earth. We can see objects that have accelerated beyond our current Hubble volume because the light we see today was emitted when they were within it.

Strictly speaking, our observable Universe coincides with something called the particle horizon. The particle horizon marks the distance to the farthest light that we can possibly see at this moment in time – photons that have had enough time to either remain within, or catch up to, our gently expanding Hubble sphere.

And just what is this distance? A little more than 46 billion light years in every direction – giving our observable Universe a diameter of approximately 93 billion light years, or more than 500 billion trillion miles.



The observable - or inferrable universe. This may just be a small component of the whole ball game.


The observable universe, more technically known as the particle horizon.
(A quick note: the particle horizon is not the same thing as the cosmological event horizon. The particle horizon encompasses all the events in the past that we can currently see. The cosmological event horizon, on the other hand, defines a distance within which a future observer will be able to see the then-ancient light our little corner of spacetime is emitting today.

In other words, the particle horizon deals with the distance to past objects whose ancient light that we can see today; the cosmological event horizon deals with the distance that our present-day light that will be able to travel as faraway regions of the Universe accelerate away from us.)

Dark Energy

Thanks to the expansion of the Universe, there are regions of the cosmos that we will never see, even if we could wait an infinite amount of time for their light to reach us. But what about those areas just beyond the reaches of our present-day Hubble volume? If that sphere is also expanding, will we ever be able to see those boundary objects?

This depends on which region is expanding faster – the Hubble volume or the parts of the Universe just outside of it. And the answer to that question depends on two things: 1) whether H0 is increasing or decreasing, and 2) whether the Universe is accelerating or decelerating. These two rates are intimately related, but they are not the same.

In fact, cosmologists believe that we are actually living at a time when His decreasing; but because of dark energy, the velocity of the Universe’s expansion is increasing.

That may sound counterintuitive, but as long as Hdecreases at a slower rate than that at which the Universe’s expansion velocity is increasing, the overall movement of galaxies away from us still occurs at an accelerated pace. And at this moment in time, cosmologists believe that the Universe’s expansion will outpace the more modest growth of the Hubble volume.

So even though our Hubble volume is expanding, the influence of dark energy appears to provide a hard limit to the ever-increasing observable Universe.

Our Earthly Limitations



cosmology tapestry


Cosmologists seem to have a good handle on deep questions like what our observable Universe will someday look like and how the expansion of the cosmos will change. But ultimately, scientists can only theorize the answers to questions about the future based on their present-day understanding of the Universe. Cosmological timescales are so unimaginably long that it is impossible to say much of anything concrete about how the Universe will behave in the future. Today’s models fit the current data remarkably well, but the truth is that none of us will live long enough to see whether the predictions truly match all of the outcomes.

Disappointing? Sure. But totally worth the effort to help our puny brains consider such mind-bloggling science – a reality that, as usual, is just plain stranger than fiction.



About 

Vanessa earned her bachelor's degree in Astronomy and Physics in 2009 from Wheaton College in Massachusetts. Her credits in astronomy include observing and analyzing eclipsing binary star systems and taking a walk on the theory side as a NSF REU intern, investigating the expansion of the Universe by analyzing its traces in observations of type 1a supernovae. In her spare time she enjoys writing about astrophysics, cosmology, biology, and medicine, making delicious vegetarian meals, taking adventures with her husband and/or Nikon D50, and saving the world.

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How to Photograph Tonight’s Spectacular Triple-Play Conjunction

How to Photograph Tonight’s Spectacular Triple-Play Conjunction:



Last night's one-day-old Moon photographed a half-hour after sunset. Details: handheld camera ISO 400, f/2.8, 1/15". Credit: Bob King


Last night’s one-day-old Moon photographed a half-hour after sunset. Details: handheld camera, 200mm lens, ISO 400, f/2.8, 1/15″. Credit: Bob King
Tonight the thin, 2-day-old crescent Moon will join Venus and Mars in the western sky at dusk for one of the most striking conjunctions of the year. The otherworldly trio will fit neatly with a circle about 1.5° wide or just three times the diameter of the full moon. No question, this will catch a lot of eyes around the world. Why not take a picture and share it with your friends? Here are a few tips to do just that.



Moon, Mars and Venus around 6:45 p.m. (CST) on Feb. 20 in the western sky. Be sure to look for the darkly-lit part of the moon illuminated by sunlight reflecting off Earth called earthshine. It’s a beautiful sight in binoculars. Source: Stellarium


Moon, Mars and Venus around 6:45 p.m. (CST) on Feb. 20 in the western sky. Be sure to look for the darkly-lit part of the moon illuminated by sunlight reflecting off Earth called earthshine. Source: Stellarium, author
You won’t need much for an easy snapshot. In bright twilight, point your mobile phone toward the Moon and tap off a few shots, taking care not to touch the screen too hard lest you shake the phone and blur the image. The phone’s autoexposure and autofocus settings should be adequate to capture both the Moon and Venus. Mars is fainter and may only show if you can steady your phone against something to allow for a longer exposure without blurring. Assuming you use your phone in its default wide view, the Moon, Venus and Mars will form a tight, small group in a larger scene.



Last night, Feb. 19, Venus and Mars were 1 degree apart. Tonight they'll be even closer at just over 1/2° with the Moon a degree or so to their right. Credit: Bob King


Last night, Feb. 19, Venus and Mars were 1°apart. Tonight they’ll be even closer at just over 1/2° with the Moon about 1° to their right. Details: 65 minutes after sunset (mid-twilight), camera on tripod, 35mm lens at f/2.8, ISO 400 and 6 second exposure. Credit: Bob King
Phones provide the highest resolution in their wide setting. If you zoom in, the Moon will be bigger but resolution or sharpness will suffer. Someday phones will be as good as digital single lens reflex cameras (DSLRs) but until then, you’ll need one of these or their cousins, the point-and-shoot cameras, to get the best images of astronomical objects.

You’ll also need a tripod to keep the camera still and stable during the longer exposures you’ll need during the optimum time for photography which begins about 30 minutes after sunset. That’s when your photos will capture all three objects without overexposing the Moon and making it look washed-out. Ideally, you want to see the bright crescent contrasting with the dim glow of the earthshine.



Venus and Mars photographed in mid-twilight with a 100mm telephoto lens at f/2.8. To prevent trailing of the planets, I cut the exposure in half to 4 seconds and increased the camera's ISO to 800. Credit: Bob King


Venus and Mars photographed in mid-twilight with a 100mm telephoto lens at f/2.8. To prevent trailing of the planets, I cut the exposure in half to 4 seconds and increased the camera’s ISO to 800. Credit: Bob King
Lucky for us, the Moon’s sharp form makes an ideal target for the camera’s autofocus. Frame an attractive landscape or ask a friend to stand in the foreground. Set your lens to its widest open setting (usually f/2.8-3.5) and the ISO (your camera’s sensitivity to light) to 800. The higher the ISO, the shorter the exposure you can use to capture an image, but high ISOs introduce unwanted noise and graininess. 800’s a good compromise. If you can manually set your exposure, start at 4 seconds.

Compose your photo and then focus on the Moon and gently press the shutter button. Check the image on the back screen. Are you on target or is it too dark? If so, double the time. If too bright, half it. As the sky gets darker, you’ll need to gradually increase your exposure. That’s when the Moon will start to wash out and the beautiful deep blue sky turn black or the color of your local light pollution. Around here, that’s pinkish-orange. I’ve got lots of orange sky photos to prove it!



The key to good photos in twilight is balancing the different types of lighting - dusk, the sunlit crescent, the earth-lit portion and the planets. Shoot pictures at a variety of exposures between about 30-60 minutes after sunset when the western sky is still aglow but the Moon is bright and obvious. Credit: Bob King


Mercury and the Moon on Jan. 31, 2014. Besides finding a scene you like, the key to good photos in twilight is balancing the different types of lighting – dusk, the sunlit crescent, the earth-lit outline and the planets. Shoot pictures at a variety of exposures starting about 35 minutes after sunset when the western sky is still aglow but the Moon is bright and obvious. Credit: Bob King
All told, you can use a mobile phone to shoot from about 25-40 minutes after sunset and a DSLR from 25 minutes to 75 minutes after. If you’re shooting with a standard 24-35mm lens, keep your exposures under 20 seconds or the Moon and planets will start to streak or trail. The Rule of 500 is a great way to remember how long a time exposure you can make with any lens before celestial objects start trailing. So, 500/24mm = 20.8 seconds and 500/200mm (telephoto) = 2.5 seconds. That means if you plan to shoot the conjunction with a longer lens, you’ll need to up your ISO to 1600 or even 3200 in late twilight to get a tack-sharp, motionless photo.



I screwed this photo up of the Moon, Jupiter and Mars by overexposing the sunlit crescent. Credit: Bob King


I screwed this photo up of the Moon, Jupiter and Mars by overexposing the sunlit crescent. It’s all part of learning the ropes, a task made much easier nowadays by simply checking the view screen of your camera and trying a different exposure. Credit: Bob King
Telephoto images are a bit more challenging, but they increase the size of the pretty trio within the scene. When shooting telephoto images (even wide ones if you’re fussy), shoot them on self-timer. That’s the setting everyone used before the selfie took the world by storm. Most timers are pre-set to 10 seconds. You press it and the camera counts down 10 seconds before automatically tripping the shutter, allowing you time to put yourself in a group photo.

In astrophotography, using the self-timer assures you’re going to get a vibration-free photo. If it’s cold out and you’re shooting with a telephoto, vibration from your finger pressing the shutter button can jiggle the image.

Good luck tonight and clear skies! If you have any questions, please ask.



About 

I'm a long-time amateur astronomer and member of the American Association of Variable Star Observers (AAVSO). My observing passions include everything from auroras to Z Cam stars. Every day the universe offers up something both beautiful and thought-provoking. I also write a daily astronomy blog called Astro Bob.

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WOW Fake Winter Solstice Image is Fake. But Cool

Fake Winter Solstice Image is Fake. But Cool.:

\"Hideaway\" by artist Inga Nielsen


Editor Note: We originally wrote this article back in 2008, but I’ve decided to pull it back out and share it again because this PHOTO WILL NOT DIE! It’s a beautiful image by Inga Nielsen, but it’s not real. – Fraser

Has this image been showing up in your email inbox, forwarded on from excited friends? Along with it may be the following words: “This is the sunset at the North Pole with the moon at its closest point. And you can also see the sun below the moon. An amazing photo and one not easily duplicated. You may want to save this and pass it on to others.” It is a beautiful picture, but is it a real photo?

Even though this image was even featured on the iconic Astronomy Picture of the Day website, the image is in fact a work of art by artist Inga Nielsen, who is also an astrophysics student. The image was created with a computer program, and is called “Hideaway.”



Some internet hoaxes have real staying power (like the ‘Mars as big as the full Moon’ hoax) and this image falls into that “urban legend” category as well. It has been circulating around the internet for over two years, and being passed around as a real photo. According to Nielsen, “Someone cut out my name, called the image “Sunset at the north pole” and told everyone it was a photograph.”

Here is the artist’s website, and if you’re fluent in German, here’s an article about her.

The image was created using a scenery generator program called Terragenâ„¢. Before anything was known about the image, there were some great discussions on forums like Snopes and Hoax-Slayer. People offered some excellent arguments about the scientific and photographic elements that prove its not a real photo. So, if you have any doubts, go take a look. Their arguments are quite convincing. And of course, we now have the artist’s own word for it. Sorry, but no matter how many times you go to the North Pole (or anywhere on Earth for that matter), you’ll never see anything like this image portrays.

Another Editor’s Note: The Moon and the Sun appear to be roughly the same size in the sky, no matter where you are on Earth. From the North Pole or the equator, they’re roughly the same size. And this is why we get total solar eclipses, where the Moon passes in front of the Sun, just covering it up. Fraser

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Tuesday, February 17, 2015

M106: A Spiral Galaxy with a Strange Center

M106: A Spiral Galaxy with a Strange Center:

m106_colombari_960.jpg
M106: A Spiral Galaxy with a Strange Center

Interesting Facts About The Planets

Interesting Facts About The Planets:



A montage of planets and other objects in the solar system. Credit: NASA/JPL


A montage of planets and other objects in the solar system. Credit: NASA/JPL
While the universe is a big place to study, we shouldn’t forget our own backyard. With eight planets and a wealth of smaller worlds to look at, there’s more than enough to learn for a few lifetimes!

So what are some of the most surprising things about the planets? We’ve highlighted a few things below.

1. Mercury is hot, but not too hot for ice

The closest planet to the Sun does indeed have ice on its surface. That sounds surprising at first glance, but the ice is found in permanently shadowed craters — those that never receive any sunlight. It is thought that perhaps comets delivered this ice to Mercury in the first place. In fact, NASA’s MESSENGER spacecraft not only found ice at the north pole, but it also found organics, which are the building blocks for life. Mercury is way too hot and airless for life as we know it, but it shows how these elements are distributed across the Solar System.

2. Venus doesn’t have any moons, and we aren’t sure why.

Both Mercury and Venus have no moons, which can be considered a surprise given there are dozens of other ones around the Solar System. Saturn has over 60, for example. And some moons are little more than captured asteroids, which may have been what happened with Mars’ two moons, for example. So what makes these planets different? No one is really sure why Venus doesn’t, but there is at least one stream of research that suggests it could have had one in the past.



Mars, as it appears today, Credit: NASA


Mars, as it appears today, Credit: NASA
3. Mars had a thicker atmosphere in the past.

What a bunch of contrasts in the inner Solar System: practically atmosphere-less Mercury, a runaway hothouse greenhouse effect happening in Venus’ thick atmosphere, temperate conditions on much of Earth and then a thin atmosphere on Mars. But look at the planet and you can see gullies carved in the past from probable water. Water requires more atmosphere, so Mars had more in the past. Where did it go? Some scientists believe it’s because the Sun’s energy pushed the lighter molecules out of Mars’ atmosphere over millions of years, decreasing the thickness over time.

4. Jupiter is a great comet catcher.

The most massive planet in the Solar System probably had a huge influence on its history. At 318 times the mass of Earth, you can imagine that any passing asteroid or comet going near Jupiter has a big chance of being caught or diverted. Maybe Jupiter was partly to blame for the great bombardment of small bodies that peppered our young Solar System early in its history, causing scars you can still see on the Moon today. And in 1994, astronomers worldwide were treated to a rare sight: a comet, Shoemaker-Levy 9, breaking up under Jupiter’s gravity and slamming into the atmosphere.



Fragmentation of comets is common. Many sungrazers are broken up by thermal and tidal stresses during their perihelions. At top, an image of the comet Shoemaker-Levy 9 (May 1994) after a close approach with Jupiter which tore the comet into numerous fragments. An image taken by Andrew Catsaitis of components B and C of Comet 73P/Schwassmann–Wachmann 3 as seen together on 31 May 2006 (Credit: NASA/HST, Wikipedia, A.Catsaitis)


Fragmentation of comets is common. Many sungrazers are broken up by thermal and tidal stresses during their perihelions. At top, an image of the comet Shoemaker-Levy 9 (May 1994) after a close approach with Jupiter which tore the comet into numerous fragments. An image taken by Andrew Catsaitis of components B and C of Comet 73P/Schwassmann–Wachmann 3 as seen together on 31 May 2006 (Credit: NASA/HST, Wikipedia, A.Catsaitis)
5. No one knows how old Saturn’s rings are

There’s a field of ice and rock debris circling Saturn that from afar, appear as rings. Early telescope observations of the planet in the 1600s caused some confusion: does that planet have ears, or moons, or what? With better resolution, however, it soon became clear that there was a chain of small bodies encircling the gas giant. It’s possible that a single moon tore apart under Saturn’s strong gravity and produced the rings. Or, maybe they’ve been around (pun intended) for the last few billion years, unable to coalesce into a larger body but resistant enough to gravity not to break up.

6. Uranus is more stormy than we thought.

When Voyager 2 flew by the planet in the 1980s, scientists saw a mostly featureless blue ball and some assumed there wasn’t much activity going on on Uranus. We’ve had a better look at the data since then that does show some interesting movement in the southern hemisphere. Additionally, the planet drew closer to the Sun in 2007, and in more recent years telescope probing has shown some storms going on. What is causing all this activity is difficult to say unless we were to send another probe that way. And unfortunately, there are no missions yet that are slated for sure to zoom out to that part of the Solar System.



Infrared images of Uranus showing storms at 1.6 and 2.2 microns obtained Aug. 6, 2014 by the 10-meter Keck telescope. Credit: Imke de Pater (UC Berkeley) & Keck Observatory images.


Infrared images of Uranus showing storms at 1.6 and 2.2 microns obtained Aug. 6, 2014 by the 10-meter Keck telescope. Credit: Imke de Pater (UC Berkeley) & Keck Observatory images.
7. Neptune has supersonic winds.

While on Earth we are concerned about hurricanes, the strength of these storms is nowhere near what you would find on Neptune. At its highest altitudes, according to NASA, winds blow at more than 1,100 miles per hour (1,770 kilometers per hour). To put that in context, that’s faster than the speed of sound on Earth, at sea level. Why Neptune is so blustery is a mystery, especially considering the Sun’s heat is so little at its distance.

8. You can see Earth’s magnetic field at work during light shows.

We have a magnetic field surrounding our planet that protects us from the blasts of radiation and particles the Sun sends our way. Good thing, too, because such flare-ups could prove deadly to unprotected people; that’s why NASA keeps an eye on solar activity for astronauts on the International Space Station, for example. At any rate, when you see auroras shining in the sky, that’s what happens when the particles from the Sun flow along the magnetic field lines and interact with Earth’s upper atmosphere.

Universe Today has many articles on interesting facts about the planets. Start with 10 facts about Mercury  and 10 facts about Venus. You may also want to check out the 10 facts about Mars. Astronomy Cast also has a number of podcasts about the planets, including one on Earth.



About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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What Makes The Solar System Interesting To Astronomers?

What Makes The Solar System Interesting To Astronomers?:



Artist's conception of the solar system, often used in the Eyes on the Solar System 3D Simulator. Credit: NASA


Artist’s conception of the solar system, often used in the Eyes on the Solar System 3D Simulator. Credit: NASA
While most of us are stuck on planet Earth, we’re lucky enough to have a fairly transparent atmosphere. This allows us to look up at the sky and observe changes. The ancients noticed planets wandering across the sky, and occasional visitors such as comets.

Thousands of years ago, most thought the stars ruled our destiny. Today, however, we can see science at work in the planets, asteroids and comets close to home. So why take a look at the Solar System? What can it teach us?

1. The definition of a planet and a moon is fuzzy.

We all know of that famous International Astronomical Union vote in 2006 where Pluto was demoted from planethood into a newly created class called “dwarf planets.” But the definition drew controversy among some, who pointed out that no planet — dwarf or otherwise — perfectly clears the neighborhood in its orbit of asteroids, for example. Moons are considered to orbit around planets, but that doesn’t cover situations such as moons orbiting asteroids or double planets, for example. Goes to show you the Solar System requires more study to figure this out.

2. Comets and asteroids are leftovers.

No, we don’t mean leftovers to eat — we mean leftovers of what the Solar System used to look like. So while it’s easy to get distracted by the weather and craters and prospects for life on planets and moons, it’s important to remember that we must also pay attention to the smaller bodies. Comets and asteroids, for example, could have brought organics and water ice to our own planet — providing what we need for life.



Four images of Comet 67P/Churyumov–Gerasimenko taken on Nov. 30, 2014 by the orbiting Rosetta spacecraft. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0


Four images of Comet 67P/Churyumov–Gerasimenko taken on Nov. 30, 2014 by the orbiting Rosetta spacecraft. Credit: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
3. The planets are all on the same “plane” and orbit in the same direction.

When considering the IAU’s definition of planets, we come up with eight: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. You’ll notice that these bodies tend to follow the same path in the sky (called the ecliptic) and that they orbit the Sun in the same direction. That supports the leading theory for the Solar System’s formation, which is that the planets and moons and Sun formed from a large gas and dust cloud that condensed and spun.

4. We’re nowhere near the center of the galaxy.

We can measure vast distances across the universe by looking at things such as “standard candles” —  a type of exploding stars that tend to have the same luminosity, which makes it easier to predict how far away they are from us. At any rate, looking at our neighborhood, we’ve been able to figure out we’re nowhere near the Milky Way galaxy’s center. We’re about 165 quadrillion miles away from the center supermassive black hole, NASA says, which is probably a good thing.



A still photo from an animated flythrough of the universe using SDSS data. This image shows our Milky Way Galaxy. The galaxy shape is an artist’s conception, and each of the small white dots is one of the hundreds of thousands of stars as seen by the SDSS. Image credit: Dana Berry / SkyWorks Digital, Inc. and Jonathan Bird (Vanderbilt University)


A still photo from an animated flythrough of the universe using SDSS data. This image shows our Milky Way Galaxy. The galaxy shape is an artist’s conception, and each of the small white dots is one of the hundreds of thousands of stars as seen by the SDSS. Image credit:
Dana Berry / SkyWorks Digital, Inc. and Jonathan Bird (Vanderbilt University)
5. But the Solar System is bigger than you think.

Beyond the orbit of Neptune (the furthermost planet), it takes a long time to leave the Solar System. In 2012, some 35 years after leaving Earth on a one-way trip to the outer solar Solar System, Voyager 1 passed through the area where the Sun’s magnetic and gas environment gives way to that of the stars, meaning that it is interstellar space. That was an astounding 11 billion miles (17 billion kilometers) away from Earth, or roughly 118 equivalent Earth-sun distances (astronomical units).

6. The Sun is hugely massive.

Just how massive? 99.86% of the Solar System’s mass is in our local star, which goes to show you where the real heavyweight is. The Sun is made up of hydrogen and helium, which shows you that these gases are far more abundant in our neighborhood (and the Universe generally) than the rocks and metals we are more familiar with here on Earth.



Solar prominences and filaments on the Sun on September 18, 2014, as seen with a hydrogen alpha filter. Credit and copyright: John Chumack/Galactic Images.


Solar prominences and filaments on the Sun on September 18, 2014, as seen with a hydrogen alpha filter. Credit and copyright: John Chumack/Galactic Images.
7. We haven’t finished searching for life here.

So we know for sure that life exists on Earth, but that doesn’t rule out a whole bunch of other places. Mars had water flowing on it in the ancient past, and has frozen water at its poles — making astrobiologists think it might be a good candidate. There also are a range of icy moons that could have oceans with life below the surfaces, such as Europa (at Jupiter) and Enceladus (at Saturn). There’s also the interesting world of Titan, which has “prebiotic chemistry” — chemistry that was a precursor to life — on its surface.

8. We can use the Solar System to better understand exoplanets.

Exoplanets are so far away, and so small in our telescopes, that it’s difficult to see very much detail in their atmospheres. But by looking at the chemistry of Jupiter, for example, we can make some predictions about gas giants further afield. If we look at Earth and Neptune, we can get a better sense of the range of planetary sizes on which life could exist (those “super-Earths” and “mini-Neptunes” you sometimes hear mentioned.) And even looking at where water freezes in our own Solar System can help us better understand the ice line in other locations.

We have written articles about the solar system for Universe Today. Here are facts about the planets in the Solar System. We have recorded a whole series of podcasts about the Solar System at Astronomy Cast. Check them out here.



About 

Elizabeth Howell is the senior writer at Universe Today. She also works for Space.com, Space Exploration Network, the NASA Lunar Science Institute, NASA Astrobiology Magazine and LiveScience, among others. Career highlights include watching three shuttle launches, and going on a two-week simulated Mars expedition in rural Utah. You can follow her on Twitter @howellspace or contact her at her website.

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