Astronomical observations have been obtained from the Polar Environment Atmospheric Research Laboratory (PEARL), which is located in Northern Canada (image credit: left, Steinbring et al., right, Dan Weaver).
The quest for optimal sites to carry out astronomical observations has taken scientists to the frigid Arctic. Eric Steinbring, who led a team of National Research Council Canada experts, noted that a high Arctic site can, “offer excellent image quality that is maintained during many clear, calm, dark periods that can last 100 hours or more.” The new article by Steinbring and colleagues conveys recent progress made to obtain precise observations from a 600 m high ridge near the Eureka research base on Ellesmere Island, which is located in northern Canada.
The new telescope that Steinbring and his colleagues tested was located at the Polar Environment Atmospheric Research Laboratory (PEARL). The observatory can be accessed in winter by 4 x 4 trucks via a 15 km long road from a base facility at sea-level. That base camp is operated by Environment Canada and serviced by an airstrip and resupply ship in summer. Recently, wide-field cameras developed at the University of Toronto were deployed near Eureka to monitor thousands of stars, with the objective of expanding the exoplanet database.
Earlier work by Steinbring and colleagues indicated that data obtained from PEARL imply that clear weather prevails 68% of the time. After significant testing, the team concluded that the site “can allow reliable, uninterrupted temporal coverage during successive dark periods, in roughly 100 hour blocks with clear skies and good seeing.”
The Polar Environment Atmospheric Research Laboratory (PEARL) is located on Ellesmere Island (image credit: left, wikimedia commons, right, Tobias Kerzenmacher).
However, the optimal conditions can be interrupted by brief but potentially intense storms. In the article the team added that, “the primary issue is wind rather than the cold temperatures.” The PEARL facility is equipped with an important weather probe that conveys on-site conditions at 10 minute intervals, thanks to the Canadian Network for the Detection of Atmospheric Change (CANDAC).
There are numerous challenges that arise when observing from the Arctic, but scientists like Steinbring have worked to overcome them, potentially enabling new studies of gravitational lenses and other pertinent phenomena. Indeed, astronomical observations are likewise being obtained from Antarctica. For example, there is the Antarctic Search for Transiting Exoplanets (ASTEP) 40 cm telescope at Dome C, and three 50 cm Antarctic Survey Telescopes (AST3) at Dome A, Antarctica. Steinbring remarked that floorspace is potentially available for up to 5 more telescopes at PEARL, if the compact design they studied was adopted.
E. Steinbring and his colleagues B. Leckie and R. Murowinski are associated with the National Research Council Canada, Herzberg Astronomy and Astrophysics in Victoria, Canada. An electronic preprint of their article is available on arXiv, and the findings were presented recently at theAdapting to the Atmosphere Conference in Durham, UK.
An Iridium flare so bright, it is reflected in a pond. Credit and copyright: Thierry Legault.
There are so many fun sights to see in the sky that are pure astronomical magic. And then there are the spectacular human-created sights. One of those sights is watching satellites from the Iridium constellation that — because of their odd shape — produce spectacular flares that can be brighter than the planet Venus.
Because most of these satellites are still under control by their parent company, their flare timings are easy to predict. And now astrophotographer Thierry Legualt has caught them in action on a video.
“Usually they are photographed in long exposures,” Legault told Universe Today via email. “But last summer I filmed three of them in the Big Dipper and Orion, and they were so bright a pond reflected the flare. In video you can see the real speed of the event.”
The third sequence on the video might look a little odd, but Legault said he rotated the camera 90°. “I found it funny like that,” he said. “Tilt your head or your screen!?”
According to a July Sky & Telescope article, the constellation includes 66 satellites — down from the planned 77 — and is named after element 77 in the periodic table. Normally these machines drift along like a faint star, but when the sunlight catches the side just right, out comes the flash.
“A really bright one can take your breath away,” wrote Bob King, who is also a writer here on Universe Today. “I’ve been lucky enough to witness a few –8 passes and can only describe the experience as alarming. It’s not natural to see a starlike object glow so brilliantly. If you’ve ever wondered what a nearby supernova might look like, treat yourself to one of these.”
Diagram of the Earths orbit around the Sun. Credit: NASA/H. Zell
Ever since the 16th century when Nicolaus Copernicus demonstrated that the Earth revolved around in the Sun, scientists have worked tirelessly to understand the relationship in mathematical terms. If this bright celestial body – upon which depends the seasons, the diurnal cycle, and all life on Earth – does not revolve around us, then what exactly is the nature of our orbit around it?
For several centuries, astronomers have applied the scientific method to answer this question, and have determined that the Earth’s orbit around the Sun has many fascinating characteristics. And what they have found has helped us to understanding why we measure time the way we do.
Orbital Characteristics:
First of all, the speed of the Earth’s orbit around the Sun is 108,000 km/h, which means that our planet travels 940 million km during a single orbit. The Earth completes one orbit every 365.242199 mean solar days, a fact which goes a long way towards explaining why need an extra calendar day every four years (aka. during a leap year).
The planet’s distance from the Sun varies as it orbits. In fact, the Earth is never the same distance from the Sun from day to day. When the Earth is closest to the Sun, it is said to be at perihelion. This occurs around January 3rd each year, when the Earth is at a distance of about 147,098,074 km.
The average distance of the Earth from the Sun is about 149.6 million km, which is also referred to as one astronomical unit (AU). When it is at its farthest distance from the Sun, Earth is said to be at aphelion – which happens around July 4th where the Earth reaches a distance of about 152,097,701 km.
And those of you in the northern hemisphere will notice that “warm” or “cold” weather does not coincide with how close the Earth is to the Sun. That is determined by axial tilt (see below).
Elliptical Orbit:
Next, there is the nature of the Earth’s orbit. Rather than being a perfect circle, the Earth moves around the Sun in an extended circular or oval pattern. This is what is known as an “elliptical” orbit. This orbital pattern was first described by Johannes Kepler, a German mathematician and astronomer, in his seminal work Astronomia nova (New Astronomy).
An illustration of Kepler’s three laws of motion, which show two planets that have elliptical orbits around the Sun. Credit: Wikipedia/Hankwang
After measuring the orbits of the Earth and Mars, he noticed that at times, the orbits of both planets appeared to be speeding up or slowing down. This coincided directly with the planets’ aphelion and perihelion, meaning that the planets’ distance from the Sun bore a direct relationship to the speed of their orbits. It also meant that both Earth and Mars did not orbit the Sun in perfectly circular patterns.
In describing the nature of elliptical orbits, scientists use a factor known as “eccentricity”, which is expressed in the form of a number between zero and one. If a planet’s eccentricity is close to zero, then the ellipse is nearly a circle. If it is close to one, the ellipse is long and slender.
Earth’s orbit has an eccentricity of less than 0.02, which means that it is very close to being circular. That is why the difference between the Earth’s distance from the Sun at perihelion and aphelion is very little – less than 5 million km.
Seasonal Change:
Third, there is the role Earth’s orbit plays in the seasons, which we referred to above. The four seasons are determined by the fact that the Earth is tilted 23.4° on its vertical axis, which is referred to as “axial tilt.” This quirk in our orbit determines the solstices – the point in the orbit of maximum axial tilt toward or away from the Sun – and the equinoxes, when the direction of the tilt and the direction to the Sun are perpendicular.
Over the course of a year the orientation of the axis remains fixed in space, producing changes in the distribution of solar radiation. Credit: NOAA/Thomas G. Andrews
In short, when the northern hemisphere is tilted away from the Sun, it experiences winter while the southern hemisphere experiences summer. Six months later, when the northern hemisphere is tilted towards the Sun, the seasonal order is reversed.
In the northern hemisphere, winter solstice occurs around December 21st, summer solstice is near June 21st, spring equinox is around March 20th and autumnal equinox is about September 23rd. The axial tilt in the southern hemisphere is exactly the opposite of the direction in the northern hemisphere. Thus the seasonal effects in the south are reversed.
While it is true that Earth does have a perihelion, or point at which it is closest to the sun, and an aphelion, its farthest point from the Sun, the difference between these distances is too minimal to have any significant impact on the Earth’s seasons and climate.
Lagrange Points:
Another interesting characteristic of the Earth’s orbit around the Sun has to do with Lagrange Points. These are the five positions in Earth’s orbital configuration around the Sun where where the combined gravitational pull of the Earth and the Sun provides precisely the centripetal force required to orbit with them.
The five Lagrange Points between the Earth are labelled (somewhat unimaginatively) L1 to L5. L1, L2, and L3 sit along a straight line that goes through the Earth and Sun. L1 sits between them, L3 is on the opposite side of the Sun from the Earth, and L2 is on the opposite side of the Earth from L1. These three Lagrange points are unstable, which means that a satellite placed at any one of them will move off course if disturbed in the slightest.
The L4 and L5 points lie at the tips of the two equilateral triangles where the Sun and Earth constitute the two lower points. These points liem along along Earth’s orbit, with L4 60° behind it and L5 60° ahead. These two Lagrange Points are stable, hence why they are popular destinations for satellites and space telescopes.
The study of Earth’s orbit around the Sun has taught scientists much about other planets as well. Knowing where a planet sits in relation to its parent star, its orbital period, its axial tilt, and a host of other factors are all central to determining whether or not life may exist on one, and whether or not human beings could one day live there.
The Allen Telescope Array is the first radio telescope designed specifically for SETI Photo by Colby Gutierrez-Kraybill
Since it was founded in 1984, the SETI (Search for Extraterrestrial Intelligence) Institute in Mountain View, California, has been a principal American venue for scientific efforts to discover evidence of extraterrestrial civilizations. In mid-November, the institute sponsored a conference, “Communicating across the Cosmos”, on the problems of devising and understanding messages from other worlds. The conference drew 17 speakers from numerous disciplines, including linguistics, anthropology, archeology, mathematics, cognitive science, philosophy, radio astronomy, and art.
This is the second of four installments of a report on the conference. Today, we’ll look at the SETI Institute’s current efforts to find an extraterrestrial message, and some of their future plans. If they find something, just how much information can we expect to receive? How much can we send?
The idea of using radio to listen for messages from extraterrestrials is as old as radio itself. Radio pioneers Nikola Tesla and Guglielmo Marconi both listened for signals from the planet Mars early in the 20th century. The first to listen for messages from the stars was radio astronomer Frank Drake in 1960. Until recently though, SETI projects have been limited and sporadic. That began to change in 2007 when the SETI Institute’s Allen Telescope Array (ATA) started observations.
Consisting of 42 small dishes, the ATA is the first radio telescope in the world designed specifically for SETI. The SETI search is currently managed by Jon Richards, an engineer who is an expert on both the system’s hardware and software. He spoke at the conference about the project. The ATA is currently used for SETI research twelve hours out of each day, from 7 pm to 7 am. During the day, the site is operated by Stanford Research International to perform more conventional astronomical studies. When used for such observations, the dishes can function together as an interferometer, generating images of celestial radio sources. To minimize radio interference from human activities, the telescope is sited a six hour drive north of the SETI Institute at the remote Hat Creek Observatory in the Cascade Mountains of Northern California.
The ATA can detect signals over the range from 1 to 10 GHz. The researchers use several strategies to tell potential ETI signals apart from naturally occurring radio sources in space, and human-made terrestrial interference. Radio emissions from natural sources are smeared over a broad range of frequencies. Artificial signals designed for communication typically pack all of their energy into a very narrow frequency band. To detect such signals, the ATA can resolve frequency differences down to just 1 Hz.
When a radio source is moving with respect to the receiver, it appears to change in frequency. This phenomenon is called the Doppler effect. Because an alien planet and the Earth would be moving in relation to one another, a genuine ETI signal would exhibit the Doppler effect. A source of terrestrial interference that’s fixed to the Earth wouldn’t. If the beam of the telescope is shifted away from the target, a genuine alien signal emanating from a distant point in space would disappear, reappearing when the beam was shifted back. A signal due to local interference wouldn’t.
This illustration of the Doppler effect shows the change of wavelength caused by the motion of the source. Credit: ARM.
The ATA is designed to perform these tests automatically whenever it detects a potential candidate signal. To make sure, it repeats the second test five times. If a signal passes the tests, the operator is automatically sent an e-mail, and the candidate signal is entered into a database. Periodically, as a test, the telescope is programed to point in the direction of one of the two Voyager spacecraft. Because these spacecraft are hurtling through deep space beyond the orbit of Neptune, their signals mimic the properties expected from an alien transmission. So far, all the e-mails received have been generated by such tests, and by false alarms. The fateful e-mail announcing the successful detection of an extraterrestrial signal has not yet been sent.
Richards explained that the ATA’s most recent project has been to listen to more than one hundred Earth-like planets discovered by the Kepler space telescope between 2009 and 2012. Next year the ATA’s antenna feeds will get an upgrade that will increase their upper frequency limit to 15 GHz and greatly increase their sensitivity. Both ground-based and Kepler studies have identified numerous Earth-like planets at habitable distances from small dim red dwarf stars. A systematic search of these stars is planned next. If the SETI Institute can find the funding they hope eventually to expand the ATA to 350 dishes.
According to astronomer Jill Tartar, the retired director of the SETI Institute’s Center for SETI Research, the institute is hoping to become involved in a much larger international project; the Square Kilometer Array (SKA). When it begins operations in 2020, the SKA is planned to be the world’s largest radio telescope. It will consist of several thousand dishes and other receivers giving it a radio signal collecting area of one square kilometer. The advantage of having more collecting area is that the telescope is sensitive to fainter signals. If funding allows it to be built in the way currently planned, it will be capable of training multiple simultaneous beams at the sky, some of which Tartar said might be used to mount a continuously ongoing SETI search.
The planned Square Kilometer Array will be the world’s largest radio telescope when it begins operations in 2018 Swinburne Astronomy Productions for SKA Project Development Office
Suppose we did find something. What sort of reply could we send? How much do we have the technological capability to send, if we wanted to? Back in 1974, in the first demonstration of the capacity for interstellar messaging, the Arecibo radio telescope transmitted a mere 210 bytes, and took 3 minutes to do it. The message consisted of a human stick figure and a few other crude symbols and diagrams. Because this primitive effort is still the most well-known example of interstellar radio messaging, prepare yourself for a stunning surprise. According to SETI Institute radio astronomer Seth Shostak, using broadband microwave radio, we could send them the Library of Congress (consisting of 17 million books) in 3 days, and the contents of the World Wide Web (as of 2008) in a comparable time.
Using the shorter optical wavelengths of a laser beam and optical broadband, we could send either one in 20 minutes. Since the extraterrestrials might tune in at any time, we would need to send the transmission over and over again many times. Although our transmissions could be sent in only days or minutes, they would, of course, still take decades or centuries to traverse the light years. This transmission capability presents a stunning opportunity. We can send anything. We can send everything. Could it really be that someday, beings from Tau Ceti will peruse your Facebook page?
So what can we expect from the aliens? Any message we might receive, Seth Shostak thought, would be of one of two possible sorts. A civilization already aware of our existence, he believed, would send us a huge message, rich in information content. This is because even if technological civilizations are fairly common in the galaxy the nearest one might be tens, hundreds, or thousands of light years away. Radio messages traveling at the speed of light will take that long to cross those distances, and decades or centuries will elapse between query and response. If we are contacted, Shostak really does think that we should send the aliens the entire content of the World Wide Web. Civilizations further away than 70 light years from Earth probably wouldn’t know that we exist, because radio signals from Earth haven’t reached them yet. Shostak didn’t think that civilizations would waste precious transmitting time and energy bombarding planets with petabytes of information if they didn’t already know that there was a technological civilization there. Worlds that weren’t known to harbor a civilization, Shostak speculated, might get put on a long list of potentially habitable planets to which the aliens might periodically send a brief “ping” hoping to get a response.
A petabyte of gibberish contains as much information as a petabyte of our world’s greatest art and literature (or tackiest YouTube videos). A petabyte of our world’s greatest art and literature is gibberish to a being who can’t understand it. We could send the aliens truly stunning amounts of information, but can we find some way to ensure that they will understand its meaning? Could we hope to understand an alien message sent to us, or would all those petabytes be for naught? In the next installment, we’ll learn that we face daunting problems.
S. J. Dick (1996), The Biological Universe: The Twentieth_Century Extraterrestrial Life Debate and the Limits of Science, Cambridge University Press, Cambridge, UK.
A team of astronomers have used the Subaru Telescope to look back more than 13 billion years to find 7 early galaxies that appeared quite suddenly within 700 million years of the Big Bang . Credit: NASA/WMAP Science Team
It’s an amazing thing, staring into deep space with the help of a high-powered telescope. In addition to being able to through the vast reaches of space, one is also able to effectively see through time.
Using the Subaru Telescope’s Suprime-Cam, a team of astronomers has done just that. In short, they looked back 13 billion years and discovered 7 early galaxies that appeared quite suddenly within 700 million years of the Big Bang. In so doing, they discovered clues to one of astronomy’s most burning questions: when and how early galaxies formed in our universe.
The team, led by graduate student Akira Konno and Dr. Masami Ouchi (Associate Professor at the University of Tokyo’s ICRR) was looking for a specific kind of galaxy called a Lyman-alpha emitter (LAE), to understand the role such galaxies may have played in an event called “cosmic reionization”.
The current cosmological model states that the universe was born in the Big Bang some 13.8 billion years ago. In its earliest epochs, it was filled with a hot “soup” of charged protons and electrons. As the newborn universe expanded, its temperature decreased uniformly.
It is estimated that the first stars and galaxies formed 12.8 billion years ago, during a period of “cosmic reionization”. Credit: NASA/ESA/A. Felid (STScI)
When the universe was 400,000 years old, conditions were cool enough to allow the protons and electrons to bond and form neutral hydrogen atoms. That event is called “recombination” and resulted in a universe filled with a “fog” of these neutral atoms.
Eventually the first stars and galaxies began to form, and their ultraviolet light ionized the hydrogen atoms, and “divided” the neutral hydrogen into protons and electrons again. As this occurred, the “fog” of neutral hydrogen cleared.
Astronomers call this event “cosmic reionization” and think that it ended about 12.8 billion years ago – a billion years after the Big Bang. The timing of this event – when it started and how long it lasted – is one of the big questions in astronomy.
To investigate this cosmic reionization, the Subaru team searched for early LAE galaxies at a distance of 13.1 billion light years. Although Hubble Space Telescope has found more distant LAE galaxies, the discovery of seven such galaxies at 13.1 billion light-years represents a distance milestone for Subaru Telescope.
Color composite images of seven LAEs found in the study. The red objects between two white lines are the LAEs. Credit: ICRR, University of Tokyo
Mr. Konno, the graduate student heading the analysis of the data from the Subaru Telescope pointed out the obstacles that Subaru had to overcome to make the observations.”It is quite difficult to find the most distant galaxies due to the faintness of the galaxies.” he said. “So, we developed a special filter to be able to find a lot of faint LAEs. We loaded the filter onto Suprime-Cam and conducted the most distant LAE survey with the integration time of 106 hours.”
That extremely long integration time was one of the longest ever performed at Subaru Telescope. It allowed for unprecedented sensitivity and enabled the team to search for as many of the most distant LAEs as possible.
According to Konno, the team expected to find several tens of LAEs. Instead they only found seven.
“At first we were very disappointed at this small number,” Konno said. “But we realized that this indicates LAEs appeared suddenly about 13 billion years ago. This is an exciting discovery. We can see that the luminosities suddenly brightened during the 700-800 million years after the Big Bang. What would cause this?”
This shows evolution of the Lyman-alpha luminosities of the galaxies. Credit: ICRR, University of Tokyo; Hubble Space Telescope/NASA/ESA
As the table above illustrates, the luminosities of LAEs changed based on this study. The yellow circle at 1 billion years after the Big Bang is used for normalization. The yellow circles come from previous studies, and the yellow dashed line shows the expected evolutionary trend of the luminosity.
The current finding is shown by a red circle, and we can see that the galaxies appear suddenly when the universe was 700 million years old. This indicates that the neutral hydrogen fog was suddenly cleared, allowing the galaxies to shine out, as indicated by the backdrop shown for scale and illustration.
According to the team’s analysis, one reason that LAEs appeared very quickly is cosmic reionization. LAEs in the epoch of cosmic reionization became darker than the actual luminosity due to the presence of the neutral hydrogen fog.
In the team’s analysis of their observations, they suggest the possibility that the neutral fog filling the universe was cleared about 13.0 billion years ago and LAEs suddenly appeared in sight for the first time.
“However, there are other possibilities to explain why LAEs appeared suddenly,” said Dr. Ouchi, who is the principal investigator of this program. “One is that clumps of neutral hydrogen around LAEs disappeared. Another is that LAEs became intrinsically bright. The reason of the intrinsic brightening is that the Lyman-alpha emission is not efficiently produced by the ionized clouds in a LAE due to the significant escape of ionizing photons from the galaxy. In either case, our discovery is an important key to understanding cosmic reionization and the properties of the LAEs in early universe.”
Dr. Masanori Iye, who is a representative of the Thirty Meter Telescope (TMT) project of Japan, commented on the observations and analysis. “To investigate which possibility is correct, we will observe with HSC (Hyper Suprime-Cam) on Subaru Telescope, which has a field of view 7 times wider than Suprime-Cam, and TMT currently being built on the summit of Mauna Kea in Hawaii in the future. By these observations, we will clarify the mystery of how galaxies were born and cosmic reionization occurred.”
A binary black hole system, viewed edge-on. This pair of extremely dense objects twists and warps spacetime as the two black holes spiral in toward one another. Image Credit: Bohn, Throwe, Hébert, Henriksson, Bunandar, Taylor, Scheel (see http://www.black-holes.org/lensing)
A black hole is an extraordinarily massive, improbably dense knot of spacetime that makes a living swallowing or slinging away any morsel of energy that strays too close to its dark, twisted core. Anyone fortunate (or unfortunate) enough to directly observe one of these beasts in the wild would immediately notice the way its colossal gravitational field warps all of the light from the stars and galaxies behind it, a phenomenon known as gravitational lensing.
Thanks to the power of supercomputers, a curious observer no longer has to venture into outer space to see such a sight. A team of astronomers has released their first simulated images of the lensing effects of not just one, but two black holes, trapped in orbit by each other’s gravity and ultimately doomed to merge as one.
Astronomers have been able to model the gravitational effects of a single black hole since the 1970s, but the imposing mathematics of general relativity made doing so for a double black-hole system a much larger challenge. Over the last ten years, however, scientists have improved the accuracy of computer models that deal with these types of calculations in an effort to match observations from gravitational wave detectors like LIGO and VIRGO.
The research collaboration Simulating Extreme Spacetimes (SXS) has begun using these models to mimic the lensing effects of high-gravity systems involving objects such as neutron stars and black holes. In their most recent paper, the team imagines a camera pointing at a binary black hole system against a backdrop of the stars and dust of the Milky Way. One way to figure out what the camera would see in this situation would be to use general relativity to compute the path of each photon traveling from every light source at all points within the frame. This method, however, involves a nearly impossible number of calculations. So instead, the researchers worked backwards, mapping only those photons that would reach the camera and result in a bright spot on the final image – that is, photons that would not be swallowed by either of the black holes.
As you can see in the image above, the team’s simulations testify to the enormous effect that these black holes have on the fabric of spacetime. Ambient photons curl into a ring around the converging binaries in a process known as frame dragging. Background objects appear to multiply on opposite sides of the merger (for instance, the yellow and blue pair of stars in the “northeast” and the “southwest” areas of the ring). Light from behind the camera is even pulled into the frame by the black holes’ mammoth combined gravitational field. And each black hole distorts the appearance of the other, pinching off curved, comma-shaped regions of shadow called “eyebrows.” If you could zoom in with unlimited precision, you would find that there are, in fact, an infinite number of these eyebrows, each smaller than the last, like a cosmic set of Russian dolls.
In case you thought things couldn’t get any more amazing, SXS has also created two videos of the black hole merger: one simulated from above, and the other edge-on.
The SXS collaboration will continue to investigate gravitationally ponderous objects like black holes and neutron stars in an effort to better understand their astronomical and physical properties. Their work will also assist observational scientists as they search the skies for evidence of gravitational waves.
Check out the team’s ArXiv paper describing this work and their website for even more fascinating images.
The total solar eclipse of November 2012 as seen from
Where will YOU be on August 21st, 2017?
Astronomy is all about humility and thinking big in terms of space and time. It’s routine for astronomers to talk of comets on thousand year orbits, or stars with life spans measured in billions of years…
Yup, the lifespan of your average humanoid is indeed fleeting, and pales in comparison to the universe, that’s for sure. But one astronomical series that you can hope to live through is the cycle of eclipses.
I remember reading about the total solar eclipse of February 26th, 1979 as a kid. Carter was in the White House, KISS was mounting yet another comeback, and Voyager 1 was wowing us with images of Jupiter. That was also the last total solar eclipse to grace mainland United States in the 20th century.
But the ongoing “eclipse-drought” is about to be broken.
One thousand days from this coming Monday, November 24th on August 21st 2017, the shadow of the Moon will touch down off of the Oregon coast and sweep eastward across the U.S. heartland before heading out to the Atlantic off of the coast of South Carolina. Millions live within a days’ drive of the 115 kilometre wide path, and the eclipse has the added plus of occurring at the tail end of summer vacation season. This also means that lots of folks will be camping and otherwise mobile with their RVs and able to journey to the event.
This is also the last total solar eclipse to pass over any of the 50 United States since July 11th, 1991, and the first eclipse to cross the contiguous United States from “sea to shining sea” since way back on June 8th, 1918.
Think it’s too early to prepare? Towns across the path, including Hopkinsville, Kentucky and towns in Kansas and Nebraska are already laying plans for eclipse day. Other major U.S. cities, such as Nashville, Idaho Falls, and Columbia, South Carolina also lie along the path of totality, and the spectacle promises to spawn a whole new generation of “umbraphiles” or eclipse chasers.
A total solar eclipse is an unforgettable sight. But unlike a total lunar eclipse, which can be viewed from the moonward-facing hemisphere of the Earth, one generally has to journey to the narrow path of totality to see a total solar eclipse. Totality rarely comes to you.
The Zeilers view the November 2013 eclipse from Africa. Credit: Michael Zeiler.
And don’t settle for a 99% partial eclipse just outside the path. “There’s no comparison between partial and total solar eclipses when it comes to sheer grandeur and beauty,” Michael Zeiler, longtime eclipse chaser and creator of the Great American Eclipse website told Universe Today. We witnessed the 1994 annular solar eclipse of the Sun from the shores of Lake Erie, and can attest that a 99% partial eclipse is still pretty darned bright!
There are two total solar eclipses remaining worldwide up until 2017: One on March 20th, 2015 crossing the high Arctic, and another on March 9th 2016 over Southeast Asia. The 2017 eclipse offers a maximum of 2 minutes and 41 seconds of totality, and weather prospects for the eclipse in late August favors viewers along the northwestern portion of the track.
And though an armada of cameras will be prepared to capture the eclipse along its trek across the U.S., many veteran eclipse chasers suggest that first time viewers merely sit back and take in the moment. The onset of totality sees a bizarre sort of twilight fall across the landscape, as shadow bands skip across the countryside, temperatures drop, and wildlife is fooled into thinking that nightfall has come early.
And then, all too soon, the second set of blinding diamond rings burst through the lunar valleys, the eclipse glasses go back on, and totality is over. Which always raises the question heard throughout the crowd post-eclipse:
When’s the next one?
Well, the good news is, the United States will host a second total solar eclipse on April 8th, 2024, just seven years later! This path will run from the U.S. Southwest to New England, and crisscross the 2017 path right around Carbondale, Illinois.
Will the woo that surfaced around the approach of Comet ISON and the lunar tetrad of “blood Moon eclipses” rear its head in 2017? Ah, eclipses and comets seem to bring ‘em out of the woodwork, and 2017 will likely see a spike in the talking-head gloom and doom videos ala YouTube. Some will no doubt cite the “perfection” seen during total solar eclipses as proof of divine inspiration, though this is actually just a product of our vantage point in time and space. In fact, annular eclipses are slightly more common than total solars in our current epoch, and will become more so as the Moon slowly recedes from the Earth. And we recently noted in our post on the mutual phenomena of Jupiter’s moons that solar eclipses very similar to those seen from the Earth can also be spied from Callisto.
Heads up to any future interplanetary eclipse resort developer: Callisto is prime real estate.
The 70 meter Evpatoria Planetary Radar radio telescope in the Crimea was used to transmit 4 interstellar messages in 1999, 2001, 2003, and 2008
Over the last 20 years, astronomers have discovered several thousand planets orbiting other stars. We now know that potentially habitable Earth-like planets are abundant in the cosmos. Such findings lend a new plausibility to the idea that intelligent life might exist on other worlds. Suppose that SETI (Search for Extraterrestrial Intelligence) researchers succeed in their quest to find a message from a distant exoplanet. How much information can we hope to receive or send? Can we hope to decipher its meaning? Can humans compose interstellar messages that are comprehensible to alien minds?
Such concerns were the topic of a two day academic conference on interstellar messages held at the SETI Institute in Mountain View, California; ‘Communicating across the Cosmos’. The conference drew 17 speakers from a wide variety of disciplines, including linguistics, anthropology, archeology, mathematics, cognitive science, philosophy, radio astronomy, and art. This article is the first of a series of installments about the conference. Today, we’ll explore the ways in which our society is already sending messages to extraterrestrial civilizations, both accidentally and on purpose.
Sending radio messages over sizable interstellar distances is feasible with present day technology. According to SETI Institute radio astronomer Seth Shostak, who presented at the conference, we are already — by accident — constantly signaling our presence to any extraterrestrial astronomers that might exist in our neighborhood of the galaxy. Some radio signals intended for domestic uses leak into space. The most powerful come from radars used for military purposes, air traffic control, and weather forecasting. Because these radars sweep across broad swaths of the sky, their signals travel out into space in many directions.
With radio telescopes no more sensitive than those astronomers on Earth use today, extraterrestrials out to distances of tens of light years could detect them and figure out that they were artificial. The Arecibo radar telescope in Puerto Rico is designed specifically to send a narrow beam of radio waves into space, usually to bounce them off celestial bodies and learn about their surfaces. For a receiver within its beam, it could be detected hundreds of light-years away.
FM radio and television broadcasts also leak out into space, but they are weaker and couldn’t be detected more than about one tenth of a light year away with present day human technology. This is quite a bit less than the distance to the nearest star. The size and sensitivity of radio telescopes is progressing rapidly. An alien civilization just a few centuries more advanced than us in radio technology could detect even these weak signals over vast distances in the galaxy. As our signals spread outward at the speed of light, they will reach progressively larger numbers of stars and planets, any one of which might be home to ETI. If they really are out there, they are likely to find us eventually.
Humans have been fascinated with formulating messages for extraterrestrials for a surprisingly long time. Eighteenth and nineteenth century scientists drew up proposals to make huge fire pits or plantings in the shapes of geometric figures that they hoped would be visible in the telescopes of the inhabitants of neighboring worlds. In the early days of radio, attempts were made to contact Mars and Venus.
As prospects for intelligent life within the solar system dimmed, attention turned to the stars. In the early 1970’s the first two spacecraft to escape the sun’s gravitational pull, Pioneer 10 and 11, each carried an engraved plaque designed to tell aliens where Earth is, and what human beings look like. Voyager 1 and 2 carried a more ambitious message of images and sounds encoded on a phonograph record. Both the Pioneer plaques and the Voyager records were devised by teams led by astronomers Carl Sagan and Frank Drake, both SETI pioneers. In 1974, the powerful Arecibo radio telescope beamed a brief 3 minute message towards a star cluster 21,000 light years away as part of a dedication ceremony for a major upgrade. The binary coded message was an image, including a stick figure of a human, our solar system, and some chemicals important to earthly life. The distant target was chosen simply because it was overhead at the time of the ceremony.
The plaque affixed to the Pioneer 10 and 11 spacecraft, the first spacecraft to leave our solar system. In the upper left corner is a diagram depicting the hydrogen atom, the most abundant element in the universe. The diagram symbolizes the transition of the electron from a spin-up to a spin-down state. This transition is responsible for radio emissions at the wavelength of 21 cm by clouds of hydrogen gas in interstellar space. This phenomenon is very familiar to radio astronomers and provides a distance standard used to indicate the sizes of the human beings. In the middle left is a representation of position of the sun with respect to the center of the galaxy and 14 pulsars. At the bottom is a map of the solar system indicating the origin of the spacecraft as the sun’s third planet. The relative distances of the planets from the sun are indicated as binary numbers with a unit one tenth the distance of Mercury from the sun. At the right is a depiction of a human couple with the man’s arm raised in a gesture of friendly greeting and the pioneer spacecraft drawn in outline as a backdrop NASA Ames Research Center.
Cultural anthropologist and conference speaker Klara Anna Capova said that in recent years, messaging to extraterrestrials has moved beyond science and become a commercial enterprise. In 1999 and 2003, a private company solicited content from the general public and transmitted these ‘Cosmic Call’ messages to several nearby sun-like stars from the 70 meter radio telescope of the Evpatoria Deep Space Center in Crimea, Ukraine.
In 2009, another private company transmitted 25,000 messages, collected via a website, towards the red dwarf star Gliese 581, 20 light years away. In 2008, a Dorito’s commercial was beamed to a sun-like star 42 light years away, and in 2009 Penguin books transmitted 1000 messages as part of a book promotion. In 2010, a greeting, spoken in the fictional Klingon language, was beamed towards the star Arcturus, 37 light years away. The message was sent to promote the opening of what was billed as the first authentic Klingon opera on Earth. As one conference speaker noted, there are no regulations on the transmission or content of such messages.
Actively messaging extraterrestrials is a controversial practice, and the director of the Evpatoria Center, Alexander Zaitsev, has faced criticism from some members of the scientific community for his actions. Traditionally, SETI researchers have simply listened for alien messages. A received message might allow humans to learn something about the nature and motives of its extraterrestrial senders. That might give us a basis for deciding whether or not it was wise and prudent to reply.
Drake’s Arecibo message, by intent, was beamed at a star cluster tens of thousands of light years away and was meant simply to demonstrate the capacity for interstellar messaging. The Pioneer and Voyager spacecraft likewise will not reach the stars for tens of thousands of years. On the other hand, the recent transmissions were directed at nearby stars, from which we might receive a reply in less than a century. At the conference, Seth Shostak advanced what he confessed was a provocative position. He said we shouldn’t worry too much about the recent transmissions, because the much weaker signals that constantly emanate from Earth would be detectable by extraterrestrial civilizations with more advanced radio technology anyway. “That horse”, he said “has already left the barn”.
In the next installment, we will explore the SETI Institute’s current and planned efforts to conduct our human search for extraterrestrial signals. We will consider the limits of our own signaling capacity, and learn that the amount of information we could send the aliens is truly vast.
References and Further Reading:
Communicating across the Cosmos: How can we make ourselves understood by other civilizations in the galaxy (2014), SETI Institute Conference Website
M. J. Crowe (1986) The Extraterrestrial Life Debate 1750-1900: The Idea of a Plurality of Worlds From Kant to Lowell, University of Cambridge, Cambridge, UK.
C. Sagan, F. Drake, A. Druyan, T. Ferris, J. Lomberg, L. S. Sagan (1978), Murmurs of Earth: The Voyager Interstellar Record, Random House, New York, NY.
All the physical properties of our Universe – indeed, the fact that we even exist within a Universe that we can contemplate and explore – owe to events that occurred very early in its history. Cosmologists believe that our Universe looks the way it does thanks to a rapid period of inflation immediately before the Big Bang that smoothed fluctuations in the vacuum energy of space and flattened out the fabric of the cosmos itself.
According to current theories, however, interactions between the famed Higgs boson and the inflationary field should have caused the nascent Universe to collapse. Clearly, this didn’t happen. So what is going on? Scientists have worked out a new theory: It was gravity that (literally) held it all together.
The interaction between the curvature of spacetime (more commonly known as gravity) and the Higgs field has never been well understood. Resolving the apparent problem of our Universe’s stubborn existence, however, provides a good excuse to do some investigating. In a paper published this week in Physical Review Letters, researchers from the University of Copenhagen, the University of Helsinki, and Imperial College London show that even a small interaction between gravity and the Higgs would have been sufficient to stave off a collapse of the early cosmos.
The researchers modified the Higgs equations to include the effect of gravity generated by UV-scale energies. These corrections were found to stabilize the inflationary vacuum at all but a narrow range of energies, allowing expansion to continue and the Universe as we know it to exist… without the need for new physics beyond the Standard Model.
This new theory is based on the controversial evidence of inflation announced by BICEP2 earlier this summer, so its true applicability will depend on whether or not those results turn out to be real. Until then, the researchers are hoping to support their work with additional observational studies that seek out gravitational waves and more deeply examine the cosmic microwave background.
At this juncture, the Higgs-gravity interaction is not a testable hypothesis because the graviton (the particle that handles all of gravity’s interactions) itself has yet to be detected. Based purely on the mathematics, however, the new theory presents an elegant and efficient solution to the potential conundrum of why we exist at all.
Artist view of an asteroid (with companion) passing near Earth. Credit: P. Carril / ESA
Asteroids and comets have a few things in common. They are both celestial bodies orbiting our Sun, and they both can have unusual orbits, sometimes straying close to Earth or the other planets. They are both “leftovers” — made from materials from the formation of our Solar System 4.5 billion years ago. But there are a few notable differences between these two objects, as well. The biggest difference between comets and asteroids, however, is what they are made of.
While asteroids consist of metals and rocky material, comets are made up of ice, dust, rocky materials and organic compounds. When comets get closer to the Sun, they lose material with each orbit because some of their ice melts and vaporizes. Asteroids typically remain solid, even when near the Sun.
Right now, the majority of asteroids reside in the asteroid belt, a region between the orbits of Mars and Jupiter which may hold millions of space rocks of varying sizes. On the other hand, the majority of comets are in the farthest reaches of our Solar System: either 1. in the Kuiper Belt — a region just outside the orbit of the dwarf planet Pluto that may have millions of icy comets (as well as many icy dwarf planets like Pluto and Eris); or 2. the Oort Cloud, a region where trillions of comets may circle the Sun at huge distances of up to 20 trillion kilometers (13 trillion miles).
Anillustration of what the Oort cloud might be like. Credit: Don Yeomans/JPL.
Some scientists think asteroids formed much closer to the Sun, where it was too warm for any ices to remain solid, while comets formed farther from the Sun and were therefore able to retain ice. However, other scientists think that the comets that are now in the Kuiper Belt and Oort cloud actually formed in the inner Solar System, but were then flung out from the gravitation effects of the giant planets Jupiter and Saturn.
We do know that gravitational perturbations periodically jar both asteroids and comets from their usual “homes” — setting them on orbital courses that bring them closer to the Sun, as well as Earth.
When comets approach the Sun, some of their ices melt. This causes another notable difference between asteroids and comets: comets have “tails” while asteroids generally don’t. When the ices in comets begin to melt and other materials vaporize from the heat from the Sun, this forms a glowing halo that extends outward from the comet as it sails through space. The ice and compounds like methane and ammonia develop a fuzzy, cloud-like shell called a coma. Forces exerted on the coma by the Sun’s radiation pressure and solar wind cause an enormous, elongated tail to form. Tails always points away from the Sun.
Asteroids typically don’t have tails, even those near the Sun. But recently, astronomers have seen some asteroids that have sprouted tails, such as asteroid P/2010 A2. This seems to happen when the asteroid has been hit or pummeled by other asteroids and dust or gas is ejected from their surfaces, creating a sporadic tail effect. These so-called “active asteroids” are a newly recognized phenomenon, and as of this writing, only 13 known active asteroids have been found in the main asteroid belt, and so they are very rare.
Another difference between asteroids and comets is in their orbital patterns. Asteroids tend to have shorter, more circular orbits. Comets tend to have very extended and elongated orbits, which often exceed 50,000 AU from the Sun. (*Note: 1 AU, or Astronomical Unit, equals the distance from the Earth to the Sun.) Some, called long-period comets come from the Oort Cloud and are in big elliptical orbits of the Sun that take them far out beyond the planets and back. Others, called short-period comets come from the Kuiper Belt and travel in shorter orbits around the Sun.
There is a big difference when it comes to numbers… although there is a caveat in that we don’t know precisely how many asteroids OR comets there are in our Solar System, since many have never been seen. Astronomers have discovered millions of asteroids – some as small as dust particles and others measuring hundreds of kilometers across. But as of this writing, astronomers have found only about 4,000 comets. However, some estimates say there could be one hundred billion comets in the Oort cloud.
The fact that asteroids and comets were both formed during the earliest days of our Solar System has scientists studying both with keen interest. By examining them up close with satellites and landers — such as the current Rosetta mission with the Philae lander to Comet 67P — scientists hope to learn more about what our Solar System looked like in its earliest days. The next mission to a comet will be the JAXA Hayabusa-2 mission, which should launch at the end of November or early December 2014, arriving in 2018 to asteroid (162173) 1999 JU. Here’s a list of past missions to asteroids and comets.
Scientists also study comets and asteroids to determine the likelihood of them hitting Earth and other planets, and what effect their flybys could have on planetary atmospheres. In November of 2014, a comet named Siding Spring flew very close to Mars, and scientists are still studying the encounter. But this may happen more often that we think: one recent study says that Mars gets bombarded by 200 small asteroids or comets every year.
How likely is it that our planet could be hit by a large asteroid or comet? We do know that Earth has been hit many times in the past by asteroids and comets whose orbits bring them into the inner Solar System. There is strong scientific evidence that cosmic collisions played a major role in the mass extinctions documented in Earth’s fossil records. These objects that come close to Earth, known as Near Earth Objects or NEOs, still pose a danger to Earth today. But NASA, ESA and other space agencies have search programs that have discovered hundreds of thousands of main-belt asteroids, comets. None at this time pose any threat to Earth. You can find out more on this topic at NASA’s Near Earth Object Program website.
Additionally, the possibility of mining both asteroids and comets someday is also becoming a source of interest for industrialists and commercial space ventures, such as Planetary Resources.
