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Spotting a comet in the all-sky maps from SOHO's instrument SWAN
An animation showing the movement of comet C/2020 F8 (SWAN) through successive all-sky maps made by the Solar Wind ANisotropies (SWAN) instrument aboard the ESA/NASA Solar and Heliospheric Observatory (SOHO). The sequence covers the period from 1 April to 9 May 2020. The comet can be seen as a moving white blob on the left of the image, just below the middle line of the coordinate grid, indicated with an arrow starting from the 5 April map. The comet is small to start with but gradually grows bigger. It was using these maps that Australian amateur Michael Mattiazzo discovered the comet.
Between 17 and 27 April, the comet disappears behind the black areas that identify regions of the sky too bright to be observed, but by 28 April it is clearly visible again towards the left edge of the map. When the comet leaves the left-hand side of the image, it reappears on the right-hand side after 2 May (the image represents the 360-degree sky mapping used by SWAN). | 0.825686 | 3.188129 |
Scientists on the Cassini mission have become out-of-this world "plumbers" as they try to piece together what's happening inside the "pipes" feeding the plumes of Saturn's moon Enceladus.
Enceladus is jetting out giant geysers three times the size of the moon, and now scientists are beginning to understand how the ice grains are created and how they might have formed. Knowing the process of how the plume forms and the path the water-ice particles have to travel is giving them an insight into what may be a liquid reservoir or lake lying just beneath the surface.
"Since Cassini discovered the water vapor geysers, we've all wondered where this water vapor and ice are coming from. Is it from an underground water reservoir or are there some other processes at work? Now, after looking at data from multiple instruments, we can say there probably is water beneath the surface of Enceladus," said Juergen Schmidt, team member on Cassini's Cosmic Dust Analyzer at the University of Potsdam, Germany. This study appears in the Feb. 7, 2008, issue of the journal Nature.
The large number of ice particles observed spewing from the geysers and the steady rate at which these particles are produced require high temperatures, close to the melting point of ice, possibly resulting in an internal lake. The lake would be similar to Earth's Lake Vostok, beneath Antarctica, where liquid water exists locked in ice. The ice grains then condense in the vapor evaporating from the water, streaming through cracks in the ice crust to the surface.
The presence of liquid water inside Enceladus would have major implications for future astrobiology studies on the possibility of life on bodies in the outer solar system.
Scientists have studied the plume dynamics since 2005, collecting data from several Cassini remote sensing instruments and those that sample particles directly, like the Cosmic Dust Analyzer. They conclude that an internal lake at a temperature of about 273 Kelvin (32 degrees Fahrenheit) is the best way to account for the material jetting out of the geysers.
At these warm temperatures, liquid water, ice and water vapor mingle. The vapor escapes to the vacuum of space through cracks in Enceladus' ice crust. When the gas expands, it cools and the ice grains that make up the visible part of the plumes condense from the vapor. Vapor in the plumes is clocked at roughly the same speed as a supersonic jet, about 300 to 500 meters per second, or about 650 to 1,100 miles per hour. However, most of the condensed ice particles fail to reach Enceladus' escape velocity of 240 meters per second (536 miles per hour).
Pinball-like physics account for the slow speed of the particles. Shooting up through crooked cracks in the ice, the particles ricochet off the walls, losing speed, while the water vapor moves unimpeded up the crevasse. The vapor reboosts the frozen particles as they pinball off the walls, carrying them upward. Reaching nozzle-like openings at the surface, the faster-moving water vapor shoots high above Enceladus, becoming entrapped in Saturn's magnetosphere. Most of the particles, which have lost energy through collisions in transit, fail to achieve escape velocity and fall back to Enceladus' surface. Only about 10 percent escape Enceladus and form Saturn's E-ring.
"Our model provides a simple concept to understand how particles form, their speed and how they behave as they make their way out into space. If vapor temperature is too low, then the gas density is too small to push the grains out and we would not see such large amounts of particles," said Schmidt. "Therefore, we believe that at the site of evaporation, we must have temperatures near the melting point of water."
Scientists say that particles seen in the plumes are too numerous to have started from processes described in one existing model that requires low temperatures, proposing that gases may be trapped inside ice crystals. Another model suggests that water ice, suddenly exposed to the vacuum of space, sublimes, or boils, directly into vapor without liquefying first. But this would mean there are short bursts of activity, rather than the steady production of particles. The new model of grains condensing in a vent that evaporates from a liquid body is consistent with a steady production of particles, ejected from a localized source.
This research provides fundamental knowledge about solar system bodies, in particular those that, like our home planet, are homes to oceans - environments where life might evolve.
The next Enceladus flyby is in March 2008. The spacecraft closest approach will be at a mere 50 kilometers (30 miles) from the surface and the altitude will increase to about 200 kilometers (124 miles) as the spacecraft passes through the plumes. Cassini will sample the plumes directly and find out more about their makeup.
For more information:
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Science Mission Directorate, Washington, D.C. JPL designed, developed and assembled the Cassini orbiter.
Media Relations Contact: Carolina Martinez (JPL) 818-354-9382 | 0.806493 | 4.027603 |
All the planets we've found in the Milky Way — so far
Astronomers have confirmed the existence of more than 3,000 "exoplanets" — planets that aren't in our solar system, orbiting stars other than our sun. The chart above shows how similar they are to Earth.
Why it matters: A small number of discovered exoplanets — those that are small enough to have a rocky surface and the right distance from their star to hold liquid water — may be able to support life, and provide clues about the evolution of our own planet.
The big picture: The first discovery of a planet orbiting a star other than the sun was only 30 years ago.
- In 1988, scientists announced the discovery of a planet orbiting a pulsar nearly 5,000 light-years away.
- Over the last three decades, the pace of discovery has only quickened: More than half of confirmed exoplanet discoveries have been announced in the last four years.
Most of the recent discoveries were detected by the Kepler space telescope, the first space-based telescope designed specifically to find Earth-sized planets orbiting other stars. "Kepler was a complete game-changer," MIT astronomer Sara Seager told Axios.
- That's why Seager is enthusiastic about analyzing the findings from Kepler's successor, the Transiting Exoplanet Survey Satellite (TESS), which was launched in April.
- TESS searches for Earth-like planets in an area of the sky closer to Earth than where Kepler looked, making it easier for astronomers to later confirm the planets' existence by calculating their mass.
Since TESS began making observations in July, it has already made two confirmed exoplanet discoveries. Scientists expect it to make thousands more as it sends its findings back to Earth. "Every month we get a deluge of data," Seager said.
What's next: Neither TESS, nor Kepler, nor any of the massive land-based telescopes searching the galaxy for planets are able to capture actual images of exoplanets.
- Instead, they detect their presence by measuring changes in their stars' light over time.
The bottom line: The technology for capturing even pixel-sized images of exoplanets — which would help scientists better assess whether their atmospheres are suitable for life — is still many years away. | 0.858722 | 3.456043 |
With the Mercury Messenger mission now coming to its end, it seems an appropriate time to speculate on why our inner Solar System looks the way it does. After all, as we continue finding new solar systems, we’re discovering many multi-planet systems with planets — often more than one — closer to their star than Mercury is to ours. We have Kepler to thank for these discoveries, its data analyzed in a number of recent papers including one arguing that about 5 percent of all Kepler stars have systems with tightly packed inner planets. The awkward acronym for such systems is STIP.
Well, maybe it’s not all that awkward, and Kathryn Volk and Brett Gladman (University of British Columbia) have good cause to deploy it in their new paper, which focuses on this topic. They’re wondering why our Solar System lacks planets inside Mercury’s orbit, and they point to the paper I mentioned above (Lissauer et al, 2014) as well as another by Francois Fressin and colleagues that concludes that half of all Kepler stars have at least one planet in the mass range from 0.8 to 2 Earth masses with orbits inside Mercury’s distance from our Sun, which is 0.39 AU, or 58.5 million kilometers.
Image: The Caloris basin and adjacent regions on Mercury. Recent exoplanet discoveries raise the question of why our Solar System lacks planets inside Mercury’s orbit. Can instabilities in the early Solar System help us find the answer, while at the same time explaining some of the planet’s peculiarities? Image credit: JHU/APL.
Taking as an hypothesis that nearly all F, G and K-class stars originally form with planets well within Mercury’s orbital distance, Volk and Gladman ask whether the reason we find systems without such planets today is that instabilities have destroyed these worlds through generations of catastrophic collisions and gradual re-formation, leaving (in our case) Mercury as the surviving relic. It is true that STIPs can be dynamically stable over long time-frames (hence we see the Kepler examples), but the absence of tightly packed inner worlds around many stars is here taken as the result of a ‘metastable planetary arrangement’ that leaves one or no short period planets. The Kepler STIPs we see, then, are those that have survived this process.
The authors use the Kepler data to generate systems similar to those we have uncovered, allowing them to ‘evolve’ computationally to study system dynamics, taking some simulations well beyond the first collision to see how the instabilities multiply. An initial collision often produces second collisions at higher speeds. While low-speed impacts can occur in some systems, producing far smaller amounts of debris and subsequent accretion, a fraction of STIPs experience heavy perturbation that can lead to the destruction of their inner worlds. From the paper:
Our experiments show that instability timescales in these systems are distributed such that equal fractions of the systems go unstable (reach a first planetary collision) in each decade in time (Fig. 2). This logarithmic decay is not unknown in dynamical systems (eg., Holman & Wisdom (1993)) and is presumably related to chaotic diffusion and resonance sticking near the stability boundary. After a brief, relatively stable initial period, the systems hit instability at a rate of ∼20% per time decade, with half of the systems still intact at ∼100 Myr. The exact decay rate may be influenced by our usage of the current Kepler STIPs sample (perhaps the most stable); however if this decay rate held, at ∼5 Gyr 5–10% of STIPs would not yet have reached an instability, in rough agreement with the observed STIPs frequency.
Turning the results on our own Solar System, they find that the orbits of the three outer terrestrial planets (Venus, Earth, Mars) remain unaffected on 500 million year timescales by the presence of additional planets totaling several Earth masses, all of the latter inside a distance of 0.5 AU from the Sun. Dynamical instabilities would have initiated a sequence of collisions among these worlds that left Mercury as the sole survivor. The authors argue that it is possible for the orbits of the outer terrestrial planets to remain unperturbed as the inner planets fall victim to these events.
Various issues are explained by this scenario. A series of collisions concentrates iron into the surviving remnants, which accounts for Mercury’s high density. The authors also ask whether instabilities in the inner system approximately 4 billion years ago could account for the Late Heavy Bombardment (sometimes called the ‘lunar cataclysm’), when Mercury, Venus, Earth and Mars experienced a high number of impacts. From the paper:
Gladman & Coffey (2009) estimated that 10–20% of large (m to 100 km) debris originating near current Mercury would strike Venus, with 1–4% impacting Earth (∼0.1% strikes the Moon). The Earth’s impact rate would peak ∼1–10 Myr after the event and decay on ∼30 Myr timescales as Mercury and Venus absorb most of the debris; this is a plausible match for the cataclysm’s final stages (Cuk et al. 2010). A bottom-heavy size distribution for the 1–100 km debris could explain the recent finding (Minton et al. 2015) that a main-belt asteroid source would produce too many impact basins during the cataclysm.
Such an event might be studied by future sampling missions, for:
STIP debris would likely be mostly silicate-rich mantle material similar but not identical to main-belt asteroid compositions, consistent with cataclysm impactor compositions inferred via cosmochemical means (Joy et al. 2012). The smallest dust (being blown out hyperbolically) could impact the Earth-Moon system. We estimate that 10−11 of the departing dust would strike the Moon, at vimp ∼30 km/s. If any dust or meteoroid projectiles were retained, fragments might be found in regolith breccias compacted during the cataclysm epoch.
This is an interesting model, and the authors point out that it gets us out of the difficulty of assuming an inner protoplanetary disk edge that has to be adjusted to account for Mercury and the lack of worlds interior to its orbit. We have a model that would leave the orbits of the existing terrestrial-class worlds unaffected by the series of collisions and disintegrations that Mercury emerged from, although the recipients of catastrophic amounts of early debris. The model also accounts for the apparent instability of Mercury’s orbit on a 5 to 10 billion year time-frame.
The paper is Volk and Gladman, “Consolidating and Crushing Exoplanets: Did it happen here?,” submitted to Astrophysical Journal Letters (preprint). Thanks to Andrew Tribick for the pointer to this paper. | 0.907385 | 3.964194 |
A population of fast radio bursts at cosmological distances. Video from Swinburne University.
Extragalactic radio bursts are intense bursts of radio emission that have durations of milliseconds and exhibit the characteristic dispersion sweep of radio pulsars.
A TELESCOPE in Puerto Rico has confirmed what Australian astronomers have known for a while: There are mysterious sounds emanating from deep in outer space.
The Arecibo Observatory has picked up split-second bursts of radio waves from beyond the Milky Way, which have excited astronomers from around the world, science website Phys.org reports.
Parkes’ radio telescope in central NSW was the first to discover these curious pulses, but some scientists wrote these off because it was the only facility to report the findings.
But now the Puerto Rico telescope’s international team of astronomers has detected similar intergalactic radio wave bursts.
“Our result is important because it eliminates any doubt that these radio bursts are truly of cosmic origin,” principal investigator for the pulsar survey Victoria Kaspi said.
“The radio waves show every sign of having come from outside our galaxy — a really exciting prospect.”
So what is the source of the unidentified sounds?
This question presents a perplexing mystery for astrophysicists and there is no consensus.
Possible answers include evaporating black holes, the merging of neutron stars or flares from magnetars (neutron stars with powerful magnetic fields).
The cosmic bursts, which last only a few thousandths of a second, are estimated to occur about 10,000 times a day.
“The brightness and duration of this event, and the inferred rate at which these bursts occur, are all consistent with the properties of the bursts previously detected by the Parkes telescope in Australia,” said Laura Spitler, the lead author of a paper on the subject published yesterday in The Astrophysical Journal.
The Arecibo Observatory has the world’s largest and most sensitive radio telescope, with a dish that spans 305m. | 0.861433 | 3.684768 |
Seven terrestrial exoplanets around a nearby star
An international team of astronomers has discovered a compact analogue of our inner solar system about 40 light-years away. Brice-Olivier Demory of the Center of Space and Habitability at the University of Bern, analysed the data collected with NASA’s Spitzer Space Telescope and calculated that the newly detected exoplanets all have masses less or similar to the Earth.
TRAPPIST-1 is the name of the small, ultracool star that is the new hot topic in astronomy and the search for life outside our solar system. Observing the star with telescopes from the ground and space during an extensive campaign, an international team found that there are at least seven terrestrial planets around TRAPPIST-1. Their temperatures are low enough to make possible liquid water on the surfaces, as the researchers report in the journal «Nature». «Looking for life elsewhere, this system is probably our best bet as of today», says Brice-Olivier Demory, professor at the University of Bern’s Center for Space and Habitability and one of the authors of the «Nature» paper.
The configuration of these exoplanets orbiting a dwarf star makes it possible to study their atmospheric properties with current and future telescopes. «The James Webb Space Telescope, Hubble’s successor, will have the possibility to detect the signature of ozone if this molecule is present in the atmosphere of one of these planets,» explains Demory: «This could be an indicator for biological activity on the planet.» But the astrophysicist warns that we must remain extremely careful about inferring biological activity from afar and that everything could be different than expected.
Observing from all over the world and space
A year ago, the astronomers had already detected three Earth-sized planets orbiting the star TRAPPIST-1. The planets pass in front of the star in so called transits and periodically dim the starlight by a small amount. After this discovery the researchers observed the star for months with different telescopes in Chile, Morocco, Hawaii, La Palma and South Africa, and in September 2016, NASA’s Spitzer Space Telescope monitored TRAPPIST-1 for 20 days. Exploiting all the data the astronomers found that the TRAPPIST-1 system is a compact analogue of our inner solar system with at least seven planets.
Bernese computer simulations confirmed
«My task was to make an independent analysis of the Spitzer data as well as a dynamic analysis of the system that allowed to compute the masses of these planets,» explains Demory. He found that some of the detected planets have densities similar to the Earth and most probably a rocky composition. In a paper published in October 2016, Yann Alibert and Willy Benz, both astrophysics professors at the University of Bern as well, had already predicted based on their computer simulations that such planets around dwarf stars should be common.
Earth-like exoplanets orbiting dwarf stars are easier to observe than real Earth-twins around solar-type stars. Since these dwarfs are also much cooler, the temperature zone that allows water to be liquid on the surface of the planet is much closer to the star. And exoplanets that are close to their host star revolve more rapidly and produce more transits in a given timeframe. «About 15 percent of the stars in our neighbourhood are very cool stars like TRAPPIST-1,» says Brice-Olivier Demory: «We have a list of about 600 targets that we will observe in the future.» To monitor the candidate stars in the northern hemisphere the Center for Space and Habitability (CSH) of the University of Bern is leading a consortium that builds a new telescope in Mexico.
Michaël Gillon, Amaury Triaud, Brice-Oliver Demory et al.: «Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1», Nature 22.02.2017, doi:10.1038/nature21360
«Earth-like exoplanets around the dwarf star TRAPPIST-1»
Short talks and panel discussion with Prof. Brice-Olivier Demory, Prof. Yann Alibert, Prof. Kevin Heng, Zoë Lehmann and Science Fiction author Laurence Suhner, who published a short novel about TRAPPIST-1 in Nature.
University of Bern, Thursday, 9 March 2017, 18.30 h
Information and registration:: www.unibe.ch/trappist1 (from Thursday, February 23, 2017) | 0.834569 | 3.7308 |
Could DSCOVR help in the hunt for exoplanets?
Could a space weather satellite be helpful in in the ongoing hunt for exoplanets? It now turns out it just might. According to a team of scientists led by Stephen Kane from the San Francisco State University, the Deep Space Climate Observatory (DSCOVR), launched in February of this year to study space weather, could make a significant contribution to the search for distant alien worlds.
DSCOVR, operated by the National Oceanic and Atmospheric Administration (NOAA), was designed to monitor the solar wind and forecast space weather around Earth. It is equipped with two NASA instruments that are used to observe the Earth in detail: the National Institute of Standards and Technology Advanced Radiometer (NISTAR) and the Earth Polychromatic Imaging Camera (EPIC). EPIC provides high-resolution spectral images of the Earth, whereas NISTAR is designed to measure the reflected and emitted energy from the entire sunlit face of our planet.
According to Kane and his colleagues, data obtained by these instruments provide a unique opportunity to help in the search for extrasolar worlds by monitoring the Earth as if it were an exoplanet. They findings were detailed in a paper published on the arXiv pre-print server.
“It [DSCOVR] can be used to indirectly study exoplanets by allowing us to study how to extract various important planetary parameters,” Kane told Astrowatch.net.
By degrading the data acquired by DSCOVR, the scientists hope to learn what information could be retrieved about the planets orbiting other stars. They assume that if it is possible to obtain basic characteristics of Earth, it could be also applied to exoplanet-searching missions. The scientists demonstrated that using degraded low-resolution images from the EPIC instrument, they were able to determine Earth’s rotation, obliquity, and atmospheric albedo.
“What we are doing is using the data from DSCOVR to learn more about how we can retrieve these parameters for exoplanets by using the Earth as a well-understood planet and degrading the DSCOVR data to what we would expect to acquire from an exoplanet mission. If we can accurately determine the Earth’s parameters from these degraded data, then we can also determine the minimum requirements for an exoplanet imaging mission to be successful,” Kane said.
The researchers managed to extract periodic behavior due to planetary rotation, weather patterns, and surface terrain from the images provided by EPIC. NISTAR was helpful when it comes to atmospheric albedo as it measures the amount of reflected sunlight and the thermal radiation from Earth in the direction toward the Sun.
“Using the combination of the EPIC imager and cavity radiometer to interpret what might be seen by an exoplanet instrument is quite workable. We and other researchers are attempting to use the data in this manner,” Jay R. Herman of NASA’s Goddard Space Flight Center, one of the co-authors of the paper, told SpaceFlight Insider.
The importance of properties such as planetary rotation, albedo, and obliquity is significant because they are crucial to determining planetary surface conditions. Therefore, a complete characterization of exoplanets requires the ability to obtain measurements of these key planetary parameters.
While the DSCOVR spacecraft cannot be used to directly image extrasolar planets as the sensitivity of the detector for the imager is too low, the researchers have shown that it could be very helpful in the future search for alien worlds. Their study regarding the DSCOVR data could provide an effective baseline from which to develop tools that can be useful when obtaining various exoplanet imaging data.
DSCOVR is a partnership between NOAA, NASA, and the U.S. Air Force. NOAA is operating the mission from its NOAA Satellite Operations Facility in Suitland, Maryland.
Tomasz Nowakowski is the owner of Astro Watch, one of the premier astronomy and science-related blogs on the internet. Nowakowski reached out to SpaceFlight Insider in an effort to have the two space-related websites collaborate. Nowakowski's generous offer was gratefully received with the two organizations now working to better relay important developments as they pertain to space exploration. | 0.873521 | 3.258554 |
A Martian crater is providing more proof that the Red Planet may once have supported life, a Stony Brook geochemist and planetary scientist says in a recently published NASA study.
The study led by Assistant Professor Joel Hurowitz offers perhaps the most significant evidence to date that an ancient lake on Mars had all the ingredients of a life-sustaining body of water.
Building on the 2013 discovery that Mars’ Gale crater contained a freshwater lake more than 3 billion years ago, Assistant Professor Joel Hurowitz led a team of 22 international scientists using findings beamed to Earth from NASA’s Curiosity rover to determine that the lake was stratified, meaning that depending on the depth, its water created several co-existing environments where life could flourish, much like the lakes on Earth.
“The diversity of environments in this Martian lake would have provided multiple opportunities for different types of microbes to survive, including those that thrive in oxidant-rich conditions, those that thrive in oxidant-poor conditions, and those that inhabit the interface between those settings,” Hurowitz said. “This type of oxidant stratification is a common feature of lakes on Earth, and now we’ve found it on Mars.”
Hurowitz is an assistant professor in Stony Brook’s Department of Geosciences, as well as the head of one of three laboratories inside the University’s Center for Planetary Exploration (CPEx), which brings students and faculty together to pave the way for future human exploration of our solar system through interdisciplinary study and hands-on science.
The study, titled Redox stratification of an ancient lake in Gale crater, Mars and published in the June 2 edition of Science, uses evidence retrieved by the Curiosity rover from the base of a mountain inside Gale crater. After examining the physical, chemical and mineral characteristics of the mountain’s rock layers, the team was able to not only determine that the ancient lake was stratified, but that ancient Mars itself experienced distinct climate change.
During the time Gale crater held lake water, climate conditions changed from colder and drier to warmer and wetter. This relatively short-term climate change took place within a longer climate evolution, during which Mars transitioned from warm, wet conditions that supported lakes, to the cold, arid planet we see through our telescopes today.
“These results give us unprecedented detail in answering questions about ancient environmental conditions on Mars,” said Curiosity Project Scientist Ashwin Vasavada of NASA’s Jet Propulsion Laboratory. “I’m struck by how these fascinating conclusions on habitability and climate took everything the mission had to offer: a set of sophisticated science instruments, multiple years and miles of exploration, a landing site that retained a record of the ancient environment, and a lot of hard work by the mission team.”
While evidence of life on Mars is still unknown, seeking signs of life there starts with studying the environment and its ability, in present or ancient times, to sustain life. Developments such as these achieved by Hurowitz and all co-authors on the study reinforce NASA’s strategy to use rovers to further investigate Mars.
Hurowitz’s involvement with NASA’s missions to Mars continues as he is also deputy principal investigator for the Planetary Instrument for X-ray Lithochemistry (PIXL), an instrument being developed within Stony Brook’s CPEx that will be part of the upcoming Mars 2020 Rover Mission, which will further explore Mars in search of possible signs of ancient life.
View a selection of press coverage this discovery received:
Nature: Life could have survived in Mars crater
Newsday: LI researcher: Mars crater held fresh water, key to early life
Popular Science: Mars was probably habitable for longer than we thought
Yahoo News UK: Ancient Mars Lake Had Multiple Environments That Might Have Supported Life
The Verge: An ancient Martian lake could have been teeming with lots of kinds of life
New Scientist: Mars rover sees signs of microbe-friendly layers in ancient lake
Space.com: Ancient Mars Lake Had Multiple Environments That Might Have Supported Life
International Business Times: Ancient Lake On Mars Was Stratified, Had Oxygen That Varied Across Depths | 0.83509 | 3.768637 |
How historic Jupiter comet impact led to planetary defense
Twenty-five years ago, humanity first witnessed a collision between a comet and a planet. From July 16 to 22, 1994, enormous pieces of the comet Shoemaker-Levy 9 (SL9), discovered just a year prior, crashed into Jupiter over several days, creating huge, dark scars in the planet's atmosphere and lofting superheated plumes into its stratosphere.
The SL9 impact gave scientists the opportunity to study a new celestial phenomenon. It was also a wake-up call that big collisions still occur in the solar system—after all, if Jupiter was vulnerable, maybe Earth is, too. Had the comet hit Earth instead, it could have created a global atmospheric disaster, much like the impact event that wiped out the dinosaurs 65 million years ago.
"Shoemaker-Levy 9 was a sort of punch in the gut," said Heidi Hammel, who led visible-light observations of the comet with NASA's Hubble Space Telescope and is now the executive vice president at The Association of Universities for Research in Astronomy AURA (which manages astronomers' interface to Hubble). "It really invigorated our understanding of how important it is to monitor our local neighborhood, and to understand what the potential is for impacts on Earth in the future."
Comets, cosmic snowballs of frozen gases, rock and dust that orbit the Sun, are just one type of object that can wreak havoc on planetary bodies. Asteroids—the rocky, airless remnants left over from the formation of our solar system—are another. In honor of World Asteroid Day, June 30, we look back at this historic Shoemaker-Levy 9 event, which taught us the importance of looking out for potential impacts.
Discovering the Comet
Astronomers Carolyn and Eugene Shoemaker and David Levy discovered comet SL9 in March 1993. The Shoemakers were already a well-known comet-discovering astronomical duo, having discovered 32 comets together or separately in their careers. Calculations indicated that the comet, broken up into large pieces (some over a half a mile wide) by the planet's gravity, was orbiting Jupiter and would impact in July 1994.
The news whipped the astronomical community into a frenzy—here was an opportunity to actually observe an impact. Other planets and moons are covered in craters, but we had never seen an impact happen. On Earth, scientists had recently confirmed that many of our own craters were created by impacts rather than volcanic eruptions, like the mile-wide (1.6-kilometer-wide) Meteor Crater in Arizona, and the 93-mile-wide (150-km-wide) Chicxulub Crater in the Gulf of Mexico. The SL9 impact with Jupiter would be an extraordinary opportunity to study how impacts affected a planet.
The world's astronomers had a year to prepare for the impact, so many ground-based telescopes around the world joined the campaign. This effort included NASA's Infrared Telescope Facility (IRTF) which sits atop Maunakea on Hawai'i's Big Island. NASA also ultimately received data from two of its spacecraft, the Galileo spacecraft—which was already on route to Jupiter after launching in 1989—and the Hubble Space Telescope.
"The Shoemaker-Levy 9 impacts brought together comet researchers, Jupiter atmosphere experts, and astronomers, who came together to ask "How are we going to observe this event?"" said Kelly Fast, program manager for NASA's Near Earth Object Observations Program. For the SL9 impacts, Fast was stationed at the IRTF on her first observing run. "Having that notice ahead of time to plan was really essential, because it gave us the opportunity to optimize how these observations might be made to give us the best science."
Astronomers gathered at the IRTF in Hawaii to begin preparing for the impact. The telescope, which was built in the late 1970s to support the Voyager missions to the outer planets, is sensitive to heat, so its images showed enormous bright spots where the comet fragments impacted Jupiter.
"Normally you think of the solar system as static, you don't see these big changes happen all at once," said John Rayner, director of the IRTF, who was on staff at IRTF during the impacts. "But to suddenly see these impacts, these enormous bright spots that appeared on the biggest planet in our solar system, was quite extraordinary."
As amazing as the observations were from the IRTF and numerous ground-based observatories, those telescopes from Earth didn't actually see the impacts happen because they occurred on Jupiter's "night" side. Only as the planet rotated did ground-based telescopes get to see the after-effects of the impact.
But NASA's Galileo spacecraft had a front-row seat for the event. At the time of the impacts, Galileo was on its way to study Jupiter and its moons, and approaching at the right geometry to witness the fragments of SL9 slam into the gas giant. From 238 million kilometers (148 million miles) away, the spacecraft started snapping photos.
The best images, though, came from Hubble, which had recently gotten crucial repairs in its first servicing mission. Above Earth's atmosphere, with its high-resolution camera, Hubble's exquisite image quality allowed scientists to track the plumes growing and collapsing onto the cloud tops of Jupiter. Slowly, as the planet rotated, dark scars were revealed in its atmosphere where the comet fragments had impacted. Astronomers saw expanding waves of dark material, the shapes of the plumes, and details in the explosions' debris fields with unparalleled detail. Hubble press conferences were held at least once a day for the full week so that the public could follow along as new images came in.
Hammel recalls being initially skeptical that Hubble would see anything at all, since the comet was so small compared to the immense gaseous planet. When the images started coming down, she barely slept for days.
"I was astonished, and then I was elated," she said. It was just so remarkable to be involved in a project I knew was going to change our understanding of Jupiter, and change our understanding of impacts in the Solar System."
Scientists around the world observed the aftermath of the 21 fragments that slammed into Jupiter's atmosphere. Each impact lofted material that splashed back into Jupiter's atmosphere, creating debris that acted as markers for scientists on Earth to study Jupiter's winds. Before the event, cloud tracking was the primary way to see how the gas giant's atmosphere transported material around the planet. But material like ammonia and hydrogen cyanide lofted into the stratosphere from deep under Jupiter's uppermost clouds gave scientists a way to track the winds as those molecules were blown around the planet. Even today, scientists can still detect the changes in hydrogen cyanide in Jupiter's atmosphere from the impacts.
Observations were also able to refine basic impact models and tell us more, in general, about how particles are transported around an atmosphere after an impact. Because we can't test impacts in real life—except at very small scales, like shooting a pebble into a block of rock in a laboratory—the SL9 impacts offered scientists a natural experiment with which to study how massive impacts affect a large body like a planet. Studying SL9's impact on Jupiter helped scientists strengthen their models of what might happen if a comet or asteroid struck Earth.
A Wake up Call for Humanity
Before the SL9 impact, the term "planetary defense" didn't exist. These days, there are many teams of scientists tracking near-Earth objects (NEOs): asteroids that come within 30 million miles (50 million kilometers) of Earth's orbit. But back in the mid 1990s, only a few teams (including the Shoemakers) were looking for asteroids in the inner solar system.
In the year before the impact, a study team in the Air Force led by Lindley Johnson, now NASA's first (and so far, only) Planetary Defense Officer, had been trying to convince their leadership that finding and tracking NEOs should be a part of the Air Force's space situational awareness mission. When SL9 was found to be on a collision course with Jupiter, Johnson's research became a major element in the Air Force's study of future space capabilities.
By 1998, Congress—influenced by Eugene Shoemaker and other scientists advocating for NEO research and with Hubble images of Jupiter's devastation fresh in their minds—officially directed NASA to find 90% of the asteroids in our celestial neighborhood 1 kilometer or larger. By the end of 2010, NASA had achieved that goal. Now, the agency is working to identify at least 90% of the asteroids between 450-3,000 feet (140-1,000 meters) wide, and they're about a third of the way there.
"The Shoemaker-Levy 9 event showed us that we are vulnerable to impacts in the present day, not just in the distant past," said Johnson. "These impact events occur in the Solar System right now, and we should do our best to find hazardous objects before they are of imminent danger of impacting Earth." | 0.926647 | 3.988815 |
The mass inflow and outflow rates of the Milky Way
According to the most widely accepted cosmological models, the first galaxies began to form between 13 and 14 billion years ago. Over the course of the next billion years, the cosmic structures now observed first emerged. These include things like galaxy clusters, superclusters and filaments, but also galactic features like globular clusters, galactic bulges, and supermassive black holes (SMBHs).
However, like living organisms, galaxies have continued to evolve ever since. In fact, over the course of their lifetimes, galaxies accrete and eject mass all the time. In a recent study, an international team of astronomers calculated the rate of inflow and outflow of material for the Milky Way. Then the good folks at Astrobites gave it a good breakdown and showed just how relevant it is to our understanding of galactic formation and evolution.
The study was led by ESA astronomer Dr. Andrew J. Fox and included members from the Space Telescope Science Institute's (STScI) Milky Way Halo Research Group, the ESA's Association of Universities for Research in Astronomy (AURA), and multiple universities. Based on previous studies, they examined the rate at which gas flows in and out of the Milky Way from surrounding high-velocity clouds (HVC).
Since the availability of material is key to star formation in a galaxy, knowing the rate at which it is added and lost is important to understanding how galaxies evolve over time. And as Michael Foley of Astrobites summarized, characterizing the rates at which material is added to galaxies is crucial to understanding the details of this "galactic fountain" model.
In accordance with this model, the most massive stars in a galaxy produce stellar winds that drive material out of the galaxy disk. When they go supernova near the end of their lifespans, they similarly drive most of their material out. This material then infalls back into the disk over time, providing material for new stars to form.
"These processes are collectively known as stellar feedback, and they are responsible for pushing gas back out of the Milky Way," said Foley. "In other words, the Milky Way is not an isolated lake of material; it is a reservoir that is constantly gaining and losing gas due to gravity and stellar feedback."
In addition, recent studies have shown that star formation may be closely related to the size of the supermassive black hole (SMBH) at a galaxy's core. Basically, SMBHs put out a tremendous amount of energy that can heat gas and dust surrounding the core, which prevents it from clumping effectively and undergoing gravitational collapse to form new stars.
As such, the rate at which material flows in and out of a galaxy is key to determining the rate of star formation. To calculate the rate at which this happens for the Milky Way, Dr. Fox and his colleagues consulted data from multiple sources. Dr. Fox told Universe Today via email:
"We mined the archive. NASA and ESA maintain well-curated archives of all Hubble Space Telescope data, and we went through all the observations of background quasars taken with the Cosmic Origins Spectrograph (COS), a sensitive spectrograph on Hubble that can be used to analyze the ultraviolet light from distant sources. We found 270 such quasars. First, we used these observations to make a catalog of fast-moving gas clouds known as high-velocity clouds (HVCs). Then we devised a method for splitting the HVCs into inflowing and outflowing populations by making use of the Doppler shift."
In addition, a recent study showed that the Milky Way experienced a dormant period roughly 7 billion years ago, which lasted for about 2 billion years. This was the result of shock waves that caused interstellar gas clouds to become heated, which temporarily caused the flow of cold gas into our galaxy to stop. Over time, the gas cooled and began flowing in again, triggering a second round of star formation.
After looking at all the data, Fox and his colleagues were able to place constraints on the rate of inflow and outflow for the Milky Way:
"After comparing the rates of inflowing and outflowing gas, we found an excess of inflow, which is good news for future star formation in our galaxy, since there is plenty of gas that can be converted into stars and planets. We measured about 0.5 solar masses per year of inflow and 0.16 solar masses per year of outflow, so there's a net inflow."
However, as Foley indicated, HVCs are believed to live for periods of only about 100 million years or so. As a result, this net inflow cannot be expected to last indefinitely. "Finally, they ignore HVCs that are known to reside in structures (such as the Fermi Bubbles) that don't trace the inflowing or outflowing gas," he adds.
Since 2010, astronomers have been aware of the mysterious structures emerging from the center of our galaxy known as Fermi Bubbles. These bubble-like structures extend for thousands of light-years and are thought to be the result of SMBH's consuming interstellar gas and belching out gamma rays.
However, in the meantime, the results provide new insight into how galaxies form and evolve. The study also bolsters the new case made for "cold flow accretion," a theory originally proposed by Prof. Avishai Dekel and colleagues from the Hebrew University of Jerusalem's Racah Institute of Physics to explain how galaxies accrete gas from surrounding space during their formation.
"These results show that galaxies like the Milky Way do not evolve in a steady state," Dr. Fox summarized. "Instead they accrete and lose gas episodically. It's a boom and bust cycle: When gas comes in, more stars can be formed, but if too much gas comes in, it can trigger a starburst so intense that it blows away all the remaining gas, shutting off the star formation. Thus, the balance between inflow and outflow regulates how much star formation occurs. Our new results help to illuminate this process."
Another interesting takeaway from this study is the fact that what applies to our Milky Way also applies to star systems. For instance, our solar system is also subject to the inflow and outflow of material over time. Objects like "Oumuamua and the more recent 2I/Borisov confirm that asteroids and comets are kicked out of star systems and scooped up by others regularly.
But what about gas and dust? Is our solar system and (by extension) planet Earth losing or gaining weight over time? And what could this mean for the future of our system and home planet? For example, astrophysicist and author Brian Koberlein addressed the latter issue in 2015 on his website. Using the then-recent Gemini meteor shower as an example, he wrote:
"In fact, from satellite observations of meteor trails, it's estimated that about 100-300 metric tons (tonnes) of material strikes Earth every day. That adds up to about 30,000 to 100,000 tonnes per year. That might seem like a lot, but over a million years, that would only amount to less than a billionth of a percent of Earth's total mass."
However, as he goes on to explain, Earth also loses mass on a regular basis through a number of processes. These include radioactive decay of material in the Earth's crust, which leads to energy and subatomic particles (alpha, beta and gamma-rays) leaving our planet. A second is atmospheric loss, in which gases like hydrogen and helium are lost to space. Together, these add up to a loss of about 110,000 tonnes per year.
On the surface, this would seem like a net loss of about 10,000 or more tonnes annually. What's more, microbiologist/science communicator Dr. Chris Smith and Cambridge physicist Dave Ansell estimated in 2012 that the Earth gains 40,000 tonnes of dust a year from space, while it loses 90,000 a year through atmospheric and other processes.
So it may be possible that Earth is getting lighter at a rate of 10,000 to 50,000 tonnes a year. However, the rate at which material is being added is not well constrained at this point, so it is possible that we might be breaking even (though the possibility that Earth is gaining mass seems unlikely). As for our solar system, the situation is similar. On the one hand, interstellar gas and dust flows in all the time.
On the other hand, our sun—which accounts for 99.86 percent of the solar system's mass—is also shedding mass over time. Using data gathered by NASA's MESSENGER probe, a team of NASA and MIT researchers concluded that the sun is losing mass due to solar wind and interior processes. According to Ask an Astronomer, this is happening at a rate of 1.3245 x 1015 tonnes a year, even though the sun is expanding simultaneously.
That's a staggering number, but the sun has a mass of about 1.9885×1027 tonnes. So it won't be winking out anytime soon. But as it loses mass, its gravitational influence on Earth and the other planets will diminish. However, by the time our sun reaches the end of its main sequence, it will expand considerably and could very well swallow Mercury, Venus, Earth and even Mars completely.
So while our galaxy may be gaining mass for the foreseeable future, it looks like our sun and Earth itself are slowly losing mass. This should not be seen as bad news, but it does have implications in the long run. In the meantime, it's kind of encouraging to know that even the oldest and most massive objects in the universe are subject to change like living creatures.
Whether we're talking about planets, stars, or galaxies, they are born, they live and they die. And in between, they can be trusted to put on or lose a few pounds. The circle of life, played out on the cosmic scale. | 0.926351 | 4.111609 |
Fr.: magnitude apparente
A measure of a star's observed brightness (opposed to → absolute magnitude); symbol m. It depends on the star's → intrinsic brightness, its distance from the observer, and the amount of → interstellar absorption. The brightest star → Sirius has an apparent magnitude of -1.46, while the weakest stars visible with the naked eye in the most favorable observation conditions have magnitudes of about +6.5. The stars of magnitudes less than +23 are measured by professional observatories, whereas those of magnitudes less than +30 by a telescope such as the → Hubble Space Telescope (M.S.: SDE). | 0.838603 | 3.138821 |
SETI and the Search for Life
Excerpts from the written testimony submitted by Christopher F. Chyba, SETI Institute, to the "Life in the Universe" hearings held by the House Subcommitee on Space and Aeronautics on July 12, 2001.
Over the past decade, there has been a rebirth in the scientific study of life elsewhere in the Universe – and for very good reasons. We’ve learned that organic molecules – the sort of carbon-based molecules all life on Earth is based upon – are abundant not only in our own solar system, but throughout the space between the stars. They are likely to be present in many other solar systems as well.
|Europa is one of the primary focuses in the search for life in the universe.
We’re finally beginning to discover other planets are out there. While we can’t yet detect solar systems like our own, at a minimum we now know that planets are not rare. My own suspicion is that just about every kind of solar system that could be out there, will be out there. Our solar system will prove to be neither common nor rare, but instead just one example of a wide variety of possibilities.
Within our solar system we have more and more evidence of other worlds with liquid water, which is an essential ingredient for life as we know it. Water seems to have flowed on the martian surface in the geologically recent past. There is now strong, though still indirect, evidence for a second ocean in our solar system beneath the ice of Jupiter’s moon Europa – the evidence from the Voyager and especially Galileo spacecraft missions points towards an ocean whose volume is nearly twice that of all the Earth’s oceans combined. If we want to look for life in our solar system, the importance of Europa can hardly be exaggerated. Perhaps even more astonishing, there is now evidence for subsurface oceans under the ice of two of Jupiter’s other large moons, Ganymede and Callisto. We’ve gone from thinking that Earth’s ocean is unique to thinking that our ocean may be one of many.
We’ve also learned that Earth harbors a deep subsurface biosphere, and that the mass of microorganisms beneath our feet, reaching down miles underground, likely equals or exceeds the mass of all the organisms on Earth’s surface. This is a dramatically different picture of terrestrial life than the one we experience daily, and makes speculation about subsurface life on Europa or vestigial life on Mars seem much more credible. Our understanding of the Earth helps shape our thinking about other worlds, and vice-versa.
The prospects for finding life elsewhere seem better than ever. But we need to remember that prospects are not proof, and it may be possible that Earth is the only planet where life exists. That would seem extraordinary, and I doubt it’s likely in a galaxy with 400 billion stars, but the honest answer is that we don’t know yet. But we can use scientific exploration to try and find out.
The SETI (Search for ExtraTerrestrial Intelligence) Institute is a private scientific institute dedicated to research, education, and public outreach. Its mission is to use scientific methods to investigate the origin, nature, and prevalence of life in the Universe. SETI Institute scientists investigate everything from the formation of stars and planets to the development of advanced technical civilizations. Research topics include, for example, interstellar organic chemistry, planet formation, the search for extrasolar planets, the chemistry of life’s origins, microbiology and life in extreme environments, planetary climatology and habitability, Mars and Europa, and the role of asteroid and comet impacts in the history of life on Earth.
By understanding the many factors that make a world habitable for complex life, we can put the search for extraterrestrial civilizations into context. For instance, by learning more about the history of life on Earth, we can try to track the events that have led to the development of intelligence. But we don’t know whether the evolution of human-style technical intelligence is something that will prove to be incredibly rare or common. Finding evidence for such intelligence elsewhere would have a profound effect on humanity.
|The Very Large Array (VLA) radio telescope is used by SETI to listen for artificially produced radio signals from outside our solar system.
One of SETI’s best-known projects is the search for artificially produced radio signals in the vicinities of nearby stars. Many natural objects in the Universe produce radio waves (including our own Sun), but no naturally occurring source in the Universe is known that produces bandwidths thinner than 300 Hz (Hertz, a measure of frequency equal to one cycle per second). So the first criterion of an artificial signal is a very narrow spectral bandwidth. In fact, we look for bandwidths below about 1 Hz in width. This wavelength of the signal is extremely precise and highly efficient, because narrow-band signals pack a lot of energy into a small amount of spectral space. Any object producing extremely narrow bandwidth signals is either artificial or represents some entirely unknown astrophysical phenomenon.
To give some sense of how sensitive our radio searches are, it’s worth mentioning that we have for many years tested our system by using the signal transmitted by the Pioneer 10 spacecraft, launched from Earth in 1972 and now traveling beyond our Solar System. Pioneer 10 is at a distance of 6 billion miles from Earth and broadcasting with a power of a few watts – much less than a light bulb in your house, but about the power of a small flashlight. It takes more than 10 hours for Pioneer 10’s radio signal, traveling at the speed of light, to reach Earth. Because Pioneer 10 really is an extraterrestrial (even extra-Solar System!) artificial source, it provides an excellent test for our system – and it comes in loud and clear.
Since SETI gets so much media attention, it is easy to get the mistaken impression that SETI researchers have searched the galaxy thoroughly for alien radio signals, yet have found nothing. But in fact we’ve only examined about one-billionth of the galaxy so far. We’re looking at the thousand nearest Sun-like stars that lie within about 150 light years of Earth. This is only a tiny fraction of the entire Milky Way galaxy, which contains some 400 billion stars and is 100,000 light years across
Even if alien signals are detected someday, it is unlikely that an interstellar dialogue would occur, except over extremely long timescales. If we detect a signal from a star 100 light years away, that message was sent 100 years ago – so that two-way communication would require 200 years for each reply.
It is quite possible that, while we could detect the signal’s carrier wave, we would not have the sensitivity to detect whatever message might be carried by that wave. Even if we could, it is difficult to predict how difficult decipherment might prove to be. A possible analogy could be the decipherment of inscriptions left by the ancient Maya, which proved extremely difficult. Even in this case, we had the advantage of being able to apply linguistic knowledge from extant Maya languages. And of course, we share a genetic and sociological heritage with any other human culture that we will not share with an extraterrestrial civilization. Nevertheless, if we detect an extraterrestrial radio signal, we will at least have in common the physics and mathematics that made that transmission possible, and this could be a starting point.
|The goals of the SETI Institute fit naturally with the goals of NASA’s astrobioligy program.
The scientific Search for Extraterrestrial Intelligence enjoys great public interest. We see this every day at the Institute, where we serve as a resource for the press covering topics across the range of life in the Universe studies. Our web site (www.seti.org) receives about two million hits per month. We view this kind of interest as a tremendous opportunity to teach students and the general public about science and the scientific method -that blend of openness to new ideas coupled with an insistence on hard evidence and skeptical analysis of data.
The goals of the SETI Institute fit naturally with the fundamental questions at the heart of NASA’s Astrobiology program: "Does life exist elsewhere in the Universe, or are we alone?" and "What is life’s future on Earth and beyond?" Whether any other intelligent civilizations exist elsewhere is a natural extension of these questions. The scientific investigation of these questions is exciting, inspiring, and eventually may help humanity find its place in the Universe.
This article has been translated in to Portuguese.
Related Web Pages
Life in the Universe (SETI Institute)
SETI Institute Online (SETI Institute)
NASA Orgins (NASA)
The Search for Extrasolar Planets (exoplanets.org) | 0.871014 | 3.680165 |
NASA's Hubble Space Telescope has seen planet-size cannonballs of hot gas whipping through the space near a dying star, but the origin of these plasma balls remains a mystery.
The high-speed blobs, each double the mass of Mars and twice as hot as the surface of the sun, are moving so fast in space that they would take only half an hour to go between the Earth and the moon (238,900 miles, or 384,472 kilometers), according to a statement from NASA's Jet Propulsion Laboratory. The observations suggest that these balls of fire have been appearing every 8.5 years for at least the last four centuries, the statement said.
The gas balls were observed near a red giant called V Hydrae that is about 1,200 light-years away from Earth. Red giants are stars that are nearing the end of their fuel supplies and have begun to puff up and expand. While the fireballs could not have been ejected by the star, it could be that an unseen companion star is responsible for the chaos, according to a new study of this cosmic firing squad. [Celestial Photos: Hubble Space Telescope's Latest Cosmic Views]
"According to this [new] theory, the companion would have to be in an elliptical orbit that carries [the companion] close to the red giant's puffed-up atmosphere every 8.5 years," according to the statement. "As the companion enters the bloated star's outer atmosphere, it gobbles up material. This material then settles into a disk around the companion, and serves as the launching pad for blobs of plasma."
If scientists can discover where these balls come from, it could also explain other weird shapes seen in the cloud of gas around dying stars, some of which have been difficult for scientists to explain, the statement said.
"We knew [V Hydrae] had a high-speed outflow, from previous data, but this is the first time we are seeing this process in action," said lead author on the new work Raghvendra Sahai, a research scientist at NASA's Jet Propulsion Laboratory in California, in the statement. "We suggest that these gaseous blobs produced during this late phase of a star's life help make the structures seen in planetary nebulae."
The new study used Hubble's observations of V Hydrae that took place between 2002 and 2004, and 2011 and 2013. Supplemental observations were performed by the Submillimeter Array in Hawaii, which looked at the star in submillimeter wavelengths and found knotty structures that may have been produced by blobs sent out 400 years ago, the statement said.
Astronomers had previously speculated that the knotty structures were actually jets of material that emerge from structures called accretion disks, or disks of material that is accelerating around a star. While red giants do not have accretion disks, their companion stars might. Sahai said that the model proposed in the new paper "provides the most plausible explanation" for what the team observed.
The observations showed another surprise: These clumps aren't fired in the same direction every 8.5 years, possibly because of wobbles in the companion's accretion disk, the statement said. V Hydrae is obscured every 17 years, which could happen when one of the blobs passes in front of the star from Earth's perspective.
"This discovery was quite surprising, but it is very pleasing as well because it helped explain some other mysterious things that had been observed about this star by others," Sahai said.
The results were recently published in The Astrophysical Journal. | 0.894648 | 3.89548 |
The Very Large Telescope Interferometer (VLTI) is unique globally and will continue to be the optical telescope with the highest angular resolution in the southern hemisphere, even as we move into the ELT era. It’s a very powerful facility, able to either combine light from its four 1.8 m Auxiliary Telescopes, or the four 8.2 m Unit Telescopes, with separations of up to 130 m or so. It has a diverse set of instruments covering a wide range of wavelengths, spectral resolutions, and science cases — from resolving the surfaces of giant stars all the way to studying the environments around black holes in the centres of galaxies including our own Milky Way.
For our science, however, spatial resolution was key — our goal was to measure the angular diameters of bright nearby stars to the 1% level (or better!). You might ask though: why use such an advanced facility as a simple measuring tape? There are many reasons! By combining an angular diameter with a bolometric flux through the black body relation (with fluxes obtained through some combination of precision photometry and spectroscopy, or photometry alone), you can obtain the effective temperature of your star to an accuracy and precision not accessible to other techniques. Add a parallax into the mix from the Gaia satellite, and you can work out a stellar radius. With these two measurements you can investigate the environments of planets around your stars, add complementary information to asteroseismic targets, as well as use the stars as temperature standards for spectroscopic surveys. Such information also lets you constrain theoretical models, plus test or build upon empirical relations, letting us understand more distant stars through our knowledge of those closer and more well studied. Moving to larger scales yet again, surface brightness relations which relate angular size to stellar colour are built from such precision measurements and underpin our extragalactic distance scales based on certain standard candles. To these ends, observing a diverse array of stars in temperature, gravity, and metallicity space is critical to ensuring our understanding of stars isn’t a narrow one.
We used the four 1.8 m Auxiliary Telescopes plus PIONIER, the shortest-wavelength (and thus highest spatial resolution) beam combiner on the VLTI to measure the angular diameters of 16 southern stars: 6 dwarfs, 5 sub-giants, and 5 giants (Figure 1 below, see Rains et al. 2020). Ten of these stars had no previous interferometric measurements, and the other six serve as a useful check on cross interferometer/beam-combiner consistency (this latter point is important for such a fundamental technique!). Our smallest star, HR7221, was only a tad larger in angular diameter than our coin from before and was close to the resolution limit of the facility. On the other hand our largest star, λ Sgr, was a factor of four larger and big enough for us to resolve the effects of limb darkening at different wavelengths.
The VLTI is the only telescope capable of this science in the southern hemisphere, and given the southerly declination of most of our stars, the only telescope capable of resolving them at all. The Australia ESO Strategic Partnership is critical in giving Australian researchers access to such a powerful facility, enabling Australian astronomers to do interferometry across all wavelengths. | 0.833383 | 3.995682 |
These new images from NASA’s Dawn spacecraft show the full range of different crater shapes that can be found at Ceres’ surface: From shallow, flattish craters to those with peaks at their centers.
Dwarf planet Ceres continues to puzzle scientists as NASA’s Dawn spacecraft gets closer to being captured into orbit around the object. The latest images from Dawn, taken nearly 29,000 miles (46,000 kilometers) from Ceres, reveal that a bright spot that stands out in previous images lies close to yet another bright area.
“Ceres’ bright spot can now be seen to have a companion of lesser brightness, but apparently in the same basin. This may be pointing to a volcano-like origin of the spots, but we will have to wait for better resolution before we can make such geologic interpretations,” said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles.
Using its ion propulsion system, Dawn will enter orbit around Ceres on March 6. As scientists receive better and better views of the dwarf planet over the next 16 months, they hope to gain a deeper understanding of its origin and evolution by studying its surface. The intriguing bright spots and other interesting features of this captivating world will come into sharper focus.
“The brightest spot continues to be too small to resolve with our camera, but despite its size it is brighter than anything else on Ceres. This is truly unexpected and still a mystery to us,” said Andreas Nathues, lead investigator for the framing camera team at the Max Planck Institute for Solar System Research, Gottingen, Germany.
Dawn visited the giant asteroid Vesta from 2011 to 2012, delivering more than 30,000 images of the body along with many other measurements, and providing insights about its composition and geological history. Vesta has an average diameter of 326 miles (525 kilometers), while Ceres has an average diameter of 590 miles (950 kilometers). Vesta and Ceres are the two most massive bodies in the asteroid belt, located between Mars and Jupiter.
Dawn’s mission is managed by JPL for NASA’s Science Mission Directorate in Washington. Dawn is a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK, Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team. | 0.861612 | 3.683411 |
It’s possible that some extraterrestrials were at the most recent Astronomy on Tap Seattle gathering, at which we explored the possibility of life on Mars and looked at exciting new techniques for capturing images of exoplanets.
We have met the Martians and they are us—maybe
“Are we all Martian-Americans? We still don’t know,” said Bob Abel, a professor of applied physics at Olympic College and collaborator with the University of Washington’s Large Synoptic Survey Telescope Group. Abel gave a talk titled, “Where Are the Martians?” at Astronomy on Tap Seattle April 26.
Giving a quick geological and topographical history of Mars, Abel said that the Red Planet is just one-half the diameter of Earth, and thus has just one-eighth the volume of Earth, so Mars cooled off pretty quickly.
“During the early formation of the solar system, it would have cooled to the point where liquid water could exist on its surface before the Earth got to that point,” Abel said, adding that it’s clear that water was once abundant on Mars. The rovers Spirit and Curiosity both landed in craters that used to be lakes, and Opportunity set down on the edge of what scientists think was once a salty sea.
In addition, Abel said that Spirit found opaline silica in Gusev Crater on Mars.
“The place where you find this on Earth is near geysers and hydrothermal vents,” Abel said. You’ll find heat, water, and minerals around these vents. “You’ve got all the stuff for life, and you find the most primitive life clustered around these on Earth.”
The surface of Mars is awfully barren now, but life could have conceivably existed there in the distant past. Scientists have found meteorites from Mars on Earth, and inside some of those meteorites they’ve found structures that look like nanobacteria. The debate continues over whether these are biological or not.
“It’s still somewhat up in the air, but it’s tantalizing evidence,” Abel said. “The question still remains, did life start earlier on Mars, since it was capable of being inhabited? And by the time Earth was habitable, did meteorites come to Earth and start life on Earth?”
The investigation continues.
As for present-day Mars, while the surface appears devoid of life, we may find something if we dig a little deeper. Abel said that Curiosity detects occasional outbursts of methane on Mars. He pointed out that most methane on Earth is created by biology.
“I’m personally rooting for flatulence, but we don’t know yet what’s causing it,” he laughed. But, through measurements made by many different Mars orbiters, we’ve learned that the planet’s outer core is molten. So beneath the surface there is heat, water, hydrocarbons, and soil: everything life wants. Abel recalled a talk last year by Penelope Boston, head of the NASA Astrobiology Institute.
“She can’t see how life doesn’t exist below the surface of Mars,” Abel said.
Snapshots of exoplanets
Getting photographs of exoplanets—planets orbiting far-away stars—is a relatively new field within astronomy. The first such images were captured just eight years ago or so. Benjamin Gerard said the technology and capabilities within the field are advancing rapidly. Gerard, a doctoral student in physics and astronomy at the University of Victoria in British Columbia, uses the Gemini Planet Imager to trick out pictures of planets near stars that are many light years away. These photos can be useful for figuring out the components of a planet’s atmosphere and whether it has oceans and continents.
Gerard said the main challenges in exoplanet imaging are resolution and contrast. He explained that the key to good resolution is adaptive optics. If you’ve looked through a telescope you have likely had nights when the objects you observe appear to be wiggling around because of atmospheric turbulence. Gemini corrects for this with adaptive optics.
Light from the object hits a deformable mirror as well as a component called a wave-front sensor. The sensor measures the amount of turbulence, sends the information to the mirror’s actuators, which can correct for the aberration.
“The mirror deforms once every millisecond,” Gerard said. “This aberration gets corrected and is constantly re-focused onto the camera. Once it reaches that point this image that is very turbulent suddenly becomes much more stable and we can get much better resolution.”
Gerard said this is a plus for ground-based telescopes.
“With this technique, we can basically take a ten-meter telescope and make it like we were in space,” he said. “With adaptive optics we actually do better than any space telescope in resolution.”
The problem of contrast is apparent to anyone who has visited social media, which is full of bad-contrast photos. Especially common are pics of people posed in front of windows. Often the people appear as silhouettes because the light from the window is way brighter. While exoplanets don’t pose in front of cosmic windows, contrast is a huge problem when it comes to getting the images.
“A planet like Earth is about ten billion times dimmer than it’s host star,” Gerard pointed out. Using a coronagraph helps block out the light of the star and remove its glare from the image. They also use a technique called angular differential imaging to overcome aberrations within the instruments. This is a little bit counter-intuitive to the amateur astrophotographer who typically uses an instrument rotator during long exposures to compensate for the apparent motion of objects caused by the rotation of the Earth.
“For exoplanet imaging this is actually helpful, so we turn off the instrument rotator and the planet appears to rotate with respect to the view of the fixed telescope instrumental aberrations,” Gerard said. “We can distinguish one from the other.” Computer algorithms can later put images made in this way back together to create even greater contrast.
Gerard hopes they’ll be able to do even better in the near future. The Wide Field Infrared Survey Telescope (WFIRST) is scheduled to launch in the mid-2020s. It will have a deformable mirror that should have the capability to image smaller planets like Earth.
“This is many orders of magnitude better than we can do on ground-based telescopes, because on a space telescope you’re much more stable,” Gerard said. “On the Hubble Space Telescope now we can’t reach this sort of contrast because there is no deformable mirror.”
Since Gerard gave the talk NASA announced an independent review of WFIRST that could change its timeline and instrumentation. | 0.832179 | 3.468117 |
The European Space Agency’s PLATO mission hunting for habitable exoplanets has been given the green light to move from blueprint into construction.
It was previously selected in 2014 as part of the ESA’s Cosmic Vision Programme, but the launch date has been pushed out two years from 2024 to 2026.
The goal is to detect Earth-size planets or super-Earths orbiting around stars in the habitable zone – an area with conditions that might support liquid water and an atmosphere.
The project is led by astrophysicists at the University of Warwick in the UK. Don Pollacco, professor of Physics at Warwick University, said: “The launch of PLATO will give us the opportunity to contribute to some of the biggest discoveries of the next decade answering fundamental questions about our existence, and could eventually lead to the detection of extra-terrestrial life.”
In all, 34 small wide-field telescopes are expected to be launched in 2026. Cameras onboard will use transit photometry, a popular method of detecting planets by analyzing the starlight. If the brightness falls periodically, there’s a good chance that it’s caused by a planet crossing the star and partially blocking its light. It’ll give researchers a way to estimate the size of the planet and compare it to Earth’s radius.
To estimate other properties, such as mass, the radial velocity method or Doppler spectroscopy is used. The star’s position will shift slightly due to the tug of a nearby exoplanet companion, and the movement shifts the wavelengths of the light seen through a spectroscope.
The researchers hope to identify promising habitable planets for follow-up observations that will help them probe its atmosphere.
Now that the mission has been granted a green light, industry leaders will be given a chance to make bids to build components of the space telescopes and its software platform.
NASA’s Kepler space telescope was on a similar mission, and scientists recently finished sorting possible exoplanets into a catalog. They found 219 possible candidates, and ten of them are about the size of Earth and lie in the habitable zone, meaning we are now aware of over 4,000 exoplanets in total.
It’s still unknown if any of those planets have the right conditions to support life. ®
Sponsored: Webcast: Simplify data protection on AWS | 0.876758 | 3.389951 |
Uranus is one of the 4 giant planets in the solar system, in the sub-category of ice giants with Neptune. Its atmosphere is essentially made up of hydrogen (83%) and helium (15%), with smaller amounts of methane (2%) and ammonia (0.001%).
The planet’s spin axis is tilted more than 90°, such that it ‘cartwheels’ on its side with one of its poles facing the Sun for 42 years (half of its orbit around the Sun).
Uranus’ core is the same size as Earth’s and composed of rocks rich in silicates and iron-nickel. It is surrounded by a mantle of ice, ammonia and methane.
The atmosphere is made up chiefly of hydrogen and helium, with bands of clouds at different altitudes.
Uranus also has a system of 13 very dark rings composed of rocks and dust.
Credits: NASA/ESA/M. Showalter/SETI Institute.
Uranus planetary data
- Mean diameter: 51,118 km
- Mass (Earth = 1): 14.5, i.e. 86.8.1021 t
- Mean density: 1,270 kg/m3
- Gravity at equator (Earth = 1): 0.904, i.e. 8.87 m/s2
- Mean distance from Sun (Earth-Sun = 1 AU): 19.2 AU, i.e. 2,872.5 million km
- Tilt of spin axis: 97.8°
- Rotation period (day cycle): 17.24 hrs, retrograde, i.e. 17 hrs 14 min
- Revolution period around Sun: 84.02 Earth years, i.e. 30,687 Earth days
- Cloud top temperature: –220°C
- Moons: 27
- Rings: 13
The Uranian system
Observations by the Voyager 2 probe, the Hubble Space Telescope and astronomers from Earth have identified 27 known moons in the Uranian system.
The two largest moons are Titania and Oberon, both spanning more than 1,500 km.
Titania is Uranus’ largest moon and the 8th largest in the solar system. It has giant trenches and cliffs, and possibly a very tenuous carbon dioxide atmosphere.
Oberon is a mixture of ice and rock, with a dark reddish surface. | 0.903804 | 3.570369 |
Quarter* ♓ Pisces
Moon phase on 8 June 2053 Sunday is Waning Gibbous, 21 days old Moon is in Pisces.Share this page: twitter facebook linkedin
Previous main lunar phase is the Full Moon before 7 days on 1 June 2053 at 11:02.
Moon rises in the evening and sets in the morning. It is visible to the southwest and it is high in the sky after midnight.
Moon is passing about ∠6° of ♓ Pisces tropical zodiac sector.
Lunar disc appears visually 4.1% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1815" and ∠1890".
Next Full Moon is the Buck Moon of July 2053 after 22 days on 1 July 2053 at 02:01.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 21 days old. Earth's natural satellite is moving from the middle to the last part of current synodic month. This is lunation 660 of Meeus index or 1613 from Brown series.
Length of current 660 lunation is 29 days, 7 hours and 8 minutes. It is 33 minutes longer than next lunation 661 length.
Length of current synodic month is 5 hours and 36 minutes shorter than the mean length of synodic month, but it is still 33 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠336.2°. At the beginning of next synodic month true anomaly will be ∠352.3°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
4 days after point of apogee on 3 June 2053 at 22:38 in ♑ Capricorn. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 8 days, until it get to the point of next perigee on 16 June 2053 at 21:48 in ♊ Gemini.
Moon is 394 943 km (245 406 mi) away from Earth on this date. Moon moves closer next 8 days until perigee, when Earth-Moon distance will reach 357 537 km (222 163 mi).
13 days after its ascending node on 26 May 2053 at 04:22 in ♍ Virgo, the Moon is following the northern part of its orbit for the next day, until it will cross the ecliptic from North to South in descending node on 9 June 2053 at 18:30 in ♓ Pisces.
13 days after beginning of current draconic month in ♍ Virgo, the Moon is moving from the beginning to the first part of it.
5 days after previous South standstill on 3 June 2053 at 04:36 in ♑ Capricorn, when Moon has reached southern declination of ∠-18.483°. Next 8 days the lunar orbit moves northward to face North declination of ∠18.495° in the next northern standstill on 16 June 2053 at 21:27 in ♊ Gemini.
After 7 days on 16 June 2053 at 10:51 in ♊ Gemini, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.149687 |
What We Learned from Dawn
NASA’s Dawn mission, which launched in 2007, sought to characterize the processes that dominated early solar system evolution. To build a detailed picture of those early days, Dawn visited two time capsules of the solar system—Vesta and Ceres, the largest bodies of the main asteroid belt. Studying these planet-like worlds, intact survivors from the earliest part of solar system history, gave scientists insight into the original building blocks of the solar system. And by mapping the bodies from orbit, the spacecraft was able to provide key pieces of data that scientists couldn’t get using telescopes or brief flybys.
What did we learn from Dawn during its groundbreaking, 11-year mission?
Dawn showed us that location was key to how the early system organized and evolved.
Dawn highlighted how important place of birth was for bodies in the early days of our solar system, which formed 4.6 billion years ago.
Understanding the environment where the smaller planets formed is crucial to understanding their destiny, Dawn showed us. Early solar system and planetary migration models now must account for the findings Dawn has made over the last seven years.
Vesta, which likely formed in the inner solar system and stayed there, evolved in many ways like the rocky planets of the inner solar system. Dawn’s mapping of Vesta’s craters revealed that the northern hemisphere of Vesta is an ancient surface that had more large impacts than expected based on pre-Dawn models of asteroids in the main belt. This suggests that there were more large objects early on and tells us that “planetesimals”—the types of smaller bodies that could evolve into planets—were born big, rather than being built of smaller blocks.
Ceres, on the other hand, appears to have formed farther from the Sun and migrated into the inner solar system. Dawn measured Ceres’ surface composition and found a chemical (ammonia), which requires the colder temperatures of the outer solar system—beyond the orbit of Jupiter—to condense. Ceres may have formed there and then drifted closer to the Sun. Or materials from the outer solar system, having drifted inward, could have attached to Ceres as it formed.
Dawn also reinforced that location determines the amount of water incorporated in solar system bodies, and that water plays an important role in driving out heat. Bodies that formed with a lot of water, like Ceres, cooled fast. While those with little or no water, like Vesta, could not cool as fast. Vesta completely melted its own interior, forming a metallic core and rocky mantle and crust. However, Ceres’ interior is stratified in a rocky mantle made of water-rich rock (such as clays) and an outer shell rich in water in the form of ice and hydrates.
Dawn reinforces that dwarf planets, not just icy moons, could have hosted oceans during a large part of their history—and potentially still do.
Ocean worlds are a focus of space exploration because they may support conditions suitable for life. We now know there is a menagerie of moons that hold global oceans, including Saturn’s moons Enceladus and Titan, and Jupiter’s moon Europa.
Ceres is a crucial piece of the ocean worlds puzzle. With a crust that mixes ice, salts, rock-forming minerals and other materials, Ceres looks to be a remnant “ocean world,” wearing the chemistry of its old ocean and records of the interaction on its surface. Dawn’s observations suggest that there still may be some remaining briny liquid under its surface. As an evolved dwarf planet, Ceres can teach us about environmental conditions at other ocean worlds.
Dawn found organics at Ceres and left us wanting to know more.
Organic molecules are building blocks of life, and Dawn found abundant organics exposed in the region of Ernutet Crater. The Dawn team believes these came from Ceres’ interior, possibly evolving in the dwarf planet’s deep ocean. Dawn identified one type of organic molecule, called aliphatic, that is made up of chains of carbon and hydrogen. While these organics were found in a relatively localized region, Ceres' loose surface material also contains a lot of carbon on a global scale. Scientists still aren’t sure of the origin of Ceres’ organic molecules. On Earth, organics are commonly associated with life, but throughout our solar system, organics can be associated with non-biological processes.
The Dawn spacecraft is science fiction that has turned into science fact.
Science fiction brought us visions of spaceships capable of visiting multiple destinations and Star Wars’ “TIE” fighters, which stands for “twin ion engine.” Thanks to its own ion engines, Dawn is the only spacecraft ever to orbit two deep-space destinations.
When it went into orbit around Vesta in 2011, Dawn became the only spacecraft to orbit a body in the main asteroid belt between Mars and Jupiter. When Dawn went into orbit around Ceres in 2015, it also became the first spacecraft to visit a dwarf planet and the only spacecraft to orbit one.
While Dawn was not the first interplanetary spacecraft to use ion engines (an honor that goes to NASA's Deep Space 1), it pushed the capabilities of this technology farther. Dawn holds the record for the longest time in powered flight (the equivalent of six years) and greatest velocity change (25,700 mph or 41,400 kilometers per hour) achieved by a spacecraft with its own propulsion system.
Dawn found Vesta was a more varied world than scientists expected.
While the giant basin in Vesta’s southern hemisphere, now called Rheasilvia, was visible to Earth-based telescopes, Dawn confirmed just how big it is: more than 310 miles (500 kilometers) in diameter, and 12 miles (19 kilometers) deep. Dawn showed that the mountain seen by NASA’s Hubble Space Telescope at the center of the basin is twice the height of Mt. Everest. It’s the second tallest mountain in the solar system and nearly as high as Mars’ Olympus Mons.
Dawn’s close-up look revealed a second large impact basin, now called Veneneia, that was partially covered by the younger Rheasilvia basin. This one-two punch reshaped the surface of Vesta, and likely nearly destroyed it. These giant impacts created dozens of gorges (discovered in Dawn’s images) circling Vesta's equator, with an older set in the northern latitudes. Some of these canyons rival the Grand Canyon in size, measuring up to 290 miles (465 kilometers) in length and 2.5 miles (4 kilometers) deep.
Dawn data also show the massive impact that carved Rheasilvia happened only a billion years ago and caused huge amounts of material to rain back down on the surface. Thus, the surface of the southern hemisphere appears younger than the northern hemisphere, which retains a hefty record of craters.
Before Dawn, scientists thought of Vesta as a generally dry body, but Dawn found water-rich minerals on Vesta’s surface, associated with carbon-rich material that is also seen in meteorites from Vesta. These materials were likely delivered to Vesta by asteroids or comets from the more volatile-rich outer solar system.
Dawn revealed that Ceres is geologically active -- or was very recently.
Ceres features a glittering array of more than 300 bright features, called faculae (and initially called “bright spots”) that gleam atop an otherwise dark landscape. The brightest area in Occator Crater has the largest deposit of carbonate minerals ever seen outside Earth.
At Earth these minerals are associated with oceanic and lake environments. The findings suggest briny water rose to Ceres’ surface in the recent past and deposited salts.
Ceres holds an enormous volcano, dubbed Ahuna Mons, which the Dawn team believes formed as a cryovolcano. This lonely mountain," 3 miles (5 kilometers) high on its steepest side, suggests that liquid may still be present beneath the surface of Ceres. It is likely that liquids enriched in salts, which would lower the freezing point, are responsible for the relatively recent geologic activity. | 0.864745 | 4.031447 |
The fearless Voyager 1 and 2 shuttles were propelled in 1977, and in spite of having an around 12-year crucial, are as yet tearing through space and returning information to anxious researchers on Earth. They’ve gotten through hindrance that ensures our nearby planetary group and are currently hurdling through the interstellar medium alongside Pioneer 10 and 11.
A group of researchers—Coryn Bailer-Jones of the Max Planck Institute for Astronomy in Switzerland and Davide Farnocchia of NASA’s Jet Propulsion Laboratory—have done the estimations. Basically, the pair figured out how to graph to what extent it would take a rocket to get from our humble close planetary system to the following framework over, as per a paper transferred to the pre-print server arXiv.
In the mission for answers, Farnocchia and Bailer-Jones went to the European Space Agency’s Gaia space telescope for help. For over five years, Gaia has been gathering information on billions of stars, diagramming their circles and way through the universe.
Utilizing this information and information about the anticipated ways of both the explorer rockets just as Pioneer 10 and 11, which are tilting toward the external ranges of the nearby planetary group, the scientists had the option to make a course of events of when these specialties may arrive at far off star frameworks. For those anxious to visit different universes, prop for some awful news.
Should they proceed with their travel, the four rocket will come extremely close to roughly 60 stars in the following million years. Also, in that equivalent measure of time, they’ll get significantly nearer—attempt two parsecs, the likeness 6.5 light years—to around 10 stars.
Who will have the absolute best at coming to and investigating a removed star? Pioneer 10 will swing inside .231 parsecs the star framework HIP 117795 in the Cassiopeia heavenly body in around 90,000 years. What’s more, to what extent before one of these shuttles is commandeered by the circle of one of these stars? It’ll be about 1,000,000,000,000,000,000,000 years. | 0.922221 | 3.331895 |
Perihelion: 1970 March 20.04, q = 0.538 AU
One of the underlying foundations of “Ice and Stone 2020” is the fact that it marks the anniversary of my observations of my very first comet, Comet Tago-Sato-Kosaka 1969g – also, incidentally, the first comet ever observed from space. (I discuss this comet, including my observations of it, in a previous “Comet of the Week” presentation.) Less than two months later another, and significantly brighter, comet came along, and it was probably that object more than anything else that inspired my lifetime of comet observing. The fortuitous occurrence of two bright comets coming in quick succession right after I first began serious observations of the night sky led that budding young astronomer to believe that bright comets are a fairly common phenomenon – something that I have long since learned is not true. By the time I learned that, however, I was “hooked” . . .
This second comet was discovered on December 28, 1969, by a South African amateur astronomer, John Bennett. At that time it was about 9th magnitude and located in southern circumpolar skies and, traveling in an orbit almost exactly perpendicular to Earth’s, traveled northward and brightened over the subsequent weeks. By about the beginning of February 1970, it had reached naked-eye brightness, and it was close to 4th magnitude near the end of that month. By mid-March, it had brightened further to about 1st magnitude and was exhibiting a bright dust tail close to 10 degrees long. Shortly after perihelion passage, the comet became visible from the northern hemisphere, and it was as bright as magnitude 0, with the bright dust tail being in excess of 10 degrees in length, when I saw it for the first time on the morning of March 24.
Continuing its northward trek, Comet Bennett remained a bright and conspicuous object throughout most of April, fading only slowly, and with the dust tail remaining bright and prominent, with some reported measurements being close to 20 degrees. It also exhibited a fainter ion tail close to 10 degrees long, and meanwhile, telescopic observations revealed an active inner coma with various jets and “hoods” or “envelopes” – indicative of rotation.
The comet finally dropped below naked-eye visibility around the middle of May, by which time it was in northern circumpolar skies. It passed seven degrees from the North Celestial Pole in late September and remained visually detectable until November, with the final photographs being taken in February 1971.
Scientific studies of Comet Bennett include infrared observations obtained by University of Minnesota astronomer Raymond Maas (who tragically died of a heart attack less than 24 hours after obtaining these observations) which show silicate grains essentially identical to those in the atmospheres of red giant stars – an important link in the study of how planetary systems form. The comet was observed in the ultraviolet with the Orbiting Astronomical Observatory 2 (OAO-2) satellite and also with the Orbiting Geophysical IsObservatory 5 (OGO-5) satellite, and these showed the presence of a large cloud of hydrogen surrounding the coma, ten times the size of the sun in the case of the OGO-5 observations. OAO-2 had detected a similar, albeit smaller, cloud around Comet Tago-Sato-Kosaka, and we now know that these “Lyman-alpha” clouds accompany almost all comets that visit the inner solar system.
I have learned informally that Comet Bennett was the first comet to be observed by astronauts in space, as the crew of the ill-fated Apollo 13 mission viewed it while en route to the moon. I have also heard that there were plans for the astronauts to photograph the comet as well, but these were apparently pre-empted following the explosion of the Service Module on April 13.
The orbit of Comet Bennett is a distinct ellipse, with calculations indicating an orbital period of 1600 to 1700 years. Its high intrinsic brightness suggests that it should have been observable on its previous return, and in 1979 the Japanese astronomer Ichiro Hasegawa suggested it might be identical to a comet that was observed from China and Europe during August and September in A.D. 363 and which according to the Roman historian Ammianus Marcellinus was believed to presage the death of the Roman emperor Jovian the following year. Unfortunately, that comet was not well enough observed for a valid orbit to be computed, so we may have to wait until Comet Bennett returns again – sometime around the 37th Century – before we can clear this matter up one way or the other. | 0.829746 | 3.880359 |
While telescopes in space can scan the sky without interference from Earth's clouds, they still run into problems from hazes on other planets. To get around foggy skies, researchers have simulated haze formation in exoplanet atmospheres in hopes of better understanding future observations made with NASA's James Webb Space Telescope.
"One of the reasons why we're starting to do this work is to understand if having a haze layer on these planets would make them more or less habitable," lead author Sarah Hörst said in a statement. Hörst, a researcher at Johns Hopkins University in Maryland, and her team varied the levels of gases in their computer model to build nine simulated planets. Then, in the lab, the researchers created the combinations of particles predicted by that model in an effort to determine which mixtures of gas were most likely to form hazes. [NASA's James Webb Space Telescope Arrives in California for Final Testing]
Now you haze it — now you don't
By turning the most powerful telescopes toward exoplanets, astronomers can determine what gases make up those worlds' atmospheres. NASA's Hubble Space Telescope and ground-based instruments have already provided some hints about other worlds, and the upcoming James Webb Space Telescope (JWST) is expected to probe even deeper.
When solid particles are suspended in the gas of an atmosphere, they can form a haze that affects how light interacts with the gas, interfering with telescope observations. Specifically, the haze mutes the wavelengths of light that telescopes can pick up and which researchers use to identify the atmosphere.
Hörst and her team used computer models to assemble the atmospheres for super-Earths or mini-Neptunes, types of worlds not found in our solar system. Super-Earths are rocky worlds larger than Earth, while mini-Neptunes are miniature versions of the gas giants in this solar system. The models mixed levels of three dominant gases — carbon dioxide, hydrogen and gaseous water — and four other gases present to a lower degree in the models: helium, carbon monoxide, methane and nitrogen. Then, the researchers varied the mixes' temperatures to produce the quantities observed in the nine simulated worlds.
After combining the gases in a chamber and heating them, Hörst and her team sent the mixtures flowing through a plasma discharge to initiate chemical reactions. The flow of charged particles broke up the gas molecules and caused them to recombine with one another to make new things; this allowed the researchers to see which atmospheres created hazes.
"Sometimes, they'll make a solid particle, creating haze, and sometimes they won't," Hörst said. "The fundamental question for this paper was: Which of these gas mixtures — which of these atmospheres — will we expect to be hazy?"
All of them, it turns out. The researchers found that each of the nine "atmospheres" made haze in varying amounts. To the scientists' surprise, they found the most haze particles in two of the water-dominated atmospheres, rather than in the methane atmospheres, where they expected to see more haze.
"We had this idea for a long time that methane chemistry was the one true path to make a haze, and we know that's not true now," said Hörst. Methane is made up of both hydrogen and carbon, which were present in the experiment.
The researchers also found that differences in particle color could affect how much heat the haze traps.
Hazes may play a role in habitability, the researchers said. Just as today's ozone layer on Earth helps to shield life from harmful radiation, scientists suspect a primitive haze may have protected the planet in the past. Similar hazes could also help life evolving on exoplanets to survive and even thrive, the researchers said.
The team will next analyze the different hazes to see how the color and size of the particles affect how they interact with light, the investigators said. These details will help researchers when they are trying to measure the composition of exoplanets using Webb, which is set to launch in 2019. The results will help determine the best exoplanets to aim the instrument at after launch.
"Part of what we're trying to help people figure out is basically where you would want to look," Hörst said.
The research was published online in the journal Nature Astronomy. | 0.842921 | 3.975606 |
Did you know that there are 88 constellations in the night sky? Over the course of several thousand years, human beings have cataloged and named them all. But only 12 of them are particularly famous and continue to play an active role in our astrological systems. These are known as the zodiac signs, 12 constellations that correspond to the different months of the year.
Each of these occupies a sector of the sky which makes up 30° of the ecliptic, starting at the vernal equinox – one of the intersections of the ecliptic with the celestial equator. The order of these astrological signs is Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces. Here are all the zodiac signs and their dates. If your birthday falls within one of those date ranges, that’s your zodiac sign.
Granted, modern science has shown astrology to be an ancient fallacy, a way of connecting patterns in celestial movements to events and behaviors here on Earth. But for ancient people, such patterns were necessary given the fact that they lacked an understanding of human psychology, astronomy, and that Earth was not the center of the universe.
The concept of the zodiac originated in Babylon in the 2nd millennium BCE, and was later influenced by Hellenistic (Ancient Greek), Roman, and Egyptian culture. This resulted in a mix of traditions, where the 12 zodiac symbols were associated with the 12 Houses – different fields of experience associated with the various planets – and the four classical elements (Earth, Wind, Water and Fire).
In essence, astrology maintains that celestial phenomena are related to human activity, so the signs are held to represent certain characteristics of behavior and personality traits. What we know today as astrology comes from the 2nd century AD, as it was formally described by Ptolemy in his work, Tetrabiblos.
This book was responsible for the spread of astrology’s as we know it across Europe and the Middle East during the time of the Roman Empire. These traditions have remained relatively unchanged for over seventeen centuries, though some alterations have been made due to the subsequent discoveries of the other planets in our Solar System.
Naturally, the birth of the modern psychology, biology and astronomy has completely discredited the notion that our personalities are determined by birth signs, the position of the stars or the planets. Given what we know today of the actual elements, the movements of the planets, and the forces that govern the universe, astrology is now known for being little more than superstition.
What’s more, the dates of the ‘star signs’ were assigned over 2,000 years ago, when the zodiac was first devised. At that time, astronomers believed that the Earth’s position was fixed in the universe, and did not understand that the Earth is subject to precession – where Earth’s rotational and orbital parameters slowly change with time. As such, the zodiac signs no longer correspond to constellations of stars that appear in night sky.
And last, but certainly not least, there is the issue of the missing 13th sign, which corresponds to the constellation Ophiuchus. Over 2000 years ago, this constellation was deliberately left out, though the Sun clearly passes in front of it after passing in front of Scorpius (aka. Scorpio) and before reaching Sagittarius.
It is unclear why ancient astrologers would do this, but it is a safe bet that they wanted to divide the 360° path of the Sun into 12 equal parts. But the true boundaries that divide the constellations, as defined by the International Astronomical Union (IAU), are not exact. And Ophiuchus actually spends more time behind the Sun than its immediate neighbor (19 days compared to Scorpius’ 12).
To find out what zodiac sign you were really born under, check out this story from BBC’s iWonder. And in the meantime, here are the zodiac signs, listed in order along with what they mean, and some interesting facts associated with their respective constellations:
Aries: March 21 – April 19
The sign of Aries, which covers 0° to 30° of celestial longitude, is represented by The Ram, which is based on the Chrysomallus – the flying ram that provided the Golden Fleece in Greek mythology. Aries is associated with the First House, known traditionally as Vita (Latin for life) and in the modern context as the “House of Self”. Aries is associated with Fire, and the ruling celestial body of Aries is Mars.
The Aries constellation is also home to Teegarden’s Star, one of Sun’s closest neighbors, located approximately 12 light years away. It appears to be a red dwarf, a class of low temperature and low luminosity stars. And then there’s Alpha Areitis, which is easily spotted by the naked eye. Also known as “Hamal” – literally “head of the sheep” in Arabic – this star is located at the point where constellations angles downward to form an arc.
For those with telescopes, several galaxies can be spotted within the Aries constellation as well. These include the spiral galaxy NGC 772 and the large 13th magnitude NGC 697 spiral galaxy. NGC 972 is another, which is faint (at magnitude 12) and part of a galaxy group. And then there’s the dwarf irregular galaxy NGC 1156, which is considered a Magellanic-type galaxy with a larger than average core.
Aries is also home to several meteor showers, such as the May Arietids. This daylight meteor shower begins between May 4th and June 6th with maximum activity happening on May 16th. The Epsilon Arietids are also a daylight occurrence, and are active between April 25th to May 27th with peak activity on May 9th. And then there are the Daytime Arietids, which occur from May 22nd to July 2nd with a maximum rate of one a minute on June 8th.
To top it off, the Aries constellation contains several stars with extrasolar planets. For example, HIP 14810, a G5 type star, is orbited by three confirmed exoplanets, all of them giant planets (all Super-Earths). HD 12661, also a G-type main sequence star, has two orbiting planets (which appear to be Super-Jupiters). And HD 20367, a G0 type star, has one orbiting gas giant that roughly the same size as Jupiter.
Taurus: April 20 – May 20
The sign of Taurus, which covers 30° to 60° of celestial longitude, is represented by The Bull – which is based on the Cretan Bull that fathered the Minotaur and was killed by Theseus. Taurus is associated with the Second House, known by the Latin name of Lucrum (wealth) and by the modern name, “House of Value”, and the element Earth. The ruling celestial body of Taurus is Venus.
Taurus’ brightest star, Alpha Tauri, is also known by its traditional name, Al Dabaran (which was Latinized to become Aldebaran). The name, which is Arabic, literally means “the Follower” because of the way the Taurus constellation appears to follow the Pleiades star cluster across the sky. In Latin, it was traditionally known as Stella Dominatrix, but to Medieval English astronomers, it was known as Oculus Tauri – literally the “eye of Taurus.”
There is one major annual meteor shower associated with the constellation of Taurus: the annual Taurids, which peak on or about November 5th of each year and have a duration period of about 45 days. The maximum fall rate for this meteor shower is about 10 meteors per hour, with many bright fireballs often occurring when the parent comet – Encke – has passed near perihelion.
And speaking of Pleiades (aka. Messier 45, The Seven Sisters) this cluster of stars is located perpendicular to Aldebaran in the night sky, and is visible to the unaided eye. Although it is made up of over 1000 confirmed stars, this object is identifiable by its seven particularly bright blue stars (though as many as 14 up can be seen with the naked eye depending on local observing conditions).
Gemini: May 21 – June 20
The sign Gemini covers 60° to 90° of the celestial longitude, and is represented by The Twins. These are based on the Dioscuri of Greek mythology, two mortals that were granted shared godhood after death. Gemini is part of the Third House, traditionally named Fratres (Brothers) and currently known as the House of Communications. The associated element for Geminis is Air, and the ruling celestial body is Mercury.
Gemini’s alpha and beta stars – aka. Castor and Pollux (“The Twins”) – are the easiest to recognize and can be spotted with the naked eye. Pollux is the brighter of the two, an orange-hued giant star of magnitude 1.2 that is 34 light-years from Earth. Pollux has an extrasolar planet revolving around it, as do two other stars in Gemini, a super-Jupiter which was confirmed in 2006.
There are two annual meteor showers associated with the constellation of Gemini. The first is the March Geminids, which peaks on or around March 22nd. The average fall rate is generally about 40 per hour (but this varies) and the meteors appear to be very slow, entering our atmosphere unhurriedly and leaving lasting trails.
The second meteor shower are the Geminids themselves, which peak on or near the date of December 14th, with activity beginning up to two weeks prior and lasting for several days. The Geminids are one of the most beautiful and mysterious showers, with a rate of about 110 per hour during a moonless night.
The Gemini constellation is also associated with Messier 35, a galactic open star cluster that is easily spotted with the naked eye. The star cluster is quite young, having formed some 100 million years ago, and is quite bright due to it having blown away most of its leftover material (i.e. nebular dust and gas) that went into the star formation process. Other open clusters in Gemini include NGC 2158, which lies directly southwest of M35 in the night sky.
Cancer: June 21 – July 22
Cancer, which covers 90° to 120° of celestial longitude, is represented by The Crab – or Karkinos, a giant crab from Greek mythology that harassed Hercules during his fight with the Hydra. The sign is associated with the Fourth House – Genitor (Parent) in Latin, or the House of Home and Family in modern times. In terms of the elements, Cancers are characterized by the element of Water, and the ruling celestial body of Cancer is The Moon.
Cancer’s best known star is Beta Cancri, also known by its Arab name Altarf (“the End”). This 3.5 magnitude star is located 290 light-years from Earth and is a binary star system that consists of a spectral type K4III orange giant and a magnitude 14 red dwarf. This system is also home to a confirmed exoplanet, beta Cancri b, which is a Super-Jupiter with an orbital period of over 600 days.
In terms of deep-sky objects, Cancer is best known as being the home of Messier Object 44 (aka. Praesepe, or the Beehive Cluster), an open cluster located in the center of the constellation. Located 577 light-years from Earth, it is one of the nearest open clusters to our Solar System. M44 contains about 50 stars, the brightest of which are of the sixth magnitude.
The smaller, denser open cluster of Messier Object 67 can also be found in Cancer, which is 2500 light-years from Earth and contains approximately 200 stars. And so can the famous quasar, QSO J0842+1835, which was used to measure the speed of gravity in the VLBI experiment conducted by Edward Fomalont and Sergei Kopeikin in September 2002.
The active galaxy OJ 287 is also found in the Cancer constellation. Located 3.5 billion light years away from Earth, this galaxy has a central supermassive black hole that is one of the largest known (with 18 billion solar masses), and produces quasi-periodic optical outbursts. There is only one meteor shower associated with the constellation of Cancer, which is the Delta Cancrids. The peak date for this shower is on or about January 16t, and has been known to average only about 4 comets per hour (and the meteors are very swift).
Leo: July 23 – Aug. 22
Those born under the sign of Leo, which covers 120° to 150° of celestial longitude, carry the sign of The Lion – which is based on the Nemean Lion of Greek mythology, a lion that had an impenetrable hide. The sign of Leo is tied to the Fifth House, known in Latin as Nati (Children), or by its modern name, House of Pleasure. The sign of Leo is also associated with the element of Fire and the ruling celestial body of Leo is The Sun.
There are five annual meteor showers associated with the constellation Leo. The first is the Delta Leonid meteor stream, which begins between February 5th through March 19th every year. The activity peaks in late February, and the maximum amount of meteors averages around 5 per hour. The next is the Sigma Leonid meteor shower, which begins on April 17th. This is a very weak shower, with activity rates no higher than 1 to 2 per hour.
The next is the November Leonids, the largest and most dependable meteor shower associated with the Leo constellation. The peak date is November 17th, but activity occurs around 2 days on either side of the date. The radiant is near Regulus and this is the most spectacular of modern showers.
The shower is made more spectacular by the appearance of the Temple-Tuttle comet, which adds fresh material to the stream when it is at perihelion. The last is the Leo Minorids, which peak on or about December 14th, which is believed to produce around 10 faint meteors per hour.
Leo is also home to some of the largest structures in the observable universe. This includes many bright galaxies, which includes the Leo Triplet (aka. the M60 group). This group of objects is made up of three spiral galaxies – Messier 65, Messier 66, and NGC 3628.
The Triplet is at a distance of 37 million light-years from Earth and has a somewhat distorted shape due to gravitational interactions with the other members of the Triplet, which are pulling stars away from M66. Both M65 and M66 are visible in large binoculars or small telescopes, but seeing them in all of their elongated glory requires a telescope.
In addition, it is also home to the famous objects Messier 95, Messier 96, and Messier 105. These are spiral galaxies, in the case of M95 and M96 (with M95 being a barred spiral), while Messier 105 is an elliptical galaxy which is known to have a supermassive black hole at its center. Then there is the Leo Ring (aka. Cosmic Horseshoe) a cloud of hydrogen and helium gas, that orbits two galaxies found within this constellation.
Virgo: Aug. 23 – Sept. 22
The sign of Virgo, which covers 150° to 180° of celestial longitude, is represented by the The Maiden. Based on Astraea from Greek mythology, the maiden was the last immortal to abandon Earth at the end of the Silver Age, when the gods fled to Olympus. Virgo is part of the Sixth House – Valetudo (Health) in Latin, or House of Health in modern times. They are also associated with the element of Earth and the ruling celestial body of Virgo is Mercury.
The brightest star in the Virgo constellation is Spica, a binary and rotating ellipsoidal variable – which means the two stars are so close together that they are egg-shaped instead of spherical – located between 240 and 260 light years from Earth. The primary is a blue giant and a variable star of the Beta Cephei type.
Besides Spica, other bright stars in Virgo include Beta Virginis (Zavijava), Gamma Virginis (Porrima), Delta Virginis (Auva) and Epsilon Virginis (Vindemiatrix). Other fainter stars that were also given names are Zeta Virginis (Heze), Eta Virginis (Zaniah), Iota Virginis (Syrma) and Mu Virginis (Rijl al Awwa). Virgo’s stars are also home to a great many exoplanets, with 35 verified exoplanets orbiting 29 of its stars.
The star 70 Virginis was one of the first planetary systems to have a confirmed exoplanet discovered orbiting it, which is 7.5 times the mass of Jupiter. The star Chi Virginis has one of the most massive planets ever detected, at a mass of 11.1 times that of Jupiter. The sun-like star 61 Virginis has three planets: one is a super-Earth and two are Neptune-mass planets.
Libra: Sept. 23 – Oct. 22
The sign of Libra covers 180° to 210° of celestial longitude. It is represented by the symbol of The Scales, which is based on the Scales of Justice held by Themis, the Greek personification of divine law and custom and the inspiration for modern depictions of Lady Justice. Libra is part of the Seventh House – Uxor (Spouse) or House of Partnership, are associated with the element of Air, and the ruling celestial body is Venus.
Two notable stars in the Libra constellation are Alpha and Beta Librae – also known as Zubenelgenubi and Zubeneschamali, which translates to “The Southern Claw” and “The Northern Claw”. Alpha Libae is a double star consisting of an A3 primary star with a slight blue tinge and a fainter type F4 companion, both of which are located approximately 77 light years from our Sun.
Beta Librae is the brighter of the two, and the brightest star in the Virgo constellation. This is a blue star of spectral type B8 (but which appears somewhat greenish) which is located roughly 160 light years from Earth. Then there’s Gamma Librae (also called Zubenelakrab, which means “the Scorpion’s Claw”) which completes the Scorpion sign. It is an orange giant of magnitude 3.9, and is located 152 light-years from Earth.
Libra is home to the star Gliese 581, which has a planetary system consisting of at least 6 planets. Both Gliese 581 d and Gliese 581 g are considered to be some of the most promising candidates for life. Gliese 581 c is considered to be the first Earth-like exoplanet to be found within its parent star’s habitable zone. All of these exoplanets are of significance for establishing the likelihood of life outside of the Solar System.
Libra is also home to one bright globular cluster, NGC 5897. It is a fairly large and loose cluster, has an integrated magnitude of 9, and is located 40,000 light-years from Earth.
Scorpio: Oct. 23 – Nov. 21
The sign of Scorpio covers 210° to 240° of celestial longitude. Scorpio is represented by The Scorpion, which is based on Scorpius – a giant scorpion in Greek mythology sent by Gaia to kill Orion. Scorpio is part of the Eighth House – Mors (Death), known today as the House of Reincarnation – and is associated with the element of Water. Traditionally, the ruling celestial body of Scorpio was Mars, but has since become Pluto.
The Scorpius constellations includes many bright stars, the brightest being Alpha Scorpii (aka. Antares). The name literally means “rival of Mars” because of its distinct reddish hue. Other stars of note include Beta Scorpii (Acrab, or “the scorpion”), Delta Scorpii (Dschubba, or “the forehead”), Xi Scorpii (Girtab, also “the scorpion”), and Sigma and Tau Scorpii (Alniyat, “the arteries”).
Lambda Scorpii (Shaula) and Upsilon Scorpii (Lesath) – whose names both mean “sting”- mark the tip of the scorpion’s curved tail. Given their proximity to one another, Lambda Scorpii and Upsilon Scorpii are sometimes referred to as “the Cat’s Eyes”.
The Scorpius constellation, due to its position within the Milky Way, contains many deep-sky objects. These include the open clusters Messier 6 (the Butterfly Cluster) and Messier 7 (the Ptolemy Cluster), the open star cluster NGC 6231 (aka. Northern Jewel Box), and the globular clusters Messier 4 and Messier 80 (NGC 6093).
The constellation is also where the Alpha Scorpiids and Omega Scorpiids meteor showers take place. The Alphas begin on or about April 16th and end around May 9th, with a peak date of most activity on or about May 3rd. The second meteor shower, the Omega (or June) Scorpiids peaks on or about June 5th of each year. The radiant for this particular shower is closer to the Ophiuchus border and the activity rate on the peak date is high – with an average of about 20 meteors per hour and many reported fireballs.
Sagittarius: Nov. 22 – Dec. 21
The sign of Sagittarius covers 240° to 270° of celestial longitude and is represented by The Archer. This symbol is based on the centaur Chiron, who according to Greek mythology mentored Achilles in the art of archery. Sagittarius is part of the Ninth House – known as Iter (Journeys) or the House of Philosophy. Sagittarius’ associated element is Fire (positive polarity), and the ruling celestial body is Jupiter.
Stars of note in the Sagittarius constellation include Alpha Sagittarii, which is also known as Alrami or Rukbat (literally “the archer’s knee”). Then there is Epsilon Sagittarii (“Kaus Australis” or “southern part of the bow”), the brightest star in the constellation – at magnitude 1.85. Beta Sagittarii, located at a position associated with the forelegs of the centaur, has the traditional name Arkab, which is Arabic for “achilles tendon.”
The second-brightest star is Sigma Sagittarii (“Nunki”), which is a B2V star at magnitude 2.08, approximately 260 light years from our Sun. Nunki is the oldest star name currently in use, having been assigned by the ancient Babylonians, and thought to represent the sacred Babylonian city of Eridu. Then there’s Gamma Sagittarii, otherwise known as Alnasl (the “arrowhead”). This is actually two star systems that share the same name, and both stars are actually discernible to the naked eye.
The Milky Way is at its densest near Sagittarius, since this is the direction in which the galactic center lies. Consequently, Sagittarius contains many star clusters and nebulae. This includes Messier 8 (the Lagoon Nebula), an emission (red) nebula located 5,000 light years from Earth which measures 140 by 60 light years.
Though it appears grey to the unaided eye, it is fairly pink when viewed through a telescope and quite bright (magnitude 3.0). The central area of the Lagoon Nebula is also known as the Hourglass Nebula, so named for its distinctive shape. Sagittarius is also home to the M17 Omega Nebula (also known as the Horseshoe or Swan Nebula).
This nebula is fairly bright (magnitude 6.0) and is located about 4890 light-years from Earth. Then there’s the Trifid Nebula (M20 or NGC 6514), an emission nebula that has reflection regions around the outside, making its exterior bluish and its interior pink. NGC 6559, a star forming region, is also associated with Sagittarius, located about 5000 light-years from Earth and showing both emission and reflection regions (blue and red).
Capricorn: Dec. 22 – Jan. 19
The sign of Capricorn spans 270° to 300° of celestial longitude and is represented by the Mountain Sea-Goat. This sign is based on Enki, the Sumerian primordial god of wisdom and waters who has the head and upper body of a mountain goat, and the lower body and tail of a fish. The sign is part of the Tenth House – Regnum (Kingdom), or The House of Social Status. Capricorns are associated with the element Earth, and the ruling body body is Saturn.
The brightest star in Capricornus is Delta Capricorni, also called Deneb Algedi. Like other stars such as Denebola and Deneb, it is named for the Arabic word for “tail”, which in this case translates to “the tail of the goat’. Deneb Algedi is a eclipsing binary star with a magnitude of 2.9, and which is located 39 light-years from Earth.
Another bright star in the Capricorni constellation is Alpha Capricorni (Algedi or Geidi, Arabic for “the kid”), which is an optical double star (two stars that appear close together) – both o which are binaries. It’s primary (Alpha² Cap) is a yellow-hued giant of magnitude 3.6, located 109 light-years from Earth, while its secondary (Alpha¹ Cap) is a yellow-hued supergiant of magnitude 4.3, located 690 light-years from Earth.
Beta Capricorni is a double star known as Dabih, which comes from the Arabic phrase “the lucky stars of the slaughter” a reference to ritual sacrifices performed by ancient Arabs. Its primary is a yellow-hued giant star of magnitude 3.1, 340 light-years from Earth, while the secondary is a blue-white hued star of magnitude 6.1. Another visible star is Gamma Capricorni (aka. Nashira, “bringing good tidings”), which is a white-hued giant star of magnitude 3.7, 139 light-years from Earth.
Several galaxies and star clusters are contained within Capricornus. This includes Messier 30 (NGC 7099) a centrally-condensed globular cluster of magnitude 7.5. Located approximately 30,000 light-years from our Sun, it cannot be seen with the naked eye, but has chains of stars extending to the north that can be seen with a telescope.
And then there is the galaxy group known as HCG 87, a group of at least three galaxies located 400 million light-years from Earth. It contains a large elliptical galaxy, a face-on spiral galaxy, and an edge-on spiral galaxy. These three galaxies are interacting, as evidenced by the high amount of star formation in the face-on spiral, and the connecting stream of stars and dust between edge-on spiral and elliptical galaxy.
The constellation of Capricornus has one meteor shower associated with it. The Capricornid meteor stream peaks on or about July 30th and is active for about a week before and after, with an average fall rate is about 10 to 30 per hour.
Aquarius: Jan. 20 – Feb. 18
Aquarius, which spans 300° to 330° of celestial longitude, is represented by the Water Bearer. In ancient Greek mythology, Aquarius is Ganymede, the beautiful Phrygian youth who was snatched up by Zeus to become the cup-bearer of the Gods. Aquarius is part of the Eleventh House – Benefacta (Friendship), or House of Friendship, is associated with the element of Air. Traditionally, the ruling celestial body of Aquarius was Saturn, but has since changed to Uranus.
While Aquarius has no particularly bright stars, recent surveys have shown that there are twelve exoplanet systems within the constellation (as of 2013). Gliese 876, one of the nearest stars (15 light-years), was the first red dwarf start to be found to have a planetary system – which consists of four planets, one of which is a terrestrial Super-Earth. 91 Aquarii is an orange giant star orbited by one planet, 91 Aquarii b, a Super-Jupiter. And Gliese 849 is a red dwarf star orbited by the first known long-period Jupiter-like planet, Gliese 849 b.
Aquarius is also associated with multiple Messier objects. M2 (NGC 7089) is located in Aquarius, which is an incredibly rich globular cluster located approximately 37,000 light-years from Earth. So is the four-star asterism M73 (which refers to a group of stars that appear to be related by their proximity to each other). Then there’s the small globular cluster M72, a globular cluster that lies a degree and half to the west of M73.
Aquarius is also home to several planetary nebulae. NGC 7293, also known as the Helix Nebula, is located at a distance of about 650 light years away, making it the closest planetary nebula to Earth. Then there’s the Saturn Nebula (NGC 7009) so-named because of its apparent resemblance to the planet Saturn through a telescope, with faint protrusions on either side that resemble Saturn’s rings.
There are five meteor showers associated with the constellation of Aquarius. The Southern Iota Aquarids begin around July 1st and end around September 18th, with the peak date occurring on August 6th with an hourly rate of 7-8 meteors average. The Northern Iota Aquarids occur between August 11th to September 10th, their maximum peak occurring on or about August 25th with an average of 5-10 meteors per hour.
The Southern Delta Aquarids begin about July 14th and end around August 18th with a maximum hourly rate of 15-20 peaking on July 29th. The Northern Delta Aquarids usually begin around July 16th, and last through September 10th. The peak date occurs on or around August 13th with a maximum fall rate of about 10 meteors per hour.
Then there is the Eta Aquarid meteor shower, which begins about April 21th and ends around May 12th. It reaches its maximum on or about May 5th with a peak fall rate of up to 20 per hour for observers in the northern hemisphere and perhaps 50 per hour for observers in the southern hemisphere. Last, there is the March Aquarids, a daylight shower that may be associated with the Northern Iota Aquarid stream.
Pisces: Feb. 19 – March 20
The sign of Pisces covers 330° to 360° of celestial longitude and is represented by the The Fish. This symbol is derived from the ichthyocentaurs – a pair of centaurian sea-gods that had the upper body of a male human, the lower front of a horse, and the tail of a fish – who aided Aphrodite when she was born from the sea. Pisces is part of the Twelfth House of Carcer (Prison), or The House of Self-Undoing, and are associated with the element of Water. The ruling celestial body of Pisces is traditionally Jupiter, but has since come to be Neptune.
Beta Piscium, also known as Samakah (the “Fish’s Mouth”), is a B-class hydrogen fusing dwarf star in the Pisces constellation. Located 495 light years from Earth, this star produces 750 times more than light than our own Sun and is believed to be 60 million years old. The brightest star in the constellation, Eta Piscium, is a bright class B star that is located 294 years away from our Solar System.
This star is also known by its Babylonian name, Kullat Nunu (which translates to “cord of the fish”), the Arab name Al Pherg (“pouring point of water”), and the Chinese name Yòu Gèng – which means “Official in Charge of the Pasturing“, referring to an asterism consisting of Eta Piscium and its immediate neighbors – Rho Piscium, Pi Piscium, Omicron Piscium, and 104 Piscium.
And then there’s van Maanen’s Star (aka. Van Maanen 2) a white dwarf that is located about 14 light years from our Sun, making it the third closest star of its kind to our system (after Sirius B and Procyon B). Gamma Piscium is a yellow-orange giant star located about 130 light years away, and is visible with just binoculars.
The Pisces constellationis also home to a number of deep-sky objects. These include M74, a loosely-wound spiral galaxy that lies at a distance of 30 million light years from our Sun. It has many clusters of young stars and the associated nebulae, showing extensive regions of star formation. Also, there’s CL 0024+1654, a massive galaxy cluster that is primarily made up of yellow elliptical and spiral galaxies. CL 0024+1654 lies at a distance of 3.6 billion light-years from Earth and lenses the galaxy behind it (i.e. it creates arc-shaped images of the background galaxy).
Last, there the active galaxy and radio source known as 3C 31. Located at a distance of 237 million light-years from Earth, this galaxy has a supermassive black hole at its center. In addition to being the source of its radio waves, this black hole is also responsible for creating the massive jets that extend several million light-years in both directions from its center – making them some of the largest objects in the universe.
There is one annual meteor shower associated with Pisces which peaks on or about October 7 of each year. The Piscid meteor shower has a radiant near the Aries constellation and produces an average of 15 meteors per hour which have been clocked at speeds of up to 28 kilometers per second. As always, the meteoroid stream can begin a few days earlier and end a few days later than the expected peak and success on viewing depends on dark sky conditions.
Currently, the Vernal Equinox is currently located in Pisces. In astronomy, equinox is a moment in time at which the vernal point, celestial equator, and other such elements are taken to be used in the definition of a celestial coordinate system. Due to the precession of the equinoxes, the Vernal Equinox is slowly drifting towards Aquarius.
Astrology is a tradition that has been with us for thousands of years and continues to be observed by many people and cultures around the world. Today, countless people still consult their horoscope to see what the future has in store, and many more consider their birth sign to be of special significance.
And the fact that many people still consider it to be valid is an indication that superstitious and “magical” thinking is something we have yet to completely outgrow. But this goes to show how some cultural traditions are so enduring, and how people still like to ascribe supernatural powers to the universe.
We have a complete guide to all 88 constellations here at Universe Today. Research them at your leisure, and be sure to check out more than just the “zodiac sign” ones!
We also have a comprehensive list of all the Messier Objects in the night sky.
Astronomy Cast also has an episode on Zodiac Signs – Episode 319: The Zodiac | 0.894781 | 3.062179 |
Astronomers have discovered the darkest known exoplanet – a distant, Jupiter-sized gas giant known as TrES-2b. Their measurements show that TrES-2b reflects less than one percent of the sunlight falling on it, making it blacker than coal or any planet or moon in our solar system.
“TrES-2b is considerably less reflective than black acrylic paint, so it’s truly an alien world,” said astronomer David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA), lead author on the paper reporting the research. In our solar system, Jupiter is swathed in bright clouds of ammonia that reflect more than a third of the sunlight reaching it. In contrast, TrES-2b (which was discovered in 2006 by the Trans-Atlantic Exoplanet Survey, or TrES) lacks reflective clouds due to its high temperature.
TrES-2b orbits its star at a distance of only three million miles. The star’s intense light heats TrES-2b to a temperature of more than 1,800° Fahrenheit – much too hot for ammonia clouds. Instead, its exotic atmosphere contains light-absorbing chemicals like vaporized sodium and potassium, or gaseous titanium oxide. Yet none of these chemicals fully explain the extreme blackness of TrES-2b.
“It’s not clear what is responsible for making this planet so extraordinarily dark,” stated co-author David Spiegel of Princeton University. “However, it’s not completely pitch black. It’s so hot that it emits a faint red glow, much like a burning ember or the coils on an electric stove.”
Kipping and Spiegel determined the reflectivity of TrES-2b using data from NASA’s Kepler spacecraft. Kepler is designed to measure the brightnesses of distant stars with extreme precision.
The team monitored the brightness of the TrES-2 system as the planet orbited its star. They detected a subtle dimming and brightening due to the planet’s changing phase.
TrES-2b is believed to be tidally locked like our moon, so one side of the planet always faces the star. And like our moon, the planet shows changing phases as it orbits its star. This causes the total brightness of the star plus planet to vary slightly.
“By combining the impressive precision from Kepler with observations of over 50 orbits, we detected the smallest-ever change in brightness from an exoplanet: just 6 parts per million,” said Kipping. “In other words, Kepler was able to directly detect visible light coming from the planet itself.”
The extremely small fluctuations proved that TrES-2b is incredibly dark. A more reflective world would have shown larger brightness variations as its phase changed.
Kepler has located more than 1,200 planetary candidates in its field of view. Additional analysis will reveal whether any other unusually dark planets lurk in that data.
TrES-2b orbits the star GSC 03549-02811, which is located about 750 light-years away in the direction of the constellation Draco. (One light-year is about 6 trillion miles.) | 0.881679 | 3.972531 |
Young stars themselves are clearing out their nursery in NGC 7822. Within the nebula, bright edges and complex dust sculptures dominate this detailed skyscape taken in infrared light by NASA’s Wide Field Infrared Survey Explorer (WISE) satellite. NGC 7822 lies at the edge of a giant molecular cloud toward the northern constellation Cepheus, a glowing star forming region that lies about 3,000 light-years away. The atomic emission of light by the nebula’s gas is powered by energetic radiation from the hot stars, whose powerful winds and light also sculpt and erode the denser pillar shapes. Stars could still be forming inside the pillars by gravitational collapse, but as the pillars are eroded away, any forming stars will ultimately be cut off from their reservoir of star stuff. This field spans around 40 light-years at the estimated distance of NGC 7822. | 0.863279 | 3.249883 |
An eye-opening new study indicates that we aren't the first Earth, and probably won't be anywhere close to the last.
Researchers have found in a surprising new study that Earth is actually a pretty early planet, and many more like it will be formed.
This theoretical study, based on an assessment of data from NASA’s Hubble Space Telescope and the Kepler space observatory — the latter of which was specifically built for finding planets — states that only 8 percent of potentially habitable planets that will ever form existed when our Solar System first came into being some 4.6 billion years ago, according to a Phys.org report.
That means a whopping 92 percent of planets that may be potentially habitable or Earth-like still haven’t been born.
Peter Behroozi, who was the study author and works at the Space Telescope Science Institute (STScI) in Baltimore, said that the research team was trying to understand where Earth fits in with the rest of the universe, and they found that Earth is a very early planet.
The research team looked out the history of star formation as galaxies grew in size over billions of years, looking at the rate at which the universe is making stars. They found that the universe made stars at a pretty fast rate at about 10 billion years ago, but it didn’t involve a very large percentage of the hydrogen and helium gas in the universe, which are the building blocks of new stars.
So that means that while star birth isn’t happening at the frenetic pace that it was at the beginning of our universe, there is a huge amount of leftover gas, meaning that the universe will keep on cranking out new stars — and thus, new planets — for a very, very long time.
Earth-like planets are actually pretty common already, with probably many of them in our own galaxy — perhaps as many as 1 billion Earth-sized planets, most of them rocky. Multiply that by 100 billion galaxies and you have a lot of potential candidates for life.
Any future formation of Earth-like planets is likely to happen outside of our galaxy, however, as the Milky Way has used up most of its gas for star formation. As a result, most of these formations will probably happen in giant galaxy clusters and dwarf galaxies with lots of leftover gas.
Scientists put out a news release on the study, which can be found here. | 0.837005 | 3.513586 |
Authors: Detlev Koester, Boris Gaensicke, Jay Farihi
First Author’s Institution: Institut für Theoretische Physik und Astrophysik, Universität Kiel, 24098 Kiel, Germany
Over the past decade the study of planetary debris in orbit around white dwarfs has become an increasingly exciting area. Observations of this debris have allowed us to make unique discoveries about the chemical composition of extrasolar rocky planets, as well as revealing the endpoints of the evolution of planetary systems very similar to our own.
A key missing piece of information in these studies has been just how many, or more accurately what proportion of, white dwarfs have debris. Although many debris-polluted white dwarfs have been found, most of them were given away by other features such as orbiting dusty or gaseous debris discs. This leaves key questions unanswered.
For example, how many of the stars that formed the white dwarfs had planets? Does it depend on the kind of star? How do these evolved planetary systems change over time? In order to answer these questions, the authors have tried to gain an unbiased measurement of the frequency of planetary systems of white dwarfs.
The easiest way to spot the planetary debris in a white dwarf’s atmosphere is to look for light absorption by calcium, which creates a distinctive line in the blue end of a white dwarf’s spectrum. Unfortunately this calcium line tends to diminish at temperatures above around 15000K, severely limiting the range over which any results from the survey would be relevant. More importantly however, calcium only makes up a small fraction of the material in the planets of the Solar System, so might only show up in the spectra of more heavily polluted white dwarfs- not exactly an unbiased sample!
To get around this problem the authors decided to instead look for silicon, which makes up around a third of the Earth. If the composition of the planetary systems at white dwarfs are similar, the silicon should therefore be easy to spot even in mildly polluted white dwarfs. Unfortunately, all of the convenient silicon lines in the spectrum of a white dwarf are found in the ultraviolet. Earth’s atmosphere blocks out UV light, so this survey would need to use the Hubble Space Telescope.
The authors used a snapshot survey, providing a list of over a hundred white dwarfs that could be quickly observed in any order in the gaps between other, longer observations. Within a certain temperature range (17000—27000K), these white dwarfs were chosen at random. Over three years, eighty-five white dwarfs from their list were successfully observed, enough to get a good grip on the statistics of debris pollution.
The results of the survey are surmised in Figure 2. The key observation is the middle panel, showing the fraction of polluted white dwarfs. Out of the 85 white dwarfs, the authors found pollution from planetary debris in an astounding 48 (56%). This means that at least half of white dwarfs are orbited by the remains of planetary systems. Put another way, that means that at least half of the stars that turned into the white dwarfs once had orbiting planets. This result agrees nicely with the latest estimates from direct studies of exoplanets.
Out of those white dwarfs with debris pollution, analysis of their atmosphere shows that at half of them must be currently accreting rocky objects, whilst the other half will have been accreting recently. Far from being a few scattered objects, this paper has shown that active evolved planetary systems are abundan, and offer an intriguing opportunity to study the death-throes of planetary systems- including, eventually, the Solar System itself. | 0.880426 | 4.057186 |
A multidisciplinary team of BYU chemistry and engineering researchers has been tasked by NASA to develop a system to measure the size and electrical charge of Mars dust — a detail seemingly innocuous, yet critical to the success of human missions to the Red Planet.
“The next great challenge in human space flight is Mars,” said BYU chemistry professor Daniel Austin. “And of course, Mars is very dusty. The problem is we don’t know very much about the dust on Mars.”
We’re not just talking about a little dirt. Dust is a major problem on Mars because it is as abundant in the planet’s atmosphere as water is in Earth’s atmosphere. In fact, massive dust storms on Mars can last for months and they can span a large portion of the planet’s surface.
If that Mars dust gets into the oxygen source or spacesuits of astronauts, it could pose a serious health risk. The dust can also interfere with the functions of a spacecraft, like the rover Opportunity which NASA lost contact with in June 2018 due to a dust storm. The solar-powered robot couldn’t get enough sunlight to recharge its batteries and attempts to reestablish communication with Opportunity were abandoned in February of this year.
To address the dust problem, the BYU team is building a mass spectrometer with special printed circuit boards that help determine the charge, the velocity and the mass of a Mars dust simulant. As the particles pass across the electrodes of the circuit board, it detects their charge.
But since the charge is so small, the team also built a specialized microchip to amplify it for measurement, with a feedback capacitor that is about 1,000 times smaller than anything you can buy off the shelf. The microchip is small, robust, and consumes very little power — all desirable qualities for the folks at NASA.
The BYU team, which includes engineering professors Wood Chiang and Aaron Hawkins, as well as grad students Yi Xi, Jace Rozsa and Elaura Gustafson, created their own charged dust particles because such particles don’t exist on Earth as they do on Mars. The researchers start with a liquid suspension of dust grains, and then spray it in a high electric field, evaporate all the solvent and what’s left is a charged dust grain.
Knowing more about the charge of the Martian dust is vital because the charge is what makes it stick to things — like NASA equipment. The team hopes that the instrument they are developing will be used on unmanned missions to Mars in preparation for the first human trips projected to happen by 2033.
“NASA projects are very ambitious — each mission that goes to Mars is in the order of billions in cost,” Chiang said. “So it’s very important that we provide a solution that can handle all of the uncertainties associated with space so the mission has the maximum likelihood to succeed.”
Gustafson presented on the research last week at the 67th annual conference of the American Society of Mass Spectrometry, attended by approximately 8,000 people. Her poster, titled “Charge Detection Mass Spectrometry of Microparticles Using Printed Circuit Board Arrays,” detailed the Mars dust work happening in the labs of Austin, Chiang and Hawkins.
Added Austin: “It’s exciting to be working on a project that might eventually find its way on another world.” | 0.817599 | 3.551093 |
From: European Space Agency
Posted: Tuesday, March 5, 2019
ESA is planning Earth’s first dedicated space weather observatory to warn of potentially harmful turbulence in our parent star. Like a referee at a sports game, the Lagrange spacecraft will be able to observe both the Sun and Earth as well as the space in between – but will itself be in the space weather line of fire.
“This will be an operational rather a scientific mission, meaning it has to keep on working because people will be depending on it,” explains ESA space environment specialist Piers Jiggens.
“On Earth it wouldn’t be acceptable to have weather forecasting infrastructure that stops working when a hurricane is coming, because coverage would be lost at the point when an extreme weather event impacts our lives the most.
“In space it will be the same – so we at ESA’s Space Environment and Effects section have been working closely with the Agency’s Space Weather Office, overseeing the Lagrange mission, for several years. Our goal is an optimised design that endures the radiation storms associated with space weather events in an efficient but effective way.”
Sun making space weather
In the same way the heat of the Sun drives weather on Earth, solar activity is responsible for disturbances in our space environment, called ‘space weather’. As well as emitting a continuous stream of charged particles, known as the solar wind, the Sun sometimes produces eruptions called ‘coronal mass ejections’ (CMEs) – expelling billions of tons of material bound up with magnetic fields, often in volumes larger than Earth itself.
If these clouds of particles reach our home planet they can disrupt Earth’s magnetic field and upper atmosphere, disrupting satellites in orbit, and electrical and communications infrastructure, potentially causing billions of euros worth of damage.
Today’s workhorse solar observer, the ESA-NASA SOHO spacecraft is located 1.5 million km away at the Lagrange point L1, on a straight line between Earth and the Sun, so views incoming CMEs head-on.
By contrast, the Lagrange mission will be placed much farther from Earth, a hundred times further than SOHO at 150-million km distance, at the third point of an equilateral triangle formed with the Earth and the Sun.
Lagrange takes its title from the gravitationally stable locations in the Sun-Earth system, one of which it will orbit around – the fifth Earth-Sun Lagrange (L5) point. These have been collectively named after the Italian mathematician who first theorised the existence of these stable points in space.
Sitting at this equidistant point away from Earth and the Sun, Lagrange will be able to identify stormy segments of the Sun’s surface before they rotate around to face Earth, and then track CME clouds as they head our way.
“Just because the spacecraft is not aligned with Earth and the Sun does not mean it will not be affected by the space weather events it will be monitoring,” adds Piers. “This is because the solar magnetic field, which high energy particles follow, is curved because of the Sun’s rotation, a phenomenon known as the ‘Parker spiral’.
“What this means is that the fastest charged particles from a CME event will reach Lagrange in a matter of minutes after an eruption, potentially causing adverse effects to the spacecraft at just the point it is most needed to resolve the direction and speed of the material headed Earthward, working on a timescale of hours.
“Often you can see some of these effects on SOHO images of CMEs – what looks like snow is actually charged particles triggering the imager detectors. In addition, radiation can cause ‘bit flips’ of onboard memory.”
Shielding the spacecraft
As is already standard, the spacecraft itself will be built from carefully screened radiation hardened electronic components. Its onboard systems will be equipped with ‘fault detection and correction’ systems to identify and correct for bit flips or other anomalies. For the Lagrange mission, ESA and its industrial partners are investigating how to make these systems more robust still.
“For the L5 mission, the spacecraft has to be more intelligent than others, and will need to have a clever failure detection, isolation and recovery strategy,” notes Stefan Kraft, overseeing the mission.
“When other missions hide away and go into sleep mode, we will need to face the storm and stay awake to remain always on duty.”
On the imaging side, the particles impair the vision of the mission’s highly sensitive instrumentation. Automated onboard systems will apply artificial intelligence to identify and remove false pixels on a frame-by-frame basis.
Reduced image exposure time is another solution being looked into to decrease the number of radiation ‘hits’. In addition extra aluminium shielding could be added around the detectors, to prevent charged particles impacting them from the side.
As Juha-Pekka Luntama of ESA’s Space Weather Office explains: “The measurements from Lagrange need to be clear in real-time so they can be fed into space weather models and allow forecasters to predict possible impacts.”
he Lagrange mission is currently being developed through parallel industrial studies, to present to Europe’s space ministers at Space19+ at the end of this year. If approved, it will launch by 2025.
The US National Oceanic and Atmospheric Administration (NOAA) is planning a solar observatory at L1 with a launch targeted in 2024. This mission would provide data complementing observations from L5. The two missions together would form a combined observation system, offering stereosopic views of space weather events as they occur.
// end // | 0.857415 | 3.488804 |
The Colorado Student Space Weather Experiment (CSSWE) was 3-unit (10x10x30 cm) CubeSat configuration nanosatellite mission designed and developed by students at CU-Boulder under the direction of faculty and staff. In January 2010, the CSSWE project was funded by the National Science Foundation (NSF) to address fundamental questions pertaining to the relationship between solar flares and energetic particles. These questions include the acceleration and loss mechanisms of outer radiation belt electrons. The goal of the CSSWE was to measure differential fluxes of relativistic electrons in the energy range of 0.5-2.9 MeV and protons in 10-40 MeV. The project was a collaborative effort between LASP and the Department of Aerospace Engineering Sciences (AES) at CU-Boulder, and included the participation of students, faculty, and professional engineers.
The CSSWE science goal was the study of the phenomenology and range of processes active on the sun and in the radiation belts. Coronal Mass Ejections (CMEs) are very large structures (billions of tons of particles) containing plasma and magnetic fields that are occasionally expelled from the sun into the heliosphere. This violent solar activity is the cause of major geomagnetic disturbances, reflected by space weather, during which the trapped radiation belt electrons have their largest variations. There is a strong correlation between CMEs and solar flares, but the correlation does not appear to be a causal one. Rather, solar flares and CMEs appear to be separate phenomena, both resulting from relatively rapid changes in the magnetic structure of the solar atmosphere.
Solar flares are very violent processes in the solar atmosphere that are associated with large energy releases. The strongest support for the onset of the impulsive phase is due to magnetic reconnection of existing or recently emerged magnetic flux loops. Reconnection accelerates particles, producing proton and electron beams that travel along flaring coronal loops.
Some of the high-energy solar particles, referred to as Solar Energetic Particles (SEPs), escape from the sun to produce solar energetic particle events. The CSSWE mission measured these SEPs with the Relativistic Electron and Proton Telescope integrated little experiment (REPTile) instrument.
SEP measurements are important for space weather applications because of their direct effects in Earth’s ionosphere and on man-made systems in space. SEPs and CME particles enhance the ionosphere, primarily at high latitudes. These ionospheric changes lead to a myriad of space weather consequences, such as degradation or even disruption of communications, degradation in the accuracy of highly relied upon Global Positioning System (GPS) measurements and surges in the power lines on the ground that could lead to widespread blackouts.
Earth’s radiation belts are usually divided into the inner belt, centered near 1.5 Earth radii from the center of the Earth when measured in the equatorial plane, and the outer radiation belt that is most intense between 4 and 5 Earth radii. These belts form a torus around the Earth, and many important orbits go through them, including those for GPS satellites (MEO) and spacecraft in Geosynchronous Earth Orbit and in highly inclined Lower Earth Orbit.
The science goals of the CSSWE mission were to study:
- How flare location, magnitude, and frequency relate to the timing, duration, and energy spectrum of SEPs reaching Earth
- How the energy spectrum of radiation belt electrons evolve and how this evolution relates to the acceleration mechanism
- CSSWE Principal Investigator, Xinlin Li, LASP Scientist and CU-Boulder AES Professor
- CSSWE Co-Principal Investigators Scott Palo, CU-Boulder AES Professor, and Shri Kanekal
- CSSWE chief technical mentor, Rick Kohnert, LASP Engineer
- AES provided the CubeSat laboratory, machine shop, and teaching faculty for the project
- LASP provided instrument testing facilities and equipment, as well as scientific and technical mentorship for the project
- More than 60 students from different majors including astronomy and planetary sciences, aerospace, mechanical, electrical, and computer engineering have helped to design the mission and build all of its subsystems
For more information about the CSSWE, see:
The CSSWE flight mission has been completed, however data analysis and modeling continue on a dataset that consists of 3.5 million points covering about two years, which is more than six times the nominal mission lifetime. The data is available through NASA’s CDAWeb archive by checking the “CubeSats” box.
REPTile (Relativistic Electron and Proton Telescope integrated little experiment)
The REPTile instrument provided the following functions:
- It measured the outer belt electrons, both trapped and precipitating to study how the low rate and energy spectrum of the Earth’s outer radiation belt electrons evolves
- It monitored the SEP protons associated with solar flares to study how flare location, magnitude, and frequency relate to the timing, duration, and energy spectrum of SEP protons that reach Earth
- It measured electrons in 3 differential and 1 integral energy channel. Protons were measured in 4 differential channels
REPTile was a small (6.05 cm in length and 6 cm in diameter), low-mass (~1 kg), and low-power (<1 W) particle detector capable of measuring relativistic outer radiation belt electrons in the energy range of 0.5 to > 3 MeV and solar energetic protons from 10-40 MeV.
The instrument was a scaled down version of the REPT instrument, which was built at LASP for the NASA Van Allen Probes mission (formerly the Radiation Belt Storm Probes mission) in the LWS (Living with a Star) program.
For more information about the Van Allen Probes mission, see:
Launch date: August 2012
Launch location: Vandenberg Air Force Base, California
Launch vehicle: Atlas V
Mission target: Low Earth orbit
Mission duration: Two years (nominal mission duration was four months)
Other organizations involved:
- California Polytechnic State University
- U.S. Navy Postgraduate School
- U.S. National Reconnaissance Office | 0.81939 | 3.963184 |
Astronomers look back 13 billion years and spot baby galaxy, one of earliest ever seen
By SETH BORENSTEIN
AP Science Writer
WASHINGTON (AP) -- Astronomers took pictures of a far-off lumpy galaxy just forming 13 billion years ago, putting it among the earliest and most distant cosmic objects ever photographed.
Though the black-and-white images are fuzzy, they are the most detailed and best confirmed look back in both time and distance that humans have seen, said Johns Hopkins University astronomy professor Holland Ford. He was part of a team of scientists taking the pictures with NASA's space telescopes, Hubble and Spitzer.
The galaxy, called A1689-zD1, is from when the universe was about 700 million years old, not long after the formation of the first galaxies.
And it's different from galaxies like our Milky Way, Ford said.
"It is much smaller. It is lumpy. It has two centers instead of one and it is undergoing extreme star formation," he said. "It is basically the building blocks for what will be a galaxy like our own in the future."
To see that far away, astronomers needed a little luck and help from the cosmos. A cluster of much closer galaxies act as a natural zoom lens for Earth's telescopes. Strong gravitational forces bend light around that cluster of galaxies, magnifying the light from directly behind it.
In this case, the infant galaxy appeared at least 10 times brighter than it would have without the natural help, Ford said. Other places behind the cluster appear hundreds of times sharper. This natural lens has to be lined up perfectly in order to see what's behind it, he said.
When Earth gets stronger telescopes in the future, including a new space telescope to be launched in 2013, this young galaxy would be a good place to look, astronomers said.
On the Net: | 0.84534 | 3.14121 |
Last month, NASA's Spitzer Space Telescope ran out of the cryogen that has kept its instruments cool and allowed them to peer through the universe at some of the coldest objects in space for the last 5.5 years.
Far from ending the mission though, the milestone marked the beginning of an entirely new phase for the spacecraft, one that promises to be every bit as fruitful as Spitzer's initial run.
"It's valuable and it's unique and it's exciting," said project scientist Michael Werner of NASA's Jet Propulsion Laboratory in Pasadena, Calif.
The Warm Spitzer mission will consist of 10 large-scaled "Exploration Science" projects, as well as dozens of smaller efforts. These projects will look at everything from Near Earth Objects (asteroids and comets that orbit the sun near Earth's path) to extrasolar planets to massive galaxies in the early universe.
"There's quite a variety of them," Werner said.
Mission managers are still checking out Spitzer's infrared array camera to make sure it is working properly at the telescope's new warmer temperature, so it will be about a month until data for the new projects begins coming in, but effectively "the mission is underway," Werner said.
Cold vs. warm
During its cryogenic mission, Spitzer's infrared eye detected a whole range of wavelengths, from the very short to the very long (about 3 microns to 160 microns). With the loss of its liquid helium coolant, those longer wavelengths get lopped off, but Warm Spitzer will still have excellent vision at shorter wavelengths.
(And as Werner points out, "cold is a relative term." Warm Spitzer is still only at -400 degrees Fahrenheit (-240 Celsius) -- "that's still really cold," he said.)
Being limited to shorter wavelengths doesn't entirely limit the science Spitzer can do, because "it turns out it depends on what you want to look at," Werner told SPACE.com. There's still plenty of science that is ideally done at these wavelengths.
And the less frenzied pace of the Warm Mission will actually allow scientists to do projects that wouldn't have fit into the original mission's schedule.
One such project will examine the variability of so-called young stellar objects. "These are objects where they're in the process of forming planetary systems, they're surrounded by a disk of material, the disk is interacting with the star in various ways," Werner explained. "It's a kind of a messy situation."
Young stellar objects are known to vary on timescales of days to weeks, so Warm Spitzer will observe some continuously for several weeks. "In the cryogenic mission, that would not have been possible because we were switching instruments on timescales of one to two weeks," Werner said.
Warm Spitzer will also devote 2,000 hours to a single deep survey project looking into the early universe. "That's about twice as big as any program that we had in the cryogenic mission just because of the pressure of the various competing scientific interests," Werner said.
The new phase will also include projects that "we really didn't know we could do during the cryogenic mission," particularly observations of exoplanets, Werner said.
One such project whose potential wasn't realized until late in the game of the original mission is the observation of Near Earth Objects (NEOs), the asteroids and comet remnants that are in our region of the solar system and, in some cases, could one day pose a threat to Earth.
So one of the 10 large Warm Spitzer projects will observe a group of about 700 NEOs to learn more about their sizes and makeup.
"At the very short wavelengths where Warm Spitzer works is a unique niche to be able to measure the solar flux of something in the solar system," said principal investigator of the project David Trilling of Northern Arizona University. "It only works because the NEOs are very warm compared to other things in the solar system."
While objects in the outer regions of the solar system have colder temperatures, "the NEOs have temperatures like the Earth, basically, because they're in orbits similar to the Earth's orbit."
About 5,000 NEOs have been identified, along with their orbits in most cases. This information is all that is needed to determine if any individual object is at risk of colliding with the Earth. But, "we know almost nothing about any individual object," Trilling told SPACE.com.
The Warm Spitzer survey will observe the selected NEOs to determine the proportions of large and small rocks and other characteristics about the unusual objects.
"That's the main thrust of our study -- we want to study the global properties of this population that we know almost nothing about despite the fact that they are the closest thing to Earth in the solar system," Trilling said.
Knowing the size distribution of the NEOs sheds light on just how they got to be where they are, far from the Oort cloud or the main asteroid belt between Mars and Jupiter.
"Where did these objects come from? What has happened to them since they came to the NEO region? Have they collided with each other, have they collided with planets? Have they split into parts?" Trilling said.
Most are likely asteroids that were displaced by some dynamical interaction and migrated closer to the Earth. Others are likely dead comets that got stuck in the inner solar system after their orbits brought them close to the sun and the material that makes up their tails was burned off.
While they look like rocks from the outside, dead comets could contain water and organic materials. Some scientists think that Earth's own life and water were seeded by comet impacts, so the dead comets in the NEO population "may have had a very significant impact, no pun intended, on the early Earth," Trilling said.
The Spitzer survey will examine the reflectivity of NEOs to distinguish asteroids from dead comets (the different compositions of objects affect how they reflect light).
The survey will also look at binary NEOs and will estimate the combined densities of these very common pairings, which will also shed light on the composition and origin of the objects.
"It's a pretty neat opportunity," Trilling said of the project.
'All over the map'
Among the other large projects planned for the Warm Spitzer mission are four that will look at exoplanets.
Two will look at already discovered planets, while the other two will be looking for their own discoveries, including searching for so-called "super Earths."
Of the two looking at known exoplanets, one will be confirming discoveries by the Kepler mission, now in orbit and operational, and learning more about them by determining whether they are gaseous or rocky, the structure of their atmospheres and other characteristics.
The other will conduct an orbital study of exoplanets, "where you look at the exoplanet over its entire orbit around the star," Werner said. "That allows you to look at the distribution of temperature on the surface of the exoplanet."
Another project will complete an earlier Spitzer survey of the galactic plane, learning about the distribution of stars in the Milky Way, their masses, ages, and how far out do spiral arms extend, telling us "more and more about our home base, so to speak," Werner said.
Another survey will do the same characterization of stars in other galaxies, while others peer at galaxies in the early universe.
"We're looking to a time when the universe was essentially 10 percent of its current size and age -- pretty far back," Werner said.
"One of the most interesting ones is to measure the Hubble constant, which is the rate at which the universe is expanding locally," Werner said.
Spitzer will try to help constrain the value of the Hubble constant by observing Cepheid variable stars, which feature a "relationship between the period of its variation and its brightness," Werner explained. If their brightness is known, their distance can be calculated, telling us just how fast the universe is expanding around us.
Of the many small projects that will also be conducted, many will also be looking at exoplanets, while others will observe brown dwarfs, supernovas, and minor planets, among other targets.
"They're sort of all over the map," Werner said.
All of these varied projects will be conducted over the next two years, the current planned time period for the Warm Spitzer mission.
Mission managers are already considering applying for a roughly 2.5-year extension, which would take the warm mission to 2014.
But that will be the end for Spitzer.
"Spitzer is moving away from the Earth, and around the end of 2013, it gets so far away that it would be difficult if we had a saving event to recover the data to properly diagnose the problems," Werner said. "So we're kind of considering that as a reasonable sunset clause for the warm mission."
Spitzer won't crash into the sun or move out of its orbit, "it will just continue to orbit the sun for eternity," Werner said. | 0.921437 | 3.890572 |
Niels Bohr, Werner Heisenberg, Erwin Schrödinger
By Matthew Kelly 13B
Niels Bohr (7 October 1885 – 18 November 1962) was a Danish physicist who helped discover quantum physics and the structure of the atom.
The Rutherford–Bohr model or just Bohr model for short (1913) followed on from the plum-pudding model (1904) and the Rutherford model (1911).
The Bohr model, introduced by Niels Bohr in 1913, shows the atom as small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the solar system, but with attraction provided by electrostatic forces rather than gravity.
Werner Karl Heisenberg (December 5, 1901 – February 1, 1976) was a German physicist, Nobel Prize winner and one of the people who started a new area of physics called quantum mechanics. Most people think that he is one of the most important scientists of the 20th century. He is also well known for discovering the Heisenberg uncertainty principle, which explains that there is a limit on how well some things can be measured.
Heisenberg’s uncertainty principle is one of the most important results of twentieth century physics. It relates to measurements of sub-atomic particles. Certain pairs of measurements such as:
1. Where a particle is
2. Where it is going (its position and momentum) cannot be exactly found.
In other words you can know the position or the speed of the sub-atomic particle but you can’t know both.
Erwin Rudolf Schrödinger
Erwin Rudolf Josef Alexander Schrödinger was an Austrian Physicist. He was one of the founders of quantum mechanics and won the Nobel Prize in Physics in 1933.
The Schrödinger equation is a mathematical formula that forms the basis of quantum mechanics, the most accurate theory of how subatomic particles behave. It is a mathematical equation that was thought of by Erwin Schrödinger in 1925. It defines something called the wave function of a particle or system (group of particles) which has a certain value at every point in space for every given time. These values have no physical meaning, yet the wave function contains all information that can be known about a particle or system. We can therefore think of the various parts of the atom, especially electrons, as waves.
The electron waves for the first three Bohr orbits are visualized above, depicting the waves as meeting a kind of resonance condition so that the continuing waves interfere constructively with each under these conditions. The numbers apply to the hydrogen orbits.
The Bohr model of the atom started the progress toward a modern theory of the atom with its postulate that angular momentum is quantized, giving only specific allowed energies. Then the development of the quantum theory and the Schrodinger equation refined the picture of the energy levels of atomic electrons.
The model of the atom that therefore existed at the onset of the Second World War is of a nucleus surrounded by a cloud of electrons. It is a visual model that maps the possible locations of electrons in an atom. The model is used to describe the probable locations of electrons around the atomic nucleus. The electron cloud is also defined as the region where an electron forms a three-dimensional standing wave, the one that does not move relative to the atomic nucleus. The model does not depict electrons as particles moving around the nucleus in a fixed orbit. Based on quantum mechanics, it gives the probable location of electrons represented by an ‘electron cloud’.
The electron cloud model uses the concept of ‘orbitals’, referring to regions in the extra-nuclear space of an atom where electrons are likely to be found. An orbital is a mathematical function that describes the wave-like behaviour of electrons in an atom. With the help of this function, the probability of finding an electron in a given region is calculated. The term ‘orbital’ can be used to refer to the physical region where electrons can be found. They are designated with the names s, p, d, and f. The s orbitals are spherical, p orbitals re dumbbell-shaped, d orbitals have two angular nodes, and f orbitals have three. An orbital can contain no more than two electrons.
Read more at Buzzle: | 0.825618 | 3.917551 |
The potentially dazzling Comet ISON has brightened enough on its highly anticipated approach toward the sun that it's now visible through a decent pair of binoculars.
Skywatchers around the world have recently used binoculars to spot Comet ISON, which is streaking toward a close encounter with the sun on Nov. 28 that will bring the icy wanderer within just 730,000 miles (1.2 million kilometers) of the solar surface.
"I have made my first confirmed binocular sighting of C/2012 S1 ISON as well," Pete Lawrence, of the town of Selsey in the United Kingdown, told the website Spaceweather.com on Saturday (Nov. 9). "ISON's head appears small and stellar through a pair of 15x70s optics." [See amazing photos of Comet ISON by stargazers]
Comet ISON is cruising through the constellation Virgo at the moment and is visible in binoculars low in the predawn eastern sky, Spaceweather.com reports. The comet is currently as bright as an 8th magnitude star — too dim to be seen with the naked eye but easy to spot with binoculars or a small telescope.
ISON was discovered by two Russian amateur astronomers in September 2012, giving scientists more than a year to prepare for its close solar flyby. Researchers have been tracking the comet with a variety of instruments on the ground and in space, hoping to learn about ISON's composition by watching which gases boil off its surface at various distances from the sun.
Skywatchers have had a keen interest in ISON as well, for the comet could put on a great show in December if it survives its close pass by the sun later this month.
While some researchers have voiced optimism that ISON will hold together, there are certainly no guarantees; it's tough to predict the behavior of any comet, particular a "dynamically new" one such as ISON that's making its first trip to the inner solar system from the distant and frigid Oort Cloud.
Editor's note: If you snap an amazing photo of Comet ISON or any other celestial sight that you'd like to share for a possible story or image gallery, please contact managing editor Tariq Malik at [email protected]. | 0.866562 | 3.178466 |
Students should normally have completed AY101 or a more advanced astronomy course; people now enrolled in AY101 or AY204 can be admitted with consent of instructor (i.e. at their own risk).
This course is designed to give motivated students direct experience in astronomical observations and their analysis, including visual and electronic techniques. We will use portable telescopes on campus, the 16-inch telescope of the campus observatory, telescopes located in the darker skies at Moundville, and observatory telescopes in Arizona and Chile by internet control.The course carries 2 credit hours (one lecture, one lab).
Both indoor exercises and observing projects are included. The lab scheduled for a particular period depends on the weather, phase of the moon, etc. There will be 12 sessions for the lab. Each student will do an independent observing project during the semester; get an early start to avoid being clouded out! The lab reports should be self-contained and complete descriptions of each exercise when forms are not provided in the exercise.
After successful completion of the course, students will be able to:
- Understand coordinate systems used in finding and recording celestial objects
- Set up and use common types of portable telescopes
- Locate celestial objects of interest using telescopes with and without automated pointing systems
- Perform and interpret imaging observations with electronic detectors
- Analyze data sets using simple mathematical models, including the role of measurement error
- Carry out and report a complete research project, from concept and data collection to analysis and conclusions
You should bring a calculator and elementary astronomy text (surely you didn’t sell it back to the bookstore!). For outdoor labs, remember that it can get pretty cold late in the fall, and dress accordingly. For some lab exercises, a millimeter ruler will help. Some dark-sky sessions will take place at Moundville Archaeological Park, for which a flashlight will be particularly helpful. In fact, a flashlight is a good idea any time we’re actually observing, much better than trying to read charts with a cigarette lighter.
Specific subjects for each session depend on the weather and phase of the Moon, so if weather dictates, we can select the most appropriate activity shortly before starting. This preliminary schedule of activities is subject to change depending on the weather.
Possible Learning Projects
- Rotation of giant planets
- Masses of planets from orbits of their satellites
- Hertzsprung-Russell diagram for a star cluster
- Stellar spectra and classification
- Meteor photography
- Light curves and physical properties of variable stars
- The distribution of galaxies in nearby clusters
- Variability of quasars and active galactic nuclei
- Structures of gaseous nebulae
- Comet tracking (if any are bright enough this term)
- Detection of giant extrasolar planets as they pass in front of their stars
The course grade will be based on results and written reports of the lab sessions (75%) and individual observing projects (25%). There is no final exam. Attendance is important since many of the activities are hands-on and cannot always be rescheduled. Students who must miss an activity should contact me to negotiate appropriate equivalent activities, where possible.
Other Important Information
Academic misconduct: All students in attendance at the University of Alabama are expected to be honorable and to observe standards of conduct appropriate to a community of scholars. The University expects from its students a higher standard of conduct than the minimum required to avoid discipline. Academic misconduct includes all acts of dishonesty in any academically related matter and any knowing or intentional help, or conspiracy to help, another student. The Academic Misconduct Disciplinary Policy will be followed in the event of academic misconduct.
Disability Services: Students with disabilities are encouraged to register with the Office of Disability Services (348-4285). Thereafter, you are invited to schedule appointments to see me during office hours to discuss accommodations or other special needs. | 0.887444 | 3.036224 |
Global Cooling FTW?
Because it turns out that even the Sun has gone into a lockdown 'recession'. Or, more accurately, a deep period of 'solar minimum'.
Which means that the activity on the Sun's surface has fallen dramatically, and its magnetic field has become weaker, letting into the environment more of the sort of cosmic rays that cause dramatic lightning storms and interfere with astronauts and space hardware.
They can also can lead to the explosion of 'sprites' — clusters of orange and red lights that shoot out of the top of thunderstorms like 60-mile-high palm trees in the sky.
Oh yes, and on top of all that, theoretically it could cause the temperature on Earth to drop to potentially catastrophic new lows.
While the Met Office and members of the Royal Astronomical Society are urging us not to panic and reminding us that this is just nature, nothing to worry about and the sort of thing that happens every 11 years or so as the Sun passes through its activity cycle, some doom-and-gloomers are much less optimistic.
Perhape they're haunted by the extreme 'solar minimum' thought to have contributed to the so-called Little Ice Age in Europe in the 17th and 18th centuries, when the temperatures fell so low the River Thames froze over, crops failed, lightning storms lit up the skies, and — in 1816 — the weather was so crazy that it snowed in July.
As we all know, the Sun — which is 4.5 billion years old and more than a million times bigger than the Earth — is not only a source of cheer when it finally pops out from behind the clouds, it also keeps us all alive.
Which means that the teeniest change in its activity levels can have extraordinary consequences — triggering lightning storms, the appearance or disappearance of the Northern Lights and those amazing sprites.
But the Sun's activity is changing constantly as it passes through its regular cycle, from solar maximum (hottest and most active) to solar minimum (quieter and cooler).
Since the 17th century, scientists have been measuring the depth of a solar minimum by counting the 'sunspots' — areas of magnetic activity on the solar surface which show up as relatively dark spots — and solar flares, large explosions that hurl charged particles into space.
The general rule is the fewer the sunspots, the more severe the minimum and the higher the chances of lightning storms, sprites and disruption on Earth.
So far this year, the Sun has been 'blank' — with no sunspots — 76 per cent of the time. A figure surpassed just once since the Fifties, last year, when it was 77 per cent blank.
So could we be heading for a grand solar minimum, a sustained period — decades, even centuries — of particularly weak solar cycles? Are we now — on top of everything else — facing another mini ice age?
As far as I can tell, this is in line with mathematical modeling predictions made by one Prof. Valentina Zharkova years ago. She argued that the Sun was entering a period of prolonged diminished activity, similar to the one that caused the 70-year Maunder Minimum in the 17th Century, and that this period would begin in 2020 and carry on through 2030.
She stated that the 11-year solar cycles that affect the strength of the Sun's magnetic field, and therefore directly affect the rate at which cosmic radiation bombards Earth and generates cloud formations, which in turn affect the Earth's overall mean temperature as well as continental, regional, and local climactic fluctuations, would cancel each other out.
And she stated, back in 2017, that she hoped that man-made global warming would cancel out the potential effects of solar cooling and prevent that Ice Age.
That appears to be a possibly forlorn hope right now, because human activity contributes a grand total of about three percent to the entire annual generation of carbon dioxide into the atmosphere.
Seriously. THREE PERCENT. That's it. That's all that 7.4 billion or so humans contribute, in total, to atmospheric CO2.
Indeed, CO2 isn't even the most powerful greenhouse gas around. Its overall effect on climate is evidently quite weak. There are far stronger greenhouse gases out there, such as methane, and it is on those gases that the latest research is focused.
The working theory that a significant number of climate scientists have is that global warming will result in the melting of frozen methane pockets and lakes, which will result in huge releases of methane all over the world, which will then cause the Earth to tip over a "climate cliff" right into oblivion, into runaway global warming that will destroy human civilisation.
Turns out, that prediction about methane is very likely to be wrong too:
Researchers at the University of Rochester in New York studied methane emissions from a period in Earth's history which bears many similarities to our current climate, examining ice cores taken from the last period of deglaciation some 8,000 to 15,000 years ago.
By closely examining air samples extracted from these frozen ice cores, the researchers found that even if the methane in these vast stores is released, it won't actually reach our atmosphere.
“Our data shows we don't need to be as concerned about large methane releases from large carbon reservoirs in response to future warming,” said Vasily Petrenko, a professor of Earth and environmental sciences at Rochester. “We should be more concerned about methane released from human activities."
When carbon-based life (plants and animals) decays, the remains freeze and the carbon contained within becomes trapped in the permafrost seen across regions including vast swathes of Siberia, Alaska and northern Canada.
Later, when the water in this permafrost melts, the soil becomes waterlogged and creates the ideal breeding ground for microbes that consume the newly-thawed carbon and produce methane.
Meanwhile, in the oceans, methane hydrates – formed under immense pressures at low temperatures – are found in sediments on the ocean floor along the subaquatic borders of the continents. If ocean temperatures rise, the current theory goes, these hydrates will destabilize and release the methane gas into the atmosphere, wreaking havoc around the globe.
The team took ice core samples from the Earth's past to see just how much methane from these ancient deposits is actually released during periods of warming, and found that the actual amount of emissions from ancient carbon reservoirs was quite small.
“The likelihood of these old carbon reservoirs destabilizing and creating a large positive warming feedback in the present day is also low,” said Michael Dionysus, a graduate student involved in the research.
The usual alarmism about "human activity" with respect to methane and carbon dioxide can be found all over these articles and the scientific research. It seems that this is the standard disclaimer that has to be attached to any and all climate research these days, in order to avoid getting one's funding cancelled.
So, what is actually likely to happen? Global warming? Global cooling? Global WTF?
Well, if you go by scientific consensus - note, this is NOT SCIENCE - then you will quickly realise that the general consensus has pretty much always been in favour of global warming, even during the period from 1965 to 1979, when the mainstream media was hyping the possibility of global cooling:
The global cooling hype got so, uh, heated - sorry for the pun - that a documentary narrated by Mr. Spock, Leonard Nimoy, was produced in which the strong and sober voice of the great Vulcan science officer explained that scientists were worried that the world would experience a new Ice Age.
So... again, which is it?
The actual science - not the consensus, the SCIENCE - is unable to provide much of a picture on this subject.
Virtually every modeled prediction of global warming has proven to be spectacularly wrong. The most accurate models more or less correctly predicted total concentrations of CO2 in the atmosphere, but failed completely to predict the actual amounts of warming. Every single one of the models going back to 1979 predicted more warming than has actually manifested.
Anyone with an ounce of sense could tell you that models of complex interdisciplinary phenomena are EXTREMELY difficult to get right. Whether we are looking at climatological, financial, or virological models, virtually every single one of the loss-severity models that are considered "gold standard" in each of those realms are highly unstable, unreliable, and inaccurate.
And that is because virtually every one of them depends on built-in assumptions that are untested and unproven, and often wildly ridiculous.
It is bad enough that we trust scientists to inform us when they themselves are no better than three blind men describing an elephant through touch. It is far, FAR worse when we give power to politicians to act on the basis of scientific advice that is reliably wrong.
A far better and more sensible heuristic is to gauge the likely outcomes of the future based on whether or not modeled predictions came to pass.
This is a much more reliable approach because it takes into account what actually happened. And what actually happened, in the case of the world's climate, is that no statistically significant warming was observed using satellite data after 1998 in the atmosphere, and that surface temperature records have proven to be highly unreliable at best.
Furthermore, every single prediction made by the climate alarmists in the 1990s and early 2000s has completely failed to come to pass.
Which means that we can argue with likely in excess of 98% certainty that they are totally wrong about global warming, and that the world's climate is likely to cool significantly over the next few hundred to thousand years.
The reason for this is a combination of solar magnetodynamics and the Earth's orbit around the Sun.
We know that the Earth "wobbles" very slightly on its own axis of rotation. Given the size of the Earth, this axial wobble absolutely has an influence on the Earth's climate, because it means that slightly more of one hemisphere is exposed to sunlight at any given point in time relative to the previous year. This has profound effects on ice formation across the Earth's surface.
This, combined with the fact that the Earth has an elliptical, not circular, orbit around the Sun, and the fact that this ellipsoidal orbit is itself subject to very small but profoundly influential fluctuations, has a strong knock-on effect on whether the Earth is in an Ice Age or not.
These phenomena are captured in the research of a Serbian geophysicist and astronomer named Milutin Milankovich, whose Milankovich Cycles describe how the Earths' surface temperature is affected by these axial and orbital wobbles.
Unlike garbage-in-garbage-out modeling, of which we are afflicted with far too much, Milankovich Cycles can be statistically modeled and replicated and simulated with very high degrees of accuracy, because ice core data match the mathematical equations extremely closely.
As the Infogalactic article points out, there are problems with the explanatory power of these cycles, which are well known.
But when you combine the information about the Sun's extended period of reduced activity with the massive failures of climate modeling to correctly predict serious global warming and the current state of the Milankovich Cycles, we are actually in for an extended period of overall cooling, interspersed by periods of relative warmth.
The last Ice Age ended about 10,000 years ago, more or less. During that time, vast mile-thick sheets of ice covered much of North America. What we would know of today as Manhattan was buried under a sheet of ice roughly half a mile thick. That is the degree to which these changes in solar output and terrestrial axial and orbital movements affect global climate.
The presence of humans is, at best, a footnote to these changes, and will continue to be so for millennia. To think otherwise, in the face of continued failed predictions, absurdly mismanaged modeling, statistical evidence, and simple common bloody sense, is arrogant in the extreme. We are simply too small and too irrelevant to contribute much of anything in the face of a planet with extremely powerful feedback and smoothing mechanisms designed to deal rather well with shocks to current equilibrium states.
It is almost as if the world we live on was... shall we say, DESIGNED to deal with the presence of flawed, Fallen, and broken stupid ape-like children that do idiotic things and soil themselves and everything around them.
But that is a discussion for another time. | 0.806839 | 3.851087 |
Gemini composite image of the field around FRB 121102 (indicated). The dwarf host galaxy was imaged, and spectroscopy performed, using the Gemini Multi-Object Spectrograph (GMOS) on the Gemini North telescope on Maunakea in Hawai'i. Data was obtained on October 24-25 and November 2, 2016. Image Credit: Gemini Observatory/AURA/NSF/NRC.
Full resolution TIFF/JPEG
Gemini Probes Distant Host of Enigmatic Radio Bursts
For Release: 1:00 p.m., EST, (noon CST) Wednesday, 4 January 2017
Gemini Observatory provides critical rapid follow up observations of a Fast Radio Burst – one of modern astronomy's greatest enigmas. These observations provide the first details on a burst's distant extragalactic host.
Fast Radio Bursts (FRBs), sudden rapid explosions of energy from space, have challenged astronomers since their discovery in 2007. Typically lasting only a few milliseconds, many questions remain, including what powers these bursts, their distance beyond our galaxy, and what their host galaxies might look like.
"Now, thanks to deep Gemini observations, we know that at least one of these FRBs originated in a discrete source within a distant dwarf galaxy located some three billion light-years beyond our Milky Way Galaxy," said Shriharsh Tendulkar of McGill University in Montreal, Canada.
Tendulkar and an international team of astronomers presented the results today at the 229th meeting of the American Astronomical Society in Grapevine, Texas. The characterization of the host galaxy was published in The Astrophysical Journal Letters, and accompanied the research team’s results on a campaign to precisely locate the FRB, published in the journal Nature.
The story began with the detection of a burst denoted FRB 121102 which was discovered in November of 2012 at the Arecibo Observatory in Puerto Rico. However, unlike the other 17 known FRBs, this one repeated itself and allowed astronomers to watch for it using the National Science Foundation's Karl G. Jansky Very Large Array (VLA). The VLA radio telescope, composed of 27 antennas in New Mexico, has the ability to see the fine detail necessary to precisely determine the object's location in the sky.
In 83 hours of observing time over six months in 2016, the VLA detected nine bursts from FRB 121102. "For a long time, we came up empty, then got a string of bursts that gave us exactly what we needed," said Casey Law, of the University of California at Berkeley.
"The VLA data allowed us to narrow down the position very accurately," said Sarah Burke-Spolaor, of the National Radio Astronomy Observatory (NRAO) and West Virginia University.
"Once we were able to accurately pinpoint the burst’s location in the two-dimensional sky we enlisted the 8-meter Gemini North telescope on Maunakea in Hawai‘i to characterize the corresponding host galaxy," said Paul Scholz formerly of McGill University and now with the National Research Council of Canada (NRC). "The Gemini observations did that, and for the first time with an FRB, left no doubt about its origin."
"The host galaxy for this FRB appears to be a very humble and unassuming dwarf galaxy, which is only about 1% of the mass or our Milky Way Galaxy," said Tendulkar, who adds that Gemini not only imaged the galaxy, but obtained a spectrum which characterized the galaxy and provided an estimate of its redshift (velocity away from us due to the expansion of the Universe) and thus its distance. "This really gave us a three dimensional lock on the home of this FRB."
"It is surprising that the host would be a dwarf galaxy," adds Tendulkar. "One would generally expect most FRBs to come from large galaxies which have the largest numbers of stars and neutron stars. Neutron stars – remnants of massive stars – are among the top candidates to explain FRBs.
Tendulkar notes that this dwarf galaxy has fewer stars, but is forming them at a high rate, which may suggest that FRBs are linked to younger neutron stars. Two other classes of extreme events – long duration gamma-ray bursts and superluminous supernovae – frequently occur in dwarf galaxies, as well. "This discovery may hint at links between FRBs and those two kinds of events," suggests Tendulkar.
"The collaboration of Gemini working with radio telescopes around the world, each looking at the Universe in such different ways, is what allowed us to make this breakthrough," said Shami Chatterjee, of Cornell University. "The simple fact that we have uncovered an extragalactic host for a fast radio burst is a huge advance in our understanding," he added.
"This impressive result shows the power of several telescopes working in concert – first detecting the radio burst and then precisely locating and beginning to characterize the emitting source," said Phil Puxley, a program director at the National Science Foundation that funds the VLA, Very Long Baseline Array (VLBA), Gemini and Arecibo observatories. "It will be exciting to collect more data and better understand the nature of these radio bursts."
"FRBs are an exciting new area in astrophysics and the CHIME telescope at DRAO is ideal for detecting large numbers of them across the whole sky," says Sean Dougherty, Director of the National Research Council of Canada (NRC) Dominion Radio Astrophysical Observatory (DRAO). In addition to funding a significant portion of Gemini, NRC hosts the Canadian Hydrogen Intensity Mapping Experiment (CHIME) which is an interferometric radio telescope under construction at DRAO in British Columbia. CHIME will survey half the sky each day in search of radio transients.
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The GEMMA Podcast
A podcast about Gemini Observatory and its role in the Era of Multi-Messenger Astronomy. Featuring news related to multi-messenger astronomy (MMA), time-domain astronomy (TDA), our visiting instrument program, and more through interviews with astronomers, engineers, and staff both here at Gemini (North and South) and abroad. | 0.844994 | 3.775809 |
An experiment in the frozen wastes of Antarctica has revealed evidence of a universe born in the same Big Bang as ours – but with rules of physics that are completely the opposite.
At home in Princeton, New Jersey.
That’s something that scientists have long known is theoretically true based on a few facts: Every particle or group of particles in the universe is also a wave—even large particles, even bacteria, even human beings, even planets and stars. And waves occupy multiple places in space at once. So any chunk of matter can also occupy two places at once. Physicists call this phenomenon “quantum superposition,” and for decades, they have demonstrated it using small particles.
But in recent years, physicists have scaled up their experiments, demonstrating quantum superposition using larger and larger particles.
Two newfound galaxies appear to be devoid of the substance, paradoxically providing more proof dark matter exists
Much as a ripple in a pond reveals a thrown stone, the existence of the mysterious stuff known as dark matter is inferred via its wider cosmic influence. Astronomers cannot see it directly, but its gravity sculpts the birth, shape and movement of galaxies. This makes a discovery from last year all the more unexpected: a weirdly diffuse galaxy that seemed to harbor no dark matter at all.
The human tolerance for sound is, on a galactic level, puny. Volcano eruptions, jackhammer-intensive construction work, My Bloody Valentine concerts—these tinnitus-inducing phenomena are barely whispers besides the majestic, roiling bursts and collisions going on in outer space.
Of course, much of this activity is technically soundless—space’s atmosphere lacks the material that make sound waves possible. So for this week’s Giz Asks, we asked experts in astronomy and astrophysics what the loudest sound wouldbe, if sound as we understand it existed up there.
The periodic table stares down from the walls of just about every chemistry lab. The credit for its creation generally goes to Dimitri Mendeleev, a Russian chemist who in 1869 wrote out the known elements (of which there were 63 at the time) on cards and then arranged them in columns and rows according to their chemical and physical properties. To celebrate the 150th anniversary of this pivotal moment in science, the UN has proclaimed 2019 to be the International year of the Periodic Table.
But the periodic table didn’t actually start with Mendeleev. Many had tinkered with arranging the elements. | 0.845427 | 3.717467 |
Some of the people doing polar research these days have their feet on the frozen ground but their eyes on the skies. Conditions of deep cold significantly reduce the chance of biological contamination, making polar ice an excellent place to gather meteorites. Polar environments have also proven to be good places to develop technologies that may one day be used to explore Mars.
The more we observe of worlds like Mars and Jupiter's moon Europa, the more we find similarities--analogs--to environments at Earth's poles; conversely, exploring polar environments may help us explore those other worlds more effectively. This offers opportunities for aspiring scientists whose sights are set on the ends of Earth--and beyond.
Photo: The CMaRS for Antarctic field use.
Left to Right: David Dickensheets, Montana State University, Roger Worland, British Antarctic Survey, David Wynn-Williams, British Antarctic Survey, Chelle Crowder, Montanta State University (Chelle is the graduate student who built the instrument shown in the foreground).
Solar System Samples
The dream of many a planetary scientist is a sample-return mission, bringing back a piece of another world, comet, or asteroid for study, as the Apollo missions did for the moon. But one expedition supplies hundreds of samples each year at a fraction of the cost of a human or robotic space mission. Since 1978, the Antarctic Search for Meteorites ( ANSMET) has sent between four and 12 people at a time to spend austral summers (5 to 7 weeks, generally between mid-November and January) searching glaciers and ice fields for meteorite impacts.
For the past decade, Ralph Harvey has served as ANSMET's principal investigator and leader of its expedition team. "The southern polar region represents a unique platform for observation," he says. "One of the great values of the Antarctic is its areas unspoiled by humans or other biological organisms." This makes the ice fields of the Antarctic ideal for preserving meteorites free from contamination.
"Even the Arctic is extremely different--teeming with life compared to Antarctica. A huge component of arctic research is biology--not the geographically isolated communities of life found in Antarctica, but a whole ecology, including human cultures."
During the 2001-2002 season, the expedition focused on the western end of the Darwin Mountains, in an area named Meteorite Hills following the discovery of numerous meteorites there in 1978. During the season, expedition members live in tents on the ice fields where they search, and they get around on foot or snowmobile, taking full advantage of 24 daily hours of sunlight to peer across blue ice (a "meteorite stranding surface") in search of meteorite specimens.
Searches are systematic: The position of each discovered meteorite is logged, and the meteorite itself is examined, given a numerical designation, removed, and placed in a sterile Teflon bag. The still-frozen specimens are transferred to the Johnson Space Center in Houston, where they are further examined and described in clean-room conditions. Samples are then sent to the Smithsonian Institution in Washington, D.C., where other experts examine them, and they are finally made available to the international research community for study. Over the years, the thousands of samples gathered by ANSMET have greatly increased our knowledge of planetary science.
By now ANSMET's connection to Mars research is well known. It gathered the specimen (EETA79001) that provided conclusive evidence of Mars origin. It has collected five of the 18 specimens identified as coming from Mars, including the specimen ALH84001, collected in 1984 and made famous in 1996 when NASA investigators suggested that secondary materials in the cracks of the meteorite might have been created through processes involving life--although most planetary scientists now think otherwise.
Searching for Life in Antarctica's Dry Valleys
While ANSMET spends time searching mountain ice, other scientists are examining Antarctica's Dry Valleys--among the coldest, driest places in the world--for signs of life. Twenty years ago small isolated colonies of bacteria, algae, and fungi were discovered living there. More recently, scientists from Canada and New Zealand found colonies of bacteria and fungi hidden away in paleosols--ancient soils created by the advance and retreat of glaciers--in conditions that are similar to Mars's past and present.
The search for tiny, microscopic forms of life, including fossilized microbes, requires specialized instruments and cooperation between field researchers and instrument builders. David Wynn-Williams, a microbiologist for the British Antarctic Survey, studies the cyanobacteria that inhabit porous sandstone rocks in the Dry Valleys. Wynn-Williams will soon use a mini Raman spectrometer--called a CMaRS--that he can carry into the field in his backpack to detect the fossilized pigments of ancient cyanobacteria. He is developing a catalog of the biomolecules found in fossilized and living samples that may one day be used in a Mars mission to identify living organisms or their fossilized remains. A Raman spectrometer has been proposed for the Mars Express Lander mission in 2005.
Chris Schoen of TRI Inc. and David Dickensheets of Montana State University, Bozeman, collaborated in the design of the CMaRS, adapting a design originally intended for petroleum industry field work. "A lot of instruments used in scientific investigations are developed as prototypes put together in academic or scientific laboratories," says Dickensheets, whose work on CMaRS is funded by the NASA Astrobiology Institute. His work on the design of miniature optical elements, "small lightweight instruments to be used for remote microscopy inside human beings," became the basis for the microscope attachment that makes CMaRS useful in the field.
Dickensheets came late to the design of instruments for scientific exploration. After getting his bachelor's and master's degrees, he went to work for Hewlett Packard where he worked on biomedical instruments. He became interested in designing instruments for field work when he returned for his Ph.D. at Stanford. "I don't consider myself a polar researcher or a space researcher, but rather an instrument maker," he says. Nonetheless, he is looking forward to his first trip to the Antarctic next year. "I learned from HP to meet with customers first-hand. Seeing it for yourself is an important part of the feedback."
Europa--Life on Ice
Polar research may help us search for life even beyond Mars. Astrobiologists agree that organic life may exist in environments where there are organic chemicals, energy sources, and water. According to planetary geologist Ronald Greeley, "Jupiter's moon Europa, along with Mars and Saturn's moon Titan, tops the list of likely candidates for life." Greeley, chair of the NASA Astrobiology Institute's Europa Focus Group, sees promise in using the discoveries of polar research to understand the chemistry, physics, and biology that may exist on Europa.
Slightly smaller than Earth's moon, Europa contains perhaps three times the volume of water of Earth's oceans. Its surface is frozen ice cracked by the massive tidal forces of Jupiter and nearby satellites. These forces also serve as Europa's energy source, heating its iron-nickel core and creating undersea hydrothermal vents that may circulate heat and minerals. These may also host life forms like those inhabiting hydrothermal vents on Earth.
Life beneath Europa's thick ice surface will be difficult to detect, but polar research suggests that other opportunities to find life may exist. Greeley says, "In the Antarctic, microcracks in the ice often serve as reservoirs for liquid water and cold-tolerant microorganisms to grow and flourish. Similar microcracks within Europa's ice, especially if nourished by brine upwelling from the liquid seas below, may also hold living organisms."
* ANSMET information. Includes maps, journal entries, contact information, and an explanation of the science behind the search for meteorites.
* ANSMET's home page at Case Western Reserve University, Ralph Harvey's home base.
* Home page of the NASA Astrobiology Institute, which includes information on Wynn-Williams's work, the Europa Focus Group, and more.
* Montana State University's Electrical and Computer Engineering Department home page, David Dickensheets's home base.
* Home page of Astrobiology at Arizona State University, Ronald Greeley's home base. Has more information on astrobiology.
* Apply for a NSF research grant to work in Antarctica.
* Teachers Experiencing the Antarctic and Arctic. A site for teachers interested in joining research expeditions at the poles.
According to Harvey, ANSMET seeks volunteers each year for its expeditions. "We've had a hundred different people in 25 years." Harvey is especially interested in involving students or scientists already researching antarctic meteorites. "This is a program that can benefit the researchers themselves, to understand how samples are gathered."
But for would-be professional meteorite hunters, Harvey is less sanguine. "People often train themselves to be clones of their advisor or another scientist. A better tactic is to find a new niche rather than duplicating what's being done. See what isn't being done--that's often where the fruitful paths lie. The world needs only so many meteorite hunters."
"There's a lot of room for growth in the polar sciences--we're still in the exploration and description phase there as far as the science goes. But it's a higher-stakes game than laboratory research. Supporting any kind of research there is expensive. It's guaranteed to be an area where ideas exceed money. On the other hand, there are lots of things to do if you can get there."
Harvey advises students interested in polar or planetary science to "have a specific idea of what you want to accomplish and then seek out an advisor who can guide you in ways known to work. Your relationship with your advisor is one of the most important of your life. Get involved in an existing program and then find your niche. It's a hard thing to do, but put effort into your research design from the very beginning, even as you are learning."
According to Dickensheets, instrument design requires a broad area of expertise. "Physics, computer savvy, real-time computer design, mechanical design, not to mention the ability to understand from your customers what their needs are." Instrument design and construction is often a team effort, and Dickensheets's students, both graduate and undergraduate, have participated in instrument design and construction. He encourages would-be instrument makers to look into university-level science and engineering departments and look for instrument-development projects to get involved in.
Dickensheets has found his experience with commercial instruments to be beneficial, and like most academics in engineering today, trains his students to be practical problem-solvers. "There's a lot of overlap on instruments in the medical and telecommunications sectors. If they don't find work at the Jet Propulsion Laboratory, they can make a good living in private industry."
Greeley, for his part, looks for students and researchers who are "bright, enthusiastic, and reliable." His advice? "Get a bachelor's degree in a basic scientific field--physics, biology, chemistry, astronomy--the basic field doesn't matter for planetary science. Then shop for graduate schools. Go where the action is, and visit and talk with the faculty to make sure you have the right fit." | 0.884647 | 3.530361 |
Mars’ moon Phobos is a pretty fascinating customer! Compared to Mars other moon Deimos, Phobos (named after the Greek personification of fear) is the larger and innermost satellite of the Red Planet. Due to its rapid orbital speed, the irregularly-shaped moon orbits Mars once every 7 hours, 39 minutes, and 12 seconds. In other words, it completes over three orbits of Mar within a single Earth day.
It’s not too surprising then that during a recent observation of Mars with the Hubble space telescope, Phobos chose to photobomb the picture! It all took place in May of 2016, when while Mars was near opposition and Hubble was trained on the Red Planet to take advantage of it making its closest pass to Earth in over a decade. The well-timed sighting also led to the creation of a time-lapse video that shows the moon’s orbital path.
During an opposition, Mars and Earth are at the closest points in their respective orbits to each other. Because Mars and the Sun appear to be on directly opposite sides of Earth, the term “opposition” is used. These occur every 26 months, and once every 15 to 17 years, an opposition will coincide with Mars being at the closest point in its orbit to the Sun (perihelion).
When this happens, Mars is especially close to Earth, which makes it an ideal occasion to photograph it. The last time this occurred was on May 22nd, 2016, when Mars was and Earth were at a distance of about 76,309,874 km (47,416,757 mi or 0.5101 AU) from each other. This would place it closer to Earth than it had been in 11 years, and the Hubble space telescope was trained on Mars to take advantage of this.
A few days before Mars made its closest pass, Hubble took 13 separate exposures of the planet over the course of 22 minutes, allowing astronomers to create a time-lapse video. This worked out well, since Phobos came into view during the exposures, which led the video showing the path of the moon’s orbit. Because of its small size, Phobos looked like a star that was popping out from behind the planet.
This sighting has only served to enhance Phobos’ fascinating nature. As of 2017, astronomers have been aware of the moon’s existence for 140 years. It was discovered in 1877, when Asaph Hall – while searching for Martian moons – observed it from the U.S. Naval Observatory in Washington D.C. A few days later, he also discovered Deimos, the smaller, outer moon of Mars.
In July of 1969, just two weeks before the Apollo landing, the Mariner 7 probe conducted a flyby of Mars and took the first close-up images of the Moon. In 1977, a year after the Viking 1 lander was deployed to the Martian surface, NASA’s Viking 1 orbiter took the first detailed photographs of the moon. These revealed a cratered surface marred by long, shallow grooves and one massive crater – known as the Stickney crater.
Asaph Hall named this crater after Chloe Angeline Stickney Hall (his wife) after discovering it in 1878, a year after he discovered Phobos and Deimos. Measuring some 10 km in diameter – almost half of the average diameter of Phobos itself – the impact that created Stickney is believed to have been so powerful that it nearly shattered the moon.
The most widely-accepted theory about Phobos origins is that both it and Deimos were once asteroids that were kicked out of the Main Belt by Jupiter’s gravity, and were then acquired by Mars. But unlike Deimos, Phobos’ orbit is unstable. Every century, the moon draws closer to Mars by about 1.98 meters (6.5 feet). At this rate, scientist estimate that within 30 to 50 million years, it will crash into Mars or be torn to pieces to form a ring in orbit.
This viewing is perhaps a reminder that this satellite won’t be with Mars forever. Then again, it will certainly still be there if and when astronauts (and maybe even colonists) begin setting foot on the planet. To these people, looking up at the sky from the surface of Mars, Phobos will be seen regularly eclipsing the Sun. Because of its small size, it does not fully eclipse the Sun, but it does make transits multiple times in a single day.
So there’s still plenty of time to study and enjoy this fearfully-named moon. And while you’re at it, be sure to check out the video below, courtesy of NASA’s Goddard Space Center!
Mars’ natural satellites – Phobos and Deimos – have been a mystery since they were first discovered. While it is widely believed that they are former asteroids that were captured by Mars’ gravity, this remains unproven. And while some of Phobos’ surface features are known to be the result of Mars’ gravity, the origin of its linear grooves and crater chains (catenae) have remained unknown.
But thanks to a new study by Erik Asphaug of Arizona State University and Michael Nayak from the University of California, we may be closer to understanding how Phobos’ got its “groovy” surface. In short, they believe that re-accretion is the answer, where all the material that was ejected when meteors impacted the moon eventually returned to strike the surface again.
Naturally, Phobos’ mysteries extend beyond its origin and surface features. For instance, despite being much more massive than its counterpart Deimos, it orbits Mars at a much closer distance (9,300 km compared to over 23,000 km). It’s density measurements have also indicated that the moon is not composed of solid rock, and it is known to be significantly porous.
Because of this proximity, it is subject to a lot of tidal forces exerted by Mars. This causes its interior, a large portion of which is believed to consist of ice, to flex and stretch. This action, it has been theorized, is what is responsible for the stress fields that have been observed on the moon’s surface.
However, this action cannot account for another common feature on Phobos, which are the striation patterns (aka. grooves) that run perpendicular to the stress fields. These patterns are essentially chains of craters that typically measure 20 km (12 mi) in length, 100 – 200 meters (330 – 660 ft) in width, and usually 30 m (98 ft) in depth.
In the past, it was assumed that these craters were the result of the same impact that created Stickney, the largest impact crater on Phobos. However, analysis from the Mars Express mission revealed that the grooves are not related to Stickney. Instead, they are centered on Phobos’ leading edge and fade away the closer one gets to its trailing edge.
For the sake of their study, which was recently published in Nature Communications, Asphaug and Nayak used computer modeling to simulate how other meteoric impacts could have created these crater patterns, which they theorized were formed when the resulting ejecta circled back and impacted the surface in other locations.
As Dr. Asphaug told Universe Today via email, their work was the result of a meeting of minds that spawned an interesting theory:
“Dr. Nayak had been studying with Prof. Francis Nimmo (of UCSC), the idea that ejecta could swap between the Martian moons. So Mikey and I met up to talk about that, and the possibility that Phobos could sweep up its own ejecta. Originally I had been thinking that seismic events (triggered by impacts) might cause Phobos to shed material tidally, since it’s inside the Roche limit, and that this material would thin out into rings that would be reaccreted by Phobos. That still might happen, but for the prominent catenae the answer turned out to be much simpler (after a lot of painstaking computations) – that crater ejecta is faster than Phobos’ escape velocity, but much slower than Mars orbital velocity, and much of it gets swept up after several co-orbits about Mars, forming these patterns.”
Basically, they theorized that if a meteorite stuck Phobos in just the right place, the resulting debris could have been thrown off into space and swept up later as Phobos swung back around mars. Thought Phobos does not have sufficient gravity to re-accrete ejecta on its own, Mars’ gravitational pull ensures that anything thrown off by the moon will be pulled into orbit around it.
Once this debris is pulled into orbit around Mars, it will circle the planet a few times until it eventually falls into Phobos’ orbital path. When that happens, Phobos will collide with it, triggering another impact that throws off more ejecta, thus causing the whole process to repeat itself.
In the end, Asphaug and Nayak concluded that if an impact hit Phobos at a certain point, the subsequent collisions with the resulting debris would form a chain of craters in discernible patterns – possibly within days. Testing this theory required some computer modeling on an actual crater.
Using Grildrig (a 2.6 km crater near Phobos’ north pole) as a reference point, their model showed that the resulting string of craters was consistent with the chains that have been observed on Phobos’ surface. And while this remains a theory, this initial confirmation does provide a basis for further testing.
“The initial main test of the theory is that the patterns match up, ejecta from Grildrig for example,” said Asphaug. “But it’s still a theory. It has some testable implications that we’re now working on.”
In addition to offering a plausible explanation of Phobos’ surface features, their study is also significant in that it is the first time that sesquinary craters (i.e. craters caused by ejecta that went into orbit around the central planet) were traced back to their primary impacts.
In the future, this kind of process could prove to be a novel way to assess the surface characteristics of planets and other bodies – such as the heavily cratered moons of Jupiter and Saturn. These findings will also help us to learn more about Phobos history, which in turn will help shed light on the history of Mars.
“[It] expands our ability to make cross-cutting relationships on Phobos that will reveal the sequence of geologic history,” Asphaug added. “Since Phobos’ geologic history is slaved to the tidal dissipation of Mars, in learning the timescale of Phobos geology we learn about the interior structure of Mars”
And all of this information is likely to come in handy when it comes time for NASA to mount crewed missions to the Red Planet. One of the key steps in the proposed “Journey to Mars” is a mission to Phobos, where the crew, a Mars habitat, and the mission’s vehicles will all be deployed in advance of a mission to the Martian surface.
Learning more about the interior structure of Mars is a goal shared by many of NASA’s future missions to the planet, which includes NASA’s InSight Lander (schedules for launch in 2018). Shedding light on Mars geology is expected to go a long way towards explaining how the planet lost its magnetosphere, and hence its atmosphere and surface water, billions of years ago. | 0.861018 | 3.494412 |
Title: Tracing the Evolution of Active Galactic Nuclei Host Galaxies Over the Last 9 Gyrs of Cosmic Time
Authors: A. D. Goulding, W.R. Forman, R.C. Hixkox et al.
First Author’s Institution: Harvard-Smithsonian Center for Astrophysics
Paper Status: Submitted to the Astrophysical Journal
Astronomers now believe that all galaxies contain a black hole at their centre and the bigger the galaxy, the bigger the black hole. However, we still don’t know how many of these black holes are active. This activity is thought to have an extreme effect by using the galaxy’s own material as fuel and throwing out huge energetic jets; but how much of an imapact does this have on the galaxy? To answer these questions astronomers attempt to study populations of galaxies with active galactic nuclei (AGN) at all redshifts at many wavelengths (X-ray, optical, far-infrared, radio etc.) to observe both the optical stellar population and the jets simultaneously.
Originally this AGN activity was thought to be triggered by galaxy mergers which in turn produce powerful starbursts and possibly a change in the galaxy’s morphology (i.e it’s shape; e.g. from a disc galaxy to an elliptical). However, some of these previous multi-wavelength studies of AGN host galaxies have provided evidence that the majority of galaxy evolution due to AGN activity (galaxy-AGN co-evolution) is dominated by secular processes (slow, calm processes) as opposed to a galaxy mergers (relatively fast, violent processes which destroy disc and spiral arm structures).
In order to study the effect of AGN on their host galaxies, the authors of this paper consider the distribution of the host galaxies out to a redshift of z = 1.4, which corresponds to a look-back time of ~ 9 Gyr (i.e. the light from the galaxies at z = 1.4 was emitted over 9 billion years ago and allows a comparison with maturer galaxies at z=0). They identify the AGN sources using radio , X-Ray and infrared (IR) wavelengths and match them to a host galaxy using an optical sample from various surveys; SDSS, Boötes and DEEP2 which have redshift ranges of 0.05 < z < 0.2, 0.2 < z < 0.7 and 0.7 < z < 1.4 respectively. This sample shows varying degrees of galaxy bimodality (two distinct populations) on the colour-magnitude diagram in each optical survey, as shown in figure 1 below. The “blue cloud” consisting of low mass, blue (and therefore star forming) galaxies is prominent at higher redshifts in the DEEP2 survey (right hand panels), whereas the “red sequence” (higher mass, red, quiescent) galaxies are more prominent in the lower redshift surveys. This shows the evolution of galaxies as they age and star formation begins to cease.
The authors argue that Figure 1 shows that radio luminous AGN are primarily found in massive red sequence galaxies across all redshift ranges; whereas X-ray luminous AGN are evenly spread throughout the colour-magnitude space. This is in conflict with the current picture of the evolution of galaxies with time; however possible evolution of the IR luminous host galaxies, from the blue cloud at high redshift to the red sequence at lower redshift, can be inferred from figure 1. Luckily, the authors also perform Markov-Chain Monte-Carlo two-dimensional Kolmogorov-Smirnov tests between all of the AGN populations to determine if any are statistically similar to each other, i.e. if they are drawn from the same host galaxy population across all redshift and wavelength bands. The statistically significant (P > 95%) results of these tests suggest:
- The X-ray luminous and radio luminous host galaxies maintain similar distributions across all redshifts
- At any given redshift, the radio and infrared luminous AGN exist in separate host galaxy populations
- Similarly, at any redshift the radio and X-ray luminous AGN exist in separate host galaxy populations
The authors argue that the above results are due to the distinctly different accretion processes that drive the activity of the black hole. Whereas the radio luminous AGN are dominated by mechanically efficient processes (low excitation, massive black holes with massive old stellar population hosts providing little fuel), the X-ray/IR luminous AGN are driven by radiatively efficient processes (requiring ample cool gas to fuel higher accretion); suggesting that the triggering mechanism and fueling source are the same for radiatively efficient AGN. They present this picture of AGN evolution with a handy schematic shown in Figure 2.
They also argue that since across all redshifts the host galaxies have similar distributions for those with X-ray/IR AGN (and since there is no statistical evidence to suggest that this is not the case for the radio galaxies) that the general properties of these AGN host galaxies have not changed over the past 9 Gyrs of cosmic time. This suggests a picture where AGN do not drive the evolution of their host galaxies; drastically different to either picture of merger or secular driven evolution discussed earlier.
Finally, since there is also little systematic difference between the underlying general galaxy population and the host galaxies of X-ray AGN, the authors infer that X-ray AGN exist in all galaxy types. This lack of distinction between the two populations gives rise to the conclusion that at some point in cosmic time, a large majority of galaxies will have hosted an actively growing black hole, independent of host galaxy properties (e.g. merger history, luminosity, stellar mass or stellar population).
With these conclusions laid bare, this suggests another mechanism is necessary to explain the quenching of star formation in order to account for galactic evolution across the colour-magnitude diagram with cosmic time*.
*Want to help answer the outstanding questions? Get involved with Radio Galaxy Zoo! | 0.81075 | 4.101235 |
Authors: David Martinez-Delgado, Eva K. Grebel, Behnam Javanmardi, Walter Boschin, Nicolas Longeard, Julio A. Carballo-Bello, Dmitry Makarov, Michael A. Beasley, Giuseppe Donatiello, Martha P. Haynes, Duncan A. Forbes, Aaron J. Romanowsky
First Author’s Institution: Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Heidelberg, Germany
Status: Accepted to Astronomy & Astrophysics, [open access]
Disclosure: One of the authors on this paper (Duncan Forbes) is a faculty member at my university, but I only realized that after I’d already chosen to write about it—I had no involvement in the paper itself.
Despite the title this isn’t a Halloween post accidentally scheduled for Thanksgiving, but a full explanation will take a little while so bear with me: the brightest star in the constellation of Andromeda is known as Mirach, a brilliant 2nd-magnitude red giant star. Located a mere seven arc-minutes away on the sky sits NGC 404, the closest-known lenticular galaxy (the full Moon is about thirty arc-minutes across, for reference). NGC 404 is about ten million light-years away, just beyond the Local Group of galaxies which contains our own Milky Way, the Andromeda Galaxy (Messier 31), the Large and Small Magellanic Clouds, and several dozen dwarf satellite galaxies. Due to NGC 404’s proximity to such a bright star it was historically very difficult to see or photograph it, especially for observers with early telescopes. Its diffuse, nebulous look could easily be mistaken for a blurry internal reflection of Mirach in those early telescopes, which led to its common nickname of “Mirach’s Ghost.” (This fact, combined with its NGC number, meant I really couldn’t help myself making the extremely obvious joke seen in Figure 1.)
Today’s paper covers the discovery of another galaxy a bit further away from Mirach on the sky (about one degree), but so small and diffuse that it was only discovered a few years ago. In September 2016 an amateur astronomer named Giuseppe Donatiello was taking long exposures of the area around the Andromeda Galaxy, when he noticed a faint smudge in one of his images that didn’t match any known features, as seen in Figure 2.
The first author on today’s paper, David Martinez-Delgado, discovered the image after Donatiello posted it on Facebook, and reached out to him to help secure time on professional telescopes for follow-up and make sure he received proper credit for his discovery. (In fact Donatiello’s one of the authors on the paper.) They were able to take observations with both the 3.58-meter Italian Telescopio Nazionale Galileo (TNG) and the 10.4-m Gran Telescopio Canarias (GTC), both part of the Roque de Los Muchachos Observatory on the Spanish islands of La Palma. (The images from these two observations are shown below in Figure 3.) As a recognition of his discovery, the galaxy was named “Donatiello 1.”
Using the observations they’d taken, the authors were able to make estimates of some of Donatiello 1’s properties. It appears to be a dwarf spheroidal galaxy that is no longer actively forming stars, similar to many of the small galaxies orbiting the Milky Way and the Andromeda Galaxy within the Local Group. Nailing down its distance proved difficult, but they were able to constrain it to within about 8.1 to 11.4 million light-years away. This places it comfortably beyond the Local Group, meaning it’s not gravitational bound to it. If it lies around 10 million light-years away from the Milky Way it would likely be only about 211,000 light-years away from NGC 404, and possibly associated with it. Interestingly, there is some evidence that NGC 404 has undergone a collision or interaction fairly recently; it’s been discovered to have a ring of on-going star formation, unusual for a lenticular galaxy. Donatiello 1 is also noticeably elongated and non-spheroidal, suggesting a possible recent interaction with NGC 404, but the authors note that more research will be needed to explore this intriguing possibility.
In these days where professional telescopes are getting bigger and faster all the time, it’s inspiring to know that amateur astronomers can still make important discoveries like this. Amateur and professional astronomers have long worked together to uncover new aspects of the universe, and who knows what new wonders are waiting to be discovered out there tomorrow! | 0.811509 | 3.760332 |
On a summer day in 2017, astronomers around the world received a message about an exciting collision of two stars far, far away. The message was sent by a team of astronomers from the LIGO and Virgo observatories. These new observatories are very different from the telescopes we have used to study our Universe up until now. LIGO and Virgo are gravitational wave observatories, listening for quiet ripples in spacetime created by the collisions of distant black holes and neutron stars. On August 17, 2017 LIGO and Virgo detected a signal that astronomers named GW170817, from the collision of two neutron stars. Less than two seconds later, NASA's Fermi satellite caught a signal, known as a gamma-ray burst, and within minutes, telescopes around the world began searching the sky. Telescopes in South America found the location of the collision in a distant galaxy known as NGC 4993. For the weeks and months that followed, astronomers watched the galaxy and the fading light from the collision. This is a new kind of multi-messenger astronomy where, for the first time, the same event was observed by both gravitational waves and light.
The stars in the night sky may seem like they have been there forever, but each star was created from gas and dust in space pulled together by gravity. A newly born star burns brightly until it runs out of fuel. Small- and medium-size stars like our own Sun end their lives as white dwarf stars, the glowing remains of the star's core. Stars much bigger than our Sun die a spectacular death, exploding as supernovae. The remains of a supernova explosion is a dense, dark core, either a neutron star or a black hole. The idea of a neutron star was first presented over 80 years ago, in 1934, but it was another 33 years before astronomers found a neutron star. In 1967, X-rays were detected from a distant neutron star and later the same year, the first radio pulsar was discovered. A pulsar is a highly magnetized neutron star that is spinning, sending a beam of radio pulse toward the Earth with each spin. Radio telescopes here on Earth can watch these pulses, which arrive like a steady ticking clock. Astronomers have also found binary neutron star systems, with two neutron stars orbiting around each other. When scientists planned to build the new LIGO and Virgo gravitational wave detectors, they hoped to find gravitational wave signals from some of these binary neutron star systems (Figure 1).
Over 100 years ago, Albert Einstein presented the Theory of General Relativity—a description of gravity that predicts black holes and curved spacetime. The theory also predicts gravitational waves, which are ripples in space and time that travel at the speed of light, created by the acceleration of massive objects, such as black holes and neutron stars. In September of 2015, the National Science Foundation's newly upgraded Advanced LIGO detectors observed the first gravitational wave signal from the collision of two black holes in a distant galaxy . The event was named GW150914, for the gravitational wave (GW) signal detected in 2015 on September 14. The Laser Interferometer Gravitational wave Observatory (LIGO) detectors are located in Hanford, Washington and Livingston, Louisiana in the United States. Together with the European Virgo detector in Italy, they form a network of gravitational wave observatories that detected 10 separate gravitational wave signals from pairs of colliding black holes in their first two observing runs from 2015 to 2017. In the northern hemisphere summer of 2017, the observatories detected a new type of signal, one that came from the collision of two neutron stars .
Gamma-rays are a kind of light even more energetic than X-rays. In the mid-1960s, gamma-ray bursts (GRBs) were discovered by the Vela satellites. Astronomers later found that these GRBs came from space, but what could create such high energy gamma-ray bursts? Determining the sources of GRBs has been one of the key challenges in high-energy astrophysics ever since. In 2005, a short-duration gamma-ray burst (sGRB) was discovered to come from a distant galaxy and observations provided evidence that sGRBs might be the result of the collision of two neutron stars or the merger of a neutron star with a black hole. These very distant events are difficult to find, so it took a new kind of astronomy and the development of sensitive gravitational wave detectors to discover the neutron star collision that created the GW170817 gravitational wave signal and the GRB detected by the NASA Fermi satellite on August 17, 2017.
A Multi-Messenger Discovery
On August 17, 2017, NASA's Fermi satellite sent an automatic alert about a gamma-ray burst signal, now known as GRB170817A . It took about 6 min for LIGO computers to find that a possible gravitational wave signal was detected at almost the same time at the Hanford observatory. The gravitational wave signal appeared to be from the collision of two neutron stars observed 2 s before the gamma-ray burst signal. LIGO and Virgo scientists issued an alert to astronomers around the world and, shortly after, they shared a map of the area of the sky that was most likely the source of the gamma-ray burst and gravitational wave signals, shown in Figures 2, 3.
This event marked the first gravitational wave multi-messenger discovery: it was observed by both gravitational waves and light, which is also known as electromagnetic waves. At the time of the alert it was afternoon in the Western Hemisphere and, by nightfall, telescopes in South America were well-placed to search the sky for light from the collision. In the first few hours of darkness, a handful of telescope found a new bright source in the galaxy NGC 4993. Telescopes around the world turned to NGC 4993 to see what would happen next. Over the next 2 weeks, a network of ground-based telescopes and space-based observatories followed up on the initial detections. Observations were made in all the different kinds of light, with telescopes that could measure signals including ultraviolet, optical, and infrared light. Astronomers discovered that the new source of light was a kilonova, a bright short-lived event caused by the collision of two neutron stars. Following the kilonova, that part of the sky was watched with X-ray and radio telescopes to better understand the collision. These observations revealed important information about the energy output of the explosion, the ejected material, and the environment of the collision. These observations showed us that neutron star collisions are able to create heavy elements, including gold, confirming what had only been a hypothesis before the measurement. Neutrino observatories searched without success for, high-energy neutrinos coming from the area of GW170817. It is a goal of multi-messenger astronomy to detect gravitational waves, electromagnetic radiation, and neutrinos from the same cosmic event . Since the gravitational wave and gamma-ray burst signals occurred at nearly identical times, we now have confirmation of Einstein's prediction that gravitational waves and light waves travel at the same speed, over millions of kilometers.
The New Astronomy
The discovery of the gravitational wave signal GW170817 and the gamma-ray burst detected by the Fermi satellite on August 17, 2017 marked the first time both gravitational waves and light from a single astrophysical source had been observed. The LIGO and Virgo gravitational wave observatories sent an alert to astronomers around the world to search for light from the collision of two neutron stars. Telescopes found the location of the collision in a distant galaxy and, for the following weeks and months, astronomers watched and recorded the fading light from the collision. This event is the first time the same event was observed by both gravitational waves and light, showing how important it is for astronomers to work together to make new and exciting discoveries in a new era of multi-messenger astronomy.
Neutron Star: ↑ The extremely dense object that remains after the collapse of a massive star.
Black Hole: ↑ A region of spacetime, caused by an extremely compact mass, where the gravity is so intense it prevents anything, including light, from escaping.
Gamma-ray: ↑ The highest energy light, also known as electromagnetic radiation.
Neutrino: ↑ Tiny particle with no electric charge.
Multi-messenger Astronomy: ↑ Using electromagnetic, gravitational-wave, and astro-particle data together to learn about the Universe.
Conflict of Interest
The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Original Source Article
↑Abbott, B. P., Abbott, R., Abbott, T. D., Acernese, F., Ackley, K., Adams, C., et al., LIGO Scientific Collaboration, Virgo Collaboration, Multi-Messenger Partners. 2017. Multi-messenger observations of a binary neutron star merger. Astrophys. J. Lett. 848:L12. doi: 10.3847/2041-8213/aa91c9
↑ LIGO Scientific Collaboration and Virgo Collaboration. 2016. Observation of gravitational waves from a binary black hole merger. Phys. Rev. Lett. 116:061102. doi: 10.1103/PhysRevLett.116.061102
↑ LIGO Scientific Collaboration and Virgo Collaboration. 2017. GW170817: observation of gravitational waves from a binary neutron star inspiral. Phys. Rev. Lett. 119:161101. doi: 10.1103/PhysRevLett.119.161101
↑ Abbott, B. P., Abbott, R., Abbott, T. D., Acernese, F., Ackley, K., Adams, C., et al., LIGO Scientific Collaboration, Virgo Collaboration, Multi-Messenger Partners. 2017. Multi-messenger observations of a binary neutron star merger. Astrophys. J. Lett. 848:L12. doi: 10.3847/2041-8213/aa91c9
↑ LIGO Scientific Collaboration, Virgo Collaboration, ANTARES, IceCube, and Pierre Auger Observatory. 2017. Search for high-energy neutrinos from binary neutron star merger GW170817 with ANTARES, IceCube, and the Pierre Auger Observatory. Astrophys. J. Lett. 850:L35. doi: 10.3847/2041-8213/aa9aed | 0.844141 | 4.031383 |
Looking beyond our first journeys to Mars in the 2030s, and perhaps setting up outposts there in the 2040s, a frequently-mentioned plan for commercialization of space often brings up the prospects of interplanetary mining. A bit of careful thought can define the prospects and successes for such a venture if we are willing to confront them honestly.
The biggest challenge is that the inner solar system out to the asteroid belt is vastly different than the outer solar system from Jupiter to the distant Kuiper Belt. It is as though they occupy two completely separate universes, and for all intents and purposes, they do!
The inner solar system is all about rocky materials, either on accessible planetary surfaces and their moons, or in the form of asteroids like this photo of asteroid Vesta. We have studied a representative sample of them and they are rich in metals, silicates and carbon-water compounds. Lots of fantastic raw materials here for creating habitats, building high-tech industries, and synthesizing food.
Humans tend to ‘follow the water’ and we know that the polar regions of Mercury and the Moon have water-ice locked away in permanently shadowed craters under the regolith. Mars is filthy rich with water-ice, which forms the permanent core of its polar caps, and probably exists below the surface in the ancient ocean basins of the Northern Hemisphere. Many asteroids in the outer belt are also rich in water, as are the occasional cometary bodies that pass through our neighborhood dozens of times a year.
The inner solar system is also compressed in space. Typical closest distances between its four planets can be about 30 million miles, so the technological requirements for interplanetary travel are not so bad. Over the decades, we have launched about 50 spacecraft to inner solar system destinations for a modest sum of money and rocketry skill.
The outer solar system is quite another matter.
Just to get there we have to travel over 500 million miles to reach Jupiter…ten times the distance to Mars when closest to Earth. The distances between destinations in the outer solar system are close to one billion miles! We have sent ten spacecraft to study these destinations. You cannot land on any of the planets there, only their moons. Even so, many of these moons (e.g those near Jupiter) are inaccessible to humans due the intense radiation belts of their planets.
The most difficult truth to deal with in the outer solar system is the quality of the resources we will find there. It is quite clear from astronomical studies and spacecraft visits that the easiest accessible resources are various forms of water and methane ice. What little rocky material there is, is typically buried under hundreds of kilometers of ice, like Saturn’s moon Enceladus shown here, or at the cores of the massive planets. The concept of mining in the outer solar system is one of recovering ice, which has limited utility for fabricating habitats or being used as fuel and reaction mass.
The lack of commercializable resources in the outer solar system is the biggest impediment to developing future ‘colonization’ plans for creating permanent, self-sustaining outposts there. This is dramatically different than what we encounter in the inner solar system where minable resources are plentiful, and water is far less costly to access than in the outer solar system.
Astronomically speaking, we will have much to occupy ourselves in developing the inner solar system for human access and commercialization, but there is a big caveat. Mined resources cannot be brought back to Earth no matter how desirable the gold, platinum and diamonds might be that are uncovered. The overhead costs to mine and ship these desirable resources is so high that they will never be able to compete with similar resources mined on Earth. Like they say about Las Vegas, ‘what is mined in space, stays in space’. Whatever resources we mine will be utilized to serve the needs of habitats on Mars and elsewhere, where the mining costs are just part of the high-cost bill for having humans in space in the first place.
The good news, however, is that the outer solar system will be the playground for scientific research, and who knows, perhaps even tourism. The same commercial pressures that will drive rocket system technology to get us to Mars in 150 days, will force these trips to take months, then weeks, then days. Once we can get to Mars in a week or less, we can get to Pluto in a handful of months, not the current ten-year journeys. Like so many other historical situations, scientific research and tourism became viable goals for travel as partners to the political or commercial competition to get to India in the 1500s, the Moon in the 1960s…or Mars in the 2000s.
In the grand scheme of things, we have all the time in the world to make this happen!
For more about this, have a look at my book ‘Interplanetary Travel:An Astronomer’s Guide’, for details about resources, rocket technology, and how to keep humans alive, based upon the best current ideas in astronomy, engineering, psychology and space medicine. Available at Amazon.com
Check back here on Friday, December 30 for the next installment! | 0.829572 | 3.342644 |
Discovery of a rare quadruple gravitational lens candidate with Pan-STARRS
Astronomers from the United States Naval Observatory (USNO) in conjunction with colleagues from the University of California, Davis, and Rutgers University have discovered the first quadruple gravitational lens candidate within data from the Panoramic Survey Telescope and Rapid
Response System (Pan-STARRS) using a combination of all-sky survey data from the USNO Robotic Astrometric Telescope (URAT) and the Wide-field Infrared Survey Explorer (WISE).
USNO graduate student George Nelson, who was performing a URAT variability study of the brightest quasars identified by USNO astronomers using WISE colors, discovered the lens while investigating the optical properties of a bright quasar sample. The paper describing this serendipitous discovery has been accepted for publication in the
Astrophysical Journal. A preprint of the paper may be found at arxiv.org/abs/1705.08359. A paper confirming the discovery by a separate team of astronomers using the Keck Cosmic Web Imager has been submitted to the Astrophysical Journal Letters. A preprint of this paper may be found at arxiv.org/abs/1707.05873.
Since the discovery of the first gravitationally lensed quasar in 1979, gravitational lenses have become powerful probes of astrophysics and cosmology. Because they require a very specific configuration between a background quasar (a bright, distant object powered by a supermassive black hole) and a foreground lensing galaxy, quadruply lensed quasars are especially rare. In fact, to date there are only about three-dozen such objects known over the entire sky.
Gravitational lenses are a manifestation of gravity's ability to bend light, which was predicted by Einstein's general theory of relativity in 1915. Since then many experiments have been carried out to test this theory starting with Sir Arthur Eddington's observations of light bending during a solar eclipse in 1919. When a galaxy acts as a gravitational lens to a background quasar, the lensed quasar appears as dual or quadruple images, depending on the relative location of the lens and the source. Lenses are rare because they require that the galaxy and the quasar be located within a few arcseconds of each other on the sky.
Gravitational lenses are at the forefront of current research in cosmology and astrophysics. In astrophysics, they have been used to uncover the structure of massive galaxies, to study how supermassive black holes relate to their host galaxies, and to gain insight into quasar accretion disks as well as their black hole spin. In cosmology, they have contributed to measuring the distribution of dark matter around galaxies and the expansion history of the universe.
Future radio, X-ray, Hubble Space Telescope and adaptive optics imaging, as well as spectroscopic studies, are already planned to further the study of this lens and to contribute to fundamental research. | 0.901895 | 3.993859 |
The mission and the data tapes reveal the first discovery of the Space Age.
"The successful orbiting of Explorer I is one of the landmarks in the technical and scientific history of the human race. Its instrumentation revealed the existence of radiation belts around the Earth and opened a massive new field of scientific exploration in space. It inspired an entire generation of young men and women in the United States to higher achievement and propelled the Western World into the Space Age.” James Van Allen, March 31, 1970
Explorer I lifted off from Cape Canaveral at 10:48:16 on Jan. 31, 1958,
a mission hastily salvaged to redeem American honour, launched in the shadow of two Sputniks already in orbit. Both had beat the U.S into space. The Explorer I satellite emerged from a sidelined mission that, sanctioned earlier, could have reached orbit a year before the Sputniks launched. It took flight with a cosmic ray detector invented by physicist James Van Allen and his graduate students in the basement of the University of Iowa’s 1910 physics building. Van Allen candidly called this extraordinary mission a “shakedown” operation that succeeded on “fool’s luck.” Clearly even he didn’t expect the instrumentation to reveal the first discovery of the space age – the existence of Earth’s radiation belts that set the course for remapping the solar system. But the achievement was obvious by the time he reflected on the space age in March, 1970.
Explorer I transmitted data about charged particles including cosmic rays to a global picket fence of radio receivers that tuned in on the satellite signal as it flew over Tokyo, Lima, Antigua, Havana, Nigeria, Singapore, the Jet Propulsion Laboratory’s Codolock station, Patrick Air Force Base in Florida and the San Gabriel Radio Club in California. Data poured in, recorded on 694 Scotch reel-to-reel magnetic audio tapes. NASA didn’t exist yet. The U.S. Army steered Explorer I into space with a Jupiter C rocket but the data tapes were shipped to Iowa City and Van Allen’s basement laboratory.
The deluge of tapes arrived in metal canisters and cardboard sleeves, labelled with the collection time and location. Graduate student George Ludwig, a key participant in building the cosmic ray detector, logged 120 pages of data from the Explorer I tapes. The charged particle counts from space rose and fell with the rising and falling pitches in a staccato concert of tones on the tapes. But Ludwig riddled the log with entry upon frustrating entry that read “no data” where gaps in the recordings bristle with static. Listen to them yourself on this website. And then remember that the gaps played the music of discovery to just the right listeners. With immense courage and interpretive ingenuity, Van Allen and his team found – not in the data but in the gaps - the totally unexpected phenomenon of the radiation belts. The data tapes aren’t merely a record of that first discovery in space history. They are space history. They are the original and only record of Explorer I’s calls home.
This is the story of Explorer I, the radiation belts and the effort to preserve the data tapes. The 694 Explorer I tapes and those from numerous other early missions lined shelves for half a century in the basement of the old physics building, now MacLean Hall. MacLean and four other buildings surround Iowa’s stately Old Capitol on the hilltop Pentacrest of the campus. Still, during the devastating floods of 2008, puddles collected on the floor of an old particle accelerator chamber where the tapes were archived and some of them began to mold. Now, restored and newly digitized, the tapes will play the chorus of the early space age for generations to come. You may be among the first to hear some of these tapes. Pressed by deadlines for more instruments on other space missions, the frantic pace escalated in the basement warren. Van Allen saw no reason to plow through every data tape. He moved on to the new data from the next mission.
Countdown to Explorer I
Sputnik beats American into Space
Shocked Americans listened to Sputnik’s A-flat beep – beep – beep on ham radios and news broadcasts for the first time on Oct. 4, 1957. People caught glimpses with their naked eyes of the silvery polished sphere orbiting above them. They marveled - and cringed. What kind of surveillance could the little artificial moon capture? What weapons might come next?
University of Iowa physicist James Van Allen was sailing south toward Antartica on the Navy ice breaker USS Glacier that day. The Glacier opened its deck to Van Allen’s rockoons, his balloon-launched rockets that kept him in space exploration on a shoe-string college budget. The quirky but highly efficient hybrid meant stringing surplus rockets from surplus Skyhook weather balloons. Carried upward some 10 miles by balloons filled with helium, on the deck Van Allen launched the rockets remotely via radio at atmospheric heights with far less air resistance. From there the rockets could reach altitudes of about 60 miles, close to double the target range of the 52 Loki rockets he cached for the voyage at a cost of about $320 per assembly, not counting travel and freight. Of course there were some challenges. The rockets wouldn’t fire in the cold and Van Allen had to wrap them in an insulating sleeve and tuck a 32-ounce can of heated juice in the firing box to solve the problem. But the altitudes meant Van Allen could continue to explore the streams of cosmic rays hurling toward Earth from across the galaxy. He and grad student Larry Cahill launched a rockoon from near the equator that afternoon, the flawless rockoon flight Number 76.
In the time it took Van Allen to go below deck to his makeshift lab and write the mission assessment in his field log, the world changed forever. Cahill burst in with the news of Sputnik. Van Allen, Cahill and ship officers quickly found Sputnik’s signature beep and pooled equipment to chart the signal and confirm that it came from a satellite in orbit. They measured the Doppler shift, the rise and fall of the frequency of Sputnik’s beep as it approached and passed overhead, the same shift that accounts for the change in tone of a train whistle as the train heads away.
Sputnik’s Doppler shift measured from the ship matched perfectly with altitude the Russians reported for Sputnik. Van Allen wired his confirmation to the scientific community meeting at an international gathering in Washington, D.C. The next day, he returned to his field log. The field logs filled an entire shelf of brown-backed ledgers in Van Allen’s Iowa City office. With hundreds of entries dating back to the 1940s, only one storms beyond impartial scientific observations and that one entry is the 17-page appraisal of Sputnik. “Yesterday night – the 4th -was very exciting for me (as well as for the civilized world in general,” he begins. “Brilliant achievement!” But then he lambasts the U.S. debacle that squandered an easy victory to reach orbit first.
While an ocean separated Van Allen from the shared furor across America, his graduate student George Ludwig stood in the middle of it. Ludwig gathered with scientists from around the world for five days of meetings for the International Geophysical Year and then joined everyone at a cocktail party hosted by the Soviet Embassy. While the guests sipped vodka and feasted on caviar, New York Times science reporter Walter Sullivan was summoned to the phone and the Washington bureau chief told him Sputnik was orbiting overhead. Sullivan informed IGY vice president Lloyd Berkner of the news. Berkner climbed on a chair, called the revelers to order and announced the Sputnik triumph. Reporters poured into the embassy, a citadel of secrecy where news now flowed as freely as the drinks. Sputnik literally meant “companion to Earth,” adding a bit of poetry to the technological milestone.
By the time the IGY was first envisioned in 1950, scientists had been promising each other for years that it was time to launch a satellite. IGY needed a crown jewel for the year-long program of international research. Organizers threw down the gauntlet, calling for a satellite to orbit the Earth and igniting the space race. There were only two contenders for this first lap of the race – the U.S and the Soviet Union. Americans complacently assumed that the U.S. would prevail. Van Allen knew as few others did that America had held the winning hand – and then bet it away on the wrong rocket.
Cut off from home, Van Allen didn’t know that a political firestorm was resurrecting the orphaned space mission that he, space visionary Wernher von Braun and Caltech’s Jet Propulsion Laboratory turned into the Explorer I mission.
World War II Rocketeers
Von Braun, the son of a baron with a gift for rocket-making, decided he wanted to explore space when he was 12 years old and never turned back. He joined a popular rocket club as a young engineering student in Berlin and his technical flair soon caught the attention of the German military. When the Nazis took over Germany, they commandeered von Braun’s talents and then arrested him in their motivational plan to redirect his sights from space launches to more down to earth weapons. He and his rocket team created the massive V-2 rockets that terrorized London and Antwerp. As the Russians closed in on the underground rocket plant at Nordhausen, von Braun shuffled through conflicting orders to justify an imaginary rocket mission for himself, half his rocket staff and their families and as many papers as he could transport in a truck caravan that moved west in the dead of night to be “captured” by the Americans. When the Americans moved in on Nordhausen later, they found tools still on the ground and 100 rockets in various stages of completion beneath the bright lights of a ghost town. The rockets and documents filled 300 freight cars for transfer to White Sands Proving Grounds in New Mexico and the rocketeers settled under house arrest at Fort Bliss in El Paso where Texas steaks became an instant hit. The other half of von Braun’s rocket team landed in Russia. Now both groups raced to build ballistic missiles, unleashing the Cold War once the Soviets developed their own atom bomb in 1949.
Testing on the V-2 began at once with General Electric and von Braun working together to reassemble and build parts under Army supervision at White Sands. The actual nose cone cavity that could hold a payload of weapons wasn’t needed and Army brass decided to invite a group of renegade scientists eager to load their instruments in a rocket and bring experiments into space. Most researchers wanted nothing to do with vehicles that might crash land carrying a precious cargo of detectors, scintillators and cameras. They preferred to stick to research with a graceful ride in a balloon even though the V-2 could reach altitudes that human beings had never touched before. Among the renegades, Van Allen raised his hand and got a seat for his cosmic rays detectors on the first V-2 test flight on April 16, 1946. Sure enough, as the rocket lifted, it began to veer off course and von Braun radioed a fuel cut-off command that sent it hurtling to the ground. Van Allen shrugged and returned to his home base of the Applied Physics Laboratory in Silver Spring, Md., to rebuild. He already had a lot of experience with this sort of thing - he too had been building weapons during World War II.
America's first smart weapon to the rescue
With a freshly minted Ph.D. in nuclear physics, Van Allen headed to the Department of Terrestrial Magnetism of the Carnegie Institution in Washington, D.C., and soon joined the war effort at the fledgling Applied Physics Laboratory created at Johns Hopkins University in Maryland.
Many young nuclear physicists found themselves recruited to the secret Manhattan Project at Los Alamos in New Mexico to build the atom bomb. Van Allen started work with an equally secret corps inventing America’s first smart weapon, a proximity fuze for the antiaircraft guns in the South Pacific. The shipboard guns shot missiles with time fuses – fire them and the missiles exploded after a designated interval whether or not a target was in range.
But the proximity fuze was a “smart” weapon encasing a miniature radio. It transmitted a signal and, if an aircraft target was in range, the signal radioed back to the fuze to fire it. Development of a radio that could stand up to a missile blast presented enormous challenges. Van Allen tested fuze after fuze but tiny wire filaments needed for the vacuum tubes in the radio shattered every time with the force of firing. In an era before transistors and semi-conductors, vacuum tubes were critical to controlling electrical signals. Van Allen decided the filaments needed a shock absorber and he replaced the rigid wires with metal springs. The spring-loaded vacuum tubes in the proximity fuze held together and the Navy enlisted Lt. James Van Allen and sent him off to the South Pacific to demonstrate the new weapons to the gunnery officers.
Yellowing wartime orders neatly filed in a folder show Van Allen hopscotching across the Pacific from ship to ship to “sell” the fuze gunnery officer by gunnery officer. But the gunners wanted nothing to do with the new weapon at first. Even when their tried and true timed fuses didn’t hit anything, they at least gave off a comforting explosion. With no target in sight, the proximity fuzed missiles plummeted silently into the ocean. But the furious barrage of enemy aircraft strikes during the Battle of the Philippine Sea on June 19-20, 1944, tested the proximity fuze and proved its might. It gave gunners a six times better chance of hitting an enemy aircraft and they brought down 425 planes in those two days – 75 percent of the air power massed against them.
Van Allen’s knowledge of creating devices that could hold up to a missile launch, his acceptance of the failed launches that came with the territory of rocketry and his ability to design simple, reliable detectors gave him and a handful of others the skills combined with dogged determination to begin space exploration at White Sands. His temerity paid off. On July 29, 1947, on the 30th U.S. flight of a V-2 rocket, Van Allen’s counters hit a plateau where the rising cosmic ray counts steadied and dropped just before they collided with the upper atmosphere.
“Dip at about 100 seconds has appeared before in a counter,” he wrote in his log. “May be real!”
The counts fell off at about 31 miles above Earth, where Van Allen found a steady stream of cosmic ray particles, a plateau that marked a very real ceiling in the atmosphere for incoming cosmic radiation.
So, what are cosmic rays?
Ray guns and x-ray vision dominate countless plots in science fiction but cosmic rays are a physical fact, carrying the fingerprints of some of the most cataclysmic forces in the universe. When aging stars begin to run out of fuel, they collapse toward their cores and finally explode into a supernova, with shock waves powerful enough to strip the nucleus from an atom, accelerate it to near light speed and hurl it across the galaxy. Viennese physicist Victor Hess, took a newly invented detector nearly a mile above Earth in a balloon in 1912 and he found radiation levels there some four times as intense as those at the surface. American physicist Robert Millikan later coined the phrase cosmic rays, theorizing that the source of ionizing radiation that rose in intensity with altitude must arise from beyond our solar system and even beyond our galaxy.
Geophysicist Scott Forbush’s global measurements of cosmic rays at the Department of Terrestrial Magnetism fascinated Van Allen. He admired the older man with his shock of white hair, his prism-thick glasses and his mean hand at poker. Forbush became Van Allen’s mentor as a debate simmered between rival scientists over cosmic rays. Many of them believed that some 30-plus miles of blue sky – the protective layers of Earth’s atmosphere – scrubbed most of the primary cosmic rays into showers of secondary particles. Others thought the primaries jetted right through. But no one could reach altitudes high enough to test the competing theories.
Then Van Allen sent his detectors up in the V-2 rocket and found the steady stream of incoming cosmic rays at 31 miles above Earth. And his detectors found the debris of nuclear reactions in the stream of cosmic rays bombarding the atmosphere, evidence validating previous findings that protons, not electrons made up the dramatic cosmic ray bursts that splintered into pions, gamma-rays, muons and neutrinos as they collided with the atmosphere.
This wasn’t the only find with the V-2. Scientists reaped new information about weather currents and they reached and identified layers of the atmosphere – the ozone layer and the ionosphere, long known to mirror back radio waves that made radio transmission possible.
With higher altitudes within his grasp, Van Allen wanted to measure the impact on cosmic ray intensity of Earth’s magnetic field as it arched toward the poles and show how intensity changed with intense solar explosions such as solar flares. He wanted to do so by launching his detectors on rockets at the equator and comparing results at different latitudes as he approached the poles. A shipboard launch out in the middle of the ocean was the most sensible way to accomplish a nomadic itinerary of launches. But the heavy, four-story V-2 wasn’t a good candidate for such a program and a quick count told Van Allen the inventory of them would soon run out. Always planning ahead, he invented the Aerobee, a far smaller, work-house rocket designed strictly for science in space.
A group of influential scientists visiting the Applied Physics Laboratory early in 1950 came to Van Allen’s small white frame house for dinner and Abbie Van Allen topped off the meal with her famous seven-layer chocolate cake. Van Allen credited the cake for the group’s sudden inspiration to ignite plans for another International Geophysical Year. It had been nearly a generation since the last geophysical year – a year of cooperative study of Earth’s surface, atmosphere and magnetic field. As plans moved forward, organizers set the goal of placing a satellite in orbit. As the challenge became an immediate contest between Russia and the United States, Van Allen began designing a detector that could measure cosmic rays intensities in a whole new arena. But he took a permanent detour back to Iowa on his way to outer space.
Return to Iowa
In 1951, Van Allen came home after his alma mater the University of Iowa offered him the chair of the Department of Physics and Astronomy. He liked to quip that Long Island-bred Abbie skeptically asked, “Where’s Iowa?”
He returned to the 1910 physics building where he had earned his Ph.D. assessing a critical nuclear reaction on a temperamental early particle accelerator. He had helped build this beast with recycled parts junked from gasoline pumps and lots of faith in glyptal, and a vacuum sealant goop made by General Electric. Now, Van Allen’s return brought one enormous problem for a space explorer – a net zero budget to continue his research. He couldn’t afford to fly his own Aerobee rockets any longer. He quickly applied small-town Iowa ingenuity
to space missions by calling on contacts in the Navy and at the Jet Propulsion Laboratory to obtain the balloons and rockets for his rockoons.
He hitched rides on a series of ice breakers for annual trips that brought him near the poles, shooting rockets from various latitudes along the way as he had planned. And, just as quickly, he began recruiting a series of brilliant graduate students into a space program they hadn’t known existed five minutes before they walked into his office. George Ludwig was one of them, an Air Force pilot with an instinct for electronics who returned to his father’s Iowa farm when he completed military service.
Fairly confident that von Braun’s next generation of rockets, under construction at the Army Ballistic Missile Agency (now the Marshall Space Flight Center) in Huntsville, Ala., would carry the first satellite into space and knowing von Braun had a satellite in the works, Van Allen and Ludwig began to develop a cosmic ray detector for orbit. Then, suddenly, in 1955 all bets were off as politics invaded the space race.
Launch to Discovery
Making artificial Moons
How would the Russians react if a military rocket launched a satellite into orbit, trespassing over their air space with an artificial moon? For the Eisenhower administration, the question hung in the unchartered boundary marking the “freedom of space.” And it became a factor in selecting the Navy’s Project Vanguard over the Orbiter that von Braun and the Army proposed for the race to get a satellite into space. The Jupiter C military booster rocket and JPL’s upper stages existed already but configuring them together, testing them and completing the satellite was to take an estimated 18 months. The Naval Research Laboratory offered the Vanguard as an alternative rocket and satellite system that could be designed and built for civilian space exploration in the about same amount of time – 18 months. All things being equal, an advisory committee backed the Vanguard as America’s official satellite mission in 1955 despite the committee chairman’s heated pleas and objections.
Delays soon plagued the untried Vanguard while orders to abandon Army satellite development officially handcuffed von Braun’s project. Still, von Braun and his team moonlighted on the mission on their own time. Ernst Stuhlinger, a key physicist on the team, worked in his garage, creating the hand-operated detonator to fire the upper stages of the rocket. He also designed an apex calculator to predict when the Jupiter C had reached its highest point, the point where the upper stages must be fired with split-second timing. Josef Boehm worked on perfecting the satellite from a design he and von Braun nurtured over the years.
Testing went forward on the Jupiter C booster rocket, with JPL’s two upper stages and a dummy payload in the nosecone as part of the Army’s ballistics program. Military brass kept the program under surveillance, though, so no one could sneak a stowaway satellite in that nosecone instead. A perfect test on Sept. 20, 1956 propelled an inert fourth-stage payload at the thrust and altitude needed to inject a live satellite into orbit. The launch convinced the von Braun team that they could have sent a satellite into orbit that day, more than a year ahead of Sputnik. Stuhlinger phoned his trusted friend James Van Allen with the news.
At White Sands, the American scientists and the German rocketeers generally kept their distance. But the courtly Stuhlinger bridged the gap, climbing up ladders with the experimenters to the nose cone of the gleaming, four-story V-2 to check instruments and secure battery connections. Van Allen characterized him as the “ombudsman” for the scientists and a kindred spirit. He and Stuhlinger shared an interest in cosmic rays and detectors. Stuhlinger had studied with Hans Geiger in Germany in the 1930s and helped develop the Geiger counter used to detect nuclear reactions and cosmic rays.
Stuhlinger first approached Van Allen about building a cosmic ray instrument
for a small experimental satellite in 1954 while Van Allen was on sabbatical at Princeton. Abbie invited him to dinner and the two physicists sat in Van Allen’s study afterwards. Van Allen lit his pipe and Stuhlinger laid out the plan. “The only sign of life was the vivid smoke production,” Stuhlinger recalled later in his memoir Wernehr von Braun, Crusader for Space. “All he said was, ‘Thanks for telling me all this. Keep me posted on your progress will you?’” Stuhlinger thought he had failed to spike any interest or confidence but he had only encountered Van Allen’s cautious ability to stand fast and wait for the right moment.
That moment arrived with Stuhlinger’s 1956 phone call and word of the Jupiter C’s success. “The Vanguard program won’t deliver on time,” Stuhlinger predicted, an opinion both scientists heartily shared. Stuhlinger asked Van Allen to develop a hush-hush cosmic ray experiment for the undercover satellite being built for the Jupiter C. This time, Van Allen gambled. His detector design, already selected as a top priority instrument for the Vanguard, could do double duty. With a risky secret agenda, Van Allen and George Ludwig began retooling it so it would fly on either the Vanguard or the Jupiter C.
“Presently, [von Braun’s technicians] have the proven capacity of projecting 18.5 pounds into orbit,” Van Allen noted in his journal. “Might have about two pounds available for us.” In their double lives, Van Allen and Ludwig made formal reports on the progress of the Vanguard instrument at the meetings for the International Geophysical Year and worked on the Jupiter C with the team at the Army Ballistic Missile Agency in Huntsville.
Give us 90 days!
As Sputnik first orbited over the heads of astounded Americans on Oct. 4, incoming Defense Secretary Neil McElroy was touring the Huntsville missile base. His hosts - Von Braun backed by two generals and the Secretary of the Army – immediately confronted him about resurrecting the Jupiter C satellite mission.
“We could have been in orbit a year ago,” von Braun said. “Vanguard will never make it. We have the hardware on the shelf. For God’s sake turn us loose and let us do something. We can put up a satellite in 60 days.” General John Medaris, commander of the missile base, countered with 90 days. And 90 is the deadline Medaris quoted when he announced to his rocket team on Nov. 8 that the Ballistic Missile Agency had been tasked with launching a scientific satellite into orbit with the Jupiter C. “Let’s go Wernher,” he says to the smiling von Braun in a newsreel released months later. But behind the scenes, the Jet Propulsion Laboratory took over von Braun’s dream assignment of building the satellite to fit JPL’s second and third stages for the rocket.
“Von Braun swallowed hard but did not comment,” Stuhlinger reported of the tumult in his memoir. Von Braun knew that JPL had saved the day for the Jupiter C, devising the re-entry testing program and lobbying to give the rocket back in the satellite program. He gave the laboratory a grateful and graceful pass, according to Stuhlinger.
Now all they needed was an official scientific instrument
for their scientific satellite. JPL director William Pickering met with the Huntsville team the next day to hammer out details and announced that the University of Iowa cosmic ray instrument would just happen to fit the Jupiter C, keeping the civilian character of the mission. “You don’t say,” von Braun blandly noted.
But where was Van Allen? Sailing on the fringes of Antarctica by now, he remained remote from the political fireworks and the sudden change of status for the Jupiter C in an all-out push to get an American satellite into orbit.
George Ludwig wasted no time. He packed America’s first space experiment in the trunk of his black and white 1956 Mercury sedan and filled every cranny of the car with other components, a few clothes and kitchen items. “Rosalie and I fitted five-year-old Barbara and four-year-old Sharon into ‘cockpits’ formed among our belongings in the backseat,” Ludwig recalled in his book, Opening Space Research. “Rosalie, now more than six months pregnant, made herself as comfortable as possible for the more than 1,600-mile trip, and we were off.” They headed west across U.S. Highway 6 on Nov. 15, two days after Ludwig’s 30th birthday.
The Eisenhower Administration breathed a sigh of relief when the Russians settled the air space issue that opened the door for reconnaissance satellites as well as scientific ones. Not only was Sputnik flying over the U.S. but the Soviets had trundled it into space in an ICBM, unconcerned about efforts to create a civilian image. But Texas Sen. Lyndon Johnson, a powerhouse for the Democratic Party, sensed the pulse of American outrage and capitalized on it with weeks of hearings. Von Braun appeared to testify just days after the first Vanguard rocket exploded seconds after a launch at Cape Canaveral on Dec. 6, 1957. “Kaputnik,” read one headline about the failed mission. Johnson and von Braun, two consummate opportunists, sized each other up and tossed each other lines that clued in Americans about the lost chance to beat the Russians into space. Now the Jupiter C carried America’s best hopes for vindication.
The War Room wait
Van Allen, von Braun and Pickering had partnered so long for the launch of Explorer I but they didn’t witness it. They gathered in the War Room of the Pentagon with Army Secretary Wilbur M. Brucker and General Lyman Lemnitzer, Army vice chief of staff, on Jan. 31, 1958. There was no television or even a loud speaker to bring them news in this inner sanctum – just a phone. A call from the cape reported a successful launch with the satellite reaching an orbital path and moving eastward around the globe. The group in the War Room bantered in high spirits as they awaited the next call to confirm the satellite was in orbit.
“Boys, this is just like waiting for the precincts to come in,” Brucker wisecracked. But even an election could be fixed - and the satellite was now beyond anyone’s control. A tense mood gripped everyone as time passed.
“It was a really anxious period and silence settled over the whole group. We drank coffee and chewed our nails and wondered what had happened because the expectation was that the satellite would go into orbit and should come around Earth [and reach California] in about 91 minutes, but 91 minutes passed and we got to reception, no reception,” Van Allen recalled.
A series of calls from General Medaris at the cape broke the grim quiet in the War Room but offered no answers. Medaris was hoping Pickering would have some news from JPL. Pickering finally telephoned JPL assistant director Frank Goddard and small-talked. More than 105 minutes passed…106…107 as Goddard listened for word from one of the West Coast telemetry stations or even from a ham radio operator that Explorer I had made it.
"We've got the bird"
The San Gabriel Radio Club gathered in an old brick building on Broadway Street with the antennas on the roof and their radio receivers calibrated. Their headsets picked up the Explorer’s signal first, 108 minutes after liftoff. Seconds later, the signal beamed to a second California station at Earthquake Valley.
“We’ve got the bird,” Goddard shouted.
“Pickering announced the good news and everyone was jubilant and everyone slapped one another on the back. Then, we had to leave for a press conference at the National Academy of Sciences,” Van Allen said. It was now close to 2 a.m. on February 1 and a military chauffeur drove Van Allen, von Braun and Pickering through deserted Washington streets in a steady rain. He unceremoniously dropped them off at the back door of the academy.
“We wondered if anyone would be there,” Van Allen said. “We walked in and there were cameras and reporters – the room was full. And we stood there for two hours answering questions.”
The press needed a good picture for the morning papers and the three men spontaneously picked up a prototype of the tubular Explorer I satellite and hoisted it over their heads in a victory pose. The photo became an instant icon of the space age.
“Jupiter C Puts Up Moon,” applauded the banner headline of the special Satellite Edition of the Huntsville Times.
But Van Allen barely had time to savor the moment and catch a few hours of sleep when lengthy gaps in his detector data suggested that the cosmic ray counter on Explorer I had failed – or he had discovered something in space that no one on Earth knew existed.
Mystery in the gaps
Scientists invented early space instruments from scratch - improvising from other fields as they went along. Van Allen and his graduate students cobbled together cosmic ray detectors with miniaturized
parts meant for watches, hearing aids, nuclear research and the latest rage – transistor radios.
The machine shop in the physics building fabricated other parts non-stop. Harried graduate students rushing in to buy wire or miniscule screws for instruments became a familiar sight at Iowa City hardware stores.
The Geiger tubes needed to count the cosmic rays remained a critical part of the whole system. Van Allen scouted down special Geiger tubes for Explorer I to Anton Electronics, a dingy storefront in Brooklyn, New York that looked like a neighborhood repair shop. “I made Geiger tubes myself when I was in graduate school but nothing of the quality that Anton achieved. It was pretty amazing what came out of this little hole in the wall, grubby place,” Van Allen said.
Looking through the window of the wood-burning stove in his Iowa hometown as a boy, Van Allen could have found a clue to his future in space. “The window was covered with mica. It’s a natural material and can withstand heat, cold, the damp and the dry. It’s really fantastic stuff,” Van Allen noted. Nicholas Anton developed his signature detectors for physicists analyzing nuclear reactions. They were perfect for a trip in a satellite to count cosmic rays because Anton’s proprietary design sealed a sturdy mica window with a fine beading of glass around the rim. The tiniest leak in a Geiger tube renders them useless since they are filled with gas. Cosmic rays enter the tube, ionize a gas molecule and generate an electric pulse. It’s the pulses that were counted by palm-sized discs of miniature electronics “potted” in a pink foam that hardened around them, holding them in place in the cylindrical detector. The instrument reflected a single-minded creation of simplicity, sophistication and mechanical strength. Still, no one had sent such a creation up in a satellite before or tried to record messages from it.
“I’ve got bad news for you. My people tell me your counter stopped working,” Pickering told Van Allen the day after the launch.
“I thought he was wrong because we had all pieces [to show] where it was and wasn’t working,” Van Allen recalled.
Still, he couldn’t explain the anomaly either. The distances between the surface receivers, the unexpected spin of Explorer I as it orbited and the uncertain altitude of the satellite made it hard to recognize any pattern to the static hum.
But even the fragmentary data produced miles of reel-to-reel audiotapes that delivered cosmic rays counts in the form of a staccato symphony of rising and falling tones. Technicians at the receiving stations activated the reel-to-reel machines for each of the 15 minutes tapes, roughly the time the satellite was in transmission range. These original audio tapes from stations around the world arrived at the University of Iowa via regular mail days after they were recorded. Each tape incorporated up to seven tracks of information, including a time stamp, the tones and an occasional voice track where a technician recorded additional information.
The backlog of tapes piled ever higher in the cramped basement beehive where tapes played non-stop on Crown Royal consoles. The playback drove pens on long arms that pulsed and slithered across paper tapes to graph the audio tones. A squadron of students measured the peaks and valleys of the graphs and converted them into numerical counts.
Faculty member Ernst Ray and graduate student Carl McIlwain worked with Van Allen to analyze the tapes. Ludwig returned from JPL and joined the effort, grading the quality of the taped data from A to F in his 120 pages of logs, an A designating noise-free data and an F meaning no readable data. From the first 10 orbits of Explorer I and 34 transmissions of data, Ludwig’s logs give nearly half of them an F. There were no back-up tapes. Nothing like them or the missions that generated them had ever existed before. Even NASA wouldn’t be organized until that fall. Iowa had the original and “the only archive of data tapes from those missions,” Ludwig said.
A satellite with a memory
Van Allen kept searching in the baffling graphs made from the tapes for a transition from the steadily rising counts to the sudden plunge to zero counts. If a transition existed, it was lost in those gaping holes. Van Allen hoped to fill the holes with data from Explorer II.
Ludwig’s invention of a miniaturized, magnetic tape recorder “was to give the satellite its memory,” wrote New York Times reporter Walter Sullivan “It was the size of a small alarm clock, designed so that the [40.5 inch] magnetic tape would jump forward once a second for as long as two hours, winding a spring as its wheels revolved.” A satellite with a memory was just what Van Allen needed. One radio command and the recorder could send more than a full orbit of data to the receiving stations. Only some of the stations could telemeter stored data from the recorder but any one of these stations would access a far more complete data record than all of them together could provide from Explorer I. Van Allen hoped to see how a journey through space could paralyze a Geiger counter and then restore it to normal function.
Ludwig started working on the recorder in 1956. “To initiate playback, a ratchet was released, permitting a spring to rewind the tape onto the supply reel,” Ludwig explains in his book, Opening Space Research. The playback head transmitted the data but also erased it for another round of recording on the same tape. The tape moved in short stops like the hands of a mechanical clock. It recorded 200 seconds of data per inch of tape until the playback command from the ground released the ratchet and spring.
No one had ever tried recording in space before and Ludwig predicted what would happen to standard components. Mylar magnetic tape could stretch at high temperatures, for instance. That had to go. Ludwig found a far more rugged 0.001 thick metal tape electroplated with a nickel-cobalt recording surface. The recorder with its metal tape was ready to be configured for Explorer I but was sacrificed in the frantic effort to place a satellite into orbit as quickly as possible. It flew on Explorer II, but that satellite failed to fire into orbit. Now everything was riding on Explorer III, launched on March 26, 1958.
A near miss threatened to cut off Explorer III instrument operations when Ludwig found faulty wiring during countdown at the Cape.
“My reaction was to heat up the soldering iron and start rewiring the wiring channel,” Ludwig recalled in a University of Iowa documentary on Van Allen. “A number of JPL people relocated to a trailer to find out what they should do about this madman who was rewiring the satellite during countdown.” Once it launched, the detector and recorder worked perfectly.
The music of discovery - Explorer III
In the fall of 1932, 18-year-old James Van Allen lugged a field magnetometer across Henry County, Iowa, near his hometown of Mount Pleasant, the county seat. He took dozens of readings of the intensity and direction of the magnetic field in the towns and open fields, helping out his physics professor Thomas Poulter at Iowa Wesleyan College in Mount Pleasant. The elegant instrument had “brass fittings and ivory knobs and a small telescope for measuring the angle of the sun” at the time he took a reading, Van Allen recalled. His measurements insured that the instrument was properly calibrated for a critical mission – Poulter’s expedition to the Antarctic with Admiral Richard Byrd in 1933. The magnetic field would increase in intensity as the Byrd party approached the South Pole and the scientists could count on measuring the changes precisely thanks to Van Allen’s odyssey in Iowa.
His youthful curiosity about the magnetic field of Earth escalated as his rockoon launches showed how cosmic ray intensities increased with distance from the equator, pooling near the poles where clusters of arching magnetic field lines intersect Earth. Now with the music from Explorer III, Van Allen discovered how Earth's magnetic field reshapes space thousands of miles beyond the atmosphere.
The Naval Research Laboratory in Washington, D.C., worked to optimize data capture for the satellite at their receiving stations and the San Diego station downloaded the first complete global recording of cosmic ray counts made by the detector. Van Allen came to Washington to confer with NRL scientists and learned that the first chants of the Explorer III readings had been transmitted to the D.C. data reduction center that NRL developed for the Vanguard missions.
On Wednesday, April 2, Van Allen took a taxi to the center on Pennsylvania Avenue and picked up the paper tapes graphing the cosmic ray counts. He stopped at a drug store to pick up graph paper and a ruler on his way back to the Dupont Plaza Hotel. He used his slide rule and NRL’s fresh estimates of the orbit altitude to recalculate the peaks and troughs of cosmic rays as a function of the latitude and altitude of the satellite. He could see 15 minutes of cosmic ray levels rising to the maximum his detector could process, then a lengthy drop to zero counts, and then more counts, as though the satellite and space had an on-off switch.
“At 3 a.m., I packed my work sheet and graph and turned in for the night with the conviction that our instruments on both Explorers I and III were working properly but that we were encountering a mysterious physical effect.”
The audio tape data arrived at Iowa while Van Allen was gone. McIlwain, Ray and graduate student Joe Kasper immediately set to work processing data from the reel. “We were looking for a clear transition, the switching point from rising counts to zero,” McIlwain said. “Now there it was. So we knew at once that there was something of very high intensity out there. I immediately took the spare payload and put it in front of an x-ray machine.” The x-ray output showed that massive levels of radiation could choke off the detector.
Van Allen returned to Iowa, welcomed by a sign Ray had left on his chair.
“Space is radioactive.”
Ray’s conscious exaggeration alerted Van Allen to the fact that he and McIlwain had their own confirmation. Van Allen laid out his graphs. McIlwain laid out his x-ray findings. The men looked over the results cautiously at first. But everything pointed to an abrupt boundary in space crossing into a zone where charged particles abruptly rose to unimagined levels. “Then it clicked right away. That was the moment when the light bulb went on – the Eureka Moment,” Van Allen said.
Ludwig returned from “foreign duty” at JPL a few days later, Van Allen noted in his journal. Data analysis from Explorers I and III scaled up to fever pitch. With streams of paper tapes cascading across a table, Van Allen, Ludwig, Ray and McIlwain had ample evidence to hammer out a description of an intense radiation zone encircling Earth – the first discovery of the space race. They were ready to go public with their findings at an upcoming conference of scientists on May 1, 1958 in Washington, D.C.
Radiation belts ring Earth
Van Allen took the podium at a joint meeting of the National Academy of Sciences and the American Physical Society and ushered his audience into a new vision of our world.
“The counting rate was more or less sensible at the start and then blanked as it came along in here and this transition occurred,” Van Allen reported, projecting his graphs. He described the abrupt climb of the satellite across an invisible boundary hundreds of miles above Earth where radiation levels vaulted to 1,000 times the levels just beneath that boundary. Here, Earth’s magnetic field trapped a dense blizzard of charged subatomic particles in a region from about 600 miles to 6,000 miles in space. This band encircled Earth from 35 degrees north to 35 degrees south, a swath that reached roughly from Richmond, Va., to Buenos Aires in Argentina. The trapped particles traversed that distance near light speed, spiraling back and forth within the radiation zone.
The power of magnetic fields was nothing new. Crank a metal wire through a magnetic field and you generate electricity. This is the principal on which all electrical generating plants are based whether the generator arm is powered by coal, oil, hydropower, wind or nuclear energy.
But the idea of Earth’s magnetic field confining an immense zone of radiation that encircled the planet made the maps of the solar system seem obsolete. And Van Allen had only announced one belt. Explorer III readings hinted at an even more massive outer belt beyond the inner one, but not with enough certainty.
After the session, Van Allen went to another room to meet the press and explained the refinements of “geomagnetically trapped corpuscular radiation.” Reporters grasped the central concept of a massive band of radiation girdling the planet with particles capable of piercing metal as though they were silk. Still, they needed a visual hook.
At a science conference in Europe soon after, NRL physicist Robert Jastrow referred to the Van Allen Radiation Belt for the first time and the name stuck. It was the most momentous discovery of the International Geophysical Year. It opened up a new mapping of the solar system, ushering in new fields of science such as magnetospheric physics to explore the magnetic fields of planets and plasma physics, devoted to the solar wind of charged particles radiating outward from the sun.
Now a celebrity scientist,
Van Allen’s physics building basement became ever more crowded by the day. CBS news correspondent Walter Cronkite, Soviet space ambassador Leonid Sedov, military brass and streams of other reporters, politicians and scientists found their way there, amazed at the modest headquarters for some of the most innovative instruments on the frontier of space science. The miniaturized discs of electronics in Iowa’s detectors impressed Russian visitors immeasurably. They hoisted Sputnik into orbit at 184 pounds compared to a total weight of 30.8 pounds for Explorer I with everything in it. It was just the start.
The intrepid explorers Van Allen, Ludwig, McIlwain and Ernst had revealed a momentous discovery in the gaps of their data and found the courage to recognize it. Now they built instruments to study the belts directly. Van Allen and his students later set out to explore the magnetic fields and radiation belts of Venus, Mars and the outer planets.
Explorer IV - Star Wars Mission
Explorer IV had a secret - a dark, spy thriller, Cold War secret that involved an elevator mechanic, atomic bombs and suspicious Russians.
Van Allen with McIlwain and Ludwig, still graduate students, invented instruments to measure the intensity of the radiation belts directly with Explorer IV. No more guessing about what was hiding in the gaps. But the mission provided camouflage for an undercover agenda – whether several nuclear bomb explosions could create a protective shell of artificial radiation belts to disable incoming ballistic weapons. The Reagan administration dusted off and refined the concept with the proposed Star Wars space shield in the 1980s. The 1958 version of an ICBM “Astrodome” was the brainchild of Nicholas Christofilos, a visionary Greek elevator mechanic with degrees in engineering who rose to the highest echelons of Berkeley’s Livermore Laboratory (later the Lawrence Livermore National Laboratory).
The idea of Christofilos’ global space shield filtered through to the Eisenhower Administration and landed at JPL for a proposed test called Project Argus. Pickering suggested Van Allen as the guy with the detectors to survey the blasts and the formation of artificial belts. Van Allen kissed the instruments goodbye as he shipped them off for assembly in the latest Explorer. Explorer IV launched into orbit on July 26, 1958 and the detectors gave immediate substance to the shadowy radiation belts that had paralyzed previous instruments. Prior to the Argus blasts, the mission observed the impact of two 10-megaton missile tests at 48 miles and 27 miles above the Central Pacific. The space blasts grabbed global news coverage. The first one, code-named Teak, unleashed a fireball across 20 miles of sky when it exploded on Aug. 1. Clearly photographed from hundreds of miles away, the blast knocked out radio communications from Australia to British Columbia in an electromagnetic tidal wave. The second blast, code-named Orange, exploded on Aug. 12 and seemed to blot out the sky over the Central Pacific.
The three secret Argus blasts that followed, each from a 1.5 megaton bomb, detonated at 300 miles above Earth and sparked dazzling auroral light shows. The electrons from the blast radiated around the globe and quickly created three thin radiation belts between the inner and outer natural ones. A beehive of students plotted the data tapes from Explorer IV without knowing what they meant. The tapes poured in from around the world and straight into the hands of a slender young woman with bobbed hair, a math degree and a security clearance. She was 22-year-old Annabelle Welsh Hudmon and she managed the beehive.
A glowing recommendation backing her for any job in computational analysis landed at Van Allen’s office even before she did. It came from F. S. Atchison, a physicist and director of the Naval Ordnance Laboratory in Corona, Calif. “I was working [there] on a computer for the Navy pilots to tell them when to fire the Sidewinder rockets,” she says. She married shortly before returning to her home state of Iowa where her husband, Stanton Hudmon, took his medical residency at the University of Iowa Hospitals.
Van Allen hired her on the spot the day before he had to leave town. She moved long tables into position, tested cadres of students to make sure their math skills were sharp and set out to graph an avalanche of data tapes. McIlwain showed her the ropes and she trained the students who came to work for her. They played the data tapes on consoles filling a corridor of the basement. The thin, spidery arms of graphics plotters leaped into action, transcribing the rising and falling tones of the data tapes into rising and falling patterns on paper tapes
that cascaded into neatly folded stacks.
“After we transcribed everything onto paper tapes, we’d plot it from there,” Hudmon says. “We were plotting all those electrons and protons ---we had no idea what we were plotting. I just supplied all the data. I had everything checked twice. Dr. Van Allen never got incorrect data from me.”
McIlwain, Van Allen, Ludwig and Ray huddled over the plots to map the massive reaches of space confined within the belts. The readings from Explorer IV clearly identified the outer radiation belt, the slot between the inner and outer zones, the impact of atmospheric nuclear missile tests and then the Project Argus blasts. Radiation levels from the belts and from the blasts crescendoed into tones on tapes and Hudmon’s team converted it all to the mathematical currency of plotted graphs.
“We ran the tapes five days a week – summers too – we were running them nonstop,” Hudmon recalls. She dropped off her husband at 7 a.m. and headed for the physics buildings. “I was the first one in along with the janitor. I worked until 3:30 or 4.”
She managed 15-20 students at a time. But on one part of the project, Van Allen asked her to work virtually alone and her security clearance came in handy. “He came down and said, ‘I want you to work on this top secret project. I knew it was an atomic bomb explosion and we were measuring the protons and electrons from that explosion. But I was somewhat in the dark. The final report that I gave him was a 100 pages showing different radiation points. I think I worked on it for nearly a year,” she says. “Aside from my children, that was the most important project in my life.”
But the meager belts from the blasts made it clear that maintaining such an artificial shield would require continuous bomb explosions and the plan was abandoned. The rapid declassification of key aspects of the bomb blasts themselves – already reported around the world – allowed Van Allen to discuss the artificial belts that the blasts had created at a science conference in Moscow where he was invited to speak.
He didn’t have to travel all the way to Moscow to find the faces of skeptics. Plenty of scientists in America thought the natural radiation belts were actually the product of atmospheric nuclear testing. The Americans blamed the Russians. The Russians blamed the Americans. Now Van Allen could settle the feud, comparing the robust natural belts to the rather puny ones generated by nuclear blasts.
He kept mum on the details of the audacious space shield experiment. But his stunning documentation of the impact of all five blasts gave added impetus to the need to ban above ground nuclear testing.
The detectors on Explorer IV could only explore particles in the horns of the outer belt as it arched toward the poles. Not even a satellite could navigate a cross-section of this vast radiation zone stretching thousands of miles outward from heights of about 10,000 miles above Earth at the equator. Satellites had eclipsed rockets to reach into space. Now Van Allen needed a new tool to take his detectors higher still. The Pioneer probes built by the Air Force for robotic launches to the moon gave him his wish in the fall of 1958. Pioneers 1 and 3 fell back to Earth from altitudes of about 73,000 miles and 63,000 miles respectively, a far miss from the moon but a win for Van Allen. The missions carried his detectors through the entire swath of the inner and outer radiation belts for the first time. Charged particles spiraling near light speed –particles captured from the solar wind as well as cosmic rays – make up the belts.
The belts arching above Earth created a sense of unchanging permanence and stability – a domed cathedral ceiling of Earth. Then, in August 2012, NASA sent the twin Van Allen Probes to the belts and soon discovered a newcomer – a third belt. Finding a third belt coalescing from the dynamic remnants in the ruins of the outer radiation belt so shocked mission scientists that they, like Van Allen so many years before, wondered if something was wrong with their instruments. Nothing was wrong. The instruments happened to be in place to witness a cataclysm forged by a solar flare. As a legacy to Explorer I, the discovery seemed hard to match. But Iowa scientists did match it with their songs from space, a radio recording of Voyager 1‘s passage into interstellar space after a journey across more than 11 billion miles.
Voyager crossed the boundary just days before the discovery of the third belt.
From Earth to Interstellar Space - Legacy of Explorer I
The chorus of space history - Listen to Explorer I data tapes
The original data tapes from the early Explorers and several other trail-blazing space missions lined floor to ceiling shelves for decades in an abandoned particle accelerator chamber in the basement of the 1910 physics building. But after the severe floods of 2008 and changes in the ventilation system of the building, the tapes began to show the wear and tear of aging, humidity and mildew. The physics department and the University of Iowa Libraries launched a rescue and restore mission to preserve and digitize the 694 tapes from America’s first satellite mission, Explorer I.
“Explorer I is gone, subsequent early satellites that remain in orbit are long silent, the ramshackle tracking stations dotted around the globe that recorded the tones sent from space have either disappeared or been wholly transformed, and Dr. Van Allen’s offices in the basement of MacLean Hall on the University of Iowa campus were dismantled decades ago. Today, the most tangible material remnant of the extraordinary effort behind the United States’ first satellite missions lies in the thousands of magnetic tapes that contain the audio signals captured on Earth at the satellites orbited overhead,” noted Greg Prickman, Head of Special Collections. The Roy J. Carver Charitable Trust in Muscatine, Iowa, where tire magnate Roy J. Carver operated his companies, provided funding for the restoration and digital conversion.
The tapes hold the music of discovery - the original sound tracks and static gaps that revealed the radiation belts. The digital format makes them accessible to you. You can tune into short excerpts, as Explorer crossed receiving stations across the globe, or review the entire odyssey via the "Data & Resources" tab in the main menu. Each tape incorporates several channels of data and even a channel where the voices of technicians at the receiving stations noted times, locations and an occasional comment on harnessing messages from outer space.
By serendipity, the Explorer I restoration program coincided with NASA’s Van Allen Probes satellite mission to the radiation belts and with Voyager 1’s crossing into interstellar space. Both missions hold intrinsic links to Van Allen’s work and to the legacy of the data tapes. Voyager reached interstellar space on Aug. 25, 2012, just days before the Van Allen Probes witnessed the emergence of a third radiation belt in early September, two unbelievable space adventures occurring in quick succession. Everything just lined up - almost like the orbits of the outer planets did as Voyagers 1 and 2 set out in 1977 to tour Jupiter, Saturn, Uranus and Neptune.
Space weather forecasting - Storm shelter for our "cyberelectric cocoon"
Practical-minded kids – and lots of adults - always asked Van Allen to give them a job description for the radiation belts. What do they do? Van Allen liked to say they don’t do anything – they are simply a grand phenomenon of Earth’s magnetic field. But everyone wanted the grand phenomenon to do something. Did they protect us from cosmic rays by trapping and confining them? Did they protect us from the eruptions of solar flares? Van Allen smiled – he had been this route before. No, our magnetic field deflected all but the most energetic cosmic rays and our atmosphere scoured most of the rest into showers of secondary particles. Solar storms generally had little impact at the surface of Earth in the early era of the space age, other than sparking glorious light shows of the aurora above the North and South polar regions. Of course, determining the presence of intense radiation zones
held critical implications for human space flight. NASA mapped mission trajectories at higher latitudes so that astronauts would limit exposure to radiation in the belts as much as possible.
In the field of space physics that Van Allen pioneered, scientists thought of the belts for decades as relatively stable landmarks above Earth. But a changing world proved them wrong. Tumultuous solar weather rocks the belts and strikes havoc for life on Earth in an era of satellite communications. The Van Allen Probes returned to the belts to find out just what was going on. The twin probes – with identical sets of instruments - monitor interruptions to satellite telecommunications, television transmission and GPS systems as intense solar storms pump up the radiation belts in the regions of space where satellites roam.
“Fifty plus years ago we had a relatively modest dependence on assets in space. But as time has gone on we have literally hundreds of thousands of spacecraft [in orbit]. We as a society have built ourselves inside a cyberelectric cocoon – layer after layer of technology and spacecraft operation that move within the Van Allen Radiation Belts now are subject to these immense transient effects from the high energy particles,” says Dan Baker, who lead the way to discovering the new belt with the Relativistic Electron Proton Telescope onboard the probes. A Van Allen protégé, Baker directs the Atmospheric and Space Physics Laboratory at the University of Colorado at Boulder. “The technology can be very severely damaged by these space storms and so [the belts], a curiosity in the earliest part of the space age, are now a necessity to understand.”
Powerful solar flares and even more powerful coronal mass ejections erupt with gales of charged particles that kick up geomagnetic storms in the Earth’s magnetic field just as hurricanes batter coastlines with winds that churn up walls of water. The solar storms can rip apart the outer radiation belt or pump it up to intensities that pound the satellites orbiting there. Geomagnetic storms generate high electrical currents in space, overloading the current in power lines until they trigger blow outs and massive power outages.
With the storms unleashing such destruction, forecasting space weather is now a must, says University of Iowa physicist Craig Kletzing, with an instrument on each probe that measures electromagnetic waves. “The holy grail really is to get to a place like we can with terrestrial weather systems where we predict in advance what’s going to happen. That’s a ways off yet because [space is] such a complex system. The desire of almost everyone is to get to a point where, if we see this happening on the sun then - in a couple of days - this is what’s going to happen” in the belts and on Earth.
The radiation belts pulse, surge and can paralyze satellites much as they saturated Van Allen instruments into static silence. Accurate space weather forecasting would deliver the ability to model satellites of just the right strength – sturdy enough to stand up to solar storms but not weighed down with costly extra armor they don’t need, Kletzing says.
Trying to figure out and forecast the impact in a satellite-dependent world led the scientists to return to the radiation belts in the first place. But none of them expected what they found when they got there shortly after the launch of the probes on Aug. 30, 2012.
The probes reached the belts amid the fireworks of a solar storm unleashed by a coronal mass ejection – a massive eruption of gases from the corona of the sun. Scientists turned on mission instruments immediately, ahead of schedule, just in time to witness the collateral damage of the storm as it obliterated the outer radiation belt. Baker could barely believe the data from his electron and proton detectors - the massive outer belt, stretching thousands of miles across space, torn away. Then his instruments detected a third belt between the inner and outer belts – a “storage ring” of what was left of the outer ring as it began to coalesce once again.
“My first thought actually was - is there something wrong with our instrument,” says Baker, who learned the ropes about radiation belts at Jupiter as one of Van Allen graduate students during the Pioneer 10 mission to the planet in the 1970s.
Kletzing’s team captured other key aspects of this startling view with Iowa’s instruments that measured electromagnetic waves – “a zoo of waves” given off by solar plasma in the storm, he said.
The sun radiates electromagnetic energy, including the visible light that makes possible all life on Earth. But the fusion furnace of the sun also emits streams of plasma that create the solar wind. Plasma - the fourth state of matter – defies the atomic structure of gases, liquids and solids. It is a volatile soup of charged subatomic particles – positive ions and negative electrons - jetting across the solar system. Shock waves rip through the solar wind after coronal explosions and, as the Van Allen Probes witnessed, they can tear away the dynamic outer radiation belt.
“It suddenly got just eaten away but there was a little remnant storing the last little bit of stuff – you might call it a storage ring. And then gradually the outer belt began to fill back in – going from outward inward,” Kletzing said. “It’s very conceivable and even likely that this kind of thing has happened before but we couldn’t detect it.”
Accelerator in the belly of the belts
The Van Allen Probes soon delivered another discovery – clear evidence of the existence of a massive particle accelerator in the belly of the belts. The discovery settles decades of debate about how particles in the belts accelerate to near light speed energies. One model theorized that charged particles hurling toward Earth gain energy as they encounter the ever increasing strength of the planet’s magnetic field and then get trapped in the belts. Imagine a rock rolling down a hill and gaining speed as it accelerates due to gravity, NASA scientists suggest. But particles spiraling up and down within the belts could accelerate right there, boosted as intense electromagnetic waves kick up their energy and speed. Physicist Geoff Reeves, of the Los Alamos National Laboratory, proved that to be the case. He tapped data from the dual locations of varied twin instruments on the probes, including Iowa’s wave instruments, to make 3D measurements of electromagnetic waves that boost the energy of the accelerating particles.
Reeves’ simple, elegant experiment measured the rising energies of particles in the radiation belts. He also measured the distances of the particles from the center of Earth. If the particles were accelerating while on the move toward Earth, their distance from the planet would decrease as their energies increased. If they accelerated within the belts at a fixed distance from Earth, then the belts must be the accelerator. And the distance stood firm!
The frequencies of the waves emitted in the radiation belts during solar storms line up with the build up of particles accelerated to high energies and speeds. Kletzing points to the bursts of red in his data, which tells him there are lots of waves to deliver kicks of acceleration. The accelerator in Earth’s radiation belts gives space weather forecasters a better shot at figuring out just how the energy surges rev up.
Unchartered territory - Voyager 1 explores interstellar space
University of Iowa physicist Don Gurnett keeps an ear on interstellar space. He records radio transmissions from afar – like 12 billion miles afar. He is listening in the vast regions beyond the solar wind with a radio receiver called a plasma wave instrument, listening in a region where cosmic rays hurl across the galaxy from the explosions of giant stars. Gurnett calls up a recent recording - one that captures a first step as momentous as Neil Armstrong’s first step on the moon.
“So I’m going to play now the first recording of sounds that have ever been made from interstellar space,” Gurnett says. “And these sounds are plasma oscillations so they have a very intense sound.” The tones of the sound waves showed that Voyager 1 had crossed the heliopause, the boundary of the solar system’s bubble inflated by the solar wind. The gateway to the vast expanses of space between the stars opens here.
For nearly a year, Voyager scientists debated whether they had crossed into interstellar space, with three instruments offering a mix of solid evidence and deep uncertainty. In May 2012, galactic cosmic ray levels jumped while solar wind particles dipped and the change escalated dramatically that summer. But the counts ebbed and the magnetic field of the sun continued to wrap Voyager. Scientists expected to break through to the interstellar magnetic field - Voyager carried a magnetometer to determine that and it didn’t happen. What now?
The sun lent a hand with a massive coronal ejection in March 2012. The St. Patrick’s Day Solar Storms raged through the solar system, with jets of plasma streaming toward interstellar space and plowing into the interstellar plasma of galactic cosmic rays. When the impact hit, Voyager was there – on location – with Iowa’s plasma wave instrument to make the definitive discovery. Voyager scientists knew that the instrument could pick up the radio signals from plasma oscillations – or vibrations – triggered by the collisions. On April 9, 2013, the instrument tuned into the song of passage – radio waves at frequencies that correspond to interstellar space.
"Normally, interstellar space is like a quiet lake," said Voyager project scientist Ed Stone in a NASA statement. "But when our sun has a burst, it sends a shock wave outward that reaches Voyager about a year later. The wave causes the plasma surrounding the spacecraft to sing."
When you tune in to a radio station at 780 on your AM dial, it means the station is broadcasting at 780 kilohertz, a frequency where the rate of oscillation of the radio waves is 780 cycles per second. The University of Iowa's plasma wave instrument detected and recorded electron plasma oscillations at the very low frequency of 2.6 kilohertz.
“We literally jumped out of our seats when we saw these oscillations in our data – they showed us the spacecraft was in an entirely new region comparable to what was expected in interstellar space,” Gurnett noted when NASA announced the momentous crossing to uncharted territory.
The high-pitched whine of the recording identifies the increased density of interstellar plasma at a point where the density of solar plasma had dropped to nearly nothing. Analyzing the data, Iowa’s plasma wave team of Gurnett and physicist Bill Kurth chronicled the passage back to an exact date: Aug. 25, 2012.
Voyager 1 had journeyed across the solar system for 35 years and more than 11 billion miles to reach that point. The spacecraft launched in 1977 with more than a dozen scientific instruments, two cameras, a nuclear power supply and Carl Sagan’s famous gold record that includes images, natural sounds, a time capsule of music, greetings spoken in 55 languages, printed messages and a cover plate with a map of Earth’s position in the galaxy. The mission completed close encounters to explore Jupiter and Saturn in 1979 and 1980. Voyager 2 followed with flyby approaches to Jupiter, Saturn, Neptune and Uranus between 1979 and 1989. Between them, the twin Voyagers explored 48 of the moons of these outer planets. Thousands of stunning photographs gave people a front row seat to share Voyager’s spellbinding views.
Where is Voyager 1 now? The spacecraft registered what NASA called a “tsunami wave” from another coronal mass ejection. The surge sang through the plasma wave instrument in March 2014 from some 12 billion miles away, confirming the continuing venture through interstellar space.
“All is not quiet around Voyager,” Gurnett noted in NASA’s most recent chapter to the Voyager saga. The radio rhapsody is likely to continue with the solar system caught in the storm currents on an 11-year cycle when the sun reverses polarity. As for Voyager 2, it is still approaching the heliopause.
Built for a 5-year mission, Voyager 1 beat all the odds with less computing power than the average cell phone, project scientists point out. The camera and most of the instruments continue to function. The Iowa wave instrument that tuned into the radio frequency of interstellar space evolved from a home-made radio receiver tested in a field in 1962.
Catching the heavens whistling back
Only the crickets broke the stillness that April of 1962 as University of Iowa electrical engineering senior Don Gurnett headed across his father’s farm in Fairfax, Iowa. He carried a handmade radio receiver with a loop antenna. Gurnett came to the field to detect whistlers, the tones of natural, very low frequency radio waves produced by bursts of lightning.
Safely beyond the power line interference of Iowa City, he sat in the velvet darkness of a clear spring night. He didn’t need a local storm. Whistlers from distant storms – guided by Earth’s magnetic field – dart back and forth between the hemispheres and then funnel to Earth producing a stream of whistling sounds picked up by VLF receivers. With his receiver, Gurnett plugged into the heavens and caught them whistling back.
Radio pioneers discovered whistlers in 1918 and a near mystical following of radio amateurs headed to the countryside to hear the musical tones and static hisses from on high. Gurnett learned about whistlers from a talk given by a NOAA scientist visiting the University of Iowa. Gurnett perfected his own design but carried it dejectedly back to Iowa City after the first night of his vigil in the fields. The receiver hadn’t picked up a thing. So he returned to the farm the next night. Hour after hour, he listened. Then suddenly, he picked up a series of faint whistling tones. Gurnett had big plans for the receiver after that. He just happened to have access to a spacecraft that could capture the radio songs of space.
The first semester of his freshman year, Sputnik launched
and Gurnett decided to help springboard America’s leap into orbit. The tall, lanky boy heard about Van Allen and the basement space lab in the physics building so he walked over and asked for a job. Van Allen could sniff out a kid with a knack for electronics from about a mile away and hired him immediately. Gurnett eventually started working on Van Allen’s homegrown satellite, Injun I, the first university-built satellite to go into orbit. Gurnett, while still an undergraduate, advanced to the position of project engineer for Injuns 2 and 3. Injun 3 resembled two mirror-finished domes fused at the middle, with solar cells lining part of the lightweight magnesium skin.
His very low frequency receiver would fit like a crown on Injun 3 and Gurnett asked permission to add it to the mission. Van Allen agreed but Gurnett suddenly realized that the receiver might blare with feedback from the satellite data transmitter, acting as an amplifier that could cripple the mission. He had to test the system and, once again, he had to get away from the electrical power lines of Iowa City. Not a problem. The space physics team simply loaded up Injun 3 with the VLF receiver and drove it to Fairfax to test it behind the Gurnett family barn. The system worked like a charm.
Injun 3 launched into orbit in December 1962 and the whistlers trapped in Earth’s magnetic field sang loud and clear through the receiver with “all sorts of radio phenomena that frankly had never been heard before,” Gurnett said. Once inside the radiation belts, the receiver picked up a phenomenon called dawn chorus. British radio enthusiasts coined the term to describe a concert of natural radio tones they could pick up that reminded them of the chorus of birds chirping at dawn. But the dawn chorus caught by VLF receivers on Earth couldn’t match the radio show from inside the belts and the chorus swelled dramatically with even mild solar storms. The songs of space gave Gurnett a new tool to explore the radiation belts and to follow the plasma of the solar wind.
Remapping the solar system
Gurnett’s findings helped pioneer the field of plasma physics and remap the distance to the heliopause. Scientists had cautiously extended the boundary of the solar system farther and farther from the sun but estimates remained billions of miles off the mark. Then, the wave instrument caught the radio emissions from a raging solar storm.
“In 1992-93, we detected a very intense radio emission with Voyager, Gurnett says. “For a long time we didn’t know the source. But we finally realized it was produced when a shock wave from a solar flare came out from the sun and reached this outer boundary that we call the heliopause. And we knew roughly the [speed] of the shock wave and that it took over a year - about 400 days – from the time of the explosion for this shock wave to reach the interstellar plasma. So we just did a calculation - distance equals speed times time. And we came up with a number of 116 to 177 astronomical units” to the heliopause.
Voyager, more than 5 billion miles from the sun at the time, sped onward. But Gurnett’s calculations told scientists that the highway to interstellar space covered a staggering 10.8 to 16.5 billion miles from the sun. Miles are “Detroit units,” meant for cars not spacecraft, Van Allen used to say. Distances in space are measured in astronomical units – 1 AU adds up to 93 million miles, the distance from Earth to the sun.
But no one on the mission is saying we’ve left the solar system. Even after crossing the heliopause, the sun’s magnetic field continues to dominate. “We’re in a mixed transitional region of interstellar space,” said Ed Stone, Voyager project scientist and former director of the Jet Propulsion Laboratory that built and operates Voyager. “We don’t know when we’ll reach interstellar space free from the influence of our solar bubble, Stone said in NASA’s announcement of the crossing. “What we can say is Voyager 1 is bathed in matter from other stars.” Amid the star dust, scientists expect more surprises from Voyager before the power supply runs out between 2020 and 2025. After that, the spacecraft heads onward, "Earth's silent ambassador," Stone calls it - like the Pioneers in its legacy.
Pioneers: First ambassadors to the outer planets
Pioneer 10 and Pioneer 11 trail blazed the way. Van Allen’s detectors on Pioneer 10 confirmed the presence of massive radiation belts at Jupiter and found them to be furies of force. His detectors on Pioneer 11 discovered the radiation belts at Saturn. There was plenty of glory to share. Pioneer 10 sent back the first riveting close up images of Jupiter. Other instruments made new discoveries about the planet’s atmosphere, magnetic field and moons. Pioneer 11 tapped momentum from Jupiter’s gravity to slingshot toward Saturn. In addition to the radiation belts, mission scientists discovered a new ring, another small moon and the disheartening realization that Titan is too cold to sustain life. And when Pioneer dipped beneath the rings of Saturn, the images melded scientific observation and transcendent surrealism.
Van Allen followed Pioneer 10 billions of miles past Jupiter, past Saturn, past Uranus, Neptune and Pluto, analyzing new cosmic ray findings with a 1972 Hewlett-Package graphics plotter sitting on his worn wooden desk in the new physics building – Van Allen Hall. Colleagues and friends who followed the faint whiff of pipe smoke into his seventh floor office could see the plotter spitting out charts and graphs from across half the solar system.
Cosmic ray counts dropped as solar explosions blasted shock waves through the solar system, storms powerful enough to push back the incoming streams of cosmic rays. But the cosmic rays jetted forward once the sun calmed down and the counts rose again. Rise and fall. Rise and fall. The cosmic ebb and flow pulsed like a heartbeat until Van Allen could see cosmic ray counts steadily rising despite solar storms by the time Pioneer 10 called home for the last time from a distance of 8 billion miles away in 2003.
The swifter Voyagers had passed Pioneer 10 by then but Van Allen’s readings told him Voyager 1 must be closing in on a critical intermediate boundary of the solar system - just in time for the Iowa space family to return home to celebrate his 90th birthday.
Space family reunion
On a warm October weekend in 2004, the pantheon of Van Allen’s space family returned to Iowa City for the birthday bash of the father of space science. Former students returned, now luminaries in a field they had helped develop across the globe. Gurnett’s administrative assistant Kathy Kurth and several others organized three days of festivities that kicked off with a cocktail party. Electronics technicians Lowell Swartz and Michael Nowack came from nearly towns and introduced themselves by their old nicknames Ugh 1 and Ugh 2. Their motto was the impossible just took a bit longer. “We’d go ugh and tackle the job,” Nowack said. Instrument maker Ed Freund reminisced about improvising parts and hunting down lightweight metals for Ludwig’s latest tape recorder design. Van Allen’s feisty former secretary Agnes McLaughlin, who even warded off federal agents on one busy day, reminded eminent scientists of their student pranks as thought they were 18 again. Ludwig opened the colloquium the next day with the adventures of Explorer I, retelling a favorite story to an audience who would never tire of discovering new details. Stone, an Iowa native son, recounted the odyssey of Voyagerduring a packed public lecture.
But underlying all the festivities simmered a fierce debate over whether Voyager 1 had crossed the inner boundary of the solar system – the termination shock. Here, the force of the solar wind began to subside and pool with cosmic gases. Had they crossed? Were the pitching waves of the termination shock rocking Voyager like a tiny raft caught in an ocean storm? Magnetic field readings on Voyager confirmed the inner crossing a few months later as Van Allen had predicted with the final messages from Pioneer 10.
“It was one of Jim Van Allen’s top goals to reach the heliopause but Pioneer 10 just ran out of electrical power before we could get there,” says Gurnett, reflecting back on his friend, mentor and teacher. “He would have been thrilled to know we actually reached it.”
Van Allen applauded the victory of reaching the outpost of the termination shock and avidly followed the Voyagers among the litany of on-going missions with University of Iowa instruments. But after a series of unexpected complications following surgery, Van Allen passed away on Aug. 9, 2006 just weeks before his 92nd birthday. He worked until the day before his surgery and finished final edits for two journal articles while in the hospital.
His father had girt, his youngest son Peter Van Allen said at a packed memorial service in Hancher Auditorium on the University of Iowa campus. “And that really meant, if there was any kind of inspiration, it came after many long hours and, if there was genius, it was the result of many hours of toil applied to the same problem.”
Fusion - The ultimate legacy
The discovery of the radiation belts extended our sense of Earth’s environment thousands of miles beyond the atmosphere into the vast regions of the magnetic field – the magnetosphere. Without it, cosmic rays and the plasma from the sun could rip away the protective ozone layer that makes life on Earth possible. But the magnetosphere, like the belts within it, still holds vast mysteries for future explorers and both could reveal clues to unleash the power of controlled fusion reactors.
The dawn chorus generated in the radiation belts sings one of those mysteries in the radio waves transmitted by the motions of particles as jet streams of electrons spiral up and down within the belts. Chorus waves deliver those kicks of acceleration to particles replenishing the belts. But the waves can stretch the tight spiral orbit of the electrons and spring them into the upper atmosphere, an escape route in nature that mimics the daunting struggle to confine plasma for controlled fusion on Earth.
“At the time we heard these recordings from Injun 3, we didn’t completely realize the significance. It was later shown that these waves that are generated in the radiation belt, they change the pitch angle” of particles, Gurnett says. “It’s one of the main mechanisms by which particles are lost in the radiation belts so it’s a very important physics problem.” It’s also the biggest problem for controlled fusion reactors but almost impossible to track the causes at temperature levels hot enough to melt any probe. So we can study these processes with spacecraft and there’ve been great advances in our understanding of the instabilities that lead to the dawn chorus.”
Simply put, If we can understand how particle are siphoned off from the radiation belts we would have a better understanding of how to confine them in a controlled fusion reaction.
The fire in the heart of the sun creates the temperatures and pressure necessary for fusion – the source of all the energy that radiates from the sun. Fusion uses hydrogen – the most abundant material in the universe as fuel. Hydrogen normally has one electron and one proton. But the hydrogen that fuels the sun’s fusion furnace has two other forms - deuterium (with a proton and a neutron) and tritium (with a proton and two neutrons). The sun fuses one of each, creating a helium atom with two neutrons and two protons. The process spins off the extra neutron to create more tritium and Einstein’s famous equation E=mc2 (energy equals mass times the speed of light squared) tells us the rest of the story. Even with the release of the stray neutron, the new helium nucleus has less mass than its other components – just a little less mass that converts to massive amounts of energy.
Earth’s surface collects about a millionth of the energy released at the surface of the sun. But that amounts to some 120 billion kilowatt-hours of energy per square mile of Earth each year, enough to meet current electrical needs of our planet with about 1,200 square miles if all of the energy could be collected, distributed and stored - big ifs with today’s technology. Controlled fusion continues to defy technology as well.
Scientists have worked for nearly 70 years to magnetically confine plasma at temperatures and pressures to generate energy in a fusion reactor. The best they can do so far is break even. Mimicking the stars for an unlimited source of clean energy continues at the huge fusion laboratories such as the National Ignition Facility and ITER.
Baker, too, looks to the alternative on-location laboratory of space to tackle the fusion puzzle. “What’s magnificent about space physics – the field that was invented by Professor Van Allen - is that we can really go there” and make direct measurements. Now he plans to tap a laboratory in Earth’s magnetic field via a space mission he’s plannws with Kletzing and scientists from across the county. The four spacecraft observatories of the Magnetospheric Multiscale mission, launched into orbit on March 12, are tapping into fundamental forces of Earth’s magnetic field and the turbulence that rocks them during solar storms.
The crossing, disconnection and reconnection of magnetic field lines in solar storm converts vast amounts of magnetic energy into bursts of kinetic and electric energy as solar storms of plasma collide with Earth’s magnetic field. The same processes in laboratories on Earth may be another fundamental process disrupting efforts to achieve controlled fusion with magnetic containment of plasma. That’s one mystery the Magnetospheric Multiscale mission would like to solve, Baker says.
Clues to achieving controlled fusion that could be gleaned from the radiation belts and the magnetosphere may hold Van Allen’s future legacy.
Still, the legacy closest to his heart was the legacy of his students - of hands working with him to build the instrument that became the eyes and ears taking space explorers to places where human beings cannot travel as yet.
“The University of Iowa is one the few universities, particularly these days, that still builds space flight hardware and makes measurements. And that’s a tradition we’ve had here for a long time and we’re keeping it going and plan to keep it going,” Kletzing says. “We’re pretty committed to staying involved in building hardware that flies on missions. Part of the history here is that the best science gets done by the people who actually build the instruments and understand how they work and somebody has to train the next generation of people. Many of Van Allen’s students went off to build hardware elsewhere. The real legacy of any educational institution is preparing the next generation to find the next set of discoveries. Van Allen flew on Explorer I because he had an instruments he’d been flying on rockets and it was ready in sufficient time to get it onto a satellite after Sputnik sort of shocked people and we said, ‘Oops we better catch up.’” | 0.887122 | 3.113911 |
Greetings! My name is Elizabeth Bailey, and I am a graduate student here at Caltech. As part of my work so far, I have addressed the ongoing search for Planet Nine, in particular the use of mean-motion resonances to infer its present-day location on the sky.
A mean-motion resonance occurs when two bodies orbiting a central body have orbital periods related by an integer ratio. A great example is Pluto and Neptune. Pluto’s orbit is not a perfect circle, but rather a little elongated (e ~ 0.25). It actually crosses Neptune’s orbit, which might lead one to ask if they are on a collision course with each other. Fortunately, the answer is a confident “no.” Neptune and Pluto will never collide, because they are in a 3:2 (pronounced “three-to-two”) mean motion resonance with each other. Meaning, for every three trips Neptune completes around the sun, Pluto completes exactly two. It’s as if they’re dancing with each other. Every three times Neptune steps into the intersection of their orbits, Pluto steps twice somewhere else, and they don’t step on each other.
So what does this have to do with Planet Nine? If Planet Nine exists, the distant KBOs it shepherds may very well experience resonant interactions with it. In fact, this was already pointed out in Konstantin & Mike's original Planet Nine paper, and is at this point relatively well understood. As a result, we can reasonably expect that at least some of the observed KBOs are currently locked into resonances with Planet Nine, and if we can understand the machinery of these interactions, perhaps we can infer the location of P9.
In a sense, the distant solar system is a lot like a giant cosmic nightclub. In this analogy, we are scanning the dance floor for Planet Nine, but it's hanging out in a dark corner somewhere in the back, while everyone is doing a P9-themed dance. So rather than looking for P9 itself, we are instead trying to figure out where it is by studying the KBO mosh-pit. This brings us to the key problem at hand: is this feasible in practice? We address this question in our recent work, published in the Astronomical Journal.
The short answer is no - using resonances does not appear to be a feasible approach to find Planet Nine. Here's a figure from the paper comprised of seven histograms, corresponding to simulations with seven different eccentricities of Planet Nine (e_9 = 0.1, ..., 0.7) showing the count of objects occupying individual resonances. (The 2:1 resonance is located at "2" on the horizontal axis, and the 3:2 resonance is located at "1.5," and so forth.)
The takeaway point from this figure is that although you do find a lot of KBOs at the big-name resonances like 3:2 or 1:1, there are many objects occupying other resonances with larger integers in their names, like 14:5 or 2:7. There is a disturbing consequence of the mathematical nature of the planetary disturbing function (yes, it is actually called "The Disturbing Function" in celestial mechanics literature) which, upsettingly, suggests that these so-called high-order resonances become increasingly important when dealing with eccentric planets like Planet Nine, and the results of computer simulations presented in this work confirm this. In summary, because Planet Nine is eccentric, it carries out very complicated dance moves with the KBOs.
It's worth mentioning that the simulations used to make this figure were simplified in comparison to reality. The canonical giant planets Jupiter through Neptune were treated as a static ring of mass (this is often referred to as the “secular” approximation), and the solar system is treated as a flat 2-dimensional object even though Planet Nine is, in reality, inclined. Think of it as a best-case scenario of sorts: in this physical setup, Planet Nine is the only active perturber of the KBOs. In the real solar system, Neptune is also on the dance floor, behaving in a very disruptive fashion. When KBOs get too close to Neptune, it flings them around. Sometimes those KBOs resume dancing with Planet Nine, but other times they just head out the door into interstellar space.
Suppose, despite these complications, you could determine which individual KBOs are indeed in mean motion resonances with Planet Nine at this time. Then, if this information were to be of any use, you would then need to know the specific resonance of each KBO. In 3-D simulations, there is no obvious concentration of objects at particular resonances (see figure below). Hence, no matter how long we wait for more KBOs to be observed, we have virtually no hope of using resonances to predict Planet Nine's current location along its orbit.
Although based on the results of this work it does not appear feasible to predict the present-day location of Planet Nine along its orbit, this does not by any means imply that Planet Nine is invisible to telescopes. There is still a well-defined swath of sky in which the search for Planet Nine continues. We have merely shown that mean-motion resonances with KBOs are not a useful tool for deciding where point the telescope, so we're back to systematically scanning the sky. Turns out that even in astronomy, the easy way is the hard way. | 0.914286 | 3.861621 |
Published on April 18th, 2011 | by Yellow Magpie1
Henrietta Swan Leavitt: She Changed The World But Paid The Price
While Edwin Hubble may have garnered all the plaudits for discovering other galaxies, the true genius that did all the work is often forgotten. Punished because of her sex, Henrietta Swan Leavitt’s work has changed the nature of astronomy forever.
Science, like virtually every aspect of humanity, is bound by our mindset. Sometimes we can be confined by convention and concepts that we take for granted. The greatest thinkers have questioned the status quo and have revealed our world to be much different than we imagine. Henrietta Swan Leavitt was one such person.
The Problem Of Measuring Distance
Scientists were faced with a very difficult problem when it came to measuring distance and time in the Universe. One of the earlier methods of calculating distance, was through parallax. This basically used two perspectives to measure objects. So for example, a star’s position was noted in both summer and winter. The angle between the two positions allowed astronomers to measure distances between stars in Space.
However, measuring distance using parallax had a significant drawback. The further away the objects were, the smaller the difference in perspectives. Certain objects could not be measured as they were too far away.
A Universe With Only One Galaxy
Prior to Leavitt many scientists maintained that the Milky Way was the only galaxy in the Universe. Although there were those that thought otherwise, neither side could conclusively prove their argument one way or another as it was possible to use evidence to support both sides.
This debate would not be solved until the 1920’s when an unsung woman would change the nature of the world for ever.
The Genius Of Leavitt
Henrietta Swan Leavitt changed all this as she helped to conclusively prove that there were a myriad of galaxies in the Universe. She worked as a so-called ‘computer’ counting images of stars on plate photographs taken from telescopes throughout the world.
With painstaking effort and detail Leavitt marked out the subtle details of the stars and recorded them. During the course of this work, she would come up with a remarkable idea that centred on objectively finding the true brightness of the stars.
The Cepheid Variable
One particular star that caught her attention is called a Cepheid variable. Cepheid variables are pulsing stars that populate the Universe. The genius of Leavitt was that she recognised that there was a distinct correlation between their luminosity and the rate at which they pulsed. To simplify, there was a relationship to the number of times they blinked and their brightness.
Once Leavitt knew this she could find Cepheid variables that pulsed at the same rate. These stars, even if one shun brighter than the other would burn at the same luminosity. The only difference was that the dimmer star was farther away. Using this Leavitt could calculate the distance between the brighter and dimmer stars. Leavitt had discovered a way of measuring stars that lay well beyond the limitations of parallax and the standard candle, which is used to measure the vast distances of Space, was born.
But Leavitt was a second class citizen. She, like countless others, was forbidden from using a telescope. Why? Because she was a woman and women were believed to be intellectually inferior to men. And so in this sexist environment she couldn’t progress her work.
Instead her work was taken up by the visionary and highly egotistical Edwin Hubble. Hubble, using the latest in telescopic technology, used Leavitt’s work to find a Cepheid that was outside of the Milky Way Galaxy.
The variable was located in our nearest neighbouring galaxy, in what would become known as Andromeda. The Andromeda galaxy is over 2.5 million light years away. Or if you look at it another way – what we see in the sky as Andromeda is what the galaxy looked like over two million years ago. When we look up at Andromeda in the night sky we are actually receiving the light that started off on its 2.5 million year journey before the existence of the modern human.
Through Leavitt, Hubble had shattered the belief that the Milky Way was an island galaxy, the only galaxy in the Universe. One can only speculate what Leavitt would have achieved in a non-sexist world but stuck in the early 20th century, it was clear that being a woman prevented her from realising her potential.
As it stands, despite all of this, Leavitt managed to change the world, she may not have received the Nobel Prize for Physics but thanks to her we now have a better understanding of the Universe, and the world that we inhabit.
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For France: Notable Women and Broken Ceilings. | 0.843937 | 3.411365 |
At best, the few extrasolar planets we have imaged directly are just points of light. But what can that light tell us about the planet? Maybe more than we thought. As you probably know the, Deep Impact spacecraft flew by comet Hartley 2 today, taking images from only 700 km away. But maneuvering to meet up with the comet is not the only job this spacecraft has been doing. The EPOXI mission also looked for ways to characterize extrasolar planets and the team made a discovery that should help identify distinctive information about extrasolar planets. How did they do it? By using the Deep Impact spacecraft to look at the planets in our very own solar system.
The spacecraft imaged the planetary bodies in our solar system — in particular the Earth, Mars and our Moon — (see here for movies of the Moon transiting Earth) and astronomer Lucy McFadden and UCLA graduate Carolyn Crow compared the reflected red, blue, and green light and grouped the planets according to the similarities they saw. The planets fall into very distinct regions on this plot, where the vertical direction indicates the relative amount of blue light, and the horizontal direction the relative amount of red light.
This suggests that when we do have the technology to gather light from individual exoplanets, astronomers could use color information to identify Earth-like worlds. “Eventually, as telescopes get bigger, there will be the light-gathering power to look at the colors of planets around other stars,” McFadden says. “Their colors will tell us which ones to study in more detail.”
On the plot, the planets cluster into groups based on similarities in the wavelengths of sunlight that their surfaces and atmospheres reflect. The gas giants Jupiter and Saturn huddle in one corner, Uranus and Neptune in a different one. The rocky inner planets Mars, Venus, and Mercury cluster off in their own corner of “color space.”
But Earth really stands out, and its uniqueness comes from two factors. One is the scattering of blue light by the atmosphere, called Rayleigh scattering, after the English scientist who discovered it. The second reason Earth stands out in color is because it does not absorb a lot of infrared light. That’s because our atmosphere is low in infrared-absorbing gases like methane and ammonia, compared to the gas giant planets Jupiter and Saturn.
“It is Earth’s atmosphere that dominates the colors of Earth,” Crow says. “It’s the scattering of light in the ultraviolet and the absence of absorption in the infrared.”
So, this filtering approach could provide a preliminary look at exoplanet surfaces and atmospheres, giving us an inkling of whether the planet is rocky or a gas planet, or what kind of atmosphere it has.
EPOXI is a combination of the names for the two extended mission components for the Deep Impact spacecraft: the first part of the acronym comes from EPOCh, (Extrasolar Planet Observations and Characterization) and the flyby of comet Hartley 2 is called the Deep Impact eXtended Investigation (DIXI). | 0.877835 | 3.993733 |
As I mentioned in my article on determining galactic distances, VLBI radio astronomy parallax measurements are finally producing accurate distance estimates for important locations around the Milky Way, replacing the dodgy and unreliable kinematic and photometric estimates used in the past.
Last week, an international team uploaded a paper presented at the 10th European VLBI Network Symposium to the astrophysics archive, giving an estimate for the distance to W75N, an important region within the Cygnus X complex, which is believed to be the closest major complex of star formation regions to our solar system. The estimate is 1320 (+110/-90) parsecs, making it slightly closer than the 1500 parsecs I've been using for the Milky Way map on this site.
The same team intends to publish estimates for other objects within Cygnus X, which should finally determine whether Cygnus X is a real complex of massive star formation regions or simply many different star formation regions scattered at different distances in the line of sight. Recent research suggests that Cygnus X is real, but only parallax measurements will make this certain. | 0.862707 | 3.012759 |
Eclipsing binary star systems are relatively common in our Universe. To the casual observer, these systems look like a single star, but are actually composed of two stars orbiting closely together. The study of these systems offers astronomers an opportunity to directly measure the fundamental properties (i.e. the masses and radii) of these systems respective stellar components.
Recently, a team of Brazilian astronomers observed a rare sight in the Milky Way – an eclipsing binary composed of a white dwarf and a low-mass brown dwarf. Even more unusual was the fact that the white dwarf’s life cycle appeared to have been prematurely cut short by its brown dwarf companion, which caused its early death by slowly siphoning off material and “starving” it to death.
The study which detailed their findings, titled “HS 2231+2441: an HW Vir system composed by a low-mass white dwarf and a brown dwarf“, was recently published the Monthly Notices of the Royal Astronomical Society. The team was led by Leonardo Andrade de Almeida, a postdoctoral fellow from the University of São Paolo’s Institute of Astronomy, Geophysics, and Atmospheric Sciences (IAG-USP), along with members from the National Institute for Space Research (MCTIC), and the State University of Feira de Santana.
For the sake of their study, the team conducted observations of a binary star system between 2005 and 2013 using the Pico dos Dias Observatory in Brazil. This data was then combined with information from the William Herschel Telescope, which is located in the Observatorio del Roque de los Muchachos on the island of La Palma. This system, known as of HS 2231+2441, consists of a white dwarf star and a brown dwarf companion.
White dwarfs, which are the final stage of intermediate or low-mass stars, are essentially what is left after a star has exhausted its hydrogen and helium fuel and blown off its outer layers. A brown dwarf, on the other hand, is a substellar object that has a mass which places it between that of a star and a planet. Finding a binary system consisting of both objects together in the same system is something astronomers don’t see everyday.
As Leonardo Andrade de Almeida explained in a FAPESP press release, “This type of low-mass binary is relatively rare. Only a few dozen have been observed to date.”
This particular binary pair consists of a white dwarf that is between twenty to thirty percent the Sun’s mass – 28,500 K (28,227 °C; 50,840 °F) – while the brown dwarf is roughly 34-36 times that of Jupiter. This makes HS 2231+2441 the least massive eclipsing binary system studied to date.
In the past, the primary (the white dwarf) was a normal star that evolved faster than its companion since it was more massive. Once it exhausted its hydrogen fuel, its formed a helium-burning core. At this point, the star was on its way to becoming a red giant, which is what happens when Sun-like stars exit their main sequence phase. This would have been characterized by a massive expansion, with its diameter exceeding 150 million km (93.2 million mi).
At this point, Almeida and his colleagues concluded that it began interacting gravitationally with its secondary (the brown dwarf). Meanwhile, the brown dwarf began to be attracted and engulfed by the primary’s atmosphere (i.e. its envelop), which caused it it lose orbital angular momentum. Eventually, the powerful force of attraction exceeded the gravitational force keeping the envelop anchored to its star.
Once this happened, the primary star’s outer layers began to be stripped away, exposing its helium core and sending massive amounts of matter to the brown dwarf. Because of this loss of mass, the remnant effectively died, becoming a white dwarf. The brown dwarf then began orbiting its white dwarf primary with a short orbital period of just three hours. As Almeida explained:
“This transfer of mass from the more massive star, the primary object, to its companion, which is the secondary object, was extremely violent and unstable, and it lasted a short time… The secondary object, which is now a brown dwarf, must also have acquired some matter when it shared its envelope with the primary object, but not enough to become a new star.”
This situation is similar to what astronomers noticed this past summer while studying the binary star system known as WD 1202-024. Here too, a brown dwarf companion was discovered orbiting a white dwarf primary. What’s more, the team responsible for the discovery indicated that the brown dwarf was likely pulled closer to the white dwarf once it entered its Red Giant Branch (RGB) phase.
At this point, the brown dwarf stripped the primary of its atmosphere, exposing the white dwarf remnant core. Similarly, the interaction of the primary with a brown dwarf companion caused premature stellar death. The fact that two such discoveries have happened within a short period of time is quite fortuitous. Considering the age of the Universe (which is roughly 13.8 billion years old), dead objects can only be formed in binary systems.
In the Milky Way alone, about 50% of low-mass stars exist as part of a binary system while high mass stars exist almost exclusively in binary pairs. In these cases, roughly three-quarters will interact in some way with a companion – exchanging mass, accelerating their rotations, and eventually en merging.
As Almeida indicated, the study of this binary system and those like it could seriously help astronomers understand how hot, compact objects like white dwarfs are formed. “Binary systems offer a direct way of measuring the main parameter of a star, which is its mass,” he said. “That’s why binary systems are crucial to our understanding of the life cycle of stars.”
It has only been in recent years that low-mass white dwarf stars were discovered. Finding binary systems where they coexist with brown dwarfs – essentially, failed stars – is another rarity. But with every new discovery, the opportunities to study the range of possibilities in our Universe increases. | 0.86475 | 3.921762 |
brace urself guys tis gonna be a long post...
just suddenly wondered.
like richard said, if we were to take one metre cube of space...it would most probably be transparent isnt it? since there is nothing in space but maybe hydrogen particles and "dark matter".
is the dark matter the one that makes space "look" black?
or issit because the edge of the universe is black? and cos theres virtually nothing in space to hinder our view, we are able to see the edge of the universe?
or issit cos theres so many black holes out there that it makes space black, tho this is more insane.
i remember someone saying that our galaxy may be rotating around a blackhole just like one of the planets in the solar system...except that this solar system has much more "planets".
since black holes suck in particles and matter, issit possible that this "solar system", which includes our galaxy, are being sucked into the black hole without us knowing? why would we not know that? my conclusion would be because everything around us are slowly rotating into the black hole, just like our galaxy, and therefore we would not know that.
i know this conclusion is quite mad, cos if we are indeed getting sucked into a "central" blackhole, why isnt our gravity getting affected(our gravity refers to our solar system's gravity in general)?
i understand that before that might happen, our sun will explode(how do you use supernova here?), and devour the whole of our solar system, but since there are so many solar systems out there, and each and everyone of them may explode also, as they explode they throw out matter against the "central" blackhole's gravity, which gives the hole more stuff to suck in.
however, if we were to look in spacetime curvature...the black hole is actually pulling the carpet on which all matter rest on...which means it doesnt matter whether a star explodes or not...it simply "eats" up the carpet.
at the same time however, as math shows, our universe is constantly expanding, this might mean either our universe will NEVER be sucked into a blackhole, or it WILL in some time.
OK QUESTIONS TIME!!
1. Why is our space black?
2. are we being sucked into a "central" blackhole unknowingly?
3. how do you use supernova in a sentence?
and please...correct my mistakes above if i have any.
i dont mind if u have a long post, i will still read it and reply to it... | 0.840311 | 3.148724 |
NASA’s MAVEN probe shows how wind circulates in Mars’ upper atmosphere
By using the MAVEN spacecraft to track winds in the Martian thermosphere, researchers hope to better understand how the atmosphere leaks into space.
High above the surface of Mars, winds circulate from dayside to night, and the air undulates as it passes over mountains and valleys far below, a new study shows.
These insights come courtesy of NASA’s MAVEN spacecraft, which now has provided the first detailed maps of winds in the Martian thermosphere, one of the highest layers of the planet’s atmosphere. The data, described in the Dec. 13 Science, could help researchers better understand how the Red Planet’s climate has changed over time by looking into how Mars’ atmosphere bleeds into space.
“Looking at how gas circulates in that layer allows us to better understand the rate at which the atmosphere is being lost and the way it’s being lost,” says study author Mehdi Benna, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md.
Wind movement in Mars’ thermosphere is much simpler than on Earth, data from the orbiter show. A single circulating flow persists from season to season, continually moving air from the planet’s dayside to its nightside, whereas on Earth there are multiple flow patterns at any one time. “Oceans on Earth complicate the circulation patterns,” Benna says. “Mars doesn’t have all that.”
The spacecraft, which arrived at Mars in 2014, also recorded waves in the thermosphere generated by winds near the ground diverting around mountains and canyons (SN: 9/22/14). “When the spacecraft is flying over a mountain, we can see the wind shifting to accommodate the presence of that mountain 200 kilometers below,” Benna says. “MAVEN doesn’t carry [traditional] cameras … but we can see a picture of the topography in the winds.”
In all, the researchers tracked winds for one and a half Martian years. While it’s still too early to say precisely what this all means for the trickle of Mars’ atmosphere into space, Benna says that these maps lay the foundation for improved computer simulations that will help researchers figure it out. | 0.801863 | 3.788753 |
Is Earth the only habitable planet in the universe or are there more worlds somewhere out there that are capable of supporting life? And if there are, what might they look like? In a bid to answer these fundamental questions, scientists are searching space for exoplanets: distant worlds that orbit other stars outside our solar system.
More than 4,000 exoplanets are known to date, most of them orbiting single stars like our Sun. Now astrophysicist Dr Markus Mugrauer of Friedrich Schiller University Jena, Germany, has discovered and characterised many new multiple star systems that contain exoplanets. The findings confirm assumptions that the existence of several stars influences the process by which planets are formed and develop. The study by Mugrauer, of the Astrophysical Institute and University Observatory of the University of Jena, has now been published in the renowned specialist journal Monthly Notices of the Royal Astronomical Society.
Space telescope provides precise data
"Multiple star systems are very common in our Milky Way," explains Mugrauer. "If such systems include planets, they are of particular interest to Astrophysics, because the planetary systems in them can differ from our solar system in fundamental ways." To find out more about these differences, Mugrauer searched more than 1,300 exoplanet host stars with exoplanets orbiting them to see whether they have companion stars. To this end, he accessed the precise observation data of the Gaia space telescope, which is operated by the European Space Agency (ESA).
In this way, he succeeded in demonstrating the existence of around 200 companion stars to planetary host stars that are up to 1,600 light years away from the Sun. With the help of the data, Mugrauer was also able to characterise the companion stars and their systems in more detail. He found that there are both tight systems with distances of only 20 astronomical units (au) - which in our solar system corresponds approximately to the distance between the Sun and Uranus - as well as systems with stars that are over 9,000 au from each other.
Red and white dwarfs
The companion stars also vary as to their mass, temperature and stage of evolution. The heaviest among them weigh 1.4 times more than our Sun, while the lightest have only 8 per cent of the Sun's mass. Most of the companion stars are low-mass, cool dwarf stars that glow faintly red. However, eight white dwarfs were also identified among the faint stellar companions. A white dwarf is the burnt-out core of a sun-like star, which is only about as big as our Earth, but half as heavy as our Sun. These observations show that exoplanets can indeed survive the final evolutionary stage of a nearby sun-like star.
Double, triple and quadruple star systems with exoplanets
The majority of the star systems with exoplanets identified in the study have two stars. However, some two dozen hierarchical triple star systems and even a quadruple star system were detected. In the range of distances investigated, of between approximately 20 and 10,000 astronomical units, a total of 15 per cent of the stars studied have at least one companion star. This is only about half the frequency expected in general for solar-like stars. In addition, the companion stars detected show distances about five times greater than in ordinary systems.
"These two factors taken together could indicate that the influence of several stars in a star system disrupts the process of planet formation as well as the further development of their orbits," says Mugrauer. The cause of this could be first the gravitational impact of a stellar companion on the gas and dust disc in which planets form around their host star. Later, the gravitation of the stellar companion influences the motion of the planets around their host star.
Markus Mugrauer would like to pursue the project further. In the future, too, the multiplicity of newly discovered planetary host stars would be studied using data from the Gaia mission and any companion stars detected would be precisely characterised. "In addition, we will combine the results with those of an international observational campaign, which we are currently conducting on the same topic at the Paranal Observatory of the European Southern Observatory in Chile," added Mugrauer. "We will then be able to investigate the precise influence of stellar multiplicity on the formation and development of planets."
Dr Markus Mugrauer
Astrophysical Institute and University Observatory
Friedrich Schiller University, Jena
Schillergässchen 2, 07745 Jena
Tel.: +49 (0)3641 947514 | 0.908055 | 3.9241 |
Don't be alarmed, but the Fireworks galaxy is exploding.
To be fair, it's been exploding for a while — at least since 1917 (give or take the 25 million years that light takes to travel from that galaxy to Earth), when astronomers first glimpsed a large star erupting into a supernova there. Since then, scientists have detected nearly a dozen stellar explosions in the busy galaxy, but none quite like the mysterious green blotch of X-ray light visible in the image above.
What makes that blotch special? For starters, it's not a supernova. The X-ray signature detected by NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) observatory is far more energetic than that of a typical supernova. (You can see one of those explosions glowing blue in the upper right corner of the same image.) But more importantly, the energetic X-ray blast also appeared and disappeared from the galaxy in about 10 days — a much briefer appearance than a supernova, which can brighten and fade over hundreds of days.
So, the greenish blast of invisible energy is probably not a supernova. What is it, then? A study published Aug. 9 in The Astrophysical Journal provides a few guesses. The study authors, who glimpsed the mysterious blast of energy by chance while studying supernovas in the Fireworks galaxy, said the mystery explosion likely involves one of the most powerful objects in the universe, possibly a black hole or neutron star, tearing apart one of its stellar neighbors.
While black holes are, uh, black, their outer edges glow with intense radiation when nearby objects get pulled into the black hole's orbit. It's possible, according to a statement accompanying the study, that the source of the green blast is a black hole that devoured a nearby star. As the hole's overwhelming gravity rips that star to shreds, stellar debris could start spinning around the black hole. Debris closest to the hole's event horizon (see: point of no return) could orbit so quickly that it gets hundreds of times hotter than Earth's sun, radiating X-rays as it gets sucked into oblivion.
A neutron star, the ultradense corpse of a once-mighty star, could also be the culprit here. Packing roughly the same mass as our sun into a ball the size of a city, neutron stars exert a gravitational pull billions of times stronger than Earth’s. However, these stellar corpses spin so blazingly fast that it can be impossible for nearby debris to reach the object's surface, for the same reason that "jump[ing] onto a carousel that's spinning at thousands of miles per hour" would be a challenge, lead study author Hannah Earnshaw, a postdoctoral researcher at California Institute of Technology in Pasadena, said in the statement.
Sometimes, however, a wobble in a neutron star's magnetic field can slow the object's rotation enough for debris to get pulled into the star's glowing halo of destruction, a feature similar to what might swirl around a black hole. The pulling in of debris like this could result in the sudden appearance and disappearance of an X-ray blast, like what was seen here.
If that’s the case, another flash of radiation is likely to appear in the same spot again, following some future magnetic field wobble. Scientists will continue monitoring the Fireworks galaxy for possible repeat performances of this unusual X-ray event, waiting for another unlucky star to go out with a bang.
- The 12 Strangest Objects in the Universe
- 15 Amazing Images of Stars
- 9 Strange Excuses for Why We Haven't Met Aliens Yet
Originally published on Live Science. | 0.887607 | 4.040515 |
WASHINGTON, May 31 - A giant asteroid will zip past Earth on Friday at the relatively close space distance of 3.6 million miles (5.8 million km) and its not alone. Astronomers studying the asteroid on Thursday noticed that it is bringing along a passenger its own moon.
Telescopes around the world began picking up distant images of the approaching two-mile (3.2-kilometer) wide asteroid on Wednesday, and a day later observers soon realized that the space rock known as 1998 QE2 had another, much smaller rock called a satellite moving in an orbit around it.
It was quite a bit of surprise that is something we did not expect, said NASA scientist Marina Brozovic, part of the observation team, during a teleconference Thursday from NASAs Jet Propulsion Laboratory in Pasadena, California.
What you can see is the larger object that is the primary, and then this little bright speck of light. That is the satellite and the satellite is in its orbit around the primary, like the moon would go around the earth, she said.
Its not all that rare for large asteroids to have company. About 16 percent of those hurtling through space near Earth have one or sometimes two moons.
The 1998 QE2 asteroid is roughly the length of nine cruise ships. It gets its name, not from Queen Elizabeth II of England, or the well-known ocean liner, but from a naming process that marks the year it was first located 1998 followed by an alphanumeric code that indicates the time of month the discovery took place.
This is one of the big ones. It was discovered about 15 years ago, and its one of the initial successes of our efforts to find the big asteroids that could hit the earth and cause global catastrophe, said Paul Chodas, an astronomer with NASA, which is tracking the asteroid to study its size, shape, rotation and surface features in an effort to learn more about its origin and composition.
Its about 15 times farther than the moon is from the earth so its a very comfortable distance but for an asteroid this size, thats a close shave, said Chodas.
We could see a few background stars, like white specks of light which werent moving, and then we actually saw this white star, what looked like a star, moving across the field very slowly, and we knew immediately that that was the asteroid because it was moving against the background of the stationery stars, said astronomer Nicola Loaring, joining the teleconference from the South African Astronomical Observatory in Sutherland, South Africa.
The QE2 is small and faint, but under clear weather conditions with a powerful telescope, backyard astronomers in the southern part of the United States should be able to see it.
The giant asteroids closest point to Earth will be Friday at 4:59 p.m. EDT (2059 GMT). Scientists estimate it will be at least another 200 years before it gets this close again. (PNA/RIA Novosti) | 0.821256 | 3.459653 |
Ganymede – Facts About The Largest & Most Massive Moon
Jupiter’s Giant Icy Moon
Ganymede is the largest moon in the solar system and is even bigger than Planet Mercury and the dwarf planet Pluto! Ganymede’s discovery in 1610 (along with the other Galilean Moons) played a significant role in the advancement of astronomy and our understanding of the solar system.
Fast Summary Facts About The Moon Ganymede
- Discovered: January 7th, 1610 by Galileo Galilei
- Name: Named after a beautiful mythological prince Jupiter turned into an eagle
- Size: Diameter of 5,268 km (3,273 miles)
- Moon Rank: Largest in the Solar System
- Surface Gravity: 0.146g (14.6% of Earth’s!)
- Orbit: Prograde and Circular
- Orbit Radius: 1,070,400 km
- Orbital Period: 7 days, 3 hours
- Orbital Speed: 10.88 km/sec
- Orbital Inclination: 0.20° (to Jupiter’s equator)
- Rotation: Synchronous (rotates once every revolution so the same side always faces Jupiter – known as tidally locked)
- Density: 1.94 g/cm3
- Surface: Water-ice and rocky material
- Surface Temperature: A frigid mean of -163 °C (between 70 - 150 K)
Read More Interesting Facts About Gigantic Ganymede!
- The discovery of Ganymede, and the other Galilean Moons in 1610, was the first time an object was observed to be orbiting another planet and lead to the understanding that the planets orbited the Sun and not the Earth!
- Like several other differentiated icy moons, Ganymede is believed to be made up of four main layers; a metallic iron-nickel core, a mantle of rock, a salt-water ocean and a shell of mostly ice (and some rock) that maybe 800 km (497 miles) thick!
- Images of Ganymede reveal that the moon has undergone extensive resurfacing since its formation as the surface terrain is a mixture of two distinct types. Dark, heavily cratered areas (believed to be the original surface) cover 40% of the surface with the remaining area consisting of a lighter grooved terrain (younger in age) which forms complex patterns unique to Ganymede. The grooves were likely formed from extensional faults (caused by ancient tidal heating during a possible period of unstable orbital resonance) which released liquid from the subsurface.
- The surface is primarily composed of water-ice, silicate rock material, carbon dioxide and a mixture of other space weathered dark material and compounds.
- Bright rays of impact debris radiate from craters as you would expect of exposed water-ice.
- The Hubble Space Telescope observed in 1996 that Ganymede has a very thin atmosphere composed of oxygen.
- Ganymede is the only moon in the solar system observed to have a magnetosphere (typically only planets have these), but is it entirely enclosed by Jupiter’s magnetosphere.
- The Voyager spacecraft observed that Ganymede has polar caps which are likely composed of water frost due to the uneven distribution of the magnetic field.
- In 2015 Scientists utilizing images from Hubble observed Ganymede’s aurora being influenced by a subsurface salt-water ocean.
- Ganymede is locked in a 1:2:4 orbital resonance with the Galilean moons Europa and Io. Ganymede completes 1 orbit for every 4 that Io does and 2 that Europa completes.
- Ganymede is believed to have formed by the accretion of the gas and dust that surrounded Jupiter after the planet was formed during the Solar Systems formation 4.5 billion years ago.
- The Pioneer 10, Voyager I and Voyager II spacecraft were the first to image Ganymede in detail, with additional observations made during the New Horizons flyby. The first probe to orbit Jupiter, Galileo, made extensive studies of the moon during its 6 encounters, passing within 264 km (164 miles) of the surface!
- A specific mission to study Jupiter’s icy moons the European Space Agency's JUICE mission (JUpiter ICy Moons Explorer) will arrive at Jupiter in 2030 focusing on the (potentially habitable) icy moons of Europa, Callisto and eventually enter orbit around Ganymede! | 0.889061 | 3.52644 |
Few people over the course of history have had a hand in discovering an atomic element. Yet nuclear chemist Dawn Shaughnessy joined a team of scientists from Lawrence Livermore National Laboratory (LLNL) and Russia that discovered five elements from 1989 to 2010.
Now she leads the Nuclear and Radiochemistry Group of the Physics and Life Sciences Directorate at LLNL and uses the National Ignition Facility (NIF) to generate some of the most extreme conditions in our solar system for high energy density experiments.
"NIF is the brightest neutron source in the world, and we use it to produce nuclear reactions that are relevant to stockpile stewardship and nuclear forensics programs. The reactions cannot be done by using accelerators or other means," said Shaughnessy, who also is serving a one-year appointment as scientific editor of the Laboratory’s Science & Technology Review.
Her first experience with NIF came before it was even operational. She joined a working group to determine whether nuclear science could be performed at NIF, and, if so, what types of diagnostics would be needed for making the measurements.
"I was fascinated," she said. "It was really cutting-edge stuff. You could make measurements in a plasma. No one else in the world was able to do that."
She began investigating how to make experimental platforms for studying the nuclear reactions of materials of interest, such as the elements nickel, yttrium and zirconium (see "Providing Data for Nuclear Detectives"). But only over the last couple of years did her team develop a technique capable of doping target capsules with these elements.
Serving as the NIF target is a 2-millimeter-diameter capsule lined on the inner surface with extremely small amounts of the material (about 1016 atoms) and filled with deuterium and tritium (DT) gas. The neutrons produced by the DT fusion during the shot bombard the material and cause nuclear reactions to occur. The fusion energy blows the products of the reaction outward, and the resulting solid debris is collected by specialized diagnostic instruments so that important radiochemical characteristics, such as rates of reactions, can be evaluated back inside a laboratory.
"Astrophysicists also are interested in these types of reactions because of NIF’s ability to duplicate the conditions at the interior of stars," Shaughnessy said.
By studying nuclear reactions within the star-like plasma generated by NIF, researchers can better explore nuclear synthesis, the stellar process that eventually creates heavier elements by fusing together lighter elements and particles. Sometimes this process, which is a progression of different nuclear reactions, must first create lighter elements before heavier ones can be created.
One such nuclear reaction under investigation occurs inside a class of stars that have masses on the order of the sun. It has boron absorbing a proton to form beryllium and an alpha particle. This nuclear reaction illustrates the type of interactions between atoms and particles that interest nuclear chemists.
As is true for so many of the projects at LLNL, the search for basic science understanding can yield big returns for other programs. Through the Discovery Science program, about 8 percent of NIF’s shots each year are dedicated to these types of experiments.
"Everything we’ve done for Discovery Science ties exactly into the platforms that we are developing for the Stockpile Stewardship Program," Shaughnessy said. "It has helped teach us how to dope capsules with materials, how to collect materials coming out of a shot and how to conduct various analyses."
But it is not just in the stellar cauldrons of stars in other galaxies where atomic concoctions are brewed. It happens right here in our solar system, without even having to escape Earth’s gravitational force. And from early on, this attracted Shaughnessy.
"Einsteinium is my favorite element," she said. "It doesn’t get enough credit because its chemistry is relatively ordinary. But I think it is really cool."
Her affinity toward einsteinium wells from her Ph.D. research at the University of California, Berkeley, into the fission of this synthetic, radioactive element. But after graduation, she turned in the opposite direction at Lawrence Berkeley National Laboratory by studying environmental factors of plutonium, which she feels is one of the most interesting elements because it has many oxidation states and forms, and neptunium, plutonium’s next-door neighbor on the periodic table.
This radioactive background is what led Shaughnessy to join LLNL’s Stockpile Radiochemistry Group in 2002, which is the same year she began hunting for elements that had never been observed before. The five elements that the team discovered were forged in a particle accelerator at Flerov Laboratory of Nuclear Reactions in Russia.
"The heavy element program at the Lab was very small," said Shaughnessy, who became the team’s principal investigator in 2005. "It was a team effort by people who were really dedicated to the science. Most of us had a background in it from somewhere else."
They filled out the bottom row of the periodic table by co-discovering the heavy elements flerovium (atomic number 114), moscovium (115), livermorium (116), tennessine (117) and oganesson (118) (see "Collaboration Expands the Periodic Table, One Element at a Time").
If any of these short-lived, synthetic elements have familiar sounding names, like livermorium, it might be because many elements that appear in the latter part of the periodic table are given names to honor people and places connected to important achievements in science. Shaughnessy recalls that the name davincium was tossed around during this period of discovery, and she hopes it will be used one day in commemoration of the early days of scientific investigation.
It is hard not to envision Leonardo da Vinci, sketching his latest invention on a table while his Italian robe flowed around him. Shaughnessy, however, looked in a much more futuristic direction for her wardrobe inspiration: she owns a custom-made Jedi robe from a Jedi robe shop in England.
"I am an enormous fan of ‘Star Wars,’" she said — no surprise to anyone who has worked with her. "I’ve been a fan since it first came out in 1977, when I saw it in a theater and connected with it at a young age. ‘Star Wars’ has always been a part of me. I still have my Star Wars figures. And now that we have new Star Wars movies again, I can get to share it with my daughter. I’ve probably seen the movies hundreds of times by this point."
Even at NIF, the force is strong with Shaughnessy. The influence runs deep. When trying to name a newly developed solid debris collecting diagnostic — which happens to look spaceship-like — she came up with Vast Area Detector for Experimental Radiochemistry, or VADER. She quickly points out, though, that she is of course aligned with the light side of the force — or, as in this case, the "laser light side."
Shaughnessy’s passion for this epic science fiction saga has helped propel her to transcend real-world boundaries, where science is fact and breakthroughs bring distant worlds much closer to home.
stark8 [at] llnl.gov | 0.800776 | 3.175166 |
Welcome back to Constellation Friday! Today, in honor of the late and great Tammy Plotner, we will be dealing with the compass – the Circinus constellation!
In the 2nd century CE, Greek-Egyptian astronomer Claudius Ptolemaeus (aka. Ptolemy) compiled a list of all the then-known 48 constellations. This treatise, known as the Almagest, would be used by medieval European and Islamic scholars for over a thousand years to come, effectively becoming astrological and astronomical canon until the early Modern Age.
Over time, the number of recognized constellations has grown as astronomers and explorers became aware of other stars visible from other location around the world. By the 20th century, the IAU adopted a modern catalog of 88 Constellations. One of these is the Circinus constellation, a small, faint constellation located in the southern skies. It is bordered by the constellations Apus, Centaurus, Lupus, Musca, Norma, Triangulum Australe.
Name and Meaning:
Because Circinus was unknown to the ancient Greeks and Romans, it has no mythology associated with it. The three brightest stars form a narrow triangle. The shape is reminiscent of a drawing (or drafting) compass of the sort used to plot sea and sky charts. Nicolas Louis de Lacaille had a fascination with secular science and the thought of naming a constellation after a science tool fascinated him.
In this case, Circinus represents a drafting tool used in navigation, mathematics, technical drawing, engineering drawing, in cartography (drawing maps) – and which many elementary school age children use to learn to draw circles and in geometry to bi-sect lines, draw arcs and so forth. In this case, the device should not be confused with Pyxis, a constellation associated with a ship’s compass… despite the similarity in names with the Latin language!
History of Observation:
The small, faint southern constellation Circinus was created by Nicholas de Lacaille during his stay at the Cape of Good Hope in the mid-18th century. Circinus was given its current name in 1763, when Lacaille published an updated sky map with Latin names for the constellations he introduced.
On the map he created, Lacaille portrayed the constellations of Norma, Circinus, and Triangulum Australe as a set of draughtsman’s instruments – as a ruler, compass, and a surveyor’s level, respectively. This constellation has endured and became one of the 88 modern constellation recognized by the IAU in 1920.
Circinus has no bright stars and consists of only 3 main stars and 9 Bayer/Flamsteed designated stars. However, the constellation does have several Deep Sky Objects associated with it. For instance, there’s the Circinus Galaxy, a spiral galaxy located approximately 13 million light years distant that was discovered in 1975. The galaxy is notable for the gas rings inside it, one of which is a massive star-forming region, and its black hole-powered core.
Then there’s the X-ray double star known as Circinus X-1, which is located approximately 30,700 light years away and was discovered in 1969. This system is composed of a neutron star orbiting a main sequence star. Circinus is also home to the bright planetary nebula known as NGC 5315, which was created when a star went supernova and cast off its outer layers into space.
Then there’s NGC 5823 (aka. Caldwell 88), an open cluster located on the border between Circinus and Lupus. Located about 3,500 light years away, this cluster is about 800 million years old and spans about 12 light years.
Circinus is visible at latitudes between +10° and -90° and is best seen at culmination during the month of June. Start by taking out your binoculars for a look at Alpha Circini – a great visual double star. Located about 53.5 light years from Earth, this stellar pair isn’t physically related but does make a unique target. The brighter of the two, Alpha, is a F1 Bright Yellow Dwarf that is a slight variable star. This contrasts very nicely with the fainter, red companion.
For the telescope, take a look at Gamma Circini – a faint star a little over five hundred light years from the Solar System. In the sky, it lies in the Milky Way, between bright Alpha Centauri and the Southern Triangle. Gamma Circini is a binary system, containing a blue giant star with a yellow, F-type, companion. Gamma is unique because it possess a stellar magnetic buoyancy!
For larger binoculars and telescopes, have a look at galactic star cluster NGC 5823 (RA 15 : 05.7 Dec -55 : 36). This dim cluster will appear to have several brighter members which are actually foreground stars, but does include Mira-type variable Y Circini. While it will be hard to distinguish from the rich, Milky Way star fields, you will notice an elliptical shaped compression of stars with an asterism which resembles and open umbrella.
For large telescopes, check out ESO 97-G13 – the “Circinus Galaxy”. Located only 4 degrees below the Galactic plane, and 13 million light-years away (RA 14h 13m 9.9s Dec 65° 20? 21?), this Seyfert Galaxy is undergoing tumultuous changes, as rings of gas are being ejected from the galactic core. While it can be spotted in a small telescope, science didn’t notice it until 25 years ago!
Be sure to check out The Messier Catalog while you’re at it!
For more information, check out the IAUs list of Constellations, and the Students for the Exploration and Development of Space page on Canes Venatici and Constellation Families. | 0.820844 | 3.434962 |
Atmospheric convection is the result of a parcel-environment instability, or temperature difference layer in the atmosphere. Different lapse rates within dry and moist air masses lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to increased winds, cumulus cloud development, and decreased surface dew points. Moist convection leads to thunderstorm development, which is often responsible for severe weather throughout the world. Special threats from thunderstorms include hail, downbursts, and tornadoes.
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There are a few general archetypes of atmospheric instability that are used to explain convection (or lack thereof). A necessary (but not sufficient) condition for convection is that the environmental lapse rate (the rate of decrease of temperature with height) is steeper than the lapse rate experienced by a rising parcel of air. When this condition is met, upward-displaced air parcels can become buoyant and thus experience a further upward force. Buoyant convection begins at the level of free convection (LFC), above which an air parcel may ascend through the free convective layer (FCL) with positive buoyancy. Its buoyancy turns negative at the equilibrium level (EL), but the parcel's vertical momentum may carry it to the maximum parcel level (MPL) where the negative buoyancy decelerates the parcel to a stop. Integrating the buoyancy force over the parcel's vertical displacement yields Convective Available Potential Energy (CAPE), the Joules of energy available per kilogram of potentially buoyant air. CAPE is an upper limit for an ideal undiluted parcel, and the square root of twice the CAPE is sometimes called a thermodynamic speed limit for updrafts, based on the simple kinetic energy equation.
However, such buoyant acceleration concepts give an oversimplified view of convection. Drag is an opposite force to counter buoyancy , so that parcel ascent occurs under a balance of forces, like the terminal velocity of a falling object. Buoyancy may be reduced by entrainment, which dilutes the parcel with environmental air. See the CAPE, buoyancy, and parcel links for a more in depth mathematical explanation of these processes.
Atmospheric convection is called deep when it extends from near the surface to above the 500 hPa level, generally stopping at the tropopause at around 200 hPa. Most atmospheric deep convection occurs in the tropics as the rising branch of the Hadley circulation; and represents a strong local coupling between the surface and the upper troposphere which is largely absent in winter midlatitudes. Its counterpart in the ocean (deep convection downward in the water column) only occurs at a few locations. While less dynamically important than in the atmosphere, such oceanic convection is responsible for the worldwide existence of cold water in the lowest layers of the ocean.
A thermal column (or thermal) is a vertical section of rising air in the lower altitudes of the Earth's atmosphere. Thermals are created by the uneven heating of the Earth's surface from solar radiation. The Sun warms the ground, which in turn warms the air directly above it. The warmer air expands, becoming less dense than the surrounding air mass, and creating a thermal low. The mass of lighter air rises, and as it does, it cools due to its expansion at lower high-altitude pressures. It stops rising when it has cooled to the same temperature as the surrounding air. Associated with a thermal is a downward flow surrounding the thermal column. The downward moving exterior is caused by colder air being displaced at the top of the thermal. Another convection-driven weather effect is the sea breeze.
Warm air has a lower density than cool air, so warm air rises within cooler air, similar to hot air balloons. Clouds form as relatively warmer air carrying moisture rises within cooler air. As the moist air rises, it cools causing some of the water vapor in the rising packet of air to condense. When the moisture condenses, it releases energy known as latent heat of vaporization which allows the rising packet of air to cool less than its surrounding air, continuing the cloud's ascension. If enough instability is present in the atmosphere, this process will continue long enough for cumulonimbus clouds to form, which support lightning and thunder. Generally, thunderstorms require three conditions to form: moisture, an unstable airmass, and a lifting force (heat).
All thunderstorms, regardless of type, go through three stages: the developing stage, the mature stage, and the dissipation stage. The average thunderstorm has a 24 km (15 mi) diameter. Depending on the conditions present in the atmosphere, these three stages take an average of 30 minutes to go through.
There are four main types of thunderstorms: single-cell, multicell, squall line (also called multicell line) and supercell. Which type forms depends on the instability and relative wind conditions at different layers of the atmosphere ("wind shear"). Single-cell thunderstorms form in environments of low vertical wind shear and last only 20–30 minutes. Organized thunderstorms and thunderstorm clusters/lines can have longer life cycles as they form in environments of significant vertical wind shear, which aids the development of stronger updrafts as well as various forms of severe weather. The supercell is the strongest of the thunderstorms, most commonly associated with large hail, high winds, and tornado formation.
The latent heat release from condensation is the determinate between significant convection and almost no convection at all. The fact that air is generally cooler during winter months, and therefore cannot hold as much water vapor and associated latent heat, is why significant convection (thunderstorms) are infrequent in cooler areas during that period. Thundersnow is one situation where forcing mechanisms provide support for very steep environmental lapse rates, which as mentioned before is an archetype for favored convection. The small amount of latent heat released from air rising and condensing moisture in a thundersnow also serves to increase this convective potential, although minimally. There are also three types of thunderstorms: orographic, air mass, and frontal.
Boundaries and forcing
Despite the fact that there might be a layer in the atmosphere that has positive values of CAPE, if the parcel does not reach or begin rising to that level, the most significant convection that occurs in the FCL will not be realized. This can occur for numerous reasons. Primarily, it is the result of a cap, or convective inhibition (CIN/CINH). Processes that can erode this inhibition are heating of the Earth's surface and forcing. Such forcing mechanisms encourage upward vertical velocity, characterized by a speed that is relatively low to what one finds in a thunderstorm updraft. Because of this, it is not the actual air being pushed to its LFC that "breaks through" the inhibition, but rather the forcing cools the inhibition adiabatically. This would counter, or "erode" the increase of temperature with height that is present during a capping inversion.
Forcing mechanisms that can lead to the eroding of inhibition are ones that create some sort of evacuation of mass in the upper parts of the atmosphere, or a surplus of mass in the low levels of the atmosphere, which would lead to upper level divergence or lower level convergence, respectively. Upward vertical motion will often follow. Specifically, a cold front, sea/lake breeze, outflow boundary, or forcing through vorticity dynamics (differential positive vorticity advection) of the atmosphere such as with troughs, both shortwave and longwave. Jet streak dynamics through the imbalance of Coriolis and pressure gradient forces, causing subgeostrophic and supergeostrophic flows, can also create upward vertical velocities. There are numerous other atmospheric setups in which upward vertical velocities can be created.
Concerns regarding severe deep moist convection
Buoyancy is key to thunderstorm growth and is necessary for any of the severe threats within a thunderstorm. There are other processes, not necessarily thermodynamic, that can increase updraft strength. These include updraft rotation, low level convergence, and evacuation of mass out of the top of the updraft via strong upper level winds and the jet stream.
Like other precipitation in cumulonimbus clouds hail begins as water droplets. As the droplets rise and the temperature goes below freezing, they become supercooled water and will freeze on contact with condensation nuclei. A cross-section through a large hailstone shows an onion-like structure. This means the hailstone is made of thick and translucent layers, alternating with layers that are thin, white and opaque. Former theory suggested that hailstones were subjected to multiple descents and ascents, falling into a zone of humidity and refreezing as they were uplifted. This up and down motion was thought to be responsible for the successive layers of the hailstone. New research (based on theory and field study) has shown this is not necessarily true.
The storm's updraft, with upwardly directed wind speeds as high as 180 kilometres per hour (110 mph), blow the forming hailstones up the cloud. As the hailstone ascends it passes into areas of the cloud where the concentration of humidity and supercooled water droplets varies. The hailstone's growth rate changes depending on the variation in humidity and supercooled water droplets that it encounters. The accretion rate of these water droplets is another factor in the hailstone's growth. When the hailstone moves into an area with a high concentration of water droplets, it captures the latter and acquires a translucent layer. Should the hailstone move into an area where mostly water vapour is available, it acquires a layer of opaque white ice.
Furthermore, the hailstone's speed depends on its position in the cloud's updraft and its mass. This determines the varying thicknesses of the layers of the hailstone. The accretion rate of supercooled water droplets onto the hailstone depends on the relative velocities between these water droplets and the hailstone itself. This means that generally the larger hailstones will form some distance from the stronger updraft where they can pass more time growing As the hailstone grows it releases latent heat, which keeps its exterior in a liquid phase. Undergoing 'wet growth', the outer layer is sticky, or more adhesive, so a single hailstone may grow by collision with other smaller hailstones, forming a larger entity with an irregular shape.
The hailstone will keep rising in the thunderstorm until its mass can no longer be supported by the updraft. This may take at least 30 minutes based on the force of the updrafts in the hail-producing thunderstorm, whose top is usually greater than 10 kilometres (6.2 mi) high. It then falls toward the ground while continuing to grow, based on the same processes, until it leaves the cloud. It will later begin to melt as it passes into air above freezing temperature
Thus, a unique trajectory in the thunderstorm is sufficient to explain the layer-like structure of the hailstone. The only case in which we can discuss multiple trajectories is in a multicellular thunderstorm where the hailstone may be ejected from the top of the "mother" cell and captured in the updraft of a more intense "daughter cell". This however is an exceptional case.
A downburst is created by a column of sinking air that, after hitting ground level, spreads out in all directions and is capable of producing damaging straight-line winds of over 240 kilometres per hour (150 mph), often producing damage similar to, but distinguishable from, that caused by tornadoes. This is because the physical properties of a downburst are completely different from those of a tornado. Downburst damage will radiate from a central point as the descending column spreads out when impacting the surface, whereas tornado damage tends towards convergent damage consistent with rotating winds. To differentiate between tornado damage and damage from a downburst, the term straight-line winds is applied to damage from microbursts.
Downbursts are particularly strong downdrafts from thunderstorms. Downbursts in air that is precipitation free or contains virga are known as dry downbursts; those accompanied with precipitation are known as wet downbursts. Most downbursts are less than 4 kilometres (2.5 mi) in extent: these are called microbursts. Downbursts larger than 4 kilometres (2.5 mi) in extent are sometimes called macrobursts. Downbursts can occur over large areas. In the extreme case, a derecho can cover a huge area more than 320 kilometres (200 mi) wide and over 1,600 kilometres (990 mi) long, lasting up to 12 hours or more, and is associated with some of the most intense straight-line winds, but the generative process is somewhat different from that of most downbursts.
A tornado is a dangerous rotating column of air in contact with both the surface of the earth and the base of a cumulonimbus cloud (thundercloud), or a cumulus cloud in rare cases. Tornadoes come in many sizes but typically form a visible condensation funnel whose narrowest end reaches the earth and surrounded by a cloud of debris and dust.
Tornadoes wind speeds generally average between 64 kilometres per hour (40 mph) and 180 kilometres per hour (110 mph). They are approximately 75 metres (246 ft) across and travel a few kilometers before dissipating. Some attain wind speeds in excess of 480 kilometres per hour (300 mph), may stretch more than a 1.6 kilometres (0.99 mi) across, and maintain contact with the ground for more than 100 kilometres (62 mi).
Tornadoes, despite being one of the most destructive weather phenomena are generally short-lived. A long-lived tornado generally lasts no more than an hour, but some have been known to last for 2 hours or longer (for example, the Tri-state tornado). Due to their relatively short duration, less information is known about the development and formation of tornadoes. Generally any cyclone based on its size and intensity has different instability dynamics. The most unstable azimuthal wavenumber is higher for bigger cyclones .
The potential for convection in the atmosphere is often measured by an atmospheric temperature/dewpoint profile with height. This is often displayed on a Skew-T chart or other similar thermodynamic diagram. These can be plotted by a measured sounding analysis, which is the sending of a radiosonde attached to a balloon into the atmosphere to take the measurements with height. Forecast models can also create these diagrams, but are less accurate due to model uncertainties and biases, and have lower spatial resolution. Although, the temporal resolution of forecast model soundings is greater than the direct measurements, where the former can have plots for intervals of up to every 3 hours, and the latter as having only 2 per day (although when a convective event is expected a special sounding might be taken outside of the normal schedule of 00Z and then 12Z.).
Other forecasting concerns
Atmospheric convection can also be responsible for and have implications on a number of other weather conditions. A few examples on the smaller scale would include: Convection mixing the planetary boundary layer (PBL) and allowing drier air aloft to the surface thereby decreasing dew points, creating cumulus-type clouds which can limit a small amount of sunshine, increasing surface winds, making outflow boundaries/and other smaller boundaries more diffuse, and the eastward propagation of the dryline during the day. On the larger scale, rising of air can lead to warm core surface lows, often found in the desert southwest.
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- Rostami, Masoud; Zeitlin, Vladimir (2018). "An improved moist-convective rotating shallow-water model and its application to instabilities of hurricane-like vortices". Quarterly Journal of the Royal Meteorological Society. 144 (714): 1450–1462. Bibcode:2018QJRMS.144.1450R. doi:10.1002/qj.3292. | 0.844183 | 3.498708 |
These photos were taken in Fort Lauderdale, FL on March 4, 2006. She used a Kodak digital camera CX7530 5.0MP.[and from another] Using always my digital cam REVIA KD-220Z in Italy on March 7, 2006. The corpus seems smaller than the previous image and on the left side of the Sun. [and from another] I wonder if these are moon swirls in the tail?
When Planet X became visible in early 2001 as a dim blur viewed at observatories, or as what appeared to be a very dim star in infrared images in early 2002, or as a star not on the star charts during CCD imaging in the Fall of 2002, the shrouding dust cloud and tail of Planet X was either not an issue or was seen to be trailing behind the rapidly moving planet. When it put on the brakes as it arrived at the Sun, in the Summer of 2003, the tail logically wafted past the halting Planet X to blow past the Sun and deposit some red dust on the Earth. It also interfered with the electric grid in many countries in August-September of 2003, creating surges and brownouts, crashing the grids. Then the dust cloud settled into clinging to and blowing outward from the N Pole of Planet X, which was pointing toward the S Pole of the Sun as it rounded it and moved up toward the Sun's middle. Thus, from Dec, 2003 to the recent past, the tail was blowing toward the Sun, and the debris and red dust and many dramatic bright moon swirl dances not as much in evidence. 2004 and into 2005 were a relatively quiet time, tail wise, as Planet X gradually rose to the Ecliptic, while rounding the Sun, and started outbound toward the Earth, trapped in her halted orbit in front of Planet X.
We have stated that as Planet X does a slow 270° roll to position itself to be above the
Sun's Ecliptic, where it will point its S Pole at the Sun's N Pole and quickly exit the solar
system, it first must swing its N Pole away from the Sun. It does so in a retrograde
manner, as it rotates retrograde and is in a retrograde orbit while passing the Sun. As the
N Pole swings round to the right, as viewed from the northern hemisphere, the tail
likewise begins to appear to the right of the Sun. The Earth, desperate to escape the
hose of magnetic particles coming from the N Pole of Planet X, leans to the left as far as
possible in the eddy flow of particles it is trapped in, caught in the path of Planet X,
moving steadily and inexorably toward the Earth as it leaves the Sun. Thus sightings and
photos of the corpus of Planet X, the Second Sun, have been captured of late, even
casting a reflection on the water (photo at right). What happens to the immense,
charged, tail of Planet X during this slow 270° roll process?
When far away from the Earth, the tail appears as an adjunct to the corpus, wafting off to one side or surrounding and somewhat behind the corpus. But as Planet X comes closer to the Earth, and the tail is blown more toward Earth than away, the view of the tail from Earth changes. The tail, as we have mentioned many times, is charged, and this is the reason it clings to and follows Planet X, which is an immense planetary magnet. The tail blows away from the N Pole of Planet X, which is the outbound port of the magnetic particle flow that is the magnetic field of a planet. But being charged, due to the iron oxide dust that is the primary component of the tail, it wants to stay aligned with the magnetic field of Planet X. Thus, the tail wraps around toward the S Pole of Planet X, along the magnetic field lines surrounding Planet X. In the past, when Planet X was at a distance, it and the tail could be seen on this or that side of the Sun. But when Planet X is coming close, as it is now, and standing between the Earth and the Sun, as it is now, with the tail flowing along the magnetic field lines of Planet X, it can appear on both sides of the Sun.
Does this mean that mankind will shortly have more of the tail effects, here on Earth? The Earth cannot escape this, and folklore speaks to this, but just what the timing of these assaults will be, we will not say, as the establishment is still not sharing what they know about this monster and its certain passage with the common man. | 0.864551 | 3.37769 |
eso1432 — Science Release
Two Families of Comets Found Around Nearby Star
Biggest census ever of exocomets around Beta Pictoris
22 October 2014
The HARPS instrument at ESO’s La Silla Observatory in Chile has been used to make the most complete census of comets around another star ever created. A French team of astronomers has studied nearly 500 individual comets orbiting the star Beta Pictoris and has discovered that they belong to two distinct families of exocomets: old exocomets that have made multiple passages near the star, and younger exocomets that probably came from the recent breakup of one or more larger objects. The new results will appear in the journal Nature on 23 October 2014.
Beta Pictoris is a young star located about 63 light-years from the Sun. It is only about 20 million years old and is surrounded by a huge disc of material — a very active young planetary system where gas and dust are produced by the evaporation of comets and the collisions of asteroids.
Flavien Kiefer (IAP/CNRS/UPMC), lead author of the new study sets the scene: “Beta Pictoris is a very exciting target! The detailed observations of its exocomets give us clues to help understand what processes occur in this kind of young planetary system.”
For almost 30 years astronomers have seen subtle changes in the light from Beta Pictoris that were thought to be caused by the passage of comets in front of the star itself. Comets are small bodies of a few kilometres in size, but they are rich in ices, which evaporate when they approach their star, producing gigantic tails of gas and dust that can absorb some of the light passing through them. The dim light from the exocomets is swamped by the light of the brilliant star so they cannot be imaged directly from Earth.
To study the Beta Pictoris exocomets, the team analysed more than 1000 observations obtained between 2003 and 2011 with the HARPS instrument on the ESO 3.6-metre telescope at the La Silla Observatory in Chile.
The researchers selected a sample of 493 different exocomets. Some exocomets were observed several times and for a few hours. Careful analysis provided measurements of the speed and the size of the gas clouds. Some of the orbital properties of each of these exocomets, such as the shape and the orientation of the orbit and the distance to the star, could also be deduced.
This analysis of several hundreds of exocomets in a single exo-planetary system is unique. It revealed the presence of two distinct families of exocomets: one family of old exocomets whose orbits are controlled by a massive planet , and another family, probably arising from the recent breakdown of one or a few bigger objects. Different families of comets also exist in the Solar System.
The exocomets of the first family have a variety of orbits and show a rather weak activity with low production rates of gas and dust. This suggests that these comets have exhausted their supplies of ices during their multiple passages close to Beta Pictoris .
The exocomets of the second family are much more active and are also on nearly identical orbits . This suggests that the members of the second family all arise from the same origin: probably the breakdown of a larger object whose fragments are on an orbit grazing the star Beta Pictoris.
Flavien Kiefer concludes: “For the first time a statistical study has determined the physics and orbits for a large number of exocomets. This work provides a remarkable look at the mechanisms that were at work in the Solar System just after its formation 4.5 billion years ago.”
Moreover, the orbits of these comets (eccentricity and orientation) are exactly as predicted for comets trapped in orbital resonance with a massive planet. The properties of the comets of the first family show that this planet in resonance must be at about 700 million kilometres from the star — close to where the planet Beta Pictoris b was discovered.
This research was presented in a paper entitled "Two families of exocomets in the Beta Pictoris system" which will be published in the journal Nature on 23 October 2014.
The team is composed of F. Kiefer (Institut d’astrophysique de Paris [IAP], CNRS, Université Pierre & Marie Curie-Paris 6, Paris, France), A. Lecavelier des Etangs (IAP), J. Boissier (Institut de radioastronomie millimétrique, Saint Martin d’Hères, France), A. Vidal-Madjar (IAP), H. Beust (Institut de planétologie et d'astrophysique de Grenoble [IPAG], CNRS, Université Joseph Fourier-Grenoble 1, Grenoble, France), A.-M. Lagrange (IPAG), G. Hébrard (IAP) and R. Ferlet (IAP).
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
Alain Lecavelier des Etangs
Institut d'astrophysique de Paris (IAP)/CNRS/UPMC
Cell: +33 6 21 75 12 03
Institut d'astrophysique de Paris (IAP)/CNRS/UPMC and School of Physics and Astronomy, Tel Aviv University
France / Israel
ESO education and Public Outreach Department
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591 | 0.852151 | 3.783576 |
The US space agency confirmed that Saturn’s emblematic rings are being dragged towards the planet by gravity, like a dusty rain of ice particles under the influence of the planet’s magnetic field.
Saturn’s rings are made of an innumerable amount of small particles, composed mainly of frozen water and rocky material.
There is still no consensus as to their mechanism of formation; some features of the rings suggest a relatively recent origin, but theoretical models indicate they are likely to have formed early in the Solar System’s history.
Their destiny, however, is now clear to scientists. Experts say that the icon rings have around 100 million years left, after which they will disappear from sight.
“We estimate that this ‘ring rain’ drains an amount of water products that could fill an Olympic-sized swimming pool from Saturn’s rings in half an hour,” explained James O’Donoghue of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
“From this alone, the entire ring system will be gone in 300 million years, but add to this the Cassini-spacecraft measured ring-material detected falling into Saturn’s equator, and the rings have less than 100 million years to live,” O’Donoghue added.
As explained by experts, the ring particles are caught in a balancing tug-o’-war between the pull of the planets gravity, which wants to draw them back into the planet, and their orbital velocity, which wants to fling them outward into space.
Now, experts have revealed that the rings are raining down on Saturn at a much faster rate.
“This is relatively short, compared to Saturn’s age of over 4 billion years,” explained experts.
As e explained in a new study published in the journal Icarus, Saturn’s rings are at their mid life point, which means that they aren’t probably older than 100 million years, since it would take that long for the C-ring to become what it is today assuming it was once as dense as the planet’s B-ring. | 0.825082 | 3.513713 |
A telescope in the South Pole observing traces of the Big Bang that created the universe has turned up the first evidence of a key moment in that process: the blink-of-an-eye expansion of the universe from a dot into a vast soup of energy and particles.
The discovery, using the BICEP2 telescope at the Amundsen-Scott South Pole Station, provided the first strong evidence of “cosmic inflation,” which scientists say occurred in a fraction of the first second of the universe’s existence, when it expanded billions of times over. The process was first proposed by MIT scientist Alan Guth in 1981.
Evidence of cosmic inflation came through identifying the effects of gravitational waves for the first time. Gravitational waves are ripples in space-time believed to have been created by the enormous forces at work during cosmic inflation. The finding emerged from a collaborative effort led by researchers at the Harvard-Smithsonian Center for Astrophysics (CfA), Stanford University, the California Institute of Technology (Caltech), and the University of Minnesota.
The waves’ discovery had been “one of the most important goals in cosmology,” according to John Kovac, Harvard associate professor of astronomy and the BICEP2 project leader. Their existence had been theorized and sought by astronomers, but not confirmed until now.
“Theorists speak about them with confidence, but still it’s a wild story,” Kovac said. “The amazing thing is it has a testable consequence that we can build a machine and go out and [look for]. The signature that we’ve measured with our telescope … is not expected to be there except for this prediction of inflation.”
Cosmology is a branch of astronomy that seeks to understand the universe’s broad structure and its evolution since the Big Bang. One of cosmology’s most important tools is a distant echo of the Big Bang, extremely faint background radiation called the cosmic microwave background (CMB).
Astronomers analyzing data from BICEP2, which scanned the clear polar skies for three years through 2012, searched for a polarization pattern in the CMB called “B-modes,” believed to have been created by gravitational waves.
Though researchers found the pattern they were seeking, they were surprised at the strength of the signal and spent three years analyzing data to be sure they were correct in their findings.
Kovac, who credited the work of the dozen people in his laboratory and those at the collaborating labs, has been trying to confirm the gravitational waves for the last 12 years. When he saw them revealed in the data, he said he felt a “mixture of awe and elation,” quickly followed by a determination to ensure they hadn’t been produced by an error somewhere.
“We are extremely cautious scientists, and detecting this signal, honestly, produced a mixture of … awe and elation, and intense stress. We want to get this right,” Kovac said. “And that’s been our state for quite a long time. We’ve been extremely cautious in our approach to analyzing this data.”
While Kovac said the results are “strong evidence” that cosmic inflation occurred, he stopped short of saying they were proof of inflation. Theoretical astrophysicist Avi Loeb, Frank B. Baird Jr. Professor of Science and Harvard Astronomy Department chair, said the findings offer new insights into some of the most basic questions about the universe.
“These results are not only a smoking gun for inflation; they also tell us when inflation took place and how powerful the process was,” Loeb said.
The BICEP2 telescope was operated as part of a broader collaboration involving about a dozen institutions and led by Kovac, Clement Pryke from the University of Minnesota, Jamie Bock from Caltech and NASA’s Jet Propulsion Laboratory, and Chao-Lin Kuo from Stanford’s SLAC National Accelerator Laboratory.
The four appeared at a news conference Monday at the CfA’s offices in Cambridge to announce the discovery, which generated worldwide media attention and immense excitement in the scientific community.
Marc Kamionkowski, a professor of physics and astronomy at Johns Hopkins who was not part of BICEP2 but who attended the CfA news conference, said the discovery was “cosmology’s missing link” that has been sought for 20 years. The findings, he said, will require “new physics” beyond the currently understood Standard Model.
Several teams of astronomers have been searching for the same signal, but the BICEP team was the first to do so, starting work in 2001, which gave them a head start, Bock said. BICEP 2 is one of three telescopes the collaborators operate at the South Pole, where the clear, dry air makes it easier to detect the faint signal from the cosmic microwave background.
“It’s a fantastic place to do science,” said Kovac, who has traveled to the South Pole 23 times. “The South Pole is paradise if you’re a CMB experimentalist … It’s the closest you can get to operating a telescope in space for microwave observation and yet still be on the ground.”
According to theory, the universe’s first second was a busy one. Among other things, the four fundamental forces of the universe separated into gravity, electromagnetism, and the strong and weak forces that work at the atomic scale. The first particles were formed, including the recently discovered Higgs boson, and the universe became much larger.
The expansion occurred during the inflationary epoch, which saw the fabric of space time itself grow in volume 1078 times in a process so rapid and energetic that it sent gravity waves rippling through the fabric of space time, to be detected by the BICEP2 team almost 14 billion years later.
Though the announcement was the culmination of years of work, researchers said that the findings pose more questions about conditions in the early universe, providing new avenues of exploration.
“This is not the end; this is the beginning,” Pryke said. “It’s mind-boggling to go looking for something like this and actually find it.” | 0.860497 | 4.083003 |
New research from NASA’s Spitzer Space Telescope reveals that asteroids somewhat near Earth, termed near-Earth objects, are a mixed bunch, with a surprisingly wide array of compositions. Like a piñata filled with everything from chocolates to fruity candies, these asteroids come in assorted colors and compositions. Some are dark and dull; others are shiny and bright. The Spitzer observations of 100 known near-Earth asteroids demonstrate that the objects’ diversity is greater than previously thought.
The findings are helping astronomers better understand near-Earth objects as a whole — a population whose physical properties are not well known.
“These rocks are teaching us about the places they come from,” said David Trilling of Northern Arizona University, Flagstaff, lead author of a new paper on the research appearing in the September issue of Astronomical Journal. “It’s like studying pebbles in a streambed to learn about the mountains they tumbled down.”
After nearly six years of operation, in May 2009, Spitzer used up the liquid coolant needed to chill its infrared detectors. It is now operating in a so-called “warm” mode (the actual temperature is still quite cold at 30 Kelvin, or minus 406 degrees Fahrenheit). Two of Spitzer’s infrared channels, the shortest-wavelength detectors on the observatory, are working perfectly.
One of the mission’s new “warm” programs is to survey about 700 near-Earth objects, cataloging their individual traits. By observing in infrared, Spitzer is helping to gather more accurate estimates of asteroids’ compositions and sizes than what is possible with visible light alone. Visible-light observations of an asteroid won’t differentiate between an asteroid that is big and dark, or small and light. Both rocks would reflect the same amount of visible sunlight. Infrared data provide a read on the object’s temperature, which then tells an astronomer more about the actual size and composition. A big, dark rock has a higher temperature than a small, light one because it absorbs more sunlight.
Trilling and his team have analyzed preliminary data on 100 near-Earth asteroids so far. They plan to observe 600 more over the next year. There are roughly 7,000 known near-Earth objects out of a population expected to number in the tens to hundreds of thousands.
“Very little is known about the physical characteristics of the near-Earth population,” said Trilling. “Our data will tell us more about the population, and how it changes from one object to the next. This information could be used to help plan possible future space missions to study a near-Earth object.”
The data show that some of the smaller objects have surprisingly high albedos (an albedo is a measurement of how much sunlight an object reflects). Since asteroid surfaces become darker with time due to exposure to solar radiation, the presence of lighter, brighter surfaces for some asteroids may indicate that they are relatively young. This is evidence for the continuing evolution of the near-Earth object population.
In addition, the fact that the asteroids observed so far have a greater degree of diversity than expected indicates that they might have different origins. Some might come from the main belt between Mars and Jupiter, and others could come from farther out in the solar system. This diversity also suggests that the materials that went into making the asteroids — the same materials that make up our planets — were probably mixed together like a big solar-system soup very early in its history.
The research complements that of NASA’s Wide-field Infrared Survey Explorer, or WISE, an all-sky infrared survey mission also up in space now. WISE has already observed more than 430 near-Earth objects — of these, more than 110 are newly discovered.
In the future, both Spitzer and WISE will tell us even more about the “flavors” of near-Earth objects. This could reveal new clues about how the cosmic objects might have dotted our young planet with water and organics — ingredients needed to kick-start life. | 0.887484 | 3.968355 |
South Africa is a very exciting place to do astronomy for many reasons. The most prominent reason? The MeerKAT telescope. In this post, I’m (finally) going to write about the most talked-about telescope on the African continent and why I’m so excited about it! I’ll tell you about the telescope, my involvement in it and why it’s so groundbreaking.
What is MeerKAT?
In technical terms, MeerKAT is a 64-dish radio interferometer telescope and is the precursor to the Square Kilometer Array telescope. MeerKAT receives astronomical signals across its 64 dishes, which provides an extremely high level of sensitivity. These signals come in the form of radio waves – the same kind of radio waves that you use to listen to 5FM, make cellphone calls with and connect to the WiFi over. Since radio waves are commonly used all over the world for everyday tasks, detecting them from space is particularly challenging. This is why the Karoo was chosen as the location for MeerKAT and subsequently SKA. It’s far from most cities and people, in a special ‘radio-quiet’ zone. With very little radio interference in the area and the high sensitivity that comes with 64 radio dishes, MeerKAT is able to detect extremely faint signals from the distant universe right here in South Africa!
My MeerKAT work
Although I’m not directly involved in MeerKAT through the South African Radio Astronomical Observatory or using radio observations, my Masters research is part of one of the ‘Large Survey Projects’ that are in-progress. The project – called LADUMA (Looking At the Distant Universe with the MeerKAT Array) – will measure faint, neutral hydrogen gas far back in the universe’s history. Although this gas is very difficult to detect, it’s the most abundant element in the universe and fuels the birth of stars.
Why am I so excited about this?
MeerKAT has – and will continue to – produced amazing science and it’s only a year old! It has already produced two papers published in Nature (most excitingly – the discovery of giant, radio bubbles at the center of the Milky Way) and its sensitivity has exceeded expectations. The technical upgrades and new modes that are still in development and are being added to the telescope will continue to improve its effectiveness and unlock new kinds of science.
Aside from the science – MeerKAT is South African! Unlike Table Mountain and the Kruger National Park and several other things that we’re proud of as South Africans – MeerKAT is something that we’ve built. When I was growing up, telescopes like the SKA, MeerKAT and SALT were a source of inspiration and interest for me as a future scientist. Now, it’s incredible to be part of these big projects.
MeerKAT has also created so many opportunities for South Africans to study and train as astronomers, engineers, computer scientists, and develop expertise in many different areas. Although many people work in astronomy and astronomy-related fields, a large portion of people take these skills to other fields that contribute to the country.
Overall, MeerKAT is proof that South Africa can be at the forefront of science and technology. It’s a massive undertaking that we’ve not only succeeded at – but excelled at. When there are so many other problems that we’re facing as a country – it’s a source of hope and a sign of progress. The future of science in South Africa is bright. | 0.81494 | 3.197904 |
A number of fixations plaguing the astrobiology community regarding the pre-requisites for life are retarding the development of biology and the search for new life in the universe. These fixations work as smoke screens to obscure the myriads of other types of life forms that may be thriving even in our Solar System. Astrobiologists, particularly at NASA, appear to have a dogmatic fixation on studying life only at the biochemical level, a pre-occupation with water as a substrate for life, adamant on only studying carbon-based life forms, restricted to a very narrow temperature range and scale; and not even noticing that all the life forms that they have imagined in their wildest models are only based on particles within the (physicists’) Standard Model.
Physics affects biology in a more fundamental way than even chemistry or biochemistry. New developments in physics should open up areas to consider more extreme life forms. If we find dark matter and supersymmetric particles – would biologists then start thinking about dark matter and supersymmetric life forms? Should we be talking about “quantum biology”? When physicists talk of parallel universes, would biologists consider symbiosis between life forms in parallel universes? Is Darwin’s tree of life complete? Where are its roots?
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Life at Extremely Small Scales – Nano and Quantum Life
Bacteria may be no larger than 10 microns; viruses no larger than 100 nanometers; molecules about 1 nanometer and atoms about 0.1 nanometers. Does scale impose a barrier to life or even consciousness? If viruses are considered life forms (as some leading astrobiologists argue) then they constitute “nano-life”.
Consciousness may even exist at the quantum scale. “In some strange way an electron or a photon [or any other elementary particle] seems to ‘know’ about changes in the environment and appears to respond accordingly,” says physicist Danah Zohar. A group at the Weizmann Institute in Israel has done a variation of the famous “double-slit” experiment. They used electrons, instead of photons, and observed how the resultant interference pattern (which indicates wave-like properties of the particle) dissipated the longer you watched the electrons go through the slits. As a wave the electron passes through both slits simultaneously but if, according to E Buks, it “senses” that it is being watched, the electron (as a particle) goes through only one path, diminishing the interference pattern. Elementary particles (such as photons and electrons) appear to possess a certain degree of “intelligence” and awareness of the environment. Renowned plasma and particle physicist, David Bohm, says “In some sense, a rudimentary mind-like quality is present even at the level of particle physics. As we go to subtlest levels this mind-like quality becomes stronger and more developed.”
In a new field called “quantum metaphysics”, Jay Alfred has proposed that consciousness is as fundamental a property of elementary particles as properties that make it “matter” or a “physical force” (for example, mass, spin, and charge) (see Conscious Particles, Fields and Waves, 2007). And just as mass, spin, and charge differ from one particle to another; it is probable that different particles have different degrees of consciousness. He has argued (see Jay Alfred, Our Invisible Bodies, 2006) that consciousness can manifest depending on the degree of quantum coherence and the intrinsic properties of the single particle. (This may be cited as the “Quantum Coherence Theory of Consciousness”.)
In studying particle consciousness we must not get distracted by their scale. In fact, (under quantum field theory) particles are excitations in a field that may be infinitely large. Every particle has a corresponding field. If a particle is considered a “unicellular life form” than a field of particles may be considered a “multicellular life form” – except that these “cells” go in and out of existence within the field. This obviously begs the question – Is the biochemical cell the smallest unit of life? If not, then a biological revolution, more important than the Copernican revolution in terms of its impact on society, is around the corner.
Life at Extremely Large Scales
Life at all scales is probably – including at the planetary, stellar and galactic scales; and even the universe and multiverse. The Gaia hypothesis has been proposed by James Lovelock and Lynn Margulis. Jay Alfred has proposed life at cosmic and global scales by using the “plasma metaphysics” model which believes that an extensive web of currents in space and on Earth exists which is both anatomically and physiologically similar to a neural network in the human brain. (See Are We Living in a Gigantic Brain? 2007) This web of currents in space not only looks like a neural network, it functions like one. We should not be surprised to see life being engineered using an electromagnetic substrate. A biochemical cell’s membrane is now thought to function like a semiconductor.
Perhaps a thought experiment could be enlightening. Imagine yourself as a cell within your brain carefully observing your environment with a nano-telescope. Would you consider your brain as being able to support consciousness? What you would see are neural cells alternately firing and resting; chemicals rushing to synapses and the zapping of nasty electrical currents – clearly not a very “habitable zone” for life or consciousness to exist – from your microscopic point of view. But we know better…
Could the plasma universe, with its network of currents, be a living, conscious entity? Was the quark-gluon plasma ball that inflated during the Big Bang a life form?
High Energy Biology – Life at High Energies and Temperatures
At high temperatures, molecules break up into atoms and atoms break up into a soup of sub-atomic particles called plasma. (Partially ionized gasses are also described as “plasma”.) Plasma life forms are likely to be the most common life form in the universe, given that plasma makes up more than 99% of our visible universe which is almost everywhere ionized. This is in stark contrast to complex carbon-based life forms, which according to the Rare Earth hypothesis proposed by Peter Ward and Donald Brownlee, would be rare in the universe due to a number of factors – including the need for an acceptable range of temperatures to survive.
Plasma is an ideal substrate for life at high temperatures. Plasma life forms would adapt to environments which would be considered hostile to carbon-based life forms. It is possible that plasma life forms were already present in the gas and materials that formed the Earth 4.6 billion years ago. Carbon-based biomolecular life forms only appeared 1 billion years later. Tsytovich and other scientists (including Lozneanu and Sanduloviciu, discussed below) have proposed that plasma life forms, in fact, spurred development of organic carbon-based life on Earth.
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In 2003 physicists; Erzilia Lozneanu and Mircea Sanduloviciu of Cuza University, Romania, described in their research paper Minimal Cell System created in Laboratory by Self-Organization (published in Chaos, Solitons & Fractals, volume 18, page 335), how they created plasma spheres in the laboratory that can grow, replicate and communicate – fulfilling most of the traditional requirements for biological cells. The physicists “grew” spheres from a few micrometers up to three centimeters in diameter. They are convinced that these plasma spheres offer a radically new explanation of how life began and proposed that they were precursors to biological evolution. Lozneanu plasma spheres can reproduce by replicating, just like bacteria which are generally considered “immortal” and do not undergo “apoptosis” or programmed cell death.
It is still a mystery in mainstream biology as to how DNA originated. An international scientific team has discovered that in the gravity-free environment of space, particles in plasma will beat together to form string-like filaments which will then twist into helical strands resembling DNA that are electrically charged and are attracted to each other. Using a computer model of molecular dynamics, V N Tsytovich and his colleagues of the Russian Academy of Science showed (in their paper entitled From Plasma Crystals and Helical Structures towards Inorganic Living Matter, published in the New Journal of Physics in August 2007) that particles in plasma can undergo self-organization as electric charges become separated and the plasma becomes polarized. “These complex, self-organized plasma structures exhibit all the necessary properties to qualify them as candidates for inorganic living matter”, says Tsytovich, “they are autonomous, they reproduce and they evolve”.
Past studies, subject to Earth’s gravity, have shown that if enough particles are injected into a low-temperature plasma, they will spontaneously organize into crystal-like structures or “plasma crystals”. Jay Alfred has characterized “subtle bodies” as plasma crystals in his 2006 book Our Invisible Bodies. He has written extensively about the anatomy and physiology of these bio plasma bodies generating a new field of research called “plasma metaphysics”.
According to plasma metaphysics (see Jay Alfred, Our Invisible Bodies, 2006), plasma is subject to self-organization through both thermodynamics and electrodynamics. Plasma life forms have various mechanisms for the absorption and distribution of energy – in other words, a metabolic system. These include both vortexes (equivalent to orifices in common biological systems) and filamentary currents (equivalent to tubes and circulatory systems in common biological systems) which are structured by magnetic fields and driven by electric fields. Information is stored in the nucleus of the bioplasma body as compressed waveforms (using Fourier transforms) and used for replication. Plasma life forms are also enclosed in a membrane (like the membrane of a biological cell) and selectively admit charged particles (just like the semi-permeable membranes of common biological systems that admit ions i.e. charged particles into the cell). These structures (vortexes, filaments, membranes and the nucleus) have been described in the metaphysical and even religious literature more than 2,000 years old in connection with what is commonly referred to as “subtle bodies”. With a membrane that separates the body from the environment, metabolic and information systems, these subtle bodies are, in fact, plasma life forms.
Dark Matter Life Forms
According to plasma metaphysics (see Jay Alfred, Our Invisible Bodies, 2006), dark matter consists largely of a magnetic plasma of largely non-standard particles or “dark plasma”. Despite the many experiments to concoct life out of chemicals, there has yet been no sign of life as complex as the simplest biological cell. One of the main unanswered questions remains as to how DNA, with its double helix structure, was formed. Computer simulations by Tsytovich have confirmed that helical strands are generated in the (complex) plasma that looks and function like DNA. At a more fundamental level, it is well known that double helical and corkscrew structures are signature features of plasma dynamics. Could the missing ingredients that gave rise to life include certain components which are now included under dark matter? Jay Alfred has proposed the “Dark Panspermia” hypothesis (see Plasma Life Forms – Dark Panspermia, 2007) which proposes that dark matter was carried by comets, meteorites, and asteroids as they traversed the dark matter-filled space around the solar neighborhood. As they impacted the Earth, dark plasma cells acted as templates for the formation of biochemical cells. Both dark matter and ordinary life forms co-evolved over vast stretches of time.
Perhaps a bacterial cell in solution should be “diluted” (similar to procedures often encountered in homeopathy) – by very slowly and meticulously taking apart each component of the bacteria. A healthy human cell should then be introduced into the solution to see if it would undergo reactions that would be similar to reactions caused by the same type of bacteria composed of visible ordinary matter. If it does (as would be expected and claimed by homeopathic theory) it will betray the presence of the dark matter counterpart of the visible bacteria.
Inter-Substrate (Plasma-Carbon) Symbiogenesis
Biologists are beginning to realize that cooperation was just as important as competition in the evolution of life’s diversity and resilience. Every cell in the human body contains a mitochondrion which is thought to be a bacterial cell which invaded an early eukaryote. Instead of being digested, both cells tolerated each other and began to live with each other – a merger which provided synergies to both. This is a startling example of symbiogenesis. But then every multi-cellular animal or plant is also an obvious example of cooperation rather than competition. More than a 1,000 trillion cells are living peacefully and co-operating in your body; together with 500 to 100,000 species of bacteria. In fact, there are about ten times as many bacteria as human cells in the human body. Does symbiosis extend further?
There is anecdotal evidence that plasma life forms formed symbiotic relationships with the abundant carbon-based life forms on Earth – particularly with hominids. Unlike other known species of animals, the unique brains of hominids allowed them to activate the higher energy bio plasma bodies that co-evolved with the physical-biochemical body without necessarily having any conscious awareness that they were accessing a different cognitive system. Relationships developed between the lower energy carbon-based bodies and the higher energy bio plasma bodies which were sustained, perhaps, for several millions of years up to the present. This allowed the higher energy bio plasma bodies to evolve in a unique way on Earth.
Do we need to expand the definition of life? When and how does a life form become conscious of itself? Is consciousness a fundamental attribute of physical matter like spin, mass, and charge which physicists themselves do not quite understand? Is the cell (as defined in mainstream biology) the smallest unit of life? Are the subtle bodies described in the metaphysical literature plasma life forms?
The new science of astrobiology at NASA appears to be limping along in its understanding of life in the universe probably because it is saddled with the heavy weight of fixations generated from a biology that is largely based on chemistry rather than the whole of physics. | 0.809988 | 3.173541 |
The thermosphere is a layer of Earth's atmosphere. The thermosphere is directly above the mesosphere and below the exosphere. It extends from about 90 km (56 miles) to between 500 and 1,000 km (311 to 621 miles) above our planet.
Temperatures climb sharply in the lower thermosphere (below 200 to 300 km altitude), then level off and hold fairly steady with increasing altitude above that height. Solar activity strongly influences temperature in the thermosphere. The thermosphere is typically about 200° C (360° F) hotter in the daytime than at night, and roughly 500° C (900° F) hotter when the Sun is very active than at other times. Temperatures in the upper thermosphere can range from about 500° C (932° F) to 2,000° C (3,632° F) or higher.
The boundary between the thermosphere and the exosphere above it is called the thermopause. At the bottom of the thermosphere is the mesopause, the boundary between the thermosphere and the mesosphere below.
Although the thermosphere is considered part of Earth's atmosphere, the air density is so low in this layer that most of the thermosphere is what we normally think of as outer space. In fact, the most common definition says that space begins at an altitude of 100 km (62 miles), slightly above the mesopause at the bottom of the thermosphere. The space shuttle and the International Space Station both orbit Earth within the thermosphere!
Below the thermosphere, gases made of different types of atoms and molecules are thoroughly mixed together by turbulence in the atmosphere. Air in the lower atmosphere is mainly composed of the familiar blend of about 80% nitrogen molecules (N2) and about 20% oxygen molecules (O2). In the thermosphere and above, gas particles collide so infrequently that the gases become somewhat separated based on the types of chemical elements they contain. Energetic ultraviolet and X-ray photons from the Sun also break apart molecules in the thermosphere. In the upper thermosphere, atomic oxygen (O), atomic nitrogen (N), and helium (He) are the main components of air.
Much of the X-ray and UV radiation from the Sun is absorbed in the thermosphere. When the Sun is very active and emitting more high energy radiation, the thermosphere gets hotter and expands or "puffs up". Because of this, the height of the top of the thermosphere (the thermopause) varies. The thermopause is found at an altitude between 500 km and 1,000 km or higher. Since many satellites orbit within the thermosphere, changes in the density of (the very, very thin) air at orbital altitudes brought on by heating and expansion of the thermosphere generates a drag force on satellites. Engineers must take this varying drag into account when calculating orbits, and satellites occasionally need to be boosted higher to offset the effects of the drag force.
High-energy solar photons also tear electrons away from gas particles in the thermosphere, creating electrically-charged ions of atoms and molecules. Earth's ionosphere, composed of several regions of such ionized particles in the atmosphere, overlaps with and shares the same space with the electrically neutral thermosphere.
Like the oceans, Earth's atmosphere has waves and tides within it. These waves and tides help move energy around within the atmosphere, including the thermosphere. Winds and the overall circulation in the thermosphere are largely driven by these tides and waves. Moving ions, dragged along by collisions with the electrically neutral gases, produce powerful electrical currents in some parts of the thermosphere.
Finally, the aurora (the Southern and Northern Lights) primarily occur in the thermosphere. Charged particles (electrons, protons, and other ions) from space collide with atoms and molecules in the thermosphere at high latitudes, exciting them into higher energy states. Those atoms and molecules shed this excess energy by emitting photons of light, which we see as colorful auroral displays. | 0.819144 | 4.019188 |
A long time ago, in a nebula that no longer exists, our newborn planet was hit with a giant impact so energetic that it melted part of the planet and the impactor and created a spinning molten glob. That whirling disk of hot melted rock was turning so fast that from the outside it would have been difficult to tell the difference between the planet and the disk. This object is called a “synestia” and understanding how it formed may lead to new insights into the process of planetary formation. The synestia phase of a planet’s birth sounds like something out of weird science fiction movie, but it may be a natural step in the formation of worlds. It very likely happened several times during the birth process for most of the planets in our solar system, particularly the rocky worlds of Mercury, Venus, Earth, and Mars. It’s all part of a process called “accretion”, where smaller chunks of rock in a planetary birth créche called a protoplanetary disk slammed together to make bigger objects called planetesimals. The planetesimals crashed together to make planets. The impacts release huge amounts of energy, which translates into enough heat to melt rocks. As the worlds got larger, their gravity helped hold them together and eventually played a role in “rounding” their shapes. Smaller worlds (such as moons) can also form the same way. | 0.859424 | 3.305241 |
X-rays Spot Spinning Black Holes Across Cosmic Sea
Credit: NASA/CXC/Univ. of Oklahoma/X. Dai et al.
Like whirlpools in the ocean, spinning black holes in space create a swirling torrent around them. However, black holes do not create eddies of wind or water. Rather, they generate disks of gas and dust heated to hundreds of millions of degrees that glow in X-ray light.
Using data from NASA's Chandra X-ray Observatory and chance alignments across billions of light years, astronomers have deployed a new technique to measure the spin of five supermassive black holes. The matter in one of these cosmic vortices is swirling around its black hole at greater than about 70% of the speed of light.
The astronomers took advantage of a natural phenomenon called a gravitational lens. With just the right alignment, the bending of space-time by a massive object, such as a large galaxy, can magnify and produce multiple images of a distant object, as predicted by Einstein.
In this latest research, astronomers used Chandra and gravitational lensing to study five quasars, each consisting of a supermassive black hole rapidly consuming matter from a surrounding accretion disk. Gravitational lensing of the light from each of these quasars by an intervening galaxy has created multiple images of each quasar, as shown by these Chandra images of four of the targets. The sharp imaging ability of Chandra is needed to separate the multiple, lensed images of each quasar.
The key advance made by researchers in this study was that they took advantage of "microlensing," where individual stars in the intervening, lensing galaxy provided additional magnification of the light from the quasar. A higher magnification means a smaller region is producing the X-ray emission.
The researchers then used the property that a spinning black hole is dragging space around with it and allows matter to orbit closer to the black hole than is possible for a non-spinning black hole. Therefore, a smaller emitting region corresponding to a tight orbit generally implies a more rapidly spinning black hole. The authors concluded from their microlensing analysis that the X-rays come from such a small region that the black holes must be spinning rapidly.
The results showed that one of the black holes, in the lensed quasar called the "Einstein Cross," (labeled Q2237 in the image above) is spinning at, or almost at, the maximum rate possible. This corresponds to the event horizon, the black hole's point of no return, spinning at the speed of light, which is about 670 million miles per hour. Four other black holes in the sample are spinning, on average, at about half this maximum rate.
For the Einstein Cross the X-ray emission is from a part of the disk that is less than about 2.5 times the size of the event horizon, and for the other 4 quasars the X-rays come from a region four to five times the size of the event horizon.
How can these black holes spin so quickly? The researchers think that these supermassive black holes likely grew by accumulating most of their material over billions of years from an accretion disk spinning with a similar orientation and direction of spin, rather than from random directions. Like a merry-go-round that keeps getting pushed in the same direction, the black holes kept picking up speed.
The X-rays detected by Chandra are produced when the accretion disk surrounding the black hole creates a multimillion-degree cloud, or corona above the disk near the black hole. X-rays from this corona reflect off the inner edge of the accretion disk, and the strong gravitational forces near the black hole distort the reflected X-ray spectrum, that is, the amount of X-rays seen at different energies. The large distortions seen in the X-ray spectra of the quasars studied here imply that the inner edge of the disk must be close to the black holes, giving further evidence that they must be spinning rapidly.
The quasars are located at distances ranging from 9.8 billion to 10.9 billion light years from Earth, and the black holes have masses between 160 and 500 million times that of the sun. These observations were the longest ever made with Chandra of gravitationally lensed quasars, with total exposure times ranging between 1.7 and 5.4 days.
A paper describing these results is published in the July 2nd issue of The Astrophysical Journal, and is available online. The authors are Xinyu Dai, Shaun Steele and Eduardo Guerras from the University of Oklahoma in Norman, Oklahoma, Christopher Morgan from the United States Naval Academy in Annapolis, Maryland, and Bin Chen from Florida State University in Tallahassee, Florida.
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A sun-like star seems to have devoured some of its own planetary offspring, prompting researchers to nickname it after the titan Kronos from Greek mythology.
The star HD 240430 is part of a binary system with HD 240429, and the two have now been nicknamed Kronos and Krios. The pair travel through the galaxy side by side some 320 light years from Earth.
They both seem to be about 4 billion years old, suggesting they were born from the same interstellar cloud, and initially shared the same chemical make-up.
But an analysis by Semyeong Oh at Princeton University and her team suggests the twins have led very different lives. Krios has noticeably smaller concentrations of elements like lithium, magnesium and iron floating in its atmosphere than its companion Kronos does.
In fact, the stars are more chemically different than any pair yet discovered. “I initially thought these two stars must not be in a binary,” says Oh.
Separated after birth
Perhaps they weren’t born together and hooked up later in life. Maybe the cloud they came from endowed them with different concentrations of elements.
But Oh and her team argue that Kronos has devoured several orbiting rocky planets throughout its life. Hence why they are calling the star Kronos, after the titan of Greek mythology who devoured his own children, fearing they would overthrow him.
By contrast, the team refer to HD 240429 as Krios, a rather more anonymous titan who was Kronos’s brother.
Oh’s team calculate that it would take the chemical elements from 15 Earth masses crushed up and scattered throughout Kronos’s roiling atmosphere to explain the star’s blend of excess elements.
“I was really excited when I saw this,” says Johanna Teske at the Carnegie Observatories in Pasadena, California, who has looked at similar pairs to see if stars known to host planets have different chemical compositions to those without the hangers-on. “A lot of those signatures were very small,” she said. “This is a huge signature.”
How the star would eat its planets isn’t clear, though. Perhaps another star flew past, disrupting the orbits of outer planets around Kronos, which then distorted the paths of inner worlds and sent them careening into their star.
The Krios system, two light years away, might have escaped unscathed, however.
If this did happen to Kronos, any remaining outer giant planets around it might have stretched-out orbits, suggesting they participated in the same cataclysm that led to the demise of their siblings. To test this, the team has begun looking for giant planets around both Kronos and Krios.
The group hasn’t found any such worlds yet – but the ongoing European Space Agency’s Gaia mission should have good chance of turning them up as it releases more data.
More on these topics: | 0.859791 | 3.884502 |
Astronomers from the European Southern Observatory (ESO) and other institutes have discovered a new stellar black hole, and it’s practically in our backyard. Researchers say the black hole is just 1,000 light-years away from Earth — closer to our solar system than any other found to date. 1,000 light-years may seem far away, but on a cosmic scale, it’s incredibly close. In comparison, Sagittarius A*, the infamous supermassive black hole at the center of the Milky Way, is more than 25,000 light-years away, while the size of the Milky Way stretches more than 100,000 light-years across. This black hole forms part of a triple system that can be seen with the naked eye. The team found evidence for the invisible object by tracking its two companion stars using the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. They say this system could just be the tip of the iceberg, as many more similar black holes could be found in the future.
“We were totally surprised when we realised that this is the first stellar system with a black hole that can be seen with the unaided eye,” says Petr Hadrava, Emeritus Scientist at the Academy of Sciences of the Czech Republic in Prague and co-author of the research. Located in the constellation of Telescopium, the system is so close to us that its stars can be viewed from the southern hemisphere on a dark, clear night without binoculars or a telescope. “This system contains the nearest black hole to Earth that we know of,” says ESO scientist Thomas Rivinius, who led the study published today in Astronomy & Astrophysics.
The team originally observed the system, called HR 6819, as part of a study of double-star systems. However, as they analysed their observations, they were stunned when they revealed a third, previously undiscovered body in HR 6819: a black hole. The observations with the FEROS spectrograph on the MPG/ESO 2.2-metre telescope at La Silla showed that one of the two visible stars orbits an unseen object every 40 days, while the second star is at a large distance from this inner pair.
Dietrich Baade, Emeritus Astronomer at ESO in Garching and co-author of the study, says: “The observations needed to determine the period of 40 days had to be spread over several months. This was only possible thanks to ESO’s pioneering service-observing scheme under which observations are made by ESO staff on behalf of the scientists needing them.”
The hidden black hole in HR 6819 is one of the very first stellar-mass black holes found that do not interact violently with their environment and, therefore, appear truly black. But the team could spot its presence and calculate its mass by studying the orbit of the star in the inner pair. “An invisible object with a mass at least 4 times that of the Sun can only be a black hole,” concludes Rivinius, who is based in Chile.
Astronomers have spotted only a couple of dozen black holes in our galaxy to date, nearly all of which strongly interact with their environment and make their presence known by releasing powerful X-rays in this interaction. But scientists estimate that, over the Milky Way’s lifetime, many more stars collapsed into black holes as they ended their lives. The discovery of a silent, invisible black hole in HR 6819 provides clues about where the many hidden black holes in the Milky Way might be. “There must be hundreds of millions of black holes out there, but we know about only very few. Knowing what to look for should put us in a better position to find them,” says Rivinius. Baade adds that finding a black hole in a triple system so close by indicates that we are seeing just “the tip of an exciting iceberg.”
This research led by Th. Rivinius was presented in the paper “A naked-eye triple system with a nonaccreting black hole in the inner binary”, published in May 6 2020 in the journal Astronomy & Astrophysics (doi: 10.1051/0004-6361/202038020).
Source: ESO, cbsnews
Cover image:Artist’s impression of the triple system with the closest black hole. Credits: ESO | 0.902158 | 3.905374 |
Science, Tech, Math › Science Understanding Star Patterns and Constellations How Identifying Star Patterns Paved the Way for Modern Astronomy Share Flipboard Email Print ThoughtCo / Carolyn Collins Petersen Science Astronomy An Introduction to Astronomy Important Astronomers Solar System Stars, Planets, and Galaxies Space Exploration Chemistry Biology Physics Geology Weather & Climate By Nick Greene Astronomy Expert Nick Greene is a software engineer for the U.S. Navy Space and Naval Warfare Engineering Center. He is also the U.N. World Space Week Coordinator for Antarctica. our editorial process Nick Greene Updated January 21, 2020 Observing the night sky is one of the oldest pastimes in human culture. It likely goes back to the earliest people, who used the sky for navigation; they noticed the backdrop of stars and charted how they changed over the year. In time, they began to tell tales about them, using the familiar look of some patterns to tell of gods, goddesses, heroes, princesses, and fantastic beasts. The Start of Astronomy In earlier times, telling stories was the most common form of entertainment, and the star patterns in the sky provided worthy inspiration. People also used the sky as a calendar once they noticed a correlation between the stars in the sky and different times of the year, like changing seasons. That led them to build observatories and temples that guided ritualistic skygazing. These storytelling and viewing activities were the start of astronomy as we know it. It was a simple beginning: People noticed the stars in the sky and named them. Then, they noticed patterns amongst the stars. They also saw objects moving across the backdrop of stars from night to night and called them "wanderers"—we now know them as planets. Of course, the science of astronomy grew over the centuries as technology advanced and scientists could define the objects in the sky they were seeing. However, even today, astronomers at all levels use some of the star patterns that were identified by the ancients; they provide a way to "map" the sky into regions. Brian Bumby / Getty Images The Birth of the Constellations Ancient humans got creative with the star patterns they observed. They played cosmic "connect the dots" to establish patterns that looked like animals, gods, goddesses, and heroes, creating constellations. They also created stories to go along with these star patterns, which became the basis for many of the myths that have passed through centuries by the Greeks, Romans, Polynesians, Native Americans, and members of various African tribes and Asian cultures. For example, the constellation Orion inspired an important figure in Greek mythology. Most of the names we use for constellations today come from ancient Greece or the Middle East, a legacy of the advanced learning of those cultures. But those terms are widespread. For instance, the names "Ursa Major" and "Ursa Minor"—the Big Bear and the Little Bear—have been used to identify those stars by different populations around the world since the Ice Ages. A star chart showing three easy-to-spot constellations in April. ThoughtCo / Carolyn Collins Petersen Constellation Use for Navigation Constellations played a significant role in navigation for explorers of the earth's surface and oceans; these navigators created extensive star charts to help them find their way around the planet. Often though, a single star chart wasn't enough for successful navigation. The visibility of constellations can differ between the Northern and Southern Hemispheres, so travelers found themselves having to learn whole new sets of constellations when venturing north or south of their home skies. A star chart view of Alpha Centauri with the Southern Cross for reference. ThoughtCo / Carolyn Collins Petersen Constellations Versus Asterisms Most people are familiar with the Big Dipper, but that seven-star pattern is not technically a constellation. Rather, it is an asterism—a prominent star pattern or group of stars that is smaller than a constellation. It can be considered a landmark. The star pattern that makes up the Big Dipper is technically part of the aforementioned constellation Ursa Major. Likewise, the nearby Little Dipper is a part of the constellation Ursa Minor. This does not mean that all landmarks are not constellations, though. The Southern Cross—our popular landmark for the south that appears to point toward the earth's South Pole—is a constellation. Use the Big Dipper to help you find two other stars in the sky. ThoughtCo / Carolyn Collins Petersen Constellations Visible to You There are 88 official constellations in the Northern and Southern Hemispheres of our sky. Most people can see more than half of them throughout the year, though it can depend on where they live. The best way to learn them all is to observe throughout the year and study the individual stars in each constellation. To identify the constellations, most observers use star charts, which can be found online and in astronomy books. Others use planetarium software such as Stellarium or an astronomy app. There are many such tools available that will help observers make useful star charts for their observing enjoyment. A star chart showing the southern cross and a nearby star cluster. ThoughtCo / Carolyn Collins Petersen Fast Facts Constellations are groupings of stars into familiar-looking figures.There are 88 officially recognized constellations.Many cultures developed their own constellation figures.Stars in constellations are not usually close to one another. Their arrangement is a trick of perspective from our point of view on earth. Sources “International Astronomical Union.” IAU, www.iau.org/public/themes/constellations/.“The 88 Constellations of the Night Sky.” The Taurus Constellation | Learning the Night Sky, Go Astronomy, www.go-astronomy.com/constellations.htm. "What are Constellations." www.astro.wisc.edu/~dolan/constellations/extra/constellations.html. Edited and updated by Carolyn Collins Petersen. | 0.823507 | 3.463907 |
Far-off planetary worlds may sustain life
Life could exist in the atmospheres of brown dwarfs and gas giants, research suggests.
A study from the Centre for Exoplanet Science shows the potential for habitable environments in the atmospheres of brown dwarfs and planets with inhospitable lower atmospheres or surfaces, using a theoretical model of an organism.
Our study of hypothetical small, simple life forms on a cool brown dwarf – an object larger than a planet and smaller than a star – suggests that they could adapt to survive in such habitats. The organisms could evolve to cope in the gravity, temperature and wind conditions in such environments, where water and nutrients may also be found.
We suggest that such life forms could survive on planets whose surface or lower atmosphere is too hot, cold, dry or dense to support life. In addition, some cool brown dwarfs are free-floating - that is, they don't orbit a star - which challenges the traditional view of habitability of a terrestrial planet orbiting a Sun-like star. In light of the finding, scientists may have previously underestimated how much of the universe is potentially habitable.
This would include the possibility of habitable atmospheres in gas giants like Jupiter, Saturn, Uranus and Neptune. Beyond our solar system, billions of such worlds at the distant reaches of our galaxy may have such habitable zones. The closest of these atmospheric habitable zones could be less than 30 light years away, which may be within the reach of powerful astronomy telescopes likely to be developed in the next decade. This would enable scientists to search for signs of life in distant worlds.
However, although these calculations show the potential for habitable conditions, they say nothing about whether or not these bodies are actually inhabited, or how life could arise in an atmosphere.
The study was the first to be published by the Centre for Exoplanet Science. It appears some 40 years after some of the ideas behind the study were published in the same journal by pioneering scientist Carl Sagan. | 0.916207 | 3.569819 |
A distant cosmic relative to the first source that astronomers detected in both gravitational waves and light may have been discovered, as reported in our latest press release. This object, called GRB 150101B, was first detected by identified as a gamma ray burst (GRB) by NASA's Fermi Gamma-ray Space Telescope in January 2015.
This image shows data from NASA’s Chandra X-ray Observatory (purple in the inset boxes) in context with an optical image of GRB 150101B from the Hubble Space Telescope.
The detection and follow-up observations with Chandra, Hubble, the Discovery Channel Telescope, the Neil Gehrels Swift Observatory, and other telescopes show GRB 150101B shares remarkable similarities to the neutron star merger and gravitational wave source discovered by Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) and its European counterpart Virgo in 2017 known as GW170817. In this view of GRB 150101B and its host galaxy, the Chandra field of view is outlined as a box on an optical and infrared image from the Hubble Space Telescope. Chandra images are included from two different times (labeled in the insets) to show how the X-ray source faded with time.
The latest study concludes that these two separate objects may, in fact, be related. The discovery suggests that events like GW170817 and GRB 150101B could represent a whole new class of erupting objects that turn on and off in X-rays and might actually be relatively common.
The researchers think both GRB 150101B and GW170817 were most likely produced by the same type of event: the merger of two neutron stars, a catastrophic coalescence that generated a narrow jet, or beam, of high-energy particles. The jet produced a short, intense burst of gamma rays (known as a short GRB), a high-energy flash that can last only seconds. GW170817 proved that these events may also create ripples in space-time itself called gravitational waves.
While there are many commonalities between GRB 150101B and GW170817, there are two very important differences. One is their location. GW170817 is about 130 million light years from Earth, while GRB 150101B lies about 1.7 billion light years away. Even if Advanced LIGO had been operating in early 2015, it would very likely not have detected gravitational waves from GRB 150101B because of its greater distance.
It is possible that a few mergers like the ones seen in GW170817 and GRB 150101B had been detected as short GRBs before but had not been identified with other telescopes. Without detections at longer wavelengths like X-rays or optical light, GRB positions are not accurate enough to determine what galaxy they are located in.
In the case of GRB 150101B, astronomers thought at first that the counterpart was an X-ray source detected by Swift in the center of the galaxy, likely from material falling into a supermassive black hole. However, follow-up observations with Chandra, with its sharp X-ray resolution, detected the true counterpart away from the center of the host galaxy. This can be seen in the Chandra images. Not only has the source dimmed dramatically, it is clearly outside the center of the galaxy, which appears as the constant brighter source to the upper right.
A paper describing this result by Eleonora Troja (Goddard Space Flight Center and the University of Maryland at College Park) and colleagues appears in the October 16, 2018, issue of the journal Nature Communications and is available online. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations. | 0.877731 | 4.044005 |
Pasadena, CA— A team of astronomers including Carnegie’s Eduardo Bañados and led by Roberto Decarli of the Max Planck Institute for Astronomy has discovered a new kind of galaxy which, although extremely old—formed less than a billion years after the Big Bang—creates stars more than a hundred times faster than our own Milky Way.
Their findings are published by Nature.
The team’s discovery could help solve a cosmic puzzle—a mysterious population of surprisingly massive galaxies from when the universe was only about 10 percent of its current age.
After first observing these galaxies a few years ago, astronomers proposed that they must have been created from hyper-productive precursor galaxies, which is the only way so many stars could have formed so quickly. But astronomers had never seen anything that fit the bill for these precursors until now.
This newly discovered population could solve the mystery of how these extremely large galaxies came to have hundreds of billions of stars in them when they formed only 1.5 billion years after the Big Bang, requiring very rapid star formation.
The team made this discovery by accident when investigating quasars, which are supermassive black holes that sit at the center of enormous galaxies, accreting matter. They were trying to study star formation in the galaxies that host these quasars.
"But what we found, in four separate cases, were neighboring galaxies that were forming stars at a furious pace, producing a hundred solar masses' worth of new stars per year," Decarli explained.
"Very likely it is not a coincidence to find these productive galaxies close to bright quasars. Quasars are thought to form in regions of the universe where the large-scale density of matter is much higher than average. Those same conditions should also be conducive to galaxies forming new stars at a greatly increased rate," added Fabian Walter, also of Max Planck.
“Whether or not the fast-growing galaxies we discovered are indeed precursors of the massive galaxies first seen a few years back will require more work to see how common they actually are,” Bañados explained.
Decarli’s team already has follow-up investigations planned to explore this question.
The team also found what appears to be the earliest known example of two galaxies undergoing a merger, which is another major mechanism of galaxy growth. The new observations provide the first direct evidence that such mergers have been taking place even at the earliest stages of galaxy evolution, less than a billion years after the Big Bang.
Other members of the research team are: Bram Venemans, Emanuele Farina, Chiara Mazzucchelli, and Hans-Walter Rix of Max Planck Institute for Astronomy; Frank Bertoldi of the University of Bonn; Chris Carilli of the National Radio Astronomy Observatory and Cambridge University; Xiaohui Fan of University of Arizona; Dominik Riechers of Cornell University, Michael A. Strauss of Princeton University, Ran Wang of Peking University), and Y. Yang of the Korea Astronomy and Space Science Institute.
The MPIA release for this paper is available here.
Caption: An artist's impression of a quasar and neighboring merging galaxy. The galaxies observed by the team are so distant that no detailed images are possible at present. This combination of images of nearby counterparts gives an impression of how they might look in more detail. The image was created by the Max Planck Institute for Astronomy using material from the NASA/ESA Hubble Space Telescope.
The researchers were supported by the DFG priority programme 1573 “The physics of the interstellar medium,” ERC grant COSMIC-DAWN, the National Science Foundation of China, the National Key Program for Science and Technology Research and Development, and a Carnegie-Princeton fellowship.
The discoveries were made at ALMA Observatory, which is a partnership of the ESO, NSF, and NINS, together with the NRC, NSC, ASIAA, and KAS, in cooperation with Chile. | 0.899857 | 4.050368 |
PASADENA, Calif. -- NASA's Dawn spacecraft on Saturday became the first probe ever to enter orbit around an object in the main asteroid belt between Mars and Jupiter.
Dawn will study the asteroid, named Vesta, for a year before departing for a second destination, a dwarf planet named Ceres, in July 2012. Observations will provide unprecedented data to help scientists understand the earliest chapter of our solar system. The data also will help pave the way for future human space missions.
"Today, we celebrate an incredible exploration milestone as a spacecraft enters orbit around an object in the main asteroid belt for the first time," NASA Administrator Charles Bolden said. "Dawn's study of the asteroid Vesta marks a major scientific accomplishment and also points the way to the future destinations where people will travel in the coming years. President Obama has directed NASA to send astronauts to an asteroid by 2025, and Dawn is gathering crucial data that will inform that mission."
The spacecraft relayed information to confirm it entered Vesta's orbit, but the precise time this milestone occurred is unknown at this time. The time of Dawn's capture depended on Vesta's mass and gravity, which only has been estimated until now. The asteroid's mass determines the strength of its gravitational pull. If Vesta is more massive, its gravity is stronger, meaning it pulled Dawn into orbit sooner. If the asteroid is less massive, its gravity is weaker and it would have taken the spacecraft longer to achieve orbit. With Dawn now in orbit, the science team can take more accurate measurements of Vesta's gravity and gather more accurate timeline information.
Dawn, which launched in September 2007, is on track to become the first spacecraft to orbit two solar system destinations beyond Earth. The mission to Vesta and Ceres is managed by NASA's Jet Propulsion Laboratory in Pasadena, Calif., for the agency's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, which is managed by NASA's Marshall Space Flight Center in Huntsville, Ala.
The University of California, Los Angeles, is responsible for the overall Dawn mission science. Orbital Sciences Corp. of Dulles, Va., designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are part of the mission's team. JPL is a division of the California Institute of Technology in Pasadena.
To follow the mission on Twitter, visit: http://www.twitter.com/NASA_Dawn .
News Media ContactPriscilla Vega 818-354-1357
Jet Propulsion Laboratory, Pasadena, Calif.
Dwayne C. Brown 202-358-1726
NASA Headquarters, Washington | 0.862153 | 3.179445 |
The Chang’e-4 mission, the fourth installment in the Chinese Lunar Exploration Program, has made some significant achievements since it launched in December of 2018. In January of 2019, the mission lander and its Yutu 2 (Jade Rabbit 2) rover became the first robotic explorers to achieve a soft landing on the far side of the Moon. Around the same time, it became the first mission to grow plants on the Moon (with mixed results).
In the latest development, the Netherlands-China Low Frequency Explorer (NCLE) commenced operations after a year of orbiting the Moon. This instrument was mounted on the Queqiao communications satellite and consists of three 5-meter (16.4 ft) long monopole antennas that are sensitive to radio frequencies in the 80 kHz – 80 MHz range. With this instrument now active, Chang’e-4 has now entered into the next phase of its mission.
The radio observatory is the result of collaboration between the Netherlands Institute for Radio Astronomy (ASTRON) and the China National Space Agency (CNSA). ASTRON has a long history of conducting radio astronomy, which includes the operation of one of the largest radio telescopes in the world – the Westerbork Synthesis Radio Telescope (WSRT), which is also part of the European Very Long Baseline Interferometry Network (EVN).
The NCLE is the first observatory built by the Netherlands and China to conduct radio astronomy experiments while orbiting on the far side of the Moon. This location is considered ideal for such experiments since it is removed from any terrestrial radio interference. It is for this reason that Queqiao has had to act as a communications relay with the Chang’e-4 mission since radio signals cannot reach the far side of the Moon directly.
While the NCLE is capable of mounting multiple forms of scientific research, its main purpose is to conduct groundbreaking experiments in radio astronomy. Particularly, the NCLE will gather data in the 21-cm (8.25 inch) emission range, which corresponds with the earliest periods in cosmic history.
These are otherwise known as the Dark Ages and Cosmic Dawn, which have previously been inaccessible to astronomers. By examining light from the earliest periods of the Universe, astronomers will finally be able to answer some of the most enduring questions about the Universe. These include when the first stars and galaxies formed, as well as the influence of Dark Matter and Dark Energy on cosmic evolution.
Until now, the Queqiao satellite was primarily a communications relay between the lander and rover and mission controllers on Earth. But with the primary goals of the Chang’e-4 mission now achieved, the China National Space Agency (CNSA) has entered into the next phase of operations, which is to operate a radio observatory on the far side of the Moon.
“Our contribution to the Chinese Chang’e 4 mission has now increased tremendously. We have the opportunity to perform our observations during the fourteen-day-long night behind the moon, which is much longer than was originally the idea. The moon night is ours, now.“
The unfolding of the antennas is the culmination of three years of hard work and the demonstration of this technology is expected to pave the way for new opportunities for radio instruments in space. In addition to scientists with ASTRON and the CNSA, there is no shortage of people around the world who are eagerly awaiting the NCLE’s first radio measurements.
Professor Heino Falcke, the chair of astrophysics and radio astronomy at Radboud University, is also the scientific leader of the Dutch-Chinese radio telescope. As he explained:
“We are finally in business and have a radio-astronomy instrument of Dutch origin in space. The team has worked incredibly hard, and the first data will reveal how well the instrument truly performs.”
The deployment of the instrument was meant to happen sooner and the year-long wait behind the Moon is believed to have had an effect on the antennas. Initially, the antennas unfolded smoothly but the progress became increasingly sluggish as time went on. As a result, the team decided to collect data first from the partially-deployed antennas first and may decide to unfold them further later.
At their current, shorter deployment, the instrument is sensitive to signals from roughly 13 billion years ago – aka. about 800 million years after the Big Bang. Once the antennas are unfolded to their full length, they will be able to capture signals from just after the Big Bang. This will allow astronomers to see the first stars being born and star clusters coming together to form the very first galaxies.
The first light in the Universe and the answers to some of the most profound questions will finally be accessible!
Further Reading: Radboud University
Where do they come from, those beguiling singularities that flummox astrophysicists—and the rest of us.…
Astronomers don’t know exactly when the first stars formed in the Universe because they haven’t…
Our measurements of dark energy give contradictory results. A new study confirms dark energy, but…
There's an unusual paradox hampering research into parts of the Milky Way. Dense gas blocks… | 0.853282 | 3.951562 |
On March 6, 2015 at 7:39 a.m. EST, NASA’s Dawn spacecraft became the first to achieve orbit around a dwarf planet — Ceres. It is also the first mission to orbit two extraterrestrial targets – Ceres and Vesta. Ceres and Vesta are the two most massive bodies of an asteroid belt between Mars and Jupiter.
The spacecraft was launched from Cape Canaveral, Florida on September 27, 2007 and explored Vesta from 2011 to 2012, sending new insights and thousands of images back to Earth.
Dawn discovered that Vesta may have had short-lived water flows on the surface and may now have localized patches of ice below its surface. Scientists are not sure where the water/ice came from. However, they guess that ice-rich bodies like comets, left part of their ice under the surface after impact.
During its time visiting Vesta, Dawn discovered narrow curved gullies that are about 100 feet (30 meters) wide. Their average length is about half a mile (900 meters). The gullies appear different than they would if formed by the flow of purely dry materials. Scientists believe that water debris flows formed the gullies.
“We’re suggesting a process similar to debris flows, when a small amount of water mobilizes the sandy and rocky particles into a flow,” explained Jennifer Scully, postgraduate researcher at the University of California, Los Angeles.
Craters with curvy gullies appear to be less than a few hundred million years old, which is still young compared to Vesta’s age of 4.6 billion years.
Laboratory experiments performed at NASA’s Jet Propulsion Laboratory in Pasadena, California, show that there could have been enough time for the gullies to form before all water evaporated from the surface of Vesta.
Ceres was discovered in 1801 and has been known as a planet, an asteroid, and now a dwarf planet.
As big as Texas, Ceres has a spherical body, like Earth that is denser material at the core and lighter minerals near the surface. Astronomers believe that water ice may be buried under its crust because its density is less than that of Earth’s crust, and because the dust-covered surface includes evidence of water-bearing minerals. It is also possible that the planet has frost-covered polar caps. Water ice is expected to be located in its mantle.
Astronomers guess that if Cere were composed of 25 percent water, it may have more water than all the fresh water on Earth. | 0.818653 | 3.965573 |
ann15061 — Kunngjøring
Powerful New Black Hole Probe Arrives at Paranal
VLTI GRAVITY instrument assembled and tested
11. august 2015
A new instrument called GRAVITY has been shipped to Chile and successfully assembled and tested at the Paranal Observatory.
GRAVITY is a second generation instrument for the VLT Interferometer (VLTI). It will allow the measurement of the positions of astronomical objects on the finest scales and perform interferometric imaging and spectroscopy. GRAVITY will bring the most advanced vision to the VLT, combining four individual telescopes of the Paranal Observatory so that they effectively act as a single telescope with a diameter of more than 100 metres.
Using several novel techniques, GRAVITY will offer sensitivity and accuracy far beyond what is possible today . It aims to measure the positions of objects on scales of order ten microarcseconds, and perform imaging with four milliarcsecond resolution. For illustration, this corresponds to seeing buildings on the Moon, and locating them to within a few centimetres.
GRAVITY will push high angular resolution astronomy to new limits: it will probe physics close to the event horizon of the supermassive black hole at the Galactic Centre — a region which is dominated by effects predicted by Einstein's theory of general relativity. In addition, it will uncover the details of mass accretion and jets — processes that occur both in young stellar objects and in the active nuclei of other galaxies. It will also excel at probing the motions of binary stars, exoplanets and young stellar discs, and in imaging the surfaces of stars.
On 21 July 2015 the team saw “first laboratory fringes” from GRAVITY in the Paranal integration hall using a test light source. Following further tests of the GRAVITY instrument and the preparation of the VLT interferometer, GRAVITY will be moved to the VLTI later this year to see “first star fringes” using the four 1.8-metre Auxiliary Telescopes starting in November 2015. The commissioning of GRAVITY with the four 8-metre VLT Unit Telescopes is foreseen for the first half of 2016.
GRAVITY's development was led by the Max Planck Institute for Extraterrestrial Physics, in Garching, Germany and involves six institutes across Europe , as well as ESO.
GRAVITY features fibre-fed integrated optics beam combiners, infrared wavefront sensors for adaptive optics, fringe tracking, active beam stabilisation, and a novel metrology concept.
The partner institutes in the GRAVITY Consortium are:
- Max Planck Institute for Extraterrestrial Physics, Garching, Germany
- LESIA, Observatoire de Paris, Université Paris Diderot, Meudon, France
- Max Planck Institute for Astronomy, Heidelberg, Germany
- University of Cologne, Cologne, Germany
- Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), Grenoble, France
- Laboratório de Sistemas, Instrumentação e Modelação em Ciências e Tecnologias do Ambiente e do Espaço (SIM), Lisbon and Porto, Portugal
- ESO, Garching, Germany
ESO, Garching, Germany
Max Planck Institute for Extraterrestrial Physics, Garching, Germany
ESO Public Information Officer
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591 | 0.842015 | 3.614432 |
The European Space Agency is gearing up to land its lander which goes by the name Philae, on a comet come Nov. 11. The lander is currently riding on the Rosetta Spacecraft, and at the moment; the space agency is still pondering on where to make the landing.
However, the European Space Agency recently revealed that it aims to release the planned landing areas on Sept. 15, and if everything goes well, the landing will be made on Nov. 11. Bear in mind that anything can change by now until then, so the date could be pushed back without warning.
The comet in question is called Comet 67P or Churyumov-Gerasimenko, and the landing will mark the first time that any space agency in the world has ever attempted a soft landing on a comet. The last time we heard of a probe landing on a comet was when NASA crashed its Deep Impact spacecraft into a comet back in 2005.
For the past eight months, the Rosetta spacecraft has spent a lot of time near Comet 67P/Churyumov-Gerasimenko as it allowed the European Space Agency to study the comet. Scientists are interested in the comet’s strange composition, as its shape is similar to that of a duck, and it has two distinct sides to it.
We’ve come to understand that investigators have located five possible landing site candidates on the comet. Most of them are located on the smallest section of the two lobes. However, it is not yet certain if any of these sections will be used for landing, as the agency requires more time to figure out if these areas are safe enough.
Time is running out though, as Sept. 15 is only days away; and before that, Nov. 11 is right before our eyes.
We understand that once Philae lands on the surface of the comet, it will work for just a few weeks. Rosetta will be nearby feeding transmission to Philae; this will be done until August 2015.
The main goal here is to find out how comets are seen as the building blocks of the solar system, and Earth itself. Furthermore, scientists want to know how comets react as they venture closer to the sun, though we are not sure for what purpose this information is needed.
The Rosetta spacecraft was launched ten years ago by the European Space Agency to get close to Comet 67P/Churyumov-Gerasimenko. The spacecraft has traveled over 4 billion miles to reach its destination, and now that it is there, the agency doesn’t have room for an overabundance of mistakes. | 0.81473 | 3.396335 |
1998: On 8 April 1998, ESA's Infrared Space Observatory (ISO) ended its observational phase.
Astronomers had been able to use ISO for more than 28 months (instead of the planned 18 months) and, as a result, gathered a wealth of additional information about the Universe. Altogether ISO made over 26 000 observations of cosmic objects.
At 07:00 CET on 8 April 1998, engineers at ESA's ground station at Villafranca near Madrid reported that ISO's telescope was beginning to warm up, above its nominal operating temperature close to absolute zero. This was the sign that ISO had exhausted the superfluid helium used to achieve the very low temperatures necessary for infrared astronomy. Observations ceased at 23:07 when the temperature of the instruments had risen above -269°C. At that time, ISO was observing the galaxy NGC 1808 with the camera (ISOCAM) for Prof. J. Hough (UK). The astronomers then handed ISO over to the engineering team for check-outs and decommissioning.
Infrared rays come from cool places in the sky, and ISO would have been dazzled by its own heat unless its optical system were extremely cold. At its launch in November 1995, ISO carried a supply of 2000 litres of superfluid helium, which boils at -271°C. Slow venting of the helium into space maintained the low temperature of the optical system.
1947: On 8 April 1947, the largest sunspot ever observed was seen. It covered 6% of the Sun's visible disk.
648 B.C.: On 6 April 648 B.C., the earliest total solar eclipse chronicled by Greeks was observed. | 0.902825 | 3.385476 |
Sometimes in science, you need to go after the longshots and gamble on something so not likely it feels ridiculous to buy it, since the reward would be so big if it worked. This is why the Robert C. Byrd Green Bank Telescope will be hanging around analyzing the very first recognized interstellar visitor to the Solar System, simply in case it is an alien spacecraft.
Back in late October, the PANSTARRS 1 telescope in Hawaii identified exactly what was at first believed to be a comet, called C/2017 U1. As the orbit was outlined it ended up being clear that it might not have actually stemmed within the Solar System, and need to rather have actually formed around another star. More research studies exposed no trace of a cometary coma, making it an asteroid.
Even then lots of people were advised of the early phases of the timeless unique Rendezvous With Rama. In the book, the rapid item ends up being an alien spaceship, which the team of the one appropriately located human spacecraft gets to check out. We do not have the innovation for that right now, however are using exactly what we have.
Further observations increased the parallels. Oumuamua, as the item is called, is remarkably lengthened — undoubtedly its 10-to-1 ratio of length to width is extraordinary for an asteroid — however would make good sense for spacecraft created to decrease friction with interstellar dust.
Still, the possibilities of this being an alien production are, well, huge. Harvard’s Professor Avi Loeb informed IFLScience the orbit revealed no indications of manoevering, as a spacecraft might. Simply in case the most significant science story of the century is presently passing by, the Breakthrough Listen task has revealed 10 hours of important time on a big radio telescope will be committed to browsing for signals at frequencies of 1-12 GigaHertz. Observations will begin at 3pm ET on December 13 (8pm GMT). Loeb observation that, in spite of a lot of optical observations, just low-sensitivity measurements have actually been made with radio telescopes, influenced Breakthrough Listen’ efforts.
Oumuamua is taking a trip so quick it’s currently two times the Earth-Sun range far from us, which is making observations utilizing telescopes that run at noticeable wavelengths progressively hard. Andrew Siemion of Berkeley SETI Research Center kept in mind it is still less than 2 percent of the range to Voyager, and we can find signals from there really well. If there are any radio emissions in the ideal wavelengths, the Byrd telescope need to choose them up.
Even in the most likely occasion that no indications of alien activity are discovered, there is constantly the opportunity of some other clinically important outcome. It’s concurred there is something uncommon about this things next to its orbit, even if a lot of aren’t ready to sign on to theories like Oumuamua being a swelling of dark matter . The more frequencies at which we study it, the most likely we are to discover responses, such as the possibility the Byrd telescope will find the existence of ice we have actually up until now missed out on. | 0.908043 | 3.751702 |
Main image: Does looking for life mean finding another Earth? Image credit: Nasa/Ames/JPL-Caltech
For now, the aliens of Star Wars are pure sci-fi, but if there is life on other worlds, we already know where to look. It's only been 20 years since the discovery of 51 Pegasi b, the first-ever exoplanet to be detected – and the first of thousands. Thanks to the Hubble, Spitzer and especially the Kepler Space telescopes, astronomers have hunted down over 4,000 planets orbiting other stars, some of which are Earth-sized, and in the habitable zone of a Sun-like star.
Could they support life? Back in the 1960s, astronomer Frank Drake created an equation to predict the likelihood of alien life, and figured there were at least 10,000 communicating civilizations in our galaxy alone. Given that there are 400 billion stars and at least 100 billion planets in the Milky Way, Drake's estimate is a conservative one if – and it's a big if – life exists at all beyond Planet Earth.
However, do we have to go light years away to find life? Find alien lifeforms on any of the seven other planets or 175 moons of the Solar System, and the conclusion will be simple: life is everywhere. We have no evidence to prove that we're alone or we're not, but either conclusion is profound. All we have is tantalising glimpses, clues and a vast bucket list of places we suspect aliens could exist.
Tabby's Star – an alien megastructure?
Did the Kepler Space telescope find an advanced alien megastructure hanging out in front of a star? The chances are slim, of course, but there's definitely something weird going on in the Tabby star system (officially called KIC 8462852), which periodically dimmed by 20% and more between 2009 and 2013. That's a helluva lot, which has got folks talking about the possibility of an astro-engineering megastructure, such as a Dyson Sphere of solar panels.
Or it could be that an alien society is trying to announce itself. If so, it's working – the SETI (Search for Extraterrestrial Intelligence) Institute has trained its Allen Telescope Array on Tabby's Star to study radio signals. "It's quite likely that this star's strange behaviour is due to nature, not aliens, (but) it's only prudent to check such things out," says SETI Institute astronomer Seth Shostak.
Kepler 3b: clear skies and water vapour
Astronomers are currently using data from three of Nasa's space telescopes – Hubble, Spitzer and Kepler – in their search for Earth-sized planets. Mostly they find 'hot Jupiters' far bigger than Earth, but what about a 'hot Neptune'? About five times the radius of Earth and 122 light years from Earth, Kepler 3b orbits a star called HAT-P-11b (nice work, naming convention committee).
Having originally found it in 2009, NASA had another look last year and discovered that Kepler 3b has a cloud-free atmosphere and, rather stunningly, water vapour. Detecting the latter is highly unusual, so Kepler 3b has to go on the list; where there's water, there's life … probably.
The unexplained Wow! signal
Is it possible that we found aliens back in 1977? While working for SETI at the Big Ear radiotelescope in Delaware, Ohio, astronomer Jerry R. Ehman detected an unexpectedly strong narrowband radio signal from within the constellation of Sagittarius which lasted for 37 seconds, prompting him to write "Wow!' in the data sheet's margin. Then nothing happened – no source for the signal was ever found. Was it an artificially generated radio signal sent by alien civilisation? Or was it simply something from Earth that bounced off space debris?
Gliese 876 – Super-Earths
Since interstellar travel is impossible, the search for alien life must prioritise close exoplanets that could support life – and Gliese 876 has got to be on the shortlist. 'Just' 15.2 light years away in the direction of the constellation of Aquarius, this red dwarf star has the four confirmed closest exoplanets to us: Gliese 876 b, Gliese 876 c, Gliese 876 d and Gliese 876 e.
All are larger than Earth, and orbit their star from about the distance of Mercury, and there's little reason to avoid such Super-Earths if you're serious about alien-hunting, since they appear to be by far the most numerous exoplanets (about 77% of all exoplanets found in the Milky Way so far, although they are easier to find than Earth-sized planets). Besides, planets that size – about six times bigger than Earth – could have habitable moons, which for all we know are the dominant home of extraterrestrial life in the Milky Way.
Enceladus and Titan – the Moon rivers
So why not try out the moons theory? Back in 2013 the orbiting Cassini spacecraft confirmed that Saturn's tiny icy moon, Enceladus, has an underground sea of liquid water. The news has excited scientists because the plumes of ice and water vapour, which were first discovered jetting from fractures at the moon's south pole in 2005, have been revealed to be warm and salty – both are tell-tale signs that there's more water below the surface.
Another moon of Saturn, Titan, is the only other body aside from Earth to have confirmed standing liquid on its surface. There's just one problem: that liquid is ethane and methane, not water. If Titan's seas of liquid methane do contain organisms it would completely change scientific concepts of how life can evolve – and the search parameters would dramatically widen. | 0.890369 | 3.199388 |
It’s no secret that a great deal of Western civilization was informed by the ancient Greeks. They revolutionized mathematics and geometry, developing astronomy along the way. They built ornate statues, beautiful temples to the gods, and amphitheaters for live entertainment with astonishing acoustics. The influence of the ancient Greeks shaped almost every field of human knowledge, from the arts and architecture to politics, philosophy, science, and technology.
Like the Babylonians, the Greeks paid close attention to the night sky. Our nearest celestial neighbor, the Moon, was particularly important to them from a planning perspective. For instance, debts might be due on the new Moon. By heeding the Moon’s phases and taking note of eclipse cycles, they found that their harvests were more fruitful, and they had fewer incidents at sea.
As savvy and well-rounded as ancient Hellenistic culture appears to have been, it’s not unreasonable to imagine that the Greeks could have created some kind of computing machine to make their Moon-centered scheduling easier. Based on fragments from in a shipwreck that was discovered in 1900, it seems they did exactly this. Based on scientific dating of the coins and pottery found in the wreck and inscriptions on the bronze remnants, historians and scientists believe the Greeks created a mechanical computer capable of calculating the positions of the Sun and the Moon on any given day. This marvelous device is known as the Antikythera mechanism.
The mechanism was housed in a wooden box and controlled with a knob on one side. It is believed that the front of the box was a display made up of a set of concentric rings with graduations, and that each ring corresponded with one celestial body. Pointers attached perpendicularly to output gears moved around the rings as the knob was turned, showing the paths and positions of these celestial bodies over time. This Earth-centric planetarium also displayed the phase of the Moon as well as the positions of the five major planets known to the ancient Greeks—Mercury, Venus, Mars, Jupiter, and Saturn.
Provided the scientific dating of the coins and pottery found among the shipwreck is correct, the Antikythera mechanism also marks the earliest appearance of the differential gear. It is believed that the designer used a pin and slot arrangement to join two gears of differing tooth counts in order to model and compensate for the irregular, elliptical orbit of the Moon. Through a complex series of gearing ratios, this ancient computer could predict solar and lunar eclipses, displaying models of them at the user’s fingertips just as they would happen in the sky.
Storms and Shipwrecks
It’s a wonder the Antikythera mechanism was discovered at all. In 1900, a group of Greek sponge divers were sailing back to Symi, an island in the Rhodes region of Southern Greece. Their ship was in a channel north of Crete, near the small island of Antikythera. They became caught in a storm and were forced take shelter around the island’s main port of Potamós. Once the storm passed, they decided to scout the area for sponges before returning home.
The divers didn’t find any sponges off the coast of Antikythera, but they did find treasure. Among the steep rock shelf below laid the remains of a large ship. Scattered among the ancient timbers, partially obscured by rock and silt, the divers could see the disembodied heads, arms, and legs of large bronze and marble statuary. After recovering what they were able to haul, the captain took note of their bearings and the two ships set sail for Symi.
At eight miles square, Antikythera is a fraction the size of Kythera, the island it opposes in the Sea of Crete. Because of its dimensions, location, and low levels of human activity, the island has long been a major stop for migratory birds. Antikythera has seen a lot of fluctuation in usage over the last few thousand years, and the current population is around fifty inhabitants. Because of its staggering cliff faces and craggy shoreline, the tiny island has been a big hazard for all of maritime history.
The sponge divers and crew spent the next six months figuring out what to do about the treasures they had found. Rather than loot the wreckage site, they decided to notify the standing authorities about their discovery. The ship’s captain went to Athens with a bronze arm that his crew had found in the wreck. Almost immediately, the government sanctioned an official recovery mission.
It was agreed that the crew of sponge divers who made the discovery would revisit the site and turn whatever they found over to the Greek government. They ended up recovering the largest collection to date of artifacts from classical antiquity. They brought back scores of treasure from the ancient Hellenistic period, including corroded bronze fragments of something they couldn’t identify. All of the artifacts went to the National Archaeological Museum in Athens.
Believe it or not, the bronze fragments that comprised the Antikythera Mechanism more or less sat around unnoticed at the museum for eight months after the exploration. This was due to the sheer volume of bronze brought into the museum from the wreck. It required a lot of sorting and re-sorting as statues and other pieces were catalogued and reconstructed by the staff. During one of these re-shufflings, someone noticed inscriptions and graduation markings on one of the fragments, and they began to receive attention befitting the oldest known mechanical computer.
Shortly after the exploration of the shipwreck in 1901, it was reported that the fragments of the mysterious object comprised some sort of astrolabe, a type of inclinometer used to locate the positions of celestial bodies. A naval historian named Konstantin Rados contested this theory, arguing that it was too complex of an instrument to be a mere astrolabe. Albert Rehm, a scholar of ancient language and textual interpretation, loosely compared it to the Sphere of Archimedes, a device the ancient Greek mathematician used for computing the volume and surface area of a sphere with relation to those of a cylinder.
Gears from the Greeks
The first in-depth analysis of the Antikythera mechanism was performed by a British science historian and Yale professor named Derek de Solla Price. He began his study of the fragments in the 1950s, using still photographs and radiographs to make sense of the gear ratios. Price’s examination continued unabated into the 1970s. In June of 1974, he published his findings with the American Philosophical Society in a monograph called Gears from the Greeks: The Antikythera Mechanism: A Calendar Computer from Ca. 80 B.C. The 72-page labor of love is Price’s full inquiry into the matter, ranging from the happenstance of the shipwreck’s discovery and early explorations of the mechanism to all that he finds conclusive and inconclusive about its origins, inner workings, meaning, and the shortlist of possible creators.
Price leaves no fragment unexamined, but he was limited by the technologies available at the time. In Gears from the Greeks, he writes that every visible cog was so corroded that not a single one could yield an accurate tooth count. He nevertheless took the task on, working with artist Beverly Pope to create the intricate line drawings you see reprinted here.
Through extensive use of radiography, Price came to the conclusion that the mechanism contained at least 27 gears. It’s now believed that the complete mechanism contained at least 30 gears.
Price was sure that if he could get an accurate count of any of the gears’ teeth, he could begin to unlock the mysteries of the mechanism. This was quite a difficult task to undertake, given that he was working with two-dimensional x-rays of gears that meshed here and overlapped there in a very tight configuration. Undaunted, he literally traced around the gears to count the teeth. Price believed the largest gear was made with 223 or 225 teeth and represented the Sun. He wasn’t sure of this gear’s exact significance, and proposed that a gear representing the eclipse cycle would have 223 teeth, while a gear standing for the Metonic cycle would have 235 teeth.
Price also counted a gear with 127 teeth, and supposed that it could have been used to follow the moon’s movement around the Earth. This number is significant as it is equal to half the number of Moon orbits in a 19-year solar cycle. Scientists believe that the mechanism’s creator did this to simplify the operation, and that a multiplier gear converted the number to 254.
No one had visited the site of the wreck since the initial dredging in 1901. In 1976, an expedition led by Jacques Cousteau recovered many more objects that helped provide clues to the age of the Antikythera mechanism. Among the ship timbers and bronze figures, Cousteau and his team found bronze and silver coins from the Asia Minor colonies of Pergamon and Ephesus, which are now part of Turkey. A coin expert named Panagiotis Tselekas was able to date these coins as having been struck between 70 and 60 BC. Cousteau’s team had also recovered pieces of pottery and many large wine jugs, which experts were able to date to 65-50BC.
All of the available evidence points to the likelihood that the ship was an immense trading vessel belonging to the Roman Empire. At the time, only a few ports in the Mediterranean such as these three were big enough to handle a ship of its enormity, and it was probably sailing from Asia Minor back to Rome. The ship was heavily laden with objects, which many researchers believe that the Romans had looted from Pergamon, Ephesus, and Rhodes.
New Technology, New Findings
Several years later, a mechanical engineer and former curator of London’s Science museum named Michael Wright performed his own extensive study of the Antikythera mechanism over a period of twenty-five years. Wright studied Derek de Solla Price’s monograph and ultimately concluded that Price’s reconstruction of the mechanism was fundamentally incorrect. In fact, Wright went so far as to call it bizarre and incomplete, suggesting that Price took some creative liberties to fill in the gaps, and to make the astronomical calculations work out against his gear tooth counts.
But Michael Wright didn’t just throw stones. In addition to writing numerous papers about the mechanism, he collaborated with Australian computer historian Allan Bromley to create a complete reconstruction of the device in bronze and wood, drawing upon his mechanical knowledge and the history of craft techniques. Wright also took his own photographs of the fragments and performed radiography with a device he created to adapt X-ray equipment for this purpose. Together, they created plans for the model by compiling data from hands-on examination and from their own measurements of the delicate fragments.
The front display of Wright’s model was an Earth-centric planetarium with indicators for the Sun, Moon, and the five major planets of ancient Greek astronomy. In creating his reconstruction, Wright attempted to stay as true to the original as the radiographs would prove. He machined gears from thin bronze that measured between one and two millimeters thick, which he proposed was the kind of stock that all of the metallic parts of the mechanism were made from.
A few years later, an international team of scientists with access to much better imaging technology confirmed that the largest gear did indeed bear 223 teeth. This particular gear was crucial to reconciling the 12-month solar year with the 29.5-day lunar month—a cycle of 19 solar years exactly equals 235 lunar months. This number 235, which indicates what the Greeks referred to as the Metonic cycle, is repeated in a series of individual graduations on the back of the mechanism. In Michael Wright’s model, a spiral groove with a resettable arm predicted the dates of solar and lunar eclipses as an output function of the internal gearing.
One of Wright’s most insightful suppositions about the device was that the gearing that drove the display on the back side, where eclipse prediction takes place, appeared to have a pin and slot mechanism. His adapted x-rays revealed a slot and the ghost of a circular piece inside of it. Wright ultimately determined that the pin gear and the slot gear pivot on slightly offset axes. Both are connected to the 223-tooth gear, which keeps track of the Moon’s orbit. This meant that the pin and slot mechanism was a differential gearing solution designed to compensate for the irregular, elliptical orbit of the Moon around the Earth.
Another of Wright’s contributions was his discovery of a fixed boss in the main fragment. This suggests that the Antikythera mechanism was designed to show epicyclical motion with subsystems that moved about a central gear. Wright believed that the Antikythera mechanism had likely been altered, or hacked, if you will at one or more points after it was made. Primarily, he supposes the two spiral output displays on the rear of the device were repurposed from some other piece of equipment and added later, citing the appearance of the enclosure’s remains.
Around the time that Michael Wright was studying the mechanism and creating his reconstruction, a team of scientists, astronomers, and mathematicians had come together in Athens to further research the ancient calendar computer. They worked in conjunction with the Antikythera Mechanism Research Project (AMRP) to continue investigation into the mechanism and published an article in 2006 detailing their findings about the machine.
Shortly after publication, British mathematician and filmmaker Tony Freeth of the AMRP collaborated with Alexander Jones, a professor of the History of Exact Sciences in Antiquity at New York University’s Institute for the Study of the Ancient World. Together, they came up with a computer model of the Antikythera mechanism that incorporates newer knowledge about the device.
In 2005, Tony Freeth engaged scientists from Hewlett-Packard who had created a special technique for creating enhanced images of the surfaces and details of paintings. A dome covered with lamps flashes light on the object in question from various angles while a series of still photos are taken. Freeth convinced them to go to Athens and use this equipment to photograph the tiny inscriptions on the mechanism. The images did wonders for furthering the team’s understanding. They were able to confirm once and for all that the largest gear definitely had 223 teeth. Another inscription directly mentions the number ‘235’ as well as the spiral display on the back with reference to the Metonic cycle.
Freeth and Jones were able to use the month inscriptions to help determine where the Antikythera Mechanism was made. At the time of the shipwreck, each of the Greek states used its own calendar scheme. The month inscriptions on the fragments pointed to Corinth, or a colony of Corinth such as Syracuse on the island of Sicily.
How it Works – the Current Model
Years of study, measurement, photographs, and educated guesswork by several people have provided an increasingly clear picture of the mechanism’s structure. Essentially, it is a collection of gear wheels that was likely contained in a wooden box and operated with a hand crank on the side. As the crank was turned, the indicators on the front would spin around, each modeling the path of one of the major celestial bodies known to the ancient Greeks. There were separate indicators for the Sun, Moon, and five major planets known at the time. The device’s smallest indicator was a tiny sphere, colored half black and half white by those who would later model it. This little ball spun independently of its indicator arm, showing the phases of the Moon as it moved through each day of the solar calendar.
According to Michael Wright, the inner workings contain multiple gear trains for the calendar year, including the true Sun and mean Sun. Two subsystems emerge from this train, one based on the Sun and one on the Moon. The Sun side contains gearing that computes the four-year cycle of the Pan-Hellenic Olympic Games as well as the nineteen-year Metonic cycle, which is a common multiple of both the solar year and the lunar month. It also computes the seventy six-year Callippic cycle, which is four times the length of the Metonic cycle and was proposed by Greek astronomer Callippus around 330BC as an improvement over the Metonic cycle.
The ancient Babylonian astronomers had discovered what Edmund Halley would come to call the Saros cycle, which describes the full cycle of eclipse activity between the Sun and the Moon. The Babylonians found that every 223 synodic (lunar) months, the Sun, Moon, and Earth return to the same relative geometry, resulting in the same type of eclipse.
The lunar gear train connects to a lunar anomaly platform and on to an eclipse gear train that shows the 223-month Saros cycle and its proposed improvement, the 669-month Exeligmos cycle. There are additional epicyclical gearing mechanisms for the five major planetary bodies known to the ancient Greeks: Venus, Mercury, Mars, Jupiter, and Saturn.
These internal gearing systems output their calculations on the back of the device through two spiral grooves. One is divided to show the calendar cycles for the Olympic Games, the Metonic cycle, and the Callippic cycle. The other acts as an eclipse predictor, operating on the 223-month Saros cycle to show the dates of both solar and lunar eclipses. A pointer spans the radius of each ring of the groove, while an attached needle rides in the slot. This design made it possible to reset the output by lifting the pointer as one would lift the arm of a record player.
Who Made the Antikythera Mechanism?
Derek de Solla Price believed there were a few people who could have created this technological wonder. One of them was Andronicus Kyrrhestes, a Macedonian who had built a kind of ancient weather station called the Tower of Winds. His octagonal structure featured a wind vane and a complex sundial on each of its faces. A frieze around the exterior of the tower paid homage to each of the eight prevailing wind gods. Inside the tower was a clepsydra, or water clock, which was driven by water from the Acropolis.
If not Kyrrhestes, Price supposes the Antikythera mechanism was conceived by some Rhodes engineer studying under Posidonios, a renowned philosopher and meteorologist who took a great interest in measuring the distances to the Moon and stars. If the Antikythera mechanism had been the work of Archimedes, Price believes that his name would certainly have been attached to it in historical records, followed closely by a great deal of praise for having invented the differential gear. In his book, De Republica, Cicero described a device he had seen while studying at Rhodes. This was a planetarium constructed by Posidonios. In his writing, Cicero wrote of some novel differences between this new planetarium and an earlier astronomical device he greatly admired, the sphere of Archimedes.
The Future of the Antikythera Mechanism
Until recently, there had only been two officially sanctioned recovery missions of the Antikythera shipwreck: the original dredging, and Jacques Cousteau’s expedition in 1976. But in September and October of 2014, a group of divers, archaeologists, and scientists returned to the site in partnership with the Hellenic navy. With the help of some cutting-edge diving gear, they were able to recover even more objects, ranging from common tableware to treasures of antiquity, such as the giant bronze spear belonging to a life-sized warrior statue.
The group had many goals for this expedition. One of these was to map the full extent of the shipwreck with a 3D digital blueprint. A bright yellow autonomous underwater vehicle (UAV) named Sirius took care of that by providing high-resolution stereo images. Sirius was built by the marine robotics arm of the Australian Centre of Field Robotics at the University of Sydney.
Because the ship’s remains are so far underwater, diving to the site and staying for more than a few minutes is terribly dangerous. The group’s other main goal was testing a new diving suit technology called the Exosuit, which allows for dives down to 1,000 feet. With these suits, the divers could safely stay down at the wreck for over 30 minutes a day.
Both Michael Wright’s physical bronze model and Tony Freeth’s computer model of the mechanism greatly moved the needle of understanding with regard to its inner workings and reason for creation. Wright is not the only craftsman who is moved by the mechanism’s mechanical marvels. In 2010, an Apple engineer named Andrew Carol completed a working replica of the mechanism which he constructed entirely from LEGO Technic pieces.
Carol’s model is much larger than the original device, mostly due to the difference between custom-machining brass gears and modeling the same oddly-numbered cogs with pre-formed ABS gears. It also uses about twice as many gears as the original, mostly because Carol had to reckon with the way the calendar has changed over the last 2,000+ years.
In early 2014, a USC mechanical engineering student modeled the Antikythera mechanism using Solidworks. He based his files on Tony Freeth’s and Alexander Jones’ gearing proposal. He has shared the CAD files through his site, theshamblog.com, noting that they are not quite fit for 3D printing in their current state. In December 2014, he made comment about his plan to release a version intended for lasers and wood.
A Mystery Wrapped in an Enigma
There are many layers to the mystery of the Antikythera mechanism. For instance, it could have been one of a kind, or it may be the only one of many such computers to survive from antiquity.
And what was the Antikythera mechanism doing at the bottom of the Sea of Crete? Was it looted from a Greek colony along with hundreds of works of art and pieces of jewelry, or was it among the Roman shipwreck’s remains by coincidence? In his monograph, Derek de Solla Price discusses the Antikythera mechanism as a historical document, offering the point that much of what remains from ancient Greek society are the sturdier pieces of evidence like architecture, jewelry, and pottery. No Hellenistic artifact had yet been found that was anywhere near as complex as the Antikythera mechanism. Prior to its discovery, the earliest-surviving object of similar complexity dates from 1000A.D—an astrolabe created by a Persian scholar named al-Bīrūnī.
After the fall of the ancient Greek civilization, it is believed that the kind of craftsmanship and technology the mechanism represents moved east through the Byzantine Empire and on to the Arabs after the fall of Constantinople. Complex mechanical clockwork on a smaller scale began to appear in Central Europe around the end of the Middle Ages, and the automata that much of modern technology emerged from in the Victorian Era.
Diagrams Reprinted by Permission
Diagrams reprinted by permission
Gears from the Greeks: The Antikythera Mechanism–A Calendar Computer from ca. 80 B.C.
by Derek De Solla Price (ISBN 9780871696472, published November, 1974)
This article was specifically written for the Hackaday Omnibus vol #02. Order your copy of this limited edition print version of Hackaday. | 0.844119 | 3.274645 |
The discovery of ice deposits in craters scattered across the Moon’s south pole has helped to renew interest in exploring the lunar surface, but no one is sure exactly when or how that ice got there. A new study suggests that while a majority of those deposits are likely billions of years old, some may be more recent.
Ariel Deutsch, a graduate student at Brown University’s Department of Earth, Environmental and Planetary Sciences in Providence, Rhode Island and the study’s lead author, says that constraining the ages of the deposits is important both for basic science and for future lunar explorers who might make use of that ice for fuel and other purposes.
“The ages of these deposits can potentially tell us something about the origin of the ice, which helps us understand the sources and distribution of water in the inner solar system,” Deutsch said. “For exploration purposes, we need to understand the lateral and vertical distributions of these deposits to figure out how best to access them. These distributions evolve with time, so having an idea of the age is important.”
For the study, Deutsch worked with Jim Head, a professor at Brown, and Gregory Neumann from the NASA Goddard Space Flight Center in Greenbelt, Maryland. Using data from NASA’s Lunar Reconnaissance Orbiter, which has been orbiting the Moon since 2009, the researchers looked at the ages of the large craters in which evidence for south pole ice deposits was found. To date the craters, researchers count the number of smaller craters that have accrued inside the larger ones. Scientists have an approximate idea of the pace of impacts over time, so counting craters can help establish the ages of terrains.
The majority of the reported ice deposits are found within large craters formed about 3.1 billion years or longer ago, the study found. Since the ice can’t be any older than the crater, that puts an upper bound on the age of the ice. Just because the crater is old doesn’t mean that the ice within it is also that old too, the researchers say, but in this case there’s reason to believe the ice is indeed old. The deposits have a patchy distribution across crater floors, which suggests that the ice has been battered by micrometeorite impacts and other debris over a long period of time.
If those reported ice deposits are indeed ancient, that could have significant implications in terms of exploration and potential resource utilization, the researchers say.
“There have been models of bombardment through time showing that ice starts to concentrate with depth,” Deutsch said. “So if you have a surface layer that’s old, you’d expect more underneath.”
While the majority of ice was in the ancient craters, the researchers also found evidence for ice in smaller craters that, judging by their sharp, well-defined features, appear to be quite fresh. That suggests that some of the deposits on the south pole got there relatively recently.
“That was a surprise,” Deutsch said. “There hadn’t really been any observations of ice in younger cold traps before.”
If there are indeed deposits of different ages, the researchers say, that suggests they may also have different sources. Older ice could have been sourced from water-bearing comets and asteroids impacting the surface, or through volcanic activity that drew water from deep within the Moon. But there aren’t many big water-bearing impactors around in recent times, and volcanism is thought to have ceased on the Moon over a billion years ago. So more recent ice deposits would require different sources — perhaps bombardment from pea-sized micrometeorites or implantation by solar wind.
The best way to find out for sure, the researchers say, is to send spacecraft there to get some samples. NASA’s Artemis program aims to put the first woman and next man on the Moon by 2024, and plans to fly numerous precursor missions with robotic spacecraft in the meantime. Jim Head, a study co-author and Deutsch’s Ph.D. advisor, says studies like this one can help to shape those future missions.
“When we think about sending humans back to the Moon for long-term exploration, we need to know what resources are there that we can count on, and we currently don’t know,” Head said. “Studies like this one help us make predictions about where we need to go to answer those questions.” | 0.835029 | 4.060064 |
We’re lucky to live on a planet where it’s predictably warmer in the summer and colder in the winter in many regions, at least within a certain range. On Kepler-413b, it’s a world where you’d have to check the forecast more frequently, because its axis swings by a wild 30 degrees every 11 years. On Earth, by comparison, it takes 26,000 years to tilt by a somewhat lesser amount (23.5 degrees).
The exoplanet, which is 2,300 light-years away in the constellation Cygnus, orbits two dwarf stars — an orange one and a red one — every 66 days. While it would be fun to imagine a weather forecast on this planet, in reality it’s likely too hot for life (it’s close to its parent stars) and also huge, at 65 Earth-masses or a “super-Neptune.”
What’s even weirder is how hard it was to characterize the planet. Normally, astronomers spot these worlds either by watching them go across the face of their parent star(s), or by the gravitational wobbles they induce in those stars. The orbit, however, is tilted 2.5 degrees to the stars, which makes the transits far more unpredictable. It took several years of Kepler space telescope data to find a pattern.
“What we see in the Kepler data over 1,500 days is three transits in the first 180 days (one transit every 66 days), then we had 800 days with no transits at all,” stated Veselin Kostov, the principal investigator on the observation. “After that, we saw five more transits in a row,” added Kostov, who works both with the the Space Telescope Science Institute and Johns Hopkins University in Baltimore, Md.
It will be an astounding six years until the next transit happens in 2020, partly because of that wobble and partly because the stars have small diameters and aren’t exactly “edge-on” to our view from Earth. As for why this planet is behaving the way it does, no one is sure. Maybe other planets are messing with the orbit, or a third star is doing the same thing.
The next major question, the astronomers added, is if there are other planets out there like this that we just can’t see because of the gap between transit periods.
You can read more about this finding in The Astrophysical Journal (a Jan. 29 publication that doesn’t appear to be on the website yet) or in preprint version on Arxiv. | 0.899026 | 3.823767 |
As 2014 opens, most of the half dozen comets traversing the morning and evening sky are faint and require detailed charts and a good-sized telescope to see and appreciate. Except for Comet Lovejoy. This gift to beginner and amateur astronomers alike keeps on giving. But wait, there’s more. Three additional binocular-bright comets will keep us busy starting this spring.
Still glowing around the naked eye limit at magnitude 6, the Lovejoy remains easy to see in binoculars from dark skies as it tracks from southern Hercules into Ophiuchus in the coming weeks.
The best time to view the comet is shortly before the start of dawn when it sails highest in the eastern sky at an altitude of around 30 degrees or “three fists” up from the horizon. By January’s end, the comet will still be 25 degrees high in a dark sky. My last encounter with Lovejoy was a week ago when 10×50 binoculars revealed a bright coma and 1.5 degree long tail to the northwest. Through the telescope the stark contrast between bright, compact nucleus and gauzy coma struck me as one of the most beautiful sights I’d seen all month.
Looking ahead to 2014 there are at present three comets beside Lovejoy that are expected to wax bright enough to see in binoculars and possibly with the naked eye: C/2012 K1 PanSTARRS, C/2013 V5 Oukaimeden and C/2013 A1 Siding Spring The first lurks in Hercules but come early April should bulk up to magnitude 9.5, bright enough to track in a small telescope for northern hemisphere observers. Watch K1 PANSTARRS amble from Bootes across the Big Dipper and down through Leo from mid-spring through late June hitting magnitude 7.5 before disappearing in the summer twilight glow. K1 will be your go-to comet during convenient viewing hours.
Come early September after K1 PANSTARRS leaves the sun’s ken, it reappears in the morning sky, traveling westward from Hydra into Puppis. Southern hemisphere observers are now favored, but northerners won’t suffer too badly. The comet is expected to crest to magnitude 5.5 in mid-October just before it dips too far south for easy viewing at mid-northern latitudes.
Comet C/2013 V5 (Oukaimeden), discovered November 15 at Oukaimeden Observatory in Marrekesh, Morocco. Preliminary estimates place the comet at around magnitude 5.5 in mid-September. It should reach binocular visibility in late August in Monoceros the Unicorn east of Orion in the pre-dawn sky before disappearing in the twilight glow for mid-northern latitude observers. Southern hemisphere skywatchers will see the comet at its best and brightest before dawn in early September and at dusk later that month.
2014’s most anticipated comet has to be C/2013 A1 Siding Spring, expected to reach magnitude 7.5 and become binocular-worthy for southern hemisphere skywatchers as it traverses the southern circumpolar constellations this September. Northerners will have to wait until early October for the comet to climb into the evening sky by way of Scorpius and Sagittarius. Watch for an 8th magnitude hazy glow in the southwestern sky at that time.
As October ticks by, A1 Siding Spring creeps closer and closer to Mars until it overlaps the planet on the 19th. Normally, a comet will only appear to pass in front of stars and deep sky objects because it’s in the same line of sight. Not this time. Siding Spring may actually “touch” Mars for real.
On October 19 the comet will pass so close to the planet that its outer coma or atmosphere may envelop Mars and spark a meteor shower. The sight of a bright planet smack in the middle of a comet’s head should be something quite wonderful to see through a telescope.
While the list of predicted comets is skimpy and arguably not bright in the sense of headliners like Hale-Bopp in 1997 or even L4 PANSTARRS from last spring, all should be visible in binoculars from a dark sky site.
Every year new comets are discovered, some of which can swiftly brighten and put on a great show like Comet Lovejoy (discovered Sept. 7) did last fall and continues to do. In 2013, 64 new comets were found, 14 of them by amateur astronomers. Comets with the potential to make us ooh and aah are out there – we just have to find them. | 0.820693 | 3.635668 |
Today, I turn out to be the user of the day at Einstein@Home. It might not amount to much, but I'm still getting all tingly inside.
If you happen to have idle CPU cycles left over on your computer, consider contributing them to the cause of finding gravitational waves or potential sources of gravitational waves at Einstein@Home.
Remember the possibility of creating invisibility cloaks using metamaterials? While perfect invisibility can theoretically be achieved, one big problem is that light cannot reach inside the cloaking device, preventing anyone from seeing the outside. No surprise there, since it works by diverting the incoming light waves away from the inside and then putting them back on their original course.
However, it turns out that blocking out the waves can itself be a very useful thing. Not so much for light, where a cheap box would do. Instead, someone remembered that light is not the only thing that is made up of waves. Earthquakes cause seismic waves through the ground which shake things up and even destroy buildings, and an "invisibility cloak" that worked on seismic waves would protect the inside from earthquakes. The weakness of an invisibility cloak can end up being its strength! And since cloaking would not be the goal here, there is no need to even attempt perfect invisibility in seismic waves and should be a lot easier to do.
Researchers from the University of Liverpool figured out how such an invisibility cloak for earthquakes can be constructed out of concentric rings of plastic. It is only a theoretical design so far, but hopefully it could be applied in the real world in the not too distant future. Even if it never becomes practical, it is still pretty neat how the idea of an invisibility cloak can be turned on its head.
The ESA space observatory Integral had observed gamma-rays from the center of the galaxy, which indicated the presence of positrons distributed in a way that couldn't quite be explained with known phenomenon. Hence some physicists speculated that the positrons may have been the result of dark matter annihilation. Not only did the distribution of positrons within our galaxy turn out to be lopsided, arguing against dark matter annihilation as the source, but it has now been explained how supernovae could be responsible for the distribution of positrons.
Some had thought that supernovae could not be the source of most of the positrons because it was assumed that they would all annihilate very close to their origin, which would not match the observed distribution of positrons. But it turns out that the positrons from supernovae, which are the result of the decay of heavy elements from the stellar explosion, travel nearly at the speed of light and can travel for thousands of light-years before slowing down and annihilating with an electron. By considering how electrons move in galactic magnetic fields, they were able to model how positrons would travel before being annihilated, and the results seem to be consistent with the Integral observations.
This deals a blow to the hypothesis that dark matter annihilation may be responsible for the positron distribution. I wonder if the same implication can be inferred for the PAMELA observations?
The CDF collaboration at Fermilab has announced the observation of a new baryon Ωb, which was also observed by the DZero collaboration, also at Fermilab, last year. It's made up of two strange quarks and one bottom quark, which are of the sort we normally do not see in nature, and it has a lifetime of only a trillionth of a second. The observation of Ωb by CDF fits well with the Standard Model of particle physics, but the interesting thing is that the measured mass conflicts with the measurement done by DZero. | 0.853302 | 3.538633 |
ARI researcher Sebastian Kamann helps confirm ancient Chinese sighting
For the first time, researchers have discovered the remains of a nova in a globular cluster. A nova is a transient astronomical event, observed when a star suddenly becomes almost 100,000 times brighter than the Sun and then slowly fades. This happens in binary systems – one star accretes gas from its companion, triggering an eruption on the surface of the accreting star. The material ejected in the eruption forms a slowly expanding nebula that can survive for centuries, long after the nova has faded. It was the glow from such a nebula that Sebastian Kamann helped to discover, in the Milky Way globular cluster Messier 22 located in the constellation Sagittarius.
"The position and brightness of the remains match an entry from 48 BC in an ancient collection of observations by Chinese astronomers," says Fabian Göttgens at the University of Göttingen, lead author of the study. This makes the ancient sighting one of the oldest observations of an event outside the solar system confirmed using modern instrumentation. The newly discovered nova remnant has a diameter of about 8,000 times the distance between the Earth and Sun. Despite its size, the nebula does not contain a large amount of material, with a mass around 30 times greater than Earth.
The observations were made with MUSE, an integral field spectrograph at the Very Large Telescope – one of the largest optical telescopes in the world – operated by the European Southern Observatory in the Atacama Desert in Chile. MUSE is currently being used to carry out a large survey of star clusters in the Galaxy and the local neighbourhood. “It is a bit funny,” says Sebastian Kamann, one of the initiators of the survey, “The centres of globular clusters like Messier 22 are some of the most frequently observed patches of the sky, but nobody ever saw the nebula.” Nova remnants only emit light in specific narrow wavelength ranges, and since most cameras integrate light over a much wider wavelength range, the remnants disappear in the noise. The power of MUSE is that instead of taking one image, it takes 3,500 monochromatic images simultaneously, each at a slightly different wavelength. “The nebula revealed itself in about a dozen of these images, while it remained invisible in the rest”, Kamann adds.
The MUSE observations not only enable the discovery of faint nebulae, but also the study of the stellar motions. In a previous publication based on the MUSE data, Kamann and his colleagues found that the motions of the stars in the clusters are not completely random; the clusters as a whole are slowly rotating. In addition, the data confirmed for the first time the presence of a stellar-mass black hole in a star cluster.
The results will be published in the journal Astronomy & Astrophysics. | 0.861147 | 3.812951 |
The first verified Interstellar Visitor to our Solar System is the object 1I/2017 U1 (aka ʻOumuamua), which is a spindle shaped body that flew in from the direction of the constellation Lyra, came closer to the Sun than Mercury, shot past Earth at a distance of 0.16 AU, then receded rapidly away. Ultimately 1I/2017 U1 will leave with a hyperbolic excess of over 26 km/s.
The Initiative For Interstellar Studies, of which I am a part, was naturally intrigued by the possibility of sending a probe to an Interstellar Object using near-term technologies on a merely decadal mission, rather than millennial. The resulting effort by a great team produced this preprint:
…which is a starting point for further research work on the options available. Technology Review even picked it as one of the best arXiv Preprints of the Week ending 17 November 2017.
My initial thoughts, for a very rapid mission preparation, would be a clone of the New Horizons vehicle, which successfully visited Pluto/Charon and is heading for a new encounter in 2019, but launched into a Jupiter gravity-assist that would throw it towards the Sun. Why? To maximise the boost, via the Oberth (or “Gravity Well”) Maneuver. I assumed a high-thrust chemical rocket, based on the JPL work for sending probes into the Local Interstellar Medium.
Other options, with lower technology readiness levels (TRLs), would rely on Solar Thermal Boosters, Solar Electric Propulsion, E-Sails, Mag-Sails, and so forth. They’re all good, but 1I/2017 U1 is *rapidly* leaving the Solar System behind. A decade delay in launching means the intercept is out in the “Great Big Dark” between the stars, thus complicating navigation, antenna pointing, and likely science return.
Even if we don’t launch after this particular interstellar vagabond, all our best theories of planet formation suggest immense numbers of such objects are passing by. We’ve only *just* become able to see them, thanks to powerful all-sky surveys that have gone online in recent years. | 0.810458 | 3.473786 |
Cosmic bursts find all that missing matter
Mysterious explosions help solve a longstanding mystery.
Astronomers have used fast radio bursts to finally detect all of the missing “normal” matter in the vast space betwee...
A 'cosmic ring of fire' of 11 billion years ago
Astronomers say rare galaxy will shake up a few theories.
Astronomers have observed a rare galaxy type as it existed 11 billion years ago, and this, they say, is likely to sha...
Close encounters likely spawned stellar births
Astronomers reconsider the impact of Sagittarius.
New stars are likely to have been born in the Milky Way as a result of recurrent encounters with the Sagittarius dwar...
Early disc galaxy puts theories in a spin
It’s huge and distant, so how did it form?
Astronomers have found a massive rotating disc galaxy that formed just 1.5 billion years after the Big Bang, when the...
Astronomers see signs of planet birth
On VLT’s new images, the twist marks the spot.
Astronomers have reported what could be the first direct evidence of a baby planet coming into existence. Around t...
A ‘decoder’ to gauge exoplanet climate
Colours may be clues to where we might live.
Astronomers from Cornell University in the US have developed what they call an environmental colour “decoder” to teas...
That’s not lava, it’s mud
European scientists unravel a Martian mystery.
Lava-like flows on Mars are more likely caused by mud than lava, according to a new study. A European team used th...
Why astronomy matters in times of crisis
The thoughts of Australia’s first Astronomer-at-Large.
In an international emergency like the present one, you might expect the science of the stars to be the last thing on...
Regular rhythms among pulsating stars
Astronomers learn more about delta Scutis.
Astronomers have detected regular pulsations in a class of intermediate-sized stars known as delta Scutis that has un...
Bending the bridge between galaxy clusters
Telescopes capture the distant action in Abell 2384.
Astronomers have found a bridge of gas extending over three million light-years from two galaxy clusters in the syste...
Brines on Mars not habitable, study says
They are common, but not ‘special’.
Liquid brines on Mars may be more common and longer lasting than previously thought, but their properties and tempera...
This X is more like two boomerangs
MeerKAT explains a distant galaxy.
Many galaxies have enormous twin jets of radio waves extending into intergalactic space. Normally these go in opposit... | 0.809422 | 3.187333 |
The colonization of Mars raises numerous interesting questions that strike at the heart of our relationship with both space and each other. Do we have the right to populate other planets? Do we have the duty to populate other planets? Should we consciously sculpt the genetics of a human settlement? Does Matt Damon want to come with?
But, in a sense, the most basic question has nothing to do with Mars itself. The question concerns population dynamics: How many people do we need to send to the Red Planet to create a genetically sustainable colony?
It is helpful to define the requirement first. Let’s say “sustainable” means capable of growing over the course of 200 years. In that time, it is not only possible, but likely, that advances in the science of deep space exploration — made on Mars or, ideally, on a still-functioning Earth — will allow us to visit with our extremely distant cousins on a regular basis.
A 2002 study on this “minimum viable population” calculated the ideal number at 160, or “about the size of a small village.” That number provides both the necessary diversity in haplotypes (chromosome sets) to ensure survival, and also includes the “million-year-old institution designed to assist reproduction” — the family. But don’t worry, it’s not that simple.
The catch is that we’ve got to get to 160 and we’re not sending busloads of astronauts into the big black. Essentially, the two approaches to solving this problem are:
1) Inbreed like crazy.
2) Bring frozen embryos or frozen sperm and frozen eggs.
And, no, we can’t just send 160-people worth of genetic material into space. It’s not reasonable to expect, let’s say, 10 astronauts to raise that many children. It will realistically take multiple generations to hit the 160 mark, at which point there will be actual families and shared genes on the planet. It’s that third generation, consisting of naturally conceived and not-so-naturally conceived babies that can hit the threshold.
And the pressure to do just that will be extraordinary. Cutting the number of individuals too close to the bare minimum risks manifesting disadvantageous traits, characteristics and afflictions that could jeopardize the colony. There’s nothing wrong with blue people per se, but inbreeding doesn’t generally end well. Just look at the British royal family.
Next question! Where should we get all these genes?
To answer this, you might look to the existing mission of Mars One, a Dutch non-profit organization dedicated to realizing the goal of manned Mars colonization by 2027. That organization has already trimmed a list of 660 applicants for the first manned mission in 2027 to 100, and started an ambitious round of fundraising. (For a fascinating look into Mars One’s selection process, see this Q&A with Dr. Norbert Kraft, Mars One’s Chief Medical Officer.)
The question of who goes to Mars is the subtext of the debate between private and public space exploration efforts. In a way, private businesses have an easier time deciding who to take, as they may not have to justify their metrics to “public” stakeholders. But you better believe there will have to be a conversation about race and genetics that will make Senate sub-committee members panic.
“Mars is by far the most promising [destination] for sustained colonization and development,” writes Drs. Dirk Schulze-Makuch, and Paul Davies, in their 2010 paper, “To Boldly Go: A One-Way Mission to Mars.” “[I]t is similar in many respects to Earth and, crucially, possesses a moderate surface gravity, an atmosphere, abundant water and carbon dioxide, together with a range of essential minerals.”
“To Boldly Go” raises the intriguing suggestion that the first colonists of Mars should be individuals past the age of reproduction, for the simple reason that a one-way Mission to Mars is, if not a suicide mission, the end of both individuals’ lives on Earth. Furthermore, we’re not sure how low gravity and space radiation will effect inter-planetary travelers. Individuals with no reproductive capacity could set up base camp while serving as canaries in the space cave.
For now, the conversation about population growth on Mars will orbit around the idea of multiple flights. But that’s probably not the most efficient way to go about this. It may simply be the most palatable to the general public. | 0.844021 | 3.483931 |
Gaze at 'the sea' in our November skies
The Astronomical Society of Las Cruces next will meet at 7:30 p.m. Friday, Nov. 18, in the Creative Arts room of the Good Samaritan Village, 3025 Terrace Drive. All are welcome.
LAS CRUCES - November evenings give those of us in the high desert the chance to look out on the sea. In the darkness above us is a group of constellations that all are associated with water and this expanse is sometimes referred to as “The Sea.” Cetus, the Whale, Piscis Austrinus, the Southern Fish, and Pisces, the Fishes, are among the denizens of this Sea. At the western end of the Sea is a transitional constellation representing a mythical half fish, half goat named Capricornus, the Sea Goat.
This ancient constellation was known to the Sumerians and Babylonians who thought of it as a goatfish. These Bronze-Age civilizations depicted Capricornus in their star catalogs dating from before 1000 BC. It is the smallest of the 12 zodiacal constellations, constellations that have a significant portion of the ecliptic passing through them.
The ecliptic is the path that the Sun appears to take each year as we on the Earth view the Sun from our orbit revolving around it. The ecliptic is very stable against the background stars. However, the Earth wobbles like a gyroscope that is spinning down, moving the north celestial pole (currently very close to Polaris) in a circle 47 degrees across in the sky.
The wobble, called precession, is caused by the Sun’s and Moon’s gravity tugging on the equatorial bulge of the Earth. If the Earth were a perfect sphere, there would be no precession. Even with the bulge at its equator, there will still not be any precession if we were spinning by ourselves in empty space. However, the Moon and the Sun both exert a gravitational pull on the Earth and its bulge. This still would not cause precession, if they both stayed centered over the equator, but they do not. The gravitational pull from above or below the bulge acts to cause the Earth to wobble. Greek astronomer Hipparchus first described precession in the 2nd century BC, though it is likely that astronomers in other countries could have discovered it earlier.
As the poles are moved by precession, this also changes the locations where the Sun is among the constellations when each of the four seasons begins. In Greek times, the Sun was in Capricornus as Northern Hemisphere winter began. In the succeeding 3,000 years, precession has moved the Sun’s location as winter starts into the neighboring zodiacal constellation of Sagittarius. It will continue to move around the rest of the zodiacal constellations over the next 26,000 years it takes for the Earth’s axis to wobble back to its current location.
Capricornus is associated with a playful creature named Pan. Pan is alleged to be half man with goat legs and hooves as well as goat horns. Pan spent most of his time chasing females or sleeping it off. He tried to seduce the nymph Syrinx, but she turned herself into reeds. The wind blew through the reeds making a lovely sound. Pan put the reeds together with wax to make his famous pipes of Pan.
Pan saved the Greek gods twice during the war with the Titans. On one occasion, Pan blew a conch shell and frightened the enemy into flight. Later, Gaia (Mother Earth) sent the monster Typhon to slay the gods. Pan warned the gods of Typhon’s approach. He suggested they turn themselves into animals to hide from Typhon. Pan dove into the river and tried to turn himself into a fish. In his haste, Pan only half-succeeded, changing his lower half into a fish. For his services, Zeus placed him in the sky as Capricornus.
Mercury begins its next appearance in the evening sky toward the end of this month. It will be higher next month when it reaches its furthest distance from the Sun. The other planet nearer the Sun than we are, Venus, dominates the evening sky. It moves eastward among the stars this month, passing close to the star at the top of the teapot of Sagittarius, known as Kaus Borealis.
Between these two planets is Saturn, finishing its run in the evening sky. Being so far from the Sun, Saturn only moves very slowly eastward among the stars of Ophiuchus as it and all the stars around it slide slowly toward the Sun. Further east, Mars is in Capricornus, about halfway up in the southern sky as it gets dark.
That takes care of all the visible planets except the King of the Planets, Jupiter. The Giant Planet rises around 4:30 a.m. in Virgo and it is easily visible 32 degrees above the east-southeastern horizon as it starts to get light.
If you would like to look at the sky through a telescope, the Astronomical Society of Las Cruces will have an array of telescopes at International Delights Café on El Paseo Road in Las Cruces on Saturday, Nov. 5, starting at dusk and running for about two hours, weather permitting. If you want to see the stars under darker skies, the society’s observatory at Leasburg Dam State Park (about 15 miles north of Las Cruces) will be open on the evening of Saturday, Nov. 19.
The Astronomical Society of Las Cruces is an organization of amateur and professional astronomers interested in furthering the science of astronomy and love of the sky. If you have an interest in astronomy, we hope you will join us. You are invited to our next meeting at 7:30 p.m. on Friday, Nov. 18, in the Creative Arts room of the Good Samaritan Village, 3025 Terrace Drive. Further information is available at www.aslc-nm.org.
Bert Stevens has been an amateur astronomer and astrophotographer for over 47 years and has discovered 56 asteroids. | 0.917201 | 3.468379 |
Discovered by high school research team
A team of highly determined high school students discovered a never-before-seen pulsar by painstakingly analyzing data from the National Science Foundation's (NSF) Robert C. Byrd Green Bank Telescope (GBT). Further observations by astronomers using the GBT revealed that this pulsar has the widest orbit of any around a neutron star and is part of only a handful of double neutron star systems.
This impressive find will help astronomers better understand how binary neutron star systems form and evolve.
Pulsars are rapidly spinning neutron stars, the superdense remains of massive stars that have exploded as supernovas. As a pulsar spins, lighthouse-like beams of radio waves, streaming from the poles of its powerful magnetic field, sweep through space. When one of these beams sweeps across the Earth, radio telescopes can capture the pulse of radio waves.
"Pulsars are some of the most extreme objects in the universe," said Joe Swiggum, a graduate student in physics and astronomy at West Virginia University in Morgantown and lead author on a paper accepted for publication in the Astrophysical Journal explaining this result and its implications. "The students' discovery shows one of these objects in a really unique set of circumstances."
About 10 percent of known pulsars are in binary systems; the vast majority of these are found orbiting ancient white dwarf companion stars. Only a rare few orbit other neutron stars or main sequence stars like our Sun. The reason for this paucity of double neutron star systems, astronomers believe, is the process by which pulsars and all neutron stars form.
When a massive star goes supernova at the end of its normal life, the explosion can be a little one-sided, imparting a "kick" to the remaining stellar core. When this happens, the resulting neutron star is sent hurtling through space. These kicks -- and the corresponding mass loss from a supernova explosion -- mean that the chances of two such stars remaining gravitationally locked in the same system are remarkably slim.
This pulsar, which received the official designation PSR J1930-1852, was discovered in 2012 by Cecilia McGough, who was a student at Strasburg High School in Virginia at the time, and De'Shang Ray, who was a student at Paul Laurence Dunbar High School in Baltimore, Maryland.
These students were participating in a summer Pulsar Search Collaboratory (PSC) workshop, which is an NSF-funded educational outreach program that involves interested high school students in analyzing pulsar survey data collected by the GBT. Students often spend weeks and months poring over data plots, searching for the unique signature that identifies a pulsar. Those who identify strong pulsar candidates are invited to Green Bank to work with astronomers to confirm their discovery.
Astronomers determined that this new pulsar is part of a binary system, based on the differences in its spin frequency (revolutions per second) between the original detection and follow-up observations.
Optical telescope surveys of the same area of the sky, however, revealed no visible companion - which would have been clearly seen if it were a white dwarf star or main sequence star. "Given the lack of any visible signals and the careful review of the timing of the pulsar, we concluded that the most likely companion was another neutron star," said Swiggum.
Further analysis of the timing of the pulses indicates that the two neutron stars have the widest separation ever observed in a double neutron star system.
Some pulsars in double neutron star systems are so close to their companion that their orbital paths are comparable to the size of our Sun and they make a full orbit in less than a day. The orbital path of J1930-1852 spans about 52 million kilometers, roughly the distance between Mercury and the Sun and it orbits its companion once every 45 days. "Its orbit is more than twice as large as that of any previously known double neutron star system," said Swiggum. "The pulsar's parameters give us valuable clues about how a system like this could have formed. Discoveries of outlier systems like J1930-1852 give us a clearer picture of the full range of possibilities in binary evolution."
Studies involving Pulsar Search Collaboratory discoveries are ongoing; as the PSC program continues, astronomers expect the 130 terabytes of data produced by the 17-million-pound GBT will likely reveal dozens of previously unknown pulsars.
The Pulsar Search Collaboratory is a joint project between the National Radio Astronomy Observatory and West Virginia University. The goal is to give high school students experience doing real research.
"This experience taught me that you do not have to be an 'Einstein' to be good at science," said McGough, who is now a Schreyer Honors College scholar at Penn State University in State College majoring in astronomy and astrophysics and physics. "What you have to be is focused, passionate, and dedicated to your work."
"As we look up into the sky and study the universe, we try to understand what's out there," said Ray, currently a student at the Community College of Baltimore County studying biology, engineering, and emergency medical services. "This experience has helped me to explore, to imagine, and to dream what could be and what we haven't seen."
The 100-meter Green Bank Telescope is the world's largest fully steerable radio telescope. Its location in the National Radio Quiet Zone protects the incredibly sensitive telescope from unwanted radio interference, enabling it to perform unique observations.
Charles Blue | EurekAlert!
Convenient location of a near-threshold proton-emitting resonance in 11B
29.05.2020 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences
A special elemental magic
28.05.2020 | Kyoto University
In living cells, enzymes drive biochemical metabolic processes enabling reactions to take place efficiently. It is this very ability which allows them to be used as catalysts in biotechnology, for example to create chemical products such as pharmaceutics. Researchers now identified an enzyme that, when illuminated with blue light, becomes catalytically active and initiates a reaction that was previously unknown in enzymatics. The study was published in "Nature Communications".
Enzymes: they are the central drivers for biochemical metabolic processes in every living cell, enabling reactions to take place efficiently. It is this very...
Early detection of tumors is extremely important in treating cancer. A new technique developed by researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from normal tissue. The work is published May 25 in the journal Nature Nanotechnology.
researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from...
Microelectronics as a key technology enables numerous innovations in the field of intelligent medical technology. The Fraunhofer Institute for Biomedical Engineering IBMT coordinates the BMBF cooperative project "I-call" realizing the first electronic system for ultrasound-based, safe and interference-resistant data transmission between implants in the human body.
When microelectronic systems are used for medical applications, they have to meet high requirements in terms of biocompatibility, reliability, energy...
Thomas Heine, Professor of Theoretical Chemistry at TU Dresden, together with his team, first predicted a topological 2D polymer in 2019. Only one year later, an international team led by Italian researchers was able to synthesize these materials and experimentally prove their topological properties. For the renowned journal Nature Materials, this was the occasion to invite Thomas Heine to a News and Views article, which was published this week. Under the title "Making 2D Topological Polymers a reality" Prof. Heine describes how his theory became a reality.
Ultrathin materials are extremely interesting as building blocks for next generation nano electronic devices, as it is much easier to make circuits and other...
Scientists took a leukocyte as the blueprint and developed a microrobot that has the size, shape and moving capabilities of a white blood cell. Simulating a blood vessel in a laboratory setting, they succeeded in magnetically navigating the ball-shaped microroller through this dynamic and dense environment. The drug-delivery vehicle withstood the simulated blood flow, pushing the developments in targeted drug delivery a step further: inside the body, there is no better access route to all tissues and organs than the circulatory system. A robot that could actually travel through this finely woven web would revolutionize the minimally-invasive treatment of illnesses.
A team of scientists from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart invented a tiny microrobot that resembles a white blood cell...
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29.05.2020 | Power and Electrical Engineering | 0.864718 | 4.010183 |
For the first time Astronomers witness a star collapse into a Black hole
Kenya Confidential Science Editor, Nairobi, September 13, 2016
Astronomers witness a star collapsing into a black hole for the first time as
Red Supergiant that’s 20 million light-years away goes dark.
Our models for how stellar black holes form are just that, models. They’re based on the complicated mathematics of what happens when a massive star collapses at the end of its lifecycle. But scientists haven’t actually witnessed the process of black hole formation directly before. That is, until now.
Using data from the Hubble Space Telescope, a team of astronomers from Ohio State University in Columbus believe they have been observing a red supergiant star, N6946-BH1, at the end of its lifecycle. In fact, in their latest observation, the star appears to have poofed out of existence. Where recently there was a bright star, now there only remains a darkness with a faint afterglow, reports New Scientist.
“This may be the first direct clue to how the collapse of a star can lead to the formation of a black hole,” said Avi Loeb at Harvard University.
The star, which is about 20 million light-years away, was first observed in 2004. Back then it was a star about 25 times larger than our sun. Later, in 2009, astronomers were witness to a spectacular light show as N6946-BH1 suddenly flared to become a million times brighter than our sun, and then faded just as suddenly. It was as if a bomb had exploded within its core.
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Researchers now believe this bright explosion was an example of what models predict about the final moments before a star collapses into a black hole, as a cloud of hydrogen ions left over from when the dying star ignites.
The newest Hubble images of this star seem to confirm that it has indeed collapsed into a black hole. They show … well, they show almost nothing. Where there was once a bright star, now there’s only darkness. Though the star has vanished from the visible spectrum of light, there remains a faint hint of its previous existence: a pale infrared afterglow.
Of course, the star didn’t just disappear. It transformed into a black hole. Or at least, that’s the best guess. Scientists can’t be certain of what’s happened until they make more measurements. For instance, when material falls into a black hole, it emits X-rays in a particular spectrum. Spotting these X-rays will be the next step to confirming the existence of a new black hole.
The team will get an opportunity to make these observations in just a few months, when new data from the Chandra X-ray Observatory becomes available.
If it turns out that N6946-BH1 has, as suspected, collapsed into a black hole before our eyes, it will be the first time such an event has ever been directly observed in real time. This could not just confirm our models and simulations about how stellar black holes form, but it could help us to improve them.
It’s pretty remarkable, though, that an event like this could be predicted and simulated decades before anyone had ever observed it happening in reality. | 0.818602 | 3.584673 |
These fluctuations extract momentum and energy from the cosmic rays, and transfer it to the gas. The end result is that the cosmic rays and thermal gas are strongly coupled together.
- Extragalactic sources and ultra-high energy cosmic rays.;
- Brazils Dance with the Devil: The World Cup, The Olympics, and the Fight for Democracy.
- The Essential Juliana Ewing Collection (16 books)?
- Cosmic ray / Gamma ray / Neutrino and similar experiments.
- Key Laboratory of Particle AstrophysicsInstitute of High Energy Physics.
- Cosmic Ray Research.
This works very nicely in hot, fully ionized gas. This means that the cooler gas seen in outflows from other galaxies must be driven by another mechanism, or must have formed once the wind had already been accelerated.
- Cosmic Ray Astrophysics / Edition 1.
- Cardiac CT?
- Please note:;
- John Lockes Politics of Moral Consensus!
- Business Loans from Family & Friends: How to Ask, Make It Legal & Make It Work.
- Top Authors.
- Cosmic ray astrophysics.
We are applying similar ideas to other galaxies, where conditions can be quite different. Elements heavier than iron are significantly more rare in the cosmic-ray flux but measuring them yields critical information to understand the source material and acceleration of cosmic rays. SuperTIGER is a cosmic-ray balloon instrument measuring cosmic-rays heavier than iron to explore the source of cosmic rays and their acceleration sites.
SuperTIGER's first flight lasted for 55 days, a record in duration for an Antarctic long duration scientific balloon payload.
- Elementary Processes of Importance for Cosmic Ray Astrophysics and X-ray Astronomy!
- Russian Minority Politics in Post-Soviet Latvia and Kyrgyzstan: The Transformative Power of Informal Networks.
- AGN Jet Model for the Fermi Bubbles.
- The Book of Urizen / Книга Уризена (иллюминированная книга).
Even if we can't trace cosmic rays directly to a source, they can still tell us about cosmic objects. Most galactic cosmic rays are probably accelerated in the blast waves of supernova remnants. Bouncing back and forth in the magnetic field of the remnant randomly lets some of the particles gain energy, and become cosmic rays. Eventually they build up enough speed that the remnant can no longer contain them, and they escape into the galaxy.
Cosmic rays accelerated in supernova remnants can only reach a certain maximum energy, which depends on the size of the acceleration region and the magnetic field strength. However, cosmic rays have been observed at much higher energies than supernova remnants can generate, and where these ultra-high-energies come from is an open big question in astronomy.
SUMMARY OF THE WORKSHOP ON COSMIC RAY ASTROPHYSICS
Perhaps they come from outside the galaxy, from active galactic nuclei , quasars or gamma ray bursts. Or perhaps they're the signature of some exotic new physics: superstrings, exotic dark matter , strongly-interacting neutrinos, or topological defects in the very structure of the universe.
Questions like these tie cosmic-ray astrophysics to basic particle physics and the fundamental nature of the universe. Confined by a magnetic field in supernova remnants, high-energy particles move around randomly. Sometimes they cross the shock wave. With each round trip, they gain about 1 percent of their original energy.
After dozens to hundreds of crossings, the particle is moving near the speed of light and is finally able to escape. Astronomer's Toolbox. Overview In the first part, the book gives an up-to-date summary of the observational data. Product Details Table of Contents. Table of Contents 1.
01/08/2016 to 07/08/2016
Cosmic Rays as Part of the Universe. Direct Observations of Cosmic Rays. Interactions of Cosmic Ray Electrons. Interactions of Cosmic Ray Nuclei.
Indirect Observations of Cosmic Rays. Statistical Mechanics of Charged Particles. Test Wave Approach 1. Waves in Cold Magnetized Plasmas. Test Wave Approach 2.
Cosmic Ray Astrophysics Research Papers - zapouce.ga
Waves in Hot Magnetized Isotropic Plasmas. Test Wave Approach 3. Generation of Plasma Waves. | 0.841684 | 3.656866 |
WASHINGTON (Reuters) - Scientists on Monday unveiled the first global geological map of Saturn's moon Titan including vast plains and dunes of frozen organic material and lakes of liquid methane, illuminating an exotic world considered a strong candidate in the search for life beyond Earth.
The map was based on radar, infrared and other data collected by NASA's Cassini spacecraft, which studied Saturn and its moons from 2004 to 2017. Titan, with a diameter of 3,200 miles (5,150 km), is the Solar System's second-biggest moon behind Jupiter's Ganymede. It is larger than the planet Mercury.
Organic materials - carbon-based compounds critical for fostering living organisms - play a leading role on Titan.
"Organics are very important for the possibility of life on Titan, which many of us think likely would have evolved in the liquid water ocean under Titan's icy crust," said planetary geologist Rosaly Lopes of NASA's Jet Propulsion Laboratory in California.
"Organic materials can, we think, penetrate down to the liquid water ocean and this can provide nutrients necessary for life, if it evolved there," added Lopes, who led the research published in the journal Nature Astronomy.
On Earth, water rains down from clouds and fills rivers, lakes and oceans. On Titan, clouds spew hydrocarbons like methane and ethane - which are gases on Earth - in liquid form due to the moon's frigid climate.
Rainfall occurs everywhere on Titan, but the equatorial regions are drier than the poles, said study co-author Anezina Solomonidou, a European Space Agency research fellow.
Plains (covering 65 percent of the surface) and dunes (covering 17 percent of the surface) made up of frozen bits of methane and other hydrocarbons dominate Titan's mid-latitudes and equatorial regions, respectively.
Titan is the only Solar System object other than Earth boasting stable liquids on the surface, with lakes and seas of full of methane being major features at its polar regions. Hilly and mountainous areas, thought to represent exposed portions of Titan's crust of water ice, represent 14 percent of the surface.
"What is really fun to think about is if there are any ways that those more complex organics can go down and mix with water in the deep icy crust or deep subsurface ocean," JPL scientist and study co-author Michael Malaska said.
Noting that on Earth there is a bacterium that can survive just on a hydrocarbon called acetylene and water, Malaska asked, "Could it or something like it live in Titan deep in the crust or ocean where temperatures are a little warmer?"
The map was created seven years before the US space agency is set to launch its Dragonfly mission to dispatch a multi-rotor drone to study Titan's chemistry and suitability for life. Dragonfly is scheduled to reach Titan in 2034.
"It is not only scientifically important but also really cool - a drone flying around on Titan," Lopes said. "It will be really exciting."
(Reporting by Will Dunham; Editing by Tom Brown) | 0.893272 | 3.540379 |
Sirius Star System
Sirius is a star system which is 8.6 light years away from Earth. One light-year is nearly 6 trillion miles. It consists of two stars, Sirius A is the main sequence star and Sirius B is a small white dwarf. Sirius B has a highly elliptical orbit around Sirius A. This binary star system is located in Canis Major, near Orion.
It is the brightest star in the night sky. It is twenty times brighter than the Sun and has a temperature exceeding it by 4000 K. It is approximately 40% larger in size compared to the Sun.
Quick Facts: –
- The name of this star has been derived from the Greek term Seirios that means “glowing”.
- This star system is approximately 300 million years old, and was previously composed of two huge bluish stars.
- It is also the closest star that can be seen without a telescope.
- It is known by various other names including the “Dog Star” and “Alpha Canis Major”.
- Sirius B has a temperature of around 25,200K which makes it hotter than Sirius A.
- This star is one of the 27 stars on the Brazil flag and it depicts the state of Mato Grosso.
- Originally, Sirius B was a B-type star. It had about five times the mass of the Sun.
- There are also speculations that there is a third star that exists in this star system but so far there is no evidence to confirm this.
- Sirius A has a radius of 740,000 miles and Sirius B has a radius of approximately 3,650 miles.
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Declan, Tobin. " Fun Sirius Facts for Kids ." Easy Science for Kids, May 2020. Web. 26 May 2020. < https://easyscienceforkids.com/sirius-facts/ >.
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Tobin, Declan. (2020). Fun Sirius Facts for Kids. Easy Science for Kids. Retrieved from https://easyscienceforkids.com/sirius-facts/
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