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Title: The Three Dimensional Evolution to Core Collapse of A Massive Star
Authors: S. M. Couch, E. Chatzopoulos, W. D. Arnett, F. X. Timmes
First Author’s Institution: TAPIR, Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, CA
Status: Submitted to ApJ Letters
There are hordes of them out there. Giant behemoths that masquerade as massive stars, but that never birthed a single radiant photon nor fused a pair of hydrogen nuclei. All of them are found on Earth. Instead of atoms, they’re built of up strings of 0’s and 1’s and live in computers of all shapes and sizes across the world (though they’d prefer the roomier accommodations of supercomputers, if you ask them). Inspired by their real, yet enigmatic counterparts in the physical universe, we first brought them to life in simple, spherically symmetric, one-dimensional form. We quickly bestowed them full three-dimensional complexity and an increasingly comprehensive set of input physics as soon as our computers possessed the computational brawn to handle them, feathery convective plumes and other instabilities, mottled compositional complexions, freewheeling invisible neutrinos, and all.
All for one goal: to understand how they die. We’ve observed their real counterparts supernovae over and over and over again, at a rate of about one every five seconds, bursting in galaxies near and far, their spectacular showers of photons (sometimes rivaling that of an entire galaxy) often traveling cosmic distances to reach our army of telescopes on Earth. We’ve sought to replicate these supernovae in our virtual massive stars, giving them encouraging nudges by injecting extra boosts of energy-imparting, explosion-inducing neutrinos, giving them a bit of a spin, tweaking how their mass is distributed, sending in sound waves, draping them with magnetic fields.
And yet. Despite the care with which we’ve crafted them, our virtual massive stars almost always refuse to explode.
What might we be missing in our theories of massive stellar death? It’s a question we’ve been asking for decades. Instead of focusing on the properties of the stellar cores that collapse and usher in their deaths, the authors of today’s paper instead turned to consider the life of the star preceding. They were motivated particularly by hints that the silicon-burning shell surrounding the pre-collapse core could be violently turbulent, stirred by convective motions in the shell. The authors thus concocted a new star, one 15 times the mass of our Sun. They harnessed the power of MESA, a special-purpose code built specifically for modeling the life of stars in 1D, from their early lives burning hydrogen, then helium, carbon, all the way to silicon and the formation of an iron core, about three minutes shy of core collapse. In order to focus on the effects of a convection in a silicon-burning shell, they stripped their stars of any complexifying qualities: no rotation, no magnetic fields.
At this point, however, their star possessed no convection, which cannot develop in 1D. Thus the authors turned to FLASH, a powerful hydrodynamics code that can follow the evolution of the complex gas motions that give rise to convection in stars. And this time, they let the star evolve in 3D. At the end of this, they had a star with a fully convective silicon-burning shell (see Figure 1), replete with characteristic convective plumes—spectacular ones that spanned the entire width of the silicon-burning shell and churned at velocities of several hundreds of kilometers a second, whirling around an 1.3 solar mass iron core on the verge of collapse.
And then, of course, came the collapse. The authors exploded two stars, twin stars, identical in every way except that one lived in one dimension and was thus spherically symmetric, while the other lived in three (though because of the computational complexity they modeled only an octant of the star) and thus retained its convectively-stirred, complex 3D structures. To help the stars explode, they were given identical shots of extra energy in the form of neutrino heating, then let go. And go they did—and differently in some key ways. Their cores initially evolved much in the same way: they collapsed, rebounded, giving birth to a shock, both of which successfully continued to grow. When the shock reached the silicon-burning shell, substantial differences began to show: the 3D convective star’s shock grew more rapidly than its 1D twin, and had a larger explosion energy. Though the authors did not evolve the collapse long enough to determine whether or not the star eventually exploded, these were promising signs that an explosion could be achieved more readily.
So does this mean that we now have it—the secret to the deaths of massive stars? Not quite. Many assumptions and simplifications—the initial 1D models, the 3D octant of the star, to name a few—were made. But while these new models were necessarily contrived, given the limits of today’s computational brawn, they are still an instructive demonstration that the turbulent environments in which the cores of massive stars breathe their last can affect how the rest of the star’s death plays out. | 0.84619 | 3.986312 |
Moon ♋ Cancer
Moon phase on 21 December 2094 Tuesday is Full Moon, 14 days old Moon is in Gemini.Share this page: twitter facebook linkedin
Moon rises at sunset and sets at sunrise. It is visible all night and it is high in the sky around midnight.
Lunar disc appears visually 5% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1855" and ∠1951".
The Full Moon this days is the Cold of December 2094.
There is high Full Moon ocean tide on this date. Combined Sun and Moon gravitational tidal force working on Earth is strong, because of the Sun-Earth-Moon syzygy alignment.
The Moon is 14 days old. Earth's natural satellite is moving through the middle part of current synodic month. This is lunation 1174 of Meeus index or 2127 from Brown series.
Length of current 1174 lunation is 29 days, 13 hours and 43 minutes. It is 1 hour and 48 minutes longer than next lunation 1175 length.
Length of current synodic month is 59 minutes longer than the mean length of synodic month, but it is still 6 hours and 4 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠287.7°. At the beginning of next synodic month true anomaly will be ∠317.1°. 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°).
8 days after point of perigee on 13 December 2094 at 11:23 in ♓ Pisces. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 6 days, until it get to the point of next apogee on 28 December 2094 at 08:42 in ♍ Virgo.
Moon is 386 427 km (240 115 mi) away from Earth on this date. Moon moves farther next 6 days until apogee, when Earth-Moon distance will reach 404 647 km (251 436 mi).
Moon is in ascending node in ♊ Gemini at 16:09 on this date, it crosses the ecliptic from South to North. Moon will follow the northern part of its orbit for the next 14 days to meet descending node on 5 January 2095 at 02:54 in ♐ Sagittarius.
At 16:09 on this date the Moon is completing its previous draconic month and is entering the new one.
11 days after previous South standstill on 9 December 2094 at 16:27 in ♑ Capricorn, when Moon has reached southern declination of ∠-24.130°. Next day the lunar orbit moves northward to face North declination of ∠24.122° in the next northern standstill on 22 December 2094 at 16:45 in ♋ Cancer.
The Moon is in Full Moon geocentric opposition with the Sun on this date and this alignment forms Sun-Earth-Moon syzygy. | 0.847411 | 3.064162 |
May 7 The US space agency NASA revealed on Monday details about its plan to hit a small moonlet target in a double asteroid system with a spacecraft in 2022, its first mission to demonstrate a planetary defence technique.
The asteroid, called Didymoon or Didymos B, is a moon asteroid around 150 meters tall orbiting a larger body Didymos A, the most accessible asteroid of its size from the Earth, the Xinhua news agency reported.
An international campaign is now making observations using powerful telescopes worldwide to understand the state of the asteroid system.
“The Didymos system is too small and too far to be seen as anything more than a point of light, but we can get the data we need by measuring the brightness of that point of light, which changes as Didymos A rotates and Didymos B orbits,” said Andy Rivkin, a co-lead of the investigation team.
Researchers are still not sure about the target’s composition: whether it is composed of solid rock, loose rubble or “softer” sand. A softer surface would absorb much of the impact force and may not be pushed as drastically as if a spacecraft hit a harder surface.
But the NASA team will eventually see the asteroid system close-up thanks to an Italian-made imager. The shoebox-sized cube satellite will record the spacecraft’s impact and its aftermath.
The spacecraft called Double Asteroid Redirection Test (DART) will carry an optical navigation system to capture images that help the spacecraft reach its target.
In its latest design, DART spacecraft will be able to move by relying on small hydrazine thrusters while utilising the electric propulsion system, which will push the start of the primary launch window to July of 2021, shortening the mission flight time. Its previous planned launch time was December 2020.
The DART spacecraft will crash itself into the asteroid at a speed of approximately six kilometer per second and the collision will change the speed of the moonlet in its orbit around the main body by a fraction of one per cent, enough to be measured using telescopes on the Earth, according to the NASA. | 0.824139 | 3.047719 |
Image of Newborn Planet
SPHERE, a planet-hunting instrument on ESO’s Very Large Telescope, has captured the first confirmed image of a planet caught in the act of forming in the dusty disc surrounding a young star.
Astronomers led by a group at the Max Planck Institute for Astronomy in Heidelberg, Germany have captured a spectacular snapshot of planetary formation around the young dwarf star PDS 70. By using the SPHERE instrument on ESO’s Very Large Telescope (VLT) — one of the most powerful planet-hunting instruments in existence.
The SPHERE instrument also enabled the team to measure the brightness of the planet at different wavelengths, which allowed properties of its atmosphere to be deduced.
The planet stands out very clearly in the new observations, visible as a bright point to the right of the blackened centre of the image. It is located roughly three billion kilometres from the central star, roughly equivalent to the distance between Uranus and the Sun. The analysis shows that PDS 70b is a giant gas planet with a mass a few times that of Jupiter. The planet's surface has a temperature of around 1000°C, making it much hotter than any planet in our own Solar System. | 0.864681 | 3.215574 |
Planetary science is the science of planets or planetary systems, including the Earth and our solar system. Planets and planetary systems, including the central stars, are the most important foundation for life to be generated and sustained. Any search for extraterrestrial life forms would focus on finding a planet bearing air and water and orbiting around a star. Whether the Earth is a special planet formed almost miraculously fit for life or there are many Earth-like planets around other stars has been a long-pursued question. Planetary science may eventually be able to give an answer to this question.
Research tends to be done by a combination of astronomical observations, space exploration (particularly unmanned space missions), examinations of meteorites and interplanetary dust particles, experiments using those planetary materials or stimulants, theory and modeling, and considerable use of computer simulation. Planetary science studies objects ranging in size from nanometer-size crystals to gas giants, observing their composition, dynamics, and history.
Planetary science mainly originated from a subfield of astronomy, which deals with celestial bodies inside our solar system. Unlike the mainstream astronomy that mainly deals with gas and plasma, planetary science deals with solid materials, and thus expanded its field by incorporating an interdisciplinary approach. Planetary science draws from diverse sciences and may be considered a part of the Earth sciences, or more logically, as its parent field because the Earth is also a planet.
The most significant year in that respect is 1969, when three significant events occurred that shaped the formation of today’s planetary science. A Japanese expedition found a concentration of meteorites at the foot of the Yamato Mountain Range in Antarctica in 1969. Since then, expeditions by Japan, the U.S., and other countries found many such sites, collecting tens of thousands of meteorites. In the same year, two large meteorites fell. They are called Allende and Murchison meteorites, which belong to a rare group of meteorites called carbonaceous chondrites. Also in 1969, Apollo 11 landed on the Moon and recovered samples of lunar rocks and soils.
The Lunar Science Conference was held in Houston in 1970 to gather research results on the lunar samples. Since then, it has been held every year and was later renamed as the Lunar and Planetary Science Conference (LPSC). The LPSC has greatly helped the formation and development of planetary science.
When the discipline concerns itself with a celestial body in particular, a specialized term is used, as shown in the table below (only Heliology, Earth science (synonymous with geoscience), Selenology, and Areology are currently in common use):
|Body||Term||Source of root in term|
|Earth||Earth science (geoscience)||Greek Gaia|
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Note: Some restrictions may apply to use of individual images which are separately licensed. | 0.872161 | 3.814435 |
Contact: Paul Preuss
Dark energy appears to account for over three-quarters of the stuff in the Universe, and it’s pushing all the rest – ordinary matter and dark matter – farther apart at an ever-increasing rate. But what is dark energy? Although theories abound, the short answer is that nobody knows.
We know it exists because of an experimental technique that uses specific types of exploding stars, or supernovae, as “standard candles.” A dozen years ago measurements of these supernova at increasing distances from Earth led to the unexpected discovery of dark energy; observations of supernovae continue to increase in power and precision in ongoing studies.
Independent evidence from measurements of the cosmic microwave background and other estimates of the matter density of the Universe provided early support for the radical idea of dark energy. Newer and quite different techniques, including weak lensing and baryon acoustic oscillations, are now poised to offer unique insights into what Nobel Prize-winner Frank Wilczek has called “the most fundamentally mysterious thing in basic science.”
Type Ia Supernovae: The Best Standard Candles
During the 1980s and 90s, the Supernova Cosmology Project (SCP), co-founded by Saul Perlmutter and Carl Pennypacker and based at Berkeley Lab, demonstrated that Type Ia supernovae were excellent standard candles for measuring the expansion history of the Universe. Although the idea had been circulating within the astronomical community for years, says Perlmutter, a Berkeley Lab astrophysicist and professor of physics at UC Berkeley, “In the early days, people thought measuring expansion with supernovae would be too hard.”
The SCP went on to show that distant supernovae, short-lived and unpredictable as they are, can nevertheless be collected “on demand,” allowing observers to schedule telescope time in advance and accumulate enough data to make confident estimates of expansion.
“In retrospect it seems obvious, but we realized that the whole process could be systematized,” Perlmutter explains. “By searching the same group of galaxies three weeks apart, we could find supernovae candidates that had appeared in the meantime. We could guarantee four to eight supernovae each time, and all of them would be on the way up” growing brighter instead of already fading.
Type Ia supernovae are among the brightest things in the Universe; what’s more, they are all almost the same brightness, with differences that can be standardized to less than 10 percent. Thus a supernova’s apparent brightness shows how far away it is and, because light takes time to travel, how far back in time it exploded.
The supernova’s redshift – the shifting of spectral lines (signals of specific elements in the exploding star) toward the red end of the spectrum – is a direct measure of how much the space through which the light has traveled has stretched.
The idea is simple on paper: by comparing brightness to redshift for numerous Type Ia supernovae, from nearby to very distant, an observer can tell how the rate of expansion of the Universe has changed over time.
Members of the Supernova Cosmology Project expected to find, as did their rivals in the High-Z Supernova Search Team, that the farther away (the farther back in time) a supernova was, the brighter (closer) it would appear relative to its redshift — an indication that expansion has been slowing. Instead both teams found the opposite.
“The chain of analysis was long, and the Universe can be devious, so at first we were reluctant to believe our result,” Perlmutter explains. “But the more we analyzed it, the more it wouldn’t go away.”
Perlmutter described the evidence for accelerating expansion at an American Astronomical Society meeting in January 1998. At first both teams thought the cause was a form of Einstein’s “cosmological constant,” assumed to be an unknown form of energy that uniformly, as its name suggests, counteracts the mutual gravitational attraction of the matter in the cosmos.
But within weeks a flurry of alternative explanations and theories were put forth, including ideas for a dynamical, not constant, form of energy, or for an odd cosmos in which our Universe bounces back and forth between expansion and contraction — or perhaps most radical of all, that Einstein’s General Theory of Relativity, the best explanation of gravitation we have, is flawed.
One way to sort out some of these competing theories is to collect a much larger sample of supernovae and measure them with greater precision. That way, scientists would be able to tell whether dark energy has indeed been constant and expansion has followed a smooth curve, or whether at different eras expansion has proceeded faster or slower than at present, and dark energy is dynamic.
To gather a lot more supernovae, especially more distant supernovae, it’s necessary for a telescope to escape the limitations of Earth’s atmosphere. In 1999, Berkeley Lab physicists and astronomers formed an international collaboration to design the SuperNova/Acceleration Probe (SNAP), a satellite dedicated to the study of dark energy. In 2003 the U.S. Department of Energy (DOE) and NASA formed the Joint Dark Energy Mission (JDEM) and solicited additional ideas. The DOE JDEM Project Office is located at Berkeley Lab.
Better measurements of Type Ia supernovae require reducing or eliminating uncertainties in measuring their brightness and spectra. Brighter Type Ia supernovae wax and wane more slowly than fainter ones, for example, but when these individual “light curves” are stretched to fit the norm, and brightness is scaled according to the stretch, most can be made to match. This “classic” method has been used to standardize intrinsic brightness to within 8 to 10 percent.
To reduce these error bars and other uncertainties, more high-quality spectra are needed, beginning with “nearby” supernova, those whose spectra have not been shifted so far into the red that parts are hard to recover or no longer visible. Since its founding in 2002, the Nearby Supernova Factory (SNfactory), a collaboration of Berkeley Lab, a consortium of French laboratories, and Yale University, has amassed an enormous database of some 2,500 spectra.
With this data, SNfactory researcher Stephen Bailey found that simply by measuring the ratio of brightness between two specific regions in the spectrum of a Type Ia supernova taken on a single night, that supernova’s distance can be determined to better than 6 percent uncertainty.
Berkeley Lab cosmologist Greg Aldering, a founder and leader of the SNfactory, says, “This is an example of exactly what we designed the Nearby Supernova Factory to do. It underlines the vital role of detailed spectrometry in discoveries of cosmic significance.”
But supernovae alone cannot provide the whole answer. Baryon acoustic oscillation is a new technique that provides a “cosmic ruler” to measure the expansion history of the Universe. Read on>
How dark energy was discovered is discussed in http://www.lbl.gov/Science-Articles/Archive/sabl/2007/Nov/darkenergy1.html (part 1); http://www.lbl.gov/Science-Articles/Archive/sabl/2007/Nov/darkenergy2.html (part 2); and http://www.lbl.gov/Science-Articles/Archive/sabl/2008/Feb/dark-energy.html (part 3).
How supernovae are used to measure dark energy is discussed in detail in http://www.lbl.gov/Science-Articles/Archive/sabl/2005/October/04-supernovae.html (part 1); http://www.lbl.gov/Science-Articles/Archive/sabl/2005/November/04-supernovae-2.html (part 2); and http://www.lbl.gov/Science-Articles/Archive/sabl/2006/Jan/05-supernovae-pt3.html (part 3). | 0.857113 | 4.132161 |
The Wealth of the Universe: Gold in Space
Modern scientific theory states that gold, as a chemical element, was formed as a result of the destruction of neutron stars. During the explosion of a neutron star, the dust that contains a precious metal is emitted in the outer space, where it then becomes condensate and settles on asteroids.
Space researchers manage to make amazing gold-related discoveries. We tell interesting facts about the discovery of the yellow metal in our galaxy.
Quadrillion dollars for an asteroid
The giant asteroid 16 Psyche was discovered in 1852 by the Italian astronomer Annibale de Gasparis. This is one of the largest space objects of the asteroid belt — the region of the Solar System located between the orbits of Mars and Jupiter.
16 Psyche is a fragment of the planet’s core, previously existed between the two celestial bodies. According to scientists, the asteroid is composed of 90% of rare metals. The diameter of 16 Psyche is 252 kilometers.
Its formation is the result of the fusion of several neutron stars, as a consequence of which a huge amount of gold was formed on the asteroid, ten times greater than the terrestrial reserves. Modern scientists have concluded that the amount of the precious metal in 16 Psyche is enough to satisfy the needs of all mankind.
This space object costs more than the entire economy of our planet, estimated at 78 trillion dollars. The asteroid contains precious metals, including gold, worth of up to 10 quadrillion dollars.
In the photo: a computer image of the asteroid 16 Psyche.
Gold Cosmic Fever
In 2014, a research team from the University of Arizona presented a project of the scientific mission to 16 Psyche. Scientists proposed to send a robotic probe to study the biochemical composition of the asteroid within the period of six months. In early 2017, the National Aeronautics and Space Administration approved this project.
With the help of this experiment, NASA employees want to learn more about the asteroid for possible mining of the precious metal. This is the first step of scientists in this direction and, perhaps, the beginning of a new era in gold mining. In 2016, the agency provided data according to which it is possible to develop and deliver minerals from asteroids to Earth. This is possible due to the existing technologies and will not require an industrial revolution to happen.
The National Aeronautics and Space Administration approved the terms of the scientific mission to the "precious" space object — the research machinery will head to 16 Psyche in 2022. The space probe will undertake a near-Earth gravitational maneuver, flying by Mars and arriving to the asteroid by 2026.
According to NASA, the space "gold rush" is expected to occur within the next 30 years.
The precious celestial body
In 2011, the scientists at the Haleakala Observatory in Hawaii, USA, discovered a large asteroid flying near the Earth, which allowed researchers to study it profoundly. The near-Earth object, named 2011 UW158, has a diameter of 300 meters and constitutes a rotating oblong asteroid.
According to preliminary estimates of specialists, this space object can contain precious metals worth of 300 billion to 5 trillion dollars.
Our galaxy is full of gold-bearing bodies. We just need to use the advanced space technologies that allow us to mine gold in space and deliver it to Earth.
Purchase gold bars in our online store!
Build your financial security! | 0.829821 | 3.281474 |
Is the universe expanding from a Big Bang or is it a misinterpretation of the redshift of light?
The Big Bang and the expanding universe probably are illusions that fit the progressive agenda of an ever evolving universe.
It also closes the door on the infinite series of cause and effect that requires a first cause outside the system to get it started, aka God/ creator/ overarching, pre-existing force. If time itself began with the Big Bang, there can be no “before,” thus cutting off any consideration of a first cause.
The Big Bang theory is based on three things:
1.) An interpretation of the redshift of light from other galaxies as speed of recession,
2.) One of many solutions to Einstein’s field equations that favored an expanding universe. Einstein’s own solution included a cosmological constant that resulted in a non-expanding universe.
3.) The Cosmic Microwave Background (or CMB) interpreted as the far red shifted afterglow of the Big Bang.
Redshift is really the shift of the dark absorption lines of elements to longer, redder, wavelengths. Hydrogen is usually used because of its abundance.
Before discussing redshift to distance let me set the stage. It’s the 1920s.
Before telescopes were powerful enough to see individual stars in other galaxies, our galaxy was assumed to be the entire universe and galaxies were assumed to be clouds of glowing gas called nebulae (meaning clouds) within our galaxy.
We now estimate there are over 100 billion galaxies in the observable universe.
Cepheid variable stars with the same variability period had been determined to be the same brightness everywhere, which made them a “standard candle” to determine distance, first in our galaxy and then in other galaxies. When individual stars were first seen in other galaxies, using the most powerful telescope of the time, nebulae were identified as other “island universes,” aka galaxies.
Redshift of stars in our galaxy were determined to be caused by their speed moving away from us. The faster, the greater the redshift by the Doppler Effect, where light is “stretched” by the speed of the source.
Redshifts in nebulae (nearby galaxies) were known to be greater than redshifts within our own galaxy.
Edwin Hubble discovered the red shift to distance relationship for nearby galaxies, based on Cepheid variable stars within them. By this he calculated that farther is redder.
Because the redshift from nearby stars in our galaxy had been recognized as indicating their speed away from us, this new redshift was assumed to mean speed of recession of galaxies.
Hubble noted that the redshift to distance relationship was only linear if he assumed fixed, not receding galaxies.
He was also uncomfortable with the extreme speeds calculated from redshift which were rapidly approaching the speed of light with increasing distance.
His redshift to distance calculations resulted in very small universe with a “Big Bang” point of origin only 2 billion years ago, which is less than the calculated age of the earth at 4.5 billion years. Later adjustments extended it to 13.7 years ago, which is still only 3 times the age of the earth.
He spent the rest of his life trying to convince others that they were wrong about redshift meaning speed of recession.
Today’s redshift calculations exclude nearby galaxies as being affected by gravity of the Local Group of galaxies.
Cosmological and relativistic terms have been added to the calculations, so the relationship is no longer linear
A redshift of 1, as a simple ratio, is equal to the speed of light; we now have redshifts greater than 8.
This made it necessary for cosmologists to assume that space itself between galaxies is expanding faster than the speed of light, the upper limit of speed for ordinary matter.
Fritz Zwicky, a contemporary of Hubble, proposed that the red shift is from loss of energy by gravitational interaction over time that fits observations better than other non-speed related theories.
To be a valid theory, the redshift must occur uniformly for the entire spectrum and not blur or obscure distant objects by scattering light. All theories based on repeated collisions in space do not fit these requirements.
History rewritten: Modern cosmologists claim Zwicky’s theory was about collisions. His original paper discussed collision related theories and eliminated them in favor of gravitational influence over time and distance.
More recently Steven Weinberg and others have raised speculation that mirrored Zwicky’s theory of gravitational influence over time causing red shifts, but they were not ready to abandon the expanding universe paradigm.
“The frequency of light is also affected by the gravitational field of the universe, and it is neither useful nor strictly correct to interpret the frequency shifts of light…in terms of the special relativistic Doppler effect.” Steven Weinberg and Jaylant Narlikar and John Wheeler, quoted in “Galaxy Redshifts Reconsidered,” by Sten Odenwald and Rick Fienberg, Sky &Telescope, February 1993 issue.
The Cosmic Microwave Background (CMB) is interpreted as the far red shifted afterglow of the Big Bang. However, the temperature of thinly dispersed matter in space as a result of residual starlight was earlier calculated and predicted by Guillaume, (5 K < T < 6 K),26 Eddington, (T = 3.1 K), Regener and Nernst, (T = 2.8 K), McKellar and Herzberg, (T = 2.3 K), Finlay-Freundlich and Max Born, (1.9 K < T < 6.0 K) based on a universe in dynamical equilibrium without expansion. Penzias and Wilson experimentally found the cosmic microwave background radiation to be consistent with a temperature of 2.7 K. Gamow, who had claimed to be the originator of the Big Bang Theory, also erroneously claimed he had been the first to predict the background temperature and claimed the result as evidence for the Big Bang. However, his estimate was not only not the first, but was 7 K with an upper limit of 50K.
Did Einstein really say his cosmological constant (for a non-expanding universe) was his biggest mistake?
The so-called Einstein quote that his cosmological constant was the “biggest blunder” of his life was only claimed by George Gamow in 1970, 15 years after Einstein died.
Einstein’s friends and research associates denied it but claimed that, if he said it, it was a joke. (the polite way to avoid calling Gamow a liar.)
Conclusion: If the universe is not expanding from a Big Bang, it can be far larger and much older than the Big Bang theory allows. The observable universe, observed back to approx. 13.5 billion years, may be a small corner of a much grander universe, which could allow more time for formation of galaxies and larger structures without the proposed dark matter influence. Exotic inventions such as expanding space, dark energy and dark matter may not be necessary. Recent work using near-infrared data from the Spitzer space telescope to more accurately estimate mass of numerous galaxies explains galaxy rotation speeds without resorting to exotic dark matter.
Original Report: “On the Red Shift of Spectral Lines Through Interstellar Space,” By F. Zwicky, Norman Bridge Laboratory Of Physics, California Institute Of Technology, August 26, 1929
History of the 2.7 K Temperature Prior to Penzias and Wilson” A. K. T. Assis, Instituto de Fisica “Gleb Wataghin” Universidade Estadual deCampinas 13083-970 Campinas, Sao Paulo, Brasil M. C. D. Neves Departamento de Fisica Universidade Estadual de Maringa 87020-900 Maringa, PR, Brasil
“The Radial Acceleration Relation in Rotationally Supported Galaxies,” by Stacy S. McGaugh and Federico Lelli, Department of Astronomy, Case Western Reserve University, James M. Schombert, Department of Physics, University of Oregon (Dated: September 21, 2016) arXiv: 1609.05917v1 astro-physics. GA
Want to know more about this and other Modern Myths including climate change, evolution, origin of life or quantum physics? See related posts on this website or buy the book Perverted Truth Exposed: How Progressive Philosophy Has Corrupted Science in print or as e-book/Kindle on line at WND Superstore (the publisher) or at Amazon, Books-a-Million or Barnes & Noble . | 0.866032 | 3.885564 |
Naturally-occurring particle accelerators function throughout the universe all the time, perpetually manifesting in energetic outbursts and other events that reveal a universe far more dynamic than our perception would lead us to believe. These natural accelerators are exploded stars, quasars, and black holes that continually send cosmic messengers our way.
Buried a few kilometres deep in the ice at the South Pole in Antarctica lies IceCube, a telescope, perhaps an unconventional one, consisting of 86 vertical strings, each instrumented with 50 optical modules that are positioned 17 metres apart. The vertical strings are lowered into holes made using a hot water drill technology that employs a 2500-metre high-pressure hose that delivers water to a drill head at a near boiling temperature of 90 °C. The holes are essentially melted into the ice, becoming holes filled with water, which then rises to the level of the ice. After the vertical strings are positioned, the water then freezes, installing the optical modules firmly in place.
IceCube serves to detect high-energy cosmic neutrinos which string through our planet from supernovae and gamma ray bursts. Neutrinos are particles that travel at the speed of light and that have no electric charge and hardly no mass. They do not interact with the electromagnetic force and thus essentially pass through matter unimpeded. In fact, each second, 65 billion neutrinos pass through every square centimetre of your body! Our whole planet is bombarded by an ocean of neutrinos, albeit unnoticeably. However, neutrinos may have played a very important role in the evolution of the early universe and as such, understanding them will allow us to essentially “peer into” stars and any other cosmic phenomena from which neutrinos are emitted.
Since neutrinos are very hard to detect and have a very low interaction probability, very few of the neutrinos out of the millions stringing through will occasionally interact with an atom. Accordingly, for a neutrino detector, one would need a large enough bulk of matter. To cut down on cost, IceCube makes use of the Antarctic ice, effectively employing it as a medium (1 cubic kilometre is occupied) in order to study collisions between neutrinos and the ice atoms. Antarctic ice makes an excellent medium because it is free of radiation and is transparent.
The method of detection is to employ the optical modules in IceCube to detect blue flashes of Cerenkov light – this is emitted when a neutrino interacts with subatomic particles in the ice and gets converted into a high energy muon, moving faster than light and creating these flashes as a result.
We can, accordingly, infer the source of the neutrino from the direction of the muon beam since the direction of the resulting muon beam is retained as the same direction of the neutrino beam. Since muons can also be produced by cosmic ray showers in the atmosphere, this technique is used to differentiate between cosmic ray muons and neutrino muons. In essence, the atmospheric cosmic ray muons (downwards-moving) are singled out and filtered while the neutrino muons (upwards-moving and passing through the Earth) are selected. Therefore, the Earth is employed as a shield since it absorbs the incident flux of atmospheric muons (the atmospheric muons do not penetrate the Earth). Only muons below the telescope are detected.
35,000 neutrinos were detected between May 2010 – May 2012, 20 of which are likely extragalactic neutrinos – with energies of the order of 100 million million electron volts which is suggestive of a cosmic origin!
There is perhaps no doubt that IceCube will usher in a new age of neutrino astronomy, revolutionize particle physics, and refine our understanding of our very mysterious universe. The search for elusive neutrinos is underway and it is quite astronomically exciting what the largest neutrino observatory ever built will unravel!
Featured image courtesy of: IceCube Collaboration. IceCube Lab in the South Pole. | 0.853765 | 4.097804 |
Some practically ancient technology has recently been used to rule out some exotic theories of physics. The Pioneer 10 and 11 probes, which were the first successful space missions to Jupiter and Saturn, respectively, have still provided data since their launch in the 1970s. After the Pioneers observed their target planets, they still transmitted radio signals back to Earth, and NASA would also try to bounce radio waves off the probes. Similar to how you can tell if an ambulance or train is rushing towards you or moving away by the change in pitch, NASA could use the Doppler effect to measure the velocity of the probes along their paths.
Astronomers wanted to use this data to study the influence of gravity farther out in the solar system, where the mass of the Sun and outer planets wouldn’t overwhelm smaller effects. Of course, studying “small effects” in deep space required accounting for many variables. John Anderson, the lead analyst of the Doppler data, started to notice small differences between his model’s predictions and the Pioneers’ actual velocity and position data beyond Neptune’s orbit. The probes were experiencing a small acceleration towards the Sun, slowing them down. By small, they mean really small: the acceleration was calculated as being 8.74 x 10-10 meters per second per second. (To help put that in context, it would take over 400 years of constant acceleration of that amount to get up to the average person’s walking speed)
For the probes to be experiencing that acceleration means they need to be experiencing some sort of force. Anderson’s team originally wrote it off as unexpected gas leaks from the Pioneers’ thrusters. But the anomalous acceleration persisted even after the thrusters should have run out of fuel. And that started to concern astronomers. Anderson’s model accounted for all known gravitational sources in the outer solar system, and even more complicated effects such as radiation pressure from the Sun. So something astronomers didn’t know about must have been the cause of the anomaly.
Astronomers and physicists have come up with dozens of interesting explanations for the Pioneer anomaly that would change our understanding of the universe. Some have proposed previously unknown clusters of dark matter in the solar system, but this was ruled out when the Voyager probes never showed this acceleration and our models of planetary orbits never showed such problems. Others proposed rewriting gravity. Ironically, an alternative theory to dark matter, known as Modified Newtonian dynamics (or MOND) was also invoked to explain the anomaly, as it proposes that gravity behaves differently at extremely low accelerations (intriguingly, also on the order of 10 to -10 meters per second per second). Others proposed that time passed at different rates for objects depending on their acceleration through the gravitational field of space, and Anderson’s group actually considered these theories for a while (in some way I truly don’t understand).
And others proposed less exciting explanations. Tiny amounts of gas could be produced and leak from the Pioneer’s nuclear power sources. And some thought even the tiny amounts of heat radiating off the probes could cause push the probes off course. No one seems to have taken the gas theory very seriously. And Anderson’s team (now working with Slava Turyshev) wrote off the heat theory in the early 2000s, saying any force based on the heat should have decreased with distance from the sun.
Viktor Toth, a programmer who seems to do theoretical physics in his free time (seriously), helped change their minds. Toth argued that Anderson’s team couldn’t rule out thermal effects unless they did a detailed analysis. In an interesting story showing the merits of preserving old research data, Toth helped Turyshev save or find copies of nearly all the Pioneer mission’s Doppler and temperature telemetry. Somewhat amazingly, the team (now with Toth) managed to recreate a full CAD model of Pioneer 10 based on the original engineering drawings and using the temperature data, ran a computer simulation measuring the thermal emissions in all directions. Their model showed that the radiation could be responsible for all but about 20% of the acceleration.
The model seems pretty convincing. But their figures look like they show the “thermal recoil” effect decreasing further from the sun, while the anomaly still seems constant. So maybe there’s still room for some anomalous physics. | 0.888289 | 4.046711 |
This is not a Birkeland Current
Posted on February 18, 2013
by Mel Acheson
Filaments of dust obscure starlight near the center of the Milky Way. Credit: ESO
Feb 19, 2013
It twists like a Birkeland Current; it’s stringy like a Birkeland Current; it’s dense like a Birkeland Current; but Everyone Knows (if they want to pursue a career in astronomy) that There is No Such Thing as Electricity in Space.
The press release
for this new image of the Pipe Nebula recalls René Magritte’s painting of a pipe, on which he painted “Ceci n’est pas une pipe” (“This is not a pipe”). His point was that the image was not the thing. Images must be interpreted.
Aah! says the canny epistemologer, but so must sensory impressions be interpreted: even “the thing” is an interpretation in reference to some general, usually preconceived, ideas about the context (aka a theory). We become so used to interpreting things according to our familiar and habitual preconceptions that we are unaware we’re interpreting. “Obviously” (the word of the day for the unexamined mind), it’s gravity, what else could it be period. Modern consensus astronomers seem to miss that point.
Interpreted in conformity with consensus astronomy, this is another “dark” thing to display on their shelf of dark things: dark matter, dark energy, and really-really dark holes. It’s “a vast dark cloud of interstellar dust.” It’s “so thick it can block out the light from the stars beyond.” “The dust and gas will clump together under the influence of gravity and more and more material will be attracted until the star is formed.”
Did you notice the preconceived idea that darkened the interpretation? “[U]nder the influence of gravity.” Anyone familiar with Alfvén’s work might have added “or electricity,” thereby admitting a twinkle of scientific provisionality into the darkness of the Closed Gravitational Mind.
The preconceived idea of the Electric Universe is, of course, a Birkeland Current. It does have a few characteristics to recommend it: The z-pinch force along a current will attract material almost like gravity does, but with important exceptions: The z-pinch force is cylindrical, not spherical (hence attracting material into filaments). It’s also more powerful, declining with the first power of the distance, not the square. The double layers that form along the boundaries of the currents tend to produce sharply defined edges on the filaments. And it has been observed in laboratory settings to trigger instabilities that might be interpreted as star-like.
But such an idea is…unfamiliar. Maybe we can call it a “dark” idea.
Mel AchesonThis is not a Birkeland Current | thunderbolts.info
DB (please excuse the lengthy article)
I wonder what the vacuum is around that immense carpet sweeper? | 0.8871 | 3.548295 |
eso0040 — Tiskové zpráva (vědecká)
The VLT Weighs the Invisible Matter in the Universe
Shapes and Orientations of 76,000 Distant Galaxies
1. prosince 2000
An international team of astronomers has succeeded in mapping the "dark" (invisible) matter in the Universe, as seen in 50 different directions from the Earth. They find that, within the uncertainty, it is unlikely that mass alone would stop the current expansion of the Universe. This fundamental result is based on the powerful, but challenging method of "cosmic shear". It depends on very accurate measurements of the apparent, weak distortion and preferential orientation of images of distant galaxies. This effect is caused by deflection of the light from those galaxies by the large mass concentrations in the Universe it encounters on its way to us. The larger these masses are, the larger are the apparent image distortions and the more pronounced are the alignments of neigbouring galaxy images. The new analysis was made possible by means of unique observational data, obtained under excellent conditions with the the ESO 8.2-m VLT ANTU telescope and the multi-mode FORS1 instrument at the Paranal Observatory.
The VLT Observations
An international team lead by astronomers at the Institut d'Astrophysique de Paris used for the first time the VLT to probe the mass density of dark matter in the Universe, by means of weak gravitational lensing effects.
The team selected 50 different sky fields which were then observed in service mode by the ESO staff at the Paranal Observatory. Long exposures of these fields were made with the FORS1 instrument (in its imaging mode) on the VLT 8.2-m ANTU telescope and only during nights with the very best observing conditions. In fact, 90% of the fields have image quality better than 0.65 arcsec, guaranteeing a superb basis for the subsequent study.
Clumps of dark matter
The unprecedented quality of these data enabled the astronomers to measure the shapes and orientations of the images of more than 70,000 galaxies with very high precision. After a careful statistical analysis, they were able to demonstrate that the distant galaxies are not randomly oriented on the sky - they show a a certain degree of alignment over substantial sky areas (to distances of several arcmin)
The astronomers refer to this as a coherent orientation. It can only be explained by gravitational lensing effects produced by clumps of dark matter in space, distributed along huge "filaments". ESO Press Photo eso0040 demonstrates this, by means of the VLT exposure (right) and the deduced mass distribution in the same direction, based on these measurements.
The weak lensing effect
The gravitational lensing effect was predicted by Einstein's theory of general relativity at the beginning of the century.
When the light of a distant galaxy passes close to a concentration of matter in space, it will be (more or less) deflected, due to the effect of the field of gravity of this matter. The observed image of the galaxy is therefore distorted.
Very strong gravitational lensing effects (by very heavy objects) produce spectacular gravitational arcs observed in some rare clusters of galaxies, cf. the VLT images of CL2244-0 and Abell 370.
Much weaker lensing effects (by less massive objects) are in fact present everywhere in the Universe, but they are not easy to detect. This was the effect the astronomers searched for. It manifests itself as a small stretching in a particular direction of the images of all galaxies that are located behind the gravitational lens. This phenomenon may then be observed as an alignment of galaxies in that particular sky area. The existence of the lens and its overall mass and extension can then be determined, albeit with some uncertainty only.
An important contribution to the map of the Universe
Thanks to the large light collecting power of the VLT and the superb quality of the present images, the team succeeded in detecting large-scale, weak lensing effects in the Universe, in a large number of different (and thus independent) directions. Moreover, the analysis of this large data sample enabled the astronomers, for the first time, to set limits to the overall mass density of the universe, by means of the gravitational lensing by large scale structures. It turns out that their results are in remarkable agreement with the current constraints obtained by other cosmological considerations.
This kind of investigation is rather difficult and cannot be based on individual sky fields alone. The final result, in terms of the inferred mass density of the Universe, only emerges when "adding" all of the 50 observed fields.
Making the reasonable assumption that the distribution of galaxies and dark matter in space is similar, the new investigation shows that the total matter density is less than half of what is needed to stop the current cosmic expansion. The new result also supports the existence of a non-zero "cosmological constant" (vacuum energy), already indicated by supernova observations, cf. eso9821.
In the ongoing quest for establishing the first true mass map of the Universe from the gravitational lensing effects caused by this mass, the VLT has now demonstrated its great potential with bravour.
The light collecting power and, not least, its excellent image quality provides what is likely to be the best observing configuration for this very challenging research programme. It was also made possible because of the opportunity to use the VLT Service Mode during which ESO staff astronomers at Paranal are responsible for carrying out the actual observations, at the moment of the very best atmospheric conditions.
: The team consists of Yannick Mellier (Principal Investigator [PI]; Institut d'Astrophysique de Paris [IAP] and Observatoire de Paris/DEMIRM [OP-DEMIRM], France), Ludovic van Waerbeke (co-PI, IAP), Roberto Maoli (IAP, OP-DEMIRM and University La Sapienza, Rome, Italy), Peter Schneider (University of Bonn, Germany), Bhuvnesh Jain (John Hopkins University, Baltimore, USA), Francis Bernardeau (Service de Physique Theorique, C.E. de Saclay, France), Thomas Erben (Max Planck für Astrophysik, Garching, Germany, IAP and OP-DEMIRM) and Bernard Fort (IAP).
The research described in this Press Release is reported in a research article ("Cosmic Shear Analysis in 50 Uncorrelated VLT Fields. Implications for Omega-0 and sigma-8."), submitted by the team to the European journal "Astronomy and Astrophysics". Note also the related article in the ESO Messenger (No. 101, p. 10-14, September 2000).
Institut d'Astrophysique de Paris
Ludovic van Waerbeke
Institut d'Astrophysique de Paris
University La Sapienza; p.t. Institut d'Astrophysique de Paris | 0.851982 | 4.037224 |
2014 Annual Science Report
Arizona State University Reporting | SEP 2013 – DEC 2014
Habitability of Water-Rich Environments - Task 5 - Evaluate the Habitability of Small Icy Satellites and Minor Planets
We constrained conditions of formation of silica phases in putative aqueous systems within the Saturn’s icy moon Enceladus, and evaluated the composition of aqueous fluids formed during thermal evolution and rock dehydration of the dwarf planet Ceres.
A detection of silica (SiO2) nano-size particles in the saturnian system with the Cassini spacecraft may indicate aqueous processes on the icy moon. Zolotov constrained physical-chemical conditions of silica formation in aqueous systems on Enceladus. The work shows that the concentration and speciation of Si-bearing solutes are mostly controlled by solubilities of secondary clay minerals in altered chondritic rocks. The concentration of dissolved SiO2 gradually increases with temperature and is not very sensitive to the pressure and redox state of the system. The work showed that aqueous alteration of carbonaceous chondritic materials forms fluids which are strongly undersaturated with respect to SiO2 phases, consistent with observations in chondrites. It was shown that cooled fluids remain undersaturated with respect to amorphous silica. Freezing or evaporation of SiO2-undesaturated chondritic fluids could be needed to precipitate silica phases. The detection of silica phases in the saturnian system indicates aqueous process within Enceladus but may not indicate high-temperature aqueous environments.
Zolotov and Mironenko modeled a global-scale non-isochemical alteration of the dwarf planet Ceres during its thermal evolution. They evaluated the phase composition in warmed Ceres’ interior, the upward transfer of fluids formed through dehydration of minerals, and the accumulation of water mantle (ocean). The calculations led to compositional and density profiles together with masses and volumes of all constituents (rocks, minerals, pore fluids, and water mantle) and the whole body. The models demonstrate the formation of a dehydrated rocky core surrounded by more hydrated and carbonated rocks. The forming ocean accumulates chemical species leached from rocks and released through alteration of minerals and organic compounds. This work showed that dehydration of Ceres’ interior could have been accompanied by redox transformations of organic compounds, reduction of sulfates, leaching of some elements (Na, C, S, etc.) from the rocks, and rock’s fracturing by overpressured gas-rich Na-C-Cl aqueous fluids. A downward freezing of the ocean could have led to accumulation of Na chloride and Na carbonate salts at the core-icy mantle interface. The evaluated fluid chemistry constrains habitability of putative aqueous phases within an early and today’s Ceres. The results will be presented at 46th Lunar and Planetary Science conference in 2015.
Anbar co-authored a publication with Chris McKay and Carolyn Porco that made the case for sampling and studying the Enceladus plume as prime target for astrobiology exploration. This paper was one of the 100 most read papers in Astrobiology in 2014. | 0.854235 | 3.734216 |
The distance to this nebula is not known with any real accuracy. According to the Skalnate Pleso Catalogue (1951) the distance of NGC 7662 is about 1,800 light years, the actual diameter about 20,000 AU. In a more recent survey of the brighter planetaries, C.R.O’Dell (1963) derived a distance of 1,740 parsecs or about 5,600 light years, increasing the actual size to 0.8 light year, or nearly 50,000 AU. It has a faint central star that is variable, with a magnitude range of 12 to 16. The central star is a bluish dwarf with a continuous spectrum and a computed temperature of about 75,000K. The nuclei of the planetary nebulae are among the hottest stars known.
NGC 7662 is a popular planetary nebula for casual observers. A small telescope will reveal a star-like object with slight nebulosity. A 6″ telescope with a magnification around 100x will reveal a slightly bluish disk, while telescopes with a primary mirror at least 16″ in diameter may reveal slight color and brightness variations in the interior. | 0.887562 | 3.190694 |
European astronomers have detected an unprecedented binary system featuring two hot blue O-type stars in orbits so tight they're actually touching each other — and they're not entirely sure what will happen when the stars complete their massive merger.
Located in the Giraffe Constellation, MY Camelopardalis (MY Cam for short), is one of the most massive binary star systems ever discovered. Individually, the two hot blue O-type stars contain 32 and 38 times the mass of our sun.
MY Cam is an eclipsing binary system in which one star passes in front of the other each time an orbit is completed. It has the shortest orbital period ever detected in a binary pair — a mere 1.2 days. The resulting changes in the brightness of the system is what enabled astronomers from the University of Alicante to confirm that it was in fact a binary system and not one massive star.
An illustration of MY Cam to scale at the quadrature phase. (J. Lorenzo et al./University of Alicante)
But given their immense size, they have to be in extremely close orbits to make a full turn so quickly. This means the stars are actually touching each other and that the material on their outer layers are forming a common envelope. Physicists call it a 'contact binary.' Both components are churning away on the main sequence, and are probably not far from the initial zero-age main sequence.
Indeed, the astronomers say that MY Cam is a young system that formed about two million years ago. Its current configuration may very well be the one it was born into, but it wasn't meant to last. According to the researchers, the system will eventually merge and create one massive single object. But some theoretical models are predicting an extremely fast merger process culminating in a massive release of energy in the form of an explosion.
That said, many astrophysicists believe that the merger of close binaries are the most efficient way to generate extremely massive stars. If true, MY Cam is the first example of such a system.
Read the entire study at Astronomy & Astrophysics: "MY Camelopardalis, a very massive merger progenitor". | 0.876255 | 3.831035 |
Cluster solves the mystery of equatorial noise
14 July 2015ESA's Cluster mission has solved a mystery which puzzled scientists for almost half a century. Data sent back by two of the spacecraft have revealed for the first time the physical mechanism behind the generation of "noisy" waves in near-Earth space.
|Cluster observes the structure of equatorial noise. Credit: ESA/ATG medialab|
Back in 1966, a NASA satellite known as OGO-3 discovered 'noisy' plasma waves at an altitude of around 18 000 km above the Earth. The waves occurred very close to the equatorial plane of the planet's magnetic field – the geomagnetic equator.
The location of the electric and magnetic fields of these waves, together with their unstructured nature, led to them being termed 'equatorial noise'. This 'noise' turned out to be one of the most frequently observed emissions in near-Earth space, being detected by many spacecraft as they fly over the geomagnetic equator.
Observations over the years by various space missions showed some evidence for discrete frequency bands, suggesting that the waves may interact with protons, alpha particles, and electrons near the geomagnetic equator. However, the width and spacing of these frequency bands appeared to be non-uniform and could not be accurately measured, except at low frequency.
Although several theories were proposed to explain how these waves were generated, their value was limited by a lack of clear observational evidence that could be used to support modelling of the phenomenon, and by the limited accuracy of the proposed models.
In an effort to solve the mystery of the generation and propagation of the equatorial noise, an international team of scientists decided to take advantage of the multipoint observations provided by ESA's Cluster mission. A specially planned Inner Magnetosphere Campaign was introduced, to study the structure of these waves in their source region.
The most significant observations were made between 18:40 and 18:55 GMT on 6 July 2013, when all four Cluster spacecraft were flying through the outer radiation belt, close to the geomagnetic equator. Clusters 3 and 4 were very near - within 60 km of each other - while Cluster 1 was approximately 800 km from the pair, and Cluster 2 was around 4400 km away in the earthward direction from the other three.
Observations of equatorial noise by STAFF instruments on Cluster 3 and Cluster 4.
Credit: Balikhin and Shprits, et al. (2015).
Observations by the Spatio-Temporal Analysis of Field Fluctuations (STAFF) instruments on Clusters 3 and 4 revealed that the waves had a highly structured and periodic pattern, providing clear observational evidence about how they were generated. The data also revealed in detail their banded structure, the most remarkable example of these structures ever observed in space.
The spectral lines showed multiples of the frequencies of the circular motion of protons in the presence of a uniform magnetic field – the so-called proton gyrofrequency. The observations of the 'noise' emissions were, in this case, much more coherent and structured than the majority of plasma waves.
"The clear appearance of the regular spectral lines associated with the waves reminded me of a comb," says Professor Michael Balikhin from the University of Sheffield, UK, a scientific principal investigator on Cluster and joint lead author of the paper in the journal Nature Communications which describes the research.
"They were found in the precise frequency range in which equatorial noise is usually observed. This previously unobserved, well organised, and periodic structure provided definitive evidence that the waves were generated by protons."
"It's truly remarkable how nature managed to draw such clear, narrow, and periodic lines in space," adds Yuri Shprits of UCLA, currently a Visiting Associate Professor at MIT, who led the study together with Michael Balikhin.
The Cluster measurements enabled not only the observation of the fine structure of the wave spectrum but also provided multi-satellite measurements of this emission at very short separation distances. The periodic pattern of emissions observed on Cluster 4 was almost an exact replication of that observed by Cluster 3, showing that the highly organised, periodic wave structure measured at least 60 km across.
The spectral observations, together with observations of particle distributions, allowed the researchers to calculate the growth rates of the waves. The Cluster spacecraft measurements also enabled them to determine the polarisation properties of the waves, further confirming that the observed emissions were the same type as those usually observed in equatorial noise waves.
This study clearly showed that these waves were produced by so-called ion ring distributions. This arrangement refers to the ring-like velocity distributions of the charged particles close to the geomagnetic equator, where more particles are observed at high velocity than low velocity. The Cluster spacecraft were able to measure these distributions, and models used by the scientists definitively showed that they are responsible for the excitation of the waves.
|Artist's impression of the Cluster spacecraft. Credit: ESA/ATG medialab|
"This remarkable result would not have been possible without a mission such as Cluster," says Michael Balikhin. "The multipoint observations enabled us to study the wave structure over distance and time.
"The extraordinary data from the Cluster Inner Magnetosphere Campaign would have been impossible to obtain without the combined effort of the whole Cluster team."
"Studies such as ours help scientists to understand the processes that are taking place in near-Earth space," says Yuri Shprits. "By combining observations of waves, observations of the particles that produce these waves and physics-based modelling, we are able to improve our understanding of the dynamics of Earth's radiation environment. This may eventually help predict the dynamics of the space environment, which is hazardous to satellites."
"Waves in the inner magnetosphere have recently attracted much attention because they are capable of accelerating electrons to relativistic energies in the radiation belts or providing a mechanism that results in the loss of these particles into the atmosphere – two fundamental aspects of space weather," says Philippe Escoubet, ESA's Cluster project scientist.
"This study has definitively identified the source of the equatorial noise that was discovered almost half a century ago. Understanding the mechanisms behind the generation of waves may be important for studies of laboratory plasmas and of plasmas elsewhere in the Universe."
Plasma is often described as the fourth state of matter. It consists of electrically charged particles, mainly electrons and protons.
The results described in this article are reported in Observations of Discrete Harmonics Emerging From Equatorial Noise, by Michael A. Balikhin, Yuri Y. Shprits, Simon N. Walker, Lunjin Chen, Nicole Cornilleau-Wehrlin, Iannis Dandouras, Ondrej Santolik, Chris Carr, Keith H. Yearby, Benjamin Weiss, published in Nature Communications, 14 July 2015.
Acknowledgement: STAFF Principal Investigator P. Canu, LPP/Ecole Polytechnique/CNRS.
Cluster is a constellation of four spacecraft flying in formation around Earth. It is the first space mission able to study, in three dimensions, the natural physical processes occurring within and in the near vicinity of the Earth's magnetosphere. Launched in 2000, it is composed of four identical spacecraft orbiting the Earth in a pyramidal configuration, along a nominal elliptical polar orbit of 4 × 19.6 Earth radii (1 Earth radius = 6380 km). Cluster's payload consists of state-of-the-art plasma instrumentation to measure electric and magnetic fields over wide frequency ranges, and key physical parameters characterising electrons and ions from energies of near 0 eV to a few MeV. The science operations are coordinated by the Joint Science Operations Centre (JSOC) at the Rutherford Appleton Laboratory, United Kingdom, and implemented by ESA's European Space Operations Centre (ESOC), in Darmstadt, Germany.
Department of Automatic Control and Systems Engineering
University of Sheffield, UK
Phone: +44 114 222 5628
Visiting Associate Professor at MIT / Researcher at UCLA
Phone: +1 617 2531902
Cluster Project Scientist
Scientific Support Office
Directorate of Science & Robotic Exploration
ESA, The Netherlands
Phone: +31 71 565 3454 | 0.835109 | 3.82862 |
A kind of closing ceremony is being held this week in Berlin, with scientists presenting the most intriguing results from the European Space Agency’s BIOMEX mission on the International Space Station.
BIOMEX, which stands for Biology and Mars Experiment, is led by Jean-Pierre de Vera from the German AeroSpace Center. Its purpose is to investigate the limits of life, while creating a database of which biological markers are retained when microorganisms are exposed to harsh environmental stresses—especially ultraviolet irradiation, desiccation, and low temperature. Bacteria, lichen, algae, fungi and other microorganisms were mixed with minerals and then exposed to space on the Expose-R2 facility located outside the Russian Zvezda module on the space station. Results from the mission are also detailed in a recent special issue of the journal Astrobiology.
In general, it was found that the tested microorganisms survived space and Mars-like conditions remarkably well. Most of the damage was caused by hard ultraviolet (UVC) irradiation. Daniela Billi from the University of Rome, for example, exposed dried cyanobacteria to UV radiation for 469 days and to a Mars-like atmosphere for 722 days, then examined the resulting damage to photosynthetic pigments and DNA.
Another intriguing study was presented by Natalia Kozyrovska from the Institute of Molecular Biology and Genetics in Kiev, Ukraine. Her group tested a terrestrial micro-ecosystem in space—a biofilm form of a natural assemblage of probiotic bacteria and yeasts, called Kombucha Multimicrobial Community. The test showed that even though biofilms incur damages in space, they also provide significant protection. And yes, the microorganisms are extracted from the beverage of the same name.
Although this meeting officially ends the BIOMEX project, research will continue, and more exciting insights may come in the future, for example from single-cell sequencing analyses of microbes exposed to space and simulated Mars conditions. That work is currently done in Marina Walther-Antonio’s lab at the Mayo Clinic, with the goal of revealing what genetic changes are caused by space conditions.
So what’s next? A follow-on mission called BIOSIGN (Biosignatures and habitable niches) might be in space as soon as 2022. Its main objective is to analyze the extent to which selected organisms and fossils can survive space exposure and conditions on other planets. BIOSIGN will test various deep-sea microbes under simulated conditions similar to what might exist on the icy moons Enceladus and Europa. It also will expand the set of bio-molecules whose products and mechanisms of degradation will be studied.
The BIOMEX project is a great example of insightful science that’s possible to conduct in Earth orbit at relatively low cost, without having to send a spacecraft into deep space. It might even shed some light on the topic of panspermia—the possibility that microorganisms can survive the journey from one planetary body to another. | 0.863354 | 3.511066 |
Keeping track of position is crucial in a lot of situations. On Earth, it’s usually relatively straight-forward, with systems having been developed over the centuries that would allow one to get at least a rough fix on one’s position on this planet. But for a satellite out in space, however, it’s harder. How do they keep their communications dishes pointed towards Earth?
The stars are an obvious orientation point. The Attitude and Articulation Control Subsystem (AACS) on the Voyager 1 and 2 space probes has the non-enviable task of keeping the spacecraft’s communication dish aligned precisely with a communications dish back on Earth, which from deep space is an incomprehensibly tiny target.
Back on Earth, the star tracker concept has become quite popular among photographers who try to image the night skies. Even in your living room, VR systems also rely on knowing the position of the user’s body and any peripherals in space. In this article we’ll take a look at the history and current applications of this type of position tracking.
Celestial navigation has been practiced for thousands of years. In theory, all you need is your eyes and some knowledge of how the Sun, Moon and stars move in the skies throughout the seasons to get a sense of direction. But this doesn’t tell you your position on the Earth’s surface.
For most of human history, ships would stay within sight of the coast and rarely cross large bodies of water. When they did crossings, they would often use dead reckoning, using one’s known position, heading and speed. Although the concept of latitude had been around for a while, measuring latitude accurately required angle-finding instruments, such as an astrolabe, invented around 200 BC, or a sextant, invented in the 16th century.
An astrolabe, sextant, or similar measures the angles between known celestial bodies, from which the latitude can be deduced. The determining of longitude was a major question that ultimately came down to having an accurate clock, as longitude and solar time are directly related. The invention of timepieces that were both accurate and could be used on a ship or moving vehicle would not be solved until the 19th century when they became reliable and affordable enough that alternatives (lunar distance method) fell out of favor.
Finding one’s way in space
Although navigating in the mindbogglingly massive vacuum of space may seem harder than navigating on Earth, essentially the same principles apply. The most important thing is to have at least one point of reference. In the case of Earth-based navigation, this can be the Sun, the Moon or any bright star with a known trajectory and location in the sky.
For a space probe, the common metaphor of ‘sailing the ocean of stars’ is rather apt when it comes to navigation. The Attitude and Articulation Control Subsystem (AACS) as it is known on the Voyager, Cassini, and other spacecraft form the core of the navigation and positioning system. In the case of Cassini, it uses a number of sensors, including Stellar Reference Units (SRU), Inertial Reference Units (IRU) and Sun sensors (SSA). These SRUs are CCD-based star trackers that together with the other units keep the spacecraft aware of its relative position in space.
The Voyager spacecraft use a similar AACS system, as did other spacecraft in the past and probes after Voyager 1 and Voyager 2. For attitude reference, star trackers, star scanners, solar trackers, sun sensors, and planetary limb trackers are used. Voyager’s AACS uses a sun sensor for yaw and pitch reference, and a star tracker to continuously track a bright star at right angles for roll reference. Galileo references a star scanner that rotates with the spinning part of the spacecraft. Magellan used a star scanner to obtain a fix on two bright stars during a special maneuver every few orbits.
It isn’t just in space where star trackers are useful, either. In order to take photographs of the Milky Way and the night sky, the film or camera sensor requires long exposure times in order to gather sufficient light from the (faint) star light. Because the Earth rotates continuously, the position of the stars is shifting, and this makes a blurred mess over even a ten second exposure time, let alone half a minute or longer. In the old days, rotating the camera or telescope along with the stars was done by aligning a pivot with the earth’s axis and turning it at a preset rotation speed
for one’s location on Earth. More modern astrophotography rigs use a photo sensor that keeps a fix on one or more stars, moving the camera that is mounted on top of the tracker with just the right amount to get a sharp image.
Bodies in Space
For the moment at least, the Final Frontier when it comes to tracking one’s position is not outer space, but our living rooms. Significant R&D money is being invested in creating an ever more realistic and natural Virtual Reality (VR) experience. This requires that the system can keep track of not only where the user is looking in the virtual world, but also where their appendages are currently located.
In VR positional tracking aims to determine the yaw, pitch, and roll of displays, controllers, or body parts. Here there are two main options: either sensors on the user keep track of markers in their surroundings, like the Oculus Rift S does, or sensors that surround the user keep track of markers on the user’s body or on the controllers, like the Oculus Rift CV1‘s aptly named Constellation system. Of course, each solution comes with its own set of advantages and disadvantages (and aggravated users).
Methods for motion capture, often used for (CGI) films and video games, operate similarly. The big difference between VR and motion capture is that for motion capture it is acceptable to gear the subject up in special suits with markers, while also often including the finer details of facial movements, something that is less interesting in VR than tracking the movement of one’s digits. You don’t want to spend twenty minutes suiting up just to play a game.
Good Tracking Goes Places
Whether navigating a celestial body’s surface, the space between the stars, or a virtual reality while flailing wildly in the living room amidst curious glances from your pets, the challenges posed by determining position and orientation remain. Only the actual space that is being navigated changes.
Improved navigation on Earth has led humankind to explore and settle virtually every bit of land on this planet, to create accurate maps, and to locate ourselves in the Earth’s oceans, land, and skies with ever-increasing precision. Over time we learned to create our own markers in addition to the Sun and stars, using light houses, radio beacons, and ultimately a constellation of satellites to enable navigation.
In space, our probes don’t just navigate by stars alone anymore either. The NASA Deep Space Network provides both communication and tracking services to any spacecraft inside our solar system, and beyond. At this point in time, only the network’s largest 70-meter antenna can still communicate with and track the Voyager probes as they venture ever further into deep space.
It’s an interesting inversion that what allowed early sailors to navigate the seven seas and later space probes to navigate the solar system is now used to keep track of you in your living room as you explore the worlds that exist within our collective imagination. | 0.891154 | 3.835102 |
NASA published the first official photo taken with the new space telescope TESS, which was launched on April 18, 2018 by SpaceX's Falcon 9 rocket for high elliptical orbit. TESS is an abbreviation of Transiting Exoplanet Survey Satellite. It should help in searching for exoplanets, or planets similar to Earth, that could potentially be inhabited.
The telescope hit the target Earth orbit on July 25, 2018, and NASA recently published the first scientific photo taken by TESS to be used for research. However, they were made at the beginning of August.
In the picture only a part of the whole frame, which was made using all four telescope cameras. The visible fragment is part of the image captured with a detector belonging to one of the cameras. It shows how powerful the entire telescope is.
"The first scientific picture, the so-called first light, makes us aware of the capabilities of TESS cameras and shows that the mission can fulfill the potential in finding a new Earth," said Paul Hertz, director of NASA's astrophysics department.
NASA plans to search the telescope 85 percent. skies in two years. Every 27 days the telescope will focus on the new area. TESS will study 13 areas of the southern sky during the first year and then 13 areas of the northern sky during the second year of the mission. TESS should observe about 200,000 stars.
When searching for planets, the telescope will look for changes in the brightness of the star - a sign that the planet is flying in front of the star as part of its orbit.
According to the researchers, the data collected by TESS may result in the discovery of thousands of new planets that would be within 200 light years of Earth. The team responsible for the TESS mission hopes to even find about 50 small, rocky planets on which life could exist.
Previously, the Kepler Space Telescope was used for such searches - it almost ended with fuel and the telescope is now in a dormant state.
#NASA #TESS #space #Kepler #telescope #science #cosmos #exoplanet | 0.842737 | 3.312227 |
Cosmic rays in the Orion-Eridanus superbubble
2017 December 12
The Orion-Eridanus superbubble, formed from the winds and the explosions of Orion’s massive stars, could be a cosmic-ray acceleration site. Inside the superbubble, the large level of magnetohydrodynamics turbulence and the core-collapse supernovae have created a turbulent medium which effect on cosmic rays can be probed comparing their flux and spectrum in the superbubble to the average in nearby interstellar clouds.
To study cosmic rays in the superbubble, we first rely on Fermi Large Area Telescope data. Eight years of data and gamma rays above 250 MeV have been used. We are particularly interested in gamma rays resulting from the decay of neutral pions produced by the interaction of cosmic rays with interstellar gas. Hence, knowing both gas distribution and gamma-ray emission allows to obtain the cosmic-ray flux. We thus developed a model of the interstellar emission using multiwavelength tracers for the gas column densities in the different phases (atomic, molecular, ionized) of the superbubble in which atomic and molecular phases are further divided into several complexes based on coherence in spatial distribution and velocity. The model also includes other ancillary components such as inverse-Compton emission and point sources.
Preliminary results show that the emissivity spectrum of the main HI cloud is consistent with the average spectrum measured in nearby clouds located outside the superbubble, but within the Gould Belt. This uniformity calls for a detailed assessment of the recent supernova rate and the energetics of massive stellar winds in the superbubble in order to estimate the diffusion properties of the young cosmic rays and to evaluate the need, or not, to advect them away in the Gould Belt or to the halo via the local Galactic wind. | 0.847866 | 3.92058 |
By the end of this section, you will be able to:
- Discuss some of the key ideas of the theory of general relativity
- Recognize that one’s experiences of gravity and acceleration are interchangeable and indistinguishable
- Distinguish between Newtonian ideas of gravity and Einsteinian ideas of gravity
- Recognize why the theory of general relativity is necessary for understanding the nature of black holes
Most stars end their lives as white dwarfs or neutron stars. When a very massive star collapses at the end of its life, however, not even the mutual repulsion between densely packed neutrons can support the core against its own weight. If the remaining mass of the star’s core is more than about three times that of the Sun (MSun), our theories predict that no known force can stop it from collapsing forever! Gravity simply overwhelms all other forces and crushes the core until it occupies an infinitely small volume. A star in which this occurs may become one of the strangest objects ever predicted by theory—a black hole.
To understand what a black hole is like and how it influences its surroundings, we need a theory that can describe the action of gravity under such extreme circumstances. To date, our best theory of gravity is the general theory of relativity, which was put forward in 1916 by Albert Einstein.
General relativity was one of the major intellectual achievements of the twentieth century; if it were music, we would compare it to the great symphonies of Beethoven or Mahler. Until recently, however, scientists had little need for a better theory of gravity; Isaac Newton’s ideas that led to his law of universal gravitation (see Orbits and Gravity) are perfectly sufficient for most of the objects we deal with in everyday life. In the past half century, however, general relativity has become more than just a beautiful idea; it is now essential in understanding pulsars, quasars (which will be discussed in Active Galaxies, Quasars, and Supermassive Black Holes), and many other astronomical objects and events, including the black holes we will discuss here.
We should perhaps mention that this is the point in an astronomy course when many students start to feel a little nervous (and perhaps wish they had taken botany or some other earthbound course to satisfy the science requirement). This is because in popular culture, Einstein has become a symbol for mathematical brilliance that is simply beyond the reach of most people (Figure 1).
So, when we wrote that the theory of general relativity was Einstein’s work, you may have worried just a bit, convinced that anything Einstein did must be beyond your understanding. This popular view is unfortunate and mistaken. Although the detailed calculations of general relativity do involve a good deal of higher mathematics, the basic ideas are not difficult to understand (and are, in fact, almost poetic in the way they give us a new perspective on the world). Moreover, general relativity goes beyond Newton’s famous “inverse-square” law of gravity; it helps explain how matter interacts with other matter in space and time. This explanatory power is one of the requirements that any successful scientific theory must meet.
The Principle of Equivalence
The fundamental insight that led to the formulation of the general theory of relativity starts with a very simple thought: if you were able to jump off a high building and fall freely, you would not feel your own weight. In this chapter, we will describe how Einstein built on this idea to reach sweeping conclusions about the very fabric of space and time itself. He called it the “happiest thought of my life.”
Einstein himself pointed out an everyday example that illustrates this effect (see Figure 2). Notice how your weight seems to be reduced in a high-speed elevator when it accelerates from a stop to a rapid descent. Similarly, your weight seems to increase in an elevator that starts to move quickly upward. This effect is not just a feeling you have: if you stood on a scale in such an elevator, you could measure your weight changing (you can actually perform this experiment in some science museums).
In a freely falling elevator, with no air friction, you would lose your weight altogether. We generally don’t like to cut the cables holding elevators to try this experiment, but near-weightlessness can be achieved by taking an airplane to high altitude and then dropping rapidly for a while. This is how NASA trains its astronauts for the experience of free fall in space; the scenes of weightlessness in the 1995 movie Apollo 13 were filmed in the same way. (Moviemakers have since devised other methods using underwater filming, wire stunts, and computer graphics to create the appearance of weightlessness seen in such movies as Gravity and The Martian.)
Another way to state Einstein’s idea is this: suppose we have a spaceship that contains a windowless laboratory equipped with all the tools needed to perform scientific experiments. Now, imagine that an astronomer wakes up after a long night celebrating some scientific breakthrough and finds herself sealed into this laboratory. She has no idea how it happened but notices that she is weightless. This could be because she and the laboratory are far away from any source of gravity, and both are either at rest or moving at some steady speed through space (in which case she has plenty of time to wake up). But it could also be because she and the laboratory are falling freely toward a planet like Earth (in which case she might first want to check her distance from the surface before making coffee).
What Einstein postulated is that there is no experiment she can perform inside the sealed laboratory to determine whether she is floating in space or falling freely in a gravitational field. As far as she is concerned, the two situations are completely equivalent. This idea that free fall is indistinguishable from, and hence equivalent to, zero gravity is called the equivalence principle.
Gravity or Acceleration?
Einstein’s simple idea has big consequences. Let’s begin by considering what happens if two foolhardy people jump from opposite banks into a bottomless chasm (Figure 3). If we ignore air friction, then we can say that while they freely fall, they both accelerate downward at the same rate and feel no external force acting on them. They can throw a ball back and forth, always aiming it straight at each other, as if there were no gravity. The ball falls at the same rate that they do, so it always remains in a line between them.
Such a game of catch is very different on the surface of Earth. Everyone who grows up feeling gravity knows that a ball, once thrown, falls to the ground. Thus, in order to play catch with someone, you must aim the ball upward so that it follows an arc—rising and then falling as it moves forward—until it is caught at the other end.
Now suppose we isolate our falling people and ball inside a large box that is falling with them. No one inside the box is aware of any gravitational force. If they let go of the ball, it doesn’t fall to the bottom of the box or anywhere else but merely stays there or moves in a straight line, depending on whether it is given any motion.
Astronauts in the International Space Station (ISS) that is orbiting Earth live in an environment just like that of the people sealed in a freely falling box (Figure 4). The orbiting ISS is actually “falling” freely around Earth. While in free fall, the astronauts live in a strange world where there seems to be no gravitational force. One can give a wrench a shove, and it moves at constant speed across the orbiting laboratory. A pencil set in midair remains there as if no force were acting on it.
In the “weightless” environment of the International Space Station, moving takes very little effort. Watch astronaut Karen Nyberg demonstrate how she can propel herself with the force of a single human hair.
Appearances are misleading, however. There is a force in this situation. Both the ISS and the astronauts continually fall around Earth, pulled by its gravity. But since all fall together—shuttle, astronauts, wrench, and pencil—inside the ISS all gravitational forces appear to be absent.
Thus, the orbiting ISS provides an excellent example of the principle of equivalence—how local effects of gravity can be completely compensated by the right acceleration. To the astronauts, falling around Earth creates the same effects as being far off in space, remote from all gravitational influences.
The Paths of Light and Matter
Einstein postulated that the equivalence principle is a fundamental fact of nature, and that there is no experiment inside any spacecraft by which an astronaut can ever distinguish between being weightless in remote space and being in free fall near a planet like Earth. This would apply to experiments done with beams of light as well. But the minute we use light in our experiments, we are led to some very disturbing conclusions—and it is these conclusions that lead us to general relativity and a new view of gravity.
It seems apparent to us, from everyday observations, that beams of light travel in straight lines. Imagine that a spaceship is moving through empty space far from any gravity. Send a laser beam from the back of the ship to the front, and it will travel in a nice straight line and land on the front wall exactly opposite the point from which it left the rear wall. If the equivalence principle really applies universally, then this same experiment performed in free fall around Earth should give us the same result.
Now imagine that the astronauts again shine a beam of light along the length of their ship. But, as shown in Figure 5 this time the orbiting space station falls a bit between the time the light leaves the back wall and the time it hits the front wall. (The amount of the fall is grossly exaggerated in Figure 5 to illustrate the effect.) Therefore, if the beam of light follows a straight line but the ship’s path curves downward, then the light should strike the front wall at a point higher than the point from which it left.
However, this would violate the principle of equivalence—the two experiments would give different results. We are thus faced with giving up one of our two assumptions. Either the principle of equivalence is not correct, or light does not always travel in straight lines. Instead of dropping what probably seemed at the time like a ridiculous idea, Einstein worked out what happens if light sometimes does not follow a straight path.
Let’s suppose the principle of equivalence is right. Then the light beam must arrive directly opposite the point from which it started in the ship. The light, like the ball thrown back and forth, must fall with the ship that is in orbit around Earth (see Figure 5). This would make its path curve downward, like the path of the ball, and thus the light would hit the front wall exactly opposite the spot from which it came.
Thinking this over, you might well conclude that it doesn’t seem like such a big problem: why can’t light fall the way balls do? But, as discussed in Radiation and Spectra, light is profoundly different from balls. Balls have mass, while light does not.
Here is where Einstein’s intuition and genius allowed him to make a profound leap. He gave physical meaning to the strange result of our thought experiment. Einstein suggested that the light curves down to meet the front of the shuttle because Earth’s gravity actually bends the fabric of space and time. This radical idea—which we will explain next—keeps the behavior of light the same in both empty space and free fall, but it changes some of our most basic and cherished ideas about space and time. The reason we take Einstein’s suggestion seriously is that, as we will see, experiments now clearly show his intuitive leap was correct.
Key Concepts and Summary
Einstein proposed the equivalence principle as the foundation of the theory of general relativity. According to this principle, there is no way that anyone or any experiment in a sealed environment can distinguish between free fall and the absence of gravity.
concept that a gravitational force and a suitable acceleration are indistinguishable within a sufficiently local environment
general theory of relativity:
Einstein’s theory relating gravity and the structure (geometry) of space and time
- Strictly speaking, this is true only if the laboratory is infinitesimally small. Different locations in a real laboratory that is falling freely due to gravity cannot all be at identical distances from the object(s) responsible for producing the gravitational force. In this case, objects in different locations will experience slightly different accelerations. But this point does not invalidate the principle of equivalence that Einstein derived from this line of thinking. ↵ | 0.819811 | 4.118135 |
The Sun ejects vast clouds of ionized gas into space; these clouds are known as coronal mass ejections (CMEs). Each CME may carry 1,000,000,000 tonnes of gas into space at speeds that can approach 2000 km/s. When they engulf Earth, CMEs can disrupt power, navigation, communication and satellite control systems. Despite their importance, scientists don't fully understand the origin or evolution of CMEs, nor their structure or extent in interplanetary space.
NASA’s twin spacecraft STEREO mission, launched in October 2006, is providing a totally new perspective on solar phenomena by imaging CMEs and other solar features from two viewpoints simultaneously. The two near-identical spacecraft are in Earth-like orbits around the Sun, displaced from one another, with the STEREO-A spacecraft orbiting the Sun ahead of the Earth and STEREO-B orbiting the Sun behind the Earth. Both spacecraft look at the Sun itself, and also the region of interplanetary space between the Sun and Earth-like distances (1 Astronomical Unit; 1 AU). The unique twin-platform view allows stereoscopic imaging of the Sun and the structure of CMEs, enabling scientists to study their fundamental nature and origin.
It is, in fact, the RAL Space-led Heliospheric Imagers (HIs) on STEREO that observe that region of interplanetary space between the Sun and 1 AU, using wide-angle telescopes. The STEREO/HI instruments are being used to identify and track CMEs as they propagate through interplanetary space, with particular focus on those that are directed towards the Earth.
When combined with data from near-Earth spacecraft, and observatories on the ground, the STEREO data will enable scientists to identify and track in 3D those CMEs that propagate towards Earth and investigate their effects on Earth’s environment, as well as studying the processes on the Sun associated with their launch. In addition to leading the STEREO/HI instruments, all of the imaging instruments aboard both STEREO spacecraft use a CCD-based camera system developed by RAL Space.
(Credit: Backstage Science)
Last updated: 12 October 2017 | 0.804399 | 3.787074 |
Today the planet Venus will appear to pass in front of the sun as seen from the surface of the Earth. This phenomenon, called a transit of Venus, happens only a few times in 250 years. The next one will be in 2117. But why does it matter?
It provides interplanetary perspective
Transits of Venus were scientific gold for early astronomers, who used them to derive an accurate measurement of the size of the solar system. By noting the time each planet took to go around the sun, and then crunching that data via methods developed by 17th century mathematician Johannes Kepler, these telescope-equipped boffins could determine each planet’s relative distance from the sun, as measured in terms of astronomical units (the distance from the Earth to the sun). Collecting such data during a transit was the reason Captain Cook was able to travel halfway around the world from London to Tahiti in 1769.
For 2012, a Dutch astronomer named Steven van Roode has created an smartphone app, VenusTransit, that lets users simultaneously observe the transit on different sides of the world. To use the app, you tap the screen the exact moment Venus completely enters the face of the sun (Contact II, as it’s called). The app notes the observer’s precise location on Earth. Then, it collects the data necessary to make the most accurate ground-based measurement of the size of the solar system, while the transit is still happening!
But wait, don’t we already know the distance to the sun? Yes. Equipment in space provides us with very accurate direct measurements of the size of the solar system. Van Roode’s project is more a cool example of citizen science, of people coming together around the globe to collect scientific data.
Why doesn’t a transit of Venus happen every year?
The sun is in the middle of the solar system. Then comes Mercury, then Venus, then Earth, then the rest of the planets (which don’t enter into this, so forget them. Forget Mercury, while you’re at it.) Focus on the sun, Venus and the Earth. We’re used to thinking of the solar system as a number line, with all the planets lined up from left to right along the X axis. But that’s not the case.
Venus and the Earth go around the sun at different speeds, in nearly circular orbits — a year on Venus is over before two-thirds of an Earth year is complete. This means that at any given moment, Venus could be behind the sun, or to the side of the sun, or on the same side of the sun as seen from the Earth. The sun, Venus and Earth only line up like a string of beads every 584 days or so.
So why doesn’t a transit of Venus happen every 584 days?
Because the orbit of Venus is tilted about 3.25 degrees compared to the Earth’s. This means that when the sun, Venus and Earth line up, Venus could be as much as 3.25 degrees above the sun or 3.25 degrees below the Sun, or anywhere in between. Since the Sun is only about half a degree wide in our sky, Venus could be in a region 15 solar diameters wide! It’s not hard to see why only very rarely — like hundreds of years rarely — Venus would happen to pass directly in front of the sun, like it will a few hours from now.
Image: Dark Sky Photos | 0.819161 | 3.943184 |
The arrival of a comet within sight of planet is an event of international significance. See the huge media attention that the Haley or Hale-Bopp have had when they have come within sight. The sight of these fantastic space objects is simultaneously frightening as well as awe-inspiring.
Most of all, it is throughout these comet viewings that the astronomer appears in all people. However, what is a comet? Where did it come from? And also exactly how does it get that amazing tail?
We ought to never puzzle comets with asteroids. Planets are little area rocks that come from a planet belt in between Mars and also Jupiter. While still rather spectacular to see, they pale in contrast to the arrival of a comet. Planets likewise have obtained substantial research study by the clinical community.
Not as much is known about comets. As a rule, comets are significantly larger than asteroids. The make-up of a comet is a combination of nebulous, gasses, ice, dust as well as area particles. One scientist called the composition of a comet as similar to a “filthy snowball” because the make-up is so varied and changeable.
The center or core of a comet is generally peaceful strong, yet the “snowball” products frequently produce a “cloud” around that center that can end up being fairly large which extends at great sizes behind the comet as it moves with space. That routing plume is what composes the comet’s stunning tail that makes it so amazing to watch when a comet comes within view of Planet.
The beginnings of comets are likewise mystical. There are a number of concepts regarding where they originate from, but it is clear that they originate from outdoors our planetary system, someplace in deep space. Some have speculated they are fragments left over from the company of planets that get loose from whatever gravitational pull as well as being sent out flying throughout space to at some point obtain captured up in the gravity of our sun bringing them right into our planetary system.
Another theory is that they originate from an aeriform cloud called the Oort cloud which is cooling down out there after the company of the sunlight. As this space particle cool down, it obtains arranged right into one body which then collects sufficient mass to be drawn in into the gravity of our planetary system becoming a quick moving comet plunging toward our sun. However, because of the strong gravitational orbits of the numerous worlds in our solar system, the comet does not constantly promptly collide with the sunlight and usually takes on an orbit of its own.
The lifespan of comets differs widely. Scientists describe a comet that is anticipated to burn out or affect the sun within two hundred years as a brief duration comet whereas a long period comet has a life expectancy of over two a century. That may seem long to us as planet occupants however in terms of stars and planets, and this is a very brief life as a space object without a doubt.
Researchers across the globe have put together some rather remarkable probes to find out more about comets to assist our understanding of these site visitors from beyond. In 1985, as an example, the United States placed a probe into the path of the comet Giacobini-Zinner which went through the comet’s tail event remarkable scientific knowledge concerning comets. After that in 1986, a worldwide collation of researchers had the ability to introduce a probe that had the ability to fly near Haley’s comet as it passed near Planet and also continue the study.
While science fiction authors, as well as tabloid newspapers, like to alarm us with the opportunity of a comet impacting the planet, scientists who comprehend the orbits of comets as well as what modifications their courses inform us this is not likely. That is great due to the fact that some comets get to sizes that are as huge as earth to make sure that impact would certainly be ravaging. For now, we can enjoy the fun of seeing comets make their rare visits to our night sky as well as admire the spectacular shows that these site visitors from past put on when they are visible in the cosmos. | 0.828507 | 3.448536 |
Convert 458 Days to Weeks
To calculate 458 Days to the corresponding value in Weeks, multiply the quantity in Days by 0.14285714285714 (conversion factor). In this case we should multiply 458 Days by 0.14285714285714 to get the equivalent result in Weeks:
458 Days x 0.14285714285714 = 65.428571428571 Weeks
458 Days is equivalent to 65.428571428571 Weeks.
How to convert from Days to Weeks
The conversion factor from Days to Weeks is 0.14285714285714. To find out how many Days in Weeks, multiply by the conversion factor or use the Time converter above. Four hundred fifty-eight Days is equivalent to sixty-five point four two nine Weeks.
Definition of Day
A day (symbol: d) is a unit of time. In common usage, it is either an interval equal to 24 hours or daytime, the consecutive period of time during which the Sun is above the horizon. The period of time during which the Earth completes one rotation with respect to the Sun is called a solar day. Several definitions of this universal human concept are used according to context, need and convenience. In 1960, the second was redefined in terms of the orbital motion of the Earth, and was designated the SI base unit of time. The unit of measurement "day", redefined in 1960 as 86 400 SI seconds and symbolized d, is not an SI unit, but is accepted for use with SI. A civil day is usually 86 400 seconds, plus or minus a possible leap second in Coordinated Universal Time (UTC), and occasionally plus or minus an hour in those locations that change from or to daylight saving time.
Definition of Week
A week (symbol: wk) is a time unit equal to seven days. It is the standard time period used for cycles of rest days in most parts of the world, mostly alongside—although not strictly part of—the Gregorian calendar. The days of the week were named after the classical planets (derived from the astrological system of planetary hours) in the Roman era. In English, the names are Monday, Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday.
Using the Days to Weeks converter you can get answers to questions like the following:
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- How much is 458 d in wk? | 0.830061 | 3.254713 |
, good question! In all my calculations and figures I treat the particle as massless (a good approximation if it is say, a spacecraft or asteroid as a Trojan of a planetary body).
If it is massless, then stability about the L4 and L5 points occurs if the primary mass is at least 24.96 times the mass of the secondary. But what if the particle is not massless? In generality, the condition for stability of orbits about L4 and L5 is given by
where you may call m1 the star's mass, m2 the mass of the big planet, and m3 the smaller (Trojan) body.
With this formula we can quickly confirm that if we set m3=0, then m1 must be at least 24.96 times m2. But what if we let m1 be 1 solar mass and m2 be the mass of Jupiter? How big can m3 be and still be stable as a Trojan body?
Answer: About 40 Jupiter masses! (Surprising, yes!)
Even if both planets had the mass of Jupiter, then they could be stable in one another's orbital space, as Trojans of one another. But they could not both have a mass of over 20 Jupiters, or else the stability would fail since together they'd be too massive relative to the star, and the chaos of the 3-body problem would appear.
In other words, for almost any reasonable choice of masses of star and planet, another planet could exist in a stable Trojan orbit.
Why then do we not find many Trojan planets in nature?
The analysis here has been for an idealized situation, where we considered only two masses (plus a co-orbital body) and for them to be in circular orbits. Eccentric orbits will reduce the stability, as will the presence of additional planets in the system. Many of the Trojan asteroids of Jupiter are not in stable orbits for example, and those asteroid groups have slowly been eroded over time. Others may be newly caught there, and remain only temporarily.
But maybe an even bigger reason is that planetary systems are very dynamic, especially in their youth. The planets form by accreting dust and gas out of the disk, and then their orbits migrate as they scatter nearby planetessimals away. The planets also influence one another, potentially even leading them to swap places or get ejected from the system. So even if a Trojan planet were to exist in a system's early history, it probably wouldn't remain there for very long while all this chaos is happening. | 0.896957 | 3.791683 |
James Lovelock's Daisyworld is a computer model of Gaia's homeostatic regulation of planetary climate. It features a coupled interaction between an idealized biota and its environment. Like our world, Daisyworld is steadily forced by a sun gradually gaining in strength. However, Daisyworld's biota consisted of only two species--black daisies that thrive when it’s cool and white daisies that thrive when it’s hot. Seeded with both, Daisyworld starts out cool but is gradually heated by a warming sun. Yet due to their different albedos, or indexes of reflectivity, the black and white daisies feed back upon that global warming to different effect.
The low-albedo black daisies heat the planet further by absorbing the sun’s rays, while the high-albedo white daisies cool the planet by reflecting that same radiation back to space. The black daisies thrive at first under the initially cool conditions that suppress the growth of the white daisies. But as the black daisies proliferate, the planet warms up enough to favor the spread of white daisies and to suppress the growth of black daisies. The growing tide of white daisies diminishes the blanket of black daisies while also reflecting heat away from the planet. These counter-effects settle down or regulate the positive amplification between the sun and the black daisies that had been driving up the temperature.
When the model is set into motion, Daisyworld soon maintains the temperature of its virtual climate at a steady level despite the increasing strength of its sun. It does so automatically, with no goal in mind but only the mutual interplay of negative and positive feedbacks: “No foresight or planning is required by the daisies only their opportunistic local growth when conditions favor them” (Lovelock). The systemic interplay between the black and white daisies models the mutual coupling of two Gaian feedback loops, either of which can exert a negative--that is, regulatory or stabilizing--effect on the other to achieve and conserve a virtual homeostasis. Daisyworld's climate remains stable until the model’s solar forcing becomes too great for the system to control. Driven past that tipping point, Daisyworld life goes extinct.
--adapted from Bruce Clarke, Gaian Systems: Lynn Margulis, Neocybernetics, and the End of the Anthropocene, forthcoming in 2020 from the University of Minnesota Press.
Also see Daisyworld at Wikipedia. | 0.821852 | 3.099508 |
A favourite target for amateur astronomers, the Wild Duck Cluster, also known as Messier 11 and, more formally NGC 6705, is a stunning sight in even small telescopes with its brightest stars forming a “V” shape reminiscent of a flock of ducks. Located in the constellation Scutum, the cluster is about 6,200 light years from Earth and contains nearly 3,000 stars, making it one of the richest and most compact open clusters known. It was discovered in 1681 and included in comet-hunter Charles Messier’s famous catalogue in 1764. This view from the Hubble Space Telescope was chosen as “Picture of the Week” at the European Space Agency’s Hubble site.
Astronomers using data from the NASA/ESA Hubble Space Telescope and other observatories have performed an accurate census of the number of galaxies in the universe. The researchers came to the surprising conclusion that the observable universe contains at least two trillion galaxies. The results also help solve an ancient astronomical paradox — why is the sky dark at night?
Globular clusters offer some of the most spectacular sights in the night sky. These ornate spheres contain hundreds of thousands of stars, and reside in the outskirts of galaxies. The Milky Way contains over 150 such clusters — and the example shown in this NASA/ESA Hubble Space Telescope image, named NGC 362, is one of the most unusual ones. | 0.83938 | 3.25469 |
Updated at 7:40 a.m. ET
A Canadian and two Swiss scientists have won the Nobel Prize in physics for contributions to our understanding of the evolution of the universe and Earth's position in the cosmos.
James Peebles of Princeton received half of the prize, with Michel Mayor and Didier Queloz sharing the other half, the Royal Swedish Academy of Sciences in Stockholm announced on Tuesday.
"While James Peebles' theoretical discoveries contributed to our understanding of how the universe evolved after the Big Bang, Michel Mayor and Didier Queloz explored our cosmic neighborhoods on the hunt for unknown planets. Their discoveries have forever changed our conceptions of the world," the secretary-general of the academy, Goran Hansson, said.
"This year's laureates have contributed to answering fundamental questions about our existence," he said. "The discoveries have forever changed our conceptions of the world."
Peebles was awarded the prize for creating a theoretical framework that is the foundation of our modern understanding of the universe's history, from the Big Bang to present day.
"Were it not for the theoretical discoveries of James Peebles, the wonderful, high-precision measurements of the [cosmic background radiation] over the last 20 years would have told us almost nothing," academy member Mats Larsson said.
Mayor and Queloz were recognized for their 1995 discovery of the first planet outside our solar system orbiting a sun-type star, an exoplanet. The planet, 51 Pegasi b, is located about 50 light-years from Earth in the constellation Pegasus. It was detected by analysis of the slight changes in the star's spectrum caused by the orbiting planet.
"I was not working alone," Peebles said by telephone during a news conference in Stockholm. "From the beginning, I have always had colleagues."
Referring to the growing field of cosmology, Peebles reflected on his more than 50-year career and the changes that have occurred over that time: "The subject grew and I grew with it."
Past physics prize laureates include Albert Einstein, Niels Bohr and James Chadwick, the discoverer of the neutron. Marie Curie won the prize in 1903 for her work in understanding the nature of radioactivity.
In 2013, Peter Higgs, who theorized the subatomic boson that bears his name, won the prize after the particle was observed for the first time during experiments at CERN's Large Hadron Collider.
Candidates eligible for the physics prize are nominated by qualified persons and invited by the Nobel Committee to submit names for consideration. No one can nominate himself or herself.
This year's Nobel Prize is worth 9 million kronor ($918,000).
In a previous version of this story, we incorrecly said Marie Curie had won a second Nobel Prize in physics for having discovered the elements radium and polonium. That award was actually the Nobel for chemistry. | 0.856107 | 3.220871 |
A seasonal ozone layer over the Martian south pole
29 September 2013For the past decade, ESA's Mars Express orbiter has been observing atmospheric structure on the Red Planet. Among its discoveries is the presence of three separate ozone layers, each with its own characteristics. A new comparison of spacecraft data with computer models explains how global atmospheric circulation creates a layer of ozone above the planet's southern winter pole.
|Ozone production over the southern winter pole on Mars. Credit: ESA/ATG medialab|
Ozone (O3) is a form of oxygen gas which contains three atoms, rather than two. On Earth, ozone is a pollutant at ground level, but at higher altitudes it provides an essential protective layer against harmful solar ultraviolet (UV) light.
However, ozone molecules are easily destroyed by solar ultraviolet light and by chemical reactions with hydrogen radicals, which are released by photolysis (splitting) of water molecules. The role of pollution in its destruction has been a major focus of attention since the mid-1980s, when a hole in the ozone layer was discovered above Antarctica.
Until the early 1970s, no one could be sure whether ozone existed on any of the other planets. Ozone was then detected on Mars and it has since been discovered on Venus by ESA's Venus Express mission. On Mars, the ozone concentration is typically 300 times thinner than on Earth, although it varies greatly with location and time.
In recent years, the SPICAM UV spectrometer on board Mars Express has shown the presence of two distinct ozone layers at low-to-mid latitudes. These comprise a persistent, near-surface layer below an altitude of 30 km, and a separate layer, which is only present in northern spring and summer, and whose altitude varies from 30 to 60 km.
In recent years, SPICAM has also provided evidence for the existence of a third ozone layer which exists 40-60 km above the southern winter pole, with no counterpart above the North Pole.
In a paper published in the journal Nature Geoscience, Franck Montmessin and Franck Lefèvre, two scientists from LATMOS in Guyancourt, France, have analysed approximately 3000 occultation sequences and vertical ozone profiles collected by SPICAM on the night side of Mars.
The data were collected during three and a half Martian years (2004 - 2011), with greater sampling over the southern hemisphere due to the spacecraft's elliptical orbit and the requirement to obtain the majority of occultations on the planet's night side. They were then compared with the LMD global climate model (GCM), developed in France, which computes the evolution of 16 gas species by means of a comprehensive description of the Martian photochemistry.
When SPICAM observed regions poleward of 75 degrees South, which were experiencing continuous polar night, it detected a previously unknown layer of ozone located at heights of 35 - 70 km, with a peak concentration at 50 km. This third ozone layer shows an abrupt decrease in elevation between 75 and 50 degrees South.
This layer was found to exist only above the winter pole. SPICAM detected a gradual increase in ozone concentration at 50 km until midwinter, after which it slowly decreased to very low concentrations, with no layer perceptible above 35 km.
The authors of the paper in Nature Geoscience believe that the observed polar ozone layers are the result of the same atmospheric circulation pattern that creates a distinct oxygen emission recently identified in the polar night.
This circulation takes the form of a huge Hadley cell in which warmer air rises and travels poleward before cooling and sinking at higher latitudes. (Earth's atmosphere has two Hadley cells between the equator and the subtropics.)
"This process consists of deep vertical downwelling of oxygen-rich air which has been transported from the summer hemisphere," explained Franck Montmessin, lead author of the paper.
"Oxygen atoms produced by CO2 photolysis in the upper branch of the Hadley cell eventually recombine in the polar night to form molecular oxygen (O2) and ozone. The concentration of ozone gas at night is dependent upon the supply of oxygen and the rate of destruction due to hydrogen radicals."
"This ozone-forming process has no counterpart on the Earth, so Mars provides an example of how diverse and complex chemical processes can be in the atmospheres of terrestrial planets and how they may potentially operate on exoplanets."
Despite SPICAM's coarser coverage of the northern polar region in autumn and winter, the scientists searched its data for evidence of a comparable layer of ozone in between 60 and 65 degrees North – but without success.
"At these latitudes, no polar ozone layer can definitively be identified from the SPICAM data," said Montmessin. "This implies that atmospheric chemistry and/or transport behave differently in the two hemispheres."
This dichotomy is confirmed by the GCM, which predicts no high-altitude ozone layer in the northern polar night region. Since the simulations show that Hadley circulation should be most active at the northern winter solstice, other processes besides transport must be considered.
The authors believe that the explanation lies in seasonal variations of temperature and water vapour, caused indirectly by the highly elliptical orbit of Mars and the planet's large axial tilt.
The southern summer takes place around perihelion, when Mars is more than 40 million km closer to the Sun than it is during the northern summer. As a result, the southern hemisphere has warmer summers than the northern hemisphere.
This temperature difference greatly influences the amount of water vapour in the atmosphere, since warmer air can contain more moisture. This, in turn, affects the production of ozone-destroying hydrogen radical molecules.
During the cooler northern summer, water vapour is essentially confined below 15 km. This vertical confinement reduces the transport of water from the north to the south.
Since hydrogen radical molecules can only be created by photolysis of water vapour above 25 km, few of these destructive radicals are produced in the northern hemisphere and transported southward. As a result, any ozone forming over the high southern latitudes remains nearly intact, allowing the creation of a polar ozone layer.
Conditions are very different during the southern summer. With Mars near perihelion and an increase of dust activity, the upper atmosphere becomes warmer. This warming raises the altitude at which the atmosphere becomes saturated with water to above 40 km and allows it to contain several times more water than around aphelion.
Enhanced hydrogen radical production from photolysis of water vapour results in a much stronger flow of ozone-destroying radicals to the north winter pole than occurs to the south winter pole in the aphelion season. This leads to a rate of ozone destruction that is about 100 times greater above the northern winter pole than above its southern counterpart.
"We believe this accounts for the different behaviour of the wintertime polar ozone layers on Mars," said Montmessin. "If there is an ozone layer above the northern winter pole, it must be very sparse compared with its southern counterpart."
"The study of ozone on Mars is fundamental in understanding the photochemical processes that control the chemical reactions which recycle carbon dioxide, the main gas in the Martian atmosphere," said Olivier Witasse, ESA's Mars Express Project Scientist. "This recycling ensures the long-term stability of an atmosphere around Mars."
"All being well, SPICAM observations of the planet's atmosphere will continue during the extended phase of the Mars Express mission, until the end of 2016, thanks to an orbit which is favourable for such measurements. From mid-2017 onwards, the NOMAD spectrometer on board the ExoMars Trace Gas Orbiter will take over the task of atmospheric profiling."
The results described in this article are reported in "Transport-driven formation of a polar ozone layer on Mars", by Franck Montmessin and Franck Lefèvre, published online on 29 September 2013 in Nature Geoscience; doi: 10.1038/ngeo1957
SPICAM (Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars) enables scientists to derive vertical profiles of the Martian atmosphere to heights of well above 100 km. This is done by studying how light from bright stars is absorbed as it passes through the gases of the Martian atmosphere at different altitudes - a technique called stellar occultation.
The Global Climate Model (GCM) of Mars used for this study has been developed at the Laboratoire de Météorologie Dynamique (LMD) and LATMOS. This model computes the evolution of 16 gaseous species by means of a comprehensive description of the Martian photochemistry,
Mars Express was launched in June 2003 and became ESA's first visit to another planet in the Solar System. The scientific payload, provided by research institutes throughout Europe, consists of seven instruments that provide remote sensing measurements of the atmosphere, ground and below the surface. Since arrival in orbit around Mars in December 2003, Mars Express has been helping to answer fundamental questions about the geology, atmosphere, surface environment, history of water and potential for life on Mars.
Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS)
Mars Express Project Scientist
Research and Scientific Support Department
Directorate of Science and Robotic Exploration
ESA, The Netherlands | 0.868631 | 3.956197 |
In a rare discovery, astronomers have found a distant rotating disk galaxy ever observed, known as the Wolfe Disk after the late astronomer Arthur M. Wolfe, spinning at 170 miles (272 kilometers) per second similar to our Milky Way. In a report published on May 20, in the scientific journal Nature, and the UC Santa Cruz official website, an international team of astronomers found a massive rotating disk galaxy that existed when the universe was only ten per cent of its current age, which now challenges the traditional models of galaxy formation.
Discovered with Atacama Large Millimeter/submillimeter Array (ALMA), rotating galaxy DLA0817g now challenges many galaxy formation simulations, which predict that massive galaxies in the evolution of the cosmos grew through mergers of smaller galaxies and hot clumps of gas.
Its properties are astonishingly similar to our own galaxy, despite being only 1.5 billion years old, coauthor J. Xavier Prochaska, professor of astronomy and astrophysics at UC Santa Cruz said in UC’s research report.
Another lead author, Marcel Neeleman, Max Planck Institute for Astronomy in Heidelberg, Germany, was quoted saying that while previous studies hinted at the existence of these early rotating gas-rich disk galaxies, thanks to ALMA astronomers now have the unambiguous evidence that they occur as early as 1.5 billion years after the Big Bang.
We think the Wolfe Disk has grown primarily through the steady accretion of cold gas, UC’s astronomer Prochaska said in the report. Still, one of the questions that remains is how to assemble such a large gas mass while maintaining a relatively stable, rotating disk, he added.
Further, adding to Prochaska’s point, Neelam explained that most galaxies that were found early in the universe looked like train wrecks because they underwent constant and often violent merging. And hence, these hot mergers make it difficult to form well-ordered, cold, rotating disks as we observe in our present universe. And that makes it a unique finding, he added.
As per the report, the team also used the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) and the NASA/ESA Hubble Space Telescope to learn more about the formation of the stars in the Wolfe Disk. The star formation rate in the Wolfe Disk was at least ten times higher than in the Milky Way galaxy, which proves that it must be one of the most productive disk galaxies in the early universe, Prochaska was quoted saying in the report. | 0.814956 | 3.973139 |
The Chandra X-ray Observatory and Hubble Space Telescope are two telescopes, orbiting earth, capable of observing in the x-ray and visible regime respectively. Over the years they have produced streams of absolutely stunning images of our beautiful universe. One of the images I like most is a combination of data from both telescopes:
It shows the enormous galaxy cluster Abell 1689 and apart from being visualy appealing, the image is also full of cool physical effects that I would like to point out. Let’s start with with the purple x-ray glow coming from the center of the massive galaxy cluster. It originates from extremely hot gas in the center of the galaxy cluster. Reportedly, the gravitational forces at play in that region cause the gas to heat to over a 100 million degrees Celsius. Also, the same purple region is predicted to contain large amounts of dark matter (matter we can’t directly measure, but has to be there in order for the gravitational fields to be as they are).
How intens the gravitational fields are in the center region of the cluster is also apparent from another, in multiple ways cooler, physical effect; gravitational lensing. The theory of gravitational lensing relies on Einsteins theory of general relativity. This may sound scary, but as long as we stay away from the math, there is nothing to worry about ;). To illustrate how this effect works I will borrow a figure from elsewhere on the webweb.
Einstein’s theory of general relativity tells us that spacetime (simply picture this as space) is curved in the vicinity of very heavy objects. The huge galaxy cluster Abell 1689 significantly curves spacetime and this curved spacetime deflects light from its straight path as is illustrated in the image above.
The complex shape of the gravitational field in Abell 1689 bends light from galaxies behind it towards earth so that a single object appears to be at multiple different places at once. Taking into account that this lensing of course distorts the image intensely, what we expect to see are some vague blurry objects with odd shapes that don’t seem to belong there. This is exactly what is visible in the image that this article is about. In the image below (Hubble data only) I have highlighted the lensed images. Look them up in the original image.
One more effect I would like to point out is the diffraction due to the telescopic design. The brightest stars in the image are not simply bright dots as one would expect from a spherical star, but look more like crosses. These 4 ‘spikes’ that surround the center star are know as diffraction spikes. They are caused by the structure that supports the secondary mirror in the telescope. This structure is comprised of several (4 in the case of the Hubble Space Telescope) bars that keep the secondary mirror in its place as is shown in the graphic below.
The diffraction is due to the interaction between light passing on either side of the support bars. But how is this possible if light moves in a straight line? Well, as light is not purely particle-like of nature, but also behaves somewhat as a wave, part of the incoming waves may ‘bend around the bar’ a bit. The diffraction pattern shows what is known as the ‘Fourier transform’ of the light. Which means that it shows the spectrum of frequencies present in the incoming light. This is also clearly visible in the image of Abell 1689. Below you see an excerpt of the bigger picture, clearly showing the different colors in the spikes.
Not only the Hubble telescope shows this diffraction pattern, but amateur telescopes with a similar design do to. In fact, my telescope has 3 such bars which shows 6 (albeit less pronounced) diffraction spikes around bright objects. A while ago I imaged Deneb, a blue-white supergiant star weighing about 20 solar masses, and the resulting image showed some cool diffraction spikes.
I hope that after reading this, you can appreciate the image at the top of this post as much as I do 🙂 | 0.87802 | 4.035196 |
Sure, the Moon now seems more colorful than controversial viral dress shades. Love it or loathe it, the Internet can sure set a meme in motion. And this week’s Full Moon on Thursday evening offers up one of our faves, as the most distant Full Moon of 2015 occurs on March 5th. Yup, the Mini-Moon is indeed once again upon us, a time when the Full Moon appears slightly smaller than usual as seen from the Earth. But can you really tell the difference?
The third Full Moon of the year occurs this week on Thursday, March 5th. Also known as the Worm or Sap Moon by the Algonquin tribes of New England, the moment of Full phase occurs at 18:07 Universal Time (UT) or 1:07 PM Eastern Standard Time (EST). This is also just over 10 hours after apogee, which occurs at 7:36 UT/2:36 AM EST. This month’s apogee is also an exceptionally distant one, measuring 406,385 kilometres from the center of the Earth to the center of the Moon. This is just 80 kilometres shy of the most distant apogee of 2015 on September 14th, which occurs when the Moon is near New phase.
Apogee for the Moon ranges from 404,000 to 406,700 kilometres distant, and the Full Moon appears 29.3 arc minutes across near apogee versus 34.1’ across near perigee as seen from the Earth.
This is also the closest apogee near a Full Moon time-wise until January 27th, 2032.
What is a Mini-Moon? As with a Supermoon, we prefer simply defining a Mini-Moon as a Full Moon which occurs within 24 hours of apogee. That’s much more definitive in our book rather than the cryptic and often cited ‘within 90% of its orbit’ refrain for Supermoons.
And speaking of which, we’ve got three ‘Super’ Full Moons in 2015, with the very closest Super (Duper?) Full Moon occurring within an hour of perigee on September 28th during the final total lunar eclipse of the ongoing tetrad… what will the spin doctors of the Internet make of this? A ‘Super Duper Blood Moon,’ anyone?
The path of the Moon this week also takes it towards the Fall equinoctial point in the astronomical constellation of Virgo, as it crosses Leo and nicks the corner of the non-zodiacal constellation Sextans. The Moon reaches Full two weeks prior to the Vernal Equinox, which falls this year on March 20th. Keep an eye on the Moon, as the first eclipse of 2015 and this year’s only total solar eclipse also occurs just 13 hours prior to the equinox for observers in the high Arctic. (More on that next week).
Can’t wait til Thursday? Tonight, observers across Canada, northern Maine, and Europe will see a fine occultation of the star Acubens (a.k.a. Alpha Cancri) by the 94% illuminated waxing gibbous Moon:
Alpha Cancri is 175 light years distant, and folks living along the U.S./Canadian border will be treated to a fine grazing occultation as the double star plays hide and seek along the limb of the Moon. This is number 17 in an ongoing series of 21 occultations of the star by the Moon stretching out until June 20th, 2015. There’s a wide separation of 11” between the star’s A and B components, and there are suspicions from previous lunar occultations that Alpha Cancri A may itself be a double star as well.
We caught a similar occultation of the star Lambda Geminorum by the Moon this past Friday:
Ever feel sorry for moonless Venus? This Wednesday night also offers a chance to spy Venus with a brief ‘pseudo-moon,’ as +6th magnitude Uranus passes just 15’ — less than half the apparent diameter of a Full Moon — from brilliant -4th magnitude Venus. Neith, the spurious 18th century moon of Venus lives! From the vantage point of Venus on March 4th, the Earth and Moon would shine at magnitudes -2.3 and +1.5, respectively, and sit about 4 arc minutes apart.
Does the rising Full Moon look smaller to you than usual this week? While the apparent change in diameter from apogee to perigee is slight, it is indeed noticeable to the naked eye observers. Remember, the Moon is actually about one Earth radius (6,400 kilometres) more distant on the local horizon than when it’s directly overhead at the zenith. The Moon is also moving away from us at a current rate of 1-2 centimetres a year, meaning that Mini-Moons will get ever more distant in epochs hence.
Already, annular solar eclipses are currently more common than total ones by a ratio of about 11 to 9. The first annular eclipse as seen from the Earth went unheralded some time about 900 million to a billion years ago, and 1.4 billion years hence, the last total solar eclipse will occur.
Be sure to get out and enjoy the rising Mini-Moon later this week!
-Send those Mini-Moon pics in to Universe Today. | 0.819064 | 3.206508 |
How SETI Works
The nearest planet that is similar in size to Earth and located within the narrow habitable zone of its star is unromantically named Kepler-186f. If there is life on this planet, none of us will ever know. That's because Kepler-186f is 493 light-years away [source: Vergano].
When the search for extraterrestrial intelligence (SETI) began in the 1960s, astronomers quickly dismissed the idea of physically visiting an alien planet. The technological advances necessary to shoot humans across the galaxy is, like the nearest habitable planet, still light-years away.
Instead, the SETI sciences decided to stay on Earth, but keep an ear on the heavens. If intelligent life is out there, SETI decided, then it must have an understanding of radio waves and the electromagnetic spectrum. Like us, the alien species probably doesn't have unlimited energy resources to travel around the universe looking for friends. The most efficient way to say, "Hello, universe. We're here!" is to send a radio transmission.
The next question for SETI scientists was where to listen? The best guess was promoted by two Cornell physicists in the early 1960s, Philip Morrison and Guiseppi Cocconi. The two men assumed that an extraterrestrial life-form intelligent enough to master the electromagnetic spectrum would try to craft its message in a "common language" that anyone could understand [source: Kiger].
The most common electromagnetic frequency, Morrison and Cocconi reasoned, is emitted by the most common element in the universe, hydrogen. If an alien was trying to communicate with us over an open channel, it would choose 1420 megahertz, also known as the "hydrogen line."
And so began the search for alien life. Using large radio telescopes, astronomers focus on one tiny patch of sky and listen for the faintest sign of an unusual transmission coming over the 1420 MHz frequency. After listening for a few minutes, the telescope moves on to the next tiny patch of sky, and so on, and so on [source: Andersen].
And that's exactly what Jerry Ehman and other SETI volunteers were doing with the Big Ear telescope at Ohio State back in the summer of 1977. They were listening to a sliver of the sky near the constellation Sagittarius and measuring the strength of the signal picked up on the 1420 MHz channel.
Ehman and others had been at it for years, always receiving the same 1s and 2s of normal background radiation, until Aug. 15, when the Big Ear picked up a startling signal that would echo through the decades.
Next we'll find out why the "Wow!" signal makes such a great case for being a message from ET. | 0.865979 | 3.59196 |
When certain stars reach the end of their lives, they go out with massive explosions so bright and spectacular that they often manage to briefly outshine entire galaxies. This is known as a supernova, and, up at the Thacher Observatory, students in Dr. Jon Swift’s
Advanced Topics in Astronomy Research course
have had the telescope trained on a particularly interesting one throughout the fall, watching as the explosive light dims over time. The data they’re collecting may one day help scientists unravel the mysteries of the expanding universe.
The course’s main objective is to equip students with a strong foundation in astronomical concepts and quantitative research skills
so that they can springboard into their own astronomical research, emphasizing hands-on, real-world scientific inquiry through group research projects that last throughout the trimester. Seniors Katie O’Neill and Jeffrey Ding focused on supernovae throughout the fall, a project that was inspired by a partnership with Dr. Ryan Foley
at the University of California, Santa Cruz (UCSC). His research on the expansion of the universe includes the study of supernovae; when his team identified an interesting supernova subject in July 2017, the Thacher Observatory began tracking it. Now, Katie and Jeffrey have amassed over six months of data.
“Supernovae are interesting to astronomers because most behave in very similar ways, meaning that they can be easily identified and cataloged even when they are very far away or very old,” describes Katie. “Astronomers can then use this information to calculate how fast the supernova was moving away from us at that point in time. By observing many supernovae, they can get a sense of the overall rate of expansion of the universe.”
“Dr. Ryan Foley’s team at UCSC started a large-scale project to identify, observe, and analyze nearby supernovae, and we are helping this effort through our observations,” she continues. “The supernova we’ve been observing is relatively nearby and we have very frequent and high-quality data, so we're both contributing to the overall understanding of it and serving as a check on Dr. Foley’s team’s independent data and analysis.”
Now, they’re looking to add a new dimension to their research. At the end of September 2017, Katie and Jeffrey, with the support and guidance of Dr. Swift, put together and submitted a proposal to the Las Cumbres Observatory
(LCO) in Goleta with the hopes of earning time on LCO’s fleet of professional telescopes around the world to collect data that is outside current campus capabilities.
“Jeffrey and I wrote and submitted our proposal to LCO for time on the FLOYDS spectrograph early this fall,” says Katie. Unlike Thacher’s telescope, which currently can only produce images, a spectrograph would allow them to observe the chemical signature of their source by creating a spectrum from astronomical light.
At the end of October 2017, Katie, Jeffrey, and Dr. Swift found out that they had been granted two hours at LCO.
“To be awarded time is a huge honor, and speaks volumes about the quality and relevance of the work our students are doing here,” said Dr. Swift.
He added: “Katie and Jeffrey showed an impressive knowledge of the capabilities of our observatory and a broad understanding of cutting-edge research on supernovas to construct a compelling proposal to use LCO’s largest fleet of telescopes to complement the science we can do here on campus. I was very impressed with their work, and I only needed to offer cosmetic edits to their proposal before submission.”
“Katie and Jeffrey’s efforts not only open the doors to further work with LCO but show that we have high caliber students worthy of receiving time on professional astronomical facilities for research purposes.”
Katie said of their success in earning time at LCO: “It’s incredibly exciting to be working with a professional observatory and this will help to further establish Thacher as a legitimate scientific facility.”
In the meantime, Katie and Jeffrey will continue to work on their supernova research throughout the winter term in Dr. Swift’s class. Dr. Foley visited Thacher in the late fall from UC Santa Cruz to work with them and other astronomy students, helping them deepen their knowledge base and increase their familiarity with the workings of the professional astronomical research community. Katie also plans to participate in a self-guided independent project
in the afternoons this term to fit more time for the project into her weekly schedule.
Dr. Swift says of the project and others like it: “By participating in real, meaningful science
I see these students solidifying their classroom skills, synthesizing ideas across disciplines, and learning how to put their knowledge to use toward a worthy goal. They quickly realize that science is not just a bunch of laws, rules, and equations. Rather, like any other human endeavor, it has many facets—creative, social, and political.” | 0.849512 | 3.808279 |
Since the beginning of the space age, the environment outside Earth’s neutral atmosphere has been a laboratory for fundamental plasma physics, for the interaction of the solar wind with the bodies of the solar system, and for phenomena that impact our daily lives. Dr. Thomsen has been at the forefront of space plasma research throughout her career. Her work blends discovery, insight, theory, and skillful data analysis. It has left its mark on our cumulative knowledge and on numerous young scientists mentored by her.
The International Sun-Earth Explorer (ISEE) spacecraft made pioneering observations of the shock formed by the supersonic solar wind encountering Earth’s magnetosphere. The universality of shock waves, their implication in generating cosmic rays, and the contradiction between the collisionless nature of interplanetary space and the requirement for shock dissipation fueled intense scientific activity. Dr. Thomsen discovered the mechanisms for energy partition among electrons, ions, and suprathermal particles and their primary dependence on shock conditions. She discovered intense explosive events, known as hot flow anomalies, capable of distorting the magnetosphere. Her studies of shock particle acceleration and magnetic structure represent both the discovery and comprehensive underpinning of modern shock physics.
Dr. Thomsen exploited the Los Alamos geosynchronous data sets to reveal the dynamics of Earth’s magnetosphere. She demonstrated that intense space weather events require a combination of interplanetary conditions and the state of the plasma in the magnetotail, thus linking bursty flows in the magnetotail to the intensity of geomagnetic activity. Her insight into magnetospheric flows led her to underpin the physics of the Kp index as a measure of activity.
Dr. Thomsen’s masterful analysis of in situ plasma data led to several important studies at Saturn, including the identification of plasmoid structure in its magnetotail. This confirmed the operation of magnetic reconnection in the Saturnian magnetosphere, attributing simultaneous measurements of energetic neutrals to charge exchange with the reconnection-accelerated ions. Her expertise in the Cassini Plasma Spectrometer (CAPS) instrument led to the first discovery of cold charged nanometer-size water ice grains in the geyser plumes from the moon Enceladus. Such grains had been hypothesized to exist in a number of astrophysical contexts.
Throughout all these scientific advances, Dr. Thomsen mentored numerous students and postdocs in the art of rigorous scientific discovery. She has played active roles in community service at local and national levels. She epitomizes the qualities of scientific excellence and leadership that have led to her Fleming Medal.
—Steven J. Schwartz, Laboratory for Atmospheric and Space Physics, University of Colorado Boulder; also at Imperial College London, U.K.
I am deeply grateful to be receiving the Fleming medal, but I feel strongly that it should really be awarded to an entire community of space scientists. Space science, especially work based on spacecraft measurements, is not a lone-wolf operation. In my entire list of publications, only two are sole authored. The rest either have at least one (and often several) coauthor or else were first authored by someone else. In fact, the best papers were generally not mine! At last count, 155 of my colleagues have granted me the privilege of participating in their research. And I haven’t counted them, but probably many more than that have contributed their expertise and insight to my own work. Some of these colleagues read like a Who’s Who of space science, and others were youngsters, just setting out on the grand adventure. To all of them I am deeply grateful for the collegiality and unselfishness that has marked our journey.
I have also been greatly privileged to be able to participate in a number of groundbreaking missions, including the first spacecraft measurements of Jupiter’s and Saturn’s magnetospheres, the first high-resolution measurements of Earth’s bow shock, the first in situ observations of a cometary coma and tail, unique plasma measurements from a six-spacecraft constellation of geosynchronous satellites, in-depth plasma and composition measurements from 8 years of Cassini’s orbit around Saturn, and the rich new plasma data from Juno at Jupiter. The instruments that returned the data from these missions were a marvel of design and construction, and I am greatly indebted to all the scientists, engineers, and other support personnel whose efforts produced such great scientific opportunity. And finally, I am grateful for the encouragement and support of my wonderful family, who have made it possible for me to pursue such a richly rewarding career. I am therefore pleased to accept the Fleming Medal on behalf of the entire “village” of people who have brought us to this day.
—Michelle F. Thomsen, Planetary Science Institute, Tucson, Ariz. | 0.888008 | 3.894262 |
Gravitational lenses have long been one of astronomy’s white whales, perplexing those who have devoted themselves to finding and studying them.
But by applying deep learning and computer vision to the abundant data generated by today’s powerful telescopes, scientists are on the verge of being able to use hundreds of thousands of gravitational lenses to expand our understanding of the universe.
Gravitational lenses occur when a galaxy, or a cluster of galaxies, blocks the view of another galaxy “behind” it, and the gravity of the first causes the light from the second to bend. This effectively makes the first galaxy a sort of magnifying glass for observing the second.
By first conclusively identifying gravitational lenses — which has proven to be a huge challenge — and then analyzing the telescope data, scientists not only can better observe those more distant galaxies, they also can gain understanding of the nature of dark matter, an unknown form of matter which seems to permeate our universe.
“There is lots of science to be learned from gravitational lenses,” said Yashar Hezaveh, a NASA Hubble postdoctoral fellow at Stanford University’s Kavli Institute for Particle Astrophysics and Cosmology. “We can use the data to look into the distribution of dark matter, and the formation of stars and galaxies.”
Delving Into Deep Learning
Until recently, scientists used large and sophisticated computer codes to analyze images. This required very large computations on superclusters and a significant amount of human intervention. But when Hezaveh and his team of researchers decided to apply computer vision and neural networks, everything changed.
“We had no expectations of how awesome it was going to be, or if it was going work at all,” said Laurence Perreault Levasseur, a postdoctoral fellow at Stanford University and a coauthor of a paper on the topic.
Another way to think about gravitational lenses is as funhouse mirrors, where the challenge is to remove the effect of mirror distortions and find the true image of the object in front of it. Traditional methods compare the observations against a large dataset of simulated images of that same object viewed in different distorted mirrors to find which one is more similar to the data.
But neural networks can directly process the images and find the answers without the need for comparison against many simulations. This can, in principle, speed up the calculations. But training a deep learning model that can understand how the various undulations affect the behavior of matter, not to mention our view of it, also requires enormous computing power.
Once Hezaveh and his team adopted GPUs to analyze the data, they had the speed and accuracy needed to unlock new knowledge of the universe. Using Stanford’s Sherlock high performance computing cluster, which runs on a combination of NVIDIA Tesla and TITAN X GPUs, the team was able to train its models up to 100x faster than on CPUs.
The resulting understanding of gravitational lenses is expected to provide a lot of fodder for those trying to understand the universe better.
“A lot of scientific questions can be addressed with this tool,” said Perreault Levasseur.
Wanted: Gravitational Lenses
Of course, to analyze data on gravitational lenses, you first have to find them, and that’s where complementary research underway by scientists at three universities in Europe comes into play.
Researchers at the Universities of Groningen, Naples and Bonn have been using deep learning methods to identify new lenses as part of the Kilo-Degree Survey (KiDS), an astronomical survey intended to better understand dark matter and the distribution of mass in the universe.
Carlo Enrico Petrillo, coauthor of a paper detailing the deep learning effort, said as many as 2,500 gravitational lenses could be uncovered using AI in conjunction with KiDS, even though the survey is only observing a small sliver (about 4 percent) of the sky.
But there was one significant challenge to making this happen: The lack of the kind of significant training dataset deep learning applications typically require. Petrillo said his team countered this by simulating the arcs and rings that surround gravitational lenses and incorporating them into images of real galaxies.
“In this way we could simulate gravitational lenses with all the specific characteristics, such as resolution, wavelength and noise, of the images coming from the surveys,” said Petrillo.
In other words, the team treated the problem as one of binary classification: galaxies surrounded by arcs and rings that match the simulations are labeled as lenses, and those that don’t are labeled as non-lenses. As the network learns from each simulation, researchers can narrow down candidates. The group’s paper notes this method initially enabled them to whittle 761 candidates down to a list of 56 suspected gravitational lenses.
NVIDIA GPUs helped to make this possible by slashing the time it takes to run a batch of images against the simulations. Doing so on a CPU required 25 seconds per batch, but a GeForce GTX 1080 GPU provides a 50x increase in speed. (The paper details results on an older generation GeForce GPU, but Petrillo recently upgraded to the newer one.)
“Using the CPU would have made my job hell,” he said.
Data Deluge Coming
As the innovations in telescopic and deep learning technology continue, the amount of data on gravitational lenses figures to increase substantially. For instance, Petrillo said the European Space Agency’s Euclid telescope is expected to produce tens of petabytes of data, while the Large Synoptic Survey Telescope in Chile will generate 30 terabytes of data each night.
That means lots of data to crunch, many gravitational lenses to be discovered and new space frontiers to be grasped — so long as scientists can keep up.
“Having a lot of lenses means building an accurate picture of the formation and evolution of galaxies, having insights on the nature of dark matter and on the structure of the space-time continuum itself,” said Petrillo. “We need efficient and fast algorithms to analyze all this data and, surely, machine learning will be common business among astronomers.” | 0.819757 | 4.108705 |
On the South Island of New Zealand, the Mahuika Comet impact would have been a dramatic event. Within 50 km of the southern coastline, it would have appeared as a fireball ten times larger than the sun, blown over 90% of the tree cover, and ignited grass and trees (Marcus et al. 2005). However, these effects would have ceased within 100 km of the coast. Steel & Snow (1992) believe that local Maori legends and place names refer to a comet event such as this one. They base their hypothesis on the legend of the “Fires of Tamatea” (or Tamaatea). Local ethnographic evidence is best chronicled in the Southland and Otago regions, centred on the town of Tapanui. Here there appears to be evidence for an airburst that flattened trees in a manner similar to the Tunguska event.
The remains of fallen trees are aligned radially away from the point of explosion out to a distance of 40–80 km. Local Maori legends in the area tell about the falling of the skies, raging winds, and mysterious and massive firestorms from space. Tapanui, itself, translates as ‘the big explosion,’ while Waipahi means ‘the place of the exploding fire’. Place names such as Waitepeka, Kaka Point, and Oweka contain the southern Maori word ka, which means fire. The local Maori also attribute the demise of the Moas, as well as their culture, to an extraterrestrial event. The extinction of the Moa is remembered as Manu Whakatau, ‘the bird felled by strange fire’.
Fires of Tamatea
These interpretations have been criticized by Goff et al. (2003). Specifically, they state that the local place names referring to a cosmogenic fire event requires ‘an in-depth knowledge of the culture and traditions of the Maori people’ and interpretation requires the use of ‘many references with cross-referencing between them . . . as opposed to citing an individual reference’ (Goff et al. 2003). We have since gone back to an original source, The Maori-Polynesian Comparative Dictionary compiled by Tregear (1891). The dictionary is based on over 160 references and traces Maori terms back to their Polynesian sources. It supports some of the interpretations made by Steel and Snow (1992). The dictionary refers to Tamatea as a very ancient person. He was the fifth in descent from Rangi, the Sky. The Fire of Tamatea refers to an older legend related to some volcanic catastrophe or conflagration before the Maori came to New Zealand. Tapanui, which is at the centre of Steel and Snow’s (1992) cosmic firestorm, lies at the edge of the destructive effects of the Mahuika impact. Masse & Masse (2006) describes legends in South America referring to wildfires caused by cosmic airburst events. He also notes that although the fires had a cosmogenic source, few legends mention this fact.
Masse (1995) also points out that some Polynesian place names and the names for legendary heroes or supernatural beings can be broken down into their literal components. In this sense, the place name Tapanui (great or large tapa) may relate to the meaning of tapa, which in the 1891 Maori-Polynesian Comparative Dictionary translates as ‘to split’or ‘to pulverize soil’ (Tregear 1891). Similarly, the word ka appears in this dictionary as meaning ‘to burn, to be lighted, to take fire’, while kaka means ‘red-hot’ (Tregear 1891). Nowhere in Maori or Polynesian sources does it mean ‘fever’ as stated by Goff et al. (2003). Possible age of the recent cosmogenic tsunami event.
Dating the Maori Fires of Tamatea and the Mega Tsunami
It is possible to constrain the age of a regional cosmogenic mega-tsunami event and with it many associated Aboriginal and Maori legends using four separate lines of evidence. First, it is possible to surmise the most likely time of meteorite and comet impacts over the last two thousand years using a combination of Chinese, Japanese, and European records of meteor, comet, and fireball sightings. Figure 3 plots the accumulated record, up to the beginning of the nineteenth century, when scientific observations began in earnest. The meteorite records for China and Japan are based upon Hasegawa (1992), while meteorite records for Europe come from Rasmussen (1991). The Asian meteorite records are the most complete with European sightings accounting for less than ten percent of the record over the last one thousand years. The comet record from Asia is based upon Hasegawa (1992). A quasi-cyclic pattern is evident in the comet sighting records that can be linked to the dominance of the Taurid complex in the inner solar system. This complex formed from the breakdown of a giant comet that entered the inner solar system about 15 000 years ago (Asher & Clube 1993; Asher et al. 1994). Recent times when the Earth crossed the trail of this comet debris occurred during 401–500, 801–900, 1041–1100, 1401–1480, 1641–1680 and 1761–1800.
By far the most active period of the past two thousand years happened between AD 1401 and 1480. Second, twenty-nine radiocarbon dates have been obtained from marine shell found in disturbed Aboriginal middens, deposited in tsunami dump deposits and sand layers, and attached to boulders transported by tsunami along the New South Wales coast (Bryant 2001). Some of these dates were obtained from the Tura Point area where mega-tsunami was first identified as an important coastal process in Australia (Young & Bryant 1992). The radiocarbon ages were converted to calendar ages using the INTCAL98 calibration table for marine samples (Stuiver et al 1998). The dates center on the year AD 1500 +85. These dates can only be stated as the most probable time for the deposition of marine shell by tsunami because the flux of atmospheric radiocarbon production around this time was highly variable leading to age reversals in the marine radiocarbon chronology. Based upon the Australian east coast deposits, it is 95% probable that a cosmogenically induced mega-tsunami event occurred between AD 1200 and 1730. This span also incorporates the age of major New Zealand tsunami deposits (Goff & McFadgen 2002;Nichol et al. 2003). Unfortunately, age reversals and the absence of any cross-correlation with a genealogical record make it impossible to identify up to five regional events in New Zealand in the fifteenth century as hypothesized by Goff & McFadgen (2002) and Goff et al. (2003). A cosmogenic source must be considered given the magnitude of the event on both the east coasts of Australia and New Zealand and the widespread distribution of that evidence throughout the region.
The preference for a major impact during this period is also supported by a radiocarbon date from Stewart Island, New Zealand—the closest large landmass to the Mahuika impact site (Fig. 1c). The southern coast of this island shows massive erosion characteristic of mega-tsunami in the form of ramps, knife-like sluices and flutes cut into granite and orientated towards the impact site (Fig. 4). All of these types of landforms have been linked to mega-tsunami (Bryant & Young 1996; Bryant 2001). An age obtained from pipi (Paphies australis) located about 500 m inland and 30 m above sea level at Mason Bay on the west coast of Stewart Island yielded a corrected age of AD 1301 +36.
Third, circumstantial evidence exists for a major environmental event that disturbed coastal Aboriginal culture within this period. For example, a disturbed midden has been found 30 m above sea level within Sydney Harbour (Attenbrow 1992). This is beyond the run-up of modern storm waves in the harbour. The date of this deposit is 1448 AD. There is also clear evidence that Aborigines switched from collecting large molluscs to fishing about 500–700 years ago (Sullivan 1987). We attribute this response to the fact that any large tsunami would have wiped out shellfish populations along the rocky coast. Aborigines thus switched to fishing to survive. At Bass Point, which is dominated by mega-tsunami erosion and which is a headland conducive to the legend of the ocean falling from the sky, the change occurred around AD 1380 (Bowdler 1976). Finally, middens at various sites along the South Coast of New South Wales indicate that edible mussels originating from more protected tidal inlets began to replace gastropods originating from rock platforms concomitantly with the switch to shell fishhooks (Sullivan 1987). Fourth, it is possible to pin down the approximate age of the Fires of Tamaatea. The cosmic fires reported in Steel & Snow (1992) burnt vegetation across the South Island. There are two sources of organic material for radiocarbon dating this event: buried charcoal (Molley et al. 1963) and carbon derived from peats in swamps and bogs that have been burnt (McGlone & Wilmshurst 1999). This material traditionally has been interpreted as reflecting the time of deforestation due to Maori occupation in New Zealand. However, much of the burnt material comes from uninhabitable high country that was burnt on a vast scale. Figure 3 plots the distribution of dates, that span at least two centuries and terminate at the end of the fifteenth century. This wide range in dates is logical knowing that mature trees, already hundreds of years old, burnt. Goff et al. (2003) criticize this dating, pointing out that it is inaccurate, that there are ambiguous regions in the distribution of the dates, and that they peak before one in the observation of comets and meteorites. Even so, Bryant (2001) never tried to interpret the dates beyond the crucial point ‘that few ages occur after the fifteenth century’ concomitant with the peak in meteorite and comet observations. Even the replotting by Goff et al. (2003) of their corrected dates supports this assertion. The Fires of Tamaatea legend may well have a cosmogenic origin. More importantly, the timing of the fires is also coherent with the dating of mega-tsunami deposits along the adjacent coastline of Australia and New Zealand. These four lines of evidence all indicate that a regional mega-tsunami event that was probably due to a comet impact in the fifteenth century. | 0.840248 | 3.552094 |
Explaining nearby objects that are old in time dilation cosmologies
One of the problems with time dilation theories is that they explain objects at cosmological distances but not objects in local space. How can old objects exist in nearby space, such as the white dwarf (WD) star orbiting Sirius.
Sirius B is a Carbon-Oxygen (C-O) WD with a measured temperature of 25,000 K.1 Like other WDs, it has no energy source but is steadily cooling down from its former hot stellar state. In fact, Sirius is itself a mature, spectral type A1V star only 2.6 parsecs (8.6 light-years) distant from the sun. Its white dwarf exhibits an elliptical orbit which varies from 8.1 to 31.5 Astronomical Units (1 AU is equal to the semi-major axis of the earth as it orbits the sun, or the average distance between the two bodies), so it has little interaction with its companion. The binary system is thought to be about 200 Ma years old, based on stellar evolution and cooling rates of WDs (see the Solar Age Condition, or SAC,2 which brings these large absolute ages into doubt).
C-O WDs are cores of massive stars that began with masses 4–5 times that of the sun. These systems have gone through various nuclear burning stages, the first core burning hydrogen to helium. After the hydrogen burns itself out, it continues on to shell burning, leaving the helium ‘ash’ in the core. As the core helium increases in density, its pressure and temperature also rises. Finally, after a stage of degeneracy, it attains a temperature of about 100 million K and begins burning the helium, converting it to carbon and oxygen. The core never attains a temperature high enough to burn the C-O products. But it goes through an unstable ‘AGB’ stage as a red giant, where it loses a great deal of its mass to the interstellar medium. The leftover debris is called a planetary nebula. The final WD, called Sirius B, has a mass of only one solar mass.1 So it is believed to have lost 80% of its previous mass.
How does such an old system exist near our youthful, directly created solar system, which is less than 10,000 years of age?
The answer is the existence of a timeless region!3 Russ Humphreys found that there is a timeless region inside the white hole (or a black hole for that matter) (see figure 1).
In the ‘White Hole’ (WH) cosmology of Russ Humphreys or in his more recent cosmology,3 as long as the earth is inside the event horizon of the WH (and therefore inside the timeless region), objects outside of it continue to age and their light continues to impinge upon the earth. So nearby objects are old in the model. That is the simple answer. The actual details may be more complex. For this process to work up close to the solar system, the event horizon may have dispersed (evaporated) somewhere between the solar system and the nearest mature star, Proxima Centauri, about 4.2 LYs away. This would allow ageing in the Centauri system also. The minimum radius to take in the entire solar system, including the Kuiper Belt, is ~70 AU. This would require the presence of a 3.5-billion-solar-mass singularity at the core to maintain a 70-AU-radius WH. (Here we have ignored the Oort Cloud since there is no direct observational evidence for its existence.)
Of course, it’s not only the earth that’s within the white hole as it collapses but the entire solar system, including the sun, created on Day 4. The singularity will cause the ageing process of objects external to the white hole as seen from the earth to continue until the event horizon gets close. After it loses sufficient matter, we would expect the WH to evaporate and the time dilation apparent to Earth-based observers to cease. All other related phenomena that affect space-time would also cease, e.g. blue-shifts. The WH would evaporate quickly as the event horizon collapses inward and all matter leave the timeless region, much the same as a miniature black hole does.
References and notes
- Holberg, J.B., Oswalt, T.D. and Barstow, M.A., Observational constraints on the degenerate massradius relation, The Astronomical J. 143:68, 2012. Return to text.
- Samec, R.G. and Figg, E., The apparent age of the time dilated universe I: gyrochronology, angular momentum loss in close solar type binaries, CRSQ 49(1):5–18, 2012. Return to text.
- Humphreys, R., New time dilation helps creation cosmology, J. Creation 22(3):84–92, 2008. Return to text. | 0.857341 | 4.052956 |
There is one moment that haunts Larry Crumpler. He’s a volcanologist who has been on the science teams of several Mars missions, but most prominently as part of the daily operations of NASA’s Mars Exploration Rovers. The rovers, Spirit and Opportunity, landed on opposite sides of the planet in 2004. In 2007, Spirit passed through an area with some lava that got Crumpler’s attention. “We were on a slope, above which was an escarpment with basaltic rocks that had just tumbled down,” he says. “There was a big one right there, just a few meters away.” Spirit was so close. If he could just drive the rover over and examine the rock up close, he might discover whether the lava had flowed onto ice, water, or dry soil. He might discover evidence, in other words, of water—exactly what the mission was sent to find.
But almost from the start, Spirit’s journey had been rougher than Opportunity’s. In 2006, its right front wheel broke—the team kept the rover moving by driving it backward, dragging the broken wheel behind it. Spirit almost certainly wouldn’t be able to climb the slope to reach the rock. Besides, there were many scientists on deck, eager to drive onto their own targets. “We had a naming theme then that was [based on] Antarctic stations, and that rock’s name was Orcadas,” Crumpler recalls. “Most team members have probably forgotten about that rock,” he says wistfully, “but not me.”
This was one in a series of lows and highs—of tantalizing but unreachable goals and triumphant discoveries—that has defined the long journey of the Mars Exploration Rovers. Spirit’s mission and the hopes of inspecting any more rocks ended in 2010, when the rover got stuck in a sandy patch and eventually ran out of power. But its twin, Opportunity, is astonishingly still motoring around the Red Planet. The rover, which the mission team initially hoped would last at least 90 days on Mars, is now in its 14th year of exploration. Opportunity has traveled 28 miles over the dusty, challenging Martian terrain, and shows no signs of ending its journey anytime soon. (Spirit traveled almost five miles; NASA’s Curiosity rover, which landed in 2012, has traveled a little more than 10.)
Here on Earth, a team of scientists and engineers have dedicated much of their careers to the rovers, some for as long as three decades, going back to when the mission was first conceived. Planetary scientist and principal investigator Steve Squyres was on the Voyager and Cassini teams, and contributes to several other Mars missions. John Callas, a physicist who has worked on seven other Mars missions, is Opportunity’s project manager. Squyres, Callas, and Crumpler have plenty of memories to share about the experience of driving an explorer inch by inch around an alien landscape 34 million miles away.
What was the trickiest driving experience?
“Opportunity drove into a dune and got buried up to its axles” in 2005, Crumpler says. The rover is designed to drive over both hard surfaces and soft soils, and to climb over obstacles up to 10 inches high. Yet Purgatory, the name the team gave the sandy ripple that turned into a sand trap for Opportunity, was about a foot tall and eight feet wide: the outer edge of the rover’s capabilities. “Although we had crossed ripples before, none were quite like Purgatory in size and its complex, asymmetric structure,” Callas says.
Complicating the problem was the communications delay. The rover team typically sends up all the instructions for the day’s operation, and the rover downloads its report several hours later, when one of the satellites orbiting Mars passes and can relay the information to Earth. So when Opportunity’s wheels started digging into the dune, it just kept on pushing forward as instructed. By the time it stopped for the day and the team discovered the problem, it was mightily stuck.
“We realized how serious this was, and we had to spend a lot of time understanding the situation and trying to re-create it on the ground,” Callas says. Luckily, brute force was the answer: “We just spun the wheels backwards and allowed enough time”—almost three weeks—“and it eventually popped out.” By the time Opportunity finally backed three feet out of the sand, its wheels had turned enough to move it 629 feet.
The team reprogrammed the rovers to stop driving if they haven’t moved as far as the number of wheel rotations should have taken them. Still, it was this very problem that proved to be fatal for Spirit. In 2009 the rover drove toward an area that was smooth and strewn with pebbles, indicating what seemed to be a hard surface. “We started driving and we broke through a crust that was a couple of centimeters thick into powdery dust,” Crumpler says. “What looked like a perfectly rocky surface was worse than quicksand.” Engineers spent nearly nine months trying to extract the rover from the trap. In 2010, Spirit sent its last communication to Earth.
What was your scariest moment?
“About three years into the mission, we had a global dust storm on Mars that darkened the sky to where less than one percent of the sunlight reached the surface,” Callas says. “These are solar-powered rovers. Without sunlight, they can’t be powered, and importantly, we can’t use that power to keep the rover warm.”
The manufactured heat is what protects the rover’s electronics at night on Mars, when it can get down to -150 degrees Fahrenheit. As the storm began, the team instructed the rover to wake up each day just long enough to warm itself, and not to use any energy for communications. “That was nerve-racking because we waited four days,” Callas says. “It was quite exciting when the signal came in right on time and we knew the rover was okay.”
A few years ago, Opportunity suffered a somewhat relatable problem. “The rover would wake up in the morning, and it didn’t remember anything about yesterday. ‘What plan? You didn’t send me a plan,’ ” says Crumpler. Then the next day the rover would remember fine, but a few days or weeks later it would happen again. That overnight recall uses the rover’s long-term, or flash memory. The team eventually resolved the situation by using only RAM memory, a strategy that created a new problem: When Opportunity is put into sleep mode at night, the data that it collected that day is erased. “That means we have to keep the rover awake until the overflight of that orbiting spacecraft,” Crumpler says.
Steve Squyres has a different scariest moment. He still remembers the tense days just before Opportunity’s landing. Spirit had arrived on Mars first, and about two weeks later, “we lost [communications with] the vehicle. The computer on board was crashing and rebooting every 15 minutes. The Opportunity landing was scheduled to happen 21 days into Spirit’s mission. So at the very same time that we’re dealing with possible loss of one vehicle, we’re getting ready to land the other one.” Then they discovered a dust storm was incoming, which would change the density of the atmosphere and affect Opportunity’s descent. “If we had gone with our original plan for how to deploy the parachute, we would have deployed the parachute too low. I can remember sitting in a control room with Spirit apparently dead, or least not talking to us, and Opportunity barreling in on the planet with a dust storm going on and thinking, We’ve put 16 years into this, and it could all be over tomorrow.” It’s a story he understandably feels better telling 14 years later.
What was your biggest surprise?
“The big surprise was how scientifically diverse and fascinating Mars turns out to be,” says Squyres. “It’s a far more interesting and complicated place than I had ever imagined.” Not only did the team find evidence of water, it also showed that the planet had experienced more hydrothermal activity in the past than scientists had expected. Crumpler was surprised that “Mars has a geological terrain that is pretty much like Earth’s. When you go to the moon, it’s all smashed, all gray, and there are big [terrain features] that are tens of kilometers across. Mars is just like the geology here on the Earth, same scale, same sort of detail, same ability to do stratigraphy”—that is, to study layers of deposits.
Crumpler’s surprise comes back every day that Opportunity wakes up again to keep exploring. “Fourteen years on a planet that’s about as cold as Antarctica and dustier than any dusty place on Earth, really fine dust, and temperature swings of 100 degrees Celsius [212 degrees Fahrenheit] every day. That has to tweak a circuit board if anything will,” he says. But Opportunity keeps humming along through all of it. Squyres jokes that one lesson he learned about being on a team driving rovers on Mars is to “get lots of exercise and eat healthy foods because it could go on for a while.”
What is the strangest photo Opportunity has taken?
Callas says that many of the photos can make you do a double-take, because you’ll see things that look like manufactured objects. “When you’re photographing geology, you get a variety of shapes and sizes,” he says. “As humans, we’re very good at recognizing patterns in chaos.” But what has impressed him most are the beautiful landscape photos of the Martian surface, particularly sunsets. “On Mars the sunset colors are backwards from what they are on Earth because you have a pink sky and a blue sunset.... You realize that it’s the same sun but two different worlds. That’s what makes that image look so remarkable.”
“Very high on my list would be the first microscopic imager picture of the things we came to call ‘blueberries’ at the Opportunity landing site,” Squyres says. “There are these uncountable number of little perfect spheres. That was pretty weird.” In the following years, Opportunity found clusters of blueberries at other locations, both on the surface and buried in the soil. The spheres are actually gray, but they appear blue in images that use false-color technology to emphasize details. Scientists determined that the spheres, a few millimeters in diameter, are made of an iron oxide called hematite and were likely formed by water from precipitation that flowed through rocks.
What was your hardest decision?
Though Crumpler credits much of the mission success to the congeniality and cooperation among the team members, he sometimes laments having to share Opportunity with so many other scientists eager to see Mars, as he did when he lost the chance to send Spirit to examine Orcadas. “The hardest decision is always not pursuing something that you really wanted to,” because the rover has to keep moving. “But if you were ruler of the universe, that’s what you’d do.”
Callas anticipates his hardest decision regarding Opportunity is going to be a moment in the future—one he already experienced at the end of Spirit’s mission, in May 2011. They had already lost communication with the rover in March 2010. “We weren’t sure that it had actually failed,” he recalls, “but may have been in some sort of a fault condition. So we sent something of the order of 1,400 commands to the rover at different times, in different ways, in order to elicit a response. And we did it over an extended period. Eventually, you have to say ‘That’s enough,’ ” and you have to say goodbye.
Squyres faced one of his hardest decisions in 2008, after Opportunity had spent two years exploring Victoria Crater. “We had to decide what to do next,” he says. “Surrounding us in every direction, we had pretty much the same stuff that we had been seeing.” Off in the distance, Endeavour Crater looked like an attractive destination that could be geologically different. “But it was 16 kilometers [10 miles] away and it was six years into the mission, and we had a vehicle that was designed to last for three months and drive one kilometer. I made the decision to go.” It took Opportunity three years to reach the new target, during which it accomplished little science. “We came ashore at Endeavour Crater and everything changed,” Squyres says. “It was like a brand-new mission. The science was completely different. That decision was tough at the time, but I think it paid off.”
What has been the rovers’ greatest discovery?
The rovers’ landing sites were chosen for their likelihood of harboring evidence of past water. Finding it would prove that Mars was, at some point, potentially habitable. The team chose Meridiani Planum as Opportunity’s landing site because it had mineral concentrations that were likely formed in liquid water. Spirit descended into Gusev Crater, which appeared from orbit to be the site of a former lake. “Our expectation was we would find lakebed sediments where we landed with Spirit,” Callas says. “Instead, we found only volcanism, chunks of lava as far as the eye could see. That was initially a scientific disappointment.” But the lava was fascinating for Crumpler. “I really didn’t anticipate that we would see the variety of volcanic phenomena that we saw.”
But it wasn’t long before both of the rovers found unambiguous evidence of what the scientists were most seeking. “The greatest discovery is the fact that every rock we look at has been affected by water,” Crumpler says. “You’d expect to see a little bit of interaction with water, but we’re talking about being really soaked in water, corroded with water, turned to mush from sitting in water for long periods of time.”
The promise of new discoveries, along with Squyres’ difficult decision to try to reach the distant site, made Endeavour Crater his most anticipated destination. At 14 miles wide, Endeavour would be the largest Martian crater ever visited. The rocks exposed by the impact would be the oldest examined up close—it was a direct look into the planet’s history, and it proved that Mars was at some point potentially habitable.
Crumpler says another interesting discovery rewarded them at Endeavour. Marathon Valley is a deep, road-like trough cutting through the rim of Endeavour crater. The drive revealed a startling formation. Craters on Earth and Mars craters observed from orbit suggested that rock layers in the rims would tilt outward because of the force of the meteor impact. “Not so,” Crumpler says. “Everything we have seen dips into the crater. Bizarre.”
Callas’ choice is Spirit’s discovery of ancient hydrothermal systems, where water once drained into the ground and was heated, which caused it to circulate. It’s a discovery that happened after they began driving the rover backward, dragging the broken wheel. “That wheel would dig up material as it went along,” says Callas. “It dug up this very white material, which turned out to be evidence of a hydrothermal system. If we had a fully functional wheel, we would have just blazed on by and never seen it.”
Why do people anthropomorphize the rovers?
At almost five feet high, Opportunity is a bit smaller than the seven-foot Curiosity rover, but much bigger than Sojourner, which landed in 1997 and was only a foot tall. Opportunity allowed scientists to see things “at the human scale,” says Crumpler.
Squyres adds that it’s more than just the twin rovers’ size: “They take a look around, they see something interesting, they travel over to it, they look at it carefully, they make discoveries, they get confused—well, we get confused.” All that can make it difficult not to become emotionally attached. “They are robots, I get it,” Squyres says. “We made them. They’re made of metal. They don’t have brains, they don’t have personalities…but they kind of do.” Callas agrees: “They’re dutiful and intrepid and responsive, and occasionally they can be recalcitrant.”
And there’s another lifelike aspect. “The vehicle is wearing out,” Squyres says. “Some parts don’t work as well as they used to. Some parts don’t work at all anymore. It’s kind of like growing old. We’ve upgraded the software over the years, so it’s less physically capable, but it’s wiser than it used to be. When Opportunity finally does die and the mission’s over, I’m going to miss it terribly.” | 0.914178 | 3.653178 |
The Transit of Venus, in Orrery Form
On rare occasions, the planet Venus reaches a point in its (and Earth's) orbit around the sun such that we can see Venus as a dark spot moving across the sun. Known as the transit of Venus, it's a bit like an eclipse, except Venus is so far away that it shows up as just a dot, rather than blocking out much of the sun (which is what our nearby moon can do).
In 1627, Johannes Kepler successfully predicted the transit of Venus coming in 1631, though unfortunately it wasn't visible in most of Europe. But because transit events occur in pairs, eight years apart, the next transit in 1639 was observed by several scientists, which helped establish the size of Venus and make a rough estimate of the distance from the Earth to the sun (as astronomical unit, or AU). This set expectations for the next set of transits, which would happen in 1761 and 1769, the latter of which saw scientists attempt to view the transit from various points around the world.
In this video, Brady Haran and James Hennessy examine an orrery (model of the solar system) from the 1760s that explained to the layperson how the event would occur, in an extremely miniaturized and simplified form. This orrery is stored at the Royal Society in London. Amazingly, the 250+ year-old orrery still works, though it's fragile. Have a look, and learn a little more about the history of these events:
There were further transits in 1874, 1882, 2004, and 2014. If you missed the recent ones, you're out of luck, as the next transit will not occur until 2117. You might catch Halley's Comet in 2062, though. | 0.901297 | 3.594733 |
NEXT STOP: URANUS!
Unlike any other planet in the solar, Uranus (Ur-uh-nus)’s name derives from Greek mythology, namely the Greek god of the sky. Uranus preceded Jupiter and Saturn in mythology as he and Gaia created the sky and earth. Named planets long after the ancient planets (Mercury, Venus, Mars, Jupiter, and Saturn), Uranus (Sir William Herschel, 1781) and Neptune are sometimes in a separate category called the “ice giants.” The two planets’ icy blue coloration comes from a primary composition of more heavier elements, “ices” such as water, ammonia, and methane. Like Venus, Uranus spins in a retrograde motion with a tilt of 97.77°! So, while other planets spin like spinning tops, Uranus spins like a rolling ball. A large object may have knocked Uranus on its side! Uranus’ rings spin parallel to its axis of rotation. Because of its unusual axial tilt, Uranus has unusually long seasons— each pole gets 42 years of sunlight followed by 42 years of darkness. Near the time of equinoxes, however, Uranus’ day-night cycle reaches that of those on other planets. Even Uranus’ magnetic field, with a tilt of 59º, is abnormal and does not line up to Uranus’ axis, with the north side strong and the south side comparatively weak. The second least dense planet, Uranus comprises of a rocky core, icy mantle, and an outer hydrogen and helium envelope. Because Uranus’ atmosphere is mainly methane, the planet is very smelly, like cow pastures. Uranus’ faint rings were mainly formed from scattered moons. Unlike the other gas giants, Uranus radiates hardly any heat; the planet’s core may have been depleted in an high-mass impact. Though Uranus is bland, dark spots like those usually found on Neptune, have recently been found on Uranus.
Uranus has 27 known moons named after characters from Shakespeare’s and Alexander Pope’s masterpieces. Uranus’ five main moons are Miranda, Ariel, Umbriel, Titania, and Oberon. These moons are comparatively and dull (brightness), comprising of 50% rock and 50% ice. Of the satellites, Ariel is the youngest with few impact craters and Umbriel is the oldest. Miranda has canyons, layers, and many variations in surface features caused by tidal heating (push and pull of the moon’s interior caused by gravitational pull) within the moon.
MISSIONS: Voyager 2
- Order in Solar System: #7
- Number of Moons: 27
- Orbital Period: 84 years
- Rotational Period: 17 hours
- Mass: 8.6810 x 10^25 kg (14.536 Earths)
- Volume: 6.833 x 10 ^13 km³ (63.086 Earths)
- Radius: 25,559 km (4.007 Earths)
- Surface Area: 8.1556 x 10^9 km² (15.91 Earths)
- Density: 1.27 g/cm³
- Eccentricity of Orbit: 0.044405586
- Surface Temperature (Average): 76 K
- Escape Velocity: 21.3 km/s
- Apparent Magnitude: 5.9 to 5.32 | 0.888123 | 3.773052 |
Hubble watches interstellar comet Borisov speed past the Sun [heic1922]
12 December 2019The NASA/ESA Hubble Space Telescope has once again captured comet 2I/Borisov streaking through our Solar System on its way back into interstellar space. At a breathtaking speed of over 175 000 kilometres per hour, Borisov is one of the fastest comets ever seen. It is only the second interstellar object known to have passed through the Solar System.
|Comet 2I/Borisov and distant galaxy in November 2019. Credit: NASA, ESA, and D. Jewitt (UCLA), CC BY 4.0|
In October 2019, Hubble observed the comet at a distance of approximately 420 million kilometres from Earth. These new observations taken in November and December 2019 of the comet at a closer distance provide clearer insights into the details and dimensions of the interstellar visitor .
The first image shows the comet in front of a distant background spiral galaxy (2MASX J10500165-0152029). The galaxy's bright central core is smeared in the image because Hubble was tracking the comet. Borisov was approximately 326 million kilometres from Earth in this exposure. Its tail of ejected dust streaks off to the upper right.
|Comet 2I/Borisov at perihelion in December 2019. Credit: NASA, ESA, and D. Jewitt (UCLA), CC BY 4.0|
The second image is Hubble's revisit observation of the comet near its closest approach to the Sun. There it was subjected to a greater degree of heating than it had ever experienced, after spending most of its life in the extreme cold of interstellar space. The comet is 298 million kilometres from Earth in this photo, near the inner edge of the asteroid belt. The nucleus, an agglomeration of ices and dust, is still too small to be resolved. The bright central portion is a coma made up of dust leaving the surface. The comet will make its closest approach to Earth in late December, when it will be at a distance of 290 million kilometres.
"Hubble gives us the best measure of the size of comet Borisov's nucleus, which is the really important part of the comet," said David Jewitt, a professor of planetary science and astronomy at the University of California Los Angeles, whose team has captured the best and sharpest images of this first interstellar comet. "Surprisingly, our Hubble images show that its nucleus is more than 15 times smaller than earlier investigations suggested it might be. The radius is smaller than half a kilometre. This is important because knowing the size helps us to determine the total number, and mass, of such objects in the Solar System, and in the Milky Way. Borisov is the first known interstellar comet, and we would like to know how many others there are."
Crimean amateur astronomer Gennady Borisov discovered the comet on 30 August 2019. After a week of observations by amateur and professional astronomers all over the world, the International Astronomical Union's Minor Planet Center computed an orbit for the comet which showed that it came from interstellar space. Until now, all catalogued comets have come either from a ring of icy debris at the periphery of our Solar System, called the Kuiper belt, or from the Oort cloud, a shell of icy objects which is thought to be in the outermost regions of our Solar System, with its innermost edge at about 2000 times the distance between the Earth and the Sun.
2I/Borisov may represent only the beginning of a series of discoveries of interstellar objects paying a brief visit to our Solar System. There may be thousands of such interstellar objects here at any given time; most, however, are too faint to be detected with present-day telescopes.
Observations by Hubble and other telescopes have shown that rings and shells of icy debris encircle young stars where planet formation is underway. A gravitational interaction between these comet-like objects and other massive bodies could cause them to hurtle deep into space where they go adrift among the stars.
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
Los Angeles, California, USA
Los Angeles, California, USA
ESA/Hubble, Public Information Officer | 0.91822 | 3.771872 |
Astronomers have discovered the largest known structure in the universe, a clump of active galactic cores that stretches 4 billion light-years from end to end.
The structure is a large quasar group (LQG), a collection of extremely luminous galactic nuclei powered by supermassive central black holes. This particular group is so large that it challenges modern cosmological theory, researchers said.
"While it is difficult to fathom the scale of this LQG, we can say quite definitely it is the largest structure ever seen in the entire universe," lead author Roger Clowes, of the University of Central Lancashire in England, said in a statement. "This is hugely exciting, not least because it runs counter to our current understanding of the scale of the universe."
Quasars are the brightest objects in the universe. For decades, astronomers have known that they tend to assemble in huge groups, some of which are more than 600 million light-years wide.
But the record-breaking quasar group, which Clowes and his team spotted in data gathered by the Sloan Digital Sky Survey, is on another scale altogether. The newfound LQC is composed of 73 quasars and spans about 1.6 billion light-years in most directions, though it is 4 billion light-years across at its widest point.
To put that mind-boggling size into perspective, the disk of the Milky Way galaxy — home of Earth's solar system — is about 100,000 light-years wide. And the Milky Way is separated from its nearest galactic neighbor, Andromeda, by about 2.5 million light-years.
The newly discovered LQC is so enormous, in fact, that theory predicts it shouldn't exist, researchers said. The quasar group appears to violate a widely accepted assumption known as the cosmological principle, which holds that the universe is essentially homogeneous when viewed at a sufficiently large scale.
Calculations suggest that structures larger than about 1.2 billion light-years should not exist, researchers said.
"Our team has been looking at similar cases which add further weight to this challenge, and we will be continuing to investigate these fascinating phenomena," Clowes said.
The new study was published today (Jan. 11) in the Monthly Notices of the Royal Astronomical Society. | 0.820391 | 3.708879 |
One of the most ballyhooed astrophysics findings in recent memory has come under fire recently.
In March, a team of researchers announced that they had found evidence of primordial gravitational waves, ripples in space-time from the universe's earliest moments. But other scientists have already begun questioning the discovery, suggesting that it may simply be the signature of dust in our own Milky Way galaxy.
"The detection of gravity waves would be the most important physics result of the 21st century," theoretical astrophysicist David Spergel of Princeton University said earlier this month at the 224th American Astronomical Society meeting in Boston. [The Big Bang to Now in 10 Easy Steps]
However, he added, "there is no statistical evidence for the claim that gravity waves have been seen."
The evidence for inflation
Most scientists think that in the first 10-35 seconds — roughly one-trillionth of a trillionth of a trillionth of a second — after the Big Bang, the early universe experienced a rapid expansion known as inflation. In this brief moment, space-time exploded outward far faster than the speed of light. The universe continues to expand today, but at a far slower pace.
Strong evidence for inflation can be found in the cosmic microwave background radiation (CMB), the light left over from the Big Bang. Temperature variations in the CMB, which pervades the entire sky, are minor, suggesting that the universe initially came from a small region of space, researchers say.
Spergel compared the relative uniformity of the CMB to teaching a class in which all students hand in identical exams.
"That suggests there has either been communication in the room, or some information shared at the beginning," he said.
If information were shared across space-time to maintain similar conditions, it would have to travel almost instantly across vast stretches of the universe, a process most scientists consider unlikely.
Inflation would have left its mark on the CMB in the form of gravitational waves, distortions in space-time, the idea goes. Teams of researchers around the world have thus been searching for "B modes," a type of polarization in the CMB predicted to be generated by primordial gravitational waves.
In March, a team led by John Kovac, of the Harvard-Smithsonian Center for Astrophysics, reported that they had likely detected B modes using the Background Imaging of Cosmic Extragalactic Polarization (BICEP2) telescope in Antarctica. The discovery was lauded as the first direct evidence for the occurrence of cosmic inflation. [Cosmic Inflation and Gravitational Waves: Discovery Images]
Spergel said that, on hearing the news, he was "excited but doubtful about the results."
His initial trepidation arose from the fact that the measurements made by the BICEP2 team were only taken in a single-energy frequency. Spergel asserted that at least three frequencies are required for a solid detection.
Observations in a single band can set limits on gravitational waves, but "it's very difficult to make a convincing detection," he said.
Another issue with the reported detection stems from the fact that dust in the Milky Way galaxy can scatter microwaves, creating a similar polarization pattern as that produced by gravitational waves — an effect that can be subtracted out.
"Dust has turned out to be an even more pernicious problem than many of us thought years ago," Spergel said.
The BICEP2 team made their measurements in one of the most polarized regions of the sky, and Spergel contends that the researchers didn't sufficiently subtract out the contribution from foreground dust emission.
The team relied on the preliminary findings on cosmic dust reported in a conference talk by scientists leading Europe's CMB-mapping Planck mission, rather than on published data. (This was the best possible option, BICEP2 team members have said; full Planck data will not be released until November.)
The BICEP2 team estimated that only 3.5 to 5 percent of the dust in the sky is polarized, but a large fraction of the sky suggests that the actual polarization figure is above 7 percent, Spergel said.
"I think it is optimistic to assume the polarization is much less," he said.
'A very sensitive record'
Spergel is not the only scientist to express doubts about inflation's "smoking gun." Since its release, the BICEP2 results have come under a great deal of scrutiny from other scientists.
But whatever ends up happening, Spergel says the findings are important and will help scientists further understand gravitational waves.
"The BICEP measurement will be a very important measurement at 150 Gigahertz," Spergel said, referring to the frequency of the 512 detectors responsible for capturing the data.
The finding also illuminates an important lesson — the need to validate a result at several different frequencies, which would provide more robust evidence for detections from the early universe.
"We are entering a very exciting period of time for cosmologists hoping to detect gravity waves," Spergel said. "I think the BICEP team should be recognized for having made a very sensitive record, for pushing the field forward." | 0.840824 | 4.112509 |
Cinder cones constitute one of the most common volcanic features on earth (Basaltic Volcanism Study Project, 1981), as well as one of the least studied. The breaching of cinder cones, due to the eruption of an associated lava flow, has been noted by a number of geologists, but has received little attention. Breaching is defined as the removal of material from the cone due to erosional, gravitational, or volcanic mechanisms, such that the interior of the cone is exposed. The Dictionary of Geological Terms (1976) defines a breached cone as a cinder cone in which lava has broken through the sides and carried away the broken material. The "broken material" is either pushed away by the flow or rafted on the surface of the flow.
Detailed examination of breaching events and rafted material of cinder cones is, in general, lacking. This investigation will examine the rafted material and cone structure and morphology at Strawberry Crater and O'Neill Crater to determine the sequence of events in the breaching of these cinder cones.
Strawberry and O'Neill Craters are located in the eastern section of the San Francisco volcanic field (SFVF), at the southern edge of the Colorado Plateau physiographic province, north-central Arizona. (Figure 1). The SFVF is dominantly basaltic in composition with local centers of silicic rocks. The basaltic rocks show a strong alkaline affinity (Eastwood, 1974; Moore et al., 1974) and are distributed throughout the volcanic field as flows and pyroclastic deposits. A total of 568 basalt, basaltic andesite and benmoreite scoria vents have been identified (Table 1, Ulrich, unpub. data).Thirty-six of these vents have been identified as being breached due to lava extrusion during the eruption.
Volcanism in the SFVF has been active since the late Miocene. Extensive K-Ar dating of the volcanics has shown a regular pattern for the migration of vent location from the southwest to the east at a rate of 1.2 cm/yr (Tanaka et al., 1986). The location of the volcanic centers and individual cone morphology within the SFVF are strongly controlled by the NW-SE, NE-SW, and N-S fault systems of the southern Colorado Plateau (Figure 2; Shoemaker et al., 1974; Breed, 1964). The current stress regime for the SFVF is extensional and is attributed to current Basin and Range deformation (Luchitta, 1974; Zoback and Zoback, 1980) with a least principal horizontal stress direction at approximately N50E (Brumbaugh, per. comm.).
The SFVF rests upon the Permian Kaibab Formation and the Triassic Moenkopi Formation. The Kaibab Formation is a dolomitic limestone, deposited in a near shore to open marine environment (Cheevers and Rawson, 1979), generally showing a blocky, jointed, cliff/ledge forming morphology. The Moenkopi Formation is a distinctly colored red mudstone/sandstone, deposited in a fluvial system (Stewart et al., 1972), showing a ledge/slope forming morphology. Neither formation directly contacts the volcanics at Strawberry Crater or O'Neill Crater. However, the close proximity of the Kaibab Formation outcrops to O'Neill Crater suggests that the strata may directly underlie much of this complex.
Colton (1937, 1967) appears to be the first to have described the geologic features of Strawberry and O'Neill Craters. Strawberry Crater is described as a breached cinder cone which was initially breached on the south side, followed by a major breach on the east side. Colton described the associated flow as being "fractured into blocks" and comparable to S P Crater's associated flow. He classified it as the earliest known Stage IV flow. The description for O'Neill Crater is even shorter, stating that it is a breached cone with an associated "broken fragments" flow that is classified as Stage III. This flow is also described as being similar to the S P flow.
Colton's (1937) Stage I-Stage V classification of cinder cones and Cooley's (1962) addition to this system of the Black Point-Sunset Age classification, later modified by Moore (1974) (Table 2), is based on geomorphic examinations of the volcanic field, and thus provide only relative ages. Damon and other's (1965, 1974) K-Ar dating of volcanic flows gave absolute dates for both Strawberry and O'Neill Craters. Strawberry Crater is dated at 46,000±46,000 yrs. and O'Neill Crater is dated at 50,000±14,000 yrs. (these dates are uncorrected for recently revised decay constants, Ulrich et al., 1984). Moore and Wolfe (1987) give dates of 51,000±46,000 yrs. and 55,000±14,000 yrs., respectively.
A study of the northern and eastern parts of the SFVF by Moore and Wolfe (1974, 1976) yielded a 1:362,000 scale map, petrologic data, and SiO2 content of basaltic andesite flows associated with Merriam age cinder cones. These were described as containing phenocrysts of corroded plagioclase, olivine, clino- and orthopyroxene and some occasional gabbroic, granulitic and sedimentary xenoliths. Both Strawberry and O'Neill Craters are mentioned as having small central plugs of rhyodacite vitrophyre. Silica content is given for O'Neill Crater only: cinder and spatter - 54.5%, associated flow - 59%, rhyodacite plug - 67%. This information was updated by Moore and Wolfe (1987) with whole rock chemical analyses (Table 3) and CIPW normative data, as well as detailed descriptions of the lithologies of cones, flows and plugs.
Bloomfield's (1988, written communication) petrologic and chemical analyses of Strawberry Crater (Table 3) indicate that the volcanics range in composition from basalt and basaltic andesite to mugearites, benmoreites and trachytes, using the classification of LeBas and others (1986). The wide range in compositions, with SiO2 varying from 49 to 64 weight percent, are accounted for through a magma mixing model. Mantle derived basaltic magma is suggested to have caused crustal melting, which was followed by subsequent mixing of the rhyolitic magma with a mantle derived or a differentiated basaltic magma.
Moore and Wolfe (1976, 1987) and Ulrich and others (1984) show each crater on U.S. Geological Survey maps, scale 1:50,000 and 1:250,000 respectively. Wood's (1980) study of cinder cone degradation uses Strawberry Crater in a crater width vs. cone width graph. Lastly, the two craters have been mentioned in works by Green and Short (1974), Wolfe (1984), and Tanaka and others (1986).
Despite the sparseness of detailed work on Strawberry and O'Neill Craters there has been a fair amount of general work done on the cinder cones of the SFVF. General studies of cinder cones include, most notably, Colton's (1937) work on relative dating of craters and flows based on geomorphic features and superposition. The earliest works concerning the volcanic field are Robinson (1913) and some remarks in pre-1900 surveys (see Robinson, 1913). However, these were more concerned with the San Francisco Peaks and only mention cinder cones as relatively minor features, if they are mentioned at all. More recent studies have primarily dealt with morphometric measurements (Babbitt, 1964; Breed, 1964; Colton, 1964), while others have dealt with volcanic processes and emplacement of cinder cone fields (Stoeser, 1974; McDonald, 1975; Settle, 1979; Lynch, 1982).The specific studies of individual cinder cones in the SFVF has been limited to S P and Sunset Craters (Colton, 1937; Smiley, 1958; Hodges, 1960; Amos, 1981, 1986; Holm, 1987; and Ulrich, 1987).
Discussion regarding the breaching of cinder cones due to volcanic events is primarily limited to statements indicating whether a cone is breached or that breaching occurred at a specific time during a witnessed eruption (Foshag and Gonzalaz, 1956; Porter, 1972; Williams and Moore, 1973; and Hammill, 1979). The Foshag and Gonzalaz (1956) account of the eruption of Paricutin, Mexico, gives descriptions of breach events. In all cases, however, the accounts lack details concerning the cause of the breach or detailed maps showing positions of the removed material. Three notable works are Macdonald (1972), Gutmann (1979) and Holm (1987). All three works indicate that the breached portion of a cinder cone is represented by rafted mounds of agglutinate and cinders on top of the associated lava flow. Holm's (1987) work specifically states that the presence of rafted agglutinate and cinder mounds can be used to indicate a past breaching event, even if the cone is subsequently rebuilt and appears unbreached. Scott and Trask (1971) observed that the breaching of the cinder cones in the Lunar Crater volcanic field, Nevada, show a preferred direction, parallel to the trends of the local fault system.
Several mechanisms for cinder cone breaching by the associated lava flow have been proposed. Macdonald (1972) states that breaching can occur due to burrowing of the flow through the cone or melting of the cone wall by the flow. Gutmann (1979) suggests that the outward directed pressure of the upwelling magma is sufficient to cause catastrophic failure of the cone structure, and results in a breach. | 0.816727 | 3.251545 |
The sky will provide a socially distant entertainment activity for stargazers this week: the annual Eta Aquarid Meteor Shower.
The May meteor shower is bits of ice and space dust left behind from Halley’s Comet that crash into Earth’s atmosphere, creating what we see as shooting stars. The annual shower serves as a reminder of the famed fireball only visible from Earth every 75 years or so. Its last sighting was in 1986, putting its next expected sighting in 2061.
This year’s meteor shower is expected to peak between Monday and Wednesday night, and is best viewed from the Southern Hemisphere, where the night is longer at this time of year.
But Northern Hemisphere viewers will have a chance to see the shower between 3 a.m. and dawn, International Meteor Organization Secretary General Robert Lunsford tells NPR.
“You can see them from anywhere as long as the sky is clear,” Lunsford said. But the shower won’t be as good this year as it was last May, he says, because the moon will be full on Thursday, reducing the visibility of meteors.
Viewers should look due east to see the shooting stars, which will be coming up from the horizon and moving quickly across the night sky from their origin in the constellation Aquarius.
Observers in the Northern Hemisphere can expect to see between five and 10 meteors per hour, depending on weather conditions.The more dry and clear the night, the better chance of seeing the shower. In Australia, stargazers reported up to 37 meteors per hour in good conditions.
The key to a successful shower experience, says Lunsford, is to get comfortable.
“Don’t step outside and stand there and expect to see meteor activity,” he says. Instead, he suggests grabbing a lawn chair and a warm blanket and setting up camp in the darkest area possible. “If you’re comfortable, you’re gonna see a lot more activity.”
And if being awake at 4 a.m. is not feasible, more vibrant showers including the Perseids and the Geminids will come later this year with better sky conditions in August and December.
NASA astronauts describe 'smooth' ISS docking after SpaceX launch – The Globe and Mail
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Astronauts describe ride to space aboard SpaceX Crew Dragon – CBS News
Thethat boosted astronauts Douglas Hurley and Robert Behnken into space provided a slightly rougher ride than expected during the later stages of the climb to orbit, but both said Monday they enjoyed their historic trip and marveled at a sooth-as-silk .
And yes, the Crew Dragon brought a “new car smell” to the lab complex.
“It absolutely did,” said station commander Chris Cassidy, the lone American aboard the station until Hurley and Behnken arrived Sunday. “Then when we got that hatch open, you could tell it was a brand new vehicle, with smiley faces on the other side, smiley face on mine, just as if you had bought a new car, the same kind of reaction.
“Wonderful to see my friends, and wonderful to see a brand new vehicle,” he said.
from pad 39A at the Kennedy Space Center Saturday afternoon, strapped into a Crew Dragon capsule atop a Falcon 9 rocket.
It was the first piloted launch to orbit from U.S. soil in nearly nine years, the first flight of a SpaceX rocket carrying astronauts and the first new crewed spacecraft to fly in space since the first shuttle mission 39 years ago.
Both Hurley and Behnken are space shuttle veterans, familiar with the initially rough ride when the orbiter’s powerful solid-propellant boosters were firing and the transition to a much smoother experience after the boosters were jettisoned and only the ship’s liquid fueled main engines were running.
The Falcon 9 is a two-stage rocket powered by liquid oxygen and kerosene. The first stage, featuring nine Merlin engines, generates 1.7 million pounds of thrust at liftoff. The rocket’s second stage is powered by a single vacuum-rated Merlin engine.
“Shuttle had solid rocket boosters, those burned very rough for the first two-and-a-half minutes,” Hurley said. “The first stage with Falcon 9 … was a much smoother ride.”
He said the shutdown of the first stage engines, the separation of the first and second stages and then the ignition of the upper stage’s single engine was similar to the memorable launch sequence depicted in the movie “Apollo 13.”
“So the first stage engines shut off, and then it took some time between the booster separating and then the Merlin vacuum engine starting,” Hurley said. “At that point, we go from roughly three Gs (three times the normal force of gravity on the ground) to zero Gs for, I don’t know, a half a second probably, and then when that Merlin vacuum engine fires, then we start accelerating again.
“It got a little rougher with the Merlin vacuum engine, and it’ll be interesting to talk to the SpaceX folks to find out why it was a little bit rougher ride on second stage than it was for shuttle on those three main engines.”
The Crew Dragon is designed to rendezvous and dock with the space station autonomously, without any direct input from the crew. But for the first piloted test fight, Hurley took over manual control twice to verify astronauts can fly the ship on their own if necessary.
There were no problems and when the Crew Dragon docked with the station Sunday morning, Hurley and Behnken were unable to detect the impact.
“The thing that really stood out to both of us, and we mentioned it as soon as we docked, is we didn’t feel the docking,” Hurley said. “It was just so smooth.”
Hurley is a former test pilot and Behnken, who holds a doctorate in mechanical engineering from Caltech, is a veteran Air Force flight test engineer. They were selected for the first piloted Crew Dragon flight in part so they could bring those skills to evaluating the spacecraft before it begins operational missions to the space station in the late-summer timeframe.
“We’re there to evaluate how it does the mission and so far, it’s done just absolutely spectacularly,” Hurley said. “It’s a very clean vehicle. … It does everything we need it to do for this mission, so we’re very happy with that part of it.”
Including the operation of the Crew Dragon’s toilet. While he did not provide any details, Hurley said it is “very similar to the one we were used to in the space shuttle, and it worked very well. We had no issues with it.”
NASA managers have not yet decided how long Hurley and Behnken will remain in orbit. The Crew Dragon is certified for up to four months in space, but the crew could be ordered home earlier depending on how the space environment affects the capsule’s solar arrays, the weather in the Atlantic Ocean splashdown zone and other factors.
Not knowing when they might be coming home is “a little bit strange,” Behnken said. “I’m trying to explain it to my son, just six years old, and from his perspective, he’s just excited that we’re going to get a dog when I get home. And so he’s accepting that uncertainty and continuing to send messages to me while I’m on orbit.”
The mission is expected to last at least six weeks and possibly up to four months, far longer than their relatively brief shuttle flights. Staying in touch with their wives, both veteran astronauts, and their two sons is a top priority for both Hurley and Behnken.
“One of the things I was most excited about (after launch) was being able to make a phone call home,” Behnken said. “It’s been a long time since I launched into orbit, and I’ve got a little boy who got a chance to watch me do that for the first time in his life. And I just wanted to understand what his experience was and share that a little bit with him.
“He was able to make the trip back to Houston after watching the docking from down in Florida and was pretty excited about the whole thing. So that was wonderful for me.”
Elon Musk announces Twitter break, but it’s a mystery as to why – Digital Trends
Elon Musk surprised his 35 million Twitter followers on Monday night when he announced he was taking a break from the platform.
The message was short and sweet, and offered no explanation as to why he’d decided to step back from the microblogging site, or when he might be back.
Off Twitter for a while
— Elon Musk (@elonmusk) June 2, 2020
The timing may be seen as interesting by some. The SpaceX and Tesla CEO has, after all, courted controversy in the past with some of his Twitter posts. So it’s possible he’s taken advice — or decided for himself — to steer clear of the site during a particularly turbulent time as protests and social unrest continue in multiple states following the police-custody death of George Floyd in Minneapolis last week.
But Musk isn’t one to shy away from controversy, so other factors could also be at play. The billionaire entrepreneur may simply want some time off following an intense period of activity in recent weeks that included a dispute with the authorities over the reopening of his Tesla manufacturing plant in California following coronavirus-related stay-at-home orders, and also a critical SpaceX mission involving the first-ever astronaut launch using the Crew Dragon spacecraft.
He also recently become a father again, and so may want to spend more time with his new son without thinking about his next Twitter post.
Musk’s penultimate post was a retweet 10 hours earlier of a NASA tweet linked to the recent Crew Dragon trip to the International Space Station.
Besides Monday’s post, his last personal tweet came on May 31 to announce that the Crew Dragon had successfully docked with the space station.
The response to Musk’s five-word tweet was mixed, with some wishing him a nice break, and others saying in no uncertain terms how happy they were about his decision.
We will miss you.
— JT Lewis (@thejtlewis) June 2, 2020
— Frei Cuing (@SecretQMafia) June 2, 2020
Take care. U deserve a break
— Viv (@flcnhvy) June 2, 2020
no one cares, dude
— Toonimated (@Toonimated) June 2, 2020
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Mars may one day have rings similar to Saturn’s famous halo, new research suggests.
In a few tens of millions of years, the Red Planet may completely crush its innermost moon, Phobos, and form a ring of rocky debris, according to the new work. Phobos is moving closer to Mars every year, meaning the planet’s gravitational pull on the satellite is increasing. Some scientists have theorized that Phobos will eventually collide with Mars, but the new research suggests that the small moon may not last that long.
“The main factor affecting whether Phobos will crash into Mars or break apart is its strength,” Tushar Mittal, a graduate student at the University of California, Berkeley and one of the authors of the new research paper, told Space.com by email. “If Phobos is too weak to withstand increasing tidal stresses, then we expect it to break apart.” [Photos of Mars’ Moon Phobos Up Close]
Strength of a satellite
The two moons of Mars, Phobos and Deimos, are named after the children of the god Ares, the Greek counterpart to Mars, the Roman god of war.
The larger, inner moon, Phobos, is only about 14 miles (22 kilometers) wide, and orbits the Red Planet rapidly, rising and setting twice each Martian day. The tiny moon is slowly moving toward its host — drawing closer to Mars by 6.5 feet (2 meters) every century — which may result in a dramatic crash into the Martian surface within 30 million to 50 million years, previous research has shown.
But after simulating the physical stresses that Mars exerts on Phobos, Mittal and co-author Benjamin Black, a postdoctoral researcher at UC Berkeley, see a different fate for Phobos. Their research suggests that instead of going out in a single, enormous impact, the moon will be pulled apart by the Martian gravity.
On Earth, the gravitational pull of the moon causes the rise and fall of ocean tides. Although the moon has no oceans, Earth’s gravitational pull is still referred to as “tidal forces.”
Phobos and other moons in the solar system also feel tidal stress from their hosts. Black and Mittal studied the “strength” of the Martian satellite, including characteristics like composition and density, to determine how much planetary stress the moon could withstand.
After comparing it to several meteorites on Earth, they concluded that Phobos today is made up of porous, heavily damaged rock and is likely the same throughout its interior.
“The moon is probably neither a complete rubble pile, nor completely rigid,” Mittal said. “The porosity of Phobos may have helped it survive.”
After simulating the stresses caused by the tidal pull of Mars, the pair found that the moon would break up over the course of 20 million to 40 million years, forming a ring of debris around the planet.
The rubble would continue to move inward, toward the planet, though at a slower pace than the larger moon is traveling, they said. Over the span of 1 million to 100 million years, the particles would rain down on the equatorial region of Mars, Mittal and Black said.
Initially, the ring could be as dense as Saturn’s, but it would become thinner as the particles fell down onto the planet over time, they added. [Latest Images from the Mars Reconnaissance Orbiter]
An inward-moving planet
Saturn isn’t the only planet in the solar system to boast rings; all of the gas giant planets have some form of debris disk surrounding them. While some of the material was likely gathered from space, portions of those ring systems could be the remains of early moons that broke apart as they journeyed inward. Larger moons move inward at a fasterpace than their smaller counterparts, causing a much more rapid demise.
“Phobos is unique in that it is currently one of only a couple of inwardly evolving moons in our solar system that we know about,” Mittal said. “However, since inwardly evolving moons inadvertently self-destruct, it is possible that more inwardly migrating moons may have existed in the past.”
Phobos is the only remaining inwardly migrating moon known to exist today. The tiny, doomed moon may help scientists to better understandthe evolution of the early solar system and the fate of other moons already destroyed.
What would a ring on Mars look like?
For an observer standing the surface of Mars, the ring will look different depending on her location.
“From one angle, the ring will reflect extra light towards a viewer, and it will look like a bright curve in the sky,” Mittal said. “From another angle, the viewer might be in the ring’s shadow, and the ring would be a dark curve in the sky.”
Because Phobos is made up of dark material that doesn’t reflect light well, the ring might be difficult to spot from Earth with an amateur telescope. However, Mittal suggested that the ring’s shadow on Mars could be visible.
Confined to a single, stable disk, the ring — if it forms — shouldn’t create too many problems for the exploration of, or travel to, the Red Planet, Mittal said. However, “Any deorbiting ring particles could be a potential hazard for a Mars base built near the equator,” he added.
The research was published online today (Nov. 23) in the journal Nature Geoscience.
source: livescience.com by Nola Taylor Redd | 0.854825 | 3.742689 |
Take a Closer Look: The innermost region of protoplanetary discs and its connection to the origin of planets
ESO-HQ, Garching b. München, Germany
October 15-19, 2018
The quest for detecting exoplanets (e.g., via Kepler and HARPS RV surveys) has revealed the existence of a large population of systems comprising one to several planets very close to the central star, i.e. at distances of 0.1-1 au, even around TTauri (age<5 Myr) stars. These are usually slightly bigger than the Earth and up to Neptune sizes, with rare Jupiter analogues. This finding differs to what we observe in our own Solar System, and raises the question of how such planets form. From a theoretical point of view, it is still hard to show that these planets formed in-situ, but it is similarly complicated to explain this large population of close-in planets as a result of migration through the disk. Additional evidence of the importance of this region comes from our own Solar System, where studies have established that material routinely observed in meteorites (e.g., Ca-Al-rich inclusions, CAI) must have formed very close to the central star, or in a very hot region of the disc.
To advance our understanding of planet formation and migration, it is crucial to study the conditions within the inner regions of their progenitor protoplanetary discs. The innermost part of the disc is where most of the star-disc interaction processes take place. The magnetic field topology of the central star truncates the disc at a few stellar radii and drives accretion of material onto the central star, as well as the ejection of fast-collimated jets and slow winds. Recent studies indicate that this star-disc interaction evolves quickly at the same time that giant planet formation ceases. Also, this region is known to undergo rapid evolution, for example, short or long lasting dimming events (e.g., AA-Tau, RW Aur, dippers). This rapid evolution is, in itself, likely to impact the formation of planets. Finally, a fraction of discs known as transition discs, show a deficit of dust in the inner few au of the disc, which could be related to the mechanism driving disc evolution in this planet-forming region.
Studies of this key inner disc region require innovative techniques and a wide range of instrumentations, since radio interferometers cannot resolve spatial scales smaller than ~10 au in most discs. Observations with instruments on the ESO/VLT and VLTI and other facilities provide us with unprecedented detail and motivate this workshop. Specifically, this workshop aims at discussing the present-day knowledge of the morphology and composition of the innermost regions of the disc, of the star-disc interaction processes, and of the theories to describe the evolution of the innermost regions of discs and of the formation of close-in planets. The workshop will thus cover the following themes:
- observations of the innermost regions of discs (<0.1-1 au, with near-IR interferometry, adaptive optics, spectroscopic techniques, space-based diffraction limited telescopes such as HST and JWST in the future)
- modeling of the inner disc (structure of the inner gas disc, disc walls, effects of magnetic fields)
- observations and theoretical predictions of processes happening at the inner disc-star interface (e.g., magnetic fields, accretion, jets)
- observations of exo-planets close to the central star (hot Jupiters, transits...)
- theoretical predictions to explain the origin of planets detected close to the stars | 0.837152 | 3.962232 |
This image of distant interacting galaxies, known collectively as Arp 142, bears an uncanny resemblance to a penguin guarding an egg. Data from NASA's Spitzer and Hubble space telescopes have been combined to show these dramatic galaxies in light that spans the visible and infrared parts of the spectrum.
This dramatic pairing shows two galaxies that couldn't look more different as their mutual gravitational attraction slowly drags them closer together.
The "penguin" part of the pair, NGC 2936, was probably once a relatively normal-looking spiral galaxy, flattened like a pancake with smoothly symmetric spiral arms. Rich with newly-formed hot stars, seen in visible light from Hubble as bluish filaments, its shape has now been twisted and distorted as it responds to the gravitational tugs of its neighbor. Strands of gas mixed with dust stand out as red filaments detected at longer wavelengths of infrared light seen by Spitzer.
The "egg" of the pair, NGC 2937, by contrast, is nearly featureless. The distinctly different greenish glow of starlight tells the story of a population of much older stars. The absence of glowing red dust features informs us that it has long since lost its reservoir of gas and dust from which new stars can form. While this galaxy is certainly reacting to the presence of its neighbor, its smooth distribution of stars obscures any obvious distortions of its shape.
Eventually these two galaxies will merge to form a single object, with their two populations of stars, gas and dust intermingling. This kind of merger was likely a significant step in the history of most large galaxies we see around us in the nearby universe, including our own Milky Way.
At a distance of about 23 million light-years, these two galaxies are roughly 10 times farther away than our nearest major galactic neighbor, the Andromeda galaxy. The blue streak at the top of the image is an unrelated background galaxy that is farther away than Arp 142.
Combining light from across the visible and infrared spectrums helps astronomers piece together the complex story of the life cycles of galaxies. While this image required data from both the Spitzer and Hubble telescopes to cover this range of light, NASA's upcoming James Webb Space Telescope will be able to see all of these wavelengths of light, and with dramatically better clarity.
The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.
NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena, California. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. | 0.882288 | 4.059855 |
Ever since the year 1610, when Galileo Galilei focused his telescope on Saturn, the rings of the sixth planet of the solar system have been a mystery that has been revealed by advances in science and technology. In the nineteenth century, Maxwell predicted with mathematical formulas what those intriguing rings were made of and a century later the Voyager space probes confirmed that prediction. Now the Cassini craft is revealing even more details, with a final dive between Saturn and its rings in September 2017 that will culminate its mission.
In July 1610, Galileo Galilei aimed his homemade telescope at Saturn. It was the second planet of the starry night that caught his attention, after Jupiter, and to his surprise this wandering star showed a pair of “handles or arms.” Due to the rudimentary nature of his telescope, Galileo was not able to see clearly what was around Saturn. The appearance of this planet then became a puzzle to be solved by future astronomers.
In 1655, the Dutch scientist Christiaan Huygens found that those “handles” of Saturn were a ring. He did so thanks to a telescope of barely five centimetres in diameter and three metres in length that allowed him to increase the size of celestial objects 50 times. Thus he saw that Saturn was surrounded by a ring system.
Seeing even further was the Italian astronomer Giovanni Domenico Cassini, who discovered in 1675 that among the rings of Saturn there is a space that separates them into two well-differentiated zones, one more internal and another more external. Today that space, almost empty and about 5,000 km wide, is called the Cassini Division.
Maxwell predicts the composition of the rings
The descriptions of Saturn’s rings would continue from the seventeenth century onwards, but no one questioned their composition until the mid-nineteenth century. It was the British mathematician James Clerk Maxwell who endeavoured to prove that Saturn’s rings could not consist of a single continuous element. He proved mathematically that the force of gravity would break a thin body orbiting Saturn, so he predicted that the rings were composed of a large numbers of particles that floated around the planet. Only by looking at them from as far away as Earth did they appear to be solid rings.
We now know that his prediction was correct because of the images sent by the twin Voyager 1 and 2 spacecraft in the early 1980s. The photographs that confirmed he was right were sent from Saturn to Earth thanks to Maxwell’s most important discovery: electromagnetic waves.
Four spacecraft have visited Saturn
On September 1, 1979, a NASA spacecraft, Pioneer 11, flew past Saturn and took the first photos of the planet at close range. Its images corroborated what we could see from Earth. Saturn’s ring system has four well-differentiated zones, rings A, B, C and D, with the large Cassini Division between A and B.
In addition, these photographs allowed the discovery of weaker areas, difficult to see at a great distance, located in the outermost part, the rings E, F and G. After its passage past the gas planet, Pioneer 11 continued its route towards the exterior of the Solar system.
At the end of 1980 came the Voyager 1 probe, and in the middle of 1981 its twin, Voyager 2. This time we learned about the composition of the rings (they consist of countless particles of ice) and new structures of the ring system, as well as data about the atmosphere of Saturn and its larges
t satellite, Titan (Saturn has more than 60 moons.)
After that visit, it would be 23 years before another spacecraft approached Saturn. NASA, ESA (the European Space Agency) and ASI (the Italian Space Agency) decided to undertake the project of installing a spacecraft in orbit around Saturn through the Cassini-Huygens mission. The Cassini spacecraft would orbit Saturn and the Huygens spacecraft would separate from Cassini to reach Titan’s surface. On October 15, 1997, Cassini-Huygens took off from Cape Canaveral and, after seven years traveling billions of kilometres, entered Saturn’s orbit on July 1, 2004.
The rings are the remains of a moon covered with ice
Until 2015, theories about how Saturn’s rings were generated were not able to explain why the composition of the tiny particles that make it up is more than 90% ice. It was then that planetary scientist Robin Canup, a researcher at the University of Colorado, published his theory in the prestigious scientific journal Nature. In order to develop his hypothesis, Canup made detailed computer simulations with the goal of explaining the frozen composition of the particles, ranging from the size of hailstones to other even smaller pieces.
His theory states that during the birth of the solar system, 4.6 billion years ago, a satellite of Saturn sank into the planet. Saturn’s ring system is the remains of that gigantic ice moon with a rocky core that struck the planet. The enormous fragments that were ejected in the collision formed a system of rings very different from the one that we can observe today. But over billions of years, the numerous collisions between these large pieces gave rise to the large ring of small particles that can be observed today.
Cassini, 13 years orbiting Saturn
Since July 2004, the Cassini spacecraft has been orbiting Saturn and sending back information about the planet and its rings. It has also been the first probe to search for the presence of life on its moons Titan and Enceladus. For thirteen years it has helped us to better understand the second largest planet in the solar system, and probably the most extraordinary (no offence to the Earth).
On April 26, Cassini became the first spacecraft to enter the space between Saturn and its rings, fulfilling its last mission before its planned destruction on September 15, 2017. It will be the first time in which an analysis will be made of the ice particles from the main rings and the outermost layers of this planet’s atmosphere. On September 11 it will make its last flyby, which will serve to steer Cassini towards its break up in Saturn’s atmosphere four days later. It will have taken more than 400 years of scientific research and technological development to unveil all the mysteries of Saturn’s rings. | 0.849307 | 3.941457 |
From stellar spectra we learn the history of the stars themselves, about the planets orbiting around them, about the galaxy in which they were born, and even the nature of the hot, dense bubble out of which all matter was created almost fourteen billion years ago. With homogenous mapping of the chemical compositions, ages, positions, and kinematics of millions of stars, our understanding of both stars and galaxies will be revolutionised in the coming years. This science is called Galactic archaeology and is made possible because the stars carry information about their past in their present-day chemistry and dynamical properties.
Because today’s Milky Way is made of many populations with overlapping characteristics, the most promising way to disentangle the formation path of each of the Galactic components and their interrelationships is by obtaining large samples of stars in the bulge, halo, thick and thin disk, with both detailed chemical abundances and kinematic information. The collected data will address some of the biggest questions in contemporary astronomy and cosmology. Our research group is involved in several ongoing and future large stellar surveys with this goal in mind.
However, stellar abundances must be determined with the help of theoretical models of the light-emitting atmospheres. We also develop advanced 3D, non-equilibrium models of stellar spectra, challenging traditional analysis and the strongly simplifying approximations to the actual physical states of stellar atmospheres that are usually made.
In these pages you will find a description of our ongoing projects and recent publications. Our independent research group is sponsored by the Sofja Kovalevskaja Award of the Alexander von Humboldt Foundation, by the Swedish Research Council and the European Commission. This fixed-term research project is scheduled to end 31 December 2019.
The core group consisted of (parentheses indicate post-MPIA affiliations):
- Group leader Karin Lind (→ Stockholm University)
- PhD student Sven Buder (→ Australian National University)
- PhD student Xudong Gao (at MPIA)
- Postdoc Anish Amarsi (→ Uppsala University)
- Postdoc Diane Feuillet (→ Lund University)
- Postdoc Ása Skúladóttir (→ Florence University)
In addition, the group was host to a number of short-term (~1-year) visiting researchers:
- PhD student Henrique Reggiani (→ Johns Hopkins University)
- PhD Student Theodora Xylakis-Dornbusch (→ Landesternwarte, University of Heidelberg)
- Postdoc Yeisson Osorio (→ IAC, Tenerife) | 0.81012 | 3.596201 |
First photo of a black hole: Astronomers capture image of cosmic phenomenon
Scientists have released the first image of a black hole. The terrifying star-devouring monster is being compared to the Eye of Sauron.
Astronomers on Wednesday unveiled the first photo of a black hole, one of the star-devouring monsters scattered throughout the Universe and obscured by impenetrable shields of gravity.
The image of a dark core encircled by a flame-orange halo of white-hot plasma looks like any number of artists’ renderings over the last 30 years.
But this time, it’s the real deal.
“The history of science will be divided into the time before the image, and the time after the image,” said Michael Kramer, director at the Max Planck Institute for Radio Astronomy.
Carlos Moedas, European Commissioner for Research, Science and Innovation called the feat a “huge breakthrough for humanity.”
The supermassive black hole immortalised by a far-flung network of radio telescopes is 50 million light-years away at the centre of a galaxy known as M87.
“It’s a distance that we could have barely imagined,” Frederic Gueth, an astronomer at France’s National Centre for Scientific Research (CNRS) and co-author of studies detailing the findings, told AFP.
HOW TO UNDERSTAND THE IMAGE
Australian-born science communicator Derek Muller explained on his YouTube channel Veritasium, there is more to the object than first meets the eye.
The blackness of a black hole is due to its event horizon, the point at which gravity is so strong even light cannot escape.
If the black hole had nothing around it, the image of the object would not have been possible.
But because the black hole has dust and gas swirling around it in an accretion disk, the object can be seen. And that’s what the fiery halo is around the image.
“It’s this matter that the black hole feeds off,” Mr Muller said.
So what’s the black “shadow” in the middle. Is it the event horizon? Yes, but also more.
Mr Muller said black holes warp space and time around them, which changes the path of light rays as they follow curved space.
Light rays that approach the black hole get bent and if they’re too close, they are sucked into the object.
For a parallel light ray not be drawn into the object it must be 2.6x further away than the size of the hole. Any light travelling closer than that cannot be seen.
The resulting shadow is 2.6x bigger than the event horizon.
A PEBBLE ON THE MOON
Locking down an image of M87’s supermassive black hole at such distance is comparable to photographing a pebble on the Moon, the scientists said.
It was also very much a team effort.
“Instead of constructing a giant telescope that would collapse under its own weight, we combined many observatories,” Michael Bremer, an astronomer at the Institute for Millimetric Radio Astronomy (IRAM) in Grenoble, told AFP.
The release of the image is causing a stir on social media, where it is already being compared to the Eye of Sauron, the villain from Lord of the Rings.
The first ever photograph of a black hole vs. the Eye of Sauron. Which is scarier?— Richard Elliot (@RElliotWSB) April 10, 2019
Black hole. Hands down. 😳 pic.twitter.com/RJeEAwvpl2
EARTH IN A THIMBLE
Over several days in April 2017, eight radio telescopes in Hawaii, Arizona, Spain, Mexico, Chile, and the South Pole zeroed in on Sag A* and M87.
Knitted together, they formed a virtual observatory some 12,000 kilometres across — roughly the diameter of Earth.
“The data is like an incomplete puzzle set,” said team member Monika Moscibrodzka, an astronomer at Radboud University. “We only see pieces of the real true image, and then we have to fill in the gaps of the missing pieces.” In the end, M87 was more photogenic. Like a fidgety child, Sag A* was too “active” to capture a clear picture, the scientists said.
“What we see in the image is the shadow of the black hole’s rim — known as the event horizon, or the point of no return — set against the luminous accretion disk,” Gueth told AFP.
The unprecedented image — so often imagined in science and science fiction --- has been analysed in six studies co-authored by 200 experts from 60-odd institutions and published Wednesday in Astrophysical Journal Letters.
“I never thought that I would see a real one in my lifetime,” said CNRS astrophysicist Jean-Pierre Luminet, author in 1979 of the first digital simulation of a black hole.
Coined in the mid-60s by US physicist John Archibald Wheeler, the term “black hole” refers to a point in space where matter is so compressed as to create a gravity field from which even light cannot escape.
The more mass, the bigger the hole. At the same scale of compression, Earth would fit inside a thimble.
A successful outcome depended in part on the vagaries of weather during the April 2017 observation period.
“For everything to work, we needed to have clear visibility at every (telescope) location worldwide”, said IRAM scientist Pablo Torne, recalling collective tension, fatigue and, finally, relief.
‘HELL OF A CHRISTMAS PRESENT
Torne was at the controls of the Pico Veleta telescope in Spain’s Sierra Madre mountains.
After that, is was eight months of nailbiting while scientists at MIT Haystack Observatory in Massachusetts and the Max Planck Institute for Radio Astronomy in Bonn crunched the data.
The Universe is filled with electromagnetic “noise”, and there was no guarantee M87’s faint signals could be extracted from a mountain of data so voluminous it could not be delivered via the internet.
There was at least one glitch.
“We were desperately waiting for the data from the South Pole Telescope, which — due to extreme weather conditions during the southern hemisphere winter — didn’t arrive until six months later,” recalled Helger Rottmann from the Max Planck Institute.
It arrived, to be precise, on December 23, 2017.
“When, a few hours later, we saw that everything was there, it was one hell of a Christmas present,” Rottmann said.
It would take another year, however, to piece together the data into an image. “To be absolutely sure, we did the work four times with four different teams,” said Gueth.
Team scientists presenting the findings at a news conference in Brussels were visibly moved.
“We are looking at a region we have never looked at before, that we cannot really imagine being there,” said Heino Falcke, chair of the EHT Science Council.
“It feels like looking at the gates of hell, at the end of space and time — the event horizon, the point of no return.
Australia is joining the space race with the opening of a new space agency
The new space agency will focus on strengthening competencies and growing capabilities making Australia less reliant on other countries for communication. | 0.841424 | 3.450081 |
Exploring the surface of Mars can be a perilous endeavor for a robot. Consider the plight of the wheeled Mars rover Spirit: The six-wheeled, 400-pound robot has been stuck in the Martian sand since January 2010—when it was downgraded from rover to science station—and the dust collecting on its solar panels may prevent it from even being able to carry out this task. As we look back on the successes and setbacks of the six-wheeled Spirit, researchers are testing out a variety of other rover ideas that could last longer, collect more data and go places on Mars that no bot has ever been.
One such concept is the Tumbleweed Rover—a simple, wind-powered, wheel-less rover that would roll over the Martian surface just like, well, a tumbleweed. The Tumbleweed has inspired scientists for more than 10 years, but to date there is no consensus regarding how exactly the rover should be designed. Now researchers at North Carolina State University have developed a computer model they say will allow engineers to test different vehicle designs and predict how they will perform on the Martian surface. The research, funded by NASA and the North Carolina Space Grant Consortium, is described in a paper published in the Journal of Spacecraft and Rockets on June 1.
The researchers created a two-part model. The first part simulates the physical parameters of the vehicle itself—the radius, weight, elasticity (how much, for example, the rover deforms when it strikes a rock) and rotational inertia. The second part re-creates specific features of the Martian surface, like rock fields and craters, based on video imaging data collected by NASA's Viking and Mars Pathfinder missions. The surface of Mars is characterized by drastic changes in landscape, and it is crucial that engineers understand the challenges each terrain type poses.
The biggest challenge in the project, according to NC State aerospace engineer and paper co-author Alexandre Hartl, was developing a detailed wind model—an extremely important element for designing the rover, given that Tumbleweed is wind-powered. "The surface wind speeds on Mars are relatively uncharted, with limited data, so you have to make some compromises on how you model the wind flow through a rock field or crater," he says. "We know what the magnitude of the wind speed is, but we don't know how it varies and its duration." The little data that is available comes from the Viking and Mars Pathfinder missions.
This model is not the first of its kind, Hartl says, but to date it is the most detailed. "We consider a lot more dynamic phenomena," Hartl says. "We're not the first one, but I think we've used it in the most sophisticated sense." Of course, getting a Tumbleweed Rover to the surface of Mars is still, at best, years away. But NASA's Jet Propulsion Laboratory and Langley Research Center are both currently developing prototypes, and the North Carolina State model will now bolster those efforts. | 0.817599 | 3.596258 |
he US space agency Nasa has unveiled a model of a space telescope that scientists say will be able to see to the farthest reaches of the universe.
The James Webb Space Telescope (JWST) is intended to replace the ageing Hubble telescope.
It will be larger than its predecessor, sit farther from Earth and have a giant mirror to enable it to see more.
Officials said the JWST - named after a former Nasa administrator - was on course for launch in June 2013.
The full-scale model is being displayed outside the Smithsonian National Air and Space Museum in the US capital, Washington DC.
The $4.5bn (£2.27bn) telescope will take up a position some 1.5 million km (930,000 miles) from Earth.
It will measure 24m (80ft) long by 12m (40ft) high and incorporate a hexagonal mirror 6.5m (21.3ft) in diameter, almost three times the size of Hubble's.
Hubble, launched in 1990, has sent back pictures of our solar system, distant stars and planets, and remote fledgling galaxies formed not long after the Big Bang.
But scientists say the JWST will enable them to look deeper into space and even further back at the origins of the universe. "Clearly we need a much bigger telescope to go back much further in time to see the very birth of the universe," said Edward Weiler, director of Nasa's Goddard Space Flight Centre.
Martin Mohan of Northrop Grumman, the contractor building the telescope, said that the team was making excellent progress. "There's engineering to do, but invention is done, more than six years ahead of launch," he said.
When ready, the JWST will be launched by a European Ariane V rocket. It is expected to have a 10-year lifespan.Until then, the 17-year-old Hubble telescope will continue to do its work. Nasa plans to send astronauts on the space shuttle to service it in 2008.
JWST is named after James E Webb, Nasa Administrator during the Apollo lunar exploration era; he served from 1961 to 1968 It will be placed 1.5m km from Earth, at Lagrange Point 2, an area of gravitational balance that keeps it in a Sun-Earth line The telescope will be shaded from sunlight by a shield, enabling it to stay cold, increasing its sensitivity to infrared radiation Three principal instruments will gather images of the Universe in the infrared region of the spectrum
These will yield new information about how stars and galaxies first formed a few hundred million years after the Big Bang | 0.852649 | 3.009105 |
The spacecraft witnessed something extraordinary.
Over 30 years ago, NASAs Voyager 2 spacecraft flew over the hot, dense world of Uranus, getting as close as 50,600 miles to the planets cloud tops.
At the time, the data collected offered scientists an unprecedented look at the ice giant of our Solar System, revealing two new rings and 11 new moons, as well as chilling temperatures that dip below 353 degrees Fahrenheit.
However, what the scientists didnt know at the time was that Voyager 2 had also witnessed something quite extraordinary over Uranus.
A team of scientists took a new look at the data collected from Voyagers Uranus flyby and discovered that the spacecraft had actually flown right through a plasmoid. Plasmoids are a giant structure of a planets magnetic field, and they can also strip a planet of its atmosphere.
The new findings were detailed in a study published in the Geophysical Research Letters, and offer a new insight into Uranus magnetic field.
Voyager 2 launched on August 20, 1977, and began its unique journey into interstellar space. But before it did that, the spacecraft had some close encounters with the planets of the Solar System.
Voyager 2 did a flyby of planets of the Solar System before heading into interstellar space.NASA
Voyager 2 was scheduled for a rendezvous with Uranus on January 24, 1986. The spacecraft beamed down thousands of images, and a host of scientific data and measurements of the planet, its atmosphere, and magnetic environment.
Uranus is an odd planet. Its spin axis is tilted by 98 degrees, which means that it spins entirely on its side unlike any other planet in the Solar System. As a result, the axis of its magnetic field points 60 degrees away from its spin axis.
So when the planet spins, the magnetosphere or the space carved out by its magnetic field, sort of wobbles along the way like a football, according to a statement by NASA.
The scientists behind the new study wanted to investigate the planets odd magnetic field further, so they began by looking back at the data gathered by Voyager 2.
Scientists took a closer look at 34-year-old data on Uranus.NASA
As they reexamined the data with fresh eyes, and more precision than before, they found a small squiggle.
That tiny distorted line was a plasmoid. Plasmoids are a sign that a planet is being stripped of its atmosphere, as these giant bubbles of plasma are sucked from the atmosphere, and hang off the end of a planets magnetic field that is blown by the solar wind, also known as magnetotail.
The discovery marks the first time that plasmoids were discovered at Uranus. It lasted for only 60 seconds of Voyagers 45-hour-long flyby and therefore appeared as a tiny blip in the data.
The process, however, is not unique to the planet. Planets like Venus, Jupiter, Saturn, and even Earth are losing their atmosphere, as particles escape their planetary grip and float off into distant space.
This process is caused by the planets magnetic fields.
A very extreme case of atmosphere escape is Mars. Scientists believe that the now dry and desolate Red Planet may have once looked very different, and possibly even hosted some form of life. But over 4 billion years of leaking into space finally took a toll on the planet.
“Mars used to be a wet planet with a thick atmosphere,” Gina DiBraccio, a space physicist at NASA’s Goddard Space Flight Center and project scientist for the Mars Atmosphere and Volatile Evolution (MAVEN) mission, said in the statement. “It evolved over time to become the dry planet we see today.”
However, its not clear how Uranus atmospheric escape has affected the planet thus far as scientists only got a tiny glimpse at this process.
“Imagine if one spacecraft just flew through this room and tried to characterize the entire Earth,” DiBraccio said. “Obviously it’s not going to show you anything about what the Sahara or Antarctica is like.”
But the newly revealed discovery does help narrow down new questions that scientists should be asking about Uranus. | 0.862424 | 3.683501 |
Crescent ♊ Gemini
Moon phase on 5 September 2015 Saturday is Last Quarter, 22 days old Moon is in Gemini.Share this page: twitter facebook linkedin
Last Quarter is the lunar phase on . Seen from Earth, illuminated fraction of the Moon surface is 49% and getting smaller. The 22 days old Moon is in ♊ Gemini.
* The exact date and time of this Last Quarter phase is on 5 September 2015 at 09:54 UTC.
Moon rises at midnight and sets at noon. It is visible to the south in the morning.
Moon is passing about ∠14° of ♊ Gemini tropical zodiac sector.
Lunar disc appears visually 0.1% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1901" and ∠1903".
Next Full Moon is the Harvest Moon of September 2015 after 22 days on 28 September 2015 at 02:50.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 22 days old. Earth's natural satellite is moving through the last part of current synodic month. This is lunation 193 of Meeus index or 1146 from Brown series.
Length of current 193 lunation is 29 days, 15 hours and 48 minutes. It is 1 hour and 36 minutes shorter than next lunation 194 length.
Length of current synodic month is 3 hours and 4 minutes longer than the mean length of synodic month, but it is still 3 hours and 59 minutes shorter, compared to 21st century longest.
This New Moon true anomaly is ∠144.1°. At beginning of next synodic month true anomaly will be ∠169.3°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
5 days after point of perigee on 30 August 2015 at 15:24 in ♓ Pisces. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 8 days, until it get to the point of next apogee on 14 September 2015 at 11:28 in ♎ Libra.
Moon is 377 060 km (234 294 mi) away from Earth on this date. Moon moves farther next 8 days until apogee, when Earth-Moon distance will reach 406 466 km (252 566 mi).
5 days after its descending node on 31 August 2015 at 10:16 in ♈ Aries, the Moon is following the southern part of its orbit for the next 8 days, until it will cross the ecliptic from South to North in ascending node on 14 September 2015 at 04:38 in ♎ Libra.
18 days after beginning of current draconic month in ♍ Virgo, the Moon is moving from the second to the final part of it.
11 days after previous South standstill on 25 August 2015 at 03:44 in ♐ Sagittarius, when Moon has reached southern declination of ∠-18.206°. Next day the lunar orbit moves northward to face North declination of ∠18.163° in the next northern standstill on 6 September 2015 at 17:06 in ♊ Gemini.
After 7 days on 13 September 2015 at 06:41 in ♍ Virgo, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.119679 |
Why is the time of the equinox so specific? S&T's editors explain.
For those of us already seeing blushing foliage or feeling a chill in the air, it might seem as though autumn has already arrived. But astronomically speaking, fall officially comes to Earth's Northern Hemisphere at 20:44 Universal Time on Sunday, September 22, 2013. At that moment, the Sun's path crosses Earth's equator heading south, an event called the autumnal equinox.
Why do we say summer ends and fall begins at an exact moment, when the natural events happen gradually? Because the four seasons many of us use — winter, spring, summer, and fall — have beginning and ending points defined as actual key moments in the Earth's annual orbit around the Sun — or equivalently, from our point of view, the Sun's annual motion in Earth's sky.
The Sun appears farther north or south in our sky, depending on the time of year, because of what some might consider an awkward misalignment of our planet. Earth's axis is tilted about 23½° with respect to our orbit around the Sun. That means that the plane drawn by Earth's orbit, called the ecliptic, is tilted with respect to the planet's equator. And because from our perspective the Sun follows the ecliptic in its path through the sky over the course of a year, each day the Sun's highest point in the sky moves depending on the time of year. For a skywatcher at north temperate latitudes, such as in the continental United States, the effect is to make the Sun appear to creep higher in the sky each day from late December to late June, and back down again from late June to late December. An equinox comes when the Sun is halfway through each journey.
The Earth's axial tilt is why we have seasons. When the planet is on one side of its orbit, the Northern Hemisphere is tipped sunward and gets heated by more direct solar rays, making summer. Six months later, when the planet is on the opposite side, the Northern Hemisphere is tipped away from the Sun, and the slanting solar rays heat the ground less, creating winter.
This celestial arrangement makes several other noteworthy things happen on the equinox date:
- In the Southern Hemisphere, September's equinox marks the start of spring, and the March equinox marks the start of fall.
- Day and night are almost exactly the same length; the word "equinox" comes from the Latin for "equal night." (A look in your almanac will reveal that day and night are not exactly 12 hours long at the equinox, for two reasons: First, sunrise and sunset are defined as when the Sun's top edge — not its center — crosses the horizon. Second, Earth's atmosphere distorts the Sun's apparent position slightly when the Sun is very low.
- The Sun rises due east and sets due west (as seen from every location on Earth). The fall and spring equinoxes are the only times of the year when this happens.
- If you were standing on the equator, the Sun would pass exactly overhead at midday. If you were at the North Pole, the Sun would skim around the horizon as the months-long polar night begins. Richard E. Byrd wrote eloquently in his 1938 book Alone of the Sun as it dove into the long Antarctic night as seen from Advance Base, 80°08'S, 163°57'W:
Huge and red and solemn, it rolled like a wheel along the Barrier edge for about two and a half hours, when the sunrise met the sunset at noon. For another two and a half hours it rolled along the horizon, gradually sinking past it until nothing was left but a blood-red incandescence. The whole effect was something like that witnessed during an eclipse. An unearthly twilight spread over the Barrier, lit by flames thrown up as from a vast pit, and the snow flamed with liquid color. | 0.847333 | 3.712865 |
Astronomers have identified a molecule containing the noble gas argon, the first such molecule detected in space.
One of the few things I remember from high school chemistry is that the noble gases are usually hermit atoms: with a full complement of electrons, they’re happy existing in solitude and unbonded with other elements.
So I was bewildered when I first read about new infrared observations of the Crab Nebula by Mike Barlow (University College London) and colleagues that suggest the presence of argon hydride ions (ArH+). Turns out the noble gases — elements in the rightmost column of the Periodic Table of Elements — can form molecules with other elements. That’s not news (even though it was news to me). As this press release from University College London explains, the news is that (1) this molecule is the first noble gas molecule detected in space, and (2) the argon in it is special: it’s the isotope argon-36, exactly the type expected to form in supernovae, like the one that created the Crab Nebula.
Astronomers detected knots of ionized argon in this supernova remnant about two decades ago, but until now observations have not revealed which isotope the argon was. The strongest emission from ionized argon and from the newly identified ArH+ come from the same part of the remnant.
Below, you’ll find the UCL press release. The team’s paper appears in the December 13th Science.
Noble gas molecules have been detected in space for the first time in the Crab Nebula, a supernova remnant, by astronomers at UCL.
Led by Professor Mike Barlow (UCL Department of Physics & Astronomy) the team used ESA’s Herschel Space Observatory to observe the Crab Nebula in far infrared light.
Their measurements of regions of cold gas and dust led them to the serendipitous discovery of the chemical fingerprint of argon hydride ions. The findings, published today in the journal Science, support scientists’ theories of how argon forms in nature.
The Herschel Space Observatory, an ESA space telescope which recently completed its mission, is the biggest space telescope ever to have flown. Herschel’s instruments were designed to detect far-infrared light, which has much longer wavelengths than we can see with our eyes.
“We were doing a survey of the dust in several bright supernova remnants using Herschel, one of which was the Crab Nebula. Discovering argon hydride ions here was unexpected because you don’t expect an atom like argon, a noble gas, to form molecules, and you wouldn’t expect to find them in the harsh environment of a supernova remnant,” said Barlow.
Although hot objects like stars glow brightly in visible light, colder objects like the dust in nebulae radiate mainly in the infrared, wavelengths which are blocked by Earth’s atmosphere. Although nebulae can be seen in visible light, this light comes from hot excited gases within them; the cold and dusty component is invisible at optical wavelengths.
In addition to mapping the dust by making far-infrared images of the nebula, the team used Herschel’s SPIRE instrument to make spectroscopic observations. In these, the infrared light is split up and dispersed according to its wavelength, much like a prism breaks white light down into its respective colors. When they looked at the data, the team saw some very unusual features which took some time to fully understand.
“Looking at infrared spectra is useful as it gives us the signatures of molecules, in particular their rotational signatures,” Barlow said. “Where you have, for instance, two atoms joined together, they rotate around their shared center of mass. The speed at which they can spin comes out at very specific, quantized, frequencies, which we can detect in the form of infrared light with our telescope.”
Elements can exist in several different versions, or isotopes, which have different numbers of neutrons in their atomic nuclei. The properties of isotopes are very similar to one another in most respects, but they do differ slightly in mass. Because of this mass difference, the speed of rotation depends on which isotopes are present in a molecule.
The light coming from certain regions of the Crab Nebula showed extremely strong and unexplained peaks in intensity around 618 gigahertz and 1235 GHz. Consulting databases of known properties of different molecules, the scientists found that the only possible explanation was that the emission was coming from spinning molecular ions of argon hydride. Moreover, the only isotope of argon whose hydride could rotate at that rate was argon-36.
In this case, energy from the neutron star at the heart of the nebula appears to have ionized the argon, which then joined with molecules of hydrogen to form the molecular ion ArH+.
Professor Bruce Swinyard (UCL Department of Physics & Astronomy and Rutherford Appleton Laboratory), a member of the team, added: “Our discovery was unexpected in another way -- because normally when you find a new molecule in space, its signature is weak and you have to work hard to find it. In this case it just jumped out of our spectra.”
The discovery of argon-36 in the Crab Nebula, as well as being the first detection of its kind, helps support scientists’ theories of how argon forms in nature. Calculations of what elements are churned out by a supernova predict a lot of argon-36 and no argon-40 -- exactly what the team observed in the Crab Nebula. On Earth, however, argon-40 is the dominant isotope as it is released by the radioactive decay of potassium in rocks.
This first discovery of an argon molecule in space continues a long tradition of noble gas research at UCL. Argon, along with the other noble gases, was discovered at UCL by William Ramsay at the end of the 19th century.
Reference: M. J. Barlow et al. "Detection of a Noble Gas Molecular Ion, 36ArH+, in the Crab Nebula." Science, 13 December 2013. | 0.812392 | 3.986799 |
A new survey offers new details about Jupiter-like planets, which could influence theories about how Earth formed and became habitable.
Over the past four years, an instrument attached to a telescope in the Chilean Andes—known as the Gemini Planet Imager—has set its gaze on 531 stars in search of new planets.
The team behind it has now released initial findings from the first half of the survey, which imaged six planets and three brown dwarfs orbiting 300 stars, in the Astronomical Journal.
“Over the past twenty years, astronomers have discovered all of these solar systems that are really different from our own,” says Bruce Macintosh, professor of physics at Stanford University. “The question that we want to understand ultimately is: Are there life-bearing, Earth-like planets out there? And one way to answer that is by understanding how other solar systems form.”
Unlike other planet-hunting techniques, which rely on looking for signs of a planet—like the effect of its gravity on the parent star—rather than the planet itself, the Gemini Planet Imager takes direct images, picking the faint planet out of the glare of a star a million times brighter.
“The giant planets in our own solar system live between five and 30 times Earth’s orbital distance, and for the first time we’re probing a similar region around other stars,” says lead author Eric Nielsen, a research scientist at the Kavli Institute for Particle Astrophysics and Cosmology. “It’s pretty exciting to be able to start to put together a census of the planets larger than Jupiter in the outer solar systems of some of our neighboring stars.”
Is our solar system special?
Most other techniques probe the inner parts of solar systems. But the Gemini Planet Imager specifically focuses on exoplanets that are large, young, and far away from the star they orbit.
In our solar system, the outer parts are the home of the giant planets. The Gemini Planet Imager helps the researchers better understand whether other solar systems have planets like Jupiter. However, while the Gemini Planet Imager is one of the most sensitive planet imagers, there are still objects that elude it and the planets this team can currently see are those more than twice the mass of Jupiter.
In the first half of the survey, the Gemini Planet Imager found fewer exoplanets than the researchers expected. However, the exoplanets they did see contributed to one of their strongest results: every one of the six planets orbited a large, bright star—despite the fact that planets are easier to see near faint stars.
This shows conclusively that wide-orbiting giant planets are more common around high mass stars, at least 1.5 times more massive than the sun. Meanwhile, for sun-like stars, Jupiter’s larger cousins are much rarer than the small planets discovered close to their star by missions like NASA’s Kepler.
“Given what we and other surveys have seen so far, our solar system doesn’t look like other solar systems,” Macintosh says. “We don’t have as many planets packed in as close to the sun as they do to their stars and we now have tentative evidence that another way in which we might be rare is having these kind of Jupiter-and-up planets.”
Although exact Jupiter-equivalent exoplanets are just beyond the scope of their instruments, not finding even a hint of something Jupiter-like around these 300 stars leaves open the possibility that our Jupiter is special.
The origins of giant planets
One other result from the first half of the survey is that brown dwarfs—objects larger than planets but smaller than stars—are a very distinct population from planets. This may point to a different formation mechanism for this class of objects, suggesting that brown dwarfs are more similar to failed stars than super-size planets.
Combined with other techniques, this paper pinpoints a distance from a star at which the number of giant planets goes from increasing to decreasing—at about five to 10 astronomical units (one astronomical unit is the distance from the sun to Earth).
“The region in the middle could be where you’re most likely to find planets larger than Jupiter around other stars,” Nielsen adds, “which is very interesting since this is where we see Jupiter and Saturn in our own solar system.”
All three of the main findings support the hypothesis that giant planets likely form “bottom up” by accumulation of particles around a solid core, whereas brown dwarfs likely form “top down” as a result of huge gravitational instabilities in the disk of gas and dust from which a solar system develops.
The future of Earth-hunting
The Gemini Planet Imager Exoplanet Survey (GPIES) observed its 531st, and final, new star in January 2019. The Gemini Planet Imager team is now working on making the instrument more sensitive to smaller, cooler exoplanets that orbit closer to their suns.
Meanwhile, the surveys capable of indirectly observing those exoplanets are moving their sensitivity outward. In the not-too-distant future, the two should convene at the corners of space where a solar system like our own could still be hiding. Whatever instrument is the first to be capable of directly viewing an Earth-like world, Macintosh imagines it will be, at least in part, a descendant of the Gemini Planet Imager.
“Right now, we see these planets as fuzzy, red blobs. Someday, it’s going to be a fuzzy blue blob. And that little, tiny, fuzzy, blue blob is going to be an Earth,” Macintosh says.
“Getting to Earths will take a space mission that’s probably about 20 years away. But when it flies, it’ll use a spectrograph like the one we built and deformable mirrors like what we have and software with lines of code that we’ve written.”
More immediately, the GPIES team members plan to publish additional results about the survey, including information they gathered about the atmospheres of exoplanets they saw, and finish analyzing the data obtained during the second half of the survey.
“I helped take the first GPIES planet search images four and a half years ago,” says coauthor Robert De Rosa, a research scientist at the Kavli Institute for Particle Astrophysics and Cosmology, who spent many nights observing with the Gemini Planet Imager in Chile and remotely from Stanford. “It’s bittersweet to see it draw to a close.”
The National Science Foundation, the National Aeronautics and Space Administration, the Natural Sciences and Engineering Research Council of Canada, the National Research Council of Canada, Fonds de Recherche du Québec, the Heising-Simons Foundation, Lawrence Livermore National Laboratory, and the Center for Exoplanets and Habitable Worlds funded the work.
Source: Stanford University | 0.846856 | 3.956417 |
Meteorites are pieces of rock and metal that fall to the Earth. Almost all are fragments broken from asteroids during collisions, taking between around 0.2 and 100 million years to journey from the asteroid belt to the Earth. There are also currently about 30 meteorites that come from the Moon, and a similar number from Mars. Meteorites are the only physical materials available on the Earth that allow direct study of the original dust from which the Solar System formed. Meteorites are named from their place of find or fall. Wherever possible, the name is taken from the nearest inhabited place to the actual site. In practice, the recovery of meteorites from desert regions has resulted in a name-number nomenclature that combines geographic and date information. The rules for naming newly recovered meteorites have been standardised by the Nomenclature Committee of the Meteoritical Society, and are summarised on the Society's web site (www.meteoriticalsociety.org). This section is intended to be a very general outline of the main features of meteorites and their classification.
Meteorites can be divided into two main types, according to the processes they have experienced: unmelted (unfractionated) and melted (or differentiated). The unmelted meteorites, or chondrites, are all stone, whilst the melted meteorites, cover a range of compositions from stone, through stony-iron to iron. Both unmelted and melted meteorites are further sub-divided into groups and classes; the inter-relationships between the different groups are shown in the "family tree". Classification of meteorites into groups is one way of identifying materials that might be associated in space and time, eg, through accretion in closely neighbouring regions of the solar nebula, or having suffered similar processes of heating, melting, differentiation and/or hydrothermal alteration. However, the classification scheme is incomplete, and there are many meteorites that do not fit comfortably into the framework. There is not always a clear cut distinction between types: eg, there are many iron meteorites that contain silicate inclusions related to chondritic meteorites. Clasts and inclusions within meteorites also frequently defy ready assignation to recognised meteorite groups. | 0.845192 | 3.411539 |
Oumuamua received tons of attention from astronomers once it was confirmed to be an interstellar object of unknown origins whizzing through our solar system. But just last Summer, a second interstellar object paid our solar system a visit: 2I/Borosov.
We don’t know much a bout 2I/Borosov except that it was an interstellar comet that had been discovered by an amateur astronomer. Perhaps unsurprisingly, more and more astronomers turned their telescopes toward the object when it became clear that there would only be a limited opportunity to observe it.
One of such telescopes to be used was the Atacama Large Millimeter/Sub-millimeter Array (ALMA), and with it, astronomers learned more about the comet’s composition. Of particular interest, the comet’s halo emitted more carbon monoxide than any other known comet in our solar system at a similar distance from Earth. This was later confirmed by NASA’s Hubble Space Telescope, and left many astronomers scratching their heads.
This discovery was important because it raised one of two potential questions about comets: 1) is comet chemical diversity more diverse than initially thought?; or 2) could this be our first official look at the potential chemical properties of another stellar system?
Whatever the case may be, astronomers think that in order for a comet like 2I/Borosov to port so much carbon monoxide, it would have needed to form far away from its host star. To put that into perspective using our own solar system, that means that it would have needed to form somewhere in the vicinity of the distance of Neptune from our own star.
It remains to be seen how 2I/Borosov got thrown out of its place of origin, but one thing’s certain: interstellar object discoveries are few and far in between, so astronomers will definitely want to take special advantage of opportunities just like this one to better understand the universe around us. | 0.899764 | 3.621028 |
Twenty years on, and the Hubble Space Telescope is still pushing the boundaries of astronomy. Ever since its faulty primary mirror was corrected, it has produced some of the most beautiful and iconic images in astronomy. And even though there are telescopes on the ground with better light-gathering power and resolution than Hubble, Hubble can do one thing which the others can’t, and that is stare at a piece of sky for hundreds of hours.
In 1995, it was pointed in the direction of the constellation of Ursa Major and stared at a patch of sky the size of a tennis ball one hundred metres away for ten days. The image is famous and is called the Hubble Deep Field (HDF). It images the dimmest and therefore most distant galaxies. Due to the time taken by light to travel across space, the further away we look the younger the galaxies appear to be and so we are able to investigate galaxy formation in the very early universe.
2004 saw the release of the Hubble Ultra Deep Field (HUDF), created by looking in the constellation Fornax (the furnace) for a stretch of eleven days which looked even further back in time than the HDF – to a time between 400 and 800 million year after the Big Bang.
On the 25th September 2012, NASA revealed the Hubble eXtreme Deep Field (XDF). This zoomed in on the HUDF. It took 23 days of exposure and looks back 13.2 billion years, just 0.5 billion years after the universe began. The field shows young galaxies growing, sometimes through violent collisions with each other. It is hoped this will help astronomers find a theory of galaxy formation.
However, we haven’t reached the magnification limit. The light from youngest galaxies yet to be observed is off the visible spectrum (Hubble’s vision) in the Infra-red due to the expansion of the universe stretching the light. NASA’s Infra-red James Webb Space Telescope will look even further into the XDF and see the time when the first stars and galaxies were beginning to form. | 0.852252 | 3.60685 |
Hi there! Today we go back to ‘Oumuamua, you know, this interstellar object discovered last Fall. Its visit to our Solar system was the opportunity to observe it, and here we discuss on an analysis of the variations of its luminosity. I present you The excited spin state of 1I/2017 U1 ‘Oumuamua, by Michael J.S. Belton and collaborators. This study tells us that its rotation state might be complex, and that affects the way we figure out its shape. It has recently been published in The Astrophysical Journal Letters.
I already told you about ‘Oumuamua. This is the first identified object, which has been found in our Solar System but which undoubtedly originates from another System. In other words, it was formed around another star.
The Pan-STARRS survey identified ‘Oumuamua in October 2017, and the determination of its orbit proved it to be unusually eccentric. With an eccentricity close to 1.2, its orbit is a branch of a hyperbola rather than an ellipse. This means that it comes from very far, passes by while the Sun deviates it, and leaves us for ever.
This is the highest eccentricity ever recorded in the Solar System so far. Other objects had an eccentricity larger than 1, but which could have been caused by the gravitational perturbation of a planet. Not for ‘Oumuamua.
Its full name is actually 1I/2017 U1 (ʻOumuamua). 2017 because it was discovered in 2017, 1I as the first Interstellar object ever discovered (by the way, the International Astronomical Union has created this category for ‘Oumuamua), and the name ‘Oumuamua means scout in Hawaiian.
The announcement of its discovery motivated the observers all around the world to try to observe it and make photometric measurements. Here we discuss what these measurements tell us on the rotation and the shape. But before that, let me tell you something on the rotation.
Different modes of rotation
We will consider that our object is an ellipsoid. This is actually unsure, but let us assume it. We have 3 different axes, and we could imagine different configurations for its rotation:
- Tumbling rotation: the object rotates around its 3 axes, and basically this is a mess. We could be in a situation of dynamical chaos, like for the moon of Saturn Hyperion.
- Short-axis mode (SAM): the rotation is strongly dominated by a motion around the shortest axis. This is the case for many bodies in the Solar System, like the planets, our Moon… This does not mean that the rotation is strictly around one axis, but we will see that a little later.
- Long-axis mode (LAM): the rotation is strongly dominated by a motion around the longest axis.
These last two modes can actually cohabit with tumbling, i.e. a tumbling rotation may favor rotation around one axis.
If the rotation were strictly around one axis, then the body would look like a top. But this rotation axis may move with respect to the figure axis. This motion is named precession-nutation. The precession is the averaged path of the figure axis around the angular momentum, while the nutation contains the oscillations around it.
Now, imagine that you look at an object, which has such a rotation. How can you estimate it? There are ways.
Observing the rotation
Actually the brightness of a body not only depends on the distance from it, or on the insolation angle, but also on the surface facing you. This means that from the brightness, you can deduce something on the rotation state of the object. In particular, this surface brightness depends on its location with respect to the principal axis. If the object has the shape of a cigar, the reflected light from the long axis and from the short one will be different, and the lightcurve will present periodic variations. And the period of these variations is the rotation period. Easy, isn’t it?
Actually, not that easy. First, you assume that the surface has a constant albedo, i.e. that the ratio between the incident and the reflected lights is constant. But you do not know that. In particular, an icy surface has a higher albedo than a carbonaceous one. Another difficulty: a tumbling object, or even one with a precessional component in its rotation, will present a combination of different frequencies. Of course, this complicates the analysis.
However, you simplify the analysis in adding observations to your dataset. The authors used 818 observations over almost one month, spanning from Oct, 25 to Nov, 23, 2017. This includes observations from the Hubble Space Telescope, from the Magellan-Baade telescope at Las Campanas Observatory (Chile), from the Canada-France-Hawaii Telescope, from Pan-NSTARRS (these last facilities being based in Hawaii)…
Once the observations are obtained as raw data, they must be treated to correct from atmospheric and instrumental problems. And then it is not done yet, since the authors need an absolute luminosity of ‘Oumuamua, i.e. as if its distance to the observer were constant. The motion of ‘Oumuamua actually induced a trend in its distance to the Earth, and a trend in its luminosity, which the authors fitted before subtracting it the measured lightflux.
Once this is done, the authors get a lightcurve, which is constant on average, but presents variations around its mean value. Unfortunately, the required treatment induced an uncertainty in the measurements, which the authors had to consider. But fortunately, these practical difficulties are well-known, and algorithms exist to extract information from such data.
2 numerical algorithms
Basically, you need to extract periods from the variations of the lightflux. For that, we dispose of the classical tool of Fourier Transforms, which in principle requires equally spaced data. But the recorded data are not equally spaced, and remember that you must consider the uncertainties as well.
Specific algorithms exist for such a purpose. The authors used CLEAN and ANOVA, to double-check their results. These algorithms allow in particular to remove the aliasing effect, i.e. a wrong measurement of a period, because of an appropriate spacing of the data. And now, the results!
A cigar or a pancake?
The authors found two fundamental periods in the lightcurves, which are 8.67±0.34 and 3.74±0.11 hours. Interestingly, they connected these measurements to the possible dynamics of rotation, and they found two possible solutions:
- Long-Axis Mode: In that case, the possible rotation periods are 6.58, 13.15 and 54.48 hours, the latter being the most probable one.
- Short-Axis Mode: Here, ‘Oumuamua would be rotating with respect to the short-axis, but also with oscillations around the long axis of periods 13.15 or 54.48 hours.
In both axis, the long axis would also precess around the angular momentum in 8.67 ± 0.34 hours. Moreover, the authors found constraints on its shape. Previous studies already told us that ‘Oumuamua is highly elongated, this study confirms this fact, and tells us that ‘Oumuamua could be somewhere between the cigar and the pancake. But once more, this result could be weakened by variations of the surface albedo of ‘Oumuamua.
The study and its authors
- The study is here, and the authors made it freely accessible on arXiv, thanks to them for sharing!
- the web page of Olivier R. Hainaut,
- the one of Karen J. Meech,
- the one of Beatrice E.A. Mueller,
- the one of Jan T. Kleyna,
- the one of Hal (Harold) A. Weaver Jr.,
- the one of Marc W. Buie,
- the one of Michał Drahus,
- the one of Richard J. Wainscoat,
- the one of Wacław Waniak,
- the ResearchGate profile of Barbara Handzlik,
- the homepage of Sebastian Kurowski,
- the one of Siyi Xu,
- the one of Scott S. Sheppard,
- the ResearchGate profile of Marco Micheli,
- the homepage of Harald Ebeling,
- and the one of Jacqueline V. Keane. | 0.905763 | 3.932963 |
I want a short little aside here to talk about a little pet peeve of mine:
People talk as if Mars’ atmosphere does basically nothing to reduce the radiation dose as compared to free space. This is definitely not true, but the confusion comes from a few areas, but largely because people have not bothered to do some basic math and geometry.
1) People use the datum or even higher altitude sites to calculate the surface pressure. The pressure at the datum (the sort of average height on Mars, analogous to “sea level,” but not really) is 636 Pascals (6.36mbar http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html ). But the scale height of Mars is 11.1km. Scale height is the constant used to determine pressure given a simple exponential model of the planetary atmosphere. The lower altitude, the higher pressure, determined by this equation:
Where P is the pressure at the altitude “z”, and P0 is the pressure at “zero” altitude, and H is the scale height.
So at Mars, P0 = 636Pa, H=11.1km, and the lowest point on Mars is in a corner of Hellas Basin at z=-8.2km (i.e. 8.2km below the datum), whereas pretty much all of Hellas Basin is 6km below the datum. https://www.psi.edu/epo/explorecraters/hellastour.htm
That gives us an estimate of over 1300Pa surface pressure at the deepest point ( https://www.google.com/webhp?#q=636Pa*e^(8.2/11.1) ) and at least 1090Pa anywhere inside Hellas basin ( https://www.google.com/webhp?#q=636Pa*e^(6/11.1) ).
2) People forget that Mars having a lower gravity means that the mass needed to get a certain pressure is higher than on Earth. So while 1kPa on Earth would mean just 10 grams per cm^2 of shielding, on Mars it is:
https://www.google.com/webhp?#q=636Pa*e^(8.2/11.1)/(3.71m/s^2) = 35.9g/cm^2.
https://www.google.com/webhp?#q=636Pa*e^(6/11.1)/(3.71m/s^2) = 29.4g/cm^2
3) That’s already decent shielding. However, there’s another significant point: That’s just the shielding at the zenith of the sky, which is the thinnest part! Everywhere else is thicker shielding, near the horizon is MUCH more shielding.
So as you can see, the vast majority of your sky shielding (at least 70%) is over 1.4 (i.e. sqrt(2) ) times your zenith shielding. So we can write that as:
So, anywhere in Hellas Basin has basically half the dose of free space (shielded by the planet itself) PLUS another at least 40 grams per square centimeter of shielding just from the atmosphere.
EDIT: to give an idea of how much 40 g/cm² of shielding can do here is this graph that shows roughly the attenuation capabilities of polyethylene and aluminum. Mars’ atmosphere’s shielding capabilities would be somewhere between those two. While this isn’t quite enough to be happy from a GCR dose long-term (you’d want shielding on your hab), it does make EVAs far less dangerous in case of a solar flare (especially any acute effects), and also makes EVAs in general represent a much lower risk of long-term exposure. But the main effect is that solar flares represent a risk less than a tenth than the case without shielding (ie just the spacesuit).
(Also, as a side note: much of the northern part of Mars is far below the datum as well. Not quite 40g/cm^2 of shielding, but a solid 30-35g/cm^2 in many places… But there are MANY reasons why you might want to build your settlement at low altitude anyway.)
EDIT AGAIN, 2015-09-08:
Here is a graph from Rapp et al 2006 which I’ve drawn roughly where the equivalent dose of 20 cm of water shielding would be for Hellas Basin’s >40g/cm^2 of CO2 shielding. I added the red horizontal line for 20cm of water, looks to be just under 30cSv/year (I believe this is in open space, not on Mars), the green line is for 40g/cm^2 of regolith, which is a worst case for CO2 (carbon has lower atomic mass than the typical silicon, calcium, and aluminum that make up the balance of regolith besides oxygen) at about 28cSv, and 50g/cm^2 CO2 (deepest spot on Mars) with 27cSv or so for GCR annual dose. But again, this is free space. Those are just rough numbers, so that’s a bit of false precision there, but it does show that Hellas Basin has about as much equivalent shielding as a foot of water.
(caption: “Figure 1. Point estimates of 5-cm depth dose for GCR at Solar Minimum as a function of areal density for various materials (figure1.jpg). (Simonsen et al. 1997)”)
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The most efficient path to new discoveries in astronomy lies in using new technologies to view the sky in profoundly different ways. The TolTEC project does just that. Our goal is to revolutionize millimeter wavelength astronomy by producing a camera that can image huge areas of the sky and trace out the formation of structures ranging from the sizes of comets to the largest objects in the Universe. TolTEC uses a new kind of detector, called KIDS, produced by our teammates at NIST. The real power of the camera will come when it is coupled to the 50m diameter Large Millimeter Telescope. TolTEC combined with the LMT opens a new way of looking at the Universe.
The scientific case for a camera like TolTEC (that is, a camera with a high mapping speed and astounding sensitivity) was highlighted in the 2010 Astronomy Decadal Survey. TolTEC will address a wide range of scientific questions concerning: (1) cosmology and cluster physics, (2) galaxy evolution and the history of star formation in the Universe; (3) relationships between giant molecular clouds and star formation in nearby galaxies; (4) the structure of galactic molecular clouds and its relationship to star formation in the Milky Way; and (5) studies of small bodies in our own solar system. Working in collaboration with the ALMA telescope, TolTEC will provide the environmental context for the formation of astronomical objects over a vast array of spatial scales.
The TolTEC project is funded by the National Science Foundation. | 0.861591 | 3.127282 |
On the Origin of Life: Panspermia and Octopus from Space
By Dr. Kenneth Scott and Bradley Pitt
So how does life come into being in the third dimension? As we have been told in our text books, primitive life evolved here, but arrived through a type of panspermia through space.
(Key 402, v. 303)
Many people were challenged by news reports in May 2018 that suggested Octopus came to Earth from outer space, via a comet. As far-fetched as these reports appeared, they were citing a peer-reviewed article by Steele et al. (2018) published in Progress in Biophysics and Molecular Biology, which presented evidence in support of panspermia (a theory suggesting life exists throughout the universe(s) and is capable of colonizing new environments).
Steele et al. review some of the original research in panspermia, including that performed by some of their co-authors. Indeed, one of the co-authors (N. Chandra Wickramasinghe), along with Fred Hoyle, coined the Hoyle-Wickramasinghe (H-W) Thesis of Cosmic (Cometary) Biology in the 1970s. This is the thesis (or theory) being ‘tested’ in their review. They argue that there is a mounting body of evidence that either supports or is predicted by the H-W or “cosmic origins” theory of life on Earth.
In simplistic terms, the cosmic origins theory presents that at least some of the genetic diversity we see on Earth has originated from elsewhere (travelling to Earth on celestial bodies such as comets; Key 402 v. 303). That is, primitive life originated from an off-planetary source (playing a key role in the terraforming of Earth; Key 402 v. 302) but subjected to evolutionary processes according to local planetary conditions. We can then see our biome as not just limited to spaceship Earth, but as a greater cosmic biome (or cosmic gene pool). Indeed, the concept of an open-ended universe, mind and universal image (going beyond the limited boundaries of our immediate ‘universe’) is an important concept in The Keys (see Key 101-102-103). The cosmic origins theory challenges the ‘terrestrial paradigm’ (that life originated solely on Earth, e.g. in warm pools) head-on. In many ways, this paradigm perpetuates the thinking that the Earth is the centre of our universe, essentially the ‘be all and end all’. It also entrenches the view that we are unique, and that the beginning of life was a random accident that only happened here.
Note that whilst Key 402 states Darwinian evolutionary processes do occur on Earth (such as with Darwin’s Finches on Galapagos, with limited spatial and temporal scales), it states that primitive life did not evolve into the complex life forms we see on Earth today. Rather, The Keys describes the integral role of the biblically referenced Elohim and B’nai Elohim in the creation of various life forms throughout the universe. For example, Key 402 v. 411 states Life did not evolve from any singular planetary sphere exclusively by factors of Darwinistic evolution, but instead through the Light lattice established behind Creation which is superimposed by a greater Creation. For this reason, building a picture of the evolutionary history of the Earth is flawed if only examining the fossil record (the difficulties of only using the fossil record are well demonstrated by the complicated and confusing ‘bristly bush’ of the human evolutionary tree with its various genesis points over time). Importantly, The Keys (e.g. Key 402 v. 296) states that our genetic blueprint is not a happenstance creation from the chemistry of the Earth but articulated from a Higher blueprint (the Adam Kadmon).
Panspermia does not necessarily attempt to address the question of how extraterrestrial lifeforms originated (on other planets). Steele et al. argue that the coming together of biological monomers (e.g. amino acids, nucleotides) into a primitive cell capable of further evolution was too unlikely to have happened in the time frame of the Earth (4.5 billion years), but plausible if you consider evolution in terms of a cosmic biome and over the time frame of the universe (14 billion years). However, if scientists were to consider that the structure of amino acids being brought together was not a random process (Key 401 v. 266), they may be able to see beyond statistical arguments on the likelihood of (or mechanism involved with) the formation of life. What most scientists lack is the realization that matching and linking elements together for life is not a random process, but a coded process based on mathematical vibration and the WORDS (Vibrational Codings of the Logoi) which order both small and large biological molecules, such as polypeptides (proteins) made from the myriad amino acids, including the 20 basic types (10+10) used as building block monomers for life that are also to be found in outer space…(Key 402 v. 297). The Keys states that primordial proteins and nucleic acids exist throughout space, and that planets are terraformed according to the life forms planned for that system (Key 401 v. 268 & 322). In other words, Consciousness exists behind the creation of Life, rather than life simply being the by-product of a chemical soup that has the right ingredients at the right time.
Codes of life in space
As articulated by Steele et al., it seems like every month more and more Earth-like planets are being found that seem capable of supporting life. In addition, Steele et al. provide examples of how water (or at least the evidence of hydrological processes) is being found on comets and other icy solar system bodies such as Mars. This is important (especially for their cosmic origins theory), because liquid water is a prerequisite for life. Water is a ‘proton acceptor’ used to assist the formation of the nucleobases, the fundamental structure of RNA/DNA (Key 402 v. 412). Water also carries the codes of Life (demonstrated by the pioneering research of Luc Montagnier) and could be considered a medium or carrier of memory and consciousness (Key 401, v. 299). Aside from water, the medium of life, Steele et al. also describe how, using increasingly sophisticated remote sensing equipment, we are starting to detect organic molecules in space and ‘biological signatures’ on interstellar bodies, as have recently been discovered on Mars. For many people, however, the question of whether there is life in space will not be answered until the evidence is in plain sight.
We are also starting to build a much better understanding of the molecular processes associated with Darwinistic inheritance (‘vertical’, between generations), and a wide variety of Lamarckian-like inheritance mechanisms (‘horizontal’, within generations) such as where lymphocytes deliver retroviruses and somatic genes to the germline (as reviewed by Steele et al.). We are also building a much better knowledge of how viruses can drive mutagenic processes and change the structure of RNA/DNA. Whilst evolutionary biologists dismissed Lamarckian evolution long ago, advances in this field (including epigenetics) demonstrate how a minimal inherent Lamarckian adaptation does occur in nature (Key 401 v. 249).
Octopus from Space
Let’s now turn to the Octopus, which has a ‘highly inconsistent and confusing’ evolutionary history according to Steele et al. Most readers would be familiar with a tree-like diagram that shows the evolutionary relationships between species. The closer two species are on the tree, the more similar they should be. Modern-day cephalopods (to which Octopus belong) have certain features, such as a large brain and a sophisticated nervous system, which appeared quite suddenly on the evolutionary tree next to its ancestors. In addition, members of the Octopus family possess a specific molecular genetic strategy (transcriptional modifications) whereby nearly all protein-coding genes show Adenosine-to-Inosine (A-to-I) editing sites in their mRNA, but not its ancestor, the nautilus. From an evolutionary point of view, this is significant because it is thought to allow for the repair of defects in gene sequences. Normally, this molecular strategy arises incrementally along an evolutionary line, rather than the instantaneous jump upward seen in Octopus. This (and other data) led Steele et al. to assume that the complex features seen in Octopus could not be explained by neo-Darwin or Lamarckian theories of evolution. Instead, they proposed that crypto-preserved Octopus eggs could have arrived on icy bodies, around the time of the appearance of these species on the evolutionary tree on Earth. The same could be said for the plant seeds too. Of course, the conditions must be right on Earth for those organisms to flourish.
Celestial bodies as carriers
Because the H-W cosmic origins theory involves genes arriving on celestial bodies (meteorites etc.), periods of the Earth’s history with a high incidence of meteorite impacts are predicted by Steele et al. to be periods of change in species composition (extinctions and new species introduced into the fossil record). Such a period of impacts and resultant species composition change occurred with the ‘Cambrian Explosion’. Note that extinctions can also occur very rapidly as a consequence of changes in the Earth’s magnetic cycles, set in motion by cosmic oscillations (Key 304).
Steele et al. review recent findings that viable microbes were found to exist in the stratosphere, about 30-40 kilometres (18-25 miles) above the Earth. Whilst some of these could be accounted for from upwelling from the ground, or contamination of the equipment used to study them, some could not. Steele et al. concluded it is plausible these microbes came to Earth via micron-sized meteorites or icy comet meteors about 1 meter in diameter. They postulated that during solar storms, these microbes could be propelled towards the surface of the Earth. Accordingly, the authors encouraged biologists to examine the apparent correlation between viral epidemics and the sun spot flare cycle (such as for influenza epidemics), where it is suggested that solar activity could assist in the descent of ‘charged molecular aggregates’ (including viruses) from the stratosphere to the ground along magnetic field lines.
As a core feature of the cosmic origins theory, Steele et al. proposed that viruses from the cosmos contribute to evolution on Earth (a ‘retroviral induction model’). They stated that viruses and their elements (e.g. reverse transcriptase enzymes) appear to be important viral-drivers of evolutionary genetic change on Earth, i.e. horizontal gene transfer (integrating their own genetic material into the genome of the infected host). The authors proposed that the Earth was seeded with sophisticated viral gene vectors, including at the time of the Cambrian Explosion, where genetic diversity increased many-fold.
In conclusion, Steele et al. stated…we came from space, we are made of viral genes, and eventually our evolutionary legacy would in full measure return to space. This is not entirely inconsistent with The Keys of Enoch, for The Keys states how we will understand our true identity is not Earth-bound, but from a Higher blueprint, as we go from Homo sapiens sapiens into Homo Universalis in the Father’s House of Many Mansions. We will come to the realization that –
Life is throughout the Cosmos – we are living in a Living Cosmos with abundant life – functioning on multiple dimensions of existence and throughout spacetime.
(Key 402 v. 410)
- https://www.sciencedirect.com/science/article/pii/S0079610718300798?via%3Dihub. Steele et al. (2018) Cause of Cambrian Explosion–Terrestrial or Cosmic? Progress in Biophysics and Molecular Biology 136, 3-23. ↑
- The purpose of this article is to explore some of the concepts presented by Steele et al. in relation to concepts in a series of books published by Dr. J.J. Hurtak beginning with The Book of Knowledge: The Keys of Enoch (The Keys), first published in 1973. The most recent book/Key (2017) we refer to is Key 402. ↑
- This view is not supported by The Keys. ↑
- Eigenbrode, Jennifer L. et. al. (2018) “Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars” Science 08 Jun 2018: Vol. 360, Issue 6393, pp. 1096-1101DOI: 10.1126/science.aas918. ↑
- Adenosine deaminases (enzymes) bind to double-stranded RNA and deaminate adenosine to form inosine. Inosine is translated as guanosine, and so A-to-I editing can alter the amino acid sequences of proteins. ↑ | 0.864858 | 3.604288 |
The Sun is our closest star, and without it life on our world could not survive. So it is essential to understand its nature. And yet, even though the Sun shines brightly on every clear day on Earth, it is difficult for astronomers to observe the star closely for a number of reasons.
Most obviously, it is hot—so hot, it is difficult to get too close without getting burnt to a crisp. Additionally, due to high solar gravity, it requires a lot of energy to insert a spacecraft into an orbit near the Sun. The harsh radiation near the Sun also plays havoc with the scientific instruments on spacecraft.
For all of these reasons, while astronomers have made steady progress in understanding the Sun and its effects on Earth, our atmosphere, and other bodies in the Solar System, we still have big questions. The good news is that we are now entering the golden age of Solar research with a major new ground-based telescope and two space-based observatories that will come close to the Sun.
"There is no doubt that the observations and insight will be unprecedented—exploring new regions with new instruments in incredible detail," David Alexander, a solar physicist at Rice University and director of its space institute, told Ars.
First light in Hawaii
You may have seen the amazing images recently released by the Daniel K. Inouye Solar Telescope, which is located on a mountaintop at 3,084 meters in Maui, Hawaii. With a 4-meter aperture, it is the world's largest solar telescope. The new images were part of the first test observations, with routine science observations set to begin this summer.
Images and video of the Sun from the telescope showcase features as small as 30km, the best resolution ever observed. Cell-like structures about the size of Texas—they also look like popcorn, or small nuggets of gold—boil across the Sun's surface, bringing heat from the interior of the star to the surface. This hot plasma then cools slightly and sinks back below the surface of the Sun. It is all rather mesmerizing.
This telescope also has scientific instruments that will allow it to measure the magnetic field in the solar corona in great detail. This will help scientists understand more fully how the energy in the Sun’s magnetic field gets released to heat the corona and drive flares and coronal mass ejections, Alexander said.
NASA's Parker Solar Probe launched on a Delta IV Heavy rocket in 2018 and will eventually pass as close to the Sun's surface as seven times the star's radius. This probe has already provided a wealth of new science data, bringing insight into the solar wind, and will only yield more as it spirals closer to the Sun.
As early as Sunday night, February 9, the Solar Orbiter spacecraft built by the European Space Agency will also launch on an Atlas V vehicle. This spacecraft will not go nearly so close to the Sun as the Parker Solar Probe, but it will reach the orbit of Mercury in terms of proximity and leave the ecliptic to provide scientists with by far their best look at the Sun's poles. (The Ulysses spacecraft, launched in 1990, had a polar orbit but at distances of about 2 to about 5 times Earth's distance from the Sun, and it only possessed a suite of in-situ instruments with no camera).
These new probes will build upon astronomers' existing information about the Sun. Already, this body of knowledge has grown considerably over the last decade thanks to instruments such as the Solar Dynamics Observatory, which is in geostationary orbit around the Earth and has provided a great amount of high-resolution imaging data. With the three new scientific tools, we are about to have a much more complete view of our Sun as a star, which matters not only for us, but also as we look to worlds around other stars.
"Over the course of the next 5 to 10 years we will have a much deeper understanding of the Sun as a star, which can have a significant impact on our understanding of exoplanet environments and as a consequence improve our understanding of what makes a planet habitable," Alexander said. | 0.866232 | 3.835826 |
Time travel enchants the imagination of many people. We know a lot of films on this topic, from “Terminator” to “Back to the Future”. There are even those who think that time travelers live and are now among us. To date, we have no evidence that time travelers really exist. The only time travelers are those whom we see on the movie screens. However, we have many theories about the way people can travel in time and why it is possible. Here is 10 Time Travel Possible Proof.
10. Einstein’s General theory of relativity
The first theory in this list is Einstein’s general theory of relativity, which helped physicists theoretically substantiate the possibility of such travels. The general theory of relativity gives an idea of the way objects create distortion on the space-time continuum in space, which we know as gravity. Gravitation itself does not lead to time travel, but it creates phenomena (both proven and theoretical) that make time travel possible.
Physicists used this theory to come up with and explain “wormholes” and “black holes”. Next, we will discuss both of these phenomena. Both these theories speak of “holes” in space and time, with the help of which one can travel.
The second theory which we will consider here fuels a lot of hopes, but it does not have any real evidence. In space, no “wormhole” was found, but scientists still believe that they can be there. Physicists assume their existence, based on Einstein’s theory of relativity, and if they really exist, then they can prove to be a way of time traveling.
It is assumed that “wormholes” are “tunnels” that can bind individual regions of the universe. This could mean that if someone entered the wormhole, he might end up in another part of the universe or in another time. Besides existence itself, this theory has one more problem: if they existed, they would be so small that a person could not penetrate them. Although there is no real evidence of the existence of “wormholes”, when it comes to time travel, this theory is one of the leading.
8. Black holes
“Black holes” are areas in the universe with such strong gravity that they absorb light. Their appearance is caused by the birth of a new star or a collision of stars. Physicists believe that everything that falls into the “black hole” will never disappear. Their force of attraction is so great that even the time in them slows down. To travel in time, you need to learn to approach the “black hole” so that it does not tighten you.
Because of the strong gravity, the time course on the spacecraft will be significantly different from the course of time on Earth. It will slow down considerably. That is, when you return to Earth, you will be much younger than your former peers. It is clear that no one has tried to verify this yet, but it is possible that this will happen in the future.
7. Cosmic strings
Space strings are narrow tubes of energy that permeate the universe. It is believed that they appeared right after the Big Bang and have a huge mass. Thus, they can change the space-time around themselves. Scientists also believe that these strings should either lock themselves in loops or exist as straight infinite lines. If these strings do exist, then there is a possibility that they can facilitate movement in time.
Scientists suppose that if two cosmic strings passed parallel and were located close enough to each other, they could bend space and time. This curvature would make time travel possible. The principle of operation here is about the same as in the case of “black holes”.
6. Time Machine
We have already seen time machines in countless films, and probably you have imagined the moment when you go into such a car, you would be in the past or the future. While there are no such machines, the theory of their construction is always attractive.
Scientists believe that to create such a machine, they need a matter with the negative energy density (the so-called “exotic matter“). This property can lead to many consequences, including the movement in time. The problem is that if even this kind of matter could be obtained, it would be not enough to create a time machine.
5. Travel at a speed faster than the speed of light
In some respects, this can be called the “Superman Theory“. In the movie “Superman” (1978), the main character returns to the past, flying so fast that the Earth begins to rotate in the opposite direction. Of course, this is ridiculous, so later it was explained that in fact, Superman returned to the past because he exceeded the speed of light. Why is it possible? The speed of light is considered to be the final speed, it does not happen faster. If someone exceeds the speed of light, he will arrive at the destination sooner than he left the point of departure. Thus, it turns out that this person will make a journey in time.
The huge drawback of this theory is that the speed of light can not be exceeded. In addition, scientists studying this concept have found that it is necessary to observe many more factors, just the excess of the speed of light will not be enough.
4. Tyler cylinder
It is almost impossible to test this theory, but it is a very interesting idea of how much mass we need for traveling through time. According to this theory, we need to find a piece of matter which mass will be ten times larger than the mass of the Sun. Then from it, we need to create a very tight, long and thin cylinder. In our universe, there are many objects which mass exceeds the mass of the Sun, but it is difficult to imagine how to make a similar cylinder of them.
In addition, this cylinder should rotate at a speed of several billion rpm. If we managed to meet all these factors, then the spacecraft, following a spiral around the cylinder, could enter into a closed time curve. This would allow the spaceship to travel in time.
The film “Interstellar” shows a journey through time in many different ways. Characters of the film travel with the help of “wormholes” and revolve around the “black hole”. In addition, the film shows how you can travel through time with the help of a tesseract – a multidimensional cube. Tesseracts can be projected into two- and three-dimensional forms.
For a journey through time, the tesseract must have more than three dimensions. When the spacecraft enters the tesseract, time begins to be represented as one of the dimensions of space. It allows the ship to reach various points of this space, which is shown in “Interstellar”. This theory is not based on anything, but we will never know what the future is preparing for us.
2. “Paradox of the Murdered Grandfather”
This theory deals not so much with the time travel itself, but with what it can lead to. If someone could go to the past, it could do great harm to his future. For example, take the “Paradox of the Murdered Grandfather“. Suppose you invent and create the time travel machine. Then you return to the past and meet your own grandfather before he has children. Then for some reason, you kill him. Now you will never be born again, and no one will create the time travel machine that had brought you to the past.
In many TV shows and movies, we’ve seen villains returned to the past to try to kill someone before they could do good in the future. An example of such a plot is the film “Terminator”. So, no matter how fascinating we seem to travel in time, it could have many consequences for our present.
1. Travelers in time are already among us?
There are many theories about people who can be travelers in time. There are many strange stories that convince some people that someone has already mastered this art and that these travelers live among us. One of the most famous examples was the episode in the film Charlie Chaplin from “The Circus“. People say that we see a passerby talking on a mobile phone. This film was released in 1928, long before the advent of mobile phones. The film is black and white, and the image is a little blurry, but it’s easy to guess why people think that this is really a mobile phone.
Another of the recent theories is that the creator of the series “The Simpsons” is also a traveler in time. There were many episodes in which the future was accurately predicted. “The Simpsons” successfully predicted such events as Donald Trump’s presidency and the year in which the “Chicago Cubs” won the World Series. Such forecasts have caused some viewers to suspect that it all was not accidental. | 0.848697 | 3.108545 |
The first automatic partially reusable spacecraft was the Buran-class shuttle, launched by the USSR on November 15, 1988, although it made only one flight and this was unmanned. This spaceplane was designed for a crew and strongly resembled the U.S. Space Shuttle.
Before studying the effects that the motions of the stars have had and will have upon the constellations, it is worth while to consider a little further the importance of the stellar pictures as archives of history. To emphasize the importance of these effects it is only necessary to recall that the constellations register the oldest traditions of our race. A knowledge has been obtained of their height above the ground during their flight and of the length of their visible courses.
The fall of meteorites offers an appreciable, though numerically insignificant, peril to the inhabitants of the earth. Historical records show perhaps three or four instances of people being killed by these bodies. But for the protection afforded by the atmosphere, which acts as a very effective shield, the danger would doubtless be very much greater.
It has been calculated that on a clear night the total starlight from the entire celestial sphere amounts to one-sixtieth of the light of the full moon; but of this less than one-twenty-fifth is due to stars separately distinguished by the eye. If there were no obscuring medium in space, it is probable that the amount of starlight would be noticeably and perhaps enormously increased.
It is a singular fact that recent investigations seem to have proved that an event of this kind actually happened in North America — perhaps not longer than a thousand or two thousand years ago.– William A. Miller
This leads us back again to the wonderful group of the Pleiades. All of the principle stars composing that group are traveling in virtually parallel lines. Whatever force set them going evidently acted upon all alike.
At the surface such a body is enveloped in a shell of relatively cool matter. Now suppose a great attracting body, such as another sun, to approach near enough for the difference in its attraction on the two opposite sides of the body and on its center to become very great the consequence will be a tidal deformation of the whole body, and it will lengthen out along the line of the gravitational pull and draw in at the sides
But serious questions remain. It needs, for instance, but a glance at the Triangulum monster to convince the observer that it cannot be a solar system which is being evolved there, but rather a swarm of stars. Many of the detached masses are too vast to admit of the supposition that they are to be transformed into planets, in our sense of planets, and the distances of the stars which appear to have been originally ejected from the focal masses are too great to allow us to liken the assemblage that they form to a solar system. | 0.884598 | 3.747766 |
The Moon is the only natural satellite of the Earth,[d] and the fifth largest satellite in the Solar System. It is the largest natural satellite of a planet in the Solar System relative to the size of its primary,[e] having 27% the diameter and 60% the density of Earth, resulting in 1?81 its mass. The Moon is the second densest satellite after Io, a satellite of Jupiter.
The Moon is in synchronous rotation with Earth, always showing the same face with its near side marked by dark volcanic maria that fill between the bright ancient crustal highlands and the prominent impact craters. It is the brightest object in the sky after the Sun, although its surface is actually very dark, with a reflectance similar to that of coal. Its prominence in the sky and its regular cycle of phases have, since ancient times, made the Moon an important cultural influence on language, calendars, art and mythology. The Moon's gravitational influence produces the ocean tides and the minute lengthening of the day. The Moon's current orbital distance, about thirty times the diameter of the Earth, causes it to appear almost the same size in the sky as the Sun, allowing it to cover the Sun nearly precisely in total solar eclipses. This matching of apparent visual size is a coincidence. The Moon's linear distance from the Earth is currently increasing at a rate of 3.82±0.07cm per year, however this rate is not constant. The large amount of energy
eleased in the giant impact event and the subsequent reaccretion of material in Earth orbit would have melted the outer shell of the Earth, forming a magma ocean. The newly formed Moon would also have had its own lunar magma ocean; estimates for its depth range from about 500 km to the entire radius of the Moon. Despite its accuracy in explaining many lines of evidence, there are still some difficulties that are not fully explained by the giant impact hypothesis, most of them involving the Moon's composition.
In 2001, a team at the Carnegie Institute of Washington reported the most precise measurement of the isotopic signatures of lunar rocks. To their surprise, the team found that the rocks from the Apollo program carried an isotopic signature that was identical with rocks from Earth, and were different from almost all other bodies in the Solar System. Since most of the material that went into orbit to form the Moon was thought to come from Theia, this observation was unexpected. In 2007, researchers from the California Institute of Technology announced that there was less than a 1% chance that Theia and Earth had identical isotopic signatures. Published in 2012, an analysis of titanium isotopes in Apollo lunar samples showed that the Moon has the same composition as the Earth, which conflicts with the moon forming far from Earth's orbit or from Theia. Variations on GIH may explain this data. | 0.824494 | 3.875839 |
Black holes are objects that have long been theorised by scientists for centuries. Just as you have to travel faster to leave Earth than you to do to leave the Moon, it was theorised that such places could exist where you would have to travel faster than light to escape them. Early descriptions of such objects were called ‘dark stars’; a star so large and massive that its own gravitational pull would pull in the light it should be emitting. Albert Einstein made this idea popular in his theory of general relativity, which includes equations to measure such strong gravitational pulls. The object in question would have an edge known as the event horizon, a point at which you can never return if you cross it. Even light, the fastest thing in the universe, would not be able to escape. The problem with ever seeing a black hole is exactly that, they are black. They do not emit or reflect any type of light. The closest known black holes are also very far away and appear tiny in the sky due to their distance from us. How could astronomers possible see an object that was virtually unseeable?
Scientists have been searching for a supposed black hole lying in the centre of our own galaxy known as Sagittarius A* (or Sgr A*) for over 20 years. Using powerful telescopes on Earth, they observed star movement near its centre over a 16-year period. The results showed that the stars were being whipped around in highly elliptical orbits at extremely fast speeds, all orbiting an invisible point. How could these stars possibly be orbiting nothing? This was some of our first indirect evidence for the existence of black holes. Such a black hole in our galaxy would have as much mass as roughly 4 million Suns yet would fit inside the orbit of Mercury. These telescopes were not powerful enough to resolve such a small and distant object.
A super massive black hole (originally named as M87*) has long been theorised to be lying in the centre of another galaxy known as Messier 87. This black hole was calculated to be far larger than the one in our own Milky Way and we’ve observed large jets of plasma being ejected from the core at almost-light speeds. Sgr A* and M87* both became targets of an ingenious network of telescopes that became known as the Event Horizon Telescope (EHT).
No single telescope on Earth is powerful enough to observe either of these black holes alone. The EHT solved this problem by linking up eight different radio telescopes around the world to create a virtually Earth-sized telescope dish. Scientists pointed this network of telescopes at both Sgr A* and M87* back in 2017, observing both for several weeks at a time. The EHT collected so much data that it could not be uploaded and synced over the internet. It had to be shipped around the world using physical hard drives so that it could be processed using supercomputers. The result was the first ever image of a black hole. The image released in April of 2019 shows the super-massive black hole lying in the centre of Messier 87. This super massive blackhole was given an official name; Powehi (pronounced po-ve-hee). This name comes from Hawaiian creation legend, meaning ‘adorned fathomless dark creation’. It is an acknowledgement to the Hawaiian observatory that contributed to the EHT network.
So, what exactly am I looking at? Until this image was released, all black holes that you may have seen are artistic representations. They are renderings of what we thought a black hole would look like from using mathematical models and physics. You may remember seeing the incredible imagery of a black hole in the film Interstellar. The image of Powehi may not look as spectacular as the one in interstellar, but they are very similar. What you are seeing is a ring of matter, rapidly being spun around the black hole while being superheated due to friction. This is known as an accretion disk and its what allowed us to see the silhouette of Powehi. This ring of light is warped around the black hole due to the incredible forces of gravity bending light rays. The brighter spots are matter that is moving towards us, while dimmer regions are moving away. Powehi was chosen to observe because it is so large spanning over 38 billion km. Just to give you an idea of size, Pluto is around 6 billion km away. This black hole would engulf our entire Solar System with room to spare. No need to worry though, as Powehi lives almost 53 million light years away! Results from the observation of Sag A* in our own galaxy are expected in the not too distant future, but even that black hole is roughly 26,000 light years away.
Dr. Katie Bouman of MIT led the team who developed the imaging algorithm that made imaging Powehi possible. The incredible results of the EHT are a testament to the importance of scientific collaboration and transparency. No single organisation or group would have been able to take this incredible image alone. Hundreds of people from dozens of countries worked in unison to achieve something that was once thought impossible through science.
Josh Kirkley, Astronomy Educator
L: The first ever image of a black hole, showing the super massive black hole that lies in the centre of the galaxy Messier 87.
R: A wide view of the region around the super massive black hole, taken by the Chandra telescope. | 0.925256 | 4.056985 |
On the surface, telescopes and microscopes might appear to function the same. They both have lenses, they both magnify objects, and they both bring the invisible world into focus. But underneath, these two devices use opposite mechanics to bring images to your eye. In fact, their opposite qualities are what determine the behavior of the light captured within them. Understanding the way each device works will help differentiate the two in your mind.
The primary difference between a microscope and a telescope is the focal length. This is the length through which light travels inside the device. The longer focal length of a telescope makes images smaller, which means you can make planetary objects shrink to fit inside your eyepiece. The shorter focal length of a microscope makes images larger, which means a molecule can appear the size of a baseball. While both devices use a focal point (the place where parallel rays of light converge) to capture an image, the focal length ultimately determines if an object will appear shrunken or enlarged.
Deep-sky objects like planets and moons don’t create their own light. This means a telescope must pull in as much light as possible to capture an image. The larger the lens diameter, the more light is absorbed, creating images far beyond the range of normal human sight. But a microscope comes equipped with its own light source (or can utilize the natural light of the environment), which makes smaller diameter lenses most effective. Too much light and your microscopic specimen will look blurred.
The two devices are also opposite in their adjustability. A telescope has a fixed objective lens, but a changeable eyepiece. This means the object must be far away to see a crisp image of it. Telescopes have a big footprint, too. They can take up a corner of a room or require an entire building to house them.
A microscope has a fixed eyepiece and three or more changeable objective lenses. If you want to focus on an object, it must be close. Their footprint is typically small, taking up only a small spot on your desktop. Even the largest microscopes are dwarfs in comparison to the largest telescopes.
While these two devices are opposites in most respects, their power to magnify the invisible has changed the way we understand nature and the cosmos. Whether you need to examine the galaxy residing in a bacterium or look outward to a galaxy full of stars, magnification will change the way you see the world.
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8×42 vs 10×42 Binoculars: What Should You Choose? | 0.846293 | 3.606982 |
A NASA scientist just announced a promising new theory about a possible link between primordial black holes and dark matter.
Dark matter, a mysterious substance composing approximately 27% of the mass and energy in the observable universe, that appears to exert a gravitational force, without emitting any form of energy that scientists can detect, widely thought to be some form of massive exotic particle.
Above, left: This image from NASA’s Spitzer Space Telescope shows an infrared view of a sky area in the constellation Ursa Major. Right: After masking out all known stars, galaxies and artifacts and enhancing what’s left, an irregular background glow appears. This is the cosmic infrared background (CIB); lighter colors indicate brighter areas. The CIB glow is more irregular than can be explained by distant unresolved galaxies, and this excess structure is thought to be light emitted when the universe was less than a billion years old. Scientists say it likely originated from the first luminous objects to form in the universe, which includes both the first stars and black holes. Credits: NASA/JPL-Caltech/A. Kashlinsky (Goddard)
An intriguing alternative view is that dark matter is made of black holes formed during the first second of our universe’s existence, known as primordial black holes.
Now a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, suggests that this interpretation aligns with our knowledge of cosmic infrared and X-ray background glows and may explain the unexpectedly high masses of merging black holes detected last year.
Alexander Kashlinsky, an astrophysicist at NASA Goddard, said:
“This study is an effort to bring together a broad set of ideas and observations to test how well they fit, and the fit is surprisingly good. If this is correct, then all galaxies, including our own, are embedded within a vast sphere of black holes each about 30 times the sun’s mass.”
Primordial black holes, if they exist, could be similar to the merging black holes detected by the LIGO team in 2014. This computer simulation shows in slow motion what this merger would have looked like up close. The ring around the black holes, called an Einstein ring, arises from all the stars in a small region directly behind the holes whose light is distorted by gravitational lensing. The gravitational waves detected by LIGO are not shown in this video, although their effects can be seen in the Einstein ring. Gravitational waves traveling out behind the black holes disturb stellar images comprising the Einstein ring, causing them to slosh around in the ring even long after the merger is complete. Gravitational waves traveling in other directions cause weaker, shorter-lived sloshing everywhere outside the Einstein ring. If played back in real time, the movie would last about a third of a second. Credits: SXS Lensing
Read more at NASA | 0.830433 | 4.095894 |
When I think about Carl Sagan, the tenth anniversary of whose death we remember today, the first thing that comes to mind is a quote about the wonders of relativistic interstellar flight. It’s worth quoting at length:
If for some reason we were to desire a two-way communication with the inhabitants of some nearby galaxy, we might try the transmission of electromagnetic signals, or perhaps even the launching of an automatic probe vehicle. With either method, the elapsed transit time to the galaxy would be several millions of years at least. By that time in our future, there may be no civilization left on Earth to continue the dialogue. But if relativistic interstellar spaceflight were used for such a mission, the crew would arrive at the galaxy in question after about 30 years in transit, able not only to sing the songs of distant Earth, but to provide an opportunity for cosmic discourse with inhabitants of a certainly unique and possibly vanished civilization. Despite the dangers of the passage and the length of the voyage, I have no doubt that qualified crew for such missions could be mustered. Shorter, round-trip journeys to destinations within our Galaxy might prove even more attractive. Not only would the crews voyage to a distant world, but they would return in the distant future of their own world, an adventure and a challenge certainly difficult to duplicate.
That’s from Intelligent Life in the Universe, which Sagan and Iosef Shklovskii published in 1966 (Holden-Day, pp. 443-444). It’s actually a translation and extended revision of Shklovskii’s older Universe, Life Mind, and the quote draws on a 1963 Sagan paper called “Direct Contact Among Galactic Civilizations by Relativistic Interstellar Flight” (Planetary and Space Science 11, pp. 485–98). Sagan had sent Shklovskii the paper even before the latter’s book appeared. The result in English became a collaborative effort that drew on the wisdom of two outstanding minds.
I don’t know how many space scientists were fired by this vision of human voyaging not just to another star but another galaxy, but I suspect this book still sits on the shelf of many a researcher. It awoke in me the sense of awe that Poul Anderson would go on to tap in Tau Zero, his fine novel about a runaway starship that makes Sagan’s 30-year voyages to Andromeda seem tame by comparison. But that’s what Sagan did. He could render hard science into celestial mental voyaging.
Good scientists do that in their own minds. Sagan’s genius was the ability to convey it to a broad audience, using prose that was supple and keen as a knife-edge. The great mystery writer Ross Macdonald once said of Raymond Chandler that he wrote ‘like a slumming angel.’ It’s the perfect phrase for Sagan as well, whose voice was distinctive and marked by a preternatural clarity. When Cosmos widened his reach to television, he was able to bring the discoveries of our telescopes and spacecraft into the home and (with a kind of poetry) show us where we stood in the universe.
Pale Blue Dot (1994) was Sagan at his best as he ranged through the Solar System and looked back on a distant Earth. Here’s the memorable conclusion:
The Cosmos extends, for all practical purposes, forever. After a brief sedentary hiatus, we are resuming our ancient nomadic way of life. Our remote descendants, safely arrayed on many worlds through the Solar System and beyond, will be unified by their common heritage, by their regard for their home planet, and by the knowledge that, whatever other life may be, the only humans in all the Universe come from Earth.
They will gaze up and strain to find the pale blue dot in their skies. They will love it no less for its obscurity and fragility. They will marvel at how vulnerable the repository of all our potential once was, how perilous our infancy, how humble our beginnings, how many rivers we had to cross before we found our way.
A slumming angel indeed. Thank you, sir.
Note: As Larry Klaes just pointed out in a comment to this post, Joel Schlosberg is conducting an ongoing Sagan tribute centered on this day, and Larry also notes the Celebrating Sagan weblog in his honor. Larry’s own tribute to Sagan in the Ithaca Times is here. Music of the Spheres has a fine recollection as well. Be sure to read Airminded’s homage, and finally, check Ann Druyan’s thoughts about her late husband. | 0.881224 | 3.370613 |
Rapid Neutral-Neutral Reactions at Low Temperatures?
Before the work of our group initiated here in Rennes, it was widely believed that rate constants for neutral-neutral reactions would become vanishingly small at the low temperatures of dense interstellar clouds, owing to the presence of substantial energetic barriers on the minimum energy path connecting reactants to products (case (a) above). Processes involving charged species, such as ion-molecule reactions, are generally barrierless, along with a limited number of reactions between two neutral radicals (case (b)), and these processes were assumed to dominate the chemistry of low temperature environments. In the early 1990s, a joint project was initiated between the Rennes group, directed at the time by Bertrand Rowe, and the gas kinetics and dynamics group of Ian W.M. Smith at Birmingham, to study the kinetics of neutral-neutral reactions down to very low temperatures using the CRESU technique. The first results on reactions of the CN radical shown to the right, demonstrated that rate constants for reactions between radicals and molecules could remain rapid or even increase at low temperatures, and therefore be of importance in low temperature environments such as dense interstellar clouds and planetary atmospheres.
The Descartes Prize
These results and subsequent developments in Rennes and Birmingham resulted in the award of one of the first Descartes Prizes of the European Union in 2000, for a project entitled “Chemistry Close to Absolute Zero”. The Descartes Prize “is awarded for outstanding scientific or technological results from European collaborative research.”
And today ?
Research on neutral-neutral reactions at very low temperatures continues in Rennes, spurred on by technical innovations and the demand for data from astrochemical modellers and planetary scientists. Recently, for example, the group have measured the rate constant for the reaction F + H2 → HF + H down to 11 K (M. Tizniti, S. D. Le Picard, F. Lique, C. Berteloite, A. Canosa, M. H. Alexander, and I. R. Sims, Nature Chemistry 6, 141 (2014)). This has enabled astronomers to link observations of HF in the interstellar medium by the Herschel Space Observatory with the abundance of H2, and hence effectively the total mass of interstellar objects such as molecular clouds. | 0.831477 | 3.653401 |
Imagine trying to see a firefly next to a distant spotlight, where the beams from the spotlight all but drown out the faint glow from the firefly. Add fog, and both lights are dimmed. Is the glow from the firefly still visible at all?
That is the question the Hunt for Observable Signatures of Terrestrial Systems, or HOSTS, Survey was tasked with answering, albeit on a cosmic scale. Using the Large Binocular Telescope Interferometer, or LBTI, in Arizona, the HOSTS Survey determines the brightness and density of warm dust floating in nearby stars' habitable zones, where liquid water could exist on the surface of a planet.
This research will contribute to a once-per-decade report on the field of astrophysics, produced by the National Academies, that NASA uses to help chart a course for future missions, some of which could continue the search for planets around other stars, known as exoplanets. But before telescopes for prospective exoplanet-hunting missions can be designed, astronomers must know if there is a fundamental limit to their ability to see a tiny, dim planet next to a bright star when the system is shrouded in dust.
"Our result is that there is no fundamental problem," said Steve Ertel of the University of Arizona's Steward Observatory, instrument scientist for the Large Binocular Telescope Interferometer and lead author on the paper, "The HOSTS Survey – Exo-Zodiacal Dust Measurements for 30 Stars," which is published in the in the Astronomical Journal. "Now it is a technical challenge."
A potential mission to search for terrestrial planets probably would include a space-based telescope, and the HOSTS Survey will help determine its size.
"The more dust there is, the bigger the telescope has to be to image a planet," Ertel said. "It is important to know what telescope size is required, so the costs can be minimized."
The dust that orbits in the plane of our solar system is known as "zodiacal dust." The HOSTS Survey has determined that the typical level of zodiacal dust around other stars — called "exo-zodiacal dust" — is less than 15 times the amount found in our own solar system's habitable zone. Stars with more than that amount of dust make poor targets for future exoplanet imaging missions, as planets would be difficult to see through the haze. One such star with a prominent dust disk, called Epsilon Eridani, is one of the 10 nearest stars investigated by the HOSTS Survey.
"It is very nearby," Ertel said. "It’s a star very similar to our sun. It would be a very nice target to look at, but we figured out that it would not be a good idea. You would not be able to see an Earth-like planet around it."
'That's Our Best Guess'
If dust and debris make finding rocky worlds challenging, then why search for planets in dusty systems?
"There is dust in our own solar system," said Philip Hinz, the lead for the HOSTS Survey team and associate professor of astronomy at the UA. "We want to characterize stars that are similar to our own solar system, because that's our best guess as to what other planetary systems might have life."
The pattern of dust distribution around a host star also can tell astronomers something about the potential planets in a star system. Some stars have wide, continuous disks that fill the whole system. This is considered a standard model, as dust is formed during asteroid collisions far from the star and then spirals inward toward the star so that it is evenly distributed throughout the system.
"This is something that we expected to see, but we also saw some surprises," Ertel said.
Take Vega, one of the brightest stars in the night sky. For more than 30 years, astronomers have known that Vega has a massive belt of cold dust far from the star, analogous to our solar system's Kuiper Belt. The star also has a disk of hot dust very close to it.
"We were thinking that Vega must have dust in the habitable zone as well, because it has dust very close and dust farther away," Ertel said. "But we looked at Vega's habitable zone and we didn't find anything."
Vega's habitable zone is devoid of detectable dust, which could indicate that the system has planets that prevent dust from collecting there. Planets have not yet been detected around Vega, but current observations are not even sensitive enough to detect a planet as large as Jupiter near the star, let alone Earth-like planets.
"This could be an indication of a planet we cannot see," Ertel said. "It could be a massive planet outside the habitable zone, or it could be several Earth-mass planets."
Other stars had different dust distributions: nothing far away or very close, but huge amounts of bright, warm dust in their habitable zones. If a star does not have a Kuiper Belt analogue producing dust, but it still has a ring of warm dust, there must be another mechanism at play in the system.
"There might be giant planets like Jupiter and Saturn in that system, but that system's asteroid belt has a lot of mass to it, so you're getting a lot of collisions that make large amounts of dust," Hinz said.
Studying these dust disks provides astronomers with more pieces to the puzzle of planetary architecture. While past studies have looked for planets very close to, and very far away from, stars to determine where planets are typically located in star systems, the HOSTS Survey is determining how dust and asteroid belts appear in the average star system.
"The survey is ongoing, so we have more questions than answers," Hinz said. "We are in the early days for trying to figure out how it all fits together."
Exo-zodiacal dust has been warmed to room temperature by its host star, so it glows when viewed in infrared wavelengths — that is, in infrared light, emitted by heated objects. However, at those wavelengths, stars glow 10,000 times brighter than the dust. To see how much dust was swirling around their chosen 30 stars, the HOSTS Survey detected the dust disks using a technique called "Bracewell nulling interferometry," after Ronald Bracewell, the astronomer who first suggested the method.
"Interferometry means 'measuring the interference between two wave trains,'" Hinz said.
The Large Binocular Telescope, or LBT, has the unique capability to perform this interferometry, as it is designed so that its twin telescopes can each detect light waves that are perfectly out of phase with each other. When waves are out of phase, they cancel each other out, causing their peaks and troughs to flatten.
"The result is that you cancel out the light from the star," Hinz said.
A similar technique was introduced in 1998, using the Multiple Mirror Telescope on Arizona's Mount Hopkins.
"It took almost 20 years to refine the technique so it is precise enough so that we could get rid of the star and sensitive enough so that we could see the remaining light from the dust," Hinz said.
Achieving this cancellation requires that the LBT be adaptable. After light bounces off the telescope's 8-meter primary mirrors, it reflects off the secondary mirrors and into detectors. The secondary mirrors are deformable so that they can correct for the distortions of light caused by ripples in the atmosphere. In order for the interferometry to work, these corrections must be accurate to one one-hundredth of the width of a human hair.
The LBTI is funded by NASA's Exoplanet Exploration Program office and managed by the agency's Jet Propulsion Laboratory in Pasadena, California. JPL is a division of Caltech. The LBTI is 10 times more sensitive than the previous telescope capable of detecting exo-zodiacal dust, the Keck Interferometer Nuller, which completed its observations of exo-zodiacal dust in 2011. To learn more about the Keck Interferometer, visit science.nasa.gov/missions/keck.
The LBT is an international collaboration among institutions in the U.S., Italy and Germany, and it is managed and headquartered at the UA. | 0.899826 | 4.006567 |
The Mercury Atmosphere and Surface Composition Spectrometer (MASCS) instrument aboard NASA's MESSENGER spacecraft was designed to study both the exosphere and surface of the planet Mercury. To learn more about the minerals and surface processes on Mercury, the Visual and Infrared Spectrometer (VIRS) portion of MASCS has been diligently collecting single tracks of spectral surface measurements since MESSENGER entered Mercury orbit on March 17, 2011. The track coverage is now extensive enough that the spectral properties of both broad terrains and small, distinct features such as pyroclastic vents and fresh craters can be studied. To accentuate the geological context of the spectral measurements, the MASCS data have been overlain on the monochrome mosiac from the Mercury Dual Imaging System (MDIS), an instrument with wide- and narrow-angle cameras to map the rugged landforms and spectral variations on Mercury’s surface.
The MESSENGER spacecraft is the first ever to orbit the planet Mercury, and the spacecraft's seven scientific instruments and radio science investigation are unraveling the history and evolution of the solar system's innermost planet. In the mission's more than four years of orbital operations, MESSENGER has acquired over 250,000 images and extensive other data sets. MESSENGER's highly successful orbital mission is about to come to an end, as the spacecraft runs out of propellant and the force of solar gravity causes it to impact the surface of Mercury near the end of April 2015.
Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington | 0.825481 | 3.28003 |
How good are your optics? Nothing can challenge the resolution of a large light bucket telescope, like attempting to split close double stars. This week, we’d like to highlight a curious triple star system that presents a supreme challenge over the next few years and will ‘keep on giving’ for decades to come.
The star system in question is 44 Boötis, in the umlaut-adorned constellation of Boötes the herdsman. Boötes is still riding high to the west at dusk for northern hemisphere observers in late August, providing observers a chance to split the pair during prime-time viewing hours.
Sometimes also referred to as Iota Boötis, William Herschel first measured the angular separation of the pair in 1781, and F.G.W. Struve discovered the binary nature of 44 Boötis in 1832. Back then, the pair was headed towards a maximum apparent separation of 5 arc seconds in 1870. We call this point apastron. A fast forward to 2015 sees the situation reversed, as the pair currently sits about an arc second apart, and closing. 44 Boötis will pass a periastron of just 0.23” from the primary in 2020. Can you split the pair now? How ‘bout in 2016 onward? Can you recover the split, post 2020?
The physical parameters of the system are amazing. About 42 light years distant, 44 Boötis A is 1.05 times as massive as our Sun, and shines at magnitude +4.8. The B component is in a 210 year elliptical orbit with a semi-major axis of 49 AUs (for comparison, Pluto at aphelion is 49 AUs from the Sun), and is itself a curious contact spectroscopic binary about one magnitude fainter. Though you won’t be able to split the B-C pair with a backyard telescope, they betray their presence to professional instruments due to their intertwined spectra. 44 Boötis B and C have a combined mass of 1.5 times that of our Sun, and orbit each other once every 6.4 hours at a center-to-center distance of only 750,000 miles, or only 3 times the distance from Earth to the Moon:
That’s close enough that the pair shares a merging atmosphere. It’s a mystery as to just how these types of contact binary stars form, and it would be fascinating to see 44 Boötis up close. This fast spin along our line of sight also means that 44 Boötis B-C varies in brightness by about half a magnitude over a six hour span.
Though the visual 44 Boötis A-B pair doesn’t quite have an orbital period that the average humanoid could expect to live through, beginning amateur astronomers can watch as the pair once again heads towards a wide an easy 5” split during apastron around 2080.
Collimation, or the near-perfect alignment of optics, is key to the splitting close binaries, and also serves as a good test of a telescope and the stability of the atmosphere. A well-collimated scope will display stars with sharp round Airy disks, looking like luminescent circular ripples in a pond. We call the lower boundary to splitting double stars the Dawes Limit, and on most nights, atmospheric seeing will limit this to about an arc second.
But there’s another method that you can use to ‘split’ doubles closer than an arc second, known as interferometry. This relies on observing the star by use of a filtering mask with two slits that vary in distance across the aperture of the scope. When the mask is rotated to the appropriate position angle and the slits are adjusted properly, the ‘fringes’ of the star snap into focus. A formula utilizing the slit separation can then calculate the separation of the close binary pair. This method works with stars that are A). Closer than 1” separation, and B). Vary by not more than a magnitude in brightness difference.
44 Boötis near periastron definitely qualifies. As of this writing, our ‘cardboard interferometer’ is still very much a work in progress. We could envision a more complex version of this rig mechanized, complete with video analysis. Hey, if nothing else, it really draws stares from fellow amateur astronomers…
We promise to delve into the exciting realm of backyard cardboard interferometry once we’ve worked all of the bugs out. In the meantime, be sure to regale us with your tales of tragedy and triumph observing 44 Boötis. Revisiting double stars can pose a life-long pursuit!
– Be sure to check out another double star challenge from Universe Today, with the hunt for Sirius B. | 0.870544 | 3.772127 |
5:15 PM - 6:30 PM
[PPS11-P05] JUICE/GALA-J (2): Science objectives of the GAnymede Laser Altimeter (GALA) for the JUICE mission
Jovian icy moon Ganymede, which is the largest moon in the Solar System and the primary target of the JUICE, can be said to be one of the typical solid bodies along with terrestrial planets in terms of its size and the intrinsic magnetic field originated from the metallic core. However, current knowledge provided by previous explorations is extremely limited since it comes from only several fly-bys. The JUICE will uncover the whole picture of Ganymede by the first “orbiting” in the history around extra-terrestrial moon. Expected new big picture of the origin and evolution of Ganymede will not only be a key to unveil the origin of diversity among the Solar System bodies, but also contribute to understand exoplanets with a wide diversity.
The GALA will measure a distance between the spacecraft and the surface of icy moons and acquire the topography data (globally for Ganymede, and fly-by region for Europa and Callisto). It will be a first-ever laser altimetry for the icy object. Such information makes surface geologies clear and tremendously improves our understanding of the icy tectonics. By comparing their tectonic styles on the rocky planets/moons, GALA data leads to reconsider the Earth’s plate tectonics. In addition, the GALA will confirm a presence/absence of the subsurface ocean by measuring tidal and rotational response, and also the gravitational information reflecting the interior structure will be greatly improved. In addition, strength and waveform of laser pulse reflected from the moon’s surface have information about surface reflectance at the laser wavelength and small scale roughness, and therefore we can see degrees of erosion and space weathering without being affected by illumination condition through GALA measurements.
In order to interpret and understand such measurements, accumulated studies for the Earth over the years will be effectively utilized: e.g., the data for surface topography, roughness and albedo will lead to describe the icy tectonics through the knowledge from terrestrial glaciology and experiments on impact and deformation process. The tidal measurements by GALA will also be a window to see its interior based on our knowledge and experiences cultivated through the past geodetic observations, e.g., the SELENE mission for the terrestrial Moon.
Characterization of the icy moons will be achieved not only from the GALA measurements but also synergy of other scientific instruments onboard JUICE spacecraft, for examples, surface images taken by optical camera (JANUS) will confirm the position of GALA laser footprint to complement the GALA “point” data for precise topographic mapping. A radar sounder (RIME) and a radio science experiment (3GM) probe the interior structure, especially interior of the icy crust to figure out an occurrence of tectonic features. A visible and infrared imaging spectrometer (MAJIS), an ultraviolet imaging spectrograph (UVS) and a sub-millimeter wave instrument (SWI) will acquire a surface and atmosphere compositional data. A magnetometer (J-MAG) monitors moons’ inductive response to the Jovian magnetic field and probes the subsurface ocean with the help of a particle environment package (PEP) and a radio and plasma wave investigation (RPWI). The GALA works closely together with these instruments and plays a leading and a supporting role to clarify the whole picture of Ganymede and other icy moons. | 0.863101 | 3.91268 |
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confusion. In the larger, he found 582 single stars, 46 clusters, and 291 nebulae.
The Milky "way —Via Lactea or Galaxy, as it is variously termed—is that luminous, cloud-like band that stretches across the heavens in a great circle. It is inclined to the celestial equator about 63°, and intersects it in the constellations Cetus and Virgo. This stream of suns is divided into two branches from a Centauri to Cygnus. To the naked eye it presents merely a diffused light; but with a powerful telescope it is found to consist of myriads of stars densely crowded together. These stars are not uniformly distributed through its entire extent. In some regions, within the space of a single square degree we can discern as many as can be seen with the naked eye in the entire heavens. In other parts there are broad open spaces. A remarkable instance of this occurs near the Southern Cross. There is a dark pear-shaped vacancy with a single bright star at the centre, glittering on the blue background of the sky. In viewing it, one is said to be impressed with the idea that he is looking through an opening into the starless depths beyond the Milky Way.
The number of stars in the galaxy which may be seen by Herschel's great reflector is estimated at twenty-one and a half millions. With the more powerful instruments now being made it is probable the number will be largely increased. The northern galactic pole is situated near Coma Berenices, and the southern in Cetus. Advancing from either pole toward the Milky Way, the number of stars increases, at first slowly and then more rapidly, until the proportion at the galaxy itself is thirty-fold.
HerscJid's theory.—Sir W. Herschel has conjectured that the stars are not indifferently scattered through space, but are collected in a stratum something like that shown in the cut, and that our sun
occupies a place at S, near where the stream branches. A and E are the galactic poles. It is evident that, to an eye viewing the stratum of stars in the direction SB, SC, or SD, they would seem much denser than in the direction SA or SE. Thus are we to think of our own sun as a star of the second or third magnitude, and our little solar system as plunged far into the midst of this vortex of worlds, a mere atom along that
"Broad and ample road Whose dust is gold and parement stars."
Nebular Hypothesis.—This is a theory which was advanced by Laplace, to show how the solar system was formed. In the "beginning," all the matter which now composes the sun and the various planets, with their moons, was in a gaseous and highly heated state. It filled all the space now occupied by the system, and extended far beyond the orbit of Neptune. In other words, the solar system was simply an immense nebula. The heat, which is the repellant force, overcame the attraction of gravitation. Gradually the mass cooled by radiation. As centuries passed, the repellent force becoming weaker, the attractive force drew the matter and condensed it toward one or more centres. The nebula then presented the appearance of a nebulous star—a nucleus enveloped to a great distance by a gaseous atmosphere. According to a well-known law in philosophy, seen in every-day life, in a whirlpool, a whirlwind, or even in water poured into a funnel, wherever matter seeks a centre, a rotary motion is established. As this rotary motion increased, the centrifugal force finally overcame at the exterior the attraction of gravitation, and so threw off a ring of condensed vapor. Centuries elapsed, and again, under the same conditions, a second ring was detached. Thus, one by one, concentric rings were separated from the parent nebula, all revolving in the same plane and in the same direction. These different rings, becoming gradually consolidated, formed the planets,—generally however, in this process, while still in the vaporous state and slowly condensing, themselves throwing off rings which were in turn consolidated into satellites. In the case of Saturn, several of these secondary rings did not break up, and so condense into globes, but still remain as rings which revolve about the planet.* Mitchell naively remarks, "Saturn's rings were left unfinished to show us how the world was made." The ring which formed the minor planets broke up into small fragments, none large enough to attract the rest and thus form a single globe. The central mass of vapor finally condensed itself into the sun, which remains the largest member of the system. According to this theory, the sun may yet give off a few more planets, whose orbits will not exceed its present diameter. After a time its heat will have all been radiated into space, its fire will become extinct, and life on the planets will cease. "We know not when this remote event may occur. We cannot fathom the purpose of God in creating and maintaining this system of worlds, nor foretell how soon it may complete its mission. We are assured, however,
"That nothing walks with aimless feet,
* It is possible that these rings may yet break up and form new satellites for that planet. Indeed, some hold that one at least of the rings has thus been resolved into small meteorites. These may be attracted, and so picked up, one by one, by the larger in succession, until they form another moon, which will continue to revolve about the planet as the ring does now.
Spectrum Analysis.—The rainbow—that child of the sun and shower—is familiar to all. The brilliant band of colors, seen when the sunbeam is passed through a prism, is scarcely less beautiful. The ray of light containing the primary colors is spread out fan-like, and each tint reveals itself. This variously colored band is called in philosophy a spectrum (plural, spectra). There are three different kinds of spectra—
1st. When the light of a solid or liquid body, as | 0.906329 | 3.638269 |
Nearly all Martian meteorites found on Earth may come from the same crater on Mars. If so, the claim could overturn our understanding of Martian history, because most pieces of the Red Planet we are able to study in detail would be billions of years older than believed. But the idea has set off a firestorm among meteorite experts, with some unconvinced that the rocks share a common origin.
There are nearly 150 known meteorites from Mars, about 80 per cent of which are in a group called the shergottites, thought to be pieces of the planet’s crust formed from cooling lava. Looking at the way minerals melted and reformed in these rocks, previous studies suggested that shergottites were 600 million years old at most.
But Stephanie Werner at the University of Oslo in Norway and her colleagues believe that the rocks are older because they have all come from the same place: the 55-kilometre-wide Mojave crater on Mars, which was carved out of terrain that is 4.3 billion years old.
To date features on other planets, astronomers use a technique called crater counting, which is based on the rate at which craters of different sizes should accumulate on a planet’s surface. Using this method, Werner’s team calculated that the impact that formed Mojave crater happened around 3 million years ago. That is a puzzle – statistical models suggest such large craters should not have formed so recently in Martian history.
Big baby crater
“These kinds of craters don’t form on Mars any more, so it was very surprising that we found this big, very young crater,” says Werner.
The team turned to the shergottite meteorites. When planetary material is launched into space during an impact, it gets exposed to cosmic rays, and these high-energy particles can alter the rock’s chemical signatures. Based on their cosmic ray exposure, the shergottites must have broken off Mars between 1 and 5 million years ago, putting them in line with the age of Mojave crater.
“That was the strongest hint that these very recently ejected meteorites from Mars could be closely linked to this impact crater,” says Werner. Also, mineral maps from two spacecraft in orbit around Mars show that the rocks in the walls and central region of Mojave crater have similar ingredients to many shergottites.
But if the shergottites are from Mojave, the rocks should be as ancient as the rest of the crater, and certainly not as young as the 600 million years suggested by examining their form. This can be explained by recent measurements of isotopes in the meteorites, says Werner.
Previous work studying ratios of different kinds of lead in shergottites suggested that the rocks are, in fact, between 4.1 and 4.3 billion years old. That would fit with the age of the terrain in Mojave crater, Werner’s team says. With these revised ages, Werner thinks that the famous Allan Hills meteorite, which is 4.1 billion years old and was once claimed to contain fossilised microbes, may have also been sent to Earth by the Mojave impact.
“This is a fantastic study,” says Audrey Bouvier at the University of Western Ontario, Canada, who studies meteorite isotopes. “I have been fighting this idea of young shergottites for a long time now, because people did not measure the composition carefully enough in the 1980s.”
Harry McSween at the University of Tennessee in Knoxville previously worked with Werner on dating Mojave crater. However, he thinks the team has not made a strong enough case for this location being the source of all shergottites. Groups of these meteorites have different cosmic ray ages and mineral properties, which suggest they came from different craters, he says. “These are separate impact events on Mars that launched each of these homogenous groups of meteorites.”
Both Werner and Bouvier counter that the crater is big enough to account for a variety of rock types. And they think cosmic-ray ages can be unreliable because meteors fragment as they travel through space, exposing fresh surfaces to cosmic bombardment.
“It is a model that can be challenged,” says Kurt Marti at the University of California, San Diego. “There are a number of ad hoc assumptions, like a break-up in space to account for cosmic ray ages, without current experimental support.”
Journal reference: Science, DOI: 10.1126/science.1247282
More on these topics: | 0.858563 | 4.029696 |
Who are we to question Einstein on the accuracy of his relativity theory right? We shouldn’t, but we should! OK, that doesn’t make sense at all. I know right? What I meant was that thanks to Einstein, we have been using his e = mc^2 theory to form so many modern marvels. Some marvels though should never have existed such as nuclear weapon for obvious reasons. Then comes the part where I said we should question Einstein e=mc^2 theory even though the majority of us will never be able to achieve what Einstein had achieved. Why should we question his theory? Well, imagine what if Einstein is wrong about nothing can travel faster than light as how Mr. Michio Kaku phrased in the video which I will post near the end of this blog post, we will be able to travel faster than light (according to Mr. Michio Kaku). I sure like the sound of travel faster than light, because Mr. Michio Kaku mentioned in the video that time travel would be possible if light’s constant speed could be beat.
Personally, without anything to backup my belief, I think nothing is finite and nothing is infinite. You can say this is a philosophical thought, because it’s really contradictory in a sense. OK, perhaps philosophical thought doesn’t have to be contradictory, but for me and in this case it is. For one thing we know for sure, we don’t know if the speed of light is the ultimate speed of the universe even though Einstein said it is. How come? Remember how Einstein was a nobody who came along and changed how we would think about sir Isaac Newton’s gravity theory altogether? Because of Einstein, we came to understand that Newton’s gravity way of thinking could be off if gravity is to be calculated at extreme levels (i.e., super large or super small sizes such as black hole or quantum mechanical elements). Nowadays, we can use Newton’s gravity way of calculation for things that aren’t as grand as black hole and so on — and things won’t be off too much. When we need a much fine tune calculation on all gravitational concerns, we have to use Einstein’s relativity theory as many in the past and now have agreed that Einstein’s relativity theory is more suitable for much more accurate gravitational calculations (i.e., for things at extreme scales). So in a sense, we might not know that in the future there will be a genius in the making which will prove Einstein wrong, right? Of course, such a genius won’t be me and you. It ain’t that easy to have a genius at Einstein caliber to come along, really!
I guess, the point I’m making is that when we thought the earth was flat, it became round. When we thought the earth was the center of everything, then came the sun said no it’s not “How dare you be so wrong earth?” When the thought of the sun is at the center of a solar system wasn’t enough, we amazed at the scale of our galaxy. Who would have thought that we could not count all the galaxies there ever were and are in space? To think there would also be unimaginable amount of stars and space whatever within each galaxy alone… mind explosion! With every twist and turn, we had it wrong. How could we have not think of what if our universe has had an edge, and beyond this edge would lie a much bigger universe that would encompass the one we are in for an eternity to come unless… Imagine a russian nested doll which would not end (i.e., there would always be another layer of dolls). So, I think we should question Einstein often even if Einstein is currently correct! By questioning Einstein often, we open up a hope that one day we might be able to travel faster than light and achieve time travel. For what purposes do we need faster than light speed and time travel? I would leave that for you to decide. Check out “Michio Kaku: What if Einstein Is Wrong?” video right after the break. Enjoy!!!
- In Einstein’s Math: Faster-Than-Light Travel? (news.discovery.com)
- Faster-Than-Light Travel May Be Possible [Science] (gizmodo.com)
- Einstein’s math suggests faster-than-light travel (msnbc.msn.com)
- Faster-Than-Light Travel May Be Possible (gizmodo.co.uk)
- Einstein’s Special Theory of Relativity Get Warp Speed Extension (dailytech.com)
- Hidden in Einstein’s Math: Faster-than-Light Travel? (livescience.com)
- Extending Einstein’s theory beyond light speed (rdmag.com)
- Einstein’s math may also describe faster-than-light velocities – Christian Science Monitor (csmonitor.com)
- Extending Einstein’s theory beyond light speed (esciencenews.com)
- Faster-than-Light Travel? (phys.org) | 0.805736 | 3.150484 |
Microbes could survive thin air of Mars
Microbes that rank among the simplest and most ancient organisms on Earth could survive the extremely thin air of Mars, a new study finds.
The Martian surface is presently cold and dry, but there is plenty of evidence suggesting that rivers, lakes and seas covered the Red Planet billions of years ago. Since there is life virtually wherever there is liquid water on Earth, scientists have suggested that life might have evolved on Mars when it was wet, and life could be there even now.
"In all the environments we find here on Earth, there is some sort of microorganism in almost all of them," said Rebecca Mickol, an astrobiologist at the Arkansas Center for Space and Planetary Sciences at the University of Arkansas in Fayetteville, and the lead author of the study. "It's hard to believe there aren't other organisms out there on other planets or moons as well."
Mickol and her team detailed their findings in the paper, "Low Pressure Tolerance by Methanogens in an Aqueous Environment: Implications for Subsurface Life on Mars," which was published in the journal Origins of Life and Evolution of Biospheres.
Previous research detected methane, the simplest organic molecule, in the Martian atmosphere. While there are abiotic ways to produce methane—such as volcanic activity—much of this colorless, odorless, flammable gas in Earth's atmosphere is produced by life, such as cattle digesting food.
"One of the exciting moments for me was the detection of methane in the Martian atmosphere," Mickol said. "On Earth, most methane is produced biologically by past or present organisms. The same could possibly be true for Mars. Of course, there are a lot of possible alternatives to the methane on Mars and it is still considered controversial. But that just adds to the excitement."
On Earth, microbes known as methanogens produce methane, also known as natural gas. Methanogens typically live in swamps and marshes, but can also be found in the guts of cattle, termites and other herbivores, as well as in dead and decaying organic matter.
Methanogens are among the simplest and most ancient organisms on Earth. These microorganisms are anaerobes, meaning they do not require oxygen. Instead, they often rely on hydrogen for energy, and carbon dioxide is the main source of carbon atoms they use in creating organic molecules.
The fact that methanogens neither require oxygen nor photosynthesis means they could live just beneath the Martian surface, shielded from harsh levels of ultraviolet radiation on the Red Planet. This could make them ideal candidates for life on Mars.
However, the area just below the surface of Mars is exposed to extremely low atmospheric pressures, normally considered inhospitable to life. The surface pressure on Mars on average ranges from one-hundredth to one-thousandth that of the surface pressure of Earth over the course of the Martian year, too low for liquid water to last on the surface. In such thin air, water easily boils. (In contrast, the pressure at the highest point on Earth's surface, the top of Mount Everest, is about one-third that of Earth's surface pressure at sea level.)
To see if methanogens might survive such extremely thin air, Mickol and Timothy Kral, the senior author of the study and an astrobiologist at the University of Arkansas at Fayetteville, experimented with four species of methanogens. They included: Methanothermobacter wolfeii, Methanosarcina barkeri, Methanobacterium formicicum, and Methanococcus maripaludis. Previous experiments on these four species over the course of more than 20 years generated a lot of data on these organisms and their rates of survival in simulated Martian conditions.
The more recent set of experiments, which took about a year, involved growing the microbes in test tubes within liquids as a proxy for the fluids potentially flowing through underground Martian aquifers. The microbes were fed hydrogen gas, and the liquids were covered with cotton swabs, which in turn were covered with dirt simulating what might be found on the Martian surface. The insides of each test tube were then subjected to low pressures.
Oxygen kills these methanogens, and maintaining a low-pressure, oxygen-free environment "was a difficult task," Mickol said. Moreover, water evaporates quickly at low pressure, which can limit how long the experiments can last and can also clog the vacuum system with water.
Despite these problems, the researchers found that these methanogens all survived exposure of lengths varying from 3 to 21 days at pressures down to roughly six-thousandths of Earth's surface pressure. "These experiments show that for some species, low pressure may not really have any effect on the survival of the organism," Mickol said.
"The next step is to also include temperature," Mickol said. "Mars is very, very cold, often getting down to -100ºC (-212ºF) at night, and sometimes, on the warmest day of the year, at noon, the temperature can rise above freezing. We'd run our experiments just above freezing, but the cold temperature would limit evaporation of the liquid media and it would create a more Mars-like environment."
Mickol stressed that these experiments do not prove life exists on other planets. "That being said, with the abundance of life on Earth, in all the different extremes of environments found here, it's quite possible there exists life—bacteria or tiny microorganisms—somewhere else in the Universe," she said. "We're just trying to explore that idea."
This story is republished courtesy of NASA's Astrobiology Magazine. Explore the Earth and beyond at www.astrobio.net . | 0.828721 | 3.811374 |
Seven planets, with mass similar to the Earth and orbiting around a dwarf star the size of Jupiter, just 39 light years from the Sun, have been spotted by scientists. The planets’ temperatures are low enough to make possible the presence of liquid water on their surface.
In May last, the scientists found three planets passing in front of star TRAPPIST-1. On further monitoring of the star from the ground and space, they found four more exoplanets orbiting it.
The results are being published on February 23 in Nature. Michaël Gillon from the Université de Liège, Belgium, is the first author of the paper.
In habitable zone of star
“This is the first time we have so many Earthlike planets found around a star. The star is low-mass and small,” Dr. Gillon said at a press briefing. “The seven planets could have some liquid water and maybe life. They are found in the habitable zone of the star. This is the first time we have found so many planets in the habitable zone of a star.”
The scientists have been able to make precise mass measurement of six of the seven planets. Though this is preliminary, they do indicate that the planets are terrestrial with liquid water. “The seven planets are suitable for detailed atmospheric study,” said Dr. Gillon. “The architecture suggests that they formed farther from the star and migrated towards it.”
“We can study the climate and chemical composition of the planets’ atmosphere,” Dr. Amaury H.M.J. Triaud from the Institute of Astronomy, Cambridge, who is one of the authors of the paper, said at the press briefing.
“We are first trying to rule out the presence of large hydrogen envelope to make sure that the planets are indeed Earthlike. This will be followed by a detailed study of climate and chemical composition to try and find out if there is life on these planets. If there is life on these planets we will know it in a decade,” he said.
The four newly discovered planets orbit around the star every 4.04 days, 6.06 days, 8.1 days and 12.3 days respectively; the orbital period of two of the three planets discovered last year are 1.51 days and 2.42 days respectively.
Five planets have sizes similar to that of the Earth, while the remaining two are intermediate in size — between the Mars and the Earth. Based on the mass estimates, the six inner planets may have a rocky composition. The sixth planet has low density, suggesting a volatile rich composition. The volatile content could be either ice layer and/or atmosphere.
Courtesy: The Hindu | 0.830367 | 3.709662 |
One of the great questions for science and humanity is: Are we the only solar system with planets, and the only one with planets that could support life? The discovery of planets around other stars makes it likely that other planets exist capable of supporting life.
Of great importance to astronomers, the discovery of other solar systems lets them test their theories on the origin of planets and solar systems. The discovery of distant planets has fundamentally changed how we perceive our place in the universe.
In the sixth century B.C., Greek scientist Anaximander was the first to theorize that other planets must exist. In 1600 Italian priest and astronomer Giordano Bruno was burned at the stake by the Catholic Church for professing the same belief. American astronomers were actively searching through giant telescopes for planets orbiting other stars by late the 1940s.
Michel Mayor was born in 1942 and even as a child was fascinated by stars and astronomy. With his collaborator, Antoine Duquennoy, he joined the many astronomers searching for small objects in the universe. But Mayor searched not for planets, but for brown dwarfs—cool, dim objects thought to form like stars, but which failed to grow massive enough to support hydrogen fusion and thus never lit up with starry furnace and fire. Too big for planets, too small to become stars, brown dwarfs were a galactic oddity.
Astronomers, however, had a problem: telescopes can’t see planets and brown dwarfs because they don’t give off light. Instead, astronomers searched for slight side-to-side wobbles in the motion of a star caused by the gravitational tug of a large planet (or brown dwarf).
Some tried to detect such wobble by carefully measuring the position of a star over the course of months or years. Others (Mayor included) looked for this wobble by using Doppler shift and measuring tiny shifts on a spectrograph in the color of the light coming from a star that would be the result of changes in the star’s motion toward or away from Earth.
Following the death of Duquennoy in 1993, Mayor teamed with graduate student Didier Queloz and developed a new, more sensitive spectrograph to search for brown dwarfs. Their new spectrograph was capable of measuring velocity changes as small as 13 meters per second, about the same as the wobble in our sun’s motion caused by Jupiter’s gravitational tug.
But everyone assumed that such massive planets would take years to orbit a star (as they do in our system). Thus the wobble from a planet’s tug would take years of data to notice. It never occurred to Mayor to use his new spectrograph and a few months’ worth of time on a telescope to search for a planet.
Beginning in April 1994, using the Haute-Provence Observatory in southern France, Mayor and Queloz tested their new spectrograph on 142 nearby stars, hoping to detect a wobble that would indicate a massive nearby object like a brown dwarf. In January 1995 one star, 51 Peg (the fifty-first brightest star in the constellation Pegasus) caught Queloz’s eye. It wobbled. It wobbled back and forth every 4.2 days.
They tested the star’s light to make sure it didn’t pulse. They tested to see if sun spots might create an apparent wobble. The tested to see if 51 Peg puffed up and contracted to create the appearance of wobble. Nothing could account for 51 Peg’s wobble except for a sizable orbiting object.
From the amount of 51 Peg’s wobble they calculated the mass of the object and knew it was too small to be a brown dwarf. It had to be a planet! They had discovered a planet outside our solar system.
By 2005, several hundred other planets had been located—gas giants speeding around Mercury-sized orbits; some rocky planets in cozy, not-too-hot-and-not-too-cold orbits; even some drifting free through space without a star to circle. Earth is certainly not alone. Mayor and Queloz were the first to discover proof of this spectacular reality.
If only one star in ten has planets (and current knowledge indicates that at least that many do), if the average star with planets has at least three, and if only one in every hundred are rocky planets in life-sustaining orbits (and recent discoveries indicate that to be the case), then there are at least 300,000 planets capable of supporting life in our galaxy alone. | 0.916827 | 3.85747 |
Iskopah ovo. Interesantan tekstic. Uzet sa http://www.astronomycafe.net/qadir/q1168.html
Mrzelo me da prevodim:
What would happen if the Earth stopped spinning?
The probability for such an event is practically zero in the next few billion years. If the Earth stopped spinning suddenly, the atmosphere would still be in motion with the Earth's original 1100 mile per hour rotation speed at the equator. All of the land masses would be scoured clean of anything not attached to bedrock. This means rocks, topsoil, trees, buildings, your pet dog, and so on, would be swept away into the atmosphere.
If the process happened gradually over billions of years, the situation would be very different, and it is this possibility which is the most likely as the constant torquing of the Sun and Moon upon the Earth finally reaches it's conclusion. If the rotation period slowed to 1 rotation every 365 days a condition called 'sun synchronous', every spot in the Earth would have permanent daytime or nighttime all year long. This is similar to the situation on the Moon where for 2 weeks the front-side is illuminated by the Sun, and for 2 weeks the back side is illuminated. This situation for the Earth is not the condition of 'stopped' rotation, but it is as close as the laws of physics will let the Earth get.
If it stopped spinning completely...not even once every 365 days, you would get 1/2 year daylight and 1/2 year nightime. During daytime for 6 months, the surface temperature would depend on your latitude, being far hotter that it is now at the equator than at the poles where the light rays are more slanted and heating efficiency is lower. This long-term temperature gradient would alter the atmospheric wind circulation pattern so that the air would move from the equator to the poles rather than in wind systems parallel to the equator like they are now. The yearly change in the Sun's position in the sky would now be just its seasonal motion up and down the sky towards the south due to the orbit of the Earth and its axial tilt. As you moved along constant lines of Earth latitude, you would see the elevation of the Sun increase or decrease in the sky just as we now see the elevation of the Sun change from a single point on the Earth due to the Earth's daily rotation.
For example, if you were at a latitude of +24 degrees North in the Summer and at a longitude where the Sun was exactly overhead, it would slide gradually to the horizon as Fall approached, but since the Sun has moved 90 degrees in its orbit, it would now be due west. Then as we approach Winter, you would now be located on the dark side of the Earth, and would have to travel in longitude to a location 180 degrees around the Earth to see the Sun 1/2 way up the sky because in the Winter, the Sun is 48 degrees south of its summer location in the sky. It's a little confusing, but if you use a globe of the Earth and orient it the right way, you can see how all this works out.
As for other effects, presumably the magnetic field of the Earth is generated by a dynamo effect that involves its rotation. If the Earth stopped rotating, it's magnetic field would no longer be regenerated and it would decay away to some low, residual value due to the very small component which is 'fossilized' in its iron-rich rocks. There would be no more 'northern lights' and the Van Allen radiation belts would probably vanish, as would our protection from cosmic rays and other high-energy particles. This is a significant biohazard.
Ako sam dobro razumela, momentalnim prestankom rotacije Zemlje, Zemljina atmosfera bi se kretala josh neko vreme, shto bi za posledicu imalo "usisavanje" svega shto nije vezano za tlo u istu. | 0.836708 | 3.040066 |
Navigating the cosmos is becoming a reality.
For centuries, it has been a dream: to travel through space driven solely by the solar wind. It was first imagined in 1600 by Johannes Kepler, the German astronomer. Centuries later, Arthur C. Clarke moved him to the realm of science fiction in "Sunjammer," a short story from 1964. Carl Sagan, the cosmologist and co-founder of the Planetary Society, thought it could be more than a speculative fantasy, and It began in the 1970s to promote the construction of solar sails for space exploration.
On Tuesday, solar navigation could take its next big step to become a proven technique for navigating the gaps between worlds.
Last month, the spacecraft of the Planetary Society, LightSail 2, traveled to space aboard a SpaceX Falcon Heavy rocket. After 10 years of planning and more than 40,000 private donations worth $ 7 million, the cube has reached a high enough orbit around the Earth and some technical problems have been solved by engineers on Earth. With the press of a button on the ground in California on Tuesday morning, mission controllers expect spacecraft sails to unfold, opening the curtain at the next act of spaceflight.
What is solar navigation?
A limitation of space travel is that energy sources eventually run out.
But the sun is a constant source of energy. It is always releasing photons into space. While these particles have no mbad, they have momentum. Solar navigation is based on the always gentle thrust of photons to push a candle forward, moving what is behind the candle in another direction.
Navigation could be one of the most efficient options in fuel consumption for space travel. While the force exerted on a solar sail is approximately the same as can be felt by the weight of a piece of paper in the palm of your hand, the momentum is able to accumulate, increasing the speed of the candle over time.
For example, NASA's Voyager twin spacecraft, which was flying with pure momentum because they ran out of fuel, needed more than 40 years from launch to reach the limits of our solar system. But if they had solar candles, the duration of their trips could have been reduced by almost half.
How will LightSail 2 work?
LightSail 2 aims to become the first adjustable solar sail launched in orbit around the Earth. It is a cube the size of a bar that carries a solar candle the size of a boxing ring. Made of a fine mylar material, these candles are designed to bloom as a space lotus and collect energy from the sun.
The cubesat has an impulse wheel, which allows the engineering team of the Planetary Society on Earth to guide its mylar sails. That will keep the spacecraft at a 90 degree angle to the sun at all times, not like the way a sailboat needs to turn towards the wind to move.
As LightSail orbits the Earth, ground engineers will attempt to extend the farthest point of its orbit, called apogee. To do this, the sail must get enough sun thrust and also rely on the direction from the ground.
"If everything goes perfectly, we should be able to raise the apogee by approximately 1,640 feet per day," says Dave Spencer, professor of aeronautics at Purdue University in West Lafayette, Indiana, and LightSail mission manager.
What will happen during deployment?
Tuesday at 11:40 a.m. in California, 2:40 p.m. Eastern Time, California engineers will send an order to orbit, and in about two minutes, LightSail 2 will deploy its sails.
During deployment, two wide-angle cameras in the cube will capture 32 images. "It will effectively give us a kind of movie of the candle display," said Dr. Spencer.
The main mission is to last about a month, and after that LightSail could orbit the Earth for a year. Sometimes it will be visible from Earth to the naked eye, and the Planetary Society will provide updates on where it can be seen.
Eventually, Earth's gravitational attraction will drag the cubes into the atmosphere, where it will burn.
Has this been tried before?
LightSail 2 follows LightSail 1, released in 2015 as a test. While fulfilling some of its objectives, the test was hindered by a series of engineering problems.
The first solar sail spacecraft, Ikaros, was launched in 2010 by the Japan Aerospace Exploration Agency. Although it was not orientable, it traveled beyond Venus. It went into orbit around the sun and was last heard in 2015.
At the beginning of the next decade, NASA plans to launch NEA Scout or Near Earth Asteroid Scout. This small cube will use a solar sail to visit an asteroid near Earth to collect data and send it back to Earth. | 0.894119 | 3.658075 |
The Dark Matter Particle Explorer (DAMPE, also known as Wukong) mission published its first scientific results on Nov. 30 in Nature, presenting the precise measurement of cosmic ray electron flux, especially a spectral break at ~0.9 TeV. The data may shed light on the annihilation or decay of particle dark matter.
DAMPE is a collaboration of more than a hundred scientists, technicians and students at nine institutes in China, Switzerland and Italy, under the leadership of the Purple Mountain Observatory (PMO) of the Chinese Academy of Sciences (CAS). The DAMPE mission is funded by the strategic priority science and technology projects in space science of CAS.
DAMPE, China's first astronomical satellite, was launched from China's Jiuquan Satellite Launch Center into sun-synchronous orbit on Dec. 17th, 2015. At an altitude of about 500 km, DAMPE has been collecting data since a week after its launch.
In its first 530 days of science operation through June 8 of this year, DAMPE has detected 1.5 million cosmic ray electrons and positrons above 25 GeV. The electron and positron data are characterized by unprecedentedly high energy resolution and low particle background contamination.
Figure 1 shows the first published results in the energy range from 25 GeV to 4.6 TeV. The spectral data in the energy range of 55 GeV-2.63 TeV strongly prefer a smoothly broken power-law model to a single power-law model.
DAMPE has directly detected a spectral break at ~0.9 TeV, with the spectral index changing from ~3.1 to ~3.9. The precise measurement of the cosmic ray electron and positron spectrum, in particular the flux declination at TeV energies, considerably narrows the parameter space of models such as nearby pulsars, supernova remnants, and/or candidates for particle dark matter that were proposed to account for the "positron anomaly" revealed previously by PAMELA and AMS-02, according to FAN Yizhong, deputy chief designer of DAMPE's scientific application system.
"Together with data from the cosmic microwave background experiments, high energy gamma-ray measurements, and other astronomical telescopes, the DAMPE data may help to ultimately clarify the connection between the positron anomaly and the annihilation or decay of particle dark matter," said FAN.
Data also hint at the presence of spectral structure between 1 and 2 TeV energies - a possible result of nearby cosmic ray sources or exotic physical processes. Yet, more data are definitely required to explore this phenomenon.
DAMPE has recorded over 3.5 billion cosmic ray events, with maximum event energies exceeding ~100 trillion electronvolts (TeV). DAMPE is expected to record more than 10 billion cosmic ray events over its useful life - projected to exceed five years given the current state of its instruments.
More statistics will allow more precise measurement of the cosmic ray electron and positron spectrum up to ~10 TeV. Scientists will also be able to explore spectral features potentially generated by dark matter particle annihilation/decay or nearby astrophysical sources, e.g., pulsars.
Figure 2 compares the results of the cosmic ray electron and positron spectra from DAMPE and other experiments. The DAMPE results reported here demonstrate the unique capability of DAMPE to explore possible new physics and/or new astrophysics in the TeV energy window, thanks to its high energy resolution, large instrumental acceptance, wide energy coverage, excellent electron/proton separation power, and long working life.
DAMPE's first scientific result is a milestone for the international collaboration. The mission will continue to study galactic cosmic rays up to ~10 TeV for electrons/gamma-rays and hundreds of TeV for nuclei, respectively. DAMPE data is expected to reveal new phenomena of the universe in the TeV window. | 0.865869 | 3.985951 |
On April 10, 2019, the first ever image of a black hole was shared across the world. Through the use of the Event Horizon Telescope, which is a network of eight connected telescopes, a group of researchers from Radboud University in the Netherlands were able to publish the details of this black hole discovery in a recent Astrophysical Journal Letters article.
Image Credit: NASA
What is a Black Hole?
A black hole has been described as a region of space that, while not empty, prevents the escape of any atom or molecule from this area. Black holes are comprised of a significant amount of matter that has been densely packed into a small area. The high density of black holes accounts for their immense gravitational pull in the universe to prevent even light molecules from escaping their depths.
Challenges of Imaging Black Holes
The inability of any form of matter, such as light, to escape black holes is the primary reason that telescopes, particularly those that detect x-rays, light or other forms of electromagnetic radiation, have failed to allow scientists to observe these phenomena.
As a result, traditional interpretations of the presence and appearance of black holes are from inferences made from analyzing the effect that these objects have on nearby matter. For example, if a normal star in the galaxy passes close to a black hole, their proximity alone can cause the star to be ripped to shreds as it is pulled toward the black hole. This process can cause x-ray emission that radiates into space to provide scientists with some evidence of a neighboring black hole.
The First Black Hole Image
Located in a galaxy known as M87, which is approximately 500 million trillion kilometers (km) away from Earth, the black hole that has been featured in this revolutionary image measures at 40 billion km across with a total mass that is up to 6.5 billion times greater than that of the Sun. In this image, a vivid “ring of fire,” which is said to shine brighter than any other star in the galaxy, can be seen surrounding a circular dark hole. The bright auburn aura surrounding the black hole is the result of superheated gas that has plummeted into the black hole.
Developing the Event Horizon Telescope
With support from the European Research Council, the National Science Foundation and several other international agencies, Dr. Heino Falcke transformed his ideas from the early 1990s into reality. Dr. Falcke’s knowledge that a specific type of radio emission is generated close to and all around the black hole formed the basis of his quest to develop an extremely powerful telescope capable of visualizing these objects from Earth.
Together, with a team of Harvard researchers led by Dr. Sheperd Doeleman, the Event Horizon Telescope was created. Each of the eight telescopes that make up the Event Horizon can be found at extremely high altitudes, such as on top of mountains and volcanoes, in various countries around the world. These locations include Hawaii, Mexico, Arizona, Chile and Antarctica. In addition to the M87 black hole, this cooperative team is currently imaging a supermassive black hole located at the center of the Milky Way.
The Significance of an Image
Although the concept of a black hole may seem to simple in theory, a lot of questions remain on how these massive entities can provide information on the nature of space and time, as well as the existence of the universe. By obtaining a true image of these mysterious objects, which closely matches those originally created from theoretical calculations, researchers can begin their quest to learn exactly what happens to objects that fall into a black hole, how the ring of fire is created and much more.
- “Black Holes” – NASA Science
- “First ever black hole image released” – BBC News | 0.86868 | 4.028662 |
National Academies Call for More Astrobiology at NASA
Richard Fienberg American Astronomical Society (AAS)
This post is adapted from a press release from the National Academies:
To advance the search for life in the universe, NASA should support research on a broader range of biosignatures and environments and incorporate the field of astrobiology into all stages of future exploratory missions, says a new congressionally mandated report from the National Academies of Sciences, Engineering, and Medicine.
Astrobiology, the study of the origin, evolution, distribution, and future of life in the universe, is a rapidly changing field, especially in the years since the publication of NASA's Astrobiology Strategy 2015. Recent scientific advances in the field now provide many opportunities to strengthen the role of astrobiology in NASA missions and to increase collaboration with other scientific fields and organizations. The report finds that these changes necessitate an updated science strategy for astrobiology.
The committee that authored the report found that the lines of evidence we use to look for current and past life on Earth and beyond, called biosignatures, needs expansion. An updated, more sophisticated catalog and framework will be important to enhance our ability to detect both life that might be similar to terrestrial life, and potential life that differs from life as we know it. The latter will be enabled by investigating novel "agnostic" biosignatures — signs of life that are not tied to a particular metabolism or molecular "blueprint," or other characteristics of life as we currently know it.
A comprehensive framework could also aid in distinguishing between biosignatures and abiotic (non-living) phenomena, and improve understanding of the potential for biosignatures to be preserved (or not) over long planetary time-scales. The report highlights the need to include in situ detection of energy-starved or otherwise sparsely distributed life such as chemolithotrophic or rock-eating life. In particular, the report found that NASA should focus on research and exploration of possible life below the surface of a planet in light of recent advances that have demonstrated the breadth and diversity of life below Earth's surface, the nature of fluids beneath the surface of Mars, and the likelihood of life-sustaining geological processes in planets and moons with subsurface oceans. A renewed focus on how to seek signs of subsurface life will inform astrobiology investigations of other rocky planets or moons, ocean or icy worlds, and beyond to exoplanets.
The report emphasizes the need for NASA to ramp up efforts in developing mission-ready life detection technologies to advance the search for life. For studies of life on planets outside of this solar system, the agency should implement technologies in near-term ground- and space-based direct imaging missions that can suppress the light from stars. The specialized measurements, equipment, and analysis required to take full advantage of space missions include some that exist outside of traditional space science fields, highlighting the need for interdisciplinary, non-traditional cooperation and collaboration with organizations outside of NASA, the report says.
So far, planning, implementation, and operations of planetary exploration missions with astrobiological objectives have tended to be more strongly defined by geological perspectives than by astrobiology-focused strategies. The committee recommended the integration of astrobiology into all mission stages, from inception to development and operations. Collaboration with private, philanthropic, and international organizations, especially international space agencies, is also crucial to achieving the objectives of searching for life in the universe.
The committee also pointed out that adopting an interdisciplinary approach to astrobiology would produce a more complete picture of life on Earth as well as other planets. Integrating the physical, chemical, biological, geologic, planetary, and astrophysical sciences into the study of astrobiology will better show the relationship between life and its environment and how each changes, incorporating a new, dynamic view of habitability that includes consideration of multiple parameters. NASA should continue to actively seek new mechanisms to reduce the barriers to these potential collaborations, the report says.
The study was sponsored by NASA. The National Academies of Sciences, Engineering, and Medicine are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, technology, and medicine. They operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln. | 0.831588 | 3.350051 |
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to have divided the circle into 365 degrees. To learn the length of the year needed only patient observation — a characteristic of the Chinese; but many younger nations got into a terrible mess with their calender from ignorance of the year's length. It is stated that in 2159 B.C. the royal astronomers Hi and Ho failed to predict an eclipse. It probably created great terror, for they were executed in punishment for their neglect. If this account be true, it means that in the twentysecond century B.c. some rule for calculating eclipses was in use. Here, again, patient observation would easily lead to the detection of the eighteen-year cycle known to the Chaldaeans as the Saros. It consists of 235 lunations, and in that time the pole of the moon's orbit revolves just once round the pole of the ecliptic, and for this reason the eclipses in one cycle are repeated with very slight modification in the next cycle, and so on for many centuries. It may be that the neglect of their duties by Hi and Ho, and their punishment, influenced Chinese astronomy; or that the succeeding records have not been available to later scholars; but the fact remains that — although at long intervals observations were made of eclipses, comets, and falling stars, and of the position of the solstices, and of the obliquity of the ecliptic — records become rare, until 776 B.C., when eclipses began to be recorded once more with some approach to continuity. Shortly afterwards notices of comets were added. Biot gave a list of these, and Mr. John Williams, in 1871, published Observations of Comets from 61 I B.c. to 1640 A.D., Extracted from the Chinese Annals. With regard to those centuries concerning which we have no astronomical Chinese records it is fair to state that it is recorded that some centuries before the Christian era, in the reign of Tsin-Chi-Hoang, all the classical and scientific books that could be found were ordered to be destroyed. If true, our loss therefrom is as great as from the burning of the Alexandrian library by the Caliph Omar. He burnt all the books because he held that they must be either consistent or inconsistent with the Koran, and in the one case they were superfluous, in the other case objectionable. Chaldaeans. – Until the last half century historians were accustomed to look back upon the Greeks, who led the world from the fifth to the third century B.C., as the pioneers of art, literature, and science. But the excavations and researches of later years make us more ready to grant that in science as in art the Greeks only developed what they derived from the Egyptians, Babylonians, and Assyrians. The Greek historians said as much, in fact; and modern commentators used to attribute the assertion to undue modesty. Since, however, the records of the libraries have been unearthed it has been recognised that the Babylonians were in no way inferior in the matter of original scientific investigation to other races of the Same era. The Chaldaeans, being the most ancient Babylonians, held the same station and dignity in the State as did the priests in Egypt, and spent all their time in the study of philosophy and astronomy, and the arts of divination and astrology. They held that the world of which we have a conception is an eternal world without any beginning or ending, in which all things are ordered by rules supported by a divine providence, and that the heavenly bodies do not move by chance, nor by their own will, but by the determinate will and appointment of the gods. They recorded these movements, but mainly in the hope of tracing the will of the gods in mundane affairs. Ptolemy (about 130 A.D.) made use of Babylonian eclipses in the eighth century B.c. for improving his solar and lunar tables. Fragments of a library at Agade have been preserved at Nineveh, from which we learn that. the star-charts were even then divided into constellations, which were known by the names which they bear to this day, and that the signs of the zodiac were used for determining the
courses of the sun, moon, and of the five planets Mercury, Venus, Mars, Jupiter, and Saturn.
We have records of observations carried on under Asshurbanapal, who sent astronomers to different parts to study celestial phenomena. Here is one: —
To the Director of Observations, – My Lord, his humble servant Nabushum-iddin, Great Astronomer of Nineveh, writes thus: “May Nabu and Marduk be propitious to the Director of these Observations, my Lord. The fifteenth day we observed the Node of the moon, and the moon was eclipsed.”
The Phoenicians are supposed to have used the stars for navigation, but there are no records. The Egyptian priests tried to keep such astronomical knowledge as they possessed to themselves. It is probable that they had arbitrary rules for predicting eclipses. All that was known to the Greeks about Egyptian science is to be found in the writings of Diodorus Siculus. But confirmatory and more authentic facts have been derived from late explorations. Thus we learn from E. B. Knobel" about the Jewish calendar dates, on records of land sales in Aramaic papyri at Assuan, translated by Professor A. H. Sayce and A. E. Cowley, (1) that the lunar cycle of nineteen years was used by the Jews in the
* R. A. S. Monthly Notices, vol. 1xviii., No. 5, March, 1908.
fifth century B.c. [the present reformed Jewish calendar dating from the fourth century A.D.], a date a “little more than a century after the grandfathers and great-grandfathers of those whose business is recorded had fled into Egypt with Jeremiah '' (Sayce); and (2) that the order of intercalation at that time was not dissimilar to that in use at the present day. Then again, Knobel reminds us of “the most interesting discovery a few years ago by Father Strassmeier of a Babylonian tablet recording a partial lunar eclipse at Babylon in the seventh year of Cambyses, on the fourteenth day of the Jewish month Tammuz.” Ptolemy, in the Almagest (Suntaxis), says it occurred in the seventh year of Cambyses, on the night of the seventeenth and eighteenth of the Egyptian month Phamenoth. Pingré and Oppolzer fix the date July 16th, 533 B.C. Thus are the relations of the chronologies of Jews and Egyptians established by these explorations.
3. ANCIENT GREEK Ast RoNOMY.
We have our information about the earliest Greek astronomy from Herodotus (born 480 B.C.). He put the traditions into writing. Thales (639–546 B.C.) is said to have predicted an eclipse which caused much alarm, and ended the battle between the Medes and Lydians. Airy fixed the | 0.861182 | 3.029122 |
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Again, in 1774, the Academy submitted the same subject, a third time, for the prize; and again Lagrange failed to detect a cause in gravitation.
Laplace" now took the matter in hand. He tried the effect of a non-instantaneous action of gravity, to no purpose But in 1787 he gave the true explanation. The principal effect of the sun on the moon's orbit is to diminish the earth's influence, thus lengthening the period to a new value generally taken as constant. But Laplace's calculations showed the new value to depend upon the excentricity of the earth's orbit, which, according to theory, has a periodical variation of enormous period, and has been continually diminishing for thousands of years. Thus the solar influence has been diminishing, and the moon's mean motion increased. Laplace computed the amount at Io" in one century, agreeing with observation. (Later on Adams showed that Laplace's calculation was wrong, and that the value he found was too large; so, part of the acceleration is now attributed by some astronomers to a lengthening of the day by tidal friction.)
Another contribution by Halley to the verification of Newton's law was made when he went to St. Helena to catalogue the southern stars. He measured the change in length of the sec
ond's pendulum in different latitudes due to the changes in gravity foretold by Newton. Furthermore, he discovered the long inequality of Jupiter and Saturn, whose period is 929 years. For an investigation of this also the Academy of Sciences offered their prize. This led Euler to write a valuable essay disclosing a new method of computing perturbations, called the instantaneous ellipse with variable elements. The method was much developed by Lagrange. But again it was Laplace who solved the problem of the inequalities of Jupiter and Saturn by the theory of gravitation, reducing the errors of the tables from 20' down to 12", thus abolishing the use of empirical corrections to the planetary tables, and providing another glorious triumph for the law of gravitation. As Laplace justly said: “These inequalities appeared formerly to be inexplicable by the law of gravitation —they now form one of its most striking proofs.” Let us take one more discovery of Halley, furnishing directly a new triumph for the theory. He noticed that Newton ascribed parabolic orbits to the comets which he studied, so that they come from infinity, sweep round the sun, and go off to infinity for ever, after having been visible a few weeks or months. He collected all the reliable observations of comets he could find, to the number of twenty-four, and computed their parabolic orbits by the rules laid down by Newton. His object was to find out if any of them really travelled in elongated ellipses, practically undistinguishable, in the visible part of their paths, from parabolae, in which case they would be seen more than once. He found two old comets whose orbits, in shape and position, resembled the orbit of a comet observed by himself in 1682. Apian observed one in 1531; Kepler the other in 1607. The intervals between these appearances is seventyfive or seventy-six years. He then examined and found old records of similar appearance in 1456, 1380, and 1305. It is true, he noticed, that the intervals varied by a year and a half, and the inclination of the orbit to the ecliptic diminished with successive apparitions. But he knew from previous calculations that this might easily be due to planetary perturbations. Finally, he arrived at the conclusion that all of these comets were identical, travelling in an ellipse so elongated that the part where the comet was seen seemed to be part of a parabolic orbit. He then predicted its return at the end of 1758 or beginning of 1759, when he should be dead; but, as he said, “if it should return, according to our prediction, about the year 1758, impartial posterity will not refuse to acknowledge that this was first discovered by an Englishman.” [Synopsis Astronomiae Cometica, 1749.] Once again Halley's suggestion became an inspiration for the mathematical astronomer. Clairaut, assisted by Lalande, found that Saturn would retard the comet Ioo days, Jupiter 518 days, and predicted its return to perihelion on April 13th, 1759. In his communication to the French Academy, he said that a comet travelling into such distant regions might be exposed to the influence of forces totally unknown, and “even of some planet too far removed from the sun to be ever perceived.” The excitement of astronomers towards the end of 1758 became intense; and the honour of first catching sight of the traveller fell to an amateur in Saxony, George Palitsch, on Christmas Day, 1758. It reached perihelion on March 13th, 1759. This fact was a startling confirmation of the Newtonian theory, because it was a new kind of calculation of perturbations, and also it added a new member to the solar system, and gave a prospect of adding many more. When Halley's comet reappeared in 1835, Pontecoulant's computations for the date of perihelion passage were very exact, and afterwards * This sentence does not appear in the original he showed that, with more exact values of the masses of Jupiter and Saturn, his prediction was correct within two days, after an invisible voyage of seventy-five years!
Hind afterwards searched out many old appearances of this comet, going back to 1 I B.C., and most of these have been identified as being really Halley's comet by the calculations of Cowell and Cromellin' (of Greenwich Observatory), who have also predicted its next perihelion passage for April 8th to 16th, 19 Io, and have traced back its history still farther, to 240 B.C.
Already, in November, 1907, the Astronomer Royal was trying to catch it by the aid of photography.
9. Discovery of NEw PLANETs — HERscHEL, PIAzzi, ADAMS, AND LE VERRIER.
It would be very interesting, but quite impossible in these pages, to discuss all the exquisite researches of the mathematical astronomers, and to inspire a reverence for the names connected with these researches, which for two hundred years have been establishing the universality of Newton's law. The lunar and planetary theories, the beautiful theory of Jupiter's satellites, the figure of the earth, and the tides, were mathematically treated by Maclaurin, D'Alembert, | 0.905357 | 3.727781 |
After NASA announced in February the discovery of a solar system with seven planets—three of which were deemed potentially habitable—UChicago postdoctoral scholar Sebastiaan Krijt began wondering: If a life form existed on one of these planets, could space debris carry it to another?
In research recently published in Astrophysical Journal Letters, Krijt and fellow UChicago scientists conclude that life forms, such as bacteria or single-cell organisms, could travel through the newly discovered TRAPPIST-1—an unusual solar system that presents an exciting new place in the Milky Way to search for extraterrestrial life.
“Frequent material exchange between adjacent planets in the tightly packed TRAPPIST-1 system appears likely,” said Krijt, the study’s lead author. “If any of those materials contained life, it’s possible they could inoculate another planet with life.”
For this to happen, an asteroid or comet would have to hit one of the planets, launching debris into space large enough to insulate the life form from the hazards of space travel. The material would have to be ejected fast enough to break away from the planet’s gravitational pull but not so fast that it would destroy the life form. And the journey would have to be relatively short so the life form could survive.
The researchers ran several simulations for TRAPPIST-1 and found that the process could occur over a period as short as 10 years. Most of the mass transferred between planets that would be large enough for life to endure irradiation during transfer and heat during re-entry would be ejected just above escape velocity, they concluded.
“Given that tightly packed planetary systems are being detected more frequently, this research will make us rethink what we expect to find in terms of habitable planets and the transfer of life—not only in the TRAPPIST-1 system, but elsewhere,” said Fred Ciesla, UChicago professor of geophysical sciences and a co-author of the paper. “We should be thinking in terms of systems of planets as a whole, and how they interact, rather than in terms of individual planets.”
Number of discovered exoplanets exploding
The first exoplanet, a planet orbiting a star other than the sun, was confirmed in 1992. Today, more than 3,600 exoplanet candidates have been discovered, with at least 3,000 additional candidates waiting to be confirmed. In addition, more than 600 multiple exoplanetary systems have been confirmed.
“The relatively new field of exoplanetology is exploding and being considered more seriously than ever,” Ciesla said. “If we took the solar system as a model, we could never have imagined the things we’re finding, such as the recent discovery of a planet that orbits two suns.”
The push now is not so much to discover new exoplanets but rather to characterize them, determine how they evolved and understand how they interact, Krijt said.
Exoplanetary systems serve as laboratories to help scientists comprehend the solar system, Ciesla said, noting that 40,000 tons of space debris falls to Earth each year. “Material from Earth must be floating around out there, too, and it’s conceivable that some of it might be carrying life. Some forms of life are very robust and could survive space travel.” | 0.899868 | 3.878389 |
On October 16, 2017, an international group of astronomers and physicists excitedly reported the first simultaneous detection of light and gravitational waves from the same source — a merger of two neutron stars. Now, a team that includes several University of Maryland astronomers has identified a direct relative of that historic event.
The newly described object, named GRB150101B, was reported as a gamma-ray burst localized by NASA’s Neil Gehrels Swift Observatory in 2015. Follow-up observations by NASA’s Chandra X-ray Observatory, the Hubble Space Telescope (HST) and the Discovery Channel Telescope (DCT) suggest that GRB150101B shares remarkable similarities with the neutron star merger, named GW170817, discovered by the Laser Interferometer Gravitational-wave Observatory (LIGO) and observed by multiple light-gathering telescopes in 2017.
A new study suggests that these two separate objects may, in fact, be directly related. The results were published on October 16, 2018 in the journal Nature Communications.
“It’s a big step to go from one detected object to two,” said study lead author Eleonora Troja, an associate research scientist in the UMD Department of Astronomy with a joint appointment at NASA’s Goddard Space Flight Center. “Our discovery tells us that events like GW170817 and GRB150101B could represent a whole new class of erupting objects that turn on and off — and might actually be relatively common.”
Troja and her colleagues suspect that both GRB150101B and GW170817 were produced by the same type of event: a merger of two neutron stars. These catastrophic coalescences each generated a narrow jet, or beam, of high-energy particles. The jets each produced a short, intense gamma-ray burst (GRB) — a powerful flash that lasts only a few seconds. GW170817 also created ripples in space-time called gravitational waves, suggesting that this might be a common feature of neutron star mergers.
The apparent match between GRB150101B and GW170817 is striking: both produced an unusually faint and short-lived gamma ray burst and both were a source of bright, blue optical light and long-lasting X-ray emission. The host galaxies are also remarkably similar, based on HST and DCT observations. Both are bright elliptical galaxies with a population of stars a few billion years old that display no evidence of new star formation.
“We have a case of cosmic look-alikes,” said study co-author Geoffrey Ryan, a postdoctoral researcher in the UMD Department of Astronomy and a fellow of the Joint Space-Science Institute. “They look the same, act the same and come from similar neighborhoods, so the simplest explanation is that they are from the same family of objects.”
In the cases of both GRB150101B and GW170817, the explosion was likely viewed “off-axis,” that is, with the jet not pointing directly towards Earth. So far, these events are the only two off-axis short GRBs that astronomers have identified.
The optical emission from GRB150101B is largely in the blue portion of the spectrum, providing an important clue that this event is another kilonova, as seen in GW170817. A kilonova is a luminous flash of radioactive light that produces large quantities of important elements like silver, gold, platinum and uranium.
While there are many commonalities between GRB150101B and GW170817, there are two very important differences. One is their location: GW170817 is relatively close, at about 130 million light years from Earth, while GRB150101B lies about 1.7 billion light years away.
The second important difference is that, unlike GW170817, gravitational wave data does not exist for GRB150101B. Without this information, the team cannot calculate the masses of the two objects that merged. It is possible that the event resulted from the merger of a black hole and a neutron star, rather than two neutron stars.
“Surely it’s only a matter of time before another event like GW170817 will provide both gravitational wave data and electromagnetic imagery. If the next such observation reveals a merger between a neutron star and a black hole, that would be truly groundbreaking,” said study co-author Alexander Kutyrev, an associate research scientist in the UMD Department of Astronomy with a joint appointment at NASA’s Goddard Space Flight Center. “Our latest observations give us renewed hope that we’ll see such an event before too long.”
It is possible that a few mergers like the ones seen in GW170817 and GRB150101B have been detected previously, but were not properly identified using complementary observations in different wavelengths of light, according to the researchers. Without such detections — in particular, at longer wavelengths such as X-rays or optical light — it is very difficult to determine the precise location of events that produce gamma-ray bursts.
In the case of GRB150101B, astronomers first thought that the event might coincide with an X-ray source detected by Swift in the center of the galaxy. The most likely explanation for such a source would be a supermassive black hole devouring gas and dust. However, follow-up observations with Chandra placed the event further away from the center of the host galaxy.
According to the researchers, even if LIGO had been operational in early 2015, it would very likely not have detected gravitational waves from GRB150101B because of the event’s greater distance from Earth. All the same, every new event observed with both LIGO and multiple light-gathering telescopes will add important new pieces to the puzzle.
“Every new observation helps us learn better how to identify kilonovae with spectral fingerprints: silver creates a blue color, whereas gold and platinum add a shade of red, for example,” Troja added. “We’ve been able identify this kilonova without gravitational wave data, so maybe in the future, we’ll even be able to do this without directly observing a gamma-ray burst.” | 0.877107 | 4.052135 |
Science and Technology Facilities Council
Study of 4.3 billion-year-old lunar rock overturns theory on formation of the Moon's crust
Scientists studying lunar rock collected during the NASA Apollo 17 Mission in 1972 have found new evidence that large portions of the moon’s crust were formed by massive impact events.
This evidence overturns previous theories that the magmas rising from the moon’s interior were responsible for helping form the lunar crust. It was thought that impacts from colliding asteroids and comets were only destructive, but the research has shown that they also helped to build the outer layer of the moon.
The discovery made by scientists funded by the Science and Technology Facilities Council (STFC) also provides a unique record of how the terrestrial planets in our solar system were formed and shaped by geological processes over time.
Radiometric age dating of the sample of moon rock at the Swedish Museum of Natural History revealed that it formed over 4.3 billion years ago. Scientists found that the sample contains unique evidence of mineral formation at incredibly high temperatures (in excess of 2300 °C). This can only be achieved by the melting the outer layer of a planet in a very large impact event.
The STFC-funded researchers from the University of Portsmouth, The University of Manchester and The Open University, used a technique called electron backscatter diffraction (EBSD) to discover the former presence of cubic zirconia, a mineral phase that would only occur in rocks heated above 2300 °C. EBSD is a technique that can determine the structure, crystal orientation and phase of materials.
Dr James Darling from the University of Portsmouth said:
“The discovery reveals that unimaginably violent impact events helped to build the lunar crust, not only destroy it. Going forward, it is exciting that we now have laboratory tools to help us fully understand their effects on the terrestrial planets.”
The research paper is now available in Nature Astronomy.
An interactive image of the complex crystal analysed in the study can be viewed online using the Virtual Microscope.
Resources on lunar geology for schools, museums and outreach organisers are available from our STFC Lunar Rocks and Meteorites Loan Scheme.
Latest News from
Science and Technology Facilities Council
UK supercomputers simulate impact of the asteroid thought to have wiped out dinosaurs28/05/2020 10:33:00
One of the UK’s most powerful high-performance computers has helped scientists simulate the impact of the asteroid, that hit earth just under 66 million years ago and is thought to have killed dinosaurs.
Harwell Space Cluster launches ambitious growth strategy27/05/2020 12:05:00
Harwell Space Cluster has published its 10 year growth strategy, supporting its ambition to become the most compelling global gateway to the space sector and making it an even more powerful engine of growth, innovation and investment for the whole of the UK.
North West HealthTec Cluster marks its first anniversary26/05/2020 13:05:00
A year of life-changing innovation, award-winning business and dynamic collaboration have marked the first year of the HealthTec Cluster for the North West.
UK government boosts vaccine manufacturing capacity at Harwell19/05/2020 13:05:00
The Vaccines Manufacturing and Innovation Centre (VMIC), a not-for-profit organisation providing the UK’s first strategic vaccine development and advanced manufacturing capability, has been awarded up to £131 million by the government, boosting investment in the UK’s vaccines infrastructure and increasing capacity to manufacture a COVID-19 vaccine.
Scientists improve our understanding of the way that stars evolve12/05/2020 15:05:00
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Study finds half of UK rice breaches limits on arsenic for children11/05/2020 15:38:00
A team of scientists have found 28 out of 55 rice samples sold in the UK contained levels of arsenic that were higher than European Commission regulations allow for babies and children under five.
SPICE receives "First Light"27/04/2020 14:38:00
RAL Space’s SPICE instrument has successfully taken its first measurements of the Sun on board the European Space Agency’s (ESA) Solar Orbiter.
Promising, early career researchers awarded fellowships24/04/2020 15:05:00
Ten talented researchers, who are in the early stages of their career and have clear leadership potential, have been awarded five-year fellowships to help them realise their research ambitions. | 0.804613 | 3.246107 |
Almost two hours before Buzz Aldrin and Neil Armstrong were slated to take off from the moon after the famous and historic moonwalk, an unmanned Russian probe called Luna 15 crash-landed on the moon about 540 miles away from Eagle.
The Luna missions began back in 1958, much before the Apollo program was even conceived. The mission of the Luna program was to send a series of robotic spacecraft to the moon either as a lander or an orbiter. The end goal was to bring samples back from the moon. Luna 15 was the fifteenth officially designated mission; however; it was the thirty-first if we are keeping track of the actual launches.
The Luna program had to face a number of failures earlier in the mission. A number of their launches were not able to reach the orbit of Earth. The ones that did reach the orbit were unable to leave it. A few them were able to go all the way to the moon only to simply fly past it. A few of them even crashed into the moon. Soviet government refrained from publicly acknowledging these failures, so the number of Luna missions were always lesser than the actual launches.
However, you should not be laughing at the Soviets because the early Pioneer missions that were being executed by the United States were also facing more or less the same failure rates. The first spacecraft to ever leave the earth’s orbit was actually Luna 1 that achieved this feat in its fourth attempt. It was also the first man-made object to reach the moon, the very first probe that was able to execute a soft landing, the first man-made satellite of the moon, the first to take a picture of the far side of the moon and the first to send back close-up pictures of the moon’s surface.
Luna 15 left earth on 13 July 1969, three days before Apollo 11. It entered the orbit on July 17, 1969 – a full three days ahead of the Americans. However, the Soviets had not taken into account the ruggedness of the moon’s surface. So, the Soviet controllers spent invaluable time studying and analyzing the moon’s surface for the next four days.
Soviet controllers decided to land the Luna 15 after two hours of Apollo 11 landing, collect samples, and start the journey back to earth before Apollo11. However, the uncertainty of the terrain delayed the landing again. Finally, two hours before Apollo 11 was slated for liftoff, the controllers pushed for a landing. By then, the Luna 15 had circled the moon for fifty-two times. After four minutes of descent, it crashed into the side of a mountain.
The Luna 16 mission later on succeeded and was the first robotic probe to land on the moon and bring a sample back to earth. Further Luna missions have also placed two lunar rovers – again another first – on the lunar surface. | 0.800664 | 3.01216 |
From: Jet Propulsion Laboratory
Posted: Thursday, October 7, 2010
PASADENA, Calif. - Fans of space exploration are familiar with the term T-minus, which NASA uses as a countdown to a rocket launch. But what of those noteworthy mission events where you already have a spacecraft in space, as with the upcoming flyby of a comet?
"We use 'E-minus' to help with our mission planning," said Tim Larson, EPOXI mission project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "The 'E' stands for encounter, and that is exactly what is going to happen one month from today, when our spacecraft has a close encounter with comet Hartley 2."
The EPOXI mission's Nov. 4 encounter with Hartley 2 will be only the fifth time in history that a comet has been imaged close-up. At point of closest approach, the spacecraft will be about 700 kilometers (435 miles) from the comet.
"Hartley 2 better not blink, because we'll be screaming by at 12.3 kilometers per second (7.6 miles per second), said Larson.
One month out, the spacecraft is closing the distance with the comet at a rate of 976,000 kilometers (607,000 miles) per day. As it gets closer, the rate of closure will increase to a little over 1,000,000 kilometers (620,000 miles) per day.
For those interested in what the "T-minus" stands for in a NASA countdown to a rocket launch - it translates to "Time-minus." For example, when a rocket is getting ready for liftoff, it will be lifting off at a specific time. If that time is 45 seconds away, it is said to be "T-minus 45 seconds and counting."
EPOXI is an extended mission that utilizes the already "in-flight" Deep Impact spacecraft to explore distinct celestial targets of opportunity. The name EPOXI itself is a combination of the names for the two extended mission components: the extrasolar planet observations, called Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact Extended Investigation (DIXI). The spacecraft will continue to be referred to as "Deep Impact."
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the EPOXI mission for NASA's Science Mission Directorate, Washington. The University of Maryland, College Park, is home to the mission's principal investigator, Michael A'Hearn. Drake Deming of NASA's Goddard Space Flight Center, Greenbelt, Md., is the science lead for the mission's extrasolar planet observations. The spacecraft was built for NASA by Ball Aerospace & Technologies Corp., Boulder, Colo.
For more information about EPOXI visit http://epoxi.umd.edu/ .
// end // | 0.828901 | 3.342868 |
AUSTIN, Texas, June 21 (UPI) — Researchers have identified an 11 million-year-old “super Neptune” exoplanet, the youngest fully formed exoplanet. By comparison, Earth is roughly 4.5 billion years old.
The discovery of K2-33b may shed light on the process of planetary evolution and the origin of close-in exoplanets.
The planet is roughly the size of Neptune, but lies much closer to its host star — 10 times closer than Mercury is to the sun. The exoplanet boasts an orbital period of just 5.4 days.
Researchers aren’t quite sure how or why such a large planet begins planetary life so close to its sun. Until recently, planetary scientists thought larger planets found near their host stars migrated from farther away. The latest discovery suggests that’s not always the case.
“The question we are answering is: Did those planets take a long time to get into those hot orbits, or could they have been there from a very early stage?” Trevor David, an astronomer at Caltech, said in a news release. “We are saying, at least in this one case, that they can indeed be there at a very early stage.”
Now, astronomers must work to understand which formation process is most common. If close-in planet formation is rare, and the majority of super Neptunes and hot Jupiters migrate from farther afield, their paths could make the formation of habitable, terrestrial worlds like Earth less likely.
“If Jupiter or Neptune had migrated inward after the terrestrial planets formed, it seems unlikely that our solar system would have an Earth, or any of the terrestrial planets at all,” said Andrew Mann, an astronomer at the University of Texas and first author of a new paper on K2-33b.
Mann and David led two separate investigations of K2-33b, arriving at independent but similar conclusions. The work of Mann and his colleagues was published in the Astrophysical Journal, while the research conducted by David and his colleagues was detailed in the journal Nature. | 0.825838 | 3.561079 |
Two stars collided — On August 17th, astronomers bore witness to the titanic collision of two neutron stars, the densest things in the universe besides black holes. In the collision’s wake, astronomers answered multiple major questions that have dominated their field for a generation. And there was more, and there is much more yet to come from this discovery… but now what?
~ Do scientists even have the right instrumentation to follow these discoveries up?
Europa’s icy plate tectonics — According to new research published in Journal of Geophysical Research: Planets, Europa has what it takes to support plate tectonics. Using computer models, a team lead by Brown University planetary scientist Brandon Johnson was able to demonstrate the physical feasibility of icy plates driving deep into the icy interior in a processes similar to what’s seen on Earth. This same process could be delivering important minerals to the ocean below, heightening the moon’s status a potentially habitable world.
~ Jupiter’s moon Europa features a ‘warm’ subterranean ocean covered in ice, leading to decades of speculation it might harbour life.
Voyager 1 just fired up its backup thrusters for the first time in 37 years — Voyager 1, the probe which became the first man-made object to leave the solar system in 2012, has been away from home for a long, long time – approximately 40 years. It’s still been beaming back reams of data. (It’s so lonely.) Now it’s nearly 21 billion kilometeres from Earth. Last week, NASA said it had successfully dusted off the spacecraft’s long-dormant backup thrusters for the first time in 37 years.
~ And, in its off time, 1 has been sending extremely ill-advised texts to possible distant alien civilisations.
Spacesuit’s Take Me Home button — Imagine, unlike in the film Gravity, a struggling astronaut presses an emergency button which automatically takes her back to the International Space Station or another space-based habitat. Such a system is currently under development at Draper Labs, and it could soon become a standard feature on spacesuits.
~ There goes my Space Life Preserver plan.
Type 2 diabetes might be reversible — For those suffering from type 2 diabetes, there is good news. Nearly half of the participants in a watershed trial of a new diabetes treatment were able to reverse their affliction. The method is quite simple: an all liquid diet that causes participants to lose a lot of weight, followed by a carefully controlled diet of real solid foods. Four times a day, a sachet of powder is stirred in water to make a soup or shake. They contain about 200 calories, but also the right balance of nutrients. If the patient can keep away from other foods long enough, there is a chance of reversing type 2 diabetes completely.
~ Jenny Craig must be sharpening her pencil.
Personal urban retreat — A transparent capsule on a roof high above the city may offer a temporary escape in urban environments, while also allowing us to reconnect with our environment. The capsule nestles in the density of the city, but escapes it due to its high position. The shape embraces the buildings since it lies partly on the roof and the facade. Like a mountain retreat, it offers a quiet space to breathe with a new viewpoint.
~ I reckon people would just fill them up with junk as extra storage.
Artificial spider silk beanie — Best Made Company’s Cap of Courage is a US$198 striped beanie that’s made by combining Bolt’s Microsilk and Rambouillet wool. The run of 100 caps is a proof of concept to show that the elusive science behind crafting synthetic spider’s silk is no longer elusive. It’s partly a product of proteins that mimic spider silk grown in yeast.
~ At least it’s not brewed from dead flies, so the courage part comes from paying that much for a hat, presumably.
Almost all Bronze Age iron artefacts were made from meteorite iron — According to a new study, it’s possible that all iron-based weapons and tools of the Bronze Age were forged using metal salvaged from meteorites. The finding has given experts a better insight into how these tools were created before humans worked out how to produce iron from its ore.
~ The surprise for me is that iron was smelted at all in the Bronze Age, before the beginning of the official Iron Age. | 0.872325 | 3.263954 |
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