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Mass Transfer in Binary Star Systems
This Demonstration shows the path of a gas particle transferred from a secondary star (S) to a more massive primary star (P) in a binary star system. The gas particle starts at the first Lagrange point (L1). The mass ratio is the ratio of the masses S to P. The initial velocity is shown as a blue arrow and the center of mass (C) is at the point marked +.[more]
If the gas particle is impeded by something such as an accretion disk, then its velocity must change to match the slower velocity gas in the disk. The energy lost during the impact shows as a bright spot on the edge of the accretion disk. Observing such bright spots can provide important information, such as the radius of the disk, which is not directly observable.[less]
mass ratio — the ratio of the masses of the mass-losing secondary star to the mass-gaining primary star
time — the number of elapsed orbits of the binary star system
initial velocity — The component is the component of the initial velocity of the particle in the direction of the mass-gaining primary star. The component is the component of the initial velocity of the particle in the direction of the orbit of the mass-losing star (in this simulation, the direction is up)
friction — the coefficient that governs the orbital decay of the transfer particle
In a binary system, the first Lagrange point (L1) is the point of gravitational equilibrium between the two stars. When the secondary star grows so large that L1 is on its surface, gas transfers from that point to the more massive primary star. This type of system is also known as a semi-detached binary star system. The path of a particle of gas depends on its initial velocity and the friction caused by other gas particles in the transfer.
Snapshot 1: This shows the trajectory of the mass transfer stream with low friction.
Snapshot 2: The masses of the stars are equal, so the center of mass is at the first Lagrange point.
Snapshot 3: With high friction, the trajectory steadily decays. | 0.822768 | 3.875733 |
Researchers from the Université libre de Bruxelles and the Université de Montpellier have succeeded, for the first time, in measuring the temperature at the heart of certain stars, as well as dating them. Their study is published in the January 8 issue of Nature.
In 1926, astrophysicist Sir Arthur Eddington wrote in his work The internal constitution of the stars: “At first sight it would seem that the deep interior of the Sun and stars is less accessible to scientific investigation than any other region of the universe. What appliance can pierce through the outer layers of a star and test the conditions within?”
Nearly 90 years later, this question has now gained an answer, thanks to the work of a team of six astrophysicists from the ULB Faculty of Science's Institute of Astronomy and Astrophysics and the Université de Montpellier's Laboratory of the Universe and Particles who have managed to measure the temperature at the heart of specific stars and to estimate their age.
These measurements use isotopes1 of well-chosen chemical elements (such as 99Tc and 93Nb), which act as both a thermometer and a clock and which the researchers have found to be in abundant supply on the stars' surfaces. To do this, they have used the HERMES spectrograph (mounted on the KULeuven Mercator telescope located on La Palma in the Canary Islands), built in the context of collaboration whose main partners were the KULeuven, the ULB and the Royal Observatory of Belgium.
The temperatures measured by the astrophysicists are those of the deep layers within the stars where the synthesis of elements heavier than iron takes place. These heavy elements, after having been dredged-up to the star's surface, are ejected into the interstellar medium at the end of the giant star's life. They become part of large dust and gas clouds making up the interstellar medium and giving birth to new stars. This is the scenario under which the Sun came into existence four and a half billion years ago. The heavier-than-iron elements that we use today here on the Earth in a range of technological applications (such as niobium in permanent magnets or cerium in catalytic converters) have followed this same path.
Our understanding of the origin of all these elements has been greatly improved by this study, just published in the 8th January issue of Nature.
1. A chemical element is characterised by its number of protons. The number of neutrons can vary for a given element; one says it has different isotopes. For example, carbon (C) normally counts 6 protons and 6 neutrons (expressed as 12C, whereby the upper script before the element symbol is the sum of the number of protons and neutrons) but it can sometimes have 7 (13C) or even 8 (14C) neutrons.
2. The Big Bang mainly produced hydrogen and helium. | 0.875419 | 3.871017 |
Murmuration is the word used for a flock of birds in flight, and the shapes they make as they maneuver, like undulating ribbon seen in the picture below, made of many individual birds, like a fluid sort of fabric across the sky:
For years, no one knew how birds flew in murmurations without crashing into each other… it was a puzzle of math and physics and biology. Within the past few years, physicists at the Institute for Complex Systems in Rome were able to develop a 3D reconstruction able to track the flight of individual birds within flocks of thousands, which revealed that each bird keeps spatial track of the seven birds closest to it, regardless of their distance. If one bird turns, that adjustment travels through the flock at 60-120 feet per second, allowing the whole flock to turn almost simultaneously. I’ve posted a video further down.
One of the researchers, Andrea Cavagna, compares their mathematical model of how a flock maneuvers to the equations describing superfluid helium–the strange properties that helium acquires when super-cooled–and says the equations are identical, in this Science article from 7/27/14 by Marcus Woo.
Superfluid helium is weird and fascinating, take a look:
Superfluid helium qualities are fluidity, cohesion, movement without friction, and zero surface tension. Zero entropy is another quality, and I wonder if the fast and accurate wavelike transmission of information across a flock might be similar to zero entropy?
And then compare those qualities to starling flock, do you see fluidity, cohesion, movement without friction, and zero surface tension?
“Starlings may simply be the most visible and beautiful example of a biological criticality that also seems to operate in proteins and neurons, hinting at universal principles yet to be understood.” Brandon Keim, The Startling Science of a Starling Murmuration published in Wired Magazine, 11/8/11. (follow him on Twitter).
And now for the completely non-scientific leaps of imagination: I look at those wheeling flocks, and I also can imagine that each bird is a tiny subatomic particle of matter, each bird an individual mitochondria within a single cell:
And then, I look again, and I can imagine that each bird is a planet or a star, in a universe or a galaxy shaped flock, like these images captured by the Hubble telescope:
And if we come back down to earth, there are some similarities in schools of fish too:
Behaviorally, in birds and in fish, it seems to be a mechanism against predators, and useful in foraging, potentially helpful in efficient flying and swimming (those in a slipstream behind others expend less energy).
I wonder if there is an even faintly similar behavioral equivalent in humans, with one individual and their group of seven closest people (remember, the key in the flock formations is that each bird keeps track of the seven other birds closest to it), whether those seven are closest geographically or closest identified with, and each with their own seven overlapping people… and the actions of just one or two would then be able to shift a larger group to a new direction, just as one or two birds can turn a flock.
There’s a giant leap of imagination for you… I started by writing about birds, and I didn’t quite think this post would travel from birds to stars to neurons to crowds and a civil rights march in 1963. I think I’d best stop before I start talking about current day politics…
One more thought, in honor of Martin Luther King, and this Martin Luther King day on January 18, 2016, his quote: “We must all learn to live together like brothers–or we will all perish together as fools.”
If you’ve come this far and are still reading with me, I hope you enjoyed the trip through my addled thought processes, wild leaps and all. | 0.833987 | 3.212185 |
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is there a type of average of the speed of planets travelling in space around the sun, and is that a significant idea?
Are we suggesting radioactive decay is intrinsic to a standard for a universal measurement of time?
assumed the planets moved at the same speed?
even then was it assumed the planets moved at the same speed
For instance, who has measured the weights of planets according to Newton?
Quote from: opportunityFor instance, who has measured the weights of planets according to Newton?Newton's law of gravitation allowed astronomers to weigh (estimate the relative masses) of any astronomical body with an orbiting satellite.- It was easy to find the mass of the Sun - it has orbiting planets- It is easy to measure the mass of Earth and Jupiter, since they have very obvious moons- With better telescopes, it became possible to weigh Mars and Saturn (they also have moons)However, it was only with Cavendish's laboratory experiment in 1798 that Newton's "G" was measured, and this allowed the relative masses of the Sun and planets to be turned into actual masses.So, depending on your viewpoint (theory or practice), the answer could be "Newton" or "Cavendish".See: https://en.wikipedia.org/wiki/Cavendish_experiment
Quote from: opportunity on 17/12/2018 10:12:12even then was it assumed the planets moved at the same speedIn the ancient heliocentric view of the universe it was assumed that we stayed still and the planets etc moved.So, plainly, they didn't move at the same speed as us.Post Copernicus, we accept that all the planets, including the Earth move round the Sun.And that requires them all to have different orbital speeds.When Kepler looked into ithttps://en.wikipedia.org/wiki/Kepler%27s_laws_of_planetary_motionhe deduced the relative speeds of the known planets and, of course, they were all different.And with the measurement of the transit of venus https://en.wikipedia.org/wiki/Transit_of_Venus,_1639He was able to measure the actual speeds so, at no point in history was it "assumed the planets moved at the same speed"... "as us".So why say it was?
The question is how actual planetary speed is calculated.
A question is how Newton calculated the distances of the planets from the sun and masses, and of course thus speed;
Just to get things clear, who knows how Newton did that? | 0.850957 | 3.485092 |
It is a known fact for scientists that Comet 67P/Churyumov-Gerasimenko lacks nitrogen. Back in 2014, ESA’s Rosetta spacecraft measured the gases in a comet’s coma after its ten years of traveling toward it. The question is: Why is the comet so low in nitrogen gas?
According to two new studies shared in Nature Astronomy, the nitrogen is concealed in the building blocks of life; therefore, they are not low at all. Rosetta spacecraft lasted for two years on its mission before crashing into the Comet 67P. The probe also unsuccessfully released a lander, which crippled when it landed on the comet’s surface. However, it was still able to take a few images.
After Rosetta’s mission three years ago, the scientists are still studying the data collected by the spacecraft. “Although Rosetta operations ended over three years ago, it is still offering us an incredible amount of new science and remains a truly ground-breaking mission,” said Matt Taylor, ESA’s Rosetta Project Scientist.
The first new study
The first modern study is based on observations using Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA). Comets are an icy, small Solar System body, while the coma is a “fuzzy” appearance that a comet gets when it passes close to the Sun. The Comet’s 67P coma was analyzed by Rosetta and was found to contain a reasonable amount of chemicals such as oxygen and carbon, but lacked nitrogen.
“The reason behind this nitrogen depletion has remained a major open question in cometary science,” said Kathrin Altwegg of the University of Bern, Switzerland, principal investigator for the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument and lead author of a new study. “Using ROSINA observations of Comet 67P, we discovered that this ‘missing’ nitrogen might, in fact, be tied up in ammonium salts that are difficult to detect in space. Finding ammonium salts on the comet is hugely exciting from an astrobiology perspective,” she added in a press release.
The molecular panspermia theory
The molecular panspermia theory is an old idea that refers to a comet’s building blocks of life as having a crucial role in spreading them throughout the Solar System. Rosetta discovered both glycine and phosphorus in 67P’s coma in 2016, which kind of proves that the theory is correct. It is believed that the comet’s containing those blocks of life, bombarded our planet to bring water on it, in the Earth’s early days. According to the theory, the blocks of life are forged in space and spread to planets via comets and asteroids.
“Finding ammonium salts on the comet is hugely exciting from an astrobiology perspective,” said Altwegg. “This discovery highlights just how much we can learn from these intriguing celestial objects.”
The second new study
The second new study is based on observations using Rosetta’s Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument. Their research brought to light the first organic compounds ever found on the surface of a comet’s nucleus. Aliphatic organic mixtures were discovered for the first time on the Comet 67P, which are chains of hydrogen and carbon that also build blocks of life.
“Where – and when – these aliphatic compounds came from is hugely important, as they are thought to be essential building blocks of life as we know it,” explained the lead author is Andrea Raponi of INAF, the National Institute for Astrophysics in Italy. “The origin of material such as this found in comets is crucial to our understanding of not only our Solar System but planetary systems throughout the Universe,” she added.
Is the molecular panspermia theory confirmed?
These organic mixtures that form blocks of life are not originated from the comet itself. They were created in a solar nebula, an early formed Sun or in the interstellar medium, said scientists in this new study. “Inspiring discoveries such as these help us to understand a great deal more about not only comets themselves, but the history, characteristics, and evolution of our entire cosmic neighborhood,” said Taylor.
This second study also shows the strong compositional similarities between 67P and other carbon-rich objects outside the Solar System. “We found that the nucleus of Comet 67P has a composition similar to the interstellar medium, indicating that the comet contains unaltered presolar material,” says study co-author Fabrizio Capaccioni, also of INAF and principal investigator for VIRTIS. “This composition is also shared by asteroids and some meteorites that we have found on Earth, suggesting that these ancient, rocky bodies locked up various compounds from the primordial cloud that went on to form the Solar System.”
He also added that “This may mean that at least a fraction of the organic compounds in the early Solar System came directly from the wider interstellar medium – and thus that other planetary systems may also have access to these compounds.”
Rosetta is not the only spacecraft that crushed ending its mission. Cassini spacecraft ended its mission over two years ago when its trajectory took it into Saturn’s upper atmosphere burning it up. Scientists are still using the data from both cases, and papers continue to be published. There is so much information from the data collected from the probes that researchers can conduct new different studies.
“Although Rosetta operations ended over three years ago, it is still offering us an incredible amount of new science and remains a truly ground-breaking mission,” adds Taylor. “These studies tackled a couple of open questions in cometary science: why comets are depleted in nitrogen, and where comets got their material from. Inspiring discoveries such as these help us to understand a great deal more about not only comets themselves, but the history, characteristics, and evolution of our entire cosmic neighborhood.”
As our second lead editor, Anna C. Mackinno provides guidance on the stories Great Lakes Ledger reporters cover. She has been instrumental in making sure the content on the site is clear and accurate for our readers. If you see a particularly clever title, you can likely thank Anna. Anna received a BA and and MA from Fordham University. | 0.904704 | 3.944951 |
A dynasty of diamonds in the sky,
You stretch beyond the hemispheres of sight
Scattering stardust like lavish silt as
Unseen tidal forces conspire to tear you apart.
A stellar stream that meanders across space,
Undulating gently out of reach
As two parallel lanes of celestial eddies
That softly lap against the night.
A confluence of uncontrollable, furious breakers,
You burn with four thousand suns
And yet as you pour into the mouth of the galaxy
Your waters are cold to the touch.
Made from dust, and to dust you will return,
Your wavelets start to decompose
Scattering sediment across the empty void
From which new life will flow.
This poem is inspired by recent research, which has found a stellar stream of at least 4,000 stars that have been moving together for over a billion years, covering most of the southern celestial hemisphere.
Within our Galaxy, the Milk Way, stars can sometimes be found gathered together, developing from birth as large clouds of molecular gas to create groups or clusters. However, the massive gravitational forces of the Milky Way constantly pull at these clusters, meaning that they tend to disperse fairly rapidly after birth. However, if the cluster is large enough then they might contain sufficient stellar mass to remain bound together for several hundred million years. Over time these stars create a stellar stream, i.e. a collection of stars that began life as a globular cluster, but which has now been stretched out along its orbit by gravitational forces.
By carefully studying the Gaia Archive (an ESA-funded mission to chart a three-dimensional map of our Galaxy), researchers were able to identify a nearby group of stars as a giant example of one such stellar stream. This particular stellar stream was found to be made up of at least 4,000 stars and is so huge that it stretches across a third of the night sky. The stream’s age is thought to be approximately one billion years old, and its relatively close proximity to the Earth (approximately 300 light years) means that detailed astronomical exploration can take place. Such explorations will provide further insight into star formation as well as providing more information about the gravitational field and mass distribution of the Milky Way.
An audio version of this poem can be heard here: | 0.830708 | 3.676661 |
A giant • It has a mass between 750 billion and one trillion solar masses, • And its diameter is about 100,000 light years
Spiral Galaxy • Concluded that it is spiral through the use of radio astronomy and observations of other galaxies • Means that it has pronounced disk component exhibiting a spiral structure, and a prominent nuclear reagion which is part of a notable bulge/halo component
Belongs to the Local Group • Includes our Milky Way Galaxy, the Large and the Small Magellanic Cloud (LMC and SMC), Andromeda Galaxy also known as M31 and over 30 small galaxies, • It is the second largest (after the Andromeda Galaxy M31)
These galaxies are spread in a volume of nearly 10 million light years diameter, • It is centered somewhere between the Milky Way and M31. • Membership is not certain for all these galaxies, and there are possible other candidate members.
the Milky Way and M31 are by for the most massive, and therefore dominant members. Each of these two giant spirals has accumulated a system of satellite galaxies, where • the system of the Milky Way contains many (nearby) dwarf galaxies, spread all over the sky, namely LMC, SMC, and the dwarf galaxies in Ursa Minor, Draco, Carina, Sextans (dwarf), Sculptor, Fornax, Leo I and Leo II, • the system of the Andromeda galaxy is seen from outside, and thus grouped around its main galaxy M31 in Andromeda, containing bright nearby M32 and M110 as well as fainter and more far-out NGCs 147 and 185, the very faint systems
Neighbors • The closest of all is SagDEG at about 80,000 light years from us and some 50,000 light years from the Galactic Center, followed by the more conspicuous Large and Small Magellanic Cloud at 179,000 and 210,000 light years, respectively
The spiral arms of our Milky Way contain interstellar matter, diffuse nebulae, and young stars and open star clusters emerging from this matter. • The bulge component consists of old stars and contains the globular star clusters; • our galaxy has probably about 200 globulars, of which we know about 150. • These globular clusters are strongly concentrated toward the Galactic Center
From the apparent distribution of clusters in the sky, Harlow Shapley concluded that the center of the Milky Way lies at a considerable distance (which he overestimated) in the direction of Sagittarius and not rather close to us, as had been thought previously by Kapetayn (this is our next lab calculating the distance to the galactic center)
Our solar system is thus situated within the outer regions of this galaxy, well within the disk and only about 20 light years above the equatorial symmetry plane but about 28,000 light years from the Galactic Center. • It takes our Solar System 225 million years or so to revolve once around the galactic center
Tracing the Milky Way's history • The oldest stars (in the globular clusters) orbit the galaxy in elongated elliptical orbits. • Galaxy must have been born from huge gas cloud • Where are the first stars without heavy metals?
History • believe that the galaxy formed out of a large, fairly spherical cloud of cold gas, rotating slowly in space. • At some point in time, the cloud began to collapse in on itself, or condense • Similar to how the solar system and stars formed • Initially, some stars may have formed as the gas cloud began to fragment around the edges
condensing further to form a star or group of stars. • Some very old stars are distributed in a spherical halo around the outside of the galaxy today because the cloud was spherical in the beginning. • At such early times, these stars consisted only of the hydrogen and helium gas which made up the cloud.
The cloud continued to collapse, with more and more stars being formed as it did so. Since the cloud was rotating, the spherical shape began to flatten out into a disc, and the stars which were formed at this time filled the disc regions. • Identical to the process of forming a solar system
As the formation of new stars continued, some stars evolved through their “life” or died • These stars began to shed their atmospheres or explode in huge supernova events. • Through this process older citizens of the still young galaxy enriched the gas in the cloud with the new, heavier elements which they had formed, • the new stars being created in the disc regions contained the heavier elements. • Astronomers call these younger, enriched stars population 1 stars, and the older stars population 2.
The solar system is situated within a smaller spiral arm, called the Local or Orion Arm, which is merely connection between the inner and outer next more massive arms, the Sagittarius Arm and the Perseus Arm
A Puzzle of the Arm • Why don't they wrap around the MW? 225,000,000 years for the Sun to circle the Milky Way age of sun is about 4,500,000,000 years • Therefore - the sun has been around the Milky Way 20 times • If the arms had been around this many times they would have wound up. • But - arms are formed by new stars (which fade away in 107-108 years)
Answer • Sun takes 225,000,000 years to orbitArms fade away (O & B stars) in about 10,000,000 years and new arms form
Theories of Arm Formation • Density wave theory- Density waves move through galaxy compressing matter as it passes and setting off star formation. • self-propagating star formation (or Supernovae chain reaction)- One supernova sends out wave which creates new stars and subsequent supernovae.
The Milky Way system is a spiral galaxy consisting of over 400 billion stars, plus gas and dust arranged into three general components as shown to the left: • The halo - a roughly spherical distribution which contains the oldest stars in the Galaxy, • The nuclear bulge and Galactic Center. • The disk, which contains the majority of the stars, including the sun, and virtually all of the gas and dust
Halo • consists of the oldest stars known, including about 146 Globular Clusters, believed to have been formed during the early formation of the Galaxy with ages of 10-15 billion years from their H-R Diagrams. • The halo is also filled with a very diffuse, hot, highly-ionized gas. The very hot gas in the halo produces a gamma-ray halo.
Dark Halo • Radius of 200,000 or 300,000 light years • Contains 80%-95% of the mass of the galaxy (dark matter)
Not much is known about the mass of the halo. • Investigations of the gaseous halos of other spiral galaxies show that the gas in the halo extends much further than previously thought, out to hundreds of thousands of light years. • Studies of the rotation of the Milky Way show that the halo dominates the mass of the galaxy, but the material is not visible, it it thought to be dark matter.
Galactic Bulge • Radius of 6,000 light years • Composed of old stars (population II) and young stars (population I)
Radius of Central Bulge • 6,000 light years • Thickness of M.W. Disk • 1,000 light years
Galactic Disk • Radius of 60,000 light years • old stars (population II) and young stars (population I), gas, and dust • Spiral arms
Galactic Halo • Radius of 65,000 light years • Includes globular clusters • which contain only old stars (population 2)
Population I Stars • younger, metal-rich stars • found in galactic disk • Population II Stars • older, metal-poor stars • found in galactic halo
Stellar Parallax: • Angle through which a star's position shifts as earth orbits the sun. (actually this only works in determining stellar distances or nearby stars.) • Nearest Stars: Alpha Centauri complex (triple-star system) Proxima Centauri at 1.3 pc (4.3 ly) 0.76 arc-secs Barnard's Star 1.8 pc (6.0 ly) 0.55 arc-secs • Since stellar parallax fails beyond 100 parsecs or so, other methods need to be used1
Luminosity • If we know how bright something really is (known as Luminosity or Absolute Brightness) then we can determine from how bright it appears (Apparent Brightness) how far away it is • Calculated through Variable Stars measure distances out to about 15 million parsecs (15 Mpc)
Rotation • In the disk of the Milky Way, stars and other matter are rotating around the center in a regular pattern, as revealed by Doppler effects
Very important clue on evolution of galaxy The lower the metal abundance (pop I vs. pop II), the farther the objects are found from the plane of the disk (remember, low metal abundance (pop II) means old) stars are born with elemental abundance's of gases of birth stars inherit orbital motion abut galaxy of parent cloud massive stars evolve quickly and spew heavy elements into interstellar medium.
Evolution of MW Galaxy • Huge cloud of primordial gas collapsed into galaxy • Broke apart into small clouds -> formed stars • First stars (population II) formed in globular clusters more than 10 billion years ago. • Galaxy continued to Evolve • Sun emerged 5 billion years ago. | 0.835644 | 3.855449 |
Half a century ago, meteorite fell on Australia and scientists have now discovered it contained star dust formed as long as 5-7 billion years ago.
That makes it the oldest solid material ever found on Earth.
Associate professor Philipp Heck, lead author of the paper describing the findings, published in the Proceedings of the National Academy of Sciences of the United States, said this was one of the most exciting studies he had worked on.
"These are the oldest solid materials ever found, and they tell us about how stars formed in our galaxy," he said.
"They're solid samples of stars, real stardust."
The materials examined by Dr Heck and his colleagues, including from the Australian National University, are called pre-solar grains, minerals formed before our sun was born.
These become trapped in meteorites, remaining unchanged for billions of years as time capsules of the time before the solar system.
These are also quite rare, found only in 5 per cent of meteorites that have fallen to Earth, and they're tiny. Perhaps 100 would fit on a full stop.
The Field Museum of Natural History in Chicago, of which Dr Heck is curator, has the largest part of the Murchison meteorite, which landed near Murchison, Victoria, in 1969.
That has proved to be a treasure trove of pre-solar grains.
Isolating them starts with crushing fragments of the meteorite into a powder, said Jennika Greer, a graduate student at the Field Museum and the University of Chicago and a co-author of the study.
"Once all the pieces are segregated, it's a kind of paste, and it has a pungent characteristic-it smells like rotten peanut butter," she said.
This paste is then dissolved with acid, leaving the pre-solar grains remained.
"It's like burning down the haystack to find the needle," said Dr Heck.
Once isolated, researchers then sought to figure out from what types of stars they came and how old they were.
Age was determined by measuring exposure to cosmic radiation.
"Some of these cosmic rays interact with the matter and form new elements. And the longer they get exposed, the more those elements form,” Dr Heck said.
Measuring how many of these new cosmic-ray produced elements are present in a pre-solar grain can indicate how long it was exposed to cosmic rays, which tells us how old it is.
But the age of the pre-solar grains wasn't the end of the discovery. As pre-solar grains are formed when a star dies, they can tell about the history of stars.
"We have more young grains than we expected. Our hypothesis is that the majority of those grains, which are 4.9 to 4.6 billion years old, formed in an episode of enhanced star formation. There was a time before the start of the solar system when more stars formed than normal," Heck said.
Receive the latest developments and updates on Australia’s space industry direct to your inbox. Subscribe today to Space Connect here. | 0.815414 | 3.950681 |
Geminid meteors sparkle during long December nights
December brings us spectacular night skies and arguably the richest meteor shower of the year, the Geminids. We still have the Summer Triangle of bright stars, Vega in Lyra, Deneb in Cygnus and Altair in Aquila, high in the south-west at nightfall while the unmistakable figure of Orion dominates the midnight hours, surrounded by his cohort of familiar winter constellations. By the predawn, the Plough sails overhead and the night’s only conspicuous planets shine to the south of east.
Our longest nights, of course, occur around the winter solstice when the Sun reaches its most southerly point in its annual trek around the sky. This occurs at 16:28 GMT on the 21st when Edinburgh’s night, measured from sunset to sunrise, lasts for 17 hours and 3 minutes, which no less than 10 hours and 39 minutes longer than at June’s summer solstice.
Sunrise/sunset times for Edinburgh during December vary from 08:19/15:44 on the 1st to 08:42/15:40 on the 21st and 08:44/15:48 on the 31st. The Moon is full on the 3rd, at last quarter on the 10th, new on the 18th and at first quarter on the 26th,
By our map times, the Summer Triangle has toppled low into the west and is being followed by the less impressive Square of Pegasus. The Square’s top-left star, Alpheratz, belongs to Andromeda whose other main stars, Mirach and Almach, line up to its left. A spur of fainter stars above Mirach leads us to the Andromeda Galaxy, whose oval glow reaches us from 2.5 million light years away.
Orion is in the east-south-east, his Belt pointing up Aldebaran and the Pleiades in Taurus and down to where the brightest nighttime star, Sirius in Canis Major, rises less than one hour later.
The Moon lies to the right of Aldebaran and below the Pleiades on the night of 2nd-3rd, to the left of Aldebaran a day later and comes around again to occult the star in the early hours of the 31st. We need a telescope to see Aldebaran wink out at the Moon’s limb at 01:01 and reappear at 01:57 as seen from Edinburgh.
It is from a radiant point near Castor in Gemini, north-east of Orion, that meteors from the Geminids shower diverge between the 8th and 17th although, of course, the meteors fly in all parts of the sky. With negligible moonlight this year, and given decent weather, we are in for a stunning display of sparkling long-trailed meteors whose paths point back to the radiant. Rates for an observer under an ideal dark sky could peak at more than 100 per hour at the shower’s peak on the night of the 13th-14th, though most of us may glimpse only a fraction of these.
Although most meteors originate as cometary debris, the Geminids appear to be rocky splinters from the 5 km-wide asteroid, Phaethon, which dives within 21 million km of the Sun every 523 days. In what is its closest approach to the Earth since its discovery in 1983, Phaethon sweeps only 10.3 million km from the Earth on the 16th when a telescope might show it as a tenth magnitude speck speeding past Alpheratz.
December’s second shower, the Ursids, derives from Comet Tuttle and is active between the 17th and 25th, peaking on the 23rd. Typically it yields fewer than ten meteors per hour so I rarely mention it here – I believe my last time was 37 years ago – but very occasionally it rivals the Geminids in intensity, if only for a few hours. The radiant point lies near the star Kochab in Ursa Minor and is plotted on our northern chart.
The unprecedented interstellar asteroid, discovered using a telescope in Hawaii and featured here hast time, has now been called 1I/’Oumuamua. This indicates that it is our first known interstellar visitor and employs the Hawaiian word ’Oumuamua to reflect its supposed status as a scout from the distant past. Further observations imply that it is remarkably elongated, being at least five times longer than it is wide.
Venus shines brilliantly at magnitude -3.9 very low in the south-east as the night ends, but is soon lost from view as it dives towards the Sun’s far side. It leaves Jupiter as our most prominent (magnitude -1.7 to -1.8) morning object. The giant world rises at Edinburgh’s east-south-eastern horizon at 05:31 on the 1st and 04:07 on the 31st, climbing southwards in the sky to stand some 15° high before dawn. Tracking eastwards in Libra, it passes 0.7° north of the celebrated double star Zubenelgenubi on the 21st.
Mars, fainter at magnitude 1.7 to 1.5, lies 16° above-right of Jupiter on the 1st when it is also about half as bright as Virgo’s star Spica, 3° below and to its right. As Mars tracks east-south-eastwards from Virgo to Libra it almost keeps pace with the Sun, so that it rises at around 03:50 throughout the month. By the 31st, it stands 3° from Jupiter, with Zubenelgenubi below and to Mars’ left in the same binocular field of view. The waning Moon forms a nice triangle with Mars and Spica on the 13th and with Mars and Jupiter on the 14th.
Saturn sets in our bright evening twilight as it heads towards conjunction beyond the Sun on the 21st. Mercury slips around the Sun’s near side on the 13th to become best placed as a morning star between Christmas and New Year. Between the 21st and 31st it brightens between magnitude 0.8 and -0.3, rises 100 or more minutes before Edinburgh’s sunrise and stands around 8° high in the south-east thirty minutes before sunrise. | 0.934246 | 3.461799 |
Planetary scientists have discovered the highest clouds above any planetary surface. They found them above Mars using the SPICAM instrument on board ESA’s Mars Express spacecraft. The results are a new piece in the puzzle of how the Martian atmosphere works.
Until now, scientists had been aware only of the clouds that hug the Martian surface and lower reaches of the atmosphere. Thanks to data from the SPICAM Ultraviolet and Infrared Atmospheric Spectrometer onboard Mars Express, a fleeting layer of clouds have been discovered at an altitude between 80 and 100 kilometres. The clouds are most likely composed of carbon dioxide.
SPICAM made the discovery by observing distant stars just before they disappeared behind Mars. By looking at the effects on the starlight as it travelled through the Martian atmosphere, SPICAM built up a picture of the molecules at different altitudes. Each sweep through the atmosphere is called a profile.
The first hints of the new cloud layer came when certain profiles showed that the star dimmed noticeably when it was behind the 90–100 kilometre high atmospheric layer. Although this happened in only one percent of the profiles, by the time the team had collected 600 profiles, they were confident that the effect was real.
“If you wanted to see these clouds from the surface of Mars, you would probably have to wait until after sunset” says Franck Montmessin, a SPICAM scientist with Service d’Aeronomie du CNRS, Verrières-le-Buisson, France, and lead author of the results. This is because the clouds are very faint and can only be seen reflecting sunlight against the darkness of the night sky. In that respect, they look similar to the mesospheric clouds, also known as noctilucent clouds, on Earth. These occur at 80 kilometres altitude above our planet, where the density of the atmosphere is similar to that of Mars’ at 35 kilometres. The newly discovered Martian clouds therefore occur in a much more rarefied atmospheric location.
At 90–100 kilometres above the Martian surface, the temperature is just –193° Celsius. This means that the clouds are unlikely to be made of water. “We observe the clouds in super-cold conditions where the main atmospheric component CO2 (carbon dioxide), cools below its condensation point. From that we infer that they are made of carbon dioxide,” says Montmessin.
But how do these clouds form? SPICAM has revealed the answer by finding a previously unknown population of minuscule dust grains above 60 kilometres in the Martian atmosphere. The grains are just one hundred nanometres across (a nanometre is one thousand-millionth of a metre).
They are likely to be the ‘nucleation centres’ around which crystals of carbon dioxide form to make clouds. They are either microscopic chippings from the rocks on the surface on Mars that have been blown to extreme altitudes by the winds, or they are the debris from meteors that have burnt up in the Martian atmosphere.
The new high-altitude cloud layer has implications for landing on Mars as it suggests the upper layers of Mars’ atmosphere can be denser than previously thought. This will be an important piece of information for future missions, when using friction in the outer atmosphere to slow down spacecraft (in a technique called ‘aerobraking’), either for landing or going into orbit around the planet. | 0.865113 | 4.046638 |
Plasmas, gas-like collections of ions and electrons, make up an estimated 99 percent of the visible matter in the universe, including the sun, the stars, and the gaseous medium that permeates the space in between. Most of these plasmas, including the solar wind that constantly flows out from the sun and sweeps through the solar system, exist in a turbulent state. How this turbulence works remains a mystery; it’s one of the most dynamic research areas in plasma physics.
Now, two researchers have proposed a new model to explain these dynamic turbulent processes.
The findings, by Nuno Loureiro, an associate professor of nuclear science and engineering and of physics at MIT, and Stanislav Boldyrev, a professor of physics at the University of Wisconsin at Madison, are reported today in the Astrophysical Journal. The paper is the third in a series this year explaining key aspects of how these turbulent collections of charged particles behave.
“Naturally occurring plasmas in space and astrophysical environments are threaded by magnetic fields and exist in a turbulent state,” Loureiro says. “That is, their structure is highly disordered at all scales: If you zoom in to look more and more closely at the wisps and eddies that make up these materials, you’ll see similar signs of disordered structure at every size level.” And while turbulence is a common and widely studied phenomenon that occurs in all kinds of fluids, the turbulence that happens in plasmas is more difficult to predict because of the added factors of electrical currents and magnetic fields.
“Magnetized plasma turbulence is fascinatingly complex and remarkably challenging,” he says.
Simulation conducted by MIT student Daniel Groselj.
Magnetic reconnection is a complicated phenomenon that Loureiro has been studying in detail for more than a decade. To explain the process, he gives a well-studied example: “If you watch a video of a solar flare” as it arches outward and then collapses back onto the sun’s surface, “that’s magnetic reconnection in action. It’s something that happens on the surface of the sun that leads to explosive releases of energy.” Loureiro’s understanding of this process of magnetic reconnection has provided the basis for the new analysis that can now explain some aspects of turbulence in plasmas.
Loureiro and Boldyrev found that magnetic reconnection must play a crucial role in the dynamics of plasma turbulence, an insight that they say fundamentally changes the understanding of the dynamics and properties of space and astrophysical plasmas and “is indeed a conceptual shift in how one thinks about turbulence,” Loureiro says.
Existing hypotheses about the dynamics of plasma turbulence “can correctly predict some aspects of what is observed,” he says, but they “lead to inconsistencies.”
Loureiro worked with Boldyrev, a leading theorist on plasma turbulence, and the two realized “we can fix this by essentially merging the existing theoretical descriptions of turbulence and magnetic reconnection,” Loureiro explains. As a result, “the picture of turbulence gets conceptually modified and leads to results that more closely match what has been observed by satellites that monitor the solar wind, and many numerical simulations.”
Loureiro hastens to add that these results do not prove that the model is correct, but show that it is consistent with existing data. “Further research is definitely needed,” Loureiro says. “The theory makes specific, testable predictions, but these are difficult to check with current simulations and observations.”
He adds, “The theory is quite universal, which increases the possibilities for direct tests.” For example, there is some hope that a new NASA mission, the Parker Solar Probe, which is planned for launch next year and will be observing the sun’s corona (the hot ring of plasma around the sun that is only visible from Earth during a total eclipse), could provide the needed evidence. That probe, Loureiro says, will be going closer to the sun than any previous spacecraft, and it should provide the most accurate data on turbulence in the corona so far.
Collecting this information is well worth the effort, Loureiro says: “Turbulence plays a critical role in a variety of astrophysical phenomena,” including the flows of matter in the core of planets and stars that generate magnetic fields via a dynamo effect, the transport of material in accretion disks around massive central objects such as black holes, the heating of stellar coronae and winds (the gases constantly blown away from the surfaces of stars), and the generation of structures in the interstellar medium that fills the vast spaces between the stars. “A solid understanding of how turbulence works in a plasma is key to solving these longstanding problems,” he says.
“This important study represents a significant step forward toward a deeper physical understanding of magnetized plasma turbulence,” says Dmitri Uzdensky, an associate professor of physics at the University of Colorado, who was not involved in this work. “By elucidating deep connections and interactions between two ubiquitous and fundamental plasma processes — magnetohydrodynamic turbulence and magnetic reconnection — this analysis changes our theoretical picture of how the energy of turbulent plasma motions cascades from large down to small scales.”
He adds, “This work builds on a previous pioneering study published by these authors earlier this year and extends it into a broader realm of collisionless plasmas. This makes the resulting theory directly applicable to more realistic plasma environments found in nature. At the same time, this paper leads to new tantalizing questions about plasma turbulence and reconnection and thus opens new directions of research, hence stimulating future research efforts in space physics and plasma astrophysics.”
The research was supported by a CAREER award from the National Science Foundation and the U.S. Department of Energy through the Partnership in Basic Plasma Science and Engineering. | 0.849358 | 4.117599 |
Nature Astronomy / 3, 916–921 (2019)
Abstract: The surface of the dwarf planet Ceres is considered to be dominated by geological processes typical of small bodies or medium-sized icy bodies, such as impact cratering; there are also features of putative cryovolcanic origin as well as those related to flow of near-surface ice. Extensional features include regional linear troughs, fractures and pit chains, fractures associated with impact craters and with crater floors, and polygonal craters whose walls seem to be structurally controlled. However, no contractional features, which are related to thrust fault activity more typical of large silicate bodies, have been described. Here we report the presence of scarps, ridges and fractures associated with thrust faults, tectonically raised terrains and thrusted craters—all contractional features. These structures closely resemble thrust-fault-related lobate scarps on Mercury and Mars, albeit with lower displacement. They seem more abundant in high-latitude ancient terrains, perhaps owing to illumination effects that aid identification. The observed deformation implies that the crustal material is stronger than water ice but weaker than silicate rocks, consistent with our current knowledge of crustal composition and rheology. These features suggest that large-scale contraction, possibly related to differentiation processes, occurred in the history of Ceres.
Abstract: Elysium Planitia and Oxia Planum are plains located near the Martian dichotomy. Lately, both regions have been extensively analyzed due to the major role that they play in the InSight and ExoMars missions. InSight landed in Elysium Planitia and will obtain the first direct measurement of surface heat flow on Mars. Similarly, the Rosalind Franklin rover on ExoMars 2020 will also provide useful information to understand the thermal state of the planet from data acquired in Oxia Planum, which is the preferred landing site. The proximity of the Martian dichotomy to the area surrounding both landing locations is an important source of spatial variability. In this work, we have modeled the heat flow and the subsurface temperature in the regions adjacent to both landing sites considering the regional context. In order to do so, we have solved the heat conduction equation by means of a finite element analysis and by taking into account topography, crustal composition, and crustal and megaregolith thicknesses. Our results indicate that the spatial variation in these parameters for the region surrounding the InSight landing site involves maximum differences in subsurface temperatures and surface heat flows between highlands and lowlands of about 67% and 16%, respectively. In regard to the area surrounding ExoMars landing site, these differences can reach 28% for subsurface temperatures, and 3% for surface heat flows. Crustal and megaregolith thicknesses together with the thermal properties of the megaregolith layer are the most influential factors affecting heat flows and temperature patterns. We also find that regional variations related to the dichotomy boundary are unlikely to have a large effect on the geothermal heat flux at the InSight and ExoMars landing sites.
Ruiz, J., Jiménez-Díaz, A., Egea-González, I., Parro, L. M., Mansilla, F.
Icarus / 322, 221-226 (2019)
Abstract: Two recent papers, by Karimi et al. (2016, Icarus 272, 102–113) and Karimi and Dombard (2017, Icarus 282, 34–39), tried to deduce paleo-heat flows for, respectively, Mars and Venus from modeling the viscoelastic relaxation of large impact craters. Indeed, crater relaxation would be consequence of the flow of the lower crust and uppermost mantle. This flow is dependent on temperature, permitting the link with the calculation of thermal profiles and heat flows. Both papers used conductive thermal profiles and constant thermal conductivities for both the crust and upper mantle (equivalent to using linear thermal gradients given there were no mention to crustal or mantle heat sources), and appropriate rheological laws. In the present discussion, we show that the background heat flows contemporaneous to impact craters formation and relaxation obtained by Karimi and co-workers, when used along with the assumptions made by these authors, lead to temperatures that produce massive (even total) lower crust melting in all and at least a substantial part of the cases for, respectively, Venus and Mars. It is clear that the heat flow results presented by Karimi and co-workers suffer of inconsistency between model requirements explicitly indicated (a crust free of melting) and the implications of the obtained basal heat flows (a lowermost crust partially or totally molten). Thus, we consider that the papers by Karimi and co-workers do not give reliable information on the thermal history of Mars and Venus.
Scientific Reports / 7, 45629 (2017)
Abstract: Until the acquisition of in-situ measurements, the study of the present-day heat flow of Mars must rely on indirect methods, mainly based on the relation between the thermal state of the lithosphere and its mechanical strength, or on theoretical models of internal evolution. Here, we present a first-order global model for the present-day surface heat flow for Mars, based on the radiogenic heat production of the crust and mantle, on scaling of heat flow variations arising from crustal thickness and topography variations, and on the heat flow derived from the effective elastic thickness of the lithosphere beneath the North Polar Region. Our preferred model finds heat flows varying between 14 and 25 mW m−2, with an average value of 19 mW m−2. Similar results (although about ten percent higher) are obtained if we use heat flow based on the lithospheric strength of the South Polar Region. Moreover, expressing our results in terms of the Urey ratio (the ratio between total internal heat production and total heat loss through the surface), we estimate values close to 0.7–0.75, which indicates a moderate contribution of secular cooling to the heat flow of Mars (consistent with the low heat flow values deduced from lithosphere strength), unless heat-producing elements abundances for Mars are subchondritic.
Icarus / 288, 53-68 (2017)
Abstract: The circum-Hellas area of Mars borders Hellas Planitia, a giant impact ∼4.0–4.2 Ga old making the deepest and broadest depression on Mars, and is characterized by a complex pattern of fracture sets, lobate scarps, grabens, and volcanic plains. The numerous lobate scarps in the circum-Hellas region mainly formed in the Late Noachian and, except Amenthes Rupes, have been scarcely studied. In this work, we study the mechanical behavior and thermal structure of the crust in the circum-Hellas region at the time of lobate scarp formation, through the modeling of the depth of faulting beneath several prominent lobate scarps. We obtain faulting depths between ∼13 and 38 km, depending on the lobate scarp and accounting for uncertainty. These results indicate low surface and mantle heat flows in Noachian to Early Hesperian times, in agreement with heat flow estimates derived from lithospheric strength for several regions of similar age on Mars. Also, faulting depth and associate heat flows are not dependent of the local crustal thickness, which supports a stratified crust in the circum-Hellas region, with heat-producing elements concentrated in an upper layer that is thinner than the whole crust.
Planetary and Space Science / 130, 24-29 (2016)
Abstract: Chaos terrains are among the most prominent landforms of Europa, and are generally among the youngest features recorded on the surface. Chaos units were formed by to endogenic activity, maybe related to solid-state convection and thermal diapirism in the ice shell, perhaps aided by melting of salt-rich ice bodies below the surface. In this work, we analyze the different units of chaotic terrain in a portion of Argadnel Regio, a region located on the anti-Jovian hemisphere of Europa, and their possible timing in the general stratigraphic framework of this satellite. Two different chaos units can be differentiated, based on surface texture, morphology, and cross-cutting relationships with other units, and from interpretations based on pre-existing surface restoration through elimination of a low albedo band. The existence of two stratigraphically different chaos units implies that conditions for chaos formation occurred during more than a single discreet time on Europa, at least in Argadnel Regio, and perhaps in other places. The existence of older chaos units on Europa might be related to convective episodes possibly favored by local conditions in the icy shell, such as variations in grain size, abundance of non-water ice-components, or regional thickness of the brittle lithosphere or the entire ice shell.
Selected Conference Abstracts/Presentations
(2019) Ruiz, J., Jiménez-Díaz, A., Mansilla, F., Parro, L. M., Egea-González, I., Küppers, M. Thrust faulting and contraction of Ceres. VI CPESS. Madrid, Spain.
(2018) Parro, L.M., Mansilla, F., Herrero-Gil, A. Viajando por Planetas en la Semana de la Ciencia: Un proyecto de divulgación de las Ciencias Planetarias. XIII SEA. Salamanca, Spain.
(2018) Egea-Gonzalez, I., Parro, L.M., Jiménez-Díaz, A., Mansilla, F., Herrero-Gil, I., Ruiz., J. Local heat flow and subsurface temperature in InSight landing-site. XIII SEA. Salamanca, Spain.
(2018) Parro, L.M., Jiménez-Díaz, A., Egea-Gonzalez, I., Mansilla, F., Ruiz., J. Marte: Evolución térmica y estructura de su corteza. XIII SEA. Salamanca, Spain.
(2018) Parro, L.M., A. Jiménez-Díaz, F. Mansilla, I. Egea-González, J. Ruiz. Heat flow and thermal structure of the Martian lithosphere. Scientific Workshop: “From Mars Express to ExoMars”, Madrid, Spain.
(2017) Jiménez-Díaz, A., Egea-González, I., Parro, L.M., Tasaka, M., Ruiz, J. On the structure of the lithosphere of Mars: New insights from crustal composition and rheology of the upper mantle. EPSC 2016, Riga, Latvia.
(2017) Galvez, F. Ballesteros, A. García-Frank, S. Gil, A. Gil-Ortiz, M. Gómez-Heras, J. Martínez-Frías, L. M. Parro, V. Parro, E. Pérez-Montero, V. Raposo, and J. A. Vaquerizo. Inclusive Planetary Science Outreach and Education: a Pioneering European Experience. EPSC 2016, Riga, Latvia.
(2017) Parro, L.M., Jiménez-Díaz, A., Ruiz, J. El estudio integrado de la litosfera de Marte. V CPESS. Madrid, Spain.
(2017) Jiménez-Díaz, A., Egea-González, I., Parro, L.M., Ruiz, J. La corteza de Marte y su influencia sobre las propiedades térmicas y mecánicas de la litosfera. V CPESS. Madrid, Spain.
(2017) Ruiz, J., Egea-González, I., Fernández, C., Herrero-Gil, A., Jiménez-Diaz, A., López, V., Mansilla, F., Parro, L., Romeo, I., Williams, J.-P. “Follow the scarps”: claves sobre la evolución y propiedades de los cuerpos planetarios aportadas por escarpes asociados a grandes fallas inversas. V CPESS. Madrid, Spain.
(2017) Jiménez-Díaz, A., Egea-González, I., Parro, L.M., Ruiz, J. On the thermo-mechanical structure of the Martian lithosphere: the role of the crust. 48th LPSC, The Woodlands, TX, USA.
(2016) Parro, L.M., Jiménez-Díaz, A., Mansilla, F., Ruiz, J. The present-day heat flow structure of Mars. AGU Fall Meeting 2016, San Francisco, CA, USA.
(2015) Parro, L.M., Jiménez-Díaz, A., Ruiz, J. Current thermal state of Mars from scaled models of surface heat flow. EPSC 2015, Nantes, France.
(2015) Parro, L. M., Jiménez-Díaz, A., Ruiz, J. Investigación del estado térmico actual de Marte, a partir de modelos de producción de calor y flujo térmico. IV CPESS. Alicante, Spain.
(2015) M. A. López-Valverde, F. González-Galindo, B. Funke, M. García-Comas, M. López-Puertas, J. J. López-Moreno, S. Jimenez-Monferrer, J. Ruiz, L. M. Parro, A. Jimenez-Diaz and the UPWARDS team. UPWARDS: An integral study of Mars in preparation for Exomars. IV CPESS. Alicante, Spain.
(2014) Parro, L. M., Pappalardo, R. T., Ruiz, J. Chaos units in Argadnel Regio, Europa, and implications for geological history. EPSC 2014, Cascais, Portugal.
(2014) Álvarez-Gómez, J. A., Parro, L. M., Aniel-Quiroga, I., González, M., Al-Yahyai, S., Martínez, J., Méndez, F., Rueda, A., Medina, R. Tsunamigenic seismic sources characterization in the Zagros fold and thrust belt. Implications for tsunami threat in the Persian Gulf. EGU 2014, Vienna, Austria.
(2014) Parro, L. M., Ruiz, J., Pappalardo, R. T. Chaos units in Argadnel Regio, Europa: implications for timing of chaos formation. 45th LPSC, The Woodlands, TX, USA.
(2013) Parro, L. M., Ruiz, J., Pappalardo, R. T. Terrenos caóticos e historia geológica en Argadnel Regio, Europa. III CPESS. Madrid, Spain.
(2013) Pimentel, C., Alloza, L. J., Caravantes, G., Jiménez-Díaz, A., López, V., Martín-Herrero, Á., Parro, L. M., Romeo, I., Ruiz, J. Grupo de Ciencias Planetarias de Madrid (GCPM). III CPESS. Madrid, Spain.
(2013) Ruiz, J., McGovern, P. J., Parro, L. M., López, V. Paleo-heat flow and the magnetic and climatic history of Mars. 44th LPSC, The Woodlands, TX, USA. | 0.84822 | 3.926608 |
When astrophysicist Jordan Alexander was given the chance to travel on the Stratospheric Observatory For Infrared Astronomy, he leapt at it.
It was as if I’d become trapped in a cold, noisy, enormous, and super hi-tech elevator, filled with row upon row of technical equipment – including a telescope. The elevator was a 747 aircraft, converted into a flying astronomical observatory, and I was on-board for a 10-hour adventure together with 30 experts from all walks of life.
No ordinary long-haul flight, this was SOFIA, the Stratospheric Observatory For Infrared Astronomy. An observatory built into a wide-bodied jumbo jet, its showpiece is a 2.5-metre-diameter optical telescope that peers through the veils of interstellar dust, which block visible light, to discover what lies hidden out there.
SOFIA, a partnership between Nasa and the German Aerospace Centre, studies cosmic objects, including asteroids in our solar system, nearby planetary systems similar to our own, supernovae, our galactic center, and extragalactic objects with massive black holes. While in New Zealand this winter, it is the largest optical telescope in the country; the next largest being the 1.8 meter telescope at the Mount John Observatory located by Lake Tekapo, South Island.
I had leapt at the chance to join the flight as a guest of the US embassy. Our flightpath took us within 1000km of the Antarctic ice shelf near Oates Bank, Buell Penninsula and the Anare Mountains. We came within 300km of the Antarctic Circle, that region where the sun never sets in summer, nor rises in winter.
The mission began with a briefing at the US National Science Foundation Antarctic Program Base in Christchurch. We underwent three hours of welcoming, flight over-viewing, safety training and mission briefing, before we finally boarded SOFIA’s 747 jet which lifted off in the early evening.
I was struck by just how carefully choreographed the flight and science crews amid a frantic 10 hours. They were constantly moving, constantly collaborating, analysing data in real-time, making decisions on-the-fly, all focused on their particular tasks yet all collaborating to maximize detections of cosmic emissions from molecules, atoms and ions. This includes carbon and oxygen and excited multi-atom molecules including carbon monoxide.
It has been said that “God made beer because he loves us and wants us to be happy”. Well, it turns out that those working in infrared astronomy, like SOFIA scientists, have discovered many of the chemical ingredients of beer in space, including massive quantities of the nine-atom molecule ethanol. Another curious find is Buckminsterfullerenes, one of the largest molecules discovered in space, containing 60 atoms and shaped like a soccer ball (only a billionth of a metre in size).
The conversations with the other guests on board, including the American ambassador and the transport minister Simon Bridges, were riveting. One was Alexia Hilbertidou, a sharp 18-year-old who founded GirlBoss – “to inspire New Zealand girls to become change makers of the future through STEM (Science, Technology, Engineering, and Mathematics) fields.”
She is a rising star, who inspires any crowd lucky-enough to hear her call for gender-challenging transformations in science within New Zealand society.
Shouting above the roar of the minimally insulated SOFIA jet, Chris Duggan, founder of House of Science, shared with me how she brings hands-on scientific explorations to New Zealand secondary schools. She accomplishes this through the development and distribution of science kit for young people to facilitate their exploration through direct engagement.
Dr Peter Crabtree’s background in the history, philosophy and psychology of science is the kind of intellect one rarely comes across in the world of practicing scientists. It is easy to find ourselves overly focused on meeting quotas called for by PBRF (NZ Performance Base Research Funding), where fabulously clever people attempt to engineer, commodify, corporatise, and optimise science.
To me, that is not, however, the essence of science. Science is about curiosity driven by novelty, breaking with convention, and asking questions like, “but how could it possibly be that way!?” No pioneer ever progressed by adhering unerringly to the rules; science progresses by those who break rules. Once something comes to be understood in some novel way that helps people see connections between ideas/objects/processes that were not recognized before, it then ceases to be science. Instead, such a breakthrough often moves into the realm of engineering, where great things are then engineered. Examples of this include modern electronics based on semi-conductor technology.
The end, however, is now in sight for this technology, and a new frontier is opening called quantum computing, which leverages the very failures of this aging technology as it attempts to engineer ever smaller transistors (logic gates) with increasing problems..
My own study explores the physics of giant (Rydberg) atoms in the cosmos, where the average density of matter between stars is a spacious 1 atom per cubic centimeter. We at AUT’s Institute for Radio Astronomy and Space Research have collected and analyzed spectroscopic data from the great nebula in Orion using AUT’s radio telescopes in Warkworth and the Australia Telescope Compact Array. Our findings have solved a puzzle in the field of radio recombination lines published by a Canadian astrophysics group nearly two decades ago.
Our findings also inform the rapidly expanding field of quantum computing, where groups of laser-manipulated Rydberg atoms are now being finessed into logic gates, the bedrock of modern computers. Such solutions will revolutionize, for example, how we build next-generation transportation systems, hunt for planets and life on other planets, and simulate life and intelligence as we know it and as we can imagine it.
About eight hours into the SOFIA flight, the flight crew suddenly told us to return to our seats and buckle-up. There was growing concern by the pilots that the weather conditions around Christchurch, were deteriorating and they were considering re-routing to Auckland.
I got chatting with Simon Bridges, as we huddled in that cold and noisy scientific steel tube travelling at 80 per cent the speed of sound. He began by asking me where I was from. Henderson Valley, West Auckland, I said. He chuckled – he is originally from West Auckland and my accent is a dead giveaway that I am not exactly a born Westie.
We shared how our childhoods were both spent exploring the bush, he in the wild West Coast of the Waitakare Ranges, at Bethels, Piha and KareKare and me at 9,000ft in the high mountain desert of the Sangre de Cristos of Northern New Mexico, near the town of Taos, named after the local Taos Pueblo Indians-part of the Southern Rocky Mountains in the United States.
We talked about religion: we were alike in feeling a spiritual dimension – though not in the sense of organised religion, in my case. The more I explore the cosmos scientifically, I told him, the more I wonder, “but how can it possibly be that way!?”, “how did we even get here”, and “where is everybody else”?
We landed at 4am into a deep fog. Shuffling, bleary eyed but imbued with wonder, like coming out of night club into the dawn, we took our final pictures of the magnificent aircraft and made our way off the NSF Antarctic Program Base onto Orchard Street, as if we had fallen out of space.
Jordan Alexander is lecturer in Physics and Astronomy at AUT
The Spinoff’s science content is made possible thanks to the support of The MacDiarmid Institute for Advanced Materials and Nanotechnology, a national institute devoted to scientific research.
The Spinoff Weekly compiles the best stories of the week – an essential guide to modern life in New Zealand, emailed out on Monday evenings. | 0.853603 | 3.26933 |
Photo: Is this what we’re seeing around KIC 8462852 a colossal megastructure built by alien intelligence? Probably not. The reality might be even more interesting. Kevin Gill/Flickr, CC BYSA
For the past few days, the media has been abuzz with one of the most peculiar astronomical observations for many years. As described in a recent paper on the arXiv preprint service, a faint star in the northern constellation Cygnus has been seen acting incredibly strangely.
The star, KIC 8462852 – somewhat hotter, younger and more luminous than our sun – was observed by the Kepler spacecraft for over four years, 24 hours per day, 365 days a year, along with more than 100,000 other stars in the same patch of sky.
Kepler was designed to monitor the brightness of those stars with exquisite precision, looking for tell-tale tiny “winks” that would indicate that they were orbited by planets.
And Kepler has found planets in abundance; more than 1,000 to date, with more being confirmed all the time.
But in the case of this faint star in Cygnus, it has found something else. Something unexpected. And we still have no idea what it is.
Some commentators have even suggested that the observations might represent the discovery of advanced alien life!
That might be something of a stretch, but it is certainly true to say that the current observations have astronomers baffled. But that isn’t a bad thing.
Many of the greatest and most exciting discoveries in astronomical history were unexpected and serendipitous, and ended up greatly revolutionising our understanding of the universe. Usually, such discoveries were made as new or improved technology allowed astronomers to study the sky in new ways, or in more detail.
That’s exactly what’s happened here, with KIC 8462852. It’s purely because of the unique ability of Kepler to study hundreds of thousands of stars continually for years at a time that the unusual behaviour was found.
Here are just three examples of how serendipity has driven astronomical understanding:
In 1781, using a homemade telescope Sir William Herschel discovered Uranus while scouring the sky looking for double stars. In one fell swoop, Herschel’s discovery doubled the radial scale of our solar system, and gave birth to the search for other planets. The chance find eventually led to the discovery of Neptune, through its gravitational pull on Uranus.
The idea that there could be more planets in our solar system also led to the scouring of the sky that found the first asteroids in the early 1800s. The first asteroid found (Ceres) was another serendipitous discovery!
Although some astronomers were searching for objects between the orbits of Mars and Jupiter, Giuseppe Piazzi was instead constructing a new catalogue of stars. As he scoured the sky, he stumbled on the faint moving asteroid, purely by chance.
From those humble beginnings, we now know of hundreds of thousands of asteroids orbiting between Mars and Jupiter. We have also found tens of thousands of similar small bodies further from the sun (the planetary Trojans, and the trans-Neptunian objects).
Our knowledge of these objects, their distribution and their sizes, has been an incredible boon to scientists trying to disentangle the story of our solar system’s formation and evolution.
In the early 1960s, there was great debate over the origin of the universe. The two leading theories – the Big Bang and Steady State models – had been developed in response to the observed expansion of the universe (another serendipitous discovery, in the early part of the 20th century, by Vesto Slipher and others).
Theorists studying the two models were striving to make predictions of what we might observe in each case. A number of scientists had pointed out that if the universe had been created in a Big Bang, and was once smaller, denser and hotter than it is today, then a relic of that heat should be observable to the current day.
As a result, astronomers at Princeton University were in the process of preparing a survey to search for that “relic radiation”. At the same time, just down the road, Arno Penzias and Robert Wilson were testing a new 6m horn antenna radio telescope.
That telescope was highly sensitive, and Penzias and Wilson were attempting to characterise its performance, and to remove known sources of interference so that it could be used to maximum effect.
They first cooled their detector, using liquid helium, to just four degrees above absolute zero. They then processed their data, removing all traces of known interference.
But one signal remained: a persistent background noise that was present no matter where in the sky the looked, or whether they were observing at night or during the day.
They considered a variety of different sources of noise that could cause the signal. They even, famously, cleaned the horn of guano deposited by pigeons nesting in the antenna. But none of this got rid of the signal. The only conclusion that remained was that it was extra-terrestrial, but the two were still flummoxed.
As it turned out, they had accidentally discovered what is now known as the microwave background – the thermal radiation left behind by the Big Bang. Their accidental discovery netted them a Nobel Prize, in 1978, and in many ways gave birth to modern observational cosmology!
In July 1967, a talented young PhD student at Cambridge University was carrying out observations using a new radio telescope, the Interplanetary Scintillation Array. Jocelyn Bell (now Dame Jocelyn Bell Burnell) was undertaking a painstaking analysis, by eye, of vast reams of data traced out by the telescope as it scanned the sky.
As she scanned through her data, she spotted an incredibly regular pulsating signal that was tracking with the background stars across the sky. Like the observations of KIC 8462852, the signal initially defied all explanation.
Such regular radio pulses, originating from a single point in the night sky, were totally unexpected. The “clock” was ticking once every 1.33730208831 seconds, more regularly than clockwork.
As they tried to understand the nature of the signal, Jocelyn and her PhD supervisor, Anthony Hewish (who was eventually awarded the Nobel Prize for his part in the discovery), considered several possible origins, including speculative thoughts that it just might be an extra-terrestrial signal (though they thought that unlikely).
Once their observations were published, theoreticians elsewhere quickly realised that the best explanation for the unexpected signal was in fact purely natural. The source was not “little green men”. Instead, it was something almost more fantastical: the dead core of a star more massive than the sun, left behind by an ancient supernova explosion.
That object, a neutron star, was smaller than a city, and the pulses were the result of hot spots on its surface, flicking across our view each time the star completed a single revolution on its axis. The object was a pulsar, and a new branch of astronomy was born.
All of this brings us back to our latest big news story. Over the past few years since it was first observed by Kepler, KIC 8462852 has exhibited occasional, short lived, dips in brightness. So far, that’s how every Kepler story starts.
But with KIC 8462852, the dips are different. When a star is transited by a planet, a tiny fraction of that star’s light is blocked, and we see a dip in its brightness. The bigger the planet, the bigger the dip in brightness, and the easier it is to spot.
But where a planet like Jupiter, the solar system’s largest planet, would cause the sun to dim by just ~1% as it passed between us and our star, the dips seen for KIC 8462852 are huge: the largest being 15% and 22% of the star’s light, fading out, then brightening again.
That, in itself, is weird. But there’s more. For a planet, the winks generated would be periodic: one orbit, one wink.
Here, and by contrast, the dips in KIC 8462852’s brightness are not periodic. The two largest occurred roughly 730 days apart, but smaller dips have also been seen. And the most recent large drop (22% of the stars light) was followed by two other, smaller dips over the month that followed.
Added together, it is clear something very strange is happening. No star has ever been observed behaving like this before. And so speculation has run rife as people attempt to explain this new and unexpected behaviour.
The short answer here is: we don’t know. At least, not yet. The authors of the paper on arXiv suggest the most likely explanation could be a cloud of comets, disintegrating as they orbit the star.
Such events are known to occur around the sun, so this idea isn’t entirely outlandish.
The Kreutz family of sun-grazing comets, which include some of the most spectacular comets in recorded history, have a long fragmentation history, and may be linked to a parent that was over 100km across, just a few thousand years ago.
The Taurid debris stream is all that remains of another giant comet, thought to have fragmented tens of thousands of years back. It delivers upwards of 50% of all the dust falling on Earth, and includes the famous comet 2P/Encke. It is so vast that it is encountered by all the terrestrial planets, and Earth spends almost six months of every year traversing it.
So comet fragmentation can occur. But even with a colossal cometary collapse, it is hard to imagine how fully 20% of a stars light would be obscured. Add to that that such a collapse should produce a vast quantity of dust, which will make the star shine brightly at infrared wavelengths, which is something we simply do not see.
So what else could it be?
Perhaps it is a young planetary system, and two of the planets just collided? That would create a huge amount of dust, which again could obscure the light from the star.
But once again, we come back to the problem of infrared light. So much dust would give the star a huge infrared excess, absorbing its visible radiation, getting hot, and re-radiating it beyond the visible. That simply isn’t seen.
So we come to the most speculative suggestion, and the reason that this faint star has attracted so much attention over the past week or so. What if the dips in brightness aren’t natural? Maybe they’re caused by a giant mega-structure built, or under construction, by intelligent advanced aliens.
Could the dips be explained by something like a partial Dyson sphere? Giant structures like this pervade science fiction and are the signature of species with technology immeasurably beyond our own.
Well, it’s certainly possible, but I wouldn’t place bets on it just yet! Extraordinary claims like this require extraordinary evidence, and astronomers will be studying KIC 8462852 for years to come, trying to disentangle the mystery.
Personally, my money would be on this being something akin to the discovery of the first pulsar: unexpected, and unexplained as of yet, and opening a door to a new process or kind of object previously unknown. Not life, but something almost as interesting: new science! | 0.957952 | 3.682208 |
The number of satellites in orbit is about to sky-rocket, and that could have serious consequences for astronomers, according to a new study.
In a race to provide low-cost internet to remote areas, companies like SpaceX are crafting plans to launch satellite “mega-constellations” — groups of satellites that communicate with one another — that enable the broadband technology.
It was widely reported last year that SpaceX alone had secured approval to launch 12,000 satellites as part of its StarLink constellation, pending approval of another 30,000.
That’s a sharp jump from the 5,500 satellites currently in orbit, which are tracked by the European Space Agency.
Other companies like Amazon and the U.K.-based OneWeb, have plans to launch thousands of their own satellites.
Now, new research from the European Southern Observatory (ESO), an astronomical research group, is raising an alarm about how these objects could disrupt ground-based observations of the night sky.
The study, which will be published in the journal Astronomy and Astrophysics, looked at 18 satellite constellations under development worldwide, assuming a total of 26,000 satellites — a “conservative” estimate based on publicly available information.
It found that the greatest impact would be on wide-field surveys conducted by large telescopes, such as the Vera C. Rubin Observatory in Chile. It says 30 to 50 per cent of their exposures could be “severely effected,” depending on the time of year.
“These are engines of discovery for astronomy,” Andrew Williams, a co-author of the study told Spoke.
Wide-field surveys are often used to find points of interest, such as stars or galaxies, that merit further research, he explained.
Other large telescopes ESO uses to focus on small points of the sky would only have about 3 per cent of their exposures affected during twilight hours.
The study notes satellites can also be visible to the naked eye just before sunrise and after sunset when they are illuminated by sunlight, which has prompted many astronomers to brand them as a form of light pollution.
“For the average person, the problem of light contamination from satellites is nothing compared to the problem of light contamination just from other sources like cities,” Williams said.
But while it’s possible to escape light contamination by moving to a remote location or with special filters, satellites are a virtually permanent fixture, he said.
To lessen the impact of satellites, ESO says they can change the operating hours of their telescopes, although that comes at a price. They suggest the aerospace industry should also work to darken satellites.
At a March 9 conference in Washington, D.C., SpaceX founder Elon Musk said that the company’s satellites wouldn’t impact astronomical discoveries.
Although it wasn’t in the study itself, Williams says that the lack of international rules surrounding the nature of satellites contributes to the problem.
“How big it is, how bright it is, this is not regulated at all,” he explained.
“There is no law an astronomer can turn to.”
The study notes that more research needs to be done to precisely quantify the impacts on astronomy, because it is based on several simplifications and assumptions, such as the total number of satellites that will be in orbit in the near future.
It’s also only valid for satellites that operate at low- to mid-latitude — about 30 degrees from the horizon.
Further studies will also need to be done to find the effects on different kinds of telescopes. | 0.848991 | 3.479795 |
New image of comet ISON
This new view of Comet C/2012 S1 (ISON) was taken with the TRAPPIST–South national telescope at ESO's La Silla Observatory on the morning of Friday 15 November 2013. Comet ISON was first spotted in our skies in September 2012, and will make its closest approach to the Sun in late November 2013.
TRAPPIST–South has been monitoring comet ISON since mid-October, using broad-band filters like those used in this image. It has also been using special narrow-band filters which isolate the emission of various gases, allowing astronomers to count how many molecules of each type are released by the comet.
Comet ISON was fairly quiet until 1 November 2013, when a first outburst doubled the amount of gas emitted by the comet. On 13 November, just before this image was taken, a second giant outburst shook the comet, increasing its activity by a factor of ten. It is now bright enough to be seen with a good pair of binoculars from a dark site, in the morning skies towards the East. Over the past couple of nights, the comet has stabilised at its new level of activity.
These outbursts were caused by the intense heat of the Sun reaching ice in the tiny nucleus of the comet as it zooms toward the Sun, causing the ice to sublimate and throwing large amounts of dust and gas into space. By the time ISON makes its closest approach to the Sun on 28 November (at only 1.2 million kilometres from its surface — just a little less than the diameter of the Sun!), the heat will cause even more ice to sublimate. However, it could also break the whole nucleus down into small fragments, which would completely evaporate by the time the comet moves away from the Sun's intense heat. If ISON survives its passage near the Sun, it could then become spectacularly bright in the morning sky.
The image is a composite of four different 30-second exposures through blue, green, red, and near-infrared filters. As the comet moved in front of the background stars, these appear as multiple coloured dots.
TRAPPIST–South (TRAnsiting Planets and PlanetesImals Small Telescope–South) is devoted to the study of planetary systems through two approaches: the detection and characterisation of planets located outside the Solar System (exoplanets), and the study of comets orbiting around the Sun. The 60-cm national telescope is operated from a control room in Liège, Belgium, 12 000 km away.
À propos de l'image
|Date de publication:||18 novembre 2013 11:00|
|Taille:||1957 x 1925 px|
À propos de l'objet
Couleurs & filtres | 0.842874 | 3.823266 |
On March 18, 1965, Soviet cosmonaut Aleksei Leonov became the first person to walk in space. Find out five other fascinating things you probably didn't know about our universe...
The Moon Is Moving Farther Away From Earth The moon is moving 3.8 cm (about 1.5 inches) farther away from the Earth every year. The increasing distance is caused by tidal movement on Earth, which slows the Earth’s rotation and makes the moon expand its orbit. At this rate, about 50 billion years down the road, the Earth’s rotation would be every 47 days, but since the Sun will be a red giant by then, there’s nothing to worry about because it may have swallowed up both the Earth and moon.
Voyager I Is the Farthest Operational Man-Made Object Voyager I, the NASA space probe, has been traveling through outer space to collect data since 1977. It was launched at an unusual period when the four outer planets were aligned, an event that only occurs every 176 years. Voyager I in its journey has sent amazing close-up photos and data on Neptune, Uranus, Saturn, and Jupiter. In 2012, it became the first spacecraft to leave the solar system and enter the interstellar medium.
Days on Earth Are Getting Longer While it might seem that the years go by more quickly to some, days on Earth are actually getting longer because the planet’s rotation is slowing. It isn’t time to panic yet because a day only lengthens about 1.8 milliseconds every century. The longer days are due to the moon pulling away at the speed of a snail. The moon's gravity causes a tidal "bulge" on Earth, and the bulge attempts to rotate at the same speed as the rest of Earth. As the tidal bulge moves forward, the moon's gravity attempts to pull it back, slowing the Earth's rotation ever so slightly.
Mars Has A Mountain Bigger Than Everest
Mars holds the title of having the solar system’s largest mountain with the impressive Olympus Mons, which boasts a height of 16 miles. This is around three times taller than Mt. Everest. Olympus Mons is so wide, 340 miles, that it would cover an area bigger than all the Hawaiian islands. It was created by lava eruptions and has a low profile, being very flat with gentle slopes.
The Sun is Really Far Away We all know that the Sun is the star that all the planets in the Solar System revolve around. You might think that the Earth is relatively close given that it just takes just 365 days to make one orbit, but you’d be wrong. The Earth is a whopping 93 million miles from its star. A distance so far that it takes light itself over 8 minutes to reach Earth. It would take a driver traveling at 65 mph an astonishing 163 years to drive to the Sun. | 0.88358 | 3.302474 |
The first black hole we have ever directly imaged now has a nickname – but astronomy’s governing body says it will take a while to make it official.
Pictures of the supermassive black hole were unveiled on Wednesday by the Event Horizon Telescope (EHT), a global network of eight telescopes that turned Earth into one giant radio telescope.
The black hole, 55 million light years away at the centre of the galaxy M87, has been dubbed “Pōwehi” by Hawaiian language professor Larry Kimura, in collaboration with Hawaii-based astronomers involved in EHT.
Fittingly, “Pōwehi” means “embellished dark source of unending creation”. The name originates from the Kumulipo, an 18th-century Hawaiian chant that describes a creation story.
Conventionally, the official naming of objects in the universe is managed by the International Astronomical Union, which has done so since 1919.
“Objects are split into different categories such as surface features of objects in the solar system, or stars,” says the IAU’s Lars Christensen.
Naming celestial objects is occasionally a source of controversy. For example, the dwarf planet Haumea was disputed for years before a name was finally chosen, because two teams claimed to have discovered it.
“Typically discoverers of objects propose a name to a working group, who then vets the name and checks for various issues like duplication or political meaning,” says Christensen.
The names of these objects differ from “designations”, which are similar to a catalogue of numbers. For example, the interstellar object known as ‘Oumuamua has a designation 1I/2017 U1.
Black holes don’t have consistent naming conventions, but are often given the designation of their host galaxy.
“For the case of M87*, which is the designation of this black hole, a (very nice) name has been proposed, but it has not received an official IAU approval,” says Christensen.
“There is so far no working group who has been delegated with [the] naming of such objects, as this is the first in its class,” he says. “Typically these things take quite a while.” | 0.912574 | 3.129986 |
We’re finally getting to know the icy nucleus behind comet 67P/Churyumov-Gerasimenko. For all the wonder that comets evoke, we on Earth never see directly what whips up the coma and tail. Even professional telescopes can’t burrow through the dust and vapor cloaking the nucleus to distinguish the clear outline of a comet’s heart. The only way to see one is to fly a camera there.
Rosetta took 10 years to reach 67P/C-G, a craggy, boot-shaped body that resembles an asteroid in appearance but with key differences. Asteroids shown in close up photos often display typical bowl-shaped impact craters. From the photos to date, 67P/C-G’s ‘craters’ look shallow and flat in comparison. Were they impacts smoothed by ice flows over time? Did some of the dust and vapor spewed by the comet settle back on the surface to partially bury and soften the landscape?
While 67P is doubtless its own comet, it does share certain similarities with Comet 81P/Wild including at least a few crater-like depressions seen during NASA’s Stardust mission. In January 2004, the spacecraft gathered photos, measurements and dust samples during its brief flyby of the nucleus. Photos reveal pinnacles, flat-bottomed depressions and bright plumes or jets of vaporizing ice.
In a 2004 paper by Donald Brownlee and team, the group experimentally reproduced the flat-floored craters by firing projectiles into resin-coated sand baked a bit to make it cohere. Their results suggest the craters formed from impacts in loosely compacted material under the low-gravity conditions typical of small objects like comets. To quote the paper: “Most disrupted material stayed inside the cavity and formed a flat-floored deposit and steep cliffs formed the rim.” Icy materials mixed with dust may have also played a role in their appearance and other crater-like depressions called pit-halos.
Speculation isn’t science, so I’ll stop here. So much more data will be streaming in soon, we’ll have our hands full. On Wednesday, August 6th, Rosetta will enter orbit around the nucleus and begin detailed studies that will continue through December 2015. Studying the new pictures now arriving daily, I’m struck by the dual nature of comets. We see an ancient landscape and yet one that looks strangely contemporary as the sun vaporizes ice, reworking the terrain like a child molding clay. | 0.816559 | 3.905139 |
Imagine standing upon a barren world billions of light-years from Earth. In the sky overhead is not a brilliant Sun, but a supermassive black hole. While this seems like a scene out of science fiction, new research1 has found that such a “black hole world” could exist.
Planets commonly form around young stars. As a star is born within a stellar nebula, a disk of gas and dust forms around the star. Some of the dust in this disk clumps to form young planets, and over time the heat of the star clears the region leaving a system of exoplanets orbiting the star.
Accretion disks of gas and dust also form around supermassive black holes. For very active, quasar-like black holes, so much light and heat is produced that the accretion disk is too hot for planets to form. But for less active black holes, known as low-luminosity Active Galactic Nuclei (AGNs) a dusty torus of gas can form, similar to the protoplanetary disks around young stars.
A team recently looked at this idea and found that low-luminosity AGNs could provide their surrounding disks with just enough heat to allow dust particles to collide. Over time the clumps would form into planets that could be ten times more massive than Earth. How quickly planets could form is dependent on the mass of the black hole. For a black hole similar to the one in our galaxy, the timescale is on the order of 100 million years.
Based on their calculations, a supermassive black hole could have tens of thousands of planets orbiting it, several light-years from its event horizon. If that’s true, then supermassive black holes could be home to the largest planetary systems in the universe.
Of course, detecting these black hole exoplanets is impossible for now. They are too small and dim to observe using current instruments. But if they are out there, some clever astronomers will figure out a way to find them in time.
Wada, Keiichi, Yusuke Tsukamoto, and Eiichiro Kokubo. “Planet Formation around Super Massive Black Holes in the Active Galactic Nuclei.” arXiv preprint arXiv:1909.06748 (2019). ↩︎ | 0.883584 | 3.829204 |
Meteor shower! The very words conjure up a picture of flaming fireballs of fury flashing frenetically against the night sky.
Actually, the reality is quite different most of the time.
The Perseids peak on Thursday morning, Aug. 13, during the hour right before morning twilight. You might see as many as 100 streaks — most of them faint — per hour if you observe at exactly the right hour on exactly the right date under a dark rural sky and if it’s crystal clear that morning. You’ll still see plenty of meteors if you observe the morning after or the morning before, but your experience won’t be as good. More on that later. First, a bit of background.
Early peoples believed that meteors were stars that fell from the sky, perhaps dislodged by a high wind. As the great Roman poet Virgil wrote,
Oft you shall see the stars, when wind is near,
Shoot headlong from the sky, and through the night
Leave in their wake long whitening seas of flame.
Actually, that’s not a bad description of what a bright meteor looks like as it streaks across the sky.
Of course, meteors really aren’t “shooting stars.” They are pieces of dust and debris in space that enter the earth’s atmosphere. As they hit the atmosphere, they burn up, leaving a streak of light. Most of the pieces are no bigger than a grain of dust, so meteor showers are not known for their bright fireballs. Mostly you’ll see relatively faint streaks of light, lasting for a second or so.
Any moonless night is a good time to observe meteors. Even without a scheduled shower, you’ll see a few meteors an hour if you’re observing from a relatively dark rural site.
What makes meteor showers interesting is the frequency of those streaks of light.
Meteor showers are caused when Earth passes through a cloud of space debris left by a passing comet, thus increasing the amount of junk that enters the earth’s atmosphere.
Still, most of the yearly meteor showers are weak. They increase the total number of meteors by only a few an hour. The Perseids are the yearly exception with 100 streaks during the last hour before morning twilight on their peak morning.
Meteor showers are best observed on moonless nights away from cities. Both the moon and the glow from city lights wash out these faint steaks of light. Luckily, this year the Perseids peak on a moonless night.
Showers are best observed after midnight as our side of the planet turns into the direction Earth’s orbit around the sun. When that happens, meteors don’t have to play catch up with the earth’s rotation. They are now plummeting headlong at Earth, so we see more of them.
To put it another way, Earth is plowing into the debris cloud like your car plowing through a swarm of bugs. The “after midnight” effect is like bugs hitting your windshield, as my good buddy and observing partner Biff Smooter likes to point out. You only get bugs on your front windshield, the direction that the car is moving.
Observing before midnight is like looking out your back windshield. You won’t see as many meteors that way. Just as bugs have a hard time catching up to the speed of your car, meteors have a hard time catching up to the speed of the Earth.
Showers like the Perseids get their name from the constellation from which they seem to originate. However, that doesn’t mean you have to look in the direction of Perseus to see them. They will appear all over the sky. Your best bet is to look in the direction away from the glow of city lights. If you are observing from north of Columbus, for example, you should look to the south.
Meteor observing requires very little equipment. I’d suggest a lawn chair and a blanket. It often gets fairly cold at 3 a.m., especially if you’ve been sitting unmoving in a lawn chair for three hours. Also, take along a gallon of bug repellent. The mosquitoes are as big as buffaloes this year.
As many as a trillion pieces of space junk enter the atmosphere daily. If they are bigger than a pebble, they create a beautiful, fiery streak across the sky that may change colors, or even flake off bright pieces and explode. They often leave a faint trail of ionized gas that is visible for several seconds after the meteor has disappeared. These infrequent, but memorable, meteors are called fireballs, or bolides. They are the kind of event you’ll remember for the rest of your life.
Some of the debris is man-made. More than a few years ago, a dozen members of the local astronomy club and I were lucky enough to see the second stage of a Russian rocket come burning into the atmosphere. It took several minutes for it to move slowly across half the sky and flaked bright pieces away from itself. It’s worth going observing hundreds of times just to see something like that happen once, and we didn’t need to have a meteor-shower night to make it happen.
While you are sitting there, enjoy the starry sky. The Milky Way is overhead. The sheer beauty of the night sky is reason enough to lie outdoors in silence, drinking in the universe with your eyes.
Tom Burns is director of the Perkins Observatory in Delaware. | 0.802002 | 3.836413 |
Monday, January 17 – Before dawn this morning, try having a look for Mars and red Antares on the rise. The first precise observation of Mars’ position dates back to this day in 272 BC, but was observed by Aristotle as early as 356 BC. So what’s the significance of looking? Translated, Alpha Scorpi – or Antares – means “rival of Mars”. Did you know Mars was originally named Ares? So “Antares” quite literally means “not Mars”. As you look for our ruddy points of light this morning, take hope. Antares will rise four minutes earlier tomorrow morning, and every day afterwards. Being able to sight a “summer star” can only mean winter for the Northern Hemisphere is getting shorter by 240 seconds every day!
While you are out, be sure to keep a watch for the Coma Berenicids meteors. This widely varied stream is still producing around one to two meteors per hour, and they are among the fastest meteors known – reaching speeds of up to 65 kilometers per second!
And since we’re “early to rise”, let’s head for an “early to bed” as we celebrate American scientist, Benjamin Franklin’s 299th birthday with an early evening observation of the seven-day old, first quarter Moon. Tonight’s outstanding feature will be the Alpine Valley. Located tonight near the terminator in the northern lunar hemisphere, this wonderful “gash” very conspicuously cuts across the lunar Alps just west of crater Aristotle. As you view this 180 km long and (at points) less than 1 km wide feature, ask yourself how it was formed. Perhaps an asteroid once sliced its way through the forming region? Even science doesn’t have a perfect answer for this one!
Tuesday, January 18 – Let’s return again to the Moon tonight to explore. The most prominent feature distinguishable in binoculars and small telescopes will be the rather blank looking oval of crater Plato, but the feature we’re really interested in is just south – Mons Pico. Appearing as an almost “star-like” point of light to binoculars, telescopes will enjoy this singular mountain for the long shadow it casts on the barren lunar landscape. No doubt comprised of white rock that has high reflecting power, Mons Pico will appear to look almost like a pyramid alone on the grey sands on Mare Ibrium. With an estimated height of 2400 m, this particular lunar feature will be lost over the next few nights. How long can you follow it?
One hundred years ago today, the United States bought their first airplane from the Wright Brothers – perhaps tonight we’ve found it?
Wednesday, January 19 – Head’s up for the United States and Southern Canada. Tonight the Moon will occult 4.4 magnitude Delta Aries! Timing for these type of events is very important so please visit this IOTA page for precise times and locations. If you have never watched a lunar occultation, I highly recommend it. Even binoculars can reveal the event and there is something very exciting about witnessing a star wink out!
Scottish engineer, James Watt was born on this day in 1736. We know my famous forefather held the patent for improvements on the steam engine, but did you know that James Watt was the first to use a telescope in surveying? Tonight let’s celebrate the date of his birth by surveying one of the most impressive features on the Moon – Clavius. As a huge mountain-walled plain, Clavius will appear near the terminator tonight in the lunar southern hemisphere, rivaled only in sheer size by similar structured Deslandres and Baily. Rising 1646 meters above the surface, the interior slopes gently downward for a distance of almost 24 km and span 225 km. Its crater-strewn walls are over 56 km thick! Clavius is punctuated by many pockmarks and craters, the largest on the southeast wall is named Rutherford. Its twin, Porter, lay to the northeast. Long noted as a “test of optics”, Clavius crater can offer up to thirteen such small craters on a steady night at high power. How many can you see? (If you think that’s tough, see if you can spot the Pleiades only two degrees away unaided!)
Thursday, January 20 – We would like to wish Buzz Aldrin a very happy 75th birthday! For those of us who enjoy studying the lunar surface, we can never look without hearing Aldrin’s description of “Magnificent desolation.” It is this kind of bravery and dedication to exploration that inspired us all! So let’s look tonight…
The ten-day old Moon will offer many features such as the fully disclosed Tycho, the incomparable Copernicus and the fascinating Bulliadus, but tonight we’ll be looking for an asterism – “The Great Wall”. By drawing a mental line from Tycho to Copernicus, extend that line by two-thirds the distance north. It is here that you will discover what looks like huge wall on the lunar surface – and at some 48 km high and 161 km long, that would be a great wall! In fact, it is nothing more than the western portion or the Juras Mountains which surround the lovely Sinus Iridum – but it’s definitely a rather striking feature and well worth the time to look in both binoculars and telescopes. Klare nacht!
Also born on this day in 1573 was Simon Mayr. He also observed the moons of Jupiter at nearly the same time as Galileo. Although Jupiter’s many satellites are known as “galilean moons”, it was Mayr who assigned them the Greek names we still use today. For many of us, Jupiter rises far too late for observation, and is often clouded out in the mornings – but did you know that you can listen to Jupiter as well? Visit with my friends at Radio JOVE for both real-time audio as well as information on how to acquire a Radio JOVE receiver of your own! Enjoy…
Friday, January 21 – How about if we try to ignore the Moon tonight and instead search for Comet C/2004 Q2? Unaided-eye detection will be next to impossible, but we’re in luck as the “Magnificent Machholz” will be only three degrees above Alpha Persei. Making its closest approach to the Sun in just a few days, spotting Comet Machholz’ dust tail with so much moonlight will be a real challenge – but at my last observation the ion tail was so strong it just might show! Having passed closest to the Earth earlier this month, Comet Machholz is delighting viewers with clear skies world-wide. On its way to becoming a circumpolar object, this great comet will make a wonderful sight in binoculars with 1.8 magnitude Mirfak in the same field. If you plan on using a telescope, be sure to take the time to study this giant star as well! As the senior member of the Alpha Persei group, this particular star is around 4000 times more luminous than our own Sun and is about 570 light years away. If you are able to discern the other bright stellar members of this group, make note of their position! They might not be cruising quite so fast as Comet Machholz, but they will have changed positions in the sky by around one degree in say… 90,000 years? Just a cosmic sneeze!
On this day in 1792 , John Couch Adams, the man who predicted the existence of Neptune. was born and he shares the same birthday as Bengt Stromgren, who came into the world in 1908. Stromgren was the developer of the theory of ionization nebulae. Why not recognize his achievements by visiting an H II region tonight that not even the Moon can outdo! Let’s head for the “Great Orion Nebula”… Although a lot of the subtle detail will be lost in the moonlight, to think that we can see such a rare “light” from 1900 light years away is pretty amazing! (And we’ll definitely be back to study.)
Saturday, January 22 – This time of year is best to look for some strange occurrences that are not astronomy-related – but wonderful for SkyWatchers! Thanks to a multitude of high thin clouds and an abundance of ice crystals in our atmosphere, be on the lookout for various forms of atmospheric phenomena. The most common is known as the “sun dog” and will look very much like a mock rainbow that appears in a small portion of the sky near the Sun. Much more dramatic is the “sun pillar”, which will look like a huge column of light towering over the Sun both during rise and set. A lot less common, but certainly inspiring is the “parhelic arc”, which appears as a circular (in whole or part) “rainbow” directly around the Sun. Do these things only happen during the day? No! It is not uncommon on frigid nights to see “light pillars” above distant street lights, or to catch a “moon dog” when conditions are just right. For more information on these fantastic phenomena, as well as some downright awesome photos, please take the time to visit with Atmospheric Optics. It makes the cold months just a little more warm…
If you have a new telescope you’d like to try out and want a lunar feature that’s a bit less obvious, then tonight let’s try for crater contrasts. The Oceanus Procellarum is the vast, grey “sea” that encompasses most of the northwestern portion of the Moon. On the terminator to its southwest edge, (and almost due west geographically) you will see two craters of near identical size and depth, but not identical lighting. The southernmost is Billy – one of the darkest floored areas on the Moon. It will appear to have a bright ring (the crater rim) around it, but the interior is as featureless as a mare! To the north is Hansteen – note how much brighter and more detailed it is. It’s easy to discern that Billy once filled with smooth lava flow, while counterpart Hansteen evolved much differently!
Sunday, January 23 – Tonight the Moon will be at its furthest point from the Earth (apogee), but not far enough to darken skies as its gibbous form appears almost two hours before sunset and reveals Saturn only six degrees away at skydark. Almost an equal distance on the other side of our “near full” Moon are the famous “twins” of Gemini – Castor and Pollux. Aim your telescopes at the northernmost of these stars as we briefly explore Alpha Geminorum!
What we are looking at when we view Castor is six-part star system that is around 45 light years away. In a telescope, only three of these stars are visible. If you look carefully, you will see the primary star is actually a fairly close double, only separated in brightness by about 1 magnitude. Each of these two stars is also a spectroscopic double and their companions orbit within just a few million miles of their primary star in a matter of days. To really understand just how close this system is, imagine our own Sun being twice its size and having a small companion orbiting even closer than Mercury. Somewhere out around Pluto would be an identical sun and companion! Moving elliptically around each other, our pair of doubles takes about 400 years to orbit each other. At closest, we would see a separation of about 1.8 arc seconds, but right now they are about 2.2 arc seconds apart and the gap is gradually widening. In around 50 years from now, this “pair of pairs” will have moved to almost 6.5 arc seconds apart!
If you want an additional challenge, see if you can spot the 9.5 magnitude “orange” C star widely placed southeast of our tight system. It is also a spectroscopic binary that belongs to the same “group”. It’s about two-thirds the size of our own Sun and its identical companion orbits in 24 hours at only about a million and a half miles away. But don’t expect to see them change soon, for it takes this particular pair 10,000 years to orbit 100 AU away the dual primary stars. Perhaps we could find a few “sunny” days there?
And that’s it for now. I sure hope that some of you have had clearer skies than I have! Until next week? Ask for the Moon – but keep reaching for the stars! Wishing you clear skies and light speed… ~Tammy Plotner | 0.890282 | 3.449662 |
micrometer(redirected from µm)
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micrometer(mīkrŏm`ətər, mī`krōmē'tər). 1 Instrument used for measuring extremely small distances. Typical examples are devices used in astronomical telescopes to measure the apparent diameter of celestial objects and similar devices used in microscopes. In both of these devices a fine hair or filament is moved from one extremity to the other of the image of an object and the distance read on a calibrated scale. Another typical micrometer is the micrometer caliper, a device in which an object to be measured is enclosed between two jaws, one fixed and the other movable by means of a fine screw. When the jaws are just touching the object, the distance between the jaws can be read on an associated scale, often to an accuracy of 10−4 (one ten-thousandth) in., or 10−6 (one millionth) m. 2 Unit of linear distance equal to 10−6 (one millionth) m. It was formerly known as a micron.
in astronomy, an instrument for measuring small distances in the focal plane of an astronomical telescope or measuring microscope. The measurement is usually accomplished with the aid of a precision micrometer screw, whose angle of rotation is proportional to the linear displacement, in the instrument’s field of view, of a frame with measuring wires, with the frame being driven by the motion of the screw.
This principle is the basis for the construction of the filar micrometer, which was first used by the French astronomers and geodesists A. Auzout and J. Picard in the second half of the 17th century. Filar micrometers are widely used in optic tubes and measuring microscopes of astronomical and geodetic instruments. A micrometer in which the frame can be rotated in the focal plane so that it is possible to measure not only the distances between the images of celestial bodies in the focal plane but also the position angles of the line joining them is called a position micrometer. Astronomers make use of the registering micrometer, invented by the German instrument maker A. Repsold at the end of the 19th century; this instrument makes it possible to register the moments for some positions of the micrometer wire as it moves across the telescope’s field of view. For good micrometers the errors do not exceed 0.002–0.003 of a screw revolution, and the accuracy of the reading is about 0.5 jam. A spiral micrometer is used when more precise scale readings are required; in this instrument a fine-pitch spiral of Archimedes is visible in the field of view of the eyepiece. By rotating the spiral so that it coincides with the marks on a scale, one can obtain a reading with an accuracy of about 0.1 jam. Some use is made of a micrometer in which the measurements are made by superimposing the two images of an object that are obtained in special prisms made of ordinary or birefringent optical material.
REFERENCESBlazhko, S. N. Kurs prakticheskoi astronomii, 3rd ed. Moscow, 1951.
V. V. PODOBED
ii. A unit of linear measurement equal to one millionth (10−6) of a meter. Also called a micrometer.
iii. The amount of pressure exerted by a column of mercury one-micrometer (one millionth of a meter) high under standard conditions. A micron of pressure is equal to .001 mm of mercury.
micrometer(1) One millionth of a meter. Also known as a "micron." See metric system and micron.
(2) A mechanical instrument that is used to measure diameters and small distances. | 0.826535 | 3.400172 |
Most asteroids orbit the Sun in a counterclockwise fashion, but a newly-discovered object nicknamed Bee-Zed goes against the grain, spinning around the Solar System the opposite way. Not only that, it frequently ventures within Jupiter’s orbital space—putting it on a potential collision course with the gas giant and its 6,000 co-orbiting asteroids.
Of the millions of documented asteroids in the Solar System, a scant 82 of them, or 0.01 percent, orbit the Sun in a retrograde motion. But as a new study in Nature points out, asteroid Bee-Zed, or 2015 BZ509, is exceptional even among these backwards-orbiting misfits. It has the distinction of being the only known retrograde object in the Solar System that shares its orbital plane with another planet, in this case mighty Jupiter.
What makes this celestial anomaly stranger still is that Jupiter is accompanied by 6,000 “Trojan” asteroids, the vast majority of which follow the gas giant in a prograde orbit. Similar to a racecar driver going the wrong way around a track, Bee-Zed is careening towards these objects with each trip around the Sun. According to calculations made by Western University astronomer Paul Weigert, Bee-Zed has been doing this for at least a million years, amounting to tens of thousands of successful “laps” around the Sun. So far, it has emerged unscathed from these close encounters.
Bee-Zed’s success may not be an accident. As noted in the study, Jupiter’s gravity is causing the rogue asteroid to weave in and out of the planet’s path each time the two objects pass. It’s the only asteroid known to have this relationship with a planet, and this state of “synchronicity” should allow Bee-Zed to avoid a catastrophic collision with Jupiter for the next million years at least. This analysis is based on calculations and observations made with the Large Binocular Camera on the Large Binocular Telescope in Mt. Graham, Arizona.
With each orbit Bee-Zed and Jupiter make around the sun, the retrograde object passes once inside and once outside the gas giant. This results in two opposing gravitational nudges that keeps the object on a safe path. Even though Bee-Zed crosses Jupiter’s orbital plane, it never actually gets too close; the nearest the two objects get to each other is about 109 million miles, roughly the distance between Earth and the Sun. So for Bee-Zed, it’s like playing “chicken” with a massive semi-truck—but the space rock only ventures onto its path when the truck is still far, far away.
The asteroid may not smash into Jupiter any time soon, but it’s less clear if Bee-Zed will smash into one of the Trojans.
“We don’t know where all Jupiter’s Trojans are yet so we can’t definitely determine the odds,” Weigert told Gizmodo. “Given their relative sizes and the volume of space they orbit within, the odds are only about 1 in 1 billion of a collision each time BZ goes around its orbit. So the chances of BZ colliding with another Trojan asteroid are small. But the Trojan asteroids don’t have the same ‘dynamical protection mechanism’ that protects BZ from collisions with Jupiter: they just have to trust in luck.”
Not much is known about Bee-Zed, which was discovered by the Panoramic Survey Telescope And Rapid Response System (Pan-STARRS) in 2015. And although astronomers presume it to be a rocky asteroid, they aren’t even entirely sure—it could be an ice-covered comet. In fact, it may have originated from the same place as Halley’s Comet, perhaps the most famous retrograde object in the Solar System.
Correction: An earlier version of this article claimed that some of Jupiter’s Trojans are in retrograde. This is not the case. Aside from Bee-Zed, there are none. Gizmodo regrets the error. | 0.904588 | 3.923558 |
Relocating the human race to a more hospitable planet would mean that multiple generations would be born in-transit
fter 200,000 years or so of human existence, climate change threatens to make swathes of our planet unlivable by the end of the century. If we do manage to adapt, on a long enough timeline the Earth will become uninhabitable for other reasons: chance events like a comet strike or supervolcano eruption, or ultimately — if we make it that long — the expansion of the sun into a red giant in around five billion years, engulfing the planet completely or at a minimum scorching away all forms of life. Planning for potential escape routes from Earth is, if not exactly pressing, then at least a necessary response to a plausible threat.
The most obvious destination is our nearest neighbor, Mars. We’ve already sent multiple probes there, and NASA is planning another moon landing in 2024 with the eventual plan of using it as a waypoint on a mission to Mars. Elon Musk’s Space X claims to be aiming for a crewed trip to Mars in the same year. But Mars is a desert planet, cold and barren, with no atmosphere save for a thin blanket of CO2. Sure, we could survive there, in protective suits and hermetically sealed structures, but it’s not a great place to truly live.
Some scientists have another favorite relocation candidate: Proxima b, a planet that orbits a star called Proxima Centauri, some 4.24 light years distant from our sun. Located in the triple-star Alpha Centauri solar system, Proxima b has a mass 1.3 times that of Earth and a temperature range that allows for liquid water on the surface, raising the possibility that it could support life.
The biggest challenge is getting there. Proxima b is almost unimaginably far away. There is a program underway, Breakthrough Starshot, to send a probe to Alpha Centauri with a journey time of just 20 years, but the entire craft will weigh only a few grams, being propelled by a 100-billion-watt laser fired at it from Earth rather than carrying any of its own fuel or, for that matter, human passengers. Even by generous estimates, traveling one light year in a vessel large enough to transport humans will take centuries; reaching a planet in the range of Proxima b would take a thousand years or more.
This means that no one cohort of crew members would be able to survive the journey from start to finish, so those on the craft for the launch would have to pass on the torch to the next generation, and the next, and the next, and the next.
While it might sound like science fiction, a small network of researchers is tackling the problem of multi-generation space travel in a serious way. “There’s no principal obstacle from a physics perspective,” Andreas Hein, executive director of the nonprofit Initiative for Interstellar Studies — an education and research institute focused on expediting travel to other stars — tells me in a call from Paris. “We know that people can live in isolated areas, like islands, for hundreds or thousands of years; we know that in principle people can live in an artificial ecosystem like Biosphere2. It’s a question of scaling things up. There are a lot of challenges, but no fundamental principle of physics is violated.”
As one might expect from such an undertaking, the difficulties are many and broad, spanning not just physics but biology, sociology, engineering, and more. They include conundrums like artificial gravity, hibernation, life support systems, propulsion, navigation, and many problems that are nowhere near to being solved. But even if we never make it to Proxima b, in the process of exploring the question of how to escape Earth, some of the scientists involved in the work may stumble upon solutions for surviving on our planet, as resources like energy and water become increasingly scarce.
When it comes to traveling beyond our solar system to colonize the planets of a nearby star, the most basic question is whether it’s possible at all on a biological level.
Frédéric Marin, an astrophysicist at the Université de Strasbourg and a global expert on the radiation created by black holes, decided to address this question in a series of research papers produced without funding and in his spare time.
He was inspired to look into the issue by the work of Nick Kanas, a professor of psychiatry who studied NASA crew members to understand the psychological effect of months spent in the International Space Station. Kanas has published many papers and books on the subject, assessing the impact on the human mind of confinement, stress, zero gravity and isolation from Earth. He describes his own work as a precursor to mounting long-duration space missions. This body of research posed questions about whether manned journeys to the outer planets of the solar system and beyond are feasible, and Marin realized that very few people had tried to seriously address the question from a biological and sociological point of view. He also realized that he had the skills to try.
As an astrophysicist, Marin was accustomed to building simulated models of particle interaction in space. He designed a simulation in which each unit would represent not a particle but a human in a closed environment, with a certain probability of living healthily, succumbing to disease, and finally passing on genetic material to the next generation. In turn, humans of the next generation were born with some random attributes, and others based on the “consanguinity” of their parents — how closely related they were. The guiding question was whether an initial crew of a given size would be sufficient to complete a 200-year journey without outgrowing the ship’s capacity, dying off en masse, or arriving with excessive inbreeding. “You can use data from biology, anthropometry, anthropology, mathematics, to compute it,” Marin says. “This is a theoretical step, but it’s the first step.”
In 2017 Marin published a paper unveiling a software system, dubbed HERITAGE, that could simulate the growth of an isolated human population over time to predict whether an initial crew of a given size would be sufficient to complete a journey over multiple generations, and arrive with enough genetic diversity to populate a new planet. In 2018 he and co-author Camille Beluffi, a physicist at scientific data startup CASC4DE, applied the same technique to calculate the crew size needed for travel to Proxima b, estimating that just 98 crew members at departure from Earth would be enough to successfully navigate a 6,300-year voyage. At least theoretically, Marin reasoned, this proved that it was not impossible for humans to sustain a healthy gene pool on the trip to Proxima b. “And after that,” he explains, “you ask, how can we do it?”
He estimated next how much space would be required to produce food. The trick, he surmised in a paper from this year, would be to farm vegetables through aeroponics — a highly efficient growing system where nutrient mists are sprayed onto the roots of hanging plants — and derive some additional protein from animals, which have greater space requirements. Using these techniques, the total space needed to feed a crew of 500 would be 0.45 km2, or 111 acres: the same area as Vatican City, or roughly an eighth the size of Central Park. This area would be distributed around a slowly rotating cylinder in order to produce artificial gravity, crucial for humans to retain muscle mass and normal bodily functions over a prolonged period in space, and span multiple floors too. One architecture plan Marin suggests is a cylinder just 25 metres tall but with a radius of 224 metres, not dissimilar to NASA’s iconic Stanford Torus concept.
What Frédéric Marin takes to be an indication of the viability of interstellar travel would seem to prove the exact opposite to others. While the Breakthrough Starshot project lists significant challenges to be overcome in order to reach Alpha Centauri with a probe weighing less than a nickel, Marin’s calculations describe a ship bigger than the U.S. Navy’s largest aircraft carrier. Surely this giant vessel would be too massive to move across the sky?
When I spoke with Avi Loeb, Frank B. Baird Jr. professor of science at Harvard University and chair of the advisory committee to the Breakthrough Starshot project, I’d expected that he would scoff at the idea of a 500-person vessel, given the difficulty of interstellar travel even for ultra-small ships. But he didn’t. Theoretically, he explains, there’s no problem moving a far bigger load with the same laser propulsion system that Starshot will use. But there’s another obstacle. “Once you go out of the protective womb of the magnetic field of Earth,” Loeb says, “you’re exposed to very energetic particles that, within a year, will damage a significant fraction of the cells in your brain... This is a risk for people who go to Mars, without even thinking about a journey that lasts hundreds of years.”
Even so, he agrees with Marin that we may need to figure out how to pull off a multi-generation space mission. “There is no doubt that our future is in space,” he told me. “One way or another we’ll have to leave the Earth... At some point there will be a risk from an asteroid that will hit us, or eventually the Sun will heat up to the point that it will boil off all the oceans on Earth. Ultimately, to survive we will need to relocate.”
This June, a group of researchers from around the world converged on the Erasmus Space Exhibition Centre in Noordwijk, the Netherlands, for the European Space Agency (ESA)’s first ever Interstellar Workshop. Under the high roof of the auditorium with spotlights facing the stage, an audience of more than a hundred sat in orderly rows to watch presentations on multi-generation space travel.
Scientists had shown up from numerous fields of research: architecture, astrophysics, linguistics, sociology, engineering, materials science, human and plant biology, and more. Many of them aimed to answer questions that come up only after you assume that — like Marin’s simulations suggest — we can actually build the ship, and keep humans healthy inside it for a millennium or more.
This was the theory advanced in “World Ships: Feasibility and Rationale,” a presentation given by aerospace engineer Andreas Hein that expounded on the trade-offs of different ship designs, as well as the assumption behind “Sociology of Interstellar Exploration: Annotations on Social Order, Authority, and Power Structures,” in which sociology professor Elke Hemminger theorized about the kind of social structure a world ship mission would require. It was in artist/biologist Angelo Vermeulen’s “Evolving Asteroid Starships: A Bio-Inspired Approach for Interstellar Space Systems,” and in theology lecturer Michael Waltemathe’s “Philosophical Aspects of Interstellar Exploration,” a presentation spanning mission ethics, anti-contamination principles in space, and Christianity’s response to aliens. (For the latter he cites the Vatican’s former chief astronomer José Gabriel Funes, who has argued that it must logically be possible for an all powerful God to have made extraterrestrial species — and that without original sin, they might even enjoy a closer relationship to their creator than humans.)
Others looked at what it means for the crew of the ship — not the first generation, who choose to leave Earth behind, but for the second, tenth, fiftieth, one hundredth, the people for whom our planet is just a myth; for whom there will be no other life but the journey.
Andrew McKenzie and Jeffrey Punske, linguists from the University of Kansas and the University of Southern Illinois, write that “[i]f a trip takes several generations to complete, the language may differ significantly at arrival from that of the passengers at departure.” More evocatively they suggest: “Even if the onboard schools rigorously maintained the teaching of ‘Earth English’ the children would develop their own Vessel English dialect, which would diverge from Earth English over time.” The problem would be compounded by the fact that this “Vessel English” — using English as just one example — would be unique to each ship, so that the crew of two ships arriving at the same planet would speak a different dialect, or even a different language altogether.
Ultimately, to survive we will need to relocate.
Separately, Neil Levy, a professor of philosophy at Macquarie University in Sydney and senior research fellow in ethics at Oxford University, considered the moral implications in an article for Aeon:
“A generation ship can work only if most of the children born aboard can be trained to become the next generation of crew,” he writes. “They will have little or no choice over what kind of project they pursue. At best, they will have a range of shipboard careers to choose between: chef, gardener, engineer, pilot, and so on.”
In other words, their life options will be extremely limited, as would be the range of experiences they can enjoy. Would it even be ethical to put them in this situation?
The conclusion depends on what we believe is justified to preserve our species, a reckoning Levy declines to make. Instead, he points to the subtext of the question: Life outcomes are already defined by accident of birth in the world as it is; the range of any child’s possible futures is constrained by poverty, nationality, religion, culture. This may be unjust, but we accept this as part of the human condition. “Asking about the permissibility of generation ships,” he writes, “might give us a fresh perspective on the permissibility of the constraints we impose now on human lives, here on the biggest generation ship of them all — our planet.”
There are more than just technological obstacles to colonizing our nearest star. For one, we can’t afford it.
In his research, Andreas Hein of the Initiative for Interstellar Studies estimates that the world economy, if it continues to grow at current rates, would be able to cover the cost of building a generation ship sometime between the year 2500 and 3000. And it’s not only a matter of time: We most likely couldn’t develop a big enough economy with the resources of Earth alone, so would need to expand in some way beyond our home planet. Colonizing space would be necessary for both the funds — say from mining asteroids — and to test the idea that it’s possible to live in a spaceship for hundreds of years.
For his part, Professor Avi Loeb, the chair of the Breakthrough Starshot project advisory board, considers space travel so dangerous that it’s not worth making such a trip, though he hasn’t given up on the idea of human life arriving in far off star systems. Instead, he sees other paths to establishing life elsewhere as more likely, like sending out an artificial intelligence system that could build biological cells from the raw materials it encountered, assembling life again from scratch that may or may not resemble our current human race.
Given that it could take a millennium for such a trip to actually materialize and that a colonized planet might not even resemble our current culture, it’s easy to see the efforts around multi-generational space travel, even those by serious scientists, as nothing more than a pipe dream.
Paul M. Sutter, an astrophysicist at Ohio State University and the Flatiron Institute in New York, has published op-eds on the difficulty of interstellar travel, particularly the Breakthrough Starshot program. Starshot is not a bad idea, he argues, “it’s just that interstellar travel is beyond ridiculously hard.” In a YouTube video, Sutter explains that the Starshot laser propulsion method — which would require as much power as the output of all the nuclear power stations in the United States combined — will transfer only a few pounds of thrust to the space probe. Asked about using the same method to drive a ship that can carry even a single human, Sutter is skeptical. “You’ll need either a million times more energy, or it takes a million times longer,” he says — and neither sounds like a viable option.
The prohibitive cost and difficulty of space exploration also means that progress is slow. “It’s been 50 years [since the moon landing] and we can’t do much more than we did in the ’60s,” says Sutter. “So follow that line of thinking to work out what we could do 50 years from now.”
But we may find value long before the trip itself, from ancillary benefits of the research.
Angelo Vermeulen, an artist and biologist by training who now works as a space systems researcher at Delft University of Technology in the Netherlands, specializes in applying principles from the natural world to artificial systems. He describes his work as “theoretical research into morphogenetic engineering,” an approach where complex design emerges from a small set of initial rules and properties — like the way termites build large, naturally cooled mounds to live in without any central control.
Some of his work integrates research from the MELiSSA program, a project led by ESA to develop a closed, circular life-support system that will recycle carbon dioxide and organic waste into food, oxygen, and water. While MELiSSA’s ultimate goal is to make long-duration space missions possible, it has also spun off a sister company charged with developing commercial, terrestrial applications of the technology — like a modular sanitation hubthat can provide wastewater treatment in off-grid environments, or a nutrient rich bacterium that also reduces cholesterol.
In some form or another, the majority of researchers I spoke to about multi-generation space travel pointed out that it’s not possible to map out all of the applications of a technological or scientific breakthrough until it has been released to the public. We can’t start connecting the dots, and finding new routes and patterns, until those dots exist somewhere on the page; but with hindsight, patterns over the short- and long-term become more obvious, sometimes in unexpected ways.
At the end of our call, Vermeulen tells me a story: In 1901, at the Pan American Exposition in Buffalo, the star attraction was a ride that simulated a trip to the moon. For 50 cents passengers could board the “spaceship” Luna, a winged wooden craft that through an artful combination of pulleys, theater props, optical illusions, and even dwarf actors, gave the impression of leaving Earth behind and climbing into space for an alien encounter.
The ride was wildly successful, attracting 400,000 paying customers, including then-President William McKinley, Thomas Edison, and various Supreme Court justices. It was reported in news bulletins around the world.
It was also pure turn-of-the-century showmanship, a triumph of creativity that, like the pulp sci-fi movies of the 1960s or ’70s, showed a vision of the future still hopelessly bound to the ideas of the time. But its exact impact — its impact on the collective consciousness — is hard to quantify. Perhaps without the Luna there would be no NASA, no Apollo mission, no Mars rover today. Without these leaps of imagination, without speculating about what the future could be before we get there, we never arrive at anywhere different to the present. And maybe, just maybe, one day a man or woman on a distant planet will look back at this research, antiquated as it will seem, and say the same.
Quelle:M One Zero | 0.837272 | 3.050865 |
The JEM-EUSO (Joint Experiment Missions for the Extreme Universe Space Observatory) program aims at developing Ultra-Violet (UV) fluorescence telescopes for efficient detections of Extensive Air Showers (EASs) induced by Ultra-High Energy Cosmic Rays (UHECRs) from satellite orbit. In order to demonstrate key technologies for JEM-EUSO, we constructed the EUSO-Balloon instrument that consists of a ∼1 m 2 refractive telescope with two Fresnel lenses and an array of multi-anode photo-multiplier tubes at the focus. Distinguishing it from the former balloon-borne experiments, EUSO-Balloon has the capabilities of single photon counting with a gate time of 2.3 µs and of imaging with a total of 2304 pixels. As a pathfinder mission, the instrument was launched for an 8 h stratospheric flight on a moonless night in August 2014 over Timmins, Canada. In this work, we analyze the count rates over ∼2.5 h intervals. The measurements are of diffuse light, e.g. of airglow emission, back-scattered from the Earth's atmosphere as well as artificial light sources. Count rates from such diffuse light are a background for EAS detections in future missions and relevant factor for the analysis of EAS events. We also obtain the geographical distribution of the count rates over a ∼780 km 2 area along the balloon trajectory. In developed areas, light sources such as the airport, mines, and factories are clearly identified. This demonstrates the correct location of signals that will be required for the EAS analysis in future missions. Although a precise determination of count rates is relevant for the existing instruments, the absolute intensity of diffuse light is deduced for the limited conditions by assuming spectra models and considering simulations of the instrument response. Based on the study of diffuse light by EUSO-Balloon, we also discuss the implications for coming pathfinders and future space-based UHECR observation missions.
|Titolo:||Ultra-violet imaging of the night-time earth by EUSO-Balloon towards space-based ultra-high energy cosmic ray observations|
|Data di pubblicazione:||2019|
|Appare nelle tipologie:||1.1 Articolo in rivista| | 0.893227 | 3.651466 |
Causes of extreme sea levels
Extreme sea levels occur on a range of time and space scales in any given coastal location, and so the contribution of each phenomenon to extreme sea levels varies.
Here we describe
For longer time scales, see the Sea Level area
Tides occur as a result of gravitational forces from the Moon and the Sun that produce changes in sea level, mostly on daily or half-daily time scales known as diurnal and semi-diurnal respectively. In the deep ocean the tidal range is typically a few tens of centimetres, but in coastal regions it can be up to several metres.
Highest astronomical tide (HAT) relative to mean sea level around Australia (shown on a logarithmic scale). Note that daily mean tidal range patterns are similar to that of HAT. Circles indicate values derived from hourly tide gauge data; gridded data values (contours) were calculated from satellite altimetry (TPX07-Atlas). Source: McInnes et al. 2016
Astronomical tides can vary on other timescales too, including the fortnightly spring and neap tides, seasonal and interannual changes, and modulation of the tidal amplitude over the 18.6 year lunar cycle.
Storm surges are the major cause of extreme sea levels and devastating coastal impacts along many coastlines around the world, which can result in significant human tolls and economic losses. For example, the storm surge from Typhoon Nargis in Myanmar in 2008 killed 138,000 people (IPCC, 2012), and following Hurricane Katrina in 2005 the US Federal government flood damage payouts totalled around $16.1 billion.
Storm surges are gravity waves arising from the inverse barometer effect and wind stress. The inverse barometer effect elevates sea levels approximately 1 cm for every 1 hPa fall in atmospheric pressure relative to surrounding conditions. Wind stress induces currents over shallow water. Wind stress directed onshore leads to an increase in sea levels (i.e. “wind setup”), particularly within semi-enclosed embayments or under severe wind forcing such as produced by tropical cyclones. In mid-latitudes, wind-induced coast-parallel currents which persist for a day or more, undergo Coriolis deflection. In the northern hemisphere coastal currents flowing with the coast to the right (left) will become elevated (depressed) at the coast and this is referred to as “current setup” (“setdown”). In the southern hemisphere, coastal currents flowing with the coast to the left (right) will result in elevated (depressed) coastal sea levels.
The storm conditions that create storm surges will also create large wind-generated waves. In some situations and locations, such as coastlines and islands with little or no continental shelf, waves may produce a greater impact than the storm surge in a severe storm. Unlike storm surges which are generated by storm systems in the immediate vicinity, the sources of waves include not only local weather conditions but also distant storms. This is because waves can travel long distances in deep water from their point of origin with little loss of energy. Such waves are called swell.
Waves steepen and break as they encounter shallow coastal waters. The wave breaking leads to loss of energy and loss of wave height. Therefore, the further offshore these conditions are encountered the smaller the waves will be that finally reach the shore. Conversely, deeper waters lying adjacent to coastlines enable waves to travel closer in to shore before finally breaking. These two situations are illustrated below. Paradoxically, the conditions that ensure that waves lose energy before reaching the shore are the same conditions that favour larger storm surges. As the waves move progressively into shallower water, they break and lose energy. Some of this energy is transferred into a shoreward momentum flux which acts to raise the mean sea level slightly close into shore. This sea level increase is called wave setup.
Coastal geometry influences the severity of storm surges experienced at the coast. Storm surges are amplified by wide continental shelves. This is because the currents caused by the wind are slowed down by the friction created by the ocean floor over the shallower shelf region and this in turn causes the water depth to increase. Thus on shelf coastlines, storm surges dominate extreme sea level events. However around reefs where there is no coastal shelf, there is little change in sea level due to storm surges, but waves play a dominant role in extreme sea level events, as the fringing reef causes wave amplitude to suddenly increase as described above.
Contributions to extreme sea levels from tides, El Niño Southern Oscillation, storm surges and wind waves on reef atolls (top) and continental shelf areas (bottom).
Other topographic features such as headlands can also either amplify or protect a coastal region from storm surge depending on the prevailing wind direction in relation to the headland.
Some earthquakes cause a very rapid vertical movement of the ocean floor and in these cases generate tsunamis (tidal waves), such as the 2004 Boxing Day Tsunami in the Indian Ocean. Tsunamis travel at speeds of about 200 metres per second in the deep ocean (about 700 kilometres per hour), taking several hours to cross an ocean basin allowing time for tsunamis warnings to be issued. Tsunami warning systems are being strengthened since the 2004 Boxing Day Tsunami.
For more information on sea level extremes in Australia, see McInnes et al, 2016, doi:10.1007/s10584-016-1647-8. | 0.843054 | 3.081357 |
West Virginia University researchers have helped discover the most massive neutron star to date, a breakthrough uncovered through the Green Bank Telescope in Pocahontas County.
The neutron star, called J0740+6620, is a rapidly spinning pulsar that packs 2.17 times the mass of the sun (which is 333,000 times the mass of the Earth) into a sphere only 20-30 kilometers, or about 15 miles, across. This measurement approaches the limits of how massive and compact a single object can become without crushing itself down into a black hole.
The star was detected approximately 4,600 light-years from Earth. One light-year is about six trillion miles.
These findings, from the National Science Foundation-funded NANOGrav Physics Frontiers Center, were published today (Sept. 16) in Nature Astronomy.
Authors on the paper include Duncan Lorimer, astronomy professor and Eberly College of Arts and Sciences associate dean for research; Eberly Distinguished Professor of Physics and Astronomy Maura McLaughlin; Nate Garver-Daniels, system administrator in the Department of Physics and Astronomy; and postdocs and former students Harsha Blumer, Paul Brook, Pete Gentile, Megan Jones and Michael Lam.
The discovery is one of many serendipitous results, McLaughlin said, that have emerged during routine observations taken as part of a search for gravitational waves.
“At Green Bank, we’re trying to detect gravitational waves from pulsars,” she said. “In order to do that, we need to observe lots of millisecond pulsars, which are rapidly rotating neutron stars. This (the discovery) is not a gravitational wave detection paper but one of many important results which have arisen from our observations.”
The mass of the pulsar was measured through a phenomenon known as “Shapiro Delay.” In essence, gravity from a white dwarf companion star warps the space surrounding it, in accordance with Einstein’s general theory of relativity. This makes the pulses from the pulsar travel just a little bit farther as they travel through the distorted spacetime around white dwarf. This delay tells them the mass of the white dwarf, which in turn provides a mass measurement of the neutron star.
Neutron stars are the compressed remains of massive stars gone supernova. They’re created when giant stars die in supernovas and their cores collapse, with the protons and electrons melting into each other to form neutrons.
To visualize the mass of the neutron star discovered, a single sugar-cube worth of neutron-star material would weigh 100 million tons here on Earth, or about the same as the entire human population.
While astronomers and physicists have studied these objects for decades, many mysteries remain about the nature of their interiors: Do crushed neutrons become “superfluid” and flow freely? Do they breakdown into a soup of subatomic quarks or other exotic particles? What is the tipping point when gravity wins out over matter and forms a black hole?
“These stars are very exotic,” McLaughlin said. “We don’t know what they’re made of and one really important question is, ‘How massive can you make one of these stars?’ It has implications for very exotic material that we simply can’t create in a laboratory on Earth.”
Pulsars get their name because of the twin beams of radio waves they emit from their magnetic poles. These beams sweep across space in a lighthouse-like fashion. Some rotate hundreds of times each second.
Since pulsars spin with such phenomenal speed and regularity, astronomers can use them as the cosmic equivalent of atomic clocks. Such precise timekeeping helps astronomers study the nature of spacetime, measure the masses of stellar objects and improve their understanding of general relativity.
More information: H. T. Cromartie et al. Relativistic Shapiro delay measurements of an extremely massive millisecond pulsar. Nature Astronomy (2019). DOI: 10.1038/s41550-019-0880-2
Image: Neutron stars are the compressed remains of massive stars gone supernova. WVU astronomers were part of a research team that detected the most massive neutron star to date.
Credit: B. Saxton (NRAO/AUI/NSF) | 0.890823 | 3.840148 |
Lynx constellation is located in the northern hemisphere. It represents the lynx, and it is not usually associated with any myths.
Lynx is one of the several constellations that were introduced by the Polish astronomer Johannes Hevelius in the 17th century.
Hevelius created the constellation to fill a relatively large gap between the two neighboring constellations, Auriga and Ursa Major. He named it Lynx because it was pretty faint and it took the eyesight of a lynx to see it. Other than Alpha Lyncis, the constellation does not contain any stars brighter than fourth magnitude.
FACTS, LOCATION & MAP
Lynx is the 28th constellation in size, occupying an area of 545 square degrees. It lies in the second quadrant of the northern hemisphere (NQ2) and can be seen at latitudes between +90° and -55°. The neighboring constellations are Auriga, Camelopardalis, Cancer, Gemini, Leo, Leo Minor and Ursa Major.
Lynx contains five stars with known planets and has no Messier objects. The brightest star in the constellation is Alpha Lyncis, with an apparent magnitude of 3.13. There are no meteor showers associated with the constellation.
Hevelius named the constellation after the lynx because it is a relatively faint one. He wrote in his Prodromus astronomiae that only those who have the sight of a lynx can see it. The book is an unfinished work published by Hevelius’ wife around 1690, a few years after his death. In the accompanying star catalogue, Hevelius called the constellation “Lynx, sive Tigris” – Lynx or Tiger.
While it is not known if Hevelius had any myths in mind when he named the constellation, there is a figure in mythology that might be linked to the constellation’s name. Lynceus, who sailed with Jason and the Argonauts, was said to have the keenest eyesight of all men and could even see things underground. He and his twin brother Idas were part of the expedition for the Golden Fleece.
Some of the stars in Lynx were documented by the Greek astronomer Ptolemy in the 2nd century, but only as “unformed” stars near Ursa Major, and not as part of any constellation.
MAJOR STARS IN LYNX
α Lyncis (Alpha Lyncis)
Alpha Lyncis has an apparent magnitude of 3.13 and is about 203 light years distant from the solar system. It belongs to the spectral class K7 III, which means that it is an orange giant that has moved past the main sequence stage and exhausted the hydrogen at its core.
Alpha Lyncis is the brightest star in Lynx and the only star in the constellation that has a Bayer designation (a Greek letter and the name of the constellation in genitive form). Other stars in Lynx use Flamsteed numbers. Alpha Lyncis is sometimes also known as Elvashak.
The star has a radius 55 times solar and is about 673 times more luminous than the Sun.
Alsciaukat – 31 Lyncis
Alsciaukat is the only star in Lynx that has a proper name. It is derived from the Arabic word aš-šawkat which means “thorn.” The star is also sometimes also called Mabsuthat, from the Arabic al-mabsūtah for “the outstretched (paw).”
The star is very similar to Alpha Lyncis in radius and mass. Both stars have roughly two solar masses and are about 1.4 billion years old. Like Alpha Lyncis, Alsciaukat is an orange giant, one belonging to the spectral class K4.5 III.
31 Lyncis is also variable star and is sometimes known as BN Lyncis. Its brightness only varies slightly, by 0.05 magnitudes, but this indicates that the star will eventually turn into a long-period variable similar to Mira (Omicron Ceti) in the Cetus constellation.
Alsciaukat is the fourth brightest star in Lynx. It has a visual magnitude of 4.25 and is approximately 389 light years distant.
38 Lyncis is the second brightest star in the constellation. It has a visual magnitude of 3.82 and is approximately 122 light years distant. It belongs to the spectral class A1V.
38 Lyncis is in fact a binary star composed of a close pair separated by only 2.6 arc seconds. The brighter component is a class A3 hydrogen fusing dwarf that has a sixth magnitude star, either a class A4 or A6 dwarf, for a companion. The primary component in the system is 31 times more luminous than the Sun. It is a rapid rotator, with a speed of over 190 km/s at the equator, and it completes a rotation in less than 15 hours.
12 Lyncis is a star of the spectral type A3V. It has an apparent magnitude of 4.86 and is approximately 229 light years distant. It is really a triple star system, with the second component 1.7” away from the primary and orbiting it with a period of 699 years, and the third component separated by 8.7” from the primary.
19 Lyncis is a binary star with a visual magnitude of 5.80. The primary component in the system is a B8V class star 468 light years distant, and the companion belongs to the spectral class K5III and is approximately 1148 light years distant from the Sun.
6 Lyncis is a subgiant of the spectral type K0IV 15 times brighter than the Sun. It has an apparent magnitude of 5.88 and is about 182 light years distant. A planet with at least 2.4 Jupiter masses was discovered in the star’s orbit in July 2008. It orbits the star with a period of 899 days.
HD 75898 is a yellow subgiant star belonging to the spectral type G0IV. It has a visual magnitude of 8.04 and is 262.82 light years distant from the Sun. The star’s estimated age is only 3.8 billion years. HD 75898 is 28% more massive and 60% larger than the Sun, and has three times the solar luminosity. A planet was discovered orbiting the star in January 2007. It has an orbital period of about 418.2 days.
DEEP SKY OBJECTS IN LYNX
NGC 2419 (Caldwell 25) – Intergalactic Wanderer
NGC 2419, also known as the Intergalactic Tramp or Intergalactic Wanderer, is a globular star cluster with a visual magnitude of 9.06. It is a Shapley class II cluster, which means that it is highly concentrated at the centre.
The cluster got its nickname because it was originally believed not to be in orbit around the Milky Way. This has been proven false since: NGC 2419 takes about three billion years to complete an orbit around our galaxy. It is 300,000 light years distant from the galactic centre and about 275,000 light years from the solar system. It is one of the most remote globular clusters, both from the galactic centre and from the Sun, almost twice as distant as the Large Magellanic Cloud in the constellation Dorado.
The cluster was discovered by the German-born British astronomer William Herschel on December 31, 1788.
NGC 2419 was originally believed to be a star. It was the American astronomer Carl Lampland who discovered that it was really a globular cluster of stars.
UFO Galaxy – NGC 2683
NGC 2683 is an unbarred spiral galaxy in Lynx. It appears nearly edge-on when observed from Earth. The galaxy has a visual magnitude of 10.6 and is about 25 million light years distant.
The Astronaut Memorial Planetarium and Observatory site gave it the nickname the ‘UFO galaxy.’
The galaxy was discovered by William Herschel in February 1788. It is moving away from Earth at the speed of 410 km/s and from the galactic centre at 375 km/s.
Bear’s Paw Galaxy – NGC 2537 (Arp 6)
NGC 2537 is classified as a blue compact dwarf galaxy (BCD galaxy), which means that it is a small galaxy that contains large clusters of hot young stars which make the galaxy appear blue in colour.
The galaxy has a visual magnitude of 12.3.
NGC 2770 is a spiral galaxy in Lynx. It has an apparent magnitude of 12.0 and is 88 million light years distant.
The galaxy has been nicknamed the ‘Supernova Factory’ because three supernova events have been observed in it in recent years: SN 1999eh, SN 2007uy and SN 2008D. SN 2008D is notable for being the first supernova to first be detected by the x-rays emitted early in its formation and not by the light emitted later in the process.
NGC 2541 is an unbarred spiral galaxy with a visual magnitude of 12.3, approximately 41 million light years from the Sun.
It belongs to the NGC 2841 group, a group of galaxies located in the constellations Lynx and Ursa Major.
NGC 2537 (Bear’s Paw) also belongs to this group. | 0.821471 | 3.691195 |
NASA’s New Horizons spacecraft is on the doorstep of the solar system’s largest planet. The spacecraft will study and swing past Jupiter, increasing speed on its voyage toward Pluto, the Kuiper Belt and beyond.
The fastest spacecraft ever launched, New Horizons will make its closest pass to Jupiter on Feb. 28, 2007. Jupiter’s gravity will accelerate New Horizons away from the sun by an additional 9,000 miles per hour, pushing it past 52,000 mph and hurling it toward a pass through the Pluto system in July 2015.
“Our highest priority is to get the spacecraft safely through the gravity assist and on its way to Pluto,” says New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute, Boulder, Colo. “We also have an incredible opportunity to conduct a real-world encounter stress test to wring out our procedures and techniques, and to collect some valuable science data.”
The New Horizons mission team will use the flyby to put the probe’s systems and seven science instruments through the paces of more than 700 observations of Jupiter and its four largest moons. The planned observations from January through June include scans of Jupiter’s turbulent, stormy atmosphere; a detailed survey of its ring system; and a detailed study of Jupiter’s moons.
The spacecraft also will take the first-ever trip down the long “tail” of Jupiter’s magnetosphere, a wide stream of charged particles that extends tens of millions of miles beyond the planet, and the first close-up look at the “Little Red Spot,” a nascent storm south of Jupiter’s famous Great Red Spot.
Much of the data from the Jupiter flyby will not be sent back to Earth until after the spacecraft’s closest approach to the planet. New Horizons’ main priority during the Jupiter close approach phase is to observe the planet and store data on its recorders before orienting its main antenna to transmit information home beginning in early March.
“Since launch, New Horizons will reach Jupiter faster than any of NASA’s previous spacecraft and begin a year of extraordinary planetary science to complement future exploration activities,” says Jim Green acting director, Planetary Science Division, NASA headquarters, Washington.
New Horizons has undergone a full range of system and instrument checkouts, instrument calibrations, flight software enhancements, and three propulsive maneuvers to adjust its trajectory.
After an eight-year cruise from Jupiter across the expanse of the outer solar system, New Horizons will conduct a five-month-long study of Pluto and its three moons in 2015. Scientific research will include studying the global geology, mapping surface compositions and temperatures, and examining Pluto’s atmospheric composition and structure. A potential extended mission would conduct similar studies of one or more smaller worlds in the Kuiper Belt, the region of ancient, rocky, icy planetary building blocks far beyond Neptune’s orbit.
New Horizons is the first mission in NASA’s New Frontiers Program of medium-class spacecraft exploration projects. The Applied Physics Laboratory, Laurel, Md., manages the mission for NASA’s Science Mission Directorate, Washington. The mission team also includes NASA’s Goddard Space Flight Center, Greenbelt, Md.; NASA’s Jet Propulsion Laboratory, Pasadena, Calif.; the U.S. Department of Energy, Washington; Southwest Research Institute, Boulder, Colo.; and several corporations and university partners. | 0.850193 | 3.516868 |
Earth may once have had two moons, which collided to form one. A new theory has been formulated to explain our moon’s asymmetry—the dark side of our moon is mountainous and rugged, whereas the side visible from Earth has relatively flat, dark lava fields. The cause of this mysterious irregularity was mathematically modelled by planetary scientists at the University of California, Santa Cruz, and the University of Bern in Switzerland, and the results were published in Nature in August 2011.
The theory states that two moons were formed approximately 4.4 billion years ago, when a Mars-sized planet collided with our newly formed planet. The collision ejected pieces of crust and mantle into Earth’s orbit. The debris coalesced to form two moons—one three times the size of the other.
Eighty million years later, the smaller of the two moons had cooled and hardened, but the larger was still molten. The two eventually collided at 7000 km/h, a speed insufficient to create a crater. Instead, the small moon crumbled upon impact and its shattered remains were deposited over one hemisphere of the resulting body, forming the rugged mountains. The impact also displaced the larger moon’s fluid magma to the side nearest to us, explaining the high concentration there of potassium, phosphorus and rare earth elements, which form once magma has solidified.
NASA plans a moon mission for September this year, when it will search for physical proof of this surprising double-moon theory. | 0.853859 | 3.522146 |
The possible existence of extraterrestrial life and, even more, the eventual contact with it, has been the subject of speculation, anger and anxiety for humanity in modern times.
Meanwhile, from outer space, science has registered multiple signals, hitherto inexplicable for experts. These signals have led to numerous theories and speculations.
4. The Signals from the Perseus Cluster
In June 2014, the Chandra X-ray observatory from NASA, and the XMM-Newton observatory of the European Space Agency, recorded a clearly intelligent signal originating from the Perseus cluster, a group of galaxies located about 240 million light years away from Earth.
As a result from the data obtained from the study of a black hole which is located in the Star system referred to as GRS 1915 +105, a researcher from the MIT, Edward Morgan was able to recreate one of the most mysterious sounds ever registered by humans.
The replicated model is the biggest black hole in the Milky Way, exceeding the mass of the Sun by approximately 18 times. This mysterious black hole emits a B flat sound at a frequency 1 million times deeper than anything perceived by the human ear.
2. Space Explosion
Between 2011 and 1012, the Parkes radio telescope located in New South Wales, Australia performed routine space sweeps and ran into FOUR mysterious bursts of radio signals. Each of those bursts lasted only a couple of milliseconds but their energy was extremely powerful.
While researchers speculate that these radio bursts might come from the depths of the Milky Way, there are other scientists who believe that they originated from elsewhere, in a galaxy further away from us. Scientists have no idea what caused these bursts and why they are so powerful.
1. The Wow! Signal
On August the 15th 1977, exactly at 10:16 p.m. EST, the Big Ear radio telescope in Ohio, USA detected a signal of unknown origin. This mysterious signal lasted for 72 seconds with an intensity 30 times higher than that of the “white noise” or background noise of the Universe.
Astronomers decided to call it the Wow! signal because it was the only thing that Professor Jerry Ehman, who was then monitoring the computers, managed to write down on paper at the time the signal was recorded.
The circled alphanumeric code “6EQUJ5″ describes the intensity variation of the signal. The signal bore the expected hallmarks of non-terrestrial and non-Solar System origin.
Up until today, this signal remains one of the most mysterious ever received. many believe that the Wow! signal originated from an extraterrestrial civilization in our galactic neighborhood, in the constellation Sagittarius, near the Chi Sagittarii star group.
Several attempts were made by Ehman as well as by other astronomers to detect and identify the signal again. The signal was expected to appear three minutes apart in each of the horns, but that did not happen.
By Ancient Code | 0.877137 | 3.242915 |
Are we alone? For centuries upon centuries, most of us who have looked at the clear night sky have pondered about this simple, yet universal question. It doesn’t matter if we’re scientists or craftsmen, scholars or artists, kids or adults. It’s one of those questions that never seems to fade in the excitement it can elicit. One of the reasons surely is: We haven’t found an answer yet.
Kevin Peter Hand has been seeking precisely that for over two decades. The astrobiologist and planetary scientist works at the Jet Propulsion Laboratory (JPL) in Pasadena, California. The JPL is closely connected to NASA and develops as well as builds space missions for the US agency.
As with most people who dedicate vast stretches of their career to a few key endeavors only, Hand fell for this passion when he was still a boy: “I grew up in a small town in the green mountains of Vermont. I was captivated by a clear night sky. When one is exposed to the stars, especially at a young age, your imagination can’t help but get captured by the questions whether or not we’re alone and whether or not life exists beyond Earth,” he told Observer. That led him to studies in physics, astronomy and psychology.
Today, he’s one of the lead scientists at NASA. In his new book Alien Oceans: The Search for Life in the Depths of Space (Princeton University Press) he tells us about the origins of life on Earth and in outer space, explains, how Goldilocks fits into the equation and indicates what searching for “life as we know it from Earth” might look like outside our own galaxy—up to 1.4 billion kilometers away.
Finding signs of life—or biosignatures, as the science community puts it—is most likely going to be successful where you find liquid water. Space missions, which Hands also covers in great detail, have found that there are a number of so-called ocean worlds out there—terrestrial-like bodies with large amounts of liquid water. “The three most compelling ocean worlds when it comes to the prospect of finding life beyond Earth,” Hand writes, “are the Jovian ice moon Europa as well as the Saturnian moons Titan and Enceladus.”
What about Mars, though? Isn’t the Curiosity Rover roaming over the surface of the red planet as we speak? Yes, but “when it comes to the search for extraterrestrial life within these alien oceans, we are talking about the search for life that is alive today. On Mars, in contrast, we’re largely searching for remnants of life. If we found fossilized evidence of life on Mars with the Curiosity Rover tomorrow, that’d be revolutionary. But with those fossils, we would not be able to understand its genetic make-up, its biochemistry,” Hand said.
Even though Hand is a master of putting things simply while remaining scientifically accurate, Alien Oceans is not your typical nightstand read. You wouldn’t open his 304 pages to wind down after an exhausting day of work. You certainly need to have the inclination to pick it up. But Hand makes it easy for you to develop just that.
Every now and again, he sprinkles anecdotes from his experiences as a researcher into the narrative, for example what it was like when he dove down 10,000 feet in a tiny submersible, to the bottom of the Atlantic Ocean, because renowned director James Cameron asked to join him on an expedition. At first Hand was hesitant to join Cameron. After all, the young researcher was in the middle of his PhD. But, he recalls now, “if you ever get the chance to go to the bottom of the ocean, take it. Don’t think twice; just say yes. Your brain will be changed forever.”
So will your perception of life after you’ve read Hand’s book, which is a historical account of groundbreaking missions in the past here on Earth and far beyond as well a glimpse into the future. He explains how spacecrafts Galileo and Cassini were able to discover liquid oceans. Oceans that are not only located outside our own solar system but also hidden under icy crusts several miles in thickness.
Over the course of his book, he gets into the nitty-gritty details of science, genetics, astrobiology, chemistry, history and, yes, even philosophy at times. But he does it in a way that you as a reader don’t have to take classes at Oxford, Cambridge or Princeton before being able to make sense of what he talks about.
Speaking of making sense… you might want to ask the question (which of course we did): Why spend hundreds of millions of dollars to look for life beyond Earth in the first place? Isn’t there more pressing things to deal with? “I always get confounded when people ask ‘Why bother looking for life?’ We don’t seem to have an issue when it comes to the importance of physics, chemistry or geology beyond Earth,” Hand said. “Yet, when it comes to biology, we get this weird preciousness. But we’re talking about understanding the fourth fundamental science. When it comes to biology, we’ve yet to make that leap to see that it works beyond earth.” That’s what he’s after.
And he’s right. Not only from a philosophical perspective. Finding life beyond Earth—and by that most likely discovering a second independent origin of life (because these icy moons are too far away to have accidentally been seeded by life on Earth)—is closely connected to understanding life right here on our planet. Right now, Hand argues, we don’t really know how and where life on Earth came to be.
There is, to be fair, quite a stretch in the book where a beginner’s knowledge of chemistry and physics will help, but if you work your way through it, you’ll be rewarded with the experience of putting this newfound knowledge to use in the concrete scenarios he outlines towards the end. There, Hand talks about what landing and exploratory missions might look like (something that he himself has been working on since 2006) and how autonomous vehicles can melt their way through an icy shell, launch a mini submersible and dive into unchartered waters. It feels like reading the script of a sci-fi-movie, only that it’s real. Or at least, has the potential to become reality one day in the more or less distant future—sometime within the next 20 to 40 years. The first vehicles are being built and tested right now.
Well, let’s assume those rovers find something; then what? “The discovery of life beyond Earth isn’t going to change the way you make your coffee in the morning or shorten your daily commute. It won’t provide a cure for cancer or stop climate change. But it will most likely spark a revolution in biology.”
And that, I guess we all agree, can only be a good thing. | 0.909223 | 3.462285 |
By Simon Tegel
LIMA, Peru — On a remote hilltop 8,000 feet above sea level in Chile’s Atacama Desert, scientists hope to answer one of the most fundamental questions facing humankind: Is there life elsewhere in the universe?
That’s one of various goals of the Giant Magellan Telescope, or GMT, now in the early stages of construction and scheduled to start scanning outer space in 2021. Once it does, it’s expected to offer views of the farthest depths of the universe ever achieved.
With seven curved mirrors giving it a record optical surface 80 feet in diameter, the GMT will have the sharpest images of any telescope ever built. Its resolution will be 10 times better than that of the Hubble Space Telescope.
That will allow scientists to peer not just to the edge of the universe billions of light years away, but also effectively back in time.
In particular, they hope to focus on the period between 50 billion and 100 billion years after the Big Bang. That’s the period when most stars, galaxies and black holes began to form — and when the conditions for the start of life on many other planets were most optimal.
But if that sounds challenging, then bear in mind that the telescope will be seeking out planets in the “habitable zone” similar to ours, with water, moderate temperature fluctuations and a stable atmosphere. In most cases, those planets are outshone billions of times by the neighboring stars around which they orbit.
“Are we alone? That is a fundamental question that every human being is interested in answering,” says Patrick McCarthy, GMT president and a Carnegie astronomer. “We are very lucky to be living at a time when we can begin attempting to answer it.”
“Even when I was a graduate student, in the ’80s and ’90s, there was a certain degree of pessimism. It was that we are either on our own in this universe, or else extremely rare. That has changed very quickly, with various breakthroughs in the science,” he adds.
Even if just one star in a billion has a planet in the habitable zone, McCarthy says that still leads to significant odds of life developing elsewhere in the universe. There are 100 billion stars in the Milky Way, one of just 100 billion galaxies. He says there could be as many as “10 to the 15th” habitable planets out there.
If the telescope is successful in picking up the first signs of extraterrestrial life — even if it’s just a few microbes rather than “intelligent” beings — it would be one of the most sensational discoveries in the history of science.
It would also silence the doubters, who still remain a significant minority of experts on the subject.
The consortium behind the GMT is made up of a host of colleges and research centers from Australia, Brazil, Korea and the United States, including Harvard, Texas A&M, the Universities of Arizona, Chicago and Texas at Austin, as well as the Carnegie and Smithsonian Institutions. So far, they have already raised $500 million of the project’s total $1 billion cost, enough for them to decide to move ahead with breaking ground in Chile in November.
The site they have chosen in the Atacama desert is one of the driest areas on Earth. It’s ideal not just because there are roughly 300 days a year without clouds, or because of the altitude. The area also lacks human settlements nearby that give off the kind of ambient light that makes it harder to view the stars, a problem that’s lessened the effectiveness of some other large telescopes around the world. The Chilean site is so remote that the project’s planners believe that even in 50 years, there will still be no people residing or emitting light from their homes and businesses anywhere near the GMT.
That has also allowed them to invest in some truly astonishing technology.
The telescope’s secondary mirrors will be made from honey-combed glass. That makes them unusually light, but also lets them flex and bend, to compensate for atmospheric turbulence distorting light from distant galaxies.
It’s that kind of turbulence that causes stars to twinkle, but which also presents a headache for astronomers. By flexing tiny portions of their reflecting surface up to 500 times a second, the GMT’s mirrors will give scientists a clearer, stable image.
“Glass has this wonderful property that when you bend it — so long as you don’t break it — unlike metal it has no memory of being bent and returns to its original shape,” McCarthy says. “Glass is pretty stiff. You don’t have to bend it very much.”
But now, as the GMT team reaches for the skies, the first step toward putting the telescope in place is building its foundations by digging a huge hole on that Atacama hilltop.
Images courtesy of GMTO Corporation. | 0.819742 | 3.754504 |
In 1705, Edmund Halley predicted the course and eventual return of his eponymous comet, and traced its past appearances (it is depicted in the Bayeux tapestry and was re-observed in 1758). Comets then were also called messengers, a vestige of their mythological role as messengers of the gods; Newton, Halley, and other astronomers of the day considered it possible that they existed to help supply the planets with water and other necessary materials.
In last week’s episode of Cosmos, we saw how Halley’s fascination with comets led to his pressing Newton to finally publish his magnum opus, the three-volume set laying out his version of the calculus, the laws of motion, the law of universal gravitation, and his ability to use those tools to predict the paths of astronomical phenomena including comets (almost: The Principia came out in 1687, and it took another 18 years for Halley to account for the gravitational effects of the planets on comets’ orbits).
The story behind those discoveries is rife with scientific intrigue and rivalries. Alas for Robert Hooke, one of the most brilliant scientists of his day, who advanced biology, physics, chemistry, optics, and a host of other sciences in ways that few others can claim. He was jealous to a fault, and lacked the mathematical skills to bring his intuitions about universal gravitation to fruition. He spent much of his time embroiled in disputes over priority of various discoveries, battling Huygens over clocks, and Isaac Newton over optics and gravity. Hooke may have stolen credit for some experiments that others asked him to conduct on their behalf. Newton outlived and outshone Hooke in the end, and some believe he destroyed the only known portrait of Hooke after his death.
Cosmos overplayed Hooke’s perfidy, turning him into a hunchbacked ogre bent on maliciously and pointlessly tearing down Newton (Newton was no less irascible, and his failure to publish results for decades inevitably led to priority disputes, most famously with Leibniz). The Wire summarizes that section of the Cosmos episode:
In this week's episode, I also learned that if you, like Robert Hooke, end up dying without getting an image of yourself preserved for future generations, a science show will turn you into an evil, balding hunchback to increase the drama of a history lesson. So take selfies forever, I guess.
I also doubt that anyone ever told Hooke, “Put up or shut up.” Just saying.
The leap from Halley and Newton’s predictions to the 20th century’s Jan Oort and the Oort cloud works nicely as a tale about the power of prediction, but I think there was a missed opportunity. Amidst all those men associated with comets, the history of science includes a famous and remarkable woman whose fame is tied to comets.
A hundred years after Halley, Newton, and Hooke did battle, astronomers only knew of a handful of starry messengers, and French astronomer Charles Messier seems to have discovered most of them. Richard Holmes in The Age of Wonder (from whom most of this account is drawn) says only 30 were cataloged by the mid-18th century.
Then came Caroline Herschel. In a short stretch, she discovered eight new comets— the first woman known to have discovered a comet at all, and the most discovered by a woman until the 1980s Her brother, William, had established himself as one of the great telescope-makers, and had used one of those devices to discover the first new planet since the days of ancient Greece. (He wanted to name it “the Georgian planet,” after the reigning King of England, but in time Uranus was the name that stuck.) His telescopes were so sensitive that he discovered that certain stars were not stars at all, but distant galaxies like our own, and his telescopes were the first that could resolve individual stars within those distant galaxies. “These clusters,” he wrote, “may be the Laboratories of the universe…wherein the most salutary remedies for the decay of the whole are prepared.” That is, he realized that new stars were being born in distant galaxies, that stars have lifespans and that galaxies too are born, and evolve. The idea inspired one of Erasmus Darwin’s evolutionary poems.
Caroline Herschel discovered her first new galaxy in 1783. William had built her her own telescope, and she served as his assistant when he was making observations, and made the observations herself when he traveled, cataloging the stars all night, then calculating their exact locations all day. One night in 1786, as she examined the Big Dipper, she saw a star that didn’t belong. The next night, it had moved relative to the other stars. In her notebook, she wrote: “the object of last night IS A COMET.”
Caroline Herschel became a celebrity. Even today, female astronomers are a rare breed, and in 1786, they were unheard of. But Herschel had indeed discovered a new comet, and it was, in the words of Fanny Burney (a novelist and lady-in-waiting to Queen Charlotte), “the first lady’s comet.” She discovered more comets, wrote the first updated English catalog of stars since Newton’s day, and aided in the construction of a massive 40-foot telescope (then the largest ever built). Touring the half-built structure, King George led the Archbishop of Canterbury through the tube, quipping, “Come, my Lord Bishop, I will show you the way to heaven.” Franz Joseph Haydn credited a visit to the Herschels’ observatory with his oratorio The Creation.
In time, Caroline Herschel was given a royal stipend to continue her work (£50 per year, for life); she was the first woman in British history to be granted a royal salary to pursue scientific research (and possibly the first woman in the world hired to do science on the public dime). She was the first woman to receive the Gold Medal of the Astronomical Society of London (in 1828), and the last to receive one until Vera Rubin’s in 1996! The image on that medal: a bas relief of the Herschels’ 40-foot telescope.
Caroline Herschel sacrificed a great deal for her work. She was pox-marked and stunted from childhood disease (a mere 4’3”) and her family had abandoned any hope of her marrying. She pursued a career in music, but at her brother’s request she gave it up to serve as his assistant and housekeeper. At one point, she claimed, “I did nothing for my brother but what a well-trained puppy dog would have done, that is to say, I did what he commanded me,” a judgment history certainly would dispute. In proposing that she receive a royal salary, her brother acknowledged that he’d have to pay twice as much to hire a male assistant.
And yet she persevered, becoming one of the great scientists of her day, with her name attached to no fewer than 5 comets. Among her comets is the periodic comet 2P/Encke, the second periodic comet to have its return accurately predicted (after Halley’s, of course). | 0.887215 | 3.33593 |
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Experts at the Gemini Observatory took multiple snaps of the rogue space object, which were combined to create a colour image.
It shows the mysterious alien visitor being followed by a very pronounced tail.
Comet C/2019 Q4 as imaged by the Canada-France-Hawaii Telescope on Hawaii's Big Island.
Scientists are excited about a newly discovered comet that is dubbed Comet C/2019 Q4 as the comet appears to have originated from outside the solar system. The comet was discovered on August 30, 2019, by Gennady Borisov from the MARGO observatory in Nauchnij, Crimea. As of now, there has been no official confirmation that comet C/2019 Q4 is an interstellar comet.
This view of the interstellar object 'Oumuamua was captured by the 4.2-meter William Herschel Telescope in La Palma in Spain's Canary Islands.
Whether the structure was constructed by an extraterrestrial life or simply made of rock and dust brought together billions of years ago by primordial gravity, Oumuamua is definitely alien to our solar system.
originally posted by: LookingAtMars
These are the best images I could find of our first interstellar visitor Oumuamua.
On July 28, 2006, Victor Afanasiev from the Russian Academy of Sciences was making observations using a 6 meter telescope equipped with a multi-slit spectrometer. By chance, he observed the spectrum of a faint meteor as it burned up in the Earth’s atmosphere, and in looking at the data, found several anomalies. First was the speed at which the meteor was traveling. This meteor hit the atmosphere at about 300 kilometers per second, which is quite extraordinary. Only about 1% of meteors have velocities above 100 km/sec, and no previous meteor observations have yielded velocities of several hundred km/s. So where did this one come from?
Since the Earth moves around the galactic center at about 220 km/s, Afanasiev says the meteor’s origin cannot easily be explained by reference to the Milky Way. It appears that it came from the direction in which the Earth and the Milky Way is travelling towards the center of our local group of galaxies. “This fact leads us to conclude that we observed an intergalactic particle, which is at rest with respect to the mass centroid of the Local Group and which was ‘hit’ by the Earth,” Afanasiev and his team say in their paper. | 0.909098 | 3.259012 |
Another characteristic of the traditional Chinese calendar is the naming of the year. Early Chinese kings or emperors named the years after their own reigns, and so did the first few emperors of the Zhou dynasty. By the time of the Spring-and-Autumn period, the influence of the feudal princes increased as the power of the monarchy declined. Each feudal prince used a calendar named after his own reign within his own state. The Zuozhuan ^Efll and the Guoyu Hip, for example, adopt the calendar of the State of Lu. There was a need of some uniformity with so many different calendars in operation at the same period. Noticing Jupiter to return to the same spot in the heavens in about 12 years, 12 zones were marked along the equator, such that Jupiter would travel within one zone in 1 year and move over to the next in the following year and that winter solstice would lie at the centre of the first zone. The first zone was called Xingji JUE, followed in the west to east direction by Xuanxiao "2^, Zouzi Jianglou l5^ Daliang XM, Sbicben Jfit, Cbunshou SI'S", Chunhuo f.|X, Cbunwei IIM, Shouxing Si, Dahuo XX and Ximu ifyfc. These were the 12 Jupiterstations (shier ci <lX). Chinese astronomers in the Warring States period had already observed that the movement of Jupiter was not regular, sometimes progressing, sometimes stationary and sometimes retrograding. Probably this gave rise to the need to invent an imaginary Counter-Jupiter that moved uniformly in the opposite direction from east to west. When Jupiter was at Xingji Counter-Jupiter would be at yin J>i, when Jupiter moved to Xuanxiao the next year Counter-Jupiter would be in mao 9fl, and so on. Hence, instead of indicating a year by the position of Jupiter at the relevant
Jupiter-station, it was also possible and, in fact, more convenient to denote a year by the position of Counter-Jupiter upon the branches. This was called Taisui jinian i&jlL&E^ (Chronology Employing the Cycle of Counter-Jupiter).
Taisui jinian used the branch to denote the year. It was often used together with Suijun jinian H^IE^, which used the stem to denote the year. Ancient nomenclatures of the branches and the stems have in recent time become an unsolved puzzle to some historians of Chinese astronomy. When Counter-Jupiter was at the yin branch it was named Shetige SSfi!i§ and at each different branch it was given a different name. These names became synonymous with the names of the branches, i.e. zi corresponding to Kundun 03 JSt, chou to Chifenruo z^Hiir, yin to Shetige, mao to Shane chen to Zhixu si to Dahuangluo jZTn.fiI, wu to Dunzang Wi^-, wei to Xiexia ^hta, shen to Tuantan vfjiit, you to Zuoe f^fP, xu to Yanmao RSBc and hai to Dayuanxian These terms were already explained in the sixth century by Xiao Ji in his Wuxing dayi, which also took into account earlier explanations in the earlier Huainanzi and Erya,32 Nonetheless they sound strange or non-Han to some modern Chinese ears, but no foreign languages approximating to the sounds of these terms have been found. One suggestion is that they came from the language of some Chinese Minorities. The eminent astronomer and geographer Luoxia Hong ^TH (fl. second and first century bc), for example, is cited as coming from the Minorities tribes and not the majority Han. There was a similar set of rather strange names for the stems. As if to further complicate matters, but perhaps for the purpose of avoiding confusion over the years and the months, another set of names for the branches was used to denote the months.
Due to the precession of the equinoxes and the sidereal period of Jupiter being 11.86 rather than exactly 12 years, Jupiter would move gradually closer towards the next Jupiter-station after each year. After 84.7 years it would be found in the next station. This is what astronomers observing the movement of Jupiter referred to as 'Taisui chao chen (Counter-
Jupiter bypassing a branch). Jupiter-stations had long ceased to be used in the Chinese calendar. As is mentioned in Chapter 5, Shen Gua had already remarked on their being out of step with the calendar in the eleventh century. However, being an imaginary heavenly body, no observation was needed or could be made on the movement of Counter-Jupiter and it was not even necessary to know the actual position of Jupiter. The Chinese lunar calendar today still retains the system of Taisui jinian. Counter-Jupiter will feature prominently in Chapter 5 on the Liuren method, although it has a presence in the other two systems as well.
Much has been written on this intriguing subject that had engaged the attention of traditional scholars for well over 2,000 years and that still attracts the interest of modern scholars. The only purpose in describing it here is to provide the bare essentials for an understanding of the three cosmic boards. Therefore due precaution needs to be taken not to be sidetracked into this fascinating subject. It suffices to add that accounts of the system accompanied with excellent bibliographies can be found, for example, in Needham (1956) and Smith (1991). For a brief account of divination using the Yijing system see, for example, Ho Peng Yoke (1991d).33 We shall not concern ourselves here with the myriad schools of interpretations in the past nor with the discovery of the ancient order of the Hexagrams in modern archaeological excavation as they play no part in the understanding of the three cosmic boards.
In the Yijing, the Taiji ^C® (Supreme Pole or Supreme Ultimate) gives rise to the two cosmological forces (er yi —"91) Yin and Yang.iA Yin is represented by a broken line symbol and Yang by an unbroken line. Combinations of Yin and Yang produce the Four Symbols [si xiang H9 J^): Tai Yin ^fcPti with two Yin lines, Shao Yang with a Yang line above a Yin line, Shao Yin 'J^&i with a Yin line above a Yang line, and Tai Yang j^PM with two Yang lines. A further combination of Yin and Yang with each of the Four Symbols resulted in the Eight Trigrams (ba gua A#) qian $Z, kun zhen M, xun H, kan ifc, li gen d. and dui JnL (see Figure 2.9, the Eight Trigrams). Combinations of the Trigrams produced the Sixty-Four Hexagrams. For a long time, two different orders of arrangement of the gua, both Trigrams and Hexagrams, were talked about. One was the houtian ij^ (Later Heavens) order attributed to Wenwang X3E, father of the first emperor of the Zhou Dynasty in the eleventh century bc. The other was the xiantian (Prior to Heavens) order attributed to the legendary emperor taiji ±M
kunify gen Be kan ifc sun SI zhen m pit gentle quake thunder
'/' «I dui Ä qian ti separate exchange paternal heaven maternal limit earth
Fuxi tKli, although no earlier reference to it can be found before the time of Shao Yong (1011-1077). Even the houtian order attributed to Wenwang may not be that ancient because of its divergence from the arrangement of the text excavated from Mawangdui in the second half of the twentieth century. Much has been told regarding the connection of the xiantian order with the binary system of Leibniz. But the three cosmic boards were more concerned with the houtian system. Neither the binary arrangement in the xiantian order nor the Mawangdui arrangement plays a part at this stage. One needs only to refer to the diagrams in Needham (1956) that show the arrangement of the Hexagrams in the houtian order, as well as to Table 2.9 that indicates the connection between the Trigrams, Yin and Yang, the wuxing and the points of the compass. It is important to note the traditional Chinese convention of orienting the compass with S on top, W to the right, N at the bottom and E on the left, turned 180 degrees from our modern convention.35 This orientation was already pointed out in our discussion on the zibai or so-called colour-coded calendar.
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Achieve Health, Wealth And Body Balance Through Yin Yang Mastery. Cut up on the old stone drums of Republic of China, inscribed in books handed down through thousands of years, traced on ancient saucers and on saucers made today, is a sign and a symbol. It is woven into textiles, stitched into embroideries, emblazoned over house gates, wrought into shop emblems, a circle, locked together inside it yang and yin yang, light, yin, dark, each carrying inside itself the essence of the other, each shaped to the other | 0.861194 | 3.184175 |
Most of Earth’s essential elements for life — including most of the carbon and nitrogen in you — probably came from another planet.
Earth most likely received the bulk of its carbon, nitrogen and other life-essential volatile elements from the planetary collision that created the moon more than 4.4 billion years ago, according to a new study by Rice University petrologists in the journal Science Advances.
“From the study of primitive meteorites, scientists have long known that Earth and other rocky planets in the inner solar system are volatile-depleted,” said study co-author Rajdeep Dasgupta. “But the timing and mechanism of volatile delivery has been hotly debated. Ours is the first scenario that can explain the timing and delivery in a way that is consistent with all of the geochemical evidence.”
The evidence was compiled from a combination of high-temperature, high-pressure experiments in Dasgupta’s lab, which specializes in studying geochemical reactions that take place deep within a planet under intense heat and pressure.
In a series of experiments, study lead author and graduate student Damanveer Grewal gathered evidence to test a long-standing theory that Earth’s volatiles arrived from a collision with an embryonic planet that had a sulfur-rich core.
The sulfur content of the donor planet’s core matters because of the puzzling array of experimental evidence about the carbon, nitrogen and sulfur that exist in all parts of the Earth other than the core.
“The core doesn’t interact with the rest of Earth, but everything above it, the mantle, the crust, the hydrosphere and the atmosphere, are all connected,” Grewal said. “Material cycles between them.”
One long-standing idea about how Earth received its volatiles was the “late veneer” theory that volatile-rich meteorites, leftover chunks of primordial matter from the outer solar system, arrived after Earth’s core formed. And while the isotopic signatures of Earth’s volatiles match these primordial objects, known as carbonaceous chondrites, the elemental ratio of carbon to nitrogen is off. Earth’s non-core material, which geologists call the bulk silicate Earth, has about 40 parts carbon to each part nitrogen, approximately twice the 20-1 ratio seen in carbonaceous chondrites.
Grewal’s experiments, which simulated the high pressures and temperatures during core formation, tested the idea that a sulfur-rich planetary core might exclude carbon or nitrogen, or both, leaving much larger fractions of those elements in the bulk silicate as compared to Earth. In a series of tests at a range of temperatures and pressure, Grewal examined how much carbon and nitrogen made it into the core in three scenarios: no sulfur, 10 percent sulfur and 25 percent sulfur.
“Nitrogen was largely unaffected,” he said. “It remained soluble in the alloys relative to silicates, and only began to be excluded from the core under the highest sulfur concentration.”
Carbon, by contrast, was considerably less soluble in alloys with intermediate sulfur concentrations, and sulfur-rich alloys took up about 10 times less carbon by weight than sulfur-free alloys.
Using this information, along with the known ratios and concentrations of elements both on Earth and in non-terrestrial bodies, Dasgupta, Grewal and Rice postdoctoral researcher Chenguang Sun designed a computer simulation to find the most likely scenario that produced Earth’s volatiles. Finding the answer involved varying the starting conditions, running approximately 1 billion scenarios and comparing them against the known conditions in the solar system today.
“What we found is that all the evidence — isotopic signatures, the carbon-nitrogen ratio and the overall amounts of carbon, nitrogen and sulfur in the bulk silicate Earth — are consistent with a moon-forming impact involving a volatile-bearing, Mars-sized planet with a sulfur-rich core,” Grewal said.
Dasgupta, the principal investigator on a NASA-funded effort called CLEVER Planets that is exploring how life-essential elements might come together on distant rocky planets, said better understanding the origin of Earth’s life-essential elements has implications beyond our solar system.
“This study suggests that a rocky, Earth-like planet gets more chances to acquire life-essential elements if it forms and grows from giant impacts with planets that have sampled different building blocks, perhaps from different parts of a protoplanetary disk,” Dasgupta said.
“This removes some boundary conditions,” he said. “It shows that life-essential volatiles can arrive at the surface layers of a planet, even if they were produced on planetary bodies that underwent core formation under very different conditions.”
Dasgupta said it does not appear that Earth’s bulk silicate, on its own, could have attained the life-essential volatile budgets that produced our biosphere, atmosphere and hydrosphere.
“That means we can broaden our search for pathways that lead to volatile elements coming together on a planet to support life as we know it.” | 0.819464 | 3.842303 |
By the end of this section, you will be able to:
- Identify the physical characteristics of stars that are used to create an H–R diagram, and describe how those characteristics vary among groups of stars
- Discuss the physical properties of most stars found at different locations on the H–R diagram, such as radius, and for main sequence stars, mass
In this chapter and Analyzing Starlight, we described some of the characteristics by which we might classify stars and how those are measured. These ideas are summarized in Table 1. We have also given an example of a relationship between two of these characteristics in the mass-luminosity relation. When the characteristics of large numbers of stars were measured at the beginning of the twentieth century, astronomers were able to begin a deeper search for patterns and relationships in these data.
|Table 1. Measuring the Characteristics of Stars|
|Surface temperature||1. Determine the color (very rough).
2. Measure the spectrum and get the spectral type.
|Chemical composition||Determine which lines are present in the spectrum.|
|Luminosity||Measure the apparent brightness and compensate for distance.|
|Radial velocity||Measure the Doppler shift in the spectrum.|
|Rotation||Measure the width of spectral lines.|
|Mass||Measure the period and radial velocity curves of spectroscopic binary stars.|
|Diameter||1. Measure the way a star’s light is blocked by the Moon.
2. Measure the light curves and Doppler shifts for eclipsing binary stars.
To help understand what sorts of relationships might be found, let’s look briefly at a range of data about human beings. If you want to understand humans by comparing and contrasting their characteristics—without assuming any previous knowledge of these strange creatures—you could try to determine which characteristics lead you in a fruitful direction. For example, you might plot the heights of a large sample of humans against their weights (which is a measure of their mass). Such a plot is shown in Figure 1 and it has some interesting features. In the way we have chosen to present our data, height increases upward, whereas weight increases to the left. Notice that humans are not randomly distributed in the graph. Most points fall along a sequence that goes from the upper left to the lower right.
We can conclude from this graph that human height and weight are related. Generally speaking, taller human beings weigh more, whereas shorter ones weigh less. This makes sense if you are familiar with the structure of human beings. Typically, if we have bigger bones, we have more flesh to fill out our larger frame. It’s not mathematically exact—there is a wide range of variation—but it’s not a bad overall rule. And, of course, there are some dramatic exceptions. You occasionally see a short human who is very overweight and would thus be more to the bottom left of our diagram than the average sequence of people. Or you might have a very tall, skinny fashion model with great height but relatively small weight, who would be found near the upper right.
A similar diagram has been found extremely useful for understanding the lives of stars. In 1913, American astronomer Henry Norris Russell plotted the luminosities of stars against their spectral classes (a way of denoting their surface temperatures). This investigation, and a similar independent study in 1911 by Danish astronomer Ejnar Hertzsprung, led to the extremely important discovery that the temperature and luminosity of stars are related (Figure 2).
Henry Norris Russell
When Henry Norris Russell graduated from Princeton University, his work had been so brilliant that the faculty decided to create a new level of honors degree beyond “summa cum laude” for him. His students later remembered him as a man whose thinking was three times faster than just about anybody else’s. His memory was so phenomenal, he could correctly quote an enormous number of poems and limericks, the entire Bible, tables of mathematical functions, and almost anything he had learned about astronomy. He was nervous, active, competitive, critical, and very articulate; he tended to dominate every meeting he attended. In outward appearance, he was an old-fashioned product of the nineteenth century who wore high-top black shoes and high starched collars, and carried an umbrella every day of his life. His 264 papers were enormously influential in many areas of astronomy.
Born in 1877, the son of a Presbyterian minister, Russell showed early promise. When he was 12, his family sent him to live with an aunt in Princeton so he could attend a top preparatory school. He lived in the same house in that town until his death in 1957 (interrupted only by a brief stay in Europe for graduate work). He was fond of recounting that both his mother and his maternal grandmother had won prizes in mathematics, and that he probably inherited his talents in that field from their side of the family.
Before Russell, American astronomers devoted themselves mainly to surveying the stars and making impressive catalogs of their properties, especially their spectra (as described in Analyzing Starlight. Russell began to see that interpreting the spectra of stars required a much more sophisticated understanding of the physics of the atom, a subject that was being developed by European physicists in the 1910s and 1920s. Russell embarked on a lifelong quest to ascertain the physical conditions inside stars from the clues in their spectra; his work inspired, and was continued by, a generation of astronomers, many trained by Russell and his collaborators.
Russell also made important contributions in the study of binary stars and the measurement of star masses, the origin of the solar system, the atmospheres of planets, and the measurement of distances in astronomy, among other fields. He was an influential teacher and popularizer of astronomy, writing a column on astronomical topics for Scientific American magazine for more than 40 years. He and two colleagues wrote a textbook for college astronomy classes that helped train astronomers and astronomy enthusiasts over several decades. That book set the scene for the kind of textbook you are now reading, which not only lays out the facts of astronomy but also explains how they fit together. Russell gave lectures around the country, often emphasizing the importance of understanding modern physics in order to grasp what was happening in astronomy.
Harlow Shapley, director of the Harvard College Observatory, called Russell “the dean of American astronomers.” Russell was certainly regarded as the leader of the field for many years and was consulted on many astronomical problems by colleagues from around the world. Today, one of the highest recognitions that an astronomer can receive is an award from the American Astronomical Society called the Russell Prize, set up in his memory.
Features of the H–R Diagram
Following Hertzsprung and Russell, let us plot the temperature (or spectral class) of a selected group of nearby stars against their luminosity and see what we find (Figure 3). Such a plot is frequently called the Hertzsprung–Russell diagram, abbreviated H–R diagram. It is one of the most important and widely used diagrams in astronomy, with applications that extend far beyond the purposes for which it was originally developed more than a century ago.
It is customary to plot H–R diagrams in such a way that temperature increases toward the left and luminosity toward the top. Notice the similarity to our plot of height and weight for people (Figure 1). Stars, like people, are not distributed over the diagram at random, as they would be if they exhibited all combinations of luminosity and temperature. Instead, we see that the stars cluster into certain parts of the H–R diagram. The great majority are aligned along a narrow sequence running from the upper left (hot, highly luminous) to the lower right (cool, less luminous). This band of points is called the main sequence. It represents a relationship between temperature and luminosity that is followed by most stars. We can summarize this relationship by saying that hotter stars are more luminous than cooler ones.
A number of stars, however, lie above the main sequence on the H–R diagram, in the upper-right region, where stars have low temperature and high luminosity. How can a star be at once cool, meaning each square meter on the star does not put out all that much energy, and yet very luminous? The only way is for the star to be enormous—to have so many square meters on its surface that the total energy output is still large. These stars must be giants or supergiants, the stars of huge diameter we discussed earlier.
There are also some stars in the lower-left corner of the diagram, which have high temperature and low luminosity. If they have high surface temperatures, each square meter on that star puts out a lot of energy. How then can the overall star be dim? It must be that it has a very small total surface area; such stars are known as white dwarfs (white because, at these high temperatures, the colors of the electromagnetic radiation that they emit blend together to make them look bluish-white). We will say more about these puzzling objects in a moment. Figure 4 is a schematic H–R diagram for a large sample of stars, drawn to make the different types more apparent.
Now, think back to our discussion of star surveys. It is difficult to plot an H–R diagram that is truly representative of all stars because most stars are so faint that we cannot see those outside our immediate neighborhood. The stars plotted in Figure 3 were selected because their distances are known. This sample omits many intrinsically faint stars that are nearby but have not had their distances measured, so it shows fewer faint main-sequence stars than a “fair” diagram would. To be truly representative of the stellar population, an H–R diagram should be plotted for all stars within a certain distance. Unfortunately, our knowledge is reasonably complete only for stars within 10 to 20 light-years of the Sun, among which there are no giants or supergiants. Still, from many surveys (and more can now be done with new, more powerful telescopes), we estimate that about 90% of the true stars overall (excluding brown dwarfs) in our part of space are main-sequence stars, about 10% are white dwarfs, and fewer than 1% are giants or supergiants.
These estimates can be used directly to understand the lives of stars. Permit us another quick analogy with people. Suppose we survey people just like astronomers survey stars, but we want to focus our attention on the location of young people, ages 6 to 18 years. Survey teams fan out and take data about where such youngsters are found at all times during a 24-hour day. Some are found in the local pizza parlor, others are asleep at home, some are at the movies, and many are in school. After surveying a very large number of young people, one of the things that the teams determine is that, averaged over the course of the 24 hours, one-third of all youngsters are found in school.
How can they interpret this result? Does it mean that two-thirds of students are truants and the remaining one-third spend all their time in school? No, we must bear in mind that the survey teams counted youngsters throughout the full 24-hour day. Some survey teams worked at night, when most youngsters were at home asleep, and others worked in the late afternoon, when most youngsters were on their way home from school (and more likely to be enjoying a pizza). If the survey was truly representative, we can conclude, however, that if an average of one-third of all youngsters are found in school, then humans ages 6 to 18 years must spend about one-third of their time in school.
We can do something similar for stars. We find that, on average, 90% of all stars are located on the main sequence of the H–R diagram. If we can identify some activity or life stage with the main sequence, then it follows that stars must spend 90% of their lives in that activity or life stage.
Understanding the Main Sequence
In The Sun: A Nuclear Powerhouse, we discussed the Sun as a representative star. We saw that what stars such as the Sun “do for a living” is to convert protons into helium deep in their interiors via the process of nuclear fusion, thus producing energy. The fusion of protons to helium is an excellent, long-lasting source of energy for a star because the bulk of every star consists of hydrogen atoms, whose nuclei are protons.
Our computer models of how stars evolve over time show us that a typical star will spend about 90% of its life fusing the abundant hydrogen in its core into helium. This then is a good explanation of why 90% of all stars are found on the main sequence in the H–R diagram. But if all the stars on the main sequence are doing the same thing (fusing hydrogen), why are they distributed along a sequence of points? That is, why do they differ in luminosity and surface temperature (which is what we are plotting on the H–R diagram)?
To help us understand how main-sequence stars differ, we can use one of the most important results from our studies of model stars. Astrophysicists have been able to show that the structure of stars that are in equilibrium and derive all their energy from nuclear fusion is completely and uniquely determined by just two quantities: the total mass and the composition of the star. This fact provides an interpretation of many features of the H–R diagram.
Imagine a cluster of stars forming from a cloud of interstellar “raw material” whose chemical composition is similar to the Sun’s. (We’ll describe this process in more detail in The Birth of Stars and Discovery of Planets outside the Solar System, but for now, the details will not concern us.) In such a cloud, all the clumps of gas and dust that become stars begin with the same chemical composition and differ from one another only in mass. Now suppose that we compute a model of each of these stars for the time at which it becomes stable and derives its energy from nuclear reactions, but before it has time to alter its composition appreciably as a result of these reactions.
The models calculated for these stars allow us to determine their luminosities, temperatures, and sizes. If we plot the results from the models—one point for each model star—on the H–R diagram, we get something that looks just like the main sequence we saw for real stars.
And here is what we find when we do this. The model stars with the largest masses are the hottest and most luminous, and they are located at the upper left of the diagram.
The least-massive model stars are the coolest and least luminous, and they are placed at the lower right of the plot. The other model stars all lie along a line running diagonally across the diagram. In other words, the main sequence turns out to be a sequence of stellar masses.
This makes sense if you think about it. The most massive stars have the most gravity and can thus compress their centers to the greatest degree. This means they are the hottest inside and the best at generating energy from nuclear reactions deep within. As a result, they shine with the greatest luminosity and have the hottest surface temperatures. The stars with lowest mass, in turn, are the coolest inside and least effective in generating energy. Thus, they are the least luminous and wind up being the coolest on the surface. Our Sun lies somewhere in the middle of these extremes (as you can see in Figure 3. The characteristics of representative main-sequence stars (excluding brown dwarfs, which are not true stars) are listed in Table 2.
|Table 2. Characteristics of Main-Sequence Stars|
|Spectral Type||Mass (Sun = 1)||Luminosity (Sun = 1)||Temperature||Radius (Sun = 1)|
|O5||40||7 × 105||40,000 K||18|
|B0||16||2.7 × 105||28,000 K||7|
Note that we’ve seen this 90% figure come up before. This is exactly what we found earlier when we examined the mass-luminosity relation. We observed that 90% of all stars seem to follow the relationship; these are the 90% of all stars that lie on the main sequence in our H–R diagram. Our models and our observations agree.
What about the other stars on the H–R diagram—the giants and supergiants, and the white dwarfs? As we will see in the next few chapters, these are what main-sequence stars turn into as they age: They are the later stages in a star’s life. As a star consumes its nuclear fuel, its source of energy changes, as do its chemical composition and interior structure. These changes cause the star to alter its luminosity and surface temperature so that it no longer lies on the main sequence on our diagram. Because stars spend much less time in these later stages of their lives, we see fewer stars in those regions of the H–R diagram.
Extremes of Stellar Luminosities, Diameters, and Densities
We can use the H–R diagram to explore the extremes in size, luminosity, and density found among the stars. Such extreme stars are not only interesting to fans of the Guinness Book of World Records; they can teach us a lot about how stars work. For example, we saw that the most massive main-sequence stars are the most luminous ones. We know of a few extreme stars that are a million times more luminous than the Sun, with masses that exceed 100 times the Sun’s mass. These superluminous stars, which are at the upper left of the H–R diagram, are exceedingly hot, very blue stars of spectral type O. These are the stars that would be the most conspicuous at vast distances in space.
The cool supergiants in the upper corner of the H–R diagram are as much as 10,000 times as luminous as the Sun. In addition, these stars have diameters very much larger than that of the Sun. As discussed above, some supergiants are so large that if the solar system could be centered in one, the star’s surface would lie beyond the orbit of Mars (see Figure 5). We will have to ask, in coming chapters, what process can make a star swell up to such an enormous size, and how long these “swollen” stars can last in their distended state.
In contrast, the very common red, cool, low-luminosity stars at the lower end of the main sequence are much smaller and more compact than the Sun. An example of such a red dwarf is Ross 614B, with a surface temperature of 2700 K and only 1/2000 of the Sun’s luminosity. We call such a star a dwarf because its diameter is only 1/10 that of the Sun. A star with such a low luminosity also has a low mass (about 1/12 that of the Sun). This combination of mass and diameter means that it is so compressed that the star has an average density about 80 times that of the Sun. Its density must be higher, in fact, than that of any known solid found on the surface of Earth. (Despite this, the star is made of gas throughout because its center is so hot.)
The faint, red, main-sequence stars are not the stars of the most extreme densities, however. The white dwarfs, at the lower-left corner of the H–R diagram, have densities many times greater still.
The White Dwarfs
The first white dwarf star was detected in 1862. Called Sirius B, it forms a binary system with Sirius A, the brightest-appearing star in the sky. It eluded discovery and analysis for a long time because its faint light tends to be lost in the glare of nearby Sirius A (Figure 5). (Since Sirius is often called the Dog Star—being the brightest star in the constellation of Canis Major, the big dog—Sirius B is sometimes nicknamed the Pup.)
We have now found thousands of white dwarfs. A Stellar Census shows that about 7% of the true stars (spectral types O–M) in our local neighborhood are white dwarfs. A good example of a typical white dwarf is the nearby star 40 Eridani B. Its surface temperature is a relatively hot 12,000 K, but its luminosity is only 1/275 LSun. Calculations show that its radius is only 1.4% of the Sun’s, or about the same as that of Earth, and its volume is 2.5 × 10–6 that of the Sun. Its mass, however, is 0.43 times the Sun’s mass, just a little less than half. To fit such a substantial mass into so tiny a volume, the star’s density must be about 170,000 times the density of the Sun, or more than 200,000 g/cm3. A teaspoonful of this material would have a mass of some 50 tons! At such enormous densities, matter cannot exist in its usual state; we will examine the particular behavior of this type of matter in The Death of Stars. For now, we just note that white dwarfs are dying stars, reaching the end of their productive lives and ready for their stories to be over.
The British astrophysicist (and science popularizer) Arthur Eddington (1882–1944) described the first known white dwarf this way:
The message of the companion of Sirius, when decoded, ran: “I am composed of material three thousand times denser than anything you’ve ever come across. A ton of my material would be a little nugget you could put in a matchbox.” What reply could one make to something like that? Well, the reply most of us made in 1914 was, “Shut up; don’t talk nonsense.”
Today, however, astronomers not only accept that stars as dense as white dwarfs exist but (as we will see) have found even denser and stranger objects in their quest to understand the evolution of different types of stars.
Key Concepts and Summary
The Hertzsprung–Russell diagram, or H–R diagram, is a plot of stellar luminosity against surface temperature. Most stars lie on the main sequence, which extends diagonally across the H–R diagram from high temperature and high luminosity to low temperature and low luminosity. The position of a star along the main sequence is determined by its mass. High-mass stars emit more energy and are hotter than low-mass stars on the main sequence. Main-sequence stars derive their energy from the fusion of protons to helium. About 90% of the stars lie on the main sequence. Only about 10% of the stars are white dwarfs, and fewer than 1% are giants or supergiants.
H–R diagram: (Hertzsprung–Russell diagram) a plot of luminosity against surface temperature (or spectral type) for a group of stars
main sequence: a sequence of stars on the Hertzsprung–Russell diagram, containing the majority of stars, that runs diagonally from the upper left to the lower right
white dwarf: a low-mass star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size; such a star is near its final state of life | 0.855607 | 3.931114 |
ASTEROIDS AND COMETS
Charles R. Alcock (Department of Astronomy) Freshman Seminar 23R 4 credits (fall term) Enrollment: Limited to 12 Note: The seminar will make use of the Clay Telescope on the roof of the Science Center. There may also be a trip to the Observatory at 60 Garden Street to visit the Great Refractor.
Comets have been seen regularly since before the beginning of recorded history. They have often been regarded as disturbing portents. Asteroids, on the other hand, were not discovered until the 19th century, with the advent of astronomy with telescopes. Today we know of many more asteroids than comets, but we believe that there are vastly more comets than asteroids in the solar system. This seminar will start with the history of the study of comets and asteroids, including the “Great March Comet of 1843,” observations of which led to the establishment of the Harvard College Observatory and its Great Refractor, at the time the largest telescope in the Americas. Our understanding of comets advanced dramatically in 1950 with the publication of two extraordinary papers: Whipple (then at Harvard) described the mixture of dust and ice that comprises the nuclei of comets, and Oort (Leiden University) showed that new comets enter the inner solar system from a vast, diffuse cloud surrounding the planetary system. Modern telescopes and spacecraft encounters provide us today with a wealth of information about comets and asteroids. We will examine these observations and learn what is known and what is inferred about the origin and structure of asteroids and comets. The students will observe with the Astronomy Laboratory’s Clay Telescope on the roof of the Science Center. Students will take on projects, which may involve their own observing program, or which exploit existing data.
BLACK HOLES, STRING THEORY AND THE FUNDAMENTAL LAWS OF NATURE
Andrew Strominger (Department of Physics) Freshman Seminar 21V 4 credits (fall term) Enrollment: Limited to 12
The quest to understand the fundamental laws of nature has been ongoing for centuries. This seminar will assess the current status of this quest. In the first five weeks, we will cover the basic pillars of our understanding: Einstein’s theory of general relativity, quantum mechanics and the Standard Model of particle physics. We will then examine the inadequacies and inconsistencies in our current picture, including, for example, the problem of quantum gravity, the lack of a unified theory of forces, Dirac’s large numbers problem, the cosmological constant problem, Hawking’s black hole information paradox, and the absence of a theory for the origin of the universe. Attempts to address these issues and move beyond our current understanding involve a network of intertwined investigations in string theory, M theory, inflation and non-abelian gauge theories and have drawn inspiration from the study of black holes and developments in modern mathematics. These forays beyond the edge of our current knowledge will be reviewed and assessed. The format of the course will be discussion of weekly reading assignments and a final paper. Non-scientists are welcome. COSMIC EXPLOSIONS Edo Berger (Department of Astronomy) Freshman Seminar 21C 4 credits (spring term) Enrollment: Limited to 12 Somewhere in the universe a massive star ends its life in a supernova explosion every second (you can count: “1 supernova, 2 supernova, 3 supernova…”). These supernovae, and other types of cosmic explosions like them, play a critical role in shaping the universe. They are responsible for the synthesis and dispersal of all the chemical elements heavier than hydrogen and helium, and, therefore, provide the building blocks for the next generations of stars, for planets and ultimately for life. These cosmic explosions also give birth to exotic objects, such as neutron stars and black holes. Finally, the explosions are so powerful that they can influence the formation of new stars within their galaxies. In this seminar, we will explore how different types of cosmic explosions occur and how they influence the universe and life within it. Equally important, we will actually use telescopes in Cambridge and in Arizona to study a new supernova explosion during the semester.
HOW DID THE FIRST STARS AND GALAXIES FORM?
Abraham Loeb (Department of Astronomy) Freshman Seminar 21G 4 credits (spring term) Enrollment: Limited to 12
Since the universe is expanding, it must have been denser in the past. But even before we get all the way back to the Big Bang, there must have been a time when stars like our sun or galaxies like our own Milky Way did not exist, because the universe was denser than they are. We, therefore, face the important question about our origins: How and when did the first stars and galaxies form? Primitive versions of this question were considered by humans in religious and philosophical texts for thousands of years, long before it was realized that the universe expands. The Seminar will summarize the fundamental principles and scientific ideas that are being used to address this question in modern cosmology. Previous generations of scholars have also wondered about the long-term future of the universe. For the first time in history, we now have a standard cosmological model that agrees with a large body of data about the past history of the universe. The seminar will conclude with the forecast that this scientific model makes about our future. It will be based on a book with the same title written by Professor Loeb (Princeton University Press, 2010). PHYSICS AND BIG QUESTIONS Gerald Gabrielse (Department of Physics) Freshman Seminar 22V 4 credits (spring term) Enrollment: Limited to 12 Three types of big questions will be considered. The first are the big questions about the limits and domain of physics. To start, what are the limits and domain of applicability of the classical physics studies studied in high school? How do these relate to special relativity, quantum mechanics and quantum field theory? Next, what are some of the big questions that physics seeks to answer. For example, what is the “standard model” of particle physics, and how is it tested? Other important big questions relate to how physics informs some major challenges to our society. For example, what does physics say about the options for powering our homes and cars, given limited petroleum reserves and the need to reduce carbon dioxide production? The final set of big questions is about the compatibility or incompatibility of physics and religious faith. Here we will consider very divergent answers in a climate of respect for what will be big differences in opinion.
FROM GALILEO TO THE BIG BANG THEORY: CONFLICT AND DIALOGUE BETWEEN RELIGION AND SCIENCE
Karin Öberg (Department of Astronomy) Freshman Seminar 50S 4 credits (fall term) Enrollment: Limited to 12
Prerequisites: The seminar will include scientific concepts and their empirical and theoretical
foundations, but no scientific preparation beyond high school physics is required.
It is easy to find controversies at the intersection of science and religion, from the time of Galileo, to
Darwin and the emergence of modern cosmology. Yet many scientists throughout the ages have been
devoutly religious, challenging claims of an intrinsic enmity between science and religion. This seminar treats a number of historical conflicts between religious beliefs and scientific theories, among
them the Galileo affair, the clockwork universe, evolution, and the Big Bang theory. The seminar
will introduce students to the main protagonists through their own words, and through contemporary and modern-day commentaries. We will explore why these conflicts arose and, based on these
historical lessons, what we can expect the future relationship between science and religion to be.
The ultimate aim of this seminar is for students to form their own opinion of which kind of conflicts
between science and religion are inevitable and which are accidents of time and place, and under
which conditions, if any, interactions between science and religion can be mutually beneficial. Most
of the seminar will focus on Christianity and the natural sciences, with emphasis on astronomy and
cosmology, but the relationship between other ancient and contemporary religions and other sciences
will be discussed as well to provide a broader context.
THE TEMPORAL UNIVERSE
Jonathan E. Grindlay (Department of Astronomy) Freshman Seminar 50I 4 credits (spring term) Enrollment: Limited to 12 Note: This seminar is open to all but may be of particular interest to those considering physical science or engineering concentrations.
The universe is not static, but rather stars and entire galaxies are evolving as revealed by their variability on timescales ranging from giga-years for galaxies to milliseconds for collapsed stars (neutron stars and black holes). In this seminar, we shall explore stars and galaxies through variability—from how brightness variability of stars with binary companions measured with small telescopes measures star masses and radii, to the extremes of variability of stars that undergo repeated huge flares, to enormously luminous variations from accretion onto gargantuan black holes in the nuclei of “Active Galaxies” (Blazars and Quasars). We shall use the Clay Telescope on the Science Center roof to make some repeated observations (from the 8th floor Astronomy Lab) of an example of each of these two types of variable stars and deduce what life would be like if either were our sun. From a Blazar, we shall observe historical outbursts that occasionally change brightness to exceed its host galaxy by a factor of ~100, by using the digitized brightness measures of this object on thousands of glass-plate images taken by Harvard telescopes from 1885 to 1992 and now digitized and online from our Digital Access to a Sky Century @ Harvard (DASCH) project. The seminar will include readings from an introductory astronomy text, as well as both popular and journal articles and the short book Black Hole (Bartusiak). Students will use astronomical software to measure stellar brightness and variability from telescope images, as well as learn temporal analysis techniques with applications to other disciplines. Students discuss in class readings and observations conducted and write short papers on their observations and deductions.
THE UNIVERSE’S HIDDEN DIMENSIONS
Lisa Randall (Department of Physics) Freshman Seminar 26J 4 credits (spring term) Enrollment: Limited to 12
This seminar will give an overview and introduction to modern physics. As with the book, Warped Passages, on which it will be loosely based, the seminar will first consider the revolutionary developments of the early twentieth century: quantum mechanics and general relativity; and then it will investigate the key concepts which separated these developments from the physical theories which previously existed. We will then delve into modern particle physics and how theory and experiment culminated in the “Standard Model of particle physics,” which physicists use today. Then we will move beyond the Standard Model into more speculative arenas, including supersymmetry, string theory, and theories of extra dimensions of space. We will consider the motivations underlying these theories, their current status, and how we might hope to test some of the underlying ideas in the near future.
EXPLORING THE INFINITE
Peter Koellner (Department of Philosophy) & W. Hugh Woodin (Department of Mathematics and of Philosophy)
Freshman Seminar 23C 4 credits (spring term) Enrollment: Limited to 12
Infinity captivates the imagination. A child stands between two mirrors and sees herself reflected over and over again, smaller and smaller, trailing off to infinity. Does it go on forever? … Does anything go on forever? Does life go on forever? Does time go on forever? Does the universe go on forever? Is there anything that we can be certain goes on forever? ... It would seem that the counting numbers go on forever, since given any number on can always add one. But is that the
extent of forever? Or are there numbers that go beyond that? Are there higher and higher levels of infinity? And, if so, does the totality of all of these levels of infinity itself constitute the highest, most ultimate, level of infinity, the absolutely infinite? In this seminar we will focus on the mathematical infinite. We will start with the so-called “paradoxes of the infinite,” paradoxes that have led some to the conclusion that the concept of infinity is incoherent. We will see, however,
that what these paradoxes ultimately show is that the infinite is just quite different than the finite and that by being very careful we can sharpen the concept of infinity so that these paradoxes are transformed into surprising discoveries. We will follow the historical development, starting with the work of Cantor at the end of the nineteenth century, and proceeding up to the present. The study of the infinite has blossomed into a beautiful branch of mathematics. We will get a glimpse of this subject, and the many levels of infinity, and we will see that the infinite is even more magnificent than one might ever have imagined. | 0.887269 | 3.801714 |
Outer space, or simply space, is the expanse that exists beyond the Earth and between celestial bodies. Outer space is not completely empty—it is a hard vacuum containing a low density of particles, predominantly a plasma of hydrogen and helium, as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays. The baseline temperature of outer space, as set by the background radiation from the Big Bang, is 2. 7 kelvins (−270. 45 °C; −454. 81 °F). The plasma between galaxies accounts for about half of the baryonic (ordinary) matter in the universe; it has a number density of less than one hydrogen atom per cubic metre and a temperature of millions of kelvins. Local concentrations of matter have condensed into stars and galaxies. Studies indicate that 90% of the mass in most galaxies is in an unknown form, called dark matter, which interacts with other matter through gravitational but not electromagnetic forces. Observations suggest that the majority of the mass-energy in the observable universe is dark energy, a type of vacuum energy that is poorly understood. Intergalactic space takes up most of the volume of the universe, but even galaxies and star systems consist almost entirely of empty space. | 0.804457 | 3.655231 |
Does Martian Methane Mean Life On Mars?
Mars just seems to be the one planet (aside from our own, of course) that we humans can’t get enough of. For hundreds of years, we’ve been writing about it, wondering if Martians are going to come to visit us or hoping Matt Damon can get home from the strange Red Planet. Let’s face it: we’re obsessed. But there’s a good reason for us to be; with so many interesting discoveries and potential signs of life, Mars just keeps pulling us in. And now, with recent discoveries about methane on the Red Planet, we may be one step closer to discovering life on Mars.
Recent Methane Discoveries
Scientists have known for a while that there’s methane on Mars. In fact, they even know it goes through cycles of intensity. While background levels of methane on some parts of Mars normally hover around .24-.65 ppb (parts per billion), the levels do increase, and peak during the northern summer on the planet. Our favorite Martian robot, Curiosity, however, recently discovered something pretty weird about those methane levels.
Back in 2013, Curiosity detected an enormous spike of methane levels on Mars. The levels jumped to 6ppb, which is a huge difference compared to the usual background levels of methane on the planet. But that’s not even the biggest spike. Just a day later, a group of researchers led by Marco Giuranna saw another huge spike, this time all the way up at 15.5ppb. That’s an enormous difference!
Verifying This Is Actually Anything But Easy
Considering all the equipment we have trained on Mars, verifying these methane levels are anything but straightforward (these 2013 observations were only verified recently). When Curiosity first detected the spike, some scientists thought it must have been an equipment fluke or malfunction, because the levels were simply so high. When Giuranna’s team noticed the secondary spike (which was a totally accidental overlap of observations), scientists were more willing to accept that the findings were accurate.
Despite all the technology we have to study this planet, it’s actually really hard to observe methane emissions. Spacecraft that are orbiting the Red Planet have a hard time documenting methane just because there’s so little of the gas, and because it has weak absorption. It’s surprisingly hard to measure Mars’ methane levels from Earth, too, because our planet has so much methane that it interferes with observations of our planetary neighbor.
So, Where Is All This Methane Coming From?
Curiosity found its methane spike about 300 miles east of the Gale Crater on Mars, in an area called Aeolis Mensae. By sheer dumb luck, Giuranna’s team was observing the same area, which is how they were able to combine and compare observations. But those observations weren’t enough to determine the exact source of the methane.
To try to determine exactly where this methane was coming from, scientists divided the Gale Crater area into large squares and ran computer simulations (one million of them) to determine possible sources that may be emitting the gas. They also studied the squares to try to find probable methane sources with physical observations. To their surprise, even though the two studies were conducted separately, they both pointed towards the probability that the methane gas had been trapped under ice. When the ice was broken, the methane gas was probably released.
Could Methane Mean Life?
We’re still not sure if the methane was emitted recently, or if it’s been sitting under the ice for eons and only recently released from the ice. But what’s really interesting is that methane is usually a gas produced by microbial life forms. While it can also be produced by other things (like your typical everyday chemical reaction), some scientists remain hopeful that the methane could reveal traces of life forms, even if they are trapped beneath the ice. We’re far from a certain answer, but with more discoveries like this, we grow closer to an answer every day. | 0.862424 | 3.731604 |
And now, a beast fiercer than Godzilla, more terrifying than Jaws — ladies and gents, I give you … Claws.
But you can’t see this monster in theatres or on the Internet. You’ll have to stay up until midnight or so to see this one among an odd tableau of constellations in the south.
Low in the southeast is Scorpius, the giant scorpion, rising just above the horizon. To the south, just to the right of the beast, you’ll see Libra, the Scales, or if you prefer, the Balance.
Based on a comment by one of the younger patrons at Perkins, I must digress here. We are not talking the kind of scales one might find on a fish or to answer the young person directly, a dragon. Instead, I’m referring to the two-sided balancing device used to measure the weight of something.
Where was I? Oh, yes.
Libra gets its ancient identity from two nearby constellations. Setting in the southwest, Virgo, the innocent virgin, is being chased by the scorpion, which is rising in the southeast.
Libra originally was considered too dim to be a constellation on its own. The ancient Greeks combined it with Scorpius to make up a larger super-monster that made Jaws look like a guppy.
The ancient Greeks called the Libra “Chelae,” which means Claws. The two brightest stars of Libra were commonly identified as the claws of the scorpion. In fact, they still bear the Arabic names that mark them as such. Zubenelschamali (pronounced just like it’s spelled — ha), the Northern Claw, is the upper star. Zubenelgenubi (try saying that one three times fast), the Southern Claw, is the lower star.
Scorpius is one of the nastiest constellations, with its broad head at the top and its deadly stinger curving down and to the left. Add the claws and you have one of the largest and cruelest-looking star groups in the sky.
Later, the Romans saw this area of sky as a set of scales, partly because the two Zubens are more or less similar in brightness. But there’s another reason.
Libra is a zodiacal constellation, one of the star groups through which the sun, moon, and planets pass as they travel across the sky.
The sun appeared in Libra on the autumnal equinox, a day during which daylight and nighttime are evenly divided. Here then was the balance point of heaven.
The Romans, who considered themselves a balanced lot, believed that Rome’s favored status among the gods resulted in part from the fact that the moon had been traveling through Libra when the city of Rome was established.
Libra’s favored status presented a problem. Libra is the only sign of the zodiac that is an inanimate object. It therefore must be owned by another constellation. Scorpions don’t have a use for scales, so the association had to go.
Luckily, Virgo sits on the other side of Libra. She was sometimes identified as Dike. The name is pronounced DEE-kay, just as Nike, the goddess of Victory, is technically pronounced NEE-kay. The shoe manufacturer can pronounce it any way they want, of course.
Dike was the goddess of justice. We see her to this very day in front of court buildings — blind justice with her scales raised high, holding the rule of law in the balance. In the Roman version of Libra, the goddess of Justice, Virgo, is holding high the balanced scales of justice, Libra.
There is, of course, something to be learned from this. The evil scorpion sometimes seems to rule for a time, but eventually the rules of justice and equality and the impulse of our common humanity will triumph. As Martin Luther King most famously said, “The arc of the moral universe is long, but it bends toward justice.” So it is written here on Earth, and so it is written among the stars.
Let us fervently hope that eventually we will come to say, as the Romans seemed to say so long ago, “Malevolent scorpion, where is your sting? Sweet justice has stolen your claws.”
Celebration of the Sun at Perkins Observatory
July is the cruelest month for stargazers because the sun doesn’t get out of the way of nighttime observing until after 10:30 p.m. or so.
Thus, during three days in July, Perkins Observatory spends its Saturday late-afternoons celebrating our daystar by observing it safely with our battery of solar-safe telescopes.
Programs start at 4 p.m. on July 14, 21 and 28. We strongly recommend that you purchase your tickets ahead of time by calling 740-363-1257. Tickets are $10 for adults and $8 for seniors and children when they are purchased in advance.
In addition, we’ll also be talking about the sun, launching rockets, and giving observatory tours that emphasize its solar features.
The solar celebration programs are among the last ones I will be conducting as director of Perkins Observatory. I’m hoping that y’all will come and celebrate my quarter century at Perkins by attending one of the programs.
Call 740-363-1257 for details or to preorder tickets.
Look for bright Venus low in the west during deep evening twilight. Venus has phases just like the moon, but Venus takes 248 days to cycle through its phases as the planet travels around the sun. Right now, the planet is in its “half-Venus” phase.
Jupiter, almost as bright as Venus, hovers near much fainter Zubenelgenubi in the south after it gets completely dark.
How bright is Jupiter? Not quite as bright as Venus but bright enough that it is unmistakable. It’s probably easier to see Jupiter to find the constellation Libra than it is to use Libra to find Jupiter.
Use binoculars to glimpse three or four of Jupiter’s brightest moons lined up close around the planet.
Saturn is that yellowish point of light above the teapot-shaped constellation Sagittarius. Look for it low in the southeast after midnight. Binoculars won’t help you much here. You’ll need at least a small to see its fabulous rings.
Mars is engaged in one of its 17-year closest approaches to Earth. Look for it low in the southeast around 3 AM amidst the faint stars of Capricornus. It’s easy to pick it out with the unaided eye. The so-called “red planet” will look like a bright, yellow-orange star.
However, even at its current best, Mars never fails to disappoint, even in a large telescope. You might see a white polar cap or two and perhaps some greenish markings on the surface.
I’d suggest coming to one of the Friday night programs at Perkins in August if you want to get a half-way-decent view of it. Call 740-363-1257 for details.
Tom Burns is director of the Perkins Observatory in Delaware. | 0.832303 | 3.271827 |
NASA’s Hubble Space Telescope is responsible for capturing some of the most detailed images of distant galaxies, but it isn’t particularly useful when it comes to photographing closer objects like Pluto and other trans-Neptunian objects in our solar system.
As it would seem, this has to do with the angular diameter of the object in question. The size and distance of the said object are incredibly significant factors in determining Hubble’s ability to view it clearly. Pluto is much closer than any galaxy, but it’s also insignificantly tiny, which makes it tougher to focus on. Galaxies, although much farther away, are massive.
One of the best photographs ever taken of the Andromeda galaxy was resolved with the Hubble Space Telescope, and it’s comprised of several smaller photographs because the galaxy is so large that the whole thing wouldn’t fit in Hubble’s viewfinder.
The next time you wonder why Hubble can’t photograph Pluto as clearly as it can galaxies, or even larger planets, remember that it has to do with Pluto’s size and distance relative to our location in the Solar System. | 0.834755 | 3.221952 |
We're learning more about the gigantic storms and turbulent atmosphere of the solar system's largest planet, Jupiter.
A trio of NASA instruments – the Hubble Space Telescope, the ground-based Gemini Observatory in Hawaii and the Juno spacecraft that's orbiting Jupiter – have teamed up to probe the mightiest storms in the solar system, taking place more than 500 million miles away on the giant planet.
"We want to know how Jupiter's atmosphere works," said Michael Wong, a planetary scientist at the University of California-Berkeley. "This is where the teamwork of Juno, Hubble and Gemini comes into play."
One recently released image from NASA shows Jupiter as a giant "jack-o'-lantern," where the warm, deep layers of Jupiter's atmosphere glow through gaps in the planet's thick cloud cover.
"It's kind of like a jack-o'-lantern," Wong said. "You see bright infrared light coming from cloud-free areas, but where there are clouds, it's really dark in the infrared."
That image was taken by the Gemini Observatory and is among the highest-resolution images of Jupiter ever obtained from the ground.
Wong said Gemini is the most effective way for scientists to get detailed images of Jupiter in the infrared wavelength. Gemini achieved a 300-mile resolution on Jupiter, which is impressive considering Jupiter is 500 million miles away.
"At this resolution, the telescope could resolve the two headlights of a car in Miami, seen from New York City," said Andrew Stephens, the Gemini astronomer who led the observations.
The new observations also confirm that dark spots in the planet's famous Great Red Spot are actually gaps in the cloud cover and not because of cloud color variations.
In addition, the Juno spacecraft detected hundreds of lightning strikes around Jupiter's poles, which NASA said is the opposite of Earth, where lightning is most common around the equator.
Jupiter's constant storms are gigantic compared to those on Earth. Thunderhead clouds reach 40 miles from base to top – five times taller than typical thunderheads on Earth – and powerful lightning flashes up to three times more energetic than Earth's largest "superbolts," NASA said.
The results about Jupiter were published in April 2020 in The Astrophysical Journal Supplement Series. | 0.863982 | 3.628076 |
New measurements of the rate of expansion of the universe, led by astronomers at the University of California, Davis, add to a growing mystery: Estimates of a fundamental constant made with different methods keep giving different results.
“There’s a lot of excitement, a lot of mystification and from my point of view it’s a lot of fun,” said Chris Fassnacht, professor of physics at UC Davis and a member of the international SHARP/H0LICOW collaboration, which made the measurement using the W.M. Keck telescopes in Hawaii.
A paper about the work is published by the Monthly Notices of the Royal Astronomical Society.
The Hubble constant describes the expansion of the universe, expressed in kilometers per second per megaparsec. It allows astronomers to figure out the size and age of the universe and the distances between objects.
Graduate student Geoff Chen, Fassnacht and colleagues looked at light from extremely distant galaxies that is distorted and split into multiple images by the lensing effect of galaxies (and their associated dark matter) between the source and Earth. By measuring the time delay for light to make its way by different routes through the foreground lens, the team could estimate the Hubble constant.
Using adaptive optics technology on the W.M. Keck telescopes in Hawaii, they arrived at an estimate of 76.8 kilometers per second per megaparsec. As a parsec is a bit over 30 trillion kilometers and a megaparsec is a million parsecs, that is an excruciatingly precise measurement. In 2017, the H0LICOW team published an estimate of 71.9, using the same method and data from the Hubble Space Telescope.
Hints of new physics
The new SHARP/H0LICOW estimates are comparable to that by a team led by Adam Reiss of Johns Hopkins University, 74.03, using measurements of a set of variable stars called the Cepheids. But it’s quite a lot different from estimates of the Hubble constant from an entirely different technique based on the cosmic microwave background. That method, based on the afterglow of the Big Bang, gives a Hubble constant of 67.4, assuming the standard cosmological model of the universe is correct.
An estimate by Wendy Freedman and colleagues at the University of Chicago comes close to bridging the gap, with a Hubble constant of 69.8 based on the luminosity of distant red giant stars and supernovae.
A difference of 5 or 6 kilometers per second over a distance of over 30 million trillion kilometers might not seem like a lot, but it’s posing a challenge to astronomers. It might provide a hint to a possible new physics beyond the current understanding of our universe.
On the other hand, the discrepancy could be due to some unknown bias in the methods. Some scientists had expected that the differences would disappear as estimates got better, but the difference between the Hubble constant measured from distant objects and that derived from the cosmic microwave background seems to be getting more and more robust.
“More and more scientists believe there’s a real tension here,” Chen said. “If we try to come up with a theory, it has to explain everything at once.”
Additional authors on the paper are: Sherry Suyu, Inh Jee and Simona Vegetti, Max Planck Institute for Astrophysics, Garching, Germany; Cristian Rusu, National Astronomical Observatory of Japan, Tokyo; James Chan, Vivien Bonvin, Martin Millon and Frederic Courbin, Ecole Polytechnique Federale de Lausanne, Switzerland; Kenneth Wong and Alessandro Sonnenfeld, Kavli Institute for the Physics and Mathematics of the Universe, Tokyo; Matthew Auger, University of Cambridge, U.K.; Stefan Hilbert, Exzellenzcluster Universe, Garching, Germany; Simon Birrer, Xuheng Ding, Anowar Shajib and Tommaso Treu, UCLA; Leon Koopmans and John McKean, University of Groningen, the Netherlands; David Lagattuta, Centre de Recherche Astrophysique de Lyon, France; Aleksi Holkala, Tuusula, Finland; and Dominique Sluse, Leiden University, the Netherlands.
The work was funded by the National Science Foundation. | 0.835968 | 4.0601 |
Mars has big dust storms, some times so big that they envelop the entire planet.
We know this because NASA has a number of satellites orbiting the Red Planet, producing vast amounts of new data, some of it giving intriguing hints about where all the water went.
Last year Mars was again enveloped by dust storms, the same events that ended the 15 years of exploration by the Mars Opportunity robotic rover.
Opportunity landed in 2004 and far exceeded its planned three-month life, its activities ending only when it was enveloped by the dust storm in June 2018.
Now two papers have been published, shedding new light on a phenomenon observed within the storm – dust towers, or concentrated clouds of dust that warm in sunlight and rise high into the air.
The NASA Jet Propulsion Laboratory (JPL), which conducts the planetary exploration program, said scientists think that dust-trapped water vapour may be riding these dust towers like an elevator to space.
The dust towers are massive, churning clouds that are denser and climb much higher than the normal background dust in the thin Martian atmosphere.
While they also occur under normal conditions, the towers appear to form in greater numbers during global storms. These reach as high as 80 kilometres and can be as big as a US state.
Recent findings on dust towers come courtesy of the NASA Mars Reconnaissance Orbiter (MRO) with the research led by JPL. The satellite’s heat-sensing Mars Climate Sounder instrument, designed specifically for measuring dust levels, can peer through the haze.
Its data, coupled with images from a camera aboard the orbiter called the Mars Context Imager (MARCI), enabled scientists to detect numerous dust towers.
"Normally the dust would fall down in a day or so," said lead author, Nicholas Heavens of Hampton University.
“But during a global storm, dust towers are renewed continuously for weeks."
In some cases, multiple towers were seen for almost a month.
That rate of dust activity surprised the scientists.
Especially intriguing was the possibility that dust towers acted as space elevators for other material, transporting them through the atmosphere.
When airborne dust heats up, it creates updrafts that carry gases along with it, including the small quantity of water vapor sometimes seen as wispy clouds on Mars.
A previous paper led by Heavens showed that during a 2007 global dust storm on Mars, water molecules were lofted into the upper atmosphere.
There, solar radiation could break them down into particles that then escaped into space.
NASA thinks that might explain how Mars lost its lakes and rivers over billions of years, becoming the freezing desert it is today.
Scientists can't say for sure what causes global dust storms as they have studied fewer than a dozen.
"Global dust storms are really unusual. we really don't have anything like this on the Earth, where the entire planet's weather changes for several months,” said Mars Climate Sounder scientist David Kass of JPL.
Receive the latest developments and updates on Australia’s space industry direct to your inbox. Subscribe today to Space Connect here. | 0.827051 | 3.963979 |
Moon ♑ Capricorn
Moon phase on 3 July 2012 Tuesday is Full Moon, 14 days old Moon is in Capricorn.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.
Moon is passing about ∠8° of ♑ Capricorn tropical zodiac sector.
Lunar disc appears visually 2.8% wider than solar disc. Moon and Sun apparent angular diameters are ∠1942" and ∠1887".
The Full Moon this days is the Buck of July 2012.
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 154 of Meeus index or 1107 from Brown series.
Length of current 154 lunation is 29 days, 13 hours and 22 minutes. It is 1 hour and 52 minutes longer than next lunation 155 length.
Length of current synodic month is 38 minutes longer than the mean length of synodic month, but it is still 6 hours and 25 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠217.1°. At the beginning of next synodic month true anomaly will be ∠248.7°. 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°).
1 day after point of perigee on 1 July 2012 at 18:01 in ♐ Sagittarius. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 10 days, until it get to the point of next apogee on 13 July 2012 at 16:47 in ♉ Taurus.
Moon is 369 137 km (229 371 mi) away from Earth on this date. Moon moves farther next 10 days until apogee, when Earth-Moon distance will reach 404 783 km (251 520 mi).
2 days after its ascending node on 1 July 2012 at 05:45 in ♐ Sagittarius, the Moon is following the northern part of its orbit for the next 11 days, until it will cross the ecliptic from North to South in descending node on 14 July 2012 at 20:55 in ♉ Taurus.
2 days after beginning of current draconic month in ♐ Sagittarius, the Moon is moving from the beginning to the first part of it.
1 day after previous South standstill on 2 July 2012 at 03:33 in ♐ Sagittarius, when Moon has reached southern declination of ∠-21.701°. Next 12 days the lunar orbit moves northward to face North declination of ∠21.665° in the next northern standstill on 16 July 2012 at 01:18 in ♊ Gemini.
The Moon is in Full Moon geocentric opposition with the Sun on this date and this alignment forms Sun-Earth-Moon syzygy. | 0.860247 | 3.041214 |
We analyzed data from the first year of a survey for Near-Earth Objects (NEOs) that we are carrying out with the Dark Energy Camera (DECam) on the 4 m Blanco telescope at the Cerro Tololo Inter-American Observatory. We implanted synthetic NEOs into the data stream to derive our nightly detection efficiency as a function of magnitude and rate of motion. Using these measured efficiencies and the solar system absolute magnitudes derived by the Minor Planet Center for the 1377 measurements of 235 unique NEOs detected, we directly derive, for the first time from a single observational data set, the NEO size distribution from 1 km down to 10 m. We find that there are 106.6 NEOs larger than 10 m. This result implies a factor of 10 fewer small NEOs than some previous results, though our derived size distribution is in good agreement with several other estimates.
- minor planets, asteroids: general
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science | 0.840467 | 3.242183 |
1) Position in the solar system: 8th planet from the sun
2) Closest distance to the sun: Perihelion: 4.444×10^9 km
3) Furthest distance from the sun: Aphelion: 4.546×10^9 km
4) Minimum distance to Earth: 4.292×10^9 km
5) Neptunian day: 16.11 hr
6) Neptunian year: 164.8 Earth years
7) Axis tilt: 28.32°
8) Orbital inclination to ecliptic: 1.77°
9) Orbital eccentricity: 0.0086
10) Diameter (equatorial): 49,528 km
11) Mass: 1.024×10^26 kg, approx. 17.1 times that of Earth
12) Gravity: 1.14 (Earth = 1)
13) Escape velocity: 23.5 km/s
14) Temperature: -201°C at 1.0 bar pressure
15) Mean surface pressure: >1000 bars
16) Atmospheric composition: 80% hydrogen, 19% helium, 1.5% methane (numbers do not add up to 100% due to uncertainty) with trace amounts of hydrogen deuteride ("heavy" hydrogen) and ethane, and aerosolized crystals of ammonia ice, water ice, ammonia hydrosulfide, and methane ice
17) Number of moons: 13
18) Ringed system? Yes
19) Magnetic Field? Yes
Amazing & Interesting Facts About Neptune!
1) Discovery as a triumph of scientific prediction: Neptune was predicted to exist by John Couch Adams and Urbain Leverrier, based on features observed in the orbit of the planet Uranus. The hypothesis explained these features as gravitational effects of an eighth planet. Johann Gottfried Galle discovered Neptune when he observed it in the predicted location on September 23, 1846.
2) Nearly discovered by Galileo: Galileo observed Neptune in the 17th century through his telescope, but by coincidence he observed it just as it was beginning its retrograde motion. For that reason, he did not recognize its planetary movement and thought it was a fixed star.
3) Extreme weather: Unlike its relatively calm neighbor, Uranus, Neptune has extreme weather. A storm called the Great Dark Spot measures 13,000 km long, about the diameter of Earth. Windspeeds on Neptune reach the near-supersonic speed of nearly 600 km/s, despite the fact that the planet receives 1/900 as much energy from the Sun as Earth.
Sample Neptune Fact Sheet (NASA): https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html
JPL Photojournal: https://photojournal.jpl.nasa.gov/catalog/PIA02245
Science Magazine: https://www.sciencemag.org/cgi/content/abstract/251/4996/929
Neptune true color image: https://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=2424
Neptune and Triton image: https://www.nasa.gov/worldbook/neptune_worldbook.html
Clouds of Neptune image: https://voyager.jpl.nasa.gov/science/neptune_magnetic.html.
Neptune. (Supplied by NASA) | 0.938148 | 3.399928 |
A newly discovered cluster of galaxies, more than 5 billion light years from Earth…is among the most massive clusters of galaxies in the universe, and produces X-rays at a rate faster than any other known cluster 다운로드.
It also creates new stars at an “unmatched” pace of more than 700 per year, said Michael McDonald. “This extreme rate of star formation was unexpected,” he said during a NASA news conference Wednesday, noting that the Milky Way forms just one or two stars a year 컴퓨터 바탕화면 다운로드.
In addition to being massive, unique, and the biggest star-nursery in the universe, this area, called Phoenix, also helps theorists with something, the galactic cooling problem 다운로드.
For years scientists have been coming up with explanations for how stars are formed 다운로드. The earliest being a mass of molecules would collapse in on themselves as fusion begins. The mass would then accumulate until its gravity becomes strong enough to spin, turn into a sphere, and pull on everything around it, collecting planets, asteroids, and other debris into its solar system 2019년 달력 한글 다운로드.
But, this doesn’t take into account thermodynamics, specifically why doesn’t the star expand as it heats up. Indeed, several half-stars were observed in the universe stuck in this state of expansion unable to contract into the ultra-compact ball of a star 다운로드.
That’s where a new theory comes in, the galactic “cooling flow”.
**There appears to be no name for the theory, all references are to a general theory theory of star formation 자백 14 다운로드.
This says the creation of stars is a lot like an explosion, with an initial burst of heat which then dissipates bringing cool air back into the explosion zone 앵무새 다운로드. In this case, thermonuclear fusion ignites much of the galaxy and begins sucking into the center lots of mass, including the surrounding galaxies.
As the (star) forms, this plasma initially heats up due to the gravitational energy released from the infall of smaller galaxies 여신의 키스 다운로드.
As the gas cools, it should condense and sink inward, a process known as a “cooling flow.” In the cluster’s center, this cooling flow can lead to very dense cores of gas, termed “cool cores,” which should fuel bursts of star formation in all clusters that go through this process. Most of these predictions had been confirmed with observations – the X-ray glow, the lower temperatures at the cluster centers – but starbursts accompanying this cooling remain rare. – TG Daily
A step forward in our knowledge of star formation, but something tells me we are not there yet. | 0.823031 | 3.703287 |
eso1008 — Photo Release
Light, Wind and Fire
Beautiful Image of a Cosmic Sculpture
24 February 2010
Today ESO has released a dramatic new image of NGC 346, the brightest star-forming region in our neighbouring galaxy, the Small Magellanic Cloud, 210 000 light-years away towards the constellation of Tucana (the Toucan). The light, wind and heat given off by massive stars have dispersed the glowing gas within and around this star cluster, forming a surrounding wispy nebular structure that looks like a cobweb. NGC 346, like other beautiful astronomical scenes, is a work in progress, and changes as the aeons pass. As yet more stars form from loose matter in the area, they will ignite, scattering leftover dust and gas, carving out great ripples and altering the face of this lustrous object.
NGC 346 spans approximately 200 light-years, a region of space about fifty times the distance between the Sun and its nearest stellar neighbours. Astronomers classify NGC 346 as an open cluster of stars, indicating that this stellar brood all originated from the same collapsed cloud of matter. The associated nebula containing this clutch of bright stars is known as an emission nebula, meaning that gas within it has been heated up by stars until the gas emits its own light, just like the neon gas used in electric store signs.
Many stars in NGC 346 are relatively young in cosmic terms with their births dating back only a few million years or so (eso0834). Powerful winds thrown off by a massive star set off this recent round of star birth by compressing large amounts of matter, the first critical step towards igniting new stars. This cloud of material then collapses under its own gravity, until some regions become dense and hot enough to roar forth as a brilliantly shining, nuclear fusion-powered furnace — a star, illuminating the residual debris of gas and dust. In sufficiently congested regions like NGC 346, with high levels of recent star birth, the result is a glorious, glowing vista for our telescopes to capture.
NGC 346 is in the Small Magellanic Cloud, a dwarf galaxy some 210 000 light-years away from Earth and in close proximity to our home, the much larger Milky Way Galaxy. Like its sister the Large Magellanic Cloud, the Small Magellanic Cloud is visible with the unaided eye from the southern hemisphere and has served as an extragalactic laboratory for astronomers studying the dynamics of star formation.
This particular image was obtained using the Wide Field Imager (WFI) instrument at the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile. Images like this help astronomers chronicle star birth and evolution, while offering glimpses of how stellar development influences the appearance of the cosmic environment over time.
ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory, and VISTA the largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
Tel: +49 89 3200 6222 | 0.90349 | 3.722021 |
NASA’s InSight lander will look for quakes on Mars (Image: JPL/NASA)
Quakes deep inside the moon have been unearthed in seismic data recorded during the Apollo 16 mission. The algorithm behind the find could help NASA’s next Mars mission study similar quakes on the Red Planet.
We have known that the moon shakes since shortly after Neil Armstrong’s first step. Seismometers left by the Apollo missions picked up echoes from meteor strikes, deep quakes linked to the moon’s orbit around Earth and powerful shallow quakes of unclear origin – all of them different-looking and of different origin to the seismic activity we see on Earth.
Since then, a catalogue of the moon’s tremors has been painstakingly assembled both by hand and by computer, with about 13,000 events identified. But software trained by a human eye and then loosely supervised could do an even better job, says Brigitte Knapmeyer-Endrun of the Max Planck Institute for Solar System Research in Gottingen, Germany.
Knapmeyer-Endrun and her team developed an algorithm that, given just one example of a type of moonquake, can identify quakes with the same rough pattern. Similar programs were first developed for speech recognition algorithms.
The team ran the program on data from the seismometer left on the moon by the Apollo 16 mission in 1972, which stopped communicating with Earth in 1977. The algorithm found 210 quakes that had escaped earlier notice in only a small set of the data.
Such a fast, versatile approach to picking out unfamiliar quakes may be useful for NASA’s InSight lander, which aims to put a seismometer on Mars. InSight doesn’t have much bandwidth to send its signals back, so software like this could help determine which Marsquakes warrant detailed study. “We need to decide quickly if there’s something interesting in a timeframe, and if we want to have a closer look,” Knapmeyer-Endrun says.
Journal reference: Journal of Geophysical Research: Planets, DOI: 10.1002/2015JE004862
More on these topics: | 0.868288 | 3.397061 |
Brown dwarf winds blow hard.
For the first time ever, astronomers have measured wind speed on a brown dwarf, or "failed star," an object heftier than a planet but not massive enough to host the fusion reactions that power stars.
That speed, a new study reports, is around 1,450 mph (2,330 km/h) — more than four times faster than any gust we experience here on Earth. (The terrestrial record is 318 mph, or 512 km/h, set in 1999 by a tornado in Oklahoma.)
The research team studied a brown dwarf called 2MASS J10475385+2124234, which is about 40 times more massive than Jupiter and lies 34 light-years from Earth. The scientists employed a novel strategy that was inspired by previous observations of Jupiter.
"We noted that the rotation period of Jupiter as determined by radio observations is different from the rotation period determined by observations at visible and infrared wavelengths," study lead author Katelyn Allers, an associate professor of physics and astronomy at Bucknell University in Lewisburg, Pennsylvania, said in a statement.
That's because the radio emissions are coming from electrons interacting with Jupiter's magnetic field, which is rooted deep in the planet's interior, she explained. The visible and infrared (IR) data, on the other hand, reveal what's happening in the gas giant's cloud tops.
The difference between the two rotation rates therefore provides a measurement of wind speed in Jupiter's upper atmosphere. And it should be possible to gather similar data for brown dwarfs, which are like scaled-up gas giants, the team reasoned.
"When we realized this, we were surprised that no one else had already done it," Allers said.
So Allers and her colleagues did it.
They gathered radio data on 2MASS J10475385+2124234 in 2018 using the Very Large Array telescope network in New Mexico. And they got the IR observations in 2017 and 2018 with NASA's Spitzer Space Telescope, which tracked the movement of a long-lived feature through the brown dwarf's upper atmosphere. (The researchers also studied a second brown dwarf, called WISE J112254.73+ 255021.5, but were unable to get the requisite IR information for that one.)
The data revealed that prevailing winds on 2MASS J10475385+2124234 flow east to west at roughly 1,450 mph, plus or minus 690 mph (1,110 km/h). That's considerably faster than the average winds in Jupiter's upper atmosphere, which zoom along at about 250 mph (400 km/h), the researchers said.
Such a disparity is to be expected. After all, the brown dwarf is significantly warmer, and thus more energetic, than Jupiter. 2MASS J10475385+2124234 has an estimated temperature of 1,124 degrees Fahrenheit (607 degrees Celsius), whereas Jupiter's cloud tops are a frosty minus 230 F (minus 145 C).
The new results should help astronomers learn more about the complex dynamics of brown dwarf atmospheres, which are poorly understood. After all, researchers now have an actual wind-speed number, rather than a mere estimate, to plug into their models.
"If you know how fast the wind speed is, you actually can get a pretty good handle on whether the atmosphere is dominated by banding or by circular storms," study co-author Johanna Vos, a postgraduate researcher at the American Museum of Natural History in New York, told Space.com.
And applications of the new study, which was published online today (April 9) in the journal Science, go beyond brown dwarf research, both Allers and Vos said.
"The next step is to do this for an exoplanet orbiting a star," Vos said. "It's kind of opened up new possibilities, and I find that really exciting."
But not every exoplanet is open to this line of inquiry, she added; astronomers will have to content themselves with relatively cool gas giants that can be directly imaged, at least for the foreseeable future. (The technique won't work with "hot Jupiters," gas giants that orbit very close to their stars, Vos said. These planets are tidally locked, always showing their host stars the same face, making it difficult if not impossible to track large-scale atmospheric movement.)
And such work cannot be done with Spitzer anymore, because NASA recently retired the workhorse space telescope. It will be tough for NASA's Hubble Space Telescope to pick up the slack, Vos said; Hubble orbits Earth and therefore doesn't make the required lengthy, uninterrupted observations of distant targets. (Spitzer circled the sun in an Earth-trailing orbit.)
"I think JWST will be our next opportunity to do this," Vos said, referring to NASA's $9.7 billion James Webb Space Telescope, which is scheduled to launch next year.
Many other researchers will be champing at the bit to use the powerful, flexible JWST once it comes online, so it may be tough to secure the requisite 20 or so consecutive hours on the scope, Vos said.
"We're still going to ask for it," she said. "We'll have to see."
- Gallery: The infrared universe seen by NASA's Spitzer Space Telescope
- Brown dwarfs: the coolest stars or the hottest planets?
- Extraterrestrial hurricanes: other planets have huge storms, too
Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook. | 0.848318 | 3.962226 |
If two black holes tango in space but astronomers cannot see them, can we still admire their flashy dance moves?
Because black holes have such a strong gravitational pull that not even light can escape, they can't be observed directly and are therefore difficult to study. But one pair of black holes has enamored astronomers with a complicated celestial dance that periodically produces extremely bright flashes of light — outbursts that are brighter than a trillion stars and even the entire Milky Way galaxy.
By studying the timing of these bright flashes of light, researchers have attempted to map out the complex choreography of the black holes' movements and predict exactly when the system will flare up again. After more than 120 years of observations and decades of building computer models, astronomers have finally figured out what these black holes are up to, thanks to data from NASA's now-retired Spitzer Space Telescope.
The two "dancing" black holes are located 3.5 billion light-years from Earth at the center of a galaxy called OJ 287. The larger of the two is one of the biggest black holes ever found, weighing in at more than 18 billion times the mass of the sun. Orbiting around this big black hole is a much smaller black hole that's about 150 million times the mass of the sun. Twice every 12 years, the smaller black hole passes through the larger one's accretion disk, or the flat band of dust and gas falling into the black hole, creating brilliant flares of light.
Because the small black hole's orbit is irregular — its position shifts with each 12-year loop around its partner — these flashes don't occur on a regular schedule. Sometimes they might occur just one year apart, while other times up to a decade passes between flares. The seemingly random timing of the flares has made it difficult for astronomers to figure out exactly what kind of "dance" these black holes are doing.
One computer simulation in 2010 was able to predict the flares within one to three weeks. In 2018, another group of researchers led by Lankeswar Dey, a graduate student at the Tata Institute of Fundamental Research in Mumbai, published a new model that they claimed could predict the flares' occurrence within four hours. In a new study, published Tuesday (April 28) in The Astrophysical Journal Letters, Dey's group reports that Spitzer's observations of a flare on July 31, 2019, confirm that their model is correct.
The Spitzer Space Telescope, which NASA decommissioned in January, just happened to be in the right place at the right time to observe the flare on that day, when no other telescopes on Earth or in space were able to see it. At the time, OJ 287 was on the opposite side of the sun from Earth's perspective.
Spitzer was 158 million miles (254 million kilometers) away from Earth at the time, and from its vantage point the telescope had a clear view of OJ 287 for a little over a month, from July 31 to early September, NASA officials said in a statement.
"When I first checked the visibility of OJ 287, I was shocked to find that it became visible to Spitzer right on the day when the next flare was predicted to occur," Seppo Laine, a scientist at Caltech/IPAC in Pasadena, California, who oversaw Spitzer's observations of the system, said in the statement. "It was extremely fortunate that we would be able to capture the peak of this flare with Spitzer, because no other human-made instruments were capable of achieving this feat at that specific point in time."
To come up with this accurate prediction, the researchers didn't just look at the orbital mechanics of the system. They also had to account for gravitational waves, or ripples in space-time created when massive objects move through space, warping their surroundings. Astronomers expect the black hole system in OJ 287 to generate gravitational waves that are strong enough to alter the smaller black hole's orbit, according to the statement.
By incorporating gravitational waves into their calculations, the researchers were able to predict a 1.5-day time frame in which the system will produce a flare. But they narrowed that down even further, to just four hours, by taking into account the "no-hair theorem" of black holes — an idea that Stephen Hawking famously doubted. This theorem posits that black hole surfaces are featureless and symmetric, rather than bumpy and irregular. (Black holes don't literally have a "surface," but rather an invisible boundary known as the event horizon, where not even light can escape the black hole's gravitational pull.)
If the large black hole at the center of OJ 287 were bumpy, with its mass unevenly distributed, its gravitational pull on the smaller black hole would be inconsistent, which would affect the smaller black hole's orbit and the timing of the flares. But the smaller object's symmetrical, spirograph-shaped orbit supports the no-hair theorem, the new study claims.
"It is important to black hole scientists that we prove or disprove the no-hair theorem," Mauri Valtonen, an astrophysicist at University of Turku in Finland and a coauthor of the study, said in the statement. "Without it, we cannot trust that black holes as envisaged by Hawking and others exist at all."
- Clocking the extreme spin of a monster black hole
- No Escape: Dive into a black hole (infographic)
- Scientists detect rare crash of two mismatched black holes for the first time | 0.886852 | 3.982931 |
There have been five mass extinction events in Earth's history. In the worst one, 250 million years ago, 96 percent of marine species and 70 percent of land species died off. It took millions of years to recover.
Nowadays, many scientists are predicting that we're on track for a sixth mass extinction. The world's species already seem to be vanishing at an unnaturally rapid rate. And humans are altering the Earth's landscape in far-reaching ways: We've hunted animals like the great auk to extinction. We've cleared away broad swaths of rain forest. We've transported species from their natural habitats to new continents. We've pumped billions of tons of carbon-dioxide into the atmosphere and oceans, transforming the climate.
Those changes could push many species to the brink. A 2007 report from the Intergovernmental Panel on Climate Change suggested that20 to 30 percent of plant and animal species faced an increased risk of extinction this century if the planet keeps warming rapidly (though scientists are still debating these estimates, with some lower, some far higher).
So what happens if the extinction rate does speed up? That's one of the questions that New Yorker science writer Elizabeth Kolbert explores in her new book, The Sixth Extinction, an in-depth look at the science of extinction and the ways we're altering life on the planet. We spoke by phone this week about the topic.
Brad Plumer: Let's start by walking through the history of science here. Back in the 18th century, no one even knew that there were any extinct species. How did we get from there all the way to realizing that there had been five of these mass extinction events in Earth's history?
Elizabeth Kolbert: There is an interesting history there. Up until the early 1800s, the concept of extinction didn’t really exist. Even early in the 19th century, you had Thomas Jefferson hoping that when he sent Lewis and Clark to the Northwest, that they would find mastodons roaming around. Mastodon bones had been unearthed — there was a very famous one unearthed in New York and displayed in Philadelphia — and people thought they must still exist somewhere.
But right around that time, a French naturalist named Georges Cuvier came to the realization that look, if these animals were out there, we would have seen them by now. They are not there. And that made sense of a lot of things. There were these bones that were very, very hard to explain. And more and more of them as Europeans colonized the New World, they were getting these bones shipped to them. It made sense of these weird nautical creatures that had been found that no one ever found.
S0 extinction actually predated the concept of evolution by about half a century — people knew that things went extinct, even though they didn't really understand how species came into being. But there was still some debate. Cuvier thought that when extinctions happened, it must be because the Earth changed quickly and catastrophically. Why else would an animal that was perfectly suited to life on this planet go extinct? His theory became known as "catastrophism." And Charles Lyell and Charles Darwin came along and said, that's ridiculous, the Earth changes slowly, we've never seen a catastrophe, that's because they don't exist.
That paradigm persisted until the 1980s and 1990s. That was when Walter Alvarez and his father Luis Alvarez came up with the theory that an asteroid impact had done in the dinosaurs. And that idea was actually resisted for the same reasons — the dominant view was that the Earth does not change quickly. But then it was proven.
And so now the prevailing view of change on planet Earth, as one paleontologist put it, is that the history of life consists of long periods of boredom interrupted occasionally by panic. It usually changes slowly, but sometimes it changes fast, and when it does, it's very hard for organisms to keep up.
BP: Nowadays, scientists are aware of five mass extinction events in the past, starting with the End-Ordovician Extinction 450 million years ago and up to the End-Cretaceous Extinction that killed off the dinosaurs 66 million years ago (see chart). Is there a lot we still don't know about what caused these events?
The worst mass extinction of all time came about 250 million years ago [the Permian-Triassic extinction event]. There's a pretty good consensus there that this was caused by a huge volcanic event that went on for a long time and released a lot of carbon-dioxide into the atmosphere. That is pretty ominous considering that we are releasing a lot of CO2 into the atmosphere and people increasingly are drawing parallels between the two events.
The very first extinction event [the end-Ordovician], seems to have been caused by some kind of sudden cold snap, but no one's exactly sure how that happened. But then, with the other two, the causes of those are pretty murky and people have tried to come up with a unified theory for these extinctions, but that hasn't worked at all. The causes seem to be pretty disparate.
BP: Now, at some point scientists realized that present-day extinction rates seem to be elevated — that species may now disappearing faster than the normal "background" rate. (Though precise estimates are tricky because measuring that background rate turns out to be very difficult.) How did they realize this?
EK: I think a point that's important to make is that, normally, you shouldn't be able to see anything go extinct in the course of a human lifetime. The normal background rate of extinction is very slow, and speciation and extinction should more or less equal out. But that's clearly not what is happening right now. Any naturalist out in the field has watched something go extinct or come perilously close. Even children can name things that have gone extinct.
So as soon as this concept of background vs. mass extinction came into being in the 1980s, people realized that what we're seeing today is not just background extinction. Now, whether you make the jump to say that a major mass extinction is going on or just an elevated extinction rate, that's up for debate. But if you are looking at this in a rigorous way, you can see that something unusual is going on.
BP: One thing your book explores is that no single factor will drive current and future extinctions. There's hunting and poaching. There's deforestation. There are invasive species. There's climate change and the acidification of the oceans. Which of these stands out as most significant?
EK: To me, what really stood out... And I always say, look, I'm not a scientist, I'm relying on what scientists tell me. And I think many scientists would say that what we're doing to the chemistry of the oceans could end up being the most significant. One-third of the carbon-dioxide that we pump into the air ends up in the oceans almost right away, and when CO2 dissolves in water, it forms an acid, that's just an unfortunate fact.
The chemistry of the oceans tends to be very stable, and to overwhelm those forces is really hard. But we are managing to do it. When people try to reconstruct the history of the ocean, the best estimate is that what we're doing to the oceans or have the potential to do is a magnitude of change that hasn't been seen in 300 million years. And changes of ocean chemistry are associated with some of the worst extinction crises in history.
BP: Are there lessons we can learn from past extinctions that provide clues for what the current changes hold?
EK: A lot of people are trying to tease out what survived previous extinctions and ask what are the characteristics of those that survived. It's called the selectivity of extinction events. Why did some groups survive and others didn't? It turns out to be, 65 million years after the fact, very, very difficult.
But speaking very broadly, the species that tend to survive mass extinction events often tend to be very widely distributed, or groups that have a lot of species. I'm not sure whom that's going to help today, but that seems to be the pattern.
BP: In your book you talk about this quasi-experiment in Brazil dating back to the 1970s, where ranchers had down swaths of rain forest at random and scientists could study the effects on species. What did we learn about deforestation and extinction from that?
EK: Right, the Biological Dynamics of Forest Fragments Project. It's in the Amazon rain forest north of the city of Manaus. What happened there was that this area was already being converted into ranches, so in collaboration with some American scientists, they deforested it in an interesting way. They left these square patches surrounded by ranch. You can see it from the air, it's quite striking. And this group of scientists surveyed the habitat in this forest before everything was cut down and then monitored it for 35 years.
And what you find are variations on this theme of loss. First most of the primate species don't survive in these smaller patches or even in the bigger patches of forest. Then you lose a lot of your bird species. In some cases species leave, and in some cases, when you maroon them in small patches of habitat, their populations shrink, and very small populations are just more vulnerable to chance.
So when people talk about the dangers of habitat fragmentation, on the one hand, a big animal that needs a large range can't survive in a small patch. But it's also smaller animals that don't need that much space become vulnerable to the dynamics of small populations.
BP: Did that Brazil project yield any lessons for protecting rain forest habitats?
EK: Don't deforest! For one. But also in the 1980s there was this battle about protecting forests, and whether it was better to do it in lots of little patches or in one big patch. And this project has resolved that. You need big areas if you want to preserve biodiversity, for the reasons I just mentioned.
BP: You discuss global warming in your book. And the big concern here seems to be that a lot of species are adapted to particular climate ranges, and if those heat up, some species may not be able to move or relocate fast enough to more suitable climates. How much do we really know about these dynamics?
EK: What people are finding, what the scientists that I was out in the Peruvian cloud forest with are finding, is that things move at very different rates. People have calculated how fast species would have to move to keep up with rising temperatures, whether it's moving up a mountain or moving to higher latitudes.
And some organisms can keep up with that fantastically high pace — for example, in Peru, there was this one genus of tree called Schefflera, which is sometimes used as a house plant, and that genus is moving really fast up the mountain. But some of the other plants weren't moving at all, and others were moving but not nearly fast enough.
So the lesson is that all those pretty complicated relationships, which in the tropics have been been pretty stable for a long time, are going to break up. And we just don't know what the fall-out from that is going to be.
BP: So you end up with pretty wide estimates for how many species could go extinct if the planet heats up this much. Some studies suggest that 20 percent to 30 percent of species are at risk of extinction if the planet warms 2°C. Other scientists think those estimates are flawed.
EK: There's still a lot we don't know here. You often hear that what we're doing is a planetary experiment, but we only have one planet, and we can only run this experiment once. So some of these modeling efforts get pretty complicated. Just because a species lives in a certain climate under a certain set of conditions, could it live under different conditions? Or is this just where it's maximally competitive? What happens if some of your competitors are disadvantaged? We just don't know. Life turns out to be incredibly complicated.
BP: That brings me to another question. Most of the people in your book who study these trends tend to think they're horrible news. Did you come across researchers who had a more optimistic view?
EK: I guess one point to make: Even in moments of extremes, certain organisms do thrive. They're sometimes called "disaster taxa," and they do very well. After the End Permian extinction, which was the worst mass extinction of all time, there was an animal calledLystrosaurus, was a pig-sized animal that just did phenomenally well. It was the biggest animal on the planet, you find fossils everywhere. And the question of why did it do so well? We just don't know.
But some things will thrive. Some things will thrive in an acidified ocean because all of their competitors will drop out. So some things will do well, and undoubtedly there will be surprises. But I have not met anyone who hasn't said, we're going to be vastly simplifying the web of life. A lot of things are going to drop out. It's hard to make predictions of what they are.
BP: There's another angle in your book that tends to get less attention. The spread of people across continents has transported all sorts of species to new habitats — and sometimes that's had catastrophic results, like when thebrown tree snake was introduced into Guam and wiped out the native birds. Is this sort of exchange speeding up, or are there efforts to slow it down?
EK: There are certain moments of time where you see a huge exchange of species. After Columbus arrived in the New World,there was this huge exchange. And as global travel becomes very rapid, that speeds up exchanges. Organisms that couldn't survive on the Mayflower could survive in a modern supertanker or plane and get transported from one continent to another. So we've ratcheted things up a notch.
So we don't do as much purposeful moving of species as we used to — where we've decided we'd like to have this bird in a new place. We've done a lot to prevent that. You're not supposed to just take a bird from South America and release it in Australia. But the unconscious transport of species, I think there's no doubt that is increasing very dramatically as the sheer amount of cargo increases.
And it can still have devastating effects. Look at the Asian carp,working their way toward the Great Lakes. There's the Asian longhorn beetle, a pretty recent invader causing tremendous damage to forests in this country. There's the emerald ash borer, quite a recent one, which has led to all these signs in the Northeast telling people not to move firewood, to avoid moving these invaders around.
There are zebra mussels, which recently moved into Massachusetts, where they weren't, taking over lakes there. The disease that’s killing off bats in the Northeast and in the D.C. area, that’s an invasive pathogen that was brought in, it’s a fungus. We can just name one thing after another. And I’m sure if we have this conversation a year from now there will be new ones that we know about.
BP: Now what about attempts to save species from extinction? What are some of the more interesting efforts you encountered?
EK: A lot of them involve zoos or conservation organizations. So there are these really fascinating and pretty ugly animals called hellbenders, they’re these big salamanders that could feature in a horror movie. They are very endangered, and what people are trying to do is raise them to a certain size at the Bronx Zoo, and then repopulate streams in upstate New York.
Also at the Bronx Zoo there's this amazing project with this endangered bird from an island in the Pacific [the maleo]. It lays these enormous eggs that have to be incubated in volcanic soil. They bury the egg and the egg is warmed by volcanic activity in the area, which is just amazing. So the zoo is trying to make an incubator that mimics these volcanic soils. Then they trick the birds, by taking away their eggs so that they lay another. And there are hundreds and hundreds of these efforts.
BP: Don't these sorts of efforts tend to favor "charismatic" animals over things like tiny organisms in the ocean that could affect entire food webs?
EK: Yes. We only see what we see. And we don't know where the link is that may turn out to be absolutely crucial, because we’re not participating in the food web at that level of specificity. The really scary thing is when scientists find organisms at the bottom of the food chain that can’t survive under conditions that we predict will occur in next century or so. That has happened. Then you can potentially get these big knock-on effects on the food chain. If you talk to marine scientists, that's exactly what they're worried about.
And you might be able to raise that pteropod in a tank, but it really doesn’t matter. Because we’re talking about things that exist on a massive scale. Too numerous to count. That's what keeps the food chain going.
BP: As a final question, what's the big thing you took away after reporting and writing this book?
EK: Here's the big thing I took away, and it’s a very sobering thought: Many of our best qualities as humans —our creativity, our cleverness, our cooperation, the fact that we can work in these huge societies, and pass knowledge on from generation to generation — those things can turn out to be damaging. It's not just that we go out and poach things, although that's a problem. We've very smart and inventive and we can change the planet by doing things that have no evil intent. For example, going on vacation and bringing a bat fungus from Europe to the United States completely unintentionally. So it's not always clear how you would separate out what we do just by being human from what we do that has all of these unfortunate side effects. | 0.827847 | 3.07835 |
One of the primary problems with sending astronauts to Mars is the length of time it takes to travel the 34 million miles of space that lies in between.
With the technology we have at present, this is estimated to take anywhere between 6 and 8 months — and that is with Mars at its closest. Having a crew floating around in zero gravity inside a spacecraft for so long means that they could be physically too weak to do anything when they get there—at least for the first few days, and that could be critical for the mission as a whole. Even though Mars gravity is only one-third of Earth, it still has the potential to be debilitating for our newly arrived astronauts.
So what to do?
One solution is to build spacecraft with a rotating torus, or similar, to provide our intrepid crew with some artificial gravity. If you have seen the movie The Martian, you might have noticed that this is the type of ship they used. By providing the astronauts with some gravity during the long journey to Mars, they would be fit and ready for action when they landed. However, there are a number of problems with this, not least the enormous cost, but also the engineering challenges involved in building something that complex and assembling up in Earth orbit. Just think how long it took to build the ISS.
The other solution, of course, is to get there faster.
So, one of the areas I looked into when I was doing the research for Colony Mars, was what work was being done on experimental rocket engines, particularly those that had the potential to be considerably faster than conventional engines.
The first one I considered was the Ion Thruster. These are currently being used to keep satellites in orbit as well as for some deep space probes. This technology is way more efficient than a chemical rocket, which has a fuel efficiency of around 35 %. Whereas the Ion engine is around 90% efficient. Theoretically, it can reach speeds of over 200,000mph, which is insane when you think about it. By comparison, the Space Shuttle could only manage a paltry 18,000mph.
So what’s the catch?
Well, it may have very high theoretical top speed, but it has very, very low thrust, around 0.5 newtons. To get an idea of what that number actually means, imagine holding say, a dozen coins in the palm of your hand. The weight of those few coins is approximately the same as the trust from this engine—not a lot.
So, to get anywhere you need to operate it over a very, very long period of time. The thrust might be tiny, but over a long period, it can build upon itself, accelerating faster and faster. The first spacecraft to use an Ion thruster was Deep Space 1, a NASA probe launched in 1998 and acted as a test bed for advanced technologies.
However, to be appropriately sci-fi I needed something a little more exotic, and I found it in the experimental EmDrive (aka, Radio Frequency Resonant Cavity Thruster), the brainchild of an English inventor, Roger Shawyer. It’s a bizarre contraption that defies the standard laws of physics. Mainly, it’s a microwave in a box, powered merely by electricity. How this could possibly provide forward thrust is beyond the realms of common sense physics. But it does seem to work, although the jury is still out on that.
Needless to say, it has been scoffed at by the physics establishment and vilified by rocket scientists and would have languished in blissful oblivion only for the interest shown by Chinese scientists. Once they started taking it seriously, then NASA Eagleworks soon followed. In 2014 NASA released some test results showing that a microwave, in an enclosed metal cone, can indeed provide forward motion, with potential trust values similar to that of Ion engines. The difference, of course, it that the EmDrive does not need a fuel tank, it just needs electricity. Theoretically, all your spacecraft would need are a few solar panels, and off you go.
But it’s not all good news. More recently, a German team concluded that the trust from their own tests could simply be from interference with the Earth’s electromagnetic field. If this proves to be true, then that would be the end for the EmDrive.
However, here’s where it starts to get interesting. You know that top secret space plane, the X-37B, that the US air-force lobs up into orbit every now and again? Well, rumor has it that it is being used to test an EmDrive. Even more interesting is that China has apparently been testing a device in orbit since 2016 and now plan to incorporate a version of it into their space station, Tiangong-2.
So, to conclude in true conspiracy theory fashion—something’s going on here. There’s a reason why these two powers are throwing resources at this device
Does it really work?
If any of these tests results turn out to be positive, then this would be an extraordinary breakthrough for space travel. Here is a basic engine, with no moving parts, not subjected to enormous forces, that works simply by electricity.
So are we on the cusp of a new space technology race? Only time will tell, but you can see why I chose this as the engine of choice to get Dr. Jann Malbec and her crew-mates to Mars in such a short period of time. That said, in The Belt series time has moved on and I started to think that maybe the VASMIR (Variable Specific Impulse Magnetoplasma Rocket) engine might be a real possibility by then—more on that later. | 0.805035 | 3.56667 |
Crescent ♓ Pisces
Moon phase on 12 January 2016 Tuesday is Waxing Crescent, 3 days young Moon is in Aquarius.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 2 days on 10 January 2016 at 01:30.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Moon is passing about ∠23° of ♒ Aquarius tropical zodiac sector.
Lunar disc appears visually 1% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1932" and ∠1951".
Next Full Moon is the Wolf Moon of January 2016 after 11 days on 24 January 2016 at 01:46.
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 3 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 198 of Meeus index or 1151 from Brown series.
Length of current 198 lunation is 29 days, 13 hours and 8 minutes. It is 1 hour and 52 minutes longer than next lunation 199 length.
Length of current synodic month is 24 minutes longer than the mean length of synodic month, but it is still 6 hours and 39 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠292.2°. At the beginning of next synodic month true anomaly will be ∠319.8°. 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°).
10 days after point of apogee on 2 January 2016 at 11:53 in ♎ Libra. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 2 days, until it get to the point of next perigee on 15 January 2016 at 02:10 in ♓ Pisces.
Moon is 371 035 km (230 550 mi) away from Earth on this date. Moon moves closer next 2 days until perigee, when Earth-Moon distance will reach 369 619 km (229 671 mi).
11 days after its ascending node on 31 December 2015 at 20:19 in ♍ Virgo, the Moon is following the northern part of its orbit for the next 2 days, until it will cross the ecliptic from North to South in descending node on 14 January 2016 at 15:48 in ♓ Pisces.
11 days after beginning of current draconic month in ♍ Virgo, the Moon is moving from the beginning to the first part of it.
3 days after previous South standstill on 8 January 2016 at 17:56 in ♐ Sagittarius, when Moon has reached southern declination of ∠-18.420°. Next 9 days the lunar orbit moves northward to face North declination of ∠18.375° in the next northern standstill on 21 January 2016 at 16:41 in ♊ Gemini.
After 11 days on 24 January 2016 at 01:46 in ♌ Leo, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.173328 |
- Define the concept of flux
- Describe electric flux
- Calculate electric flux for a given situation
The concept of flux describes how much of something goes through a given area. More formally, it is the dot product of a vector field (in this chapter, the electric field) with an area. You may conceptualize the flux of an electric field as a measure of the number of electric field lines passing through an area (Figure 6.3). The larger the area, the more field lines go through it and, hence, the greater the flux; similarly, the stronger the electric field is (represented by a greater density of lines), the greater the flux. On the other hand, if the area rotated so that the plane is aligned with the field lines, none will pass through and there will be no flux.
A macroscopic analogy that might help you imagine this is to put a hula hoop in a flowing river. As you change the angle of the hoop relative to the direction of the current, more or less of the flow will go through the hoop. Similarly, the amount of flow through the hoop depends on the strength of the current and the size of the hoop. Again, flux is a general concept; we can also use it to describe the amount of sunlight hitting a solar panel or the amount of energy a telescope receives from a distant star, for example.
To quantify this idea, Figure 6.4(a) shows a planar surface of area that is perpendicular to the uniform electric field If N field lines pass through , then we know from the definition of electric field lines (Electric Charges and Fields) that or
The quantity is the electric flux through . We represent the electric flux through an open surface like by the symbol . Electric flux is a scalar quantity and has an SI unit of newton-meters squared per coulomb (). Notice that may also be written as , demonstrating that electric flux is a measure of the number of field lines crossing a surface.
Now consider a planar surface that is not perpendicular to the field. How would we represent the electric flux? Figure 6.4(b) shows a surface of area that is inclined at an angle to the xz-plane and whose projection in that plane is (area ). The areas are related by Because the same number of field lines crosses both and , the fluxes through both surfaces must be the same. The flux through is therefore Designating as a unit vector normal to (see Figure 6.4(b)), we obtain
Check out this video to observe what happens to the flux as the area changes in size and angle, or the electric field changes in strength.
For discussing the flux of a vector field, it is helpful to introduce an area vector This allows us to write the last equation in a more compact form. What should the magnitude of the area vector be? What should the direction of the area vector be? What are the implications of how you answer the previous question?
The area vector of a flat surface of area A has the following magnitude and direction:
- Magnitude is equal to area (A)
- Direction is along the normal to the surface (); that is, perpendicular to the surface.
Since the normal to a flat surface can point in either direction from the surface, the direction of the area vector of an open surface needs to be chosen, as shown in Figure 6.5.
Since is a unit normal to a surface, it has two possible directions at every point on that surface (Figure 6.6(a)). For an open surface, we can use either direction, as long as we are consistent over the entire surface. Part (c) of the figure shows several cases.
However, if a surface is closed, then the surface encloses a volume. In that case, the direction of the normal vector at any point on the surface points from the inside to the outside. On a closed surface such as that of Figure 6.6(b), is chosen to be the outward normal at every point, to be consistent with the sign convention for electric charge.
Now that we have defined the area vector of a surface, we can define the electric flux of a uniform electric field through a flat area as the scalar product of the electric field and the area vector, as defined in Products of Vectors:
Figure 6.7 shows the electric field of an oppositely charged, parallel-plate system and an imaginary box between the plates. The electric field between the plates is uniform and points from the positive plate toward the negative plate. A calculation of the flux of this field through various faces of the box shows that the net flux through the box is zero. Why does the flux cancel out here?
The reason is that the sources of the electric field are outside the box. Therefore, if any electric field line enters the volume of the box, it must also exit somewhere on the surface because there is no charge inside for the lines to land on. Therefore, quite generally, electric flux through a closed surface is zero if there are no sources of electric field, whether positive or negative charges, inside the enclosed volume. In general, when field lines leave (or “flow out of”) a closed surface, is positive; when they enter (or “flow into”) the surface, is negative.
Any smooth, non-flat surface can be replaced by a collection of tiny, approximately flat surfaces, as shown in Figure 6.8. If we divide a surface S into small patches, then we notice that, as the patches become smaller, they can be approximated by flat surfaces. This is similar to the way we treat the surface of Earth as locally flat, even though we know that globally, it is approximately spherical.
To keep track of the patches, we can number them from 1 through N . Now, we define the area vector for each patch as the area of the patch pointed in the direction of the normal. Let us denote the area vector for the ith patch by (We have used the symbol to remind us that the area is of an arbitrarily small patch.) With sufficiently small patches, we may approximate the electric field over any given patch as uniform. Let us denote the average electric field at the location of the ith patch by
Therefore, we can write the electric flux through the area of the ith patch as
The flux through each of the individual patches can be constructed in this manner and then added to give us an estimate of the net flux through the entire surface S, which we denote simply as .
This estimate of the flux gets better as we decrease the size of the patches. However, when you use smaller patches, you need more of them to cover the same surface. In the limit of infinitesimally small patches, they may be considered to have area dA and unit normal . Since the elements are infinitesimal, they may be assumed to be planar, and may be taken as constant over any element. Then the flux through an area dA is given by It is positive when the angle between and is less than and negative when the angle is greater than . The net flux is the sum of the infinitesimal flux elements over the entire surface. With infinitesimally small patches, you need infinitely many patches, and the limit of the sum becomes a surface integral. With representing the integral over S,
In practical terms, surface integrals are computed by taking the antiderivatives of both dimensions defining the area, with the edges of the surface in question being the bounds of the integral.
To distinguish between the flux through an open surface like that of Figure 6.4 and the flux through a closed surface (one that completely bounds some volume), we represent flux through a closed surface by
where the circle through the integral symbol simply means that the surface is closed, and we are integrating over the entire thing. If you only integrate over a portion of a closed surface, that means you are treating a subset of it as an open surface.
Flux of a Uniform Electric Field A constant electric field of magnitude points in the direction of the positive z-axis (Figure 6.9). What is the electric flux through a rectangle with sides a and b in the (a) xy-plane and in the (b) xz-plane?
Strategy Apply the definition of flux: , where the definition of dot product is crucial.
- In this case,
- Here, the direction of the area vector is either along the positive y-axis or toward the negative y-axis. Therefore, the scalar product of the electric field with the area vector is zero, giving zero flux.
Significance The relative directions of the electric field and area can cause the flux through the area to be zero.
Flux of a Uniform Electric Field through a Closed Surface A constant electric field of magnitude points in the direction of the positive z-axis (Figure 6.10). What is the net electric flux through a cube?
Strategy Apply the definition of flux: , noting that a closed surface eliminates the ambiguity in the direction of the area vector.
Solution Through the top face of the cube,
Through the bottom face of the cube, because the area vector here points downward.
Along the other four sides, the direction of the area vector is perpendicular to the direction of the electric field. Therefore, the scalar product of the electric field with the area vector is zero, giving zero flux.
The net flux is .
Significance The net flux of a uniform electric field through a closed surface is zero.
Electric Flux through a Plane, Integral Method A uniform electric field of magnitude 10 N/C is directed parallel to the yz-plane at above the xy-plane, as shown in Figure 6.11. What is the electric flux through the plane surface of area located in the xz-plane? Assume that points in the positive y-direction.
Strategy Apply , where the direction and magnitude of the electric field are constant.
Solution The angle between the uniform electric field and the unit normal to the planar surface is . Since both the direction and magnitude are constant, E comes outside the integral. All that is left is a surface integral over dA, which is A. Therefore, using the open-surface equation, we find that the electric flux through the surface is
Significance Again, the relative directions of the field and the area matter, and the general equation with the integral will simplify to the simple dot product of area and electric field.
Inhomogeneous Electric Field What is the total flux of the electric field through the rectangular surface shown in Figure 6.12?
Strategy Apply . We assume that the unit normal to the given surface points in the positive z-direction, so Since the electric field is not uniform over the surface, it is necessary to divide the surface into infinitesimal strips along which is essentially constant. As shown in Figure 6.12, these strips are parallel to the x-axis, and each strip has an area
Solution From the open surface integral, we find that the net flux through the rectangular surface is
Significance For a non-constant electric field, the integral method is required. | 0.803397 | 3.452694 |
NASA's Hubble Space Telescope has trained its razor-sharp eye on one of the universe's most stately and photogenic galaxies, the Sombrero galaxy, Messier 104 (M104). The galaxy's hallmark is a brilliant white, bulbous core encircled by the thick dust lanes comprising the spiral structure of the galaxy. As seen from Earth, the galaxy is tilted nearly edge-on. We view it from just six degrees north of its equatorial plane. This brilliant galaxy was named the Sombrero because of its resemblance to the broad rim and high-topped Mexican hat.
At a relatively bright magnitude of +8, M104 is just beyond the limit of naked-eye visibility and is easily seen through small telescopes. The Sombrero lies at the southern edge of the rich Virgo cluster of galaxies and is one of the most massive objects in that group, equivalent to 800 billion suns. The galaxy is 50,000 light-years across and is located 28 million light-years from Earth.
Hubble easily resolves M104's rich system of globular clusters, estimated to be nearly 2,000 in number — 10 times as many as orbit our Milky Way galaxy. The ages of the clusters are similar to the clusters in the Milky Way, ranging from 10-13 billion years old. Embedded in the bright core of M104 is a smaller disk, which is tilted relative to the large disk. X-ray emission suggests that there is material falling into the compact core, where a 1-billion-solar-mass black hole resides.
In the 19th century, some astronomers speculated that M104 was simply an edge-on disk of luminous gas surrounding a young star, which is prototypical of the genesis of our solar system. But in 1912, astronomer V. M. Slipher discovered that the hat-like object appeared to be rushing away from us at 700 miles per second. This enormous velocity offered some of the earliest clues that the Sombrero was really another galaxy, and that the universe was expanding in all directions.
The Hubble Heritage Team took these observations in May-June 2003 with the space telescope's Advanced Camera for Surveys. Images were taken in three filters (red, green, and blue) to yield a natural-color image. The team took six pictures of the galaxy and then stitched them together to create the final composite image. One of the largest Hubble mosaics ever assembled, this magnificent galaxy has an apparent diameter that is nearly one-fifth the diameter of the full moon.
Object Names: Sombrero Galaxy, M104, NGC 4594
Credit: NASA and The Hubble Heritage Team (STScI/AURA) | 0.836606 | 4.046613 |
Our solar system's first known interstellar visitor is likely even more alien than previously imagined, a new study suggests.
The mysterious, needle-shaped object 'Oumuamua, which was spotted zooming through Earth's neighborhood last October, probably originated in a two-star system, according to the study.
'Oumuamua means "scout" in Hawaiian; the object was discovered by researchers using the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), at Haleakala Observatory on the island of Maui. ['Oumuamua: The 1st Interstellar Visitor in Photos]
Astronomers could tell that the 1,300-foot-long (400 meters) 'Oumuamua wasn't from around here based on its hyperbolic orbit, which showed that the object wasn't gravitationally bound to the sun. Initially, scientists thought the body was probably a comet. But 'Oumuamua displayed no cometary activity — no long tail, no cloud-like "coma" around its core — even after getting relatively close to the sun, so it was soon reclassified as an asteroid.
"It's really odd that the first object we would see from outside our system would be an asteroid, because a comet would be a lot easier to spot, and the solar system ejects many more comets than asteroids," study lead author Alan Jackson, a postdoctoral researcher at the Centre for Planetary Sciences at the University of Toronto Scarborough, said in a statement.
But 'Oumuamua probably didn't come from a system like our own, according to the new study. Jackson and his colleagues performed computer-modeling work, which indicated that systems with two close-orbiting stars boot out asteroids much more efficiently than one-star systems do.
And there are a lot of these binary systems out there; previous research has suggested that more than half of all Milky Way stars have close stellar companions.
Nobody knows for sure where 'Oumuamua came from or how long it's been voyaging through deep space. But the odds are good that it was born into a binary system that harbors at least one big, hot star, according to the new study. That's because such systems are likely to have predominately rocky (as opposed to icy) bodies orbiting relatively close in, in the prime ejection zone.
And 'Oumuamua was likely booted out during its natal system's planet-formation period, however long ago that may have been, Jackson and his team said.
'Oumuamua made its closest approach to Earth — about 15 million miles (24 million kilometers) — on Oct. 14. The object is now barreling toward the outer solar system and has been too distant and faint to study even with large telescopes since mid-December, NASA officials have said. But astronomers gathered a slew of data about 'Oumuamua while they could, and they will doubtless be mining this information for a long time to come.
"The same way we use comets to better understand planet formation in our own solar system, maybe this curious object can tell us more about how planets form in other systems," Jackson said.
The new study was published today (March 19) in the journal Monthly Notices of the Royal Astronomical Society. | 0.92838 | 3.895482 |
Jan 30, 2012
The Sun is predicted to “hibernate” during its next cycle in 2020.
A recent press release states that the Sun’s activity will slow to an unprecedented decline in the next ten years. The prediction is based on “…three independent studies of the sun’s insides, surface, and upper atmosphere…” According to the article, the drop in output could initiate climate effects comparable to the Maunder Minimum between 1645 and 1715.
Predictions about how the Sun will behave are reliable only if the interpretation of the data upon which the prediction was made is reliable. As many past Picture of the Day expositions have revealed, however, conventional theories of solar dynamics leave much to be desired. For example, attributing to internal heating the unexpected “weather patterns” recently discovered below the photosphere is like ascribing Earth’s weather patterns to heat escaping from within the Earth. The possibility that weather systems may be externally electrically powered has not occurred to investigators.
The Electric Universe theory proposes that stars are primarily electrical phenomena and not strictly based on gravitational compression somehow balanced by internal thermonuclear energy. Stars are electromagnetic in nature, responding to the laws of plasma physics and electric circuits and not those of gas dynamics or electrostatics.
This alternative view applies to the Sun, as well as to all other stars that populate the Universe: celestial bodies exist in conducting cosmic plasma and are connected by electric circuits. The Sun is “plugged-in” to a galactic power source and behaves like an electric motor and electric light. The faster rotation of the solar equator is prima facie evidence of an external force acting to offset the momentum loss of the solar wind.
Electric stars are not born from cold nebular clouds. Rather, their genesis resides in the electric currents induced in moving plasma. The electric currents induce their own encircling magnetic field, which “pinches” the currents to flow in filaments. Photographs of plasma in the laboratory show those currents forming twisted filament pairs called “Birkeland currents.” Birkeland currents follow magnetic field lines, drawing ionized gas and dust from their surroundings and then “pinching” it into heated blobs called plasmoids.
As the so-called “z-pinch” effect increases, it strengthens the magnetic field, further increasing the z-pinch. The resulting plasmoids form spinning electrical discharges that glow first as red stars, then “switch discharge modes” into yellow stars, some intensifying into brilliant ultraviolet arcs, driven externally by the Birkeland currents that created them.
Since this view of the Sun is at great variance with the conventional view, the mainstream “predictions” concerning solar activity should probably be taken with a grain of salt.
Stephen Smith and Wal Thornhill | 0.851137 | 3.679192 |
Apr 11, 2012
Black hole theory contradicts itself.
Most astrophysicists try to explain narrow jets erupting from various sources by using words like “nozzle” or “high pressure,” contradicting the known behavior of gases in a vacuum. For example, according to a recent press release, “flares” have been discovered jetting from a source close to the center of our galaxy. Consensus opinions call that source a black hole.
As Poshak Gandhi from the Japan Aerospace Exploration Agency (JAXA) said, “If you think of the black hole’s jet as a fire hose, then it’s as if we’ve discovered the flow is intermittent and the hose itself is varying wildly in size.”
Discovered by the Wide-field Infrared Survey Explorer (WISE), GX 339-4 is approximately 20,000 light-years away. It is conventionally presumed to be at least six times more massive than the Sun, with a gravity field 30,000 times more powerful than Earth. GX 339-4’s extreme activity is supposed to be due to a companion star “feeding” its stellar matter into the black hole’s putative gravity well. However, some of that material gets blasted into space at close to light speed.
The mechanisms by which intense gravitational fields eject tightly collimated steams of matter are not understood. It is thought that strong magnetic fields are required, but the source of that magnetism is not known, since no mention of electricity exists in the reports about such phenomena.
Some flares and X-ray jets are thought to be generated by heat from molecular collisions, causing the gas to glow. As theories indicate, gamma rays might also appear when the super-accelerated matter is eventually sucked into the black hole. Excess heat, X-rays, and gamma rays are not created by gravity. In laboratory experiments, it has been found that they are most easily produced when charged particles are accelerated through an electric field.
Previous Picture of the Day articles about black holes suggested that the terminology used to describe “gravitational point sources” is highly speculative: space/time, singularities, and infinite density are abstract concepts, precluding a realistic investigation into the nature of the Universe.
Stars are nodes in electrical circuits. Electromagnetic energy could be stored in the equatorial current sheets surrounding them until some trigger event causes them to switch into a polar discharge. The electric jet could receive its energy from a natural particle-accelerator, a “plasma double layer” with a strong electric field. Toroidal magnetic fields would form because of the polar plasma discharge, confining it into a narrow channel.
Axial electric currents should be flowing along the jet’s entire length. Only electric fields can accelerate charged particles across interstellar space.
There is no evidence that matter can be compressed to “infinite density.” Z-pinches in plasma filaments form plasmoids that become stars and galaxies. Electricity is responsible for star birth, as well as death. When current density gets too high, double layers in the stellar circuit catastrophically release excess energy, appearing as gamma ray bursts, or X-rays, or thermal flares.
Hat tip to Larry White
Editor’s note: On February 1, 2011 NASA’s Wide-field Infrared Survey Explorer was shut down. | 0.837161 | 3.904044 |
Image credit: SOHO
Comets usually don’t survive an encounter with the Sun, but SOHO captured images of a pair of extremely lucky comets that grazed the surface, well within the Sun’s fiery corona. It’s unusual for comets to travel in pairs like this, but what’s even more unusual is a faint puff of smoke emanating from the Sun at the point of the comets’ closest approach. It’s possible that the Sun evaporated the cloud of ice and dust away from the comets, essentially blasting their heads off. Studying this puff of dust may give astronomers additional clues about the composition of comets.
On May 24, 2003, a pair of comets arced in tandem towards the Sun, their path taking them to just 0.1 solar radii above the Sun’s surface, deep within the searing hot corona.
They belong to the Kreutz family of sun-grazing comets, often seen by SOHO while diving towards their final rendezvous with the Sun. But as in humans, twins are rare! Even more so, this pair showed another very unusual trait: What looks like a faint tail (or “puff of smoke”) can be seen moving away from the Sun, seemingly emanating from a point in the orbit beyond the comet’s closest approach! Normally, sungrazers simply fade and disappear at an earlier stage, obliterated by the intense heat and pressure.
Another pair of Kreutz sungrazers with such a “headless tail” was observed in June 1998 (see MPEG [ 677k] movie), when the observing geometry was very similar. But out of more than 600 sungrazing comets observed during more than six years by SOHO, this is only the third showing any signs of such behaviour!
The puff is most likely the dusty remains of the comet’s nucleus, being pushed out by the radiation pressure after all the ice in the nucleus has evaporated, thus eliminating the processes maintaining a bright coma surrounding the core. Studies of the dust cloud may reveal clues to the size distribution of the dust grains.
Comets are balls of dust and ice that zoom around space in elongated orbits. Their dust tails are pushed by the radiation pressure from the Sun. Their ion tails (usually fainter) are pushed away from the Sun by the solar wind. Both tails point away from the Sun, even for comets that are travelling back outwards in the solar system.
Original Source: SOHO News Release | 0.862334 | 3.96969 |
University students and researchers working on a NASA mission orbiting a near-Earth asteroid have made an unexpected detection of a phenomenon 30 thousand light-years away. Last fall, the student-built Regolith X-Ray Imaging Spectrometer (REXIS) onboard NASA’s OSIRIS-REx spacecraft detected a newly flaring black hole in the constellation Columba while making observations off the limb of asteroid Bennu.
REXIS, a shoebox-sized student instrument, was designed to measure the X-rays that Bennu emits in response to incoming solar radiation. X-rays are a form of electromagnetic radiation, like visible light, but with much higher energy. REXIS is a collaborative experiment led by students and researchers at MIT and Harvard, who proposed, built, and operate the instrument.
On November 11, 2019, while the REXIS instrument was performing detailed science observations of Bennu, it captured X-rays radiating from a point off the asteroid’s edge. “Our initial checks showed no previously cataloged object in that position in space,” said Branden Allen, a Harvard research scientist and student supervisor who first spotted the source in the REXIS data.
The glowing object turned out to be a newly flaring black hole X-ray binary – discovered just a week earlier by Japan’s MAXI telescope – designated MAXI J0637-430. NASA’s Neutron Star Interior Composition Explorer (NICER) telescope also identified the X-ray blast a few days later. Both MAXI and NICER operate aboard NASA’s International Space Station and detected the X-ray event from low Earth orbit. REXIS, on the other hand, detected the same activity millions of miles from Earth while orbiting Bennu, the first such outburst ever detected from interplanetary space.
“Detecting this X-ray burst is a proud moment for the REXIS team. It means our instrument is performing as expected and to the level required of NASA science instruments,” said Madeline Lambert, an MIT graduate student who designed the instrument’s command sequences that serendipitously revealed the black hole.
X-ray blasts, like the one emitted from the newly discovered black hole, can only be observed from space since Earth’s protective atmosphere shields our planet from X-rays. These X-ray emissions occur when a black hole pulls in matter from a normal star that is in orbit around it. As the matter spirals onto a spinning disk surrounding the black hole, an enormous amount of energy (primarily in the form of X-rays) is released in the process.
“We set out to train students how to build and operate space instruments,” said MIT professor Richard Binzel, instrument scientist for the REXIS student experiment. “It turns out, the greatest lesson is to always be open to discovering the unexpected.”
The main purpose of the REXIS instrument is to prepare the next generation of scientists, engineers, and project managers in the development and operations of spaceflight hardware. Nearly 100 undergraduate and graduate students have worked on the REXIS team since the mission’s inception.
NASA’s Goddard Space Flight Center in Greenbelt, Maryland, provides overall mission management, systems engineering, and the safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space in Denver built the spacecraft and provides flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program, which is managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington. | 0.890068 | 3.983629 |
It all started back in the olden-days of mid-2007 with GalaxyZoo: the ultimate in online, interactive citizen science where anyone with eyes, an Internet connection, patience, and an appreciation for beautiful galactic images from the Sloan Digital Sky Survey could make a reasonably important contribution to astrophysical scientific research. Driven by the initial success of this project, including an in-press research paper featuring the discovery of an ionisation nebula coined “Hanny’s Voorwerp” from a GalaxyZoo user, the supporting researchers of GalaxyZoo and the Citizen Science Alliance are rapidly developing new research interfaces based on the original GalaxyZoo model under a canopy program call “Zooinverse.”
From mapping the surface of the Moon, watching for solar flares, identifying merging galaxies, sorting and mapping our Milky Way … and more … the Zooinverse program offers wonderful opportunities for anyone at home to interact with our amazingly expansive universe and help better understand what is out there. All of these projects are important for keeping an eye on our local galactic neighborhood and mapping the greater cosmos.
Now, launched just earlier this month, the most critical and valuable Zooniverse project has begun: Planet Hunters.
We live on an amazing planet. It has perfect habitats for our species and human being continue to thrive on Earth. However, 2011 marks a predicted global population of 7 billion with a rapid rise to 9 billion in 2045 (read the current feature in National Geographic, January 2011). Earth is a very big place, and people are very little inhabitants. So, this planet really can handle quite a bit of our exponentially-increasing consumption, and it will successfully deal with our ways for millennia. However, humanity does like to take up a lot of space, and the long term dilemma might be that we as a species won’t be able to handle ourselves in such large numbers.
Just like the development of simple tools and all subsequent technology is a defining and fundamental evolutionary advantage of homo sapiens, one of the next big leaps using our technology will be discovering, traveling to, and inhabiting another home in the Universe. The goal should not be to find a replacement homestead (unless an asteroid places us in its gravitationally-driven cross-hairs — keep an eye out yourself for close approaches), but rather just a galactic expansion plan for human beings.
Any possible home away from home, however, will be in a neighborhood far from our spot in the Milky Way. The nearest star to Earth — Proxima Centauri — is 4.2 light years, or nearly 25 trillion miles (40 trillion km) away. That’s a long trip no matter what units you use! And, unfortunately for us there doesn’t seem to be a pale blue dot orbiting Proxima Centauri. So, without a doubt, an impressive technological advancement in human transportation must be developed before any upward and outward expansion launches. And before we can even set our sights onto another inhabitable planet, we, of course, need to actually find one — if one even exists!
If planets orbiting stars throughout our galaxy and others have not been an assumed notion for at least the duration of what current history labels “modern science,” then their existence certainly has been imagined, anticipated, and thoroughly written about. We just have to find them.
The two key planet hunting techniques successfully used over the past two decades to reign in a host of extrasolar planetary systems were initially suggested in 1952 by Otto Struve (1897-1963) while at the University of California, Berkeley. Struve suggested that it should not be unreasonable that Jupiter-sized objects might be orbiting very close to its host star, in contrast to our own system. Finding a large planetary mass together with a small orbit radius and high orbital frequency would make it possible to detect the gravitationally-induced spatial oscillations of the host star due to the planet.
Struve offered the important caveat that this approach — called the “wobble method” — which would be most reasonable with orbiting systems that are aligned with a line of sight toward an observer on Earth near a 90° inclination; i.e., so that the orbit crosses an observer’s view point perpendicularly rather than straight on and the reactive motion of the star would face “toward Earth”.
He also suggested a second method — the “wink method” — currently used today for detecting decreases in starlight intensity as an orbiting object passes directly between its host star and an Earth observer’s line of sight.
Struve, O. “Proposal for a project of high-precision stellar radial velocity work.” The Observatory, vol. 72, pp. 199-200 (1952). [download the original paper]
With technological advances in instrumentation sensitivity since Struve’s proposal, these very methods, along with additional new ideas, have been used with great success in discovering and measuring basic physical properties of extrasolar planets. For a more detailed review of the “wobble,” “wink,” and other methods, including direct imaging, please read the DPR review article on Extrasolar Planet Discovery Techniques.
It wasn’t until 1992 that human beings finally discovered an extrasolar planet so long envisioned. Today, there is a rapidly increasing list of extrasolar, or “exoplanets”, on the record books with many teams around the world working at a feverish pace to find more and discover weird, new behaviors in our Universe. One official count maintained by Jean Schneider of the Paris Observatory and the Extrasolar Planets Encyclopedia sets the total discoveries at 515 identified exoplanets as of December 25, 2010. A previous check of this catalog by DPR — on June 27, 2005 — found only 160 planets identified, so the discovery rate is certainly impressive.
The mission of discovering planets in other solar systems is so exciting, and yet so grueling that professional astronomers formally opened up the hunt to the avid amateur community. There is a great deal of grunt work and extensive measurement time involved with systematically searching the countless visible stars in the sky for the off-chance that a planetary orbit may be observed; and time is expensive when big telescopes and federal grants are required to make progress. Planet hunter and professor at University of California, Santa Cruz, Gregory Laughlin, established TransitSearch.org to guide amateur astronomers with a good telescope and a lot of patience in searching for likely candidate stars as hosts for planets. Bruce Gary has written the detailed, 253-page guide “Exoplanet Observing for Amateurs, Second Edition,” which he has made available as a free PDF e-book [ download now ]. Amateurs may learn from this valuable resource on how to take your backyard telescope and transform it into an optimal planet-hunting machine.
On March 6, 2009, NASA launched its tenth Discovery Mission called Kepler, which is designed to directly monitor the brightness of 100,000 sun-like stars in our neck-of-the-woods of the Milky Way. Using the “wink method,” the light curves fed to Earth from Kepler can be analyzed to look for signatures of transiting bodies. If the measured light intensity from a star drops, there might be a transiting body. If the intensity drops again, and again — in a stable, periodic way — then there just might be an orbiting planet.
Once an orbit is identified, then a great deal of information can be calculated, including a reasonable prediction if the planet might be habitable based on our human standards of what makes a nice home. Using the period of the orbit calculated from the observed repetition of the drop in star brightness, the orbit size can be determined. And, along with the observed temperature of the star, a characteristic temperature of the planet can be estimated. (Read more about the Kepler mission and learn more about NASA’s Center for Exoplanet Science.)
So far, researchers have confirmed eight planets from the light curves provided by Kepler. Each of these eight rocks seem to be very hot, very big, and very close to their host star. In other words, not so pleasant.
But this is only the beginning of the search! Kepler is continuously scanning thousands of stars, and there are many light curves to individually review. All of the data is being made available to the public for download and review through an online archive funded by NASA, but the interface is rather cumbersome for the interested amateur. So, this is where the team at Zooinverse enters into the game…
The creators of Galaxy Zoo have developed their latest interface that takes the raw light curve data from the public Kepler database and presents it to users in a scalable graph. After presenting a particular data set, the interface asks you a few simple questions about what you see. The questions are relatively trivial for a human observer with our extremely efficient pattern recognition abilities, but extraordinarily difficult for an automated computer program scanning the data points. It is this fundamental advantage over artificial intelligence code that offers not only the beauty of the Planet Hunters project, but also is the essence for why citizen scientists can be so crucial to important scientific pursuits.
Many of the measured stars look like the data set presented above: the brightness measured from the star varies somewhat randomly over a period of time, but maintains a simple average level with the variation due to white noise or random behavior in the star’s activity. Other data might show a clearly periodic or cyclical pattern to the brightness, which represents a pulsating star, or it might have a very irregular brightness pattern, but the variation occurs over a smooth, continuous curve.
If a star has another massive orbiting body pass directly through the line-of-sight of the Kepler telescope toward the star, then a sudden dip in the brightness will be measured. This rapid dip is due to the orbiting body — most likely a planet! — blocking some of the light radiating from the star. If this extreme dip is seen periodically, then the full orbit of the planet can be measured.
On December 27, 2010, Dynamic Patterns Research was fortunate enough to help classify a very clear example of a light curve that might represent two separate orbiting planets around SPH10122348, a dwarf star with apparent visual magnitude of 12.9, a temperature of 5,625 K, and a radius of about 1.7 times that of the Sun (view the light curve with a Google star map).
The data interface for SPH10122348 presents a “quiet” star with apparently constant brightness, within some random variation, but it has four extremely dramatic dips in brightness. Two of the dips are relatively shallow — representing a smaller orbiting planet that only covers a small fraction of the star, and the other two dips are particularly deep — possibly showing a very large planet that obscures a larger portion of the star, at least from the view of Kepler.
The four blue outlined boxes are part of the intuitive interface, which are movable and scalable boxes that the user may manipulate to identify potential transit data. Here, we placed two shorter boxes over the “small” transiting body, and two long boxes over the “larger” transit. The classification is saved and reported into the researchers at Zooinverse to review, further analyze and send back through the system to allow other users to make independent confirming classifications of the same data.
Once a light curve has been identified and vetted as a potential candidate for an exoplanet, the research team will identify which users were involved in the classification and post the results on their candidate page (view current list). Further review will check to make sure the star is not already on a previously identified list from either Kepler or older observations. If the data appears to be a new discovery, then the research team will follow up with spectroscopic data from the Keck telescope in Hawaii, and if further screening tests are passed, then the result will be submitted for publication. Citizen scientists who participated in identifying the transiting planets will be included as co-authors on all published research papers.
Scientists around the world are looking for planets around other stars, and with the power of citizen science you can now play an integral role in this critical research. This is a prime moment for citizen scientists to prove their value in professional scientific work, and this opportunity is extremely easy to dive into. Unleash your citizen scientist and start hunting planets now… | 0.936904 | 3.319254 |
The distance between moon and earth is just 384,400 km. So, if we can travel (from moon) to another planet, we also can travel (from earth) to the same planet. But I've read that some scientists want a moon base although we can have an earth base. Why? What are the advantages of a moon base.
The reason many scientists want to create a Moon base isn't because of distances in space, it's because of gravity wells. The amount of energy to escape the gravity well of a body in space depends on the mass of said body. For example, the amount of energy required to take off from Earth and go to low Earth orbit is MUCH higher than the amount of energy it takes to take off from the moon and reach low Earth orbit. The Moon has a much lower mass and therefore a much lower gravity well.
The practical XKCD 681 gives a very intuitive example of the amount of energy it takes to get out of a planet (or moon's!) gravity well.
The amount of fuel a rocket needs to "escape" the planet is shown by the depth of the well in this chart. On the bottom right you can see that the gravity well of earth is much deeper than that of the Moon.
Another easy example is in fuel costs. This image shows fuel costs of the Apollo Moon missions:
Don't be fooled by the broken bar for launch. If you were to actually draw this chart to scale, it would be impossible to read as launch fuel costs were around 96% of fuel costs for the entire mission. This means that the Apollo mission used 96% of it's fuel taking off and getting into low Earth orbit. With the remaining 4% of fuel the astronauts went to the Moon, entered orbit, landed, took off, and flew back to earth.
In short, having a Moon base which produces fuel from resources available on the Moon (water ice probably) would mean that you could save enormous amounts of fuel on all missions in space. Instead of having to launch all the fuel you will need on a Mission from Earth (where the launch is very expensive), you could simply refuel at the Moon.
In fact, if asteroid mining ever becomes a reality, it will likely be cheaper to import metal from asteroids for use in earth orbit than to send the metal up from Earth because although asteroids are much further away, the energy requirement to move there and back is far lower than a launch from the surface of Earth to space, or as the old maxim goes: "Once you've reached orbit, you're halfway to anywhere"
The lower gravity and lack of atmosphere appear well suited to launching rockets. The assumption is that available resources that would not have to be brought from Earth will be obtainable on The Moon at lower cost. However the infrastructure required for making effective use of Lunar resources at the level of sophistication needed for a major space launch facility - and the distance to major centres of high tech industry to support it - means doing so is likely to remain prohibitively expensive for the foreseeable future.
A lot of hypothetical preliminary steps need to be achieved successfully for The Moon to be demonstrably better or cheaper than other options for a space launch facilities - ie better than ongoing direct launches from Earth or from orbital facilities.
One reason could be the weather is better on the Moon.
Rocket launches from Earth are complicated by weather, which could lead to launch postponements. Meanwhile celestial mechanics marches on, oblivious to the puny clouds on a portion of one small planet, so launch windows are limited. Going to the Moon is less weather-sensitive because the Moon is bound to Earth. Then, there are fewer weather issues for the subsequent interplanetary launch from the Moon. | 0.807865 | 3.324107 |
When you gaze towards a clear moonless night sky, the stars appear as points of light – most are colorless. There are a few exceptions, however: Mars, Aldebaran and the star at the heart of the constellation Scorpius, Antares, can be seen to have a very slight reddish hue. Through a small telescope, star and planetary colors become more apparent but galaxies and nebulas remain un-pigmented and monochromatic. These objects begin to take on a greenish ting when viewed through very large telescopes but rarely show the rainbow of hues seen in many deep space pictures, like the one shown here.
This begs the question that is often asked of astrophotographers: are those the real colors or did you make them up?
The human eye’s retina contains two types of photoreceptors called rods and cones. There are about 120 million rods compared to approximately 7 million cones. Rods are more sensitive to light but only cones detect color. This is why we can make out objects that surround us, in dimly lit situations, but we cannot discern their hue. Light is comprised of three primary colors, red, blue and green. Of these, the cones in our eyes are most sensitive to the later, which makes some evolutionary sense if your ancestor’s survival was dependant upon discerning plants.
Astronomical telescopes are essentially used for two purposes: 1) to help separate distant but closely spaced objects and 2) to collect a lot of light. The amount of light collected by even the world’s largest telescopes is still insufficient for the cones in our eyes to detect color in faint nebula and galaxies other than green. Therefore, the full color of distant astronomical places, other than stars and planets, is something that still eludes direct observation. It should be noted, however, that there have been some rare claims of seeing other colors by a few observers who may simply have eyes with more color sensitivity.
But film and digital cameras do not have this type of color bias. Film emulsion contains crystals that are sensitive to each of the three primary colors of light and color digital cameras place microscopic red, green or blue filters on top of their pixels. Manufacturers use various schemes to place these filters, it should be noted, but here’s the point: only a portion of the pixels in any color digital camera are dedicated to one color. Regardless, this enables cameras to detect color much more efficiently than human eyes. Digital astronomical cameras go one-step further- they use every pixel for each color.
Cameras specifically designed for taking deep space images are unsurpassed for detecting very faint light but they only produce results in black and white. To create a full color picture, astronomers, both professional and amateur, place a red, green or blue filter in front of the camera so that every pixel is limited to detecting one specific color reflecting or shining from the astro-subject. This, by the way, is a very time consuming process. To create a full color picture, the astronomer digitally combines separate red, green and blues images using commercially available software like Photoshop. Thus, the colors seen in deep space objects taken through a camera are very real and, unless mis-handled during processing, they are also accurate.
One of the most colorful night sky locations, seen here, is located in the constellation of Scorpius, just to the north of its brightest star, Antares. This scene is a riot of colors and can best be seen in the full size image.
We are looking toward the heart of our galaxy and his picture captures a menagerie of space objects and places as we gaze into the distance. For example, there are three globular clusters. M80 is at the top and M4 is toward the bottom. Between them, to the upper left of M4, is NGC6144. The dark threads that swirl about are vast clouds of dust that absorb light and therefore appear as shadows. The bright clouds are also made of dust but these reflect light from nearby stars. Antares is just below the bottom of the image and provides the appearance of the sun at dawn.
This kaleidoscopic picture was produced by Steve Crouch using a 7-inch telescope that was specially designed for taking wide-angle photographs. Steve took this image from his home observatory located in Canberra, Australian Capital Territory, Australia during the month of June, 2006. Steve uses an 11 mega-pixel astronomical camera.
Written by R. Jay GaBany | 0.881532 | 3.9428 |
The verdict is in: after a thorough round of observations, the comet suspected of being an interstellar alien has been ratified. According to the International Astronomical Union (IAU), the comet is “unambiguously” interstellar in origin, and it has now been given a name: 2I/Borisov.
Previously, the comet had been going by the provisional name C/2019 Q4 (Borisov). C means it’s a comet with a hyperbolic orbit, followed by the year it was discovered, an alphanumeric code for when in the year it was discovered, and the comet name in parentheses – that’s Crimean amateur astronomer Gennadiy Borisov, who spotted the comet with telescope he made himself.
The new name has been simplified. In 2I, I stands for “interstellar”, and 2 for being the second interstellar object ever discovered, after ‘Oumuamua, which was detected in October 2017.
“In this case, the IAU has decided to follow the tradition of naming cometary objects after their discoverers, so the object has been named 2I/Borisov,” the IAU wrote.
Astronomers haven’t just been busy labelling the object; they have been furiously studying the comet to try and find out more about it.
According to observations and analysis so far, the comet is currently inbound towards the Sun, and will reach its closest approach (perihelion) on December 8 at a distance of 300 million kilometres (190 million miles) – about twice the average distance of Earth from the Sun.
The comet is approaching the planetary orbital plane – the ecliptic – at an angle of around 40 degrees, and is travelling at a breakneck 150,000 kilometres per hour (93,000 mph). It’s between 2 and 16 kilometres (1.2 and 10 miles) in diameter, and images of the object show a fuzzy outline typical of cometary outgassing, and even a tail.
Two recent analyses – one of the optical images showing the comet’s colour, the other of the comet’s spectra revealing its chemical composition – have revealed that it is similar to the Solar System’s long-period comets that originate in the distant Oort Cloud, rather than the short-period comets that come from closer in.
And a new paper just published by Polish astronomers on pre-print resource arXiv may have traced the comet’s trajectory to try and pinpoint where it came from.
The results didn’t conclusively point to an origin, but the paper suggests that, around a million years ago, 2I/Borisov passed the binary star Kruger 60 that’s located 13 light-years away. The comet ‘skimmed’ that star at a relatively close distance of 5.7 light-years, and at a lower velocity than the one it has currently – just 12,348 kilometres per hour.
Obviously that’s a very preliminary result – plotting an accurate trajectory is going to take months of observations, and studying the comet itself may yet yield some surprises.
In particular, it will be exciting to see just how closely similar it really is to Solar System comets, and if there are any noticeable differences.
The discovery, less than two years after the discovery of ‘Oumuamua, also shows that perhaps these interstellar visitors are not rare at all.
We can’t wait to meet 3I, 4I, 5I… | 0.849767 | 3.870716 |
This year, professional physicists and the few geeks who are still interested in science (should we call them nerds?) are celebrating General Relativity’s centenary.
Great. What of it then?
General Relativity breaks the record for flowery adjectives in science. It has been described as impossible to understand, poetic, beautiful, elegant and simple.
Surely it’s elegantly simple?
It’s hard to define ‘simple’ in scientific language. I more appropriate (and sober) description would be ‘complete’. General Relativity is the most complete theory of gravity known so far.
Why is it complete?
Because all gravitational phenomena we have observed so far can be modelled by General Relativity. It describes everything from falling apples, to the orbit of planets, the bending of light, the dynamics of galaxy clusters, and even black holes. The domain of validity of the theory covers a wide range of energy levels and scales. And scale is what physics is all about.
When the BICEP-2 experiment claimed to observe gravitational waves, there was a deeper (and probably more significant) result. It meant that General Relativity is valid up to the GeV energy scale, almost reaching the domain where quantum physics becomes the preferred description.
Can it describe the whole Universe?
Almost. Modern cosmology is based on General Relativity applied to a simple model of the Universe.
We have the field equations for gravity: the Einstein field equations.
We have the boundary conditions: homogeneity and isotropy, and the contents of the four-dimensional spacetime – matter or energy.
Put them together and you obtain a metric. Think of it as a generalised gravitational potential for the entire Universe.
Almost? What’s the catch?
The big questions in physics (we should really say Big Questions – they’re that important) , on this 100th birthday of General Relativity are the things that cannot be explained by this model: Dark Energy (the Universe doesn’t just expand, it accelerates), and Inflation (the initial the matter-energy distribution was not homogeneous).
Einstein published most of his papers on General Relativity in 1914. Why are we celebrating 2015?
Because the essential element of General Relativity is the field equations. Einstein had been working on the problem for some years, starting in 1907. He arrived at the final, correct form in 1915. And he was fully aware of the significance of this publication. He called it simply ‘The Field Equations of Gravitation’ (‘Feldgleichungen der Gravitation’, in Akademie der Wissenschaften, Sitzungsberichte 1915 (part 2) pages 844-847).
From then on, it was a matter of working out the derivations. | 0.804014 | 3.904185 |
How has the universe been formed and evolved? The Milky Way, our own galaxy, consists of several tens of billions of stars. How has it been formed and evolved? In the whole history of human civilization, these basic and profound questions inspirit people to explore the nature. The optical spectrum contains abundant physical information of distant celestial objects, and acquiring spectra of a large number of celestial objects is desperately needed in astronomy, which touches various cutting-edge researches of contemporary astronomy and astrophysics. The scientific goal of LAMOST focuses on the extragalactic observation, structure and evolution of the Galaxy, and multi-wave identification. The spectroscopic survey carried out by LAMOST of tens of millions of galaxies and others will make substantial contribution to the study of extra-galactic astrophysics and cosmology, such as galaxies, quasars and the large-scale structure of the universe. Its spectroscopic survey of large number of stars will make substantial contribution to the study of stellar astrophysics and the Galaxy. Its spectroscopic survey combining with the surveys in other wavebands, such as radio, infrared, X-ray and γ-ray will make important contribution to the cross-identification of multi-waveband of celestial objects. The large sample spectroscopic sky survey has been made dramatic progress in recent years, especially due to the success of 2dFand SDSS projects. With its powerful spectroscopic survey ability, LAMOST is expected to push it deeper and wider. To maximize the scientific potential of the facility, wide national participation and international collaboration have been emphasized. The survey has two major components: the LAMOST ExtraGAlactic Survey (LEGAS) and the LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) survey of Milky Way stellar structure. | 0.87359 | 3.039562 |
Hubble’s photo editor, Zoltan Levay, explains how he captures the invisible colors of the cosmos.
Zoltan Levay is eager to clear up a misconception about his job. Yes, he edits photos from the Hubble Space Telescope, but his work is not about subjective aesthetics. He’s an astronomer, and he’s not editing the images so much as enhancing them to reflect what’s really going on in distant galaxies. Thing is, galaxies can look awfully dim by the time their light makes it to Earth. Our eyes, which are wonderfully attuned to sunlight, are just plain “crappy,” Levay says, at seeing space, even in photographic form. So to make a vivid image of what’s actually going on in space, he has to make the invisible, visible. How? Here he describes his editing process for the “Pillars of Creation,” NASA’s iconic photograph of three gaseous plumes, 50 trillion kilometers in height, rising from a cluster of newborn stars in the Eagle Nebula, some 6,500 light years from Earth.
The raw materials
Hubble’s raw images arrive as black-and-white photographs. Each photo is taken three times at varying exposures, and then it’s Levay’s task to blend and combine to get the most accurate result. A distinct advantage of having three versions of the same image: Cosmic rays pepper Hubble’s light detector with random flecks of light and make the resulting images look like someone shook salt on them. By laying the three images on top of one another, Levay can spot — and remove — the rogue specks.
Once the images have been cleaned and stitched together, Levay adjusts the brightness of the pixels, each of which is assigned a value from 1 (pitch black) up to 65,000 (brightest white). That’s more shades of light than the human eye could ever detect, and often gradations in the images are so subtle, Levay can only spot the differences in the backend data of an image. He can accentuate the differences, however, by “clipping” the values of the brightest whites. Any pixel above a given threshold (say, 15,000), is set to maximum brightness, and the other pixels are brightened proportionately. The result? The tips of the pillars now shine nearly as brightly as the stars. “A few stars in this image are much, much brighter than anything in the nebula,” Levay says. So he suppressed their harsh glare, throwing the object of interest, the plumes of gas, into relief.
The Pillars of Creation may initially appear as pale, white plumes, but the elemental gases that make them — oxygen, hydrogen and sulfur — are actually tinged with faint colors. So you might discern a touch of cyan from the oxygen, a hint of red from the sulfur and a slightly lighter shade of red from the hydrogen. But when Hubble captures these lights, the resulting image is a pale muddle. How does Levay differentiate the colors? Photoshop. “We’re really translating colors,” he says, replacing the clouds’ subtler hues with vivid, primary colors. The images above, for instance, show his overlay of blue, green and red to accentuate the oxygen, hydrogen and sulfur in the plumes. And with that revised palette, he can repaint the pillars in colors that our eyes can more easily differentiate. Yes, it’s slightly artificial, but the colors help us see details of the pillars that might otherwise get lost. “By looking at these different individual elements you can tease out the structure,” Levay says.
Unleash the inner art critic
Levay then uses Photoshop to layer the red, green and blue images together. The result is a technicolor rendition of the nebula. But Levay isn’t done yet. “This just looks flat and muddy,” he says, “and it has an overall green cast to it, while the stars have a very strong magenta cast to them. That’s actually an artifact of the way the Hubble filters are designed.” At this point, Levay allows himself a little creative freedom, toning down the green, accentuating shadows at the center of the pillars and adding a hint of brightness to the tips of the plumes. The adjustments are slight and sparing. “You want to adjust it so that you keep those, as a photographer would say, shadow details,” he says.
Ready for mass consumption
NASA released this final image to the public in January 2015. Levay hopes it will give the public a better sense of the strange, invisible forces of the cosmos. Even after two decades of overseeing Hubble’s eight-person imaging team, he still gets a thrill from the finished product. “There are winds blowing from stars at hundreds of miles a second,” he says. “There is an immense amount of very high energy radiation going on in these clouds and that’s what’s causing them to have these forms. I hope the image gives people some inkling of the size, complexity and the dynamism that’s happening in a region of space like this.” | 0.830832 | 3.888731 |
[/caption]Naming Pluto explores the chain of events that lead to Pluto’s naming and in 2007 sees Venetia Phair viewing Pluto for the very first time through a telescope, on her 89th birthday, 77 years after Pluto’s discovery. A wonderful, intimate look into the story behind how Pluto got its name. A review of the short film directed and produced by Ginita Jimenez, distributed by Father Films.
In recent years, Pluto has seen its status change from being a planet to what many people view as a planetary underclass. The reasons behind this have been set out by the International Astronomical Union (IAU) to cater for the increasing number of Solar System bodies being discovered; the traditional nine planets have had to make room for a growing minor planet population. Unfortunately, Pluto was at the front line as it inhabits a region of space dominated by the gas giant Neptune, plus thousands of other Kuiper belt objects. Although the mysterious body lost its planetary status (as it does not have the ability to “clear its own orbit”), it has taken the title of “dwarf planet” and now has an entire class of object named in its honour: “Plutoids”.
However, the recent tumultuous history of the traditional “9th planet” has not impacted the fascination we have for Pluto. It has, and always will be, viewed with intrigue and wonder.
The key to Pluto’s romantic tale begins in the year 1930 when a mysterious heavenly was discovered by Clyde Tombaugh, a 23 year-old astronomer working at the Lowell Observatory in Flagstaff, Arizona. However, the honour of naming Pluto didn’t rest on Tombaugh’s shoulders. Over 5000 miles away in Oxford (UK) an 11 year old girl was having breakfast with her grandfather, wondering what this newly discovered planet should be called…
Naming Pluto starts out with some stunning visuals from 2006 of NASA’s New Horizons Pluto mission launching from Cape Canaveral. Throughout the opening tour of the Solar System, we can hear the voice of Venetia Burney as she is interviewed by NASA Public Affairs officer Edward Goldstein during the launch.
When Goldstein asks whether she had ever seen Pluto through a telescope, the clear and articulate voice of Venetia replies, “I don’t think I have. I’ve just seen a photograph.” And so the journey begins, where Venetia explains her fascination with Pluto and a number of experts (including the enigmatic Sir Patrick Moore) help to explain the facts behind the discovery of Pluto to the scientific endeavour of the search for “Planet X”.
One of the key moments is when Venetia is describing when she decided on the name for the heavenly body. At age 11, had an acute interest in ancient mythology, so she chose the name because Pluto is the Roman god of the underworld; a fitting name considering the cold, dark nature of Pluto’s 248 year orbit. In a fortuitous chain of events, her grandfather, a former librarian of Oxford University’s Bodleian Library, passed the suggestion via letter to Professor Herbert Hall Turner saying that his granddaughter had chosen a “thoroughly suitable name: PLUTO.” Hall Turner, thrilled with the candidate name, sent Venetia’s idea to colleagues in the USA, at the Lowell Observatory.
Pouring a cup of tea, Venetia recounts that historic day in 1930. “It was about 8 o’clock and I was having breakfast with my mother and my grandfather,” she says very matter of factually. “My grandfather, as usual, opened the paper, The Times, and in it he read that a new planet had been discovered. He wondered what it should be called. We all wondered. And then I said, “why not call it Pluto?” And the whole thing stemmed from that.”
A special delight is when Venetia visits St. Anne’s Primary School in Surrey to participate in their class project all about Pluto. It goes to show that even young school children have fallen under Pluto’s spell. One 9 year-old pupil, Katie, shares her concerns about Pluto’s demotion, “Some people say that Pluto isn’t a real planet, so I’m looking forward to Venetia coming because I want to find out if that’s true.”
Legendary astronomer Sir Patrick Moore enthusiastically gives his views on Pluto too, having co-authored a 1980 book with discoverer Tombaugh called Out of the Darkness: The Planet Pluto, he is the ideal character to defend the demotion from planet to dwarf planet by the IAU saying, “It’s not demoted! […] you can call it whatever you like. It’s there!” I have been a huge fan of Sir Patrick’s writing, and his regular BBC program The Sky at Night is essential astronomy watching, and has been for the last 50 years!
Other guests on the film uncover the various attributes of Pluto’s discovery, delving into the history and future of the planetary lightweight on the outermost reaches of the Solar System.
The Naming Pluto adventure culminates in 2006 when Venetia and Sir Patrick meet (for the second time) at his West Sussex home to make an attempt at observing Pluto through the telescope in his garden. Patrick was overjoyed to see Venetia again and chuckles as he introduces her to the camera crew, “The lady who named Pluto!”
“Yes, indeed,” the ever gracious Venetia replies, smiling.
Unfortunately, the UK summer weather conspired against the possibility of clear skies, and any chance of Patrick’s 15″ reflector of spying Pluto was lost. However, there is a fantastic twist in the tale, bringing the whole film to a wonderfully emotional ending.
All in all, Naming Pluto is a fabulous tribute, not only to Venetia, but to the astronomical process. Although Pluto has undergone a change in status these last few years, it remains an important, permanent feature of the Solar System. This well-crafted story gives the viewer an excellent overview of Pluto’s discovery, naming and the magic it holds today for the 9 year-olds at St. Anne’s to Venetia who named the planet nearly 80 years ago…
For more information about Pluto, check out the Guide to Space: Pluto »
A big thank you goes to writer, director and producer Ginita Jimenez for sharing this magnificent production with me. My copy will have pride of place with my growing collection of space science DVDs, a timeless memento of a historic time for astronomy.
If you want your own copy, or want to buy it as a gift, contact Ginita at: [email protected]
Naming Pluto is currently on the international film festival circuit so if you’d prefer watching it on the big screen, and are in the area, please see below. There will also be a blog and updates on www.fatherfilms.com.
THROUGH WOMEN’S EYES – USA
30TH & 31ST JANUARY 2009
JAIPUR INTERNATIONAL FILM FESTIVAL – INDIA
SEBASTOPOL DOCUMENTARY FILM FESTIVAL – USA
MARCH 6-8, 2009
CINEQUEST FILM FESTIVAL – USA
FEB 25-MAR 08 2009
OFFICIAL SELECTION FOR BEST SHORT FILM AWARD
Details of the film:
Title: Naming Pluto
DVD: 16:9 (FHA) (Colour)
Audio: Stereo & 5.1 Dolby
All images and media used in this review are copyrighted to Father Films 2008. All rights reserved www.fatherfilms.com. | 0.889309 | 3.325602 |
On 14 July 2015, New Horizons conducted a flyby of the planet, collecting incredible amounts of data that will take 16 months to return to Earth. The first data alone has totally changed what we previously believed about the remote planet.
What will we learn from Pluto?
is named after the Roman god of the underworld
New Horizons has captivated the imaginations of people around the world. The images being beamed back to Earth from the dwarf planet at the outer reaches of our solar system have us enthralled. While we’re anxiously awaiting news of the next data returned. What do we hope to find? Why is Pluto so fascinating? What is next on the great quest of space exploration?
Scientists at the University of Tasmania are studying their own newly gathered data on Pluto, data that is unique.
Pluto is not like other planets in the solar system. It has a very unusual orbit. Instead of orbiting at a nearly constant distance from the Sun, Pluto’s orbit is egg shaped and tilted. The elliptical orbit takes the dwarf planet nearer the sun than Neptune for part of the 248 years of its orbit and further away for the rest. This means that its temperature would be changing radically, with extreme seasonal variations. The tilt away from the rest of the Solar System suggests that Pluto may have formed quite differently than the more well-known, larger planets.
The greatest questions of astrophysics
Dr Andrew Cole, an Astrophysicist and Senior Lecturer at the University of Tasmania, studies the evolution of the Universe from the Big Bang to today. He uses the world’s largest ground-based and space telescopes to capture information that will help us answer the greatest questions of all – how did we get here and what is the future of our Universe?
Each bit of data we collect adds to our understanding. We can’t replicate the time scales or energies of space in a lab, so we have to collect data from space itself. But every time a probe goes past a planet or an asteroid or a comet and collects data, it raises more questions than it answers. There is never a time when we can imagine knowing everything that we need to know.
Dr Cole has been working with an international team of approximately two-dozen astronomers from France, Brazil, and the United States, to collect data on Pluto using Tasmania’s Greenhill Observatory.
Pluto recently passed in front of a background star. By analysing the distortion of the light of the background star we can answer questions about Pluto’s atmosphere.
Because the alignment between Pluto and the background star had to be extremely precise, it could only be seen from a narrow strip on the Earth’s surface, which included Tasmania and the South Island of New Zealand.
“Our results were critical,” said Dr Cole, “and we have a unique perspective in this experiment. We had multiple requests for the type of data we would collect. We promised to use our telescope for one experiment with a visible light filter and then another consortium asked to use an infrared camera.”
We didn’t have the capability to do both at the same time, but being physicists, loving problem solving, we thought... we could do that if we built a mirror that splits the light and sends the infrared one way and the visible light the other. And it worked.
“As far as I know we’re the only place that recorded this event both in the optical/visible light and in the infrared. So if the sky is blue on Pluto we’ll be able to tell, just by comparing the images together.”
A new picture of Pluto
The University of Tasmania researchers and their collaborators are still analysing the data to work out what it tells us, but Dr Cole says it’s clear that Pluto has a more active atmosphere than scientists might have guessed.
Because of the extreme variation in temperatures on Pluto, its possible that there is weather happening.
on Earth pass in the time it takes Pluto to orbit the Sun once.
“One prediction is that maybe the atmosphere freezes out, that it all turns into methane snow and condenses forming snow caps at the poles, like dry ice. At other times it will become a gas and be part of the atmosphere.”
“If the atmosphere is condensing out is it forming clouds? Is the atmosphere clear or hazy? By making very careful measurements, we can start to answer these questions,” said Dr Cole.
It's not the first time that Tasmanian researchers have played a role in important discoveries regarding Pluto. In fact, Tasmania’s telescope was used in a similar experiment in the mid 80s to confirm the original discovery of Pluto’s atmosphere.
“A NASA mission that involved flying a telescope very high in the atmosphere on a specially modified aircraft, obtained evidence that maybe Pluto had an atmosphere. The scientific community was sceptical. Using the same trick of waiting until Pluto passes in front of a background star, Tasmanian researchers were able to confirm NASA’s discovery.”
What can we learn from New Horizons?
on Pluto has the same intensity as moonlight on Earth.
Dr Cole is also looking forward to getting his hands on the data from New Horizons.
“I’m most excited about what the results will tell us about the big picture. There are a lot of things that we don’t understand about how planetary systems form. Anything that we can add to the picture helps,” he said.
For example, how do icy small objects very far from stars actually come together, how do they form and last for 4.5 billion years?
“I’m most interested in the interior composition of Pluto, how old its surface might be, and whether internal processes or impacts during the history of the solar system have been the most important factors in shaping it.”
Deepening our understanding of the universe.
Learning how planets form, whether they are common or rare, can help to inform our understanding of the evolution of the Universe.
“What were the odds that the Earth formed around the Sun? Are there planets like Earth all over the place or is it extremely unusual?”
The first data from New Horizons has already thrown what we thought we understood about Pluto into question.
Pluto is a dwarf planet - like a moon with no parent planet - so it was expected to be geologically dead. Images from New Horizons show evidence of processes that have formed mountains. This tells us that there is a little bit of extra energy in the system that nobody has thought of.
Pluto was reclassified from a planet to a dwarf planet.
“There is still a piece of the puzzle missing. We don’t know if those mountains are relatively recent, if they are left over from the formation of Pluto or if there was some heating event that happened at some point, like from a massive collision with another object. It’s just a mystery at this point.”
After Pluto, what’s next?
Dr Cole says there are thousands of other similar sized objects, dwarf planets and the like, yet to be explored in our solar system.
“Pluto is just the tip of the iceberg,” he said. NASA plans to send the New Horizons spacecraft past one of the Solar System’s smaller icy dwarf planets on its way out of the Solar System, but the exact path has not yet been finalised.
“As for promising targets for future missions? The most common planets to find in the universe are similar to Neptune, maybe 15-20 times the size of the earth and probably a bit icy. So exploring these ice giant planets has become a pretty big priority for scientists right now.”
Banner images: http://www.nasa.gov
Interested in conducting your own research? Apply now to become a research student.
About About Dr. Andrew Cole
Dr Andrew Cole is a Senior Lecturer in Physics and Astronomy and the Director of the Greenhill Observatory, the home of UTAS optical astronomy research infrastructure. Andrew's research specialisation is in the area of stellar populations: using the statistics of the distribution, motion, and chemistry of stars to learn about the structure, history and physical processes that shape galactic systems, including our own Milky Way. He uses the UTAS 1.3-metre Harlingten telescope to search for exoplanets around stars in the direction towards the centre of the Milky Way by analysis of gravitational microlensing light curves.View About Dr. Andrew Cole's full researcher profile | 0.925286 | 3.797999 |
Science, Tech, Math › Science An Introduction to Black Holes Share Flipboard Email Print APRIL 10: In this handout photo provided by the National Science Foundation, the Event Horizon Telescope captures a black hole at the center of galaxy M87, outlined by emission from hot gas swirling around it under the influence of strong gravity near its event horizon, in an image released on April 10, 2019. A network of eight radio observatories on six mountains and four continents, the EHT observed a black hole in Messier 87, a supergiant elliptical galaxy in the constellation Virgo, on and off for 10 days in April of 2017 to make the image. National Science Foundation / Getty Images Science Astronomy Stars, Planets, and Galaxies An Introduction to Astronomy Important Astronomers Solar System Space Exploration Chemistry Biology Physics Geology Weather & Climate By John P. Millis, Ph.D Professor of Physics and Astronomy Ph.D., Physics and Astronomy, Purdue University B.S., Physics, Purdue University our editorial process John P. Millis, Ph.D Updated January 10, 2020 Black holes are objects in the universe with so much mass trapped inside their boundaries that they have incredibly strong gravitational fields. In fact, the gravitational force of a black hole is so strong that nothing can escape once it has gone inside. Not even light can escape a black hole, it is trapped inside along with stars, gas, and dust. Most black holes contain many times the mass of our Sun and the heaviest ones can have millions of solar masses. This computer-simulated image shows a supermassive black hole at the core of a galaxy. The black region in the center represents the black hole's event horizon, where no light can escape the massive object's gravitational grip. The black hole's powerful gravity distorts space around it like a funhouse mirror. Light from background stars is stretched and smeared as the stars skim by the black hole. NASA, ESA, and D. Coe, J. Anderson, and R. van der Marel (Space Telescope Science Institute), Science Credit: NASA, ESA, C.-P. Ma (University of California, Berkeley), and J. Thomas (Max Planck Institute for Extraterrestrial Physics, Garching, Germany). Despite all that mass, the actual singularity that forms the core of the black hole has never been seen or imaged. It is, as the word suggests, a tiny point in space, but it has a LOT of mass. Astronomers are only able to study these objects through their effect on the material that surrounds them. The material around the black hole forms a rotating disk that lies just beyond a region called "the event horizon," which is the gravitational point of no return. The Structure of a Black Hole The basic "building block" of the black hole is the singularity: a pinpoint region of space that contains all the mass of the black hole. Around it is a region of space from which light cannot escape, giving the "black hole" its name. The outer "edge" of this region is what forms the event horizon. It's the invisible boundary where the pull of the gravitational field is equal to the speed of light. It's also where gravity and light speed are balanced. The event horizon's position depends on the gravitational pull of the black hole. Astronomers calculate the location of an event horizon around a black hole using the equation Rs = 2GM/c2. R is the radius of the singularity, G is the force of gravity, M is the mass, c is the speed of light. Black Hole Types and How They Form There are different types of black holes, and they come about in different ways. The most common type is known as a stellar-mass black hole. These contain roughly up to a few times the mass of our Sun, and form when large main sequence stars (10 - 15 times the mass of our Sun) run out of nuclear fuel in their cores. The result is a massive supernova explosion that blasts the stars outer layers to space. What's left behind collapses to create a black hole. An artist's conception of a stellar-mass black hole (in blue) hat likely formed when a supermassive star collapsed, feeding from material ejected by a nearby star. ESA, NASA and Felix Mirabel) The two other types of black holes are supermassive black holes (SMBH) and micro black holes. A single SMBH can contain the mass of millions or billions of suns. Micro black holes are, as their name implies, very tiny. They might have perhaps only 20 micrograms of mass. In both cases, the mechanisms for their creation are not entirely clear. Micro black holes exist in theory but have not been directly detected. Supermassive black holes are found to exist in the cores of most galaxies and their origins are still hotly debated. It's possible that supermassive black holes are the result of a merger between smaller, stellar-mass black holes and other matter. Some astronomers suggest that they might be created when a single highly massive (hundreds of times the mass of the Sun) star collapses. Either way, they are massive enough to affect the galaxy in many ways, ranging from effects on starbirth rates to the orbits of stars and material in their near vicinity. Many galaxies have supermassive black holes at their cores. If they are actively "eating", then they give off huge jets and are known as active galactic nuclei. NASA/JPL-Caltech Micro black holes, on the other hand, could be created during the collision of two very high-energy particles. Scientists suggest this happens continuously in the upper atmosphere of Earth and is likely to happen during particle physics experiments at such places as CERN. How Scientists Measure Black Holes Since light can not escape from the region around a black hole affected by the event horizon, nobody can really "see" a black hole. However, astronomers can measure and characterize them by the effects they have on their surroundings. Black holes that are near other objects exert a gravitational effect on them. For one thing, mass can also be determined by the orbit of material around the black hole. A model of a black hole surrounded by heated ionized) material. This may be what the black hole in the Milky Way "looks" like. Brandon DeFrise Carter, CC0, Wikimedia. In practice, astronomers deduce the presence of the black hole by studying how light behaves around it. Black holes, like all massive objects, have enough gravitational pull to bend light's path as it passes by. As stars behind the black hole move relative to it, the light emitted by them will appear distorted, or the stars will appear to move in an unusual way. From this information, the position and mass of the black hole can be determined. This is especially apparent in galaxy clusters where the combined mass of the clusters, their dark matter, and their black holes create oddly-shaped arcs and rings by bending the light of more distant objects as it passes by. Astronomers can also see black holes by the radiation the heated material around them gives off, such as radio or x rays. The speed of that material also gives important clues to the characteristics of the black hole it's trying to escape. Hawking Radiation The final way that astronomers could possibly detect a black hole is through a mechanism known as Hawking radiation. Named for the famed theoretical physicist and cosmologist Stephen Hawking, Hawking radiation is a consequence of thermodynamics that requires that energy escape from a black hole. The basic idea is that, due to natural interactions and fluctuations in the vacuum, the matter will be created in the form of an electron and anti-electron (called a positron). When this occurs near the event horizon, one particle will be ejected away from the black hole, while the other will fall into the gravitational well. To an observer, all that is "seen" is a particle being emitted from the black hole. The particle would be seen as having positive energy. This means, by symmetry, that the particle that fell into the black hole would have negative energy. The result is that as a black hole ages, it loses energy, and therefore loses mass (by Einstein's famous equation, E=MC2, where E=energy, M=mass, and C is the speed of light). Edited and updated by Carolyn Collins Petersen. | 0.901201 | 3.645773 |
Can the Magnetic Field of Rosetta’s Comet Tell Us How the Outer Solar System Formed?
The European Space Agency’s Rosetta mission, which was the first mission to involve a spacecraft following a comet on its journey around the Sun, and placing a lander on its surface, has found clues about how magnetic fields may have helped the Solar System to form.
The Rosetta orbiter, along with its lander, Philae, measured the magnetic field of the comet 67P/ Churyumov-Gerasimenko. Scientists from the Department of Earth, Atmospheric and Planetary Sciences at the Massachusetts Institute of Technology, USA, and the Technische Universität Braunschweig, Germany, studied the Rosetta data and found that the comet has a weak magnetic field. John Biersteker, a planetary science PhD candidate at MIT and lead author of the research, says that, “Our work is consistent with theories of magnetically driven evolution of protoplanetary disks, the first time this has been tested in the outer solar system.” The study was published in The Astrophysical Journal.
“The magnetic field in our protoplanetary disk is thought to have played a key role in accreting gas and dust onto the young Sun,” explains James Bryson, who is a planetary scientist in the Department of Earth Sciences at the University of Cambridge and who was not involved in the Biersteker study. “This field effectively acts like a spring that allows different parcels of gas in the disk to communicate with each other efficiently. If a parcel of gas next to the Sun is accreted onto the Sun, the disk field effectively pulls on a neighboring parcel, which means gas is accreted onto the Sun at a higher rate than if the disk field didn’t exist. This field can therefore explain the rate at which we observe the accretion of gas onto other Sun-like stars.”
Adds Biersteker, “We are interested in magnetic records from the first several million years of the Solar System because magnetic fields have been proposed to play an important role in the evolution of protoplanetary disks, including the one that formed the Solar System.”
Magnetism in planet-formation
About 4.6 billion years ago, the Solar System began to form as a swirling cloud of gas and dust, but then collapsed inward while flattening to create a rotating disk. Smaller particles within the disk clumped together to create larger bodies, which eventually formed the planets, moons, asteroids, comets and meteoroids. Studies of meteorites tell us that some of the dust in that early, swirling cloud may have consisted of iron and other magnetic particles. Scientists are asking if those particles experienced magnetic fields within the protoplanetary disk, and if so, whether these fields helped align the particles as they clumped together. However, studies of the magnetism in meteorites have been mainly limited to giving us information about only the inner Solar System.
Observations of comets like 67P can tell us more about how the outer Solar System formed. Like some of the other comets, 67P is thought to have come from the Kuiper Belt, outside the orbit of Neptune. Later, 67P traveled closer to Jupiter, whose gravity then pulled 67P into a 6.5-year-long orbit, closer to the Sun.
Because comets are small and formed far away from the Sun, they are thought to have changed very little since they were assembled. Comets are made of frozen water and carbon dioxide, along with dust and some organic materials. Astronomers think that they were left over from the materials that formed the infant Solar System, after the primordial gas and dust cloud collapsed and the planets, moons and asteroids formed.
According to data from the Rosetta mission, studies of 67P’s water and gases show that the comet probably formed in a very cold region, far from the Sun.
“67P is a treasure trove of information about the early Solar System,” says Biersteker. “Because 67P has been in cold storage for nearly the entire lifetime of the Solar System, it provides a unique record of conditions during the formation of planetesimals in the outer Solar System. No other record of the outer Solar System is currently available.”
To measure 67P’s magnetic field, Rosetta’s orbiter carried a magnetometer (Plasma Consortium Magnetometer, or RPC-MAG), and Philae, the lander, carried the Rosetta Lander Magnetometer and Plasma Monitor (ROMAP). When Philae attempted to land on 67P in November 2014, it bounced off the surface twice before coming to rest. However, as Philae bounced, ROMAP took several measurements of the comet’s magnetic field, both on its surface and just above, while RPC-MAG measured the magnetic field further away, at an altitude of about 17 kilometers above the surface.
Hans-Ulrich Auster and Philip Heinisch, scientists at the Institute for Geophysics and Extraterrestrial Physics at the Universität Braunschweig in Braunschweig, Germany, studied the ROMAP and RPC-MAG data along with the early Philae trajectory data and found that the comet had a very weak magnetic field. Later, the team used the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) instrument on the orbiter to obtain high resolution images of the comet with which they could simulate 67P’s precise shape, so that they could better estimate the maximum strength of the comet’s magnetic field.
“The reason for the approximations in [Auster and Heinisch’s] studies is that Philae’s landing did not go as planned, and the lander was initially lost!” says Biersteker. “Philae bounced across the surface of the comet instead of coming to rest at its intended landing spot.” However, as he explains further, “As it turned out, this was very fortunate for us, because it allowed the magnetometer to collect data over a large region of the comet instead of only at one location. But it meant that only after carefully reconstructing Philae’s trajectory could we combine the magnetic data with our knowledge of the comet’s shape. The upper limits on the strength of the magnetic field are compatible with theories where magnetic fields play an important role in controlling the evolution of the disk which formed the solar system. These are consistent with the required magnetic field strength from theoretical models of disk evolution.”
Biersteker concludes, “Our research comes at an exciting time for this field. Magnetic measurement techniques for meteorites are improving and new meteorites are always being examined, so that we may be able to start to piece together the large scale magnetic structure of the disk that formed the Solar System, both as a function of distance from the nascent Sun and possibly as a function of time.” He adds that “Astronomical measurements by instruments like ALMA, the Atacama Large Millimeter/submillimeter Array, are finally reaching the precision and resolution where we may be able to observe these magnetic fields in other planetary systems as they form.”
The work was supported through NASA’s Emerging Worlds Program. NASA Astrobiology provides resources for this and other Research and Analysis programs within the NASA Science Mission Directorate (SMD) that solicit proposals relevant to astrobiology research. It was also funded by the U.S. Rosetta program (CREI 1576768), and philanthropist Thomas F. Peterson Jr. | 0.875844 | 4.056464 |
Last year’s ESA-sponsored medical doctor at Concordia has been working on his videos and shared this project of charting the Sun over his year-stay in Antarctica:
Wouldn’t it be interesting to keep a log of your location at exactly 16:00 every week? Let’s do that on Mondays: imagine drawing a dot on a map to indicate your position at the same time every week. At the end of a calendar year you would pick up the map and most Mondays at 16:00 you would probably be at the same place – at work! But there would most likely be some deviation. Perhaps one Monday at 16:00 sharp you were at the office next door or you had to get up from your chair and cross the corridor to answer the door. Maybe one Monday you left early, so your location indicator showed you at home or maybe you took a free day, so your dot on the map was far away, at the the nearest beach. How would it look, that graph of your exact position at 16:00 every Monday for a whole year?
Well, you can do this with a star to answer that the same question: our Sun! As seen from the surface of the Earth, the position of the Sun in the sky changes with seasons. The reason for this is that our planet’s rotational axis has a 23˚ inclination with relation to the ecliptic (the plane on which all planets revolve around the Sun) plus the Earth’s orbit around the Sun is an ellipse, not a circle. This means that at exactly the same time, the Sun will be at a slightly different place in the sky next Monday as compared to this Monday. A snapshot of the Sun’s positions at the same moment over a whole year is called an “analemma”. Now the difference between an analemma and your own “graph of location at 16:00 on Mondays” is that the Sun is far more predictable! It follows the same path in the sky with no deviation year after year. This pattern looks like a figure of 8, only it is tilted and one of its lobes appears larger than the other. You can have a look at analemma pictures here and here.
What does change though is how you see the analemma – and that depends solely on your geographic latitude: A yearly analemma over Athens is slightly different compared to an analemma over Paris or Rome even if taken at the same time of day. The main change is how much the figure-8 shape tilts and how high above the horizon the analemma appears. So how would it look from, say, Sydney? Well, about the same as from Athens, since their latitudes are almost opposite. But how would it look from an extremity such as the North or South Pole?
Having spent a whole year at Concordia research station in Antarctica, and since my location at 16:00 every Monday during my stay would hardly change, I decided to step up to the challenge of documenting the analemma. To achieve that, I took a photo of the Sun with a special filter at the exact same time every week and from the exact same spot outside the station which was particularly challenging with the winds and low temperatures outside. Still, the result was rewarding as to my knowledge it is the first-ever capture of the analemma from within the Antarctic Circle. As you can see, near the poles only one lobe of the analemma is visible (at Concordia we experience a 3-month-long polar night where the Sun disappears completely from view) and the shape is almost vertical.
Wait… one last question: how would an analemma look like from the surface of another planet, for example Mars? Well have a look: https://apod.nasa.gov/apod/ap061230.html !
Our solar system is full of marvels. ҉ | 0.825618 | 3.362822 |
Moon ♏ Scorpio
Moon phase on 23 October 2014 Thursday is New Moon, 1 day young Moon is in Libra.Share this page: twitter facebook linkedin
Moon rises at sunrise and sets at sunset. It's part facing the Earth is completely in shadow.
Moon is passing about ∠25° of ♎ Libra tropical zodiac sector.
Lunar disc is not visible from Earth. Moon and Sun apparent angular diameters are ∠1818" and ∠1929".
Next Full Moon is the Beaver Moon of November 2014 after 14 days on 6 November 2014 at 22:23.
There is high New Moon ocean tide on this date. Combined Sun and Moon gravitational tidal force working on Earth is strong, because of the Sun-Moon-Earth syzygy alignment.
At 21:57 on this date the Moon completes the old and enters a new synodic month with lunation 183 of Meeus index or 1136 from Brown series.
29 days, 14 hours and 36 minutes is the length of new lunation 183. It is 1 hour and 32 minutes longer than next lunation 184 length.
Length of current synodic month is 1 hour and 52 minutes longer than the mean length of synodic month, but it is still 5 hours and 11 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠252.3°. At the beginning of next synodic month true anomaly will be ∠289.3°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
5 days after point of apogee on 18 October 2014 at 06:05 in ♌ Leo. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 10 days, until it get to the point of next perigee on 3 November 2014 at 00:21 in ♓ Pisces.
Moon is 394 236 km (244 967 mi) away from Earth on this date. Moon moves closer next 10 days until perigee, when Earth-Moon distance will reach 367 871 km (228 584 mi).
Moon is in ascending node in ♎ Libra at 00:46 on this date, it crosses the ecliptic from South to North. Moon will follow the northern part of its orbit for the next 12 days to meet descending node on 5 November 2014 at 03:13 in ♈ Aries.
At 00:46 on this date the Moon is completing its previous draconic month and is entering the new one.
9 days after previous North standstill on 13 October 2014 at 13:34 in ♊ Gemini, when Moon has reached northern declination of ∠18.517°. Next 4 days the lunar orbit moves southward to face South declination of ∠-18.539° in the next southern standstill on 28 October 2014 at 01:03 in ♐ Sagittarius.
The Moon is in New Moon geocentric conjunction with the Sun on this date and this alignment forms Sun-Moon-Earth syzygy. | 0.837327 | 3.021011 |
The color-magnitude diagram and the main-sequence luminosity function of the globular cluster M13 have been investigated. While those clusters observed by the Hubble Space Telescope (HST) show a shallow luminosity function for low-mass stars, M13 has been known to have a very steep gradient toward the faint end. To understand this seemingly unique characteristic of M13, we carried out deep BV CCD observations. The observed field of nearly 56 arcmin2 is located approximately 12′ from the cluster center. Our (B- V)-V color-magnitude diagram has the main sequence extended to the detection limit at V ≈24.5 mag. It is apparent that there is a significant population of unexpected field stars below V ≈ 22.5, which cannot be accounted for by photometric errors. When these field stars are eliminated, the derived luminosity function of M13 shows a much shallower slope at the faint end, just like other Galactic globular clusters studied by HST observations.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science | 0.875148 | 3.544958 |
A star is a massive, compact plasma body in outer space that is currently producing or has produced energy through nuclear fusion. The most familiar and closest star to the Earth is the Sun. Unlike a planet, from which most light is reflected, a star shines because of its intense heat. Stellar astronomy is the study of stars. Every star known to humans has either a name or a systematic name, while most of the stars have Bayer designations.
Individual stars differ from each other due to their total mass, their composition, and their age. The total mass determines the course of evolution of a star, as well as its eventual fate. A Hertzsprung-Russell diagram shows the pattern of the temperature of stars against their absolute magnitude, and can be used to determine the overall age of a star and the stage in its evolution. Initially, stars are composed primarily of hydrogen, with some helium and heavier trace elements that determine the metallicity of a star. Over the course of a star's evolution, a portion of the hydrogen is converted into heavier elements through the process of nuclear fusion. Part of the matter is then recycled back into the interstellar environment, where it is used to form a new generation of more metal-rich stars.
Multi-star systems consist of two or more stars that are gravitationally bound, and generally move around each other in stable orbits. When two such stars have a relatively close orbit, their gravitational interaction can have a significant impact on their evolution. For example, a nova occurs when a white dwarf accretes matter from a companion star. | 0.911544 | 3.439028 |
Hot Jupiter loops around far away star
Out of kilter Astronomers have found a hot bloated planet, twice as big as Jupiter, which is circling its star in a rare polar orbit.
The discovery, reported in the Astrophysical Journal Letters, raises new questions about how planets form and move through their solar system.
Planets usually orbit in the same plane and direction as their host star's rotation, according to the study's lead author Brett Addison of the University of New South Wales.
"A polar orbit is quite unusual. This is something that you wouldn't really expect according to planet formation models," says Addison.
Planets are believed to form in proto-planetary discs of dust rotating around a newly formed star's equator, and in the same direction as the star's spin.
In the case of our own solar system, that alignment is within six degrees of the Sun's equator.
However, the off-centre polar orbit of the planet WASP-79b is at an angle of about 106 degrees.
The planet belongs to a group of worlds known as hot Jupiters, large gas giants that orbit extremely close to their host stars. WASP-79b takes just three-and-a-half days to orbit its star.
"It's a fairly average star, about 700 light years away, slightly larger and more massive than the Sun," says Addison.
Of the 850 extra-solar planets so far confirmed, less than a dozen are known to be in polar orbits.
The unusual orbit was detected by Addison and colleagues using the Anglo-Australian Telescope. They measured changes in the light spectrum coming from the star as the planet crossed in front of it.
"As the planet crosses in front of the star, it distorts the absorption lines in the stars spectrum, and from those distortions we can determine the relative alignment or the orbit between the stars spin axis and the planet," says Addison.
Systems with spin-orbit misalignments tend to involve stars that are hotter than the Sun.
"Unlike cooler stars that have thick convective layers, the convective layer in hot stars like WASP-79a may be too thin to effectively align the planet's orbital plane over short time scales," says Addison.
Another possibility could involve the gravitational influence of another planet or star in the system.
"WASP-79b most likely migrated inwards, it didn't form where it is now, and in the process of migrating somehow its orbit became misaligned and went into a polar orbit," says Addison.
A cool red dwarf star or an even cooler failed star known as a brown dwarf are possible candidates.
"The next step is to test theories on how planetary migration can lead to misalignments and polar or even retrograde orbits," says Addison. | 0.857701 | 3.985823 |
NASA’s Mars Odyssey space probe begins to map the surface of Mars using its thermal emission imaging system.
Artist's impression of the Mars Odyssey spacecraft
|Mission type||Mars orbiter|
|Operator||NASA / JPL|
19 years, 1 month and 19 days from launch
18 years, 7 months and 2 days at Mars (6607 sols)
En route: 6 months, 17 days
Primary mission: 32 months (1007 sols)
Extended mission: 15 years, 9 months and 1 day (5599 sols) elapsed
|Launch mass||758 kilograms (1,671 lb)|
|Dry mass||376.3 kilograms (830 lb)|
|Start of mission|
|Launch date||7 April 2001, 15:02:22UTC|
|Rocket||Delta II 7925-9.5|
|Launch site||Cape Canaveral SLC-17A|
|Semi-major axis||3,793.4 km (2,357.1 mi)|
|Periareion altitude||400 km (250 mi)|
|Apoareion altitude||400 km (250 mi)|
|Epoch||19 October 2002|
|Orbital insertion||24 October 2001, 02:18:00 UTC|
MSD 45435 12:21 AMT
2001 Mars Odyssey is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectrometers and a thermal imager to detect evidence of past or present water and ice, as well as study the planet's geology and radiation environment. It is hoped that the data Odyssey obtains will help answer the question of whether life existed on Mars and create a risk-assessment of the radiation that future astronauts on Mars might experience. It also acts as a relay for communications between the Mars Science Laboratory, and previously the Mars Exploration Rovers and Phoenix lander, to Earth. The mission was named as a tribute to Arthur C. Clarke, evoking the name of 2001: A Space Odyssey.
By December 15, 2010, it broke the record for longest serving spacecraft at Mars, with 3,340 days of operation. As of 2019 October it is in a polar orbit around Mars with a semi-major axis of about 3,800 km or 2,400 miles. It has enough propellant to function until 2025.
On May 28, 2002 (sol 210), NASA reported that Odyssey's GRS instrument had detected large amounts of hydrogen, a sign that there must be ice lying within a meter of the planet's surface, and proceeded to map the distribution of water below the shallow surface. The orbiter also discovered vast deposits of bulk water ice near the surface of equatorial regions.
Odyssey has also served as the primary means of communications for NASA's Mars surface explorers in the past decade, up to the Curiosity rover. By December 15, 2010, it broke the record for longest serving spacecraft at Mars, with 3,340 days of operation, claiming the title from NASA's Mars Global Surveyor. It currently holds the record for the longest-surviving continually active spacecraft in orbit around a planet other than Earth, ahead of the Pioneer Venus Orbiter (served 14 years) and the Mars Express (serving over 14 years), at 18 years, 7 months and 2 days.
In August 2000, NASA solicited candidate names for the mission. Out of 200 names submitted, the committee chose Astrobiological Reconnaissance and Elemental Surveyor, abbreviated ARES (a tribute to Ares, the Greek god of war). Faced with criticism that this name was not very compelling, and too aggressive, the naming committee reconvened. The candidate name "2001 Mars Odyssey" had earlier been rejected because of copyright and trademark concerns. However, NASA e-mailed Arthur C. Clarke in Sri Lanka, who responded that he would be delighted to have the mission named after his books, and he had no objections. On September 20, NASA associate administrator Ed Weiler wrote to the associate administrator for public affairs recommending a name change from ARES to 2001 Mars Odyssey. Peggy Wilhide then approved the name change.
The three primary instruments Odyssey uses are the:
- Thermal Emission Imaging System (THEMIS).
- Gamma Ray Spectrometer (GRS), includes the High Energy Neutron Detector (HEND), provided by Russia. GRS is a collaboration between University of Arizona's Lunar and Planetary Lab., the Los Alamos National Laboratory, and Russia's Space Research Institute.
- Mars Radiation Environment Experiment (MARIE).
Mars Odyssey launched from Cape Canaveral on April 7, 2001, and arrived at Mars about 200 days later on October 24. The spacecraft's main engine fired in order to decelerate, which allowed it to be captured into orbit around Mars. Odyssey then spent about three months aerobraking, using friction from the upper reaches of the Martian atmosphere to gradually slow down and reduce and circularize its orbit. By using the atmosphere of Mars to slow the spacecraft in its orbit rather than firing its engine or thrusters, Odyssey was able to save more than 200 kilograms (440 lb) of propellant. This reduction in spacecraft weight allowed the mission to be launched on a Delta II 7925 launch vehicle, rather than a larger, more expensive launcher.
Aerobraking ended in January 2002, and Odyssey began its science mapping mission on February 19, 2002. Odyssey's original, nominal mission lasted until August 2004, but repeated mission extensions have kept the mission active.
About 85% of images and other data from NASA's twin Mars Exploration Rovers, Spirit and Opportunity, have reached Earth via communications relay by Odyssey. The orbiter helped analyze potential landing sites for the rovers and performed the same task for NASA's Phoenix mission, which landed on Mars in May 2008. Odyssey aided NASA's Mars Reconnaissance Orbiter, which reached Mars in March 2006, by monitoring atmospheric conditions during months when the newly arrived orbiter used aerobraking to alter its orbit into the desired shape.
Odyssey is in a Sun-synchronous orbit, which provides consistent lighting for its photographs. On September 30, 2008 (sol 2465) the spacecraft altered its orbit to gain better sensitivity for its infrared mapping of Martian minerals. The new orbit eliminated the use of the gamma ray detector, due to the potential for overheating the instrument at the new orbit.
The payload's MARIE radiation experiment stopped taking measurements after a large solar event bombarded the Odyssey spacecraft on October 28, 2003. Engineers believe the most likely cause is that a computer chip was damaged by a solar particle smashing into the MARIE computer board.
The orbiter's orientation is controlled by a set of three reaction wheels and a spare. When one failed in June 2012, the fourth was spun up and successfully brought into service. Since July 2012, Odyssey has been back in full, nominal operation mode following three weeks of 'safe' mode on remote maintenance.
On February 11, 2014, mission control accelerated Odyssey's drift toward a morning-daylight orbit to "enable observation of changing ground temperatures after sunrise and after sunset in thousands of places on Mars". The orbital change occurred gradually until November 2015. Those observations could yield insight about the composition of the ground and about temperature-driven processes, such as warm seasonal flows observed on some slopes, and geysers fed by spring thawing of carbon dioxide (CO2) ice near Mars' poles.
Water on Mars
By 2008, Mars Odyssey had mapped the basic distribution of water below the shallow surface. The ground truth for its measurements came on July 31, 2008, when NASA announced that the Phoenix lander confirmed the presence of water on Mars, as predicted in 2002 based on data from the Odyssey orbiter. The science team is trying to determine whether the water ice ever thaws enough to be available for microscopic life, and if carbon-containing chemicals and other raw materials for life are present.
The orbiter also discovered vast deposits of bulk water ice near the surface of equatorial regions. Evidence for equatorial hydration is both morphological and compositional and is seen at both the Medusae Fossae formation and the Tharsis Montes.
Odyssey and Curiosity
Mars Odyssey's THEMIS instrument was used to help select a landing site for the Mars Science Laboratory (MSL). Several days before MSL's landing in August 2012, Odyssey's orbit was altered to ensure that it would be able to capture signals from the rover during its first few minutes on the Martian surface. Odyssey also acts as a relay for UHF radio signals from the (MSL) rover Curiosity. Because Odyssey is in a Sun-synchronous orbit, it consistently passes over Curiosity's location at the same two times every day, allowing for convenient scheduling of contact with Earth.
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- "January, 2008: Hydrogen Map". Lunar & Planetary Lab at The University of Arizona.
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- "It's "2001 Mars Odyssey" for NASA's Next Trip to the Red Planet" (Press release). NASA HQ/JPL. 2000-09-28. Retrieved 2016-03-12.
- Christensen, P. R.; Jakosky, B. M.; Kieffer, H. H.; Malin, M. C.; McSween Jr., H. Y.; Nealson, K.; Mehall, G. L.; Silverman, S. H.; Ferry, S.; Caplinger, M.; Ravine, M. (2004). "The Thermal Emission Imaging System (THEMIS) for the Mars 2001 Odyssey Mission". Space Science Reviews. 110 (1–2): 85. Bibcode:2004SSRv..110...85C. doi:10.1023/B:SPAC.0000021008.16305.94.
- Boynton, W.V.; Feldman, W.C.; Mitrofanov, I.G.; Evans, L.G.; Reedy, R.C.; Squyres, S.W.; Starr, R.; Trombka, J.I.; d'Uston, C.; Arnold, J.R.; Englert, P.A.J.; Metzger, A.E.; Wänke, H.; Brückner, J.; Drake, D.M.; Shinohara, C.; Fellows, C.; Hamara, D.K.; Harshman, K.; Kerry, K.; Turner, C.; Ward1, M.; Barthe, H.; Fuller, K.R.; Storms, S.A.; Thornton, G.W.; Longmire, J.L.; Litvak, M.L.; Ton'chev, A.K. (2004). "The Mars Odyssey Gamma-Ray Spectrometer Instrument Suite". Space Science Reviews. 110 (1–2): 37. Bibcode:2004SSRv..110...37B. doi:10.1023/B:SPAC.0000021007.76126.15.
- "Mars Odyssey: Newsroom". NASA Jet Propulsion Laboratory.
- "Mission Timeline - Mars Odyssey". NASA Jet Propulsion Laboratory.
- NASA, JPL. "Communications Relay - Mars Odyssey". mars.nasa.gov. Retrieved 2018-10-31.
- "Longest-Lived Mars Orbiter Is Back in Service". Status Reports. JPL. 2012-06-27. Archived from the original on 2012-07-03.
- NASA, JPL. "Guidance, Navigation, and Control - Mars Odyssey". mars.nasa.gov. Retrieved 2018-10-31.
- Staff (2014-02-12). "NASA Moves Longest-Serving Mars Spacecraft for New Observations". Press Releases. Jet Propulsion Laboratory. Archived from the original on 2014-02-26.
- Webster, Guy; Brown, Dwayne (October 19, 2014). "NASA's Mars Odyssey Orbiter Watches Comet Fly Near". NASA. Retrieved 2014-10-20.
- Webster, Guy; Brown, Dwayne (October 19, 2014). "NASA's Mars Reconnaissance Orbiter Studies Comet Flyby". NASA. Retrieved 2014-10-20.
- Jones, Nancy; Steigerwald, Bill; Webster, Guy; Brown, Dwayne (October 19, 2014). "NASA's MAVEN Studies Passing Comet and Its Effects". NASA. Retrieved 2014-10-20.
- Webster, Guy; Brown, Dwayne; Jones, Nancy; Steigerwald, Bill (October 19, 2014). "All Three NASA Mars Orbiters Healthy After Comet Flyby". NASA. Retrieved 2014-10-20.
- France-Presse, Agence (October 19, 2014). "A Comet's Brush With Mars". The New York Times. Retrieved 2014-10-20.
- Kremer, Ken (2010-12-13). "The Longest Martian Odyssey Ever". Universe Today. Archived from the original on 2010-12-20.
- "THEMIS makes 60,000 orbits of Red Planet | Mars Odyssey Mission THEMIS". themis.asu.edu. Retrieved 2017-02-21.
- "January, 2008: Hydrogen Map". Lunar & Planetary Lab at The University of Arizona.
- "Confirmation of Water on Mars". Phoenix Mars Lander. NASA. 2008-06-20. Archived from the original on 2008-07-01.
- "THEMIS Support for MSL Landing Site Selection". THEMIS. Arizona State University. 2006-07-28. Archived from the original on 2006-08-14.
- Gold, Scott (2012-08-07). "Curiosity's perilous landing? 'Cleaner than any of our tests'". Los Angeles Times. Archived from the original on 2012-08-09.
- The Mars Odyssey site
- 2001 Mars Odyssey Mission Profile by NASA's Solar System Exploration
- Sky & Telescope: "Mars Odyssey Pays Early Dividends"
- BBC News story on Mars Odyssey observations of apparent ice deposits
- Mars Trek - Shows present overhead position of Mars Odyssey | 0.878075 | 3.145415 |
The course provides a general overview of space science from an astronomical perspective, so that students can access available space astronomy assets, know what is and how it will be available for scientific utilization, how the writing-of proposal-mechanism works regarding space missions, and know about the interaction with ground based instrumentation.
The course should also provide insight in how to participate in discussion, preparation and then implementation of a space project, given that you are part of the astronomical community (active participation in projects, preparation for proposing new space missions, etc.).
The course also describes the development of a space mission. It provides insight on how to focus your career into the field of space astronomy (including the ‘agency side’) from a scientific viewpoint.
The course uses the field of exoplanetology as the scientific ‘model’ that the description of space missions in general is based on. Stellar physics, particularly the topic of asteroseismology, which which is a new tool to stellar interiors, and retrieve the fundamental stellar parameters (e.g. mass, radius, age, etc.) with unprecedented precision is taught in detail. This technique can only be fully utilized in space and it will have a tremendous impact on essentially all aspects of astrophysics but especially in the field of exoplanetology. Therefore this topic is taught in detail. The relevant missions (e.g. CoRoT, Kepler, PLATO, Darwin, Terrestrial planet Finder, TPF) are described in detail.
The course consists of the following elements, not necessarily in this order:
Why observe from space? The planet Earth environment (atmosphere including chemical composition, physical conditions, ionosphere, particle environment). Balloon astronomy, sounding rockets and launchers to deep space. Definition of a space project (scientific idea, scientific objectives, scientific requirements, general technical solution).
The orbital mechanics of binary stars, exoplanets and space craft is described. How do you determine exoplanetary parameters? What we know about stellar parameters today is almost exclusively from studies of binaries? What orbit does your spacecraft need vs what orbit can it achieve?
Astronomical objectives of IR and Submm space missions Specific IR and Submm satellite missions (e.g. IRAS, ISO, Spitzer, Herschel & Planck, JWST): Satellite design, instrument design and realised instrumentation, science topics, trends, future (interferometry).
Exoplanets from space. The scientific issues. Understanding the relation between star and planet – stellar physics vs planetary physics. Detection techniques from space. Asteroseismology. Habitable exoplanets. The future.
The building of a Space Astronomy Mission using exoplanetary missions as examples: The role and tasks of the scientist in assessment, technical implementation and scientific implementation. NOTE: these two last topics take up about 1/2 of the course.
A special seminar with discussion on the different ways of reaching space with your equipment/problem. The space agencies (ESA & NASA) are providing space access at the moment, but this will not always be so. The future is important in this course because a) The timeline for space projects is usually 10-20 years, and b) because it is going to be YOU who form the future and it will be what you make of it.
Available space resources and using them for your science. Preparing observing proposals. Handling data. Organisation of consortia.
The student should have a general overview of space science from an astronomical perspective. A general knowledge of the space oriented community (e.g. ESA and NASA) is given.
The student will also have been give examples of successful space missions (ISO, Herschel and Planck).
The student should be able to access available and coming space astronomy assets. The student should also know what is and will be available for scientific utilisation in the next 10-year period.
The student should have an understanding of the interplay between ground-based and space-based instruments.
After the course the student will have an understanding of the background and evolution of the scientific case for a space mission, and, how this scientific case is turned into specific instrumental requirements, and finally, how these can be implemented in the space environment.
See MSc schedules.
Mode of instruction
Lectures and exercises.
Written exam plus problems during course.
Lecture notes made available after each lesson, papers from the literature handed out during lessons.
Exchange and Study Abroad students, please see the Prospective students website for information on how to apply. | 0.88055 | 3.556154 |
On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) telescope in Hawaii announced the first-ever detection of an interstellar asteroid – I/2017 U1 (aka. ‘Oumuamua). Since that time, no effort has been spared to study this object before it leaves our Solar System. These include listening to it for signs of communications, determining its true nature and shape, and determining where it came from.
In fact, the question of this interstellar object’s origins has been mystery since it was first discovered. While astronomers are sure that it came from the direction of Vega and some details have been learned about its past, where it originated from remains unknown. But according to a new study by a team of astronomers from the University of Toronto, Scarborough, ‘Oumuamua may have originally come from a binary star system.
The study, titled “Ejection of rocky and icy material from binary star systems: Implications for the origin and composition of 1I/‘Oumuamua “, recently appeared in the Monthly Notices of the Royal Astronomical Society. The study was led by Alan P. Jackson, a research fellow at the Center for Planetary Sciences (CPS) at the University of Scarborough, and included members from both the CPS and the Canadian Institute for Theoretical Astrophysics (CITA).
For the sake of their study, Jackson and his co-authors considered how in single star systems (like our own), asteroids do not get ejected very often. For the most part, it is comets that become interstellar objects, mainly because they orbit the Sun at a greater distance and are less tightly bound by its gravity. And while ‘Oumuamua was initially mistaken for a comet, follow-up observations by the European Southern Observatory (ESO) indicated that it is likely an asteroid.
With the help of other astronomers, it soon became apparent that ‘Oumuamua was likely an oddly-shaped rocky object that measured about 400 meters (1312 ft) long and was tube-shaped. These findings were rather surprising to astronomers. As Jackson explained in a recent Royal Astronomical Society press release:
“It’s really odd that the first object we would see from outside our system would be an asteroid, because a comet would be a lot easier to spot and the Solar System ejects many more comets than asteroids.”
As such, Jackson and his team hypothesized that interstellar objects like ‘Oumuamau are more likely to be ejected from a binary system. To test this theory, they constructed a population synthesis model that considered just how common binary star systems are in the Galaxy. They also conducted 2000 N-body simulations to see just how efficient such systems would be at ejecting objects like ‘Oumuamua.
What they found was that binary stars are produced at a rate of about 30% by number and 41% by mass, and that rocky objects like ‘Oumuamua are far more likely to be ejected from binary than single star systems. Based on ‘Oumuamua’s rocky composition, they also determined that the asteroid was likely ejected from the inner part of its solar system (i.e. inside the “Ice Line”) while the system was still in the process of formation.
Lastly, they determined that rocky objects are ejected from binary systems in comparable numbers to icy objects. This is based on the fact that the presence of a companion star would mean that more material would become unstable due to stellar encounters. In the end, this material would be more likely to be ejected rather than accreted to form planets, or take up residence in the outer reaches of the star system.
While there are still many unanswered questions about ‘Oumuamua, it remains the first interstellar asteroid that scientists have ever known. As such, its continued study can tell us a great deal about what lies beyond our Solar System. As Jackson put it:
“The same way we use comets to better understand planet formation in our own Solar System, maybe this curious object can tell us more about how planets form in other systems.” | 0.938673 | 4.049308 |
Newly discovered planet is tiniest one yet
Kepler-37b is roughly size of Earth's moon, report released today says
A hot, rocky planet discovered using the Kepler space telescope is the smallest ever found outside our solar system.
The new planet, called Kepler-37b, has a radius less than a third the size of Earth’s, making it roughly the size of the moon, a paper published online in the journal Nature reported Wednesday.
"The thing that really I find astounding about this is we’ve managed to find a planet that is smaller than any that we know of in our own inner solar system," Thomas Barclay, a researcher at NASA-Ames Research Center, who led the study, said in an interview with CBC News.
Barclay noted that many of the first planets found outside our solar system were larger than the planets found in our own solar system, showing that stellar systems could be quite different from our own.
Quirks & Quarks talks to Kepler planetary scientist Courtney Dressing Feb. 23 at noon on CBC Radio One.
"Now we know that things are not only larger than what we have in our own solar system, but also smaller," he said.
Kepler-37b is "significantly smaller" than Mercury, which has officially been the smallest planet in our solar system since Pluto was demoted to a "dwarf planet" by the International Astronomical Union in 2006.
Kepler-37b is the inner-most of three planets detected orbiting a star called Kepler-37, located about 210 light years away from Earth in the constellation Lyra.
The star is sun-like, but cooler and a little bit smaller than the sun, according to the paper.
Kepler-37b is thought to be rocky, with no atmosphere, like Mercury. Because it is very close to its star, its surface temperature is estimated to be a scorching 400 C. The little planet is also a speedy traveller, completing its journey around its star once every 13 days.
The two other planets in the system are Kepler-37c, which has a radius about 70 per cent the size of Earth’s, and Kepler-37d, which has a radius about double that of the Earth’s.
The Kepler space telescope, launched in 2009, is pointed at stars in the constellations Cygnus and Lyra located between a few hundred and a few thousand light years away, within our own Milky Way galaxy.
The telescope detects planets by measuring the brightness of stars over time and detecting dips in the brightness caused by planets passing in front of the star during the course of their orbits. The smaller the planet relative to the size of the star, the smaller the change in brightness and the more difficult the planet is to detect — even though smaller planets are expected to be more common than larger planets.
Barclay said it was a bit of luck that allowed his research team to detect Kepler-37b from an extremely tiny signal. The star is relatively bright and doesn't have a lot of activity on its surface such as star spots and flares that could cause other variations in brightness. Such phenomena would make it more difficult to detect the dimming caused by planets.
"For most stars we are not so lucky," Barclay added.
While it's hard to extrapolate how common planets this size are from a single sample, he said, "the fact that we found one around one of the very few stars that we could find one is suggestive that small planets may be very common."
In order to confirm that Kepler-37b is actually a planet and not a "false positive" caused by some other phenomena, such as planets passing in front of other stars in the background, the researchers took extra high-resolution images and measurements using ground-based telescopes.
They also used a computer to simulate possible scenarios that could generate a signal that looked like a planet, allowing them to rule out almost all those possibilities.
"The result was a 99.95 per cent confidence that Kepler-37b is a bona fide planet," Barclay said.
As of Wednesday, the Kepler mission had confirmed the detection of 105 planets. | 0.837545 | 3.403437 |
The problems below are all related to "Stargazers to Starships." They are arranged in the order of the relevant sections, whose numbers are given in brackets [ ]. Re denotes Earth radius. |
Teachers using this material in class may obtain a list of solutions by regular mail, by sending a personal request on school letterhead to
Dr. David P. Stern, Code 695, Goddard Space flight Center, Greenbelt, MD 20771, USA
- Suppose you look down on the solar system from somewhere north of it (from the direction of the star Polaris). You note that the Earth orbits around the Sun in a counterclockwise direction. If you assume the Earth is fixed and the Sun moves ("apparent motion of the Sun")--does the Sun circle the Earth clockwise or counterclockwise?
- You have a telescope, mounted on an equatorial axis, with a clockwork to track the stars. It has crosshairs and a scale going through the middle of your image.
You suspect that the positions of stars near the horizon are shifted by refraction of light through the atmosphere. (Air refracts light much less than water or glass--but light from a star near the horizon must pass through a very thick layer.) How can you check this out, and measure the effect if it exists?
- You are in a lifeboat boat close to the equator, somewhere south of Hawaii. The pole star is too close to the horizonto be seen, but Orion is in the sky, rather close to the horizon, too, and you know that the 3 conspicuous stars in a line, forming Orion's "belt," straddle the celestial equator. How do you find where north is?
- Rudyard Kipling in his poem "The Road to Mandalay" (Mandalay is in Burma-Myanmar) wrote
"On the Road to Mandalay
Where the flyin' fishes play
An' the dawn comes up like thunder
Outer China 'crost the Bay
- Is sunrise any faster in the tropics--or actually slower--or else, latitude really makes no difference? Explain.
- You are on a seashore in the tropics, watching sunset. If the bending of light in the atmosphere is neglected, and the visual size of the sun's disk is half a degree in diameter, how much time (approximately) passes from the moment the disk just touches the horizon to when the disk disappears completely?
- [2a] Can a sundial work correctly if its gnomon casts its shadow not on a horizontal surface but on a vertical one, e.g. the wall of a house? Explain.
- [2a] Suppose you have built a really big sundial, big enough to have divisions for minutes between the hour lines. You have corrected it for your position in your time zone and are taking the equation of time into account. What else may affect its accuracy?
- At high latitudes, close to the pole--Alaska, Canada, Scandinavia etc.--the Sun is never far from the horizon. In the summer it moves around the horizon and may be visible 18, 20 or even 24 hours of the day. In the wintertime the Sun rises only for a short time, or in regions near the pole, not at all.
To what extent does the Moon act that way?
- People watching the Moon from the US see the eyes of the "Man in the Moon" above the Moon's middle and his mouth below the middle. Do people in southern Argentina see it the same way, or upside down? Explain.
- (a)
A polar satellite, in a low Earth orbit passing over both poles, makes 16 orbits each day. Viewed from Earth, how far apart in longitude are its consecutive passes over the equator?
The Space Shuttle has a low Earth orbit inclined by about 30° to the equator. How far apart are its consecutive passes over the equator? (sin30°=0.5).
- The war between Japan and the US started in 1941 when Japanese warplanes bombed, at almost the same time, US bases on the Phillipine islands and at Pearl Harbor on Hawaii. History books tell that Pearl Harbor was attacked on December 7, 1941, while the Phillipines were attacked on December 8. How can that be?
- [5a] This problem concerns example (2) in the section on navigation, about the position of the noontime Sun at the time of the summer solstice (21 June). A formula there states that the angle a south of the zenith, at which the Sun at noon crosses the north-south direction at any latitude l, equals on that day
a = l - e
where e=23.5° is the inclination angle by which the Earth's axis deviates from the direction perpendicular to the ecliptic.
What happens if l is smaller than e?
- A desk calendar has two cubes, next to each other on a shelf, to mark the day of the month---from 01, 02, 03.... to ...29, 30, 31. By rearranging the cubes, the owner of the calendar can always display the proper number of the date. What numerals should be on the faces of each cube, if the numeral "6" can also spell "9" when placed upside-down?
- At a typical location on Earth, how many moonrises occur in a year?
Hint: The Moon circles the Earth in the same direction as the Earth spins. Imagine a weightless string connecting the Earth and the Moon. As the Earth rotates, the string gets wound up around it, but being perfectly stretchable, it never tears but always continues to bridge the distance between the two bodies.
After one year, how many times is the string wrapped around the Earth?
- A synchronous satellite keeps its position above the same spot on Earth. Is its period 24 hours or 23 hrs. 56.07 min ("star day")?
- In the calendar of the Maya Indians, living in Yucatan (around latitude 20 North), special attention was given to the "zenial days" when the noontime Sun was exactly overhead ("at the zenith"). At what dates of the year (approximately) were those days?
- In one of the eclipses of 1999 the Moon is unable to cover the entire Sun. In the middle of the eclipse zone, where one would expect a total eclipse, a narrow ring of light remains, extending all the way around the dark disk of the Moon. Not knowing anything more about that eclipse, in what part of the year would you think it is most likely to be?
(a) The radius of the Earth is 6371 km. What is the velocity, in meters/sec, of a point on the surface of the Earth, at the equator?
(b) When a rocket is launched, it starts not with velocity zero, but with the rotation velocity which the Earth gives it. Thus if a rocket is launched eastward, it requires a smaller boost (and if westward, a larger one) to achieve orbit. Cape Canaveral is at latitude 28.5 north, cos(28.5°) = 0.8788: how many meters/sec. do we gain the the cape, by launching a rocket eastward?
If orbital velocity is 8 km/sec, what percentage of it do we gain.
(One important reason the main US launch facility was placed in Cape Canaveral was the ability to launch eastward over the ocean).
- (a) [8b] Could Hipparchus have used a sundial to check if the eclipses at the Hellespont and in Alexandria reached their peak at the same time?
(b) [8c] A sundial obviously won't work at night, but could Hipparchus have used an instrument tracking the positions of the stars (the way a sundial tracks the position of the Sun) to tell the duration of a lunar eclipse?
(c) [8c] Let the duration of a lunar eclipse be the time between the moment the Moon goes completely dark to the moment it begins to be uncovered; it is visible, of course, all over the Earth's night side.
Similarly, the duration of a solar eclipse would be the time between the beginning of totality anywhere on Earth and the end of totality anywhere (at a different location!). What would you think lasts longer, and why: the longest lunar eclipse or the longest solar eclipse?
- [8c] Calculate the size (in degrees) of the angle ACB or A'CB' in the drawing of section (8c), i.e. the angles between the lines from your left and right eyes to your outstretched thumb. Assume that the approximate rule, that AC and BC are 10 times the distance AB, holds exactly. Rather than using trigonometry, you may view the distance AB as part of a large circle.
- [8c] How many km equal a parsec? A light year? Take the radius of the Earth's orbit as 300 million km, the velocity of light as 300,000 km/sec.
(This calculation is best done using the scientific notation for large numbers. You may know the phrase "astronomical number" for a number that is very, very, very big--this might well be where the term originated!).
- [9a] Express the observational result on the position of the half-moon (the way Aristarchus believed it was), using the terms "parallax" and "baseline."
(a) If Aristarchus had continued to observed a lunar eclipses, he might have concluded that the width of the Earth shadow was not twice the width of the Moon but 2.5 times that width. Using such a more accurate observation, how many Moon diameters would equal the width of the Earth?
(b) In the drawing of section (9b), suppose we were in a spaceship near point C during a total eclipse of the Moon. What would we see?
- Tycho's nova had right ascension RA = 0 h, 22 m, declination d = 63° 53'. Look up a star chart--in which constellation did it occur?
- Section #8b, about using a total solar eclipse to estimate the distance of the Moon, includes a map of the eclipse of August 11, 1999. The path of totality across the Black Sea is shown, as are samples of the region of totality at selected times. You will notice that region is nearly circular.
However, on a map of the complete path of totality (which by the way is available at the web site cited there), you will find that as you follow that path, the patch of totality becomes more and more elliptical and elongated. By the time the eclipse ends, at sunset in India, the patch is a rather lengthy ellipse. Why? And why do you suppose the duration of the eclipse is shorter there?
- From a handbook, the periods T in days and the distances r in millions of kilometers, for the 4 main satellites of Jupiter (known as the "Galilean satellites" since Galileo discovered them) are: | 0.812027 | 3.372276 |
Recently NASA’s spacecraft Parker Solar probe launched in August 2018. Though, results contradicted all the expectations that researchers have regarding solar winds act. Soon this Parker Solar will become the closest spacecraft ever. This spacecraft has completed three out of 24 planed passes, which is never before explored. Through this, researchers will get to know the atmosphere of the sun and the corona. Also, results are the opposite of expectation. “Switchbacks” are flips in the sun’s magnetic field. Scientists are still confused about this Switchbacks. To resolve this confusion, scientists are studying intensely about stars, how they born? Throw this scientist will understand the process by which stars took born. Also, this spacecraft will help to answer significant queries about basic questions about the physics of the stars. Mr. Thomus Zurbuchen said, “data which is sent by parker would revile the history of our stars and the sun in so many ways which are quite surprising.”
Scientists were astonished when they found “solar winds are moving fast at the speed of ten-time substantial than assumption according to the standard model.” Said Justin Kesper, who is the principal investigator at the University of Michigan. Researchers also got that the Sun’s radiation spread dust particles at about 3.5 million miles itself. This research is revolutionary in terms of findings, particle movements, and the hot conditions surrounding the sun.
We needed a space mission like Parker Solar Probe, who can go into the sun’s atmosphere by which we get to learn the details about the solar process. Also, it will increase the knowledge about the sun for future research, which we know till now. Currently, Parker Solar Probe has sent some pictures they are showing dust around the sun. This dust is so powerful having high temperatures, mighty sunlight, and heat, which is creating gas around the sun. As per assumptions, this dust was there, but no one has seen it before, this spacecraft will help to find out all the mystery about the sun and surroundings. And if we see the data results are coming nice. | 0.821748 | 3.043235 |
Study Reveals Similarity Among Chemicals On Comets
People in the past have looked at comets in awe. Comets then were said to be heralds of something dire. Comets these days are seen much differently. A study reveals similarity among chemicals on comets.
Comets are more than just balls of ice travelling into our solar system. Astronomers are getting a new appreciation of comets as more studies are made on them. Now it's being found out that comets have different chemicals on them. These chemicals react with one another in different ways in different comets.
No two comets are exactly alike. Even though there is a similarity among chemicals on comets, the chemical compositions that make up these comets vary. That means the chemicals also interact differently between comets. The research is part of an ongoing one made by researchers from John Hopkins University. The research is led by Neil Dello Russo, lead researcher and a space scientist at the John Hopkins University Applied Physics Laboratory.
Comets can help in understanding more on how the solar system has been formed, according to Science Daily. The chemicals found on the comets might provide a view on what the early solar system has been made of. Methane, carbon monoxide and ammonia can be found on comets. Water as well as been found on comets.
Each comet has a different chemical signature. The comets are classified into two classes. There is a class called short period comets coming from the Kuiper Belt. There is also the long period comets that come from the Oort Cloud. Even within each class, comets can vary widely.
For the study, Earth-based instruments have been used, as the John Hopkins Applied Physics Laboratory notes. These instruments include the high resolution infrared spectrometer, used to observe the differences in comet tails. A number of spectrometers have been used, one of them being the Near-Infrared Spectrometer (NIRSPEC) at the Keck 2 Telescope in the W.M. Keck Observatory.
As more studies are made on comets, astronomers are realizing that they have some similarities, but at the same time they also have differences. The study reveals that while there is similarity among chemicals on comets, these chemicals vary in composition. There is a new study that says the evidence for life on Mars has been found a long while back.
Pluto’s Ocean Could Have The Possibility Of Life
The New Horizons mission on Pluto has ended, though it has left scientists with much data to study and speculate on. One speculation is that Pluto's ocean could have the possibility of life in it.
Running Water Caused Changes On Mars’ Surface
Mars today is a much barren place. However, in the past scientists speculate it has much water. Running water likely caused changes on Mars' surface.
Is This How Solar System Was Formed?
There have been many theories about how the solar system has been formed. A new theory is being proposed. Is this how the solar system was formed?
Armageddon 2016: Are We Prepared For An Asteroid Impact? NASA Experts Say We’re Not; Details Inside
Considering the possibility of an asteroid collision on Earth, how prepared are we in facing this unpleasant surprise? When will this asteroid impact be? Can we still do something about this or is it too late for the human race? Here’s what experts have to say
Two-Mile Wide Meteor Might Come Dangerously Close To Hitting Earth
A recurring asteroid is threatening Earth once again and could hit our planet in the coming years. Experts classed the space debris as a “potentially hazardous asteroid” and are currently tracking its path to see if a collision is indeed imminent.
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Darkest Dungeon Is Celebrating Its New DLC With A Free Weekend: Here Are Some Tips To Help You Out!
Red Hook Studio's Darkest Dungeon has had a new DLC released on Steam and with it a free weekend. Grab the PvP game and try it out after reading these tips on how you can play the game the best you can. | 0.880683 | 3.459567 |
On May 5, Cinco de Mayo, the Eta Aquarids meteor shower will be visible in both the Northern and Southern hemispheres - peaking in the early hours of the night.The meteors seen in the Eta Aquarids shower originate from Halley's Comet, separated from the celestial body hundreds of years ago - considering the current path of Halley's Comet does not pass close enough to Earth's orbit to produce meteoric activity. Halley's Comet spends about 76 years orbiting the sun, the last time it was seen by observers on Earth was in 1986. It is expected to return to the inner solar system around 2061-2062. The Comet, founded by Edmund Halley in 1705, is the only comet that tends to appear twice in a lifetime. Halley predicted that the comet he observed in 1705 was in fact the same comet that has been described by other observers in the past. Sightings have been reported for nearly a millenia, the earliest was depicted on the Bayeux tapestry which chronicles the Battle of Hastings in 1066."Each time that Halley returns to the inner solar system its nucleus sheds a layer of ice and rock into space," according to NASA. "The dust grains eventually become the Eta Aquarids in May and the Orionids in October if they collide with Earth's atmosphere."The annual shower is typically visible from late April until the end of May, however, peak activity normally occurs on or around May 5 when Earth's orbit passes through the separated debris trail."These meteors are fast—traveling at about 148,000 mph (66 km/s) into Earth's atmosphere. Fast meteors can leave glowing "trains" (incandescent bits of debris in the wake of the meteor) which last for several seconds to minutes," according to NASA. "In general, 30 Eta Aquarid meteors can be seen per hour during their peak."While the meteor shower's visibility is more prominent in the Southern Hemisphere due to the radiant constellation Aquarius - to which its owes its namesake - being higher up in the sky, northern observers can catch a good glimpse of the meteors, known as "earthgrazers," along the Earth's horizon in the hours just before dawn. The view from the Northern Hemisphere typically produces 10 meteors an hour.To get the best view of the meteor showers, find a dark place away from light sources and light pollution between midnight and 4 a.m. Lie flat on your back with your feet facing east. It is best not to look at your phone for 30 minutes before looking for meteors, as it will take your eyes that amount of time to adjust to the night sky.There is a possibility the visibility of meteor shower will be dimmed by the "Super Flower Moon" expected to appear in the sky on May 7, rising at a shorter distance (361,184km away) from the Earth than normal - called a "supermoon" which can be 14% larger and 30% brighter than a normal moon, according to Science Focus. If the moon is within 10% of its closest distance to the earth at the moment of a full moon, then it is considered to be a supermoon, according the Royal Observatory in Greenwich, London.So, if you see the full moon during the early nighttime hours of May 7 and think it looks overly large, you are right.This will be the third supermoon of the year, following the "Super Snow Moon" in February and the "Super Pink Moon" in April. However, the "Super Flower Moon" will be the last occurring supermoon until April 2021.April's full moon was the closest supermoon of 2020, and was dubbed the 'Pink Moon' after the pink flowers that start to bloom in the fields during April in some areas of the world. | 0.87964 | 3.946801 |
When it comes to searching for ET, current efforts have been almost exclusively placed in picking up a radio signal – just a small portion of the electromagnetic spectrum. Consider for a moment just how much lighting we here on Earth produce and how our “night side” might appear as viewed from a telescope on another planet. If we can assume that alternate civilizations would evolve enjoying their natural lighting, wouldn’t it be plausible to also assume they might develop artificial lighting sources as well?
Is it possible for us to peer into space and spot artificially illuminated objects “out there?” According to a new study done by Abraham Loeb (Harvard), Edwin L. Turner (Princeton), the answer is yes.
For gathering light, the array of Earthly telescopes now at science’s disposal are able to confidently observe a light source comparable in overall brightness to a large city — up to a certain distance. Right now astronomers are able to measure the orbital parameters of Kuiper belt objects (KBOs) with the greatest of precision by their observed flux and computing their changing orbital distances.
However, is it possible to see light if it were to occur on the dark side? Loeb and Turner say that current optical telescopes and surveys would have the ability to see this amount of light at the edge of our Solar System and observations with large telescopes can measure a KBOs spectra to determine if they are illuminated by artificial lighting using a logarithmic slope (sunlit object would exhibit alpha=(dlogF/dlogD) = -4, whereas artificially-illuminated objects should exhibit alpha = -2.)
“Our civilization uses two basic classes of illumination: thermal (incandescent light bulbs) and quantum (light emitting diodes [LEDs] and fluorescent lamps)” Loeb and Turn write in their paper. “Such artificial light sources have different spectral properties than sunlight. The spectra of artificial lights on distant objects would likely distinguish them from natural illumination sources, since such emission would be exceptionally rare in the natural thermodynamic conditions present on the surface of relatively cold objects. Therefore, artificial illumination may serve as a lamppost which signals the existence of extraterrestrial technologies and thus civilizations.”
Spotting this illumination difference in the optical band would be tricky but by calculating the observed flux from solar illumination on Kuiper Belt Objects with a typical albedo, the team is confident that existing telescopes and surveys could detect the artificial light from a reasonably brightly illuminated region, roughly the size of a terrestrial city, located on a KBO. Even though the light signature would be weaker, it would still carry the dead give-away – the spectral signature.
However, we currently don’t expect there to be any civilizations thriving at the edge of our solar system, as it is dark and cold out there.
But Loeb has posed that possibly planets ejected from other parent stars in our galaxy may have traveled to the edge of our Solar System and ended up residing there. Whether a civilization would survive an ejection event from their parent system, and then put up lamposts is up for debate, however.
The team isn’t suggesting that any random light source detected where there should be darkness might be considered a sign of life, though. There are many factors which could contribute to illumination, such as viewing angle, backscattering, surface shadowing, outgassing, rotation, surface albedo variations and more. this is just a new suggestion and a new way of looking at things, as well as suggested exercises for future telescopes and studying exoplanets.
“City lights would be easier to detect on a planet which was left in the dark of a formerly-habitable zone after its host star turned into a faint white dwarf,” Loeb and Turner say. “The related civilization will need to survive the intermediate red giant phase of its star. If it does, separating its artificial light from the natural light of a white dwarf, would be much easier than for the original star, both spectroscopically and in total brightness.”
The next generation of optical and space-based telescopes could help to refine the search process when observing extra-solar planets and preliminary broad-band photometric detection could be improved through the use of narrow-band filters which are tuned to the spectral features of artificial light sources such as light emitting diodes. While such a scenario on a distant world would need to involve far more “light pollution” than even we produce – why rule it out?
“This method opens a new window in the search for extraterrestrial civilizations,” Loeb and Turner write. “The search can be extended beyond the Solar System with next generation telescopes on the ground and in space, which would be capable of detecting phase modulation due to very strong artificial illumination on the night-side of planets as they orbit their parent stars.”
Read Loeb and Turner’s paper: Detection Technique for Artificially-Illuminated Objects in the Outer Solar System and Beyond.
This article was inspired by a discussion on Google+.
Nancy Atkinson also contributed to this article. | 0.803886 | 3.93514 |
A. The Discovery
Sometime, maybe 1.5 billion years ago, two large collapsed stars began a long, slow mating dance. Wedded by gravity, they patiently circled their center of mass, inching together imperceptibly (perhaps a few meters each year, like the Hulse-Taylor binary), all the while quickening their speed. As they approached one another – over millions of years – they shed vast amounts of energy via gravitational radiation, and seconds before the end of their dance, their gyration increased feverishly as their relative speed approached half that of light. Then, in a split second, they embraced to form a single black hole, emitting a final burst of gravitational radiation that briefly outshone the light emitted by the entire visible universe! 1.3 billion years later, on September 15, 2014, this blast of energy reached planet Earth, where it was detected by two gargantuan, souped-up Michelson interferometers, each with arms 4 km long, collectively called the Laser Interferometer Gravitational Wave Observatory (LIGO). (See Fig. 2.)
The passing gravitational wave differentially changed the length of each detector’s arms by about one-thousandth the diameter of an atomic nucleus, inducing an unmistakable signal 24 times greater than background noise. The age of gravitational-wave observational astronomy had begun.
The LIGO Collaboration first reported its discovery in the February 12, 2016 issue of Physical Review Letters. (See Ref. 1.) Their main conclusions, summarized in Section II of that paper, are described clearly and simply, and best of all, they can be understood by students having an introductory-level comprehension of classical mechanics. (Because of its groundbreaking significance, the PRL paper is available open access — no subscription or institutional affiliation is necessary to download it.) Two other recently published papers will surely be helpful to educators wishing to discuss the LIGO discovery in their classrooms. The first (Ref. 2), by Lior Burko, describes an introductory lab exercise using data taken from the LIGO Open Science Center ( https://losc.ligo.org/events/GW150914/ ). It is clearly written and discusses the LIGO results in more detail than the present post. The second (Ref. 3), by Louis Rubbo et al., illustrates how to extract astrophysical information from LIGO-like (simulated) data, and a separate link offers a complete worksheet and teacher’s guide suitable for use by first-year physics or astronomy students (http://cgwp.gravity.psu.edu/outreach/activities/handson_activity/downloads/handson_teachers_guide.pdf ).
- When the two bodies merged, they shed about 3 solar masses of energy in less than 0.1 s. Show that the average power emitted during this fleeting time interval was greater than the total electromagnetic radiation emitted by the entire visible universe. (The luminosity of the Milky Way galaxy is roughly , where is the luminosity of the Sun. There are about galaxies in the observable universe.)
B. A Quick Review of Gravitational Wave Physics
Our goal is to introduce LIGO’s exciting discovery into the introductory mechanics curriculum, in a way that supports and complements the fundamental topics of the course. For the intended first-year audience, the discussion must rest primarily on Newtonian physics, and concepts from general relativity must be strictly limited: no tensors allowed! In the previous post, we introduced an expression (Eqn. 1) for the gravitational luminosity of two equal-mass stars in circular orbit, and later generalized (Eqn. 3) that expression to treat binary systems with unequal masses in elliptical orbit:
where is the system’s reduced mass, and is a correction associated with the orbit eccentricity ε. In the following discussion, we’ll use Eqn. 7 rather than Eqn. 1 to conform to the notation commonly found in the literature. Eqn. 7 – plus a lot of tedious algebra – is all we need to extract physical information from the LIGO signal. That signal was produced by two massive in-spiraling bodies in the split second before they merged to form a single entity, and by that time the energy drain due to gravitational radiation had circularized their orbits (, ). As usual, the total orbital energy of the binary system is half the potential energy (see PPE, section 10.6): . Setting , and proceeding just as we did in the previous post to derive Eqn. 4, we find
For spectroscopic binaries (PPE section 8.11), where we can measure a radial velocity curve for each star, and can be determined using Kepler’s 3rd law and momentum conservation. In the LIGO case, we have no radial velocity curve, but the detected signal allows us to measure the orbital period T and its rate of change . This will be sufficient to draw conclusions about the mass and nature of the system. In particular, we can understand why the two merging bodies were most likely black holes.
C. Extracting Physical Information from the LIGO Signal
Like a radial velocity curve, the period (or frequency) of the LIGO signal is directly related to the orbital period (or frequency) of the binary system. In the LIGO case, however, the period of the detected gravitational wave is half that of the orbital period (), so the wave frequency is twice that of the orbit: , where we have added the subscripts “gw” and “orb” to distinguish between wave and orbit. These relationships are easy to understand in the case of two identical bodies (Figure 3).
When the two bodies execute half an orbit, they exchange their original positions, and the gravitational effects seen far away are the same as at the start of the orbit. Therefore, the radiated wave is periodic with half the period of the orbit.
We cannot determine the orbital radius a from the detected signal, so let’s use Kepler’s 3rd law to eliminate a from Eqn. 8:
and, after MUCH messy algebra (which might be left as a student exercise), we obtain
where is called the chirp mass. Finally, using
and , we obtain
Solving for the chirp mass,
where we have now dropped the subscript “gw” to adopt the notation used in the literature.
Figure 4 is taken from Ref. 1. It shows a calculated waveform derived from the actual detected signals shown in Fig. 1 at the beginning of this post. According to Ref. 1, the signal increases in frequency from 35 to 150 Hz in the time interval 0.250 to 0.425 s immediately before the two bodies coalesce. Let’s use these numbers to calculate the chirp mass.
2. Let (in SI units), and rewrite Eqn. 10 as
Next, integrate both sides over the time interval ,
Finally, plug in the LIGO numbers to show .
3. Use Eqn. 10 to show that the total mass of the system must be greater than about . (Hint: let and derive expressions for and M in terms of and . Then minimize M.)
4. Just before the two bodies merged, their orbital frequency was about 75 Hz. Assuming , estimate the separation a between the bodies at this time. (Ans: )
Your answers to questions 3 and 4 should show that the two bodies must have been highly compact objects, either black holes or neutron stars. (Compare your answer to question 4 to the radius of the Sun.) Since a neutron star has a mass of about , they could not both have been neutron stars. Could one of them have been a neutron star?
5. Assuming one of the merging bodies was a neutron star, what was the mass of the other? (Hint: let , , and derive an expression for in terms of and . Solve for , noting that .) (Ans: , so .)
The effective radius of a black hole of mass m is given by its Schwarzchild radius . General relativity is needed to understand this properly, but a crude qualitative explanation follows from Newtonian reasoning: is the distance from a point source m at which the escape speed equals c. (Nothing, including light, can escape from a body whose radius is less than , so the body is “black.”)
6. Calculate for the mass found in Question 5. Assuming the bodies merge when their separation is equal to , calculate the orbital period immediately before merging. Then find the frequency of the gravitational wave emitted at that time. (Don’t forget the factor of 2.) (Ans: ; ; .)
7. So why did the LIGO team rule out a black hole – neutron star merger?
1. B. P. Abbott et al., “Observation of Gravitational Waves from a Binary Black Hole Merger,” Phys. Rev. Lett. 116, 061102 (2016)
2. Lior Burko, “Gravitational Wave Detection in the Introductory Lab,” arXiv:1602.04666 [physics.ed-ph]
3. Louis J. Rubbo et al., “Hands-on Gravitational Wave Astronomy: Extracting astrophysical information from simulated signals,” Am. J. Phys. 75, 597 (2007) and accompanying teacher’s guide: http://cgwp.gravity.psu.edu/outreach/activities/handson_activity/downloads/handson_teachers_guide.pdf | 0.875644 | 3.910496 |
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The 1st, lid, and Hid satellites revolve in orbits but very little inclined to the plane of the planet's orbit. During each revolution they pass
between the Sun and Jupiter, producing a solar eclipse; and also by passing through the shadow of the planet itself, cause to themselves an eclipse of the sun, and to Jupiter an eclipse of a moon. The IVth passes through a path more inclined, and therefore its eclipses are less frequent: instead of being fully eclipsed, it sometimes just grazes the shadow, as it were, and so its light is much diminished. Through a telescope we can distinctly watch the disappearance or immersion of the satellites in the planet's shadow, their reappearance or emersion, and also their transits, as a round black dot or shadow moving across the disk of Jupiter. In the cut, we see represented the various positions of the moons: the 1st is eclipsed; the lId is passing across the disk of the planet on which its shadow is also thrown; the Illd is just behind the planet, and so occulted or concealed, while it has not yet entered the shadow; the IVth is in view from the earth. These satellites revolve with great rapidity, as is necessary in order to overcome the superior attraction of the planet and prevent being drawn to its surface. The 1st goes through all its phases in If days, and the IVth in less than twenty days. A spectator on Jupiter might witness, during the Jovian year, 4,500 ecbpses of the moon (moons), and about the same number of the sun.
Jupiter's belts.—These are dusky streaks of varying breadth and number, lying more or less parallel to the planet's equator, but terminating at a short distance from the edges of the disk. Between these a brighter, often rose-colored space, marks the equatorial regions. They are not permanent, but change sometimes very materially in the course of a few minutes. Occasionally only two or three broad belts are seen; at other times a dozen narrow ones appear. It is supposed that the planet is enveloped in dense masses of cloud, and that the belts are merely fissures, laying bare the solid body beneath. The parallel appearance is doubtless due to strong equatorial currents, analogous to our tradewinds.
Velocity Of Light.—By an attentive examination of the eclipses of Jupiter's moons, Homer (a Danish astronomer, in 1617) was led to discover the progressive motion of light. Before him, it had been considered instantaneous. He noticed that the observed times of the eclipses were sometimes earlier and sometimes later than the calculated times, according as Jupiter was nearest or furthest from the earth. His investigations convinced him that it requires about 16^ min. for light to traverse the orbit of the earth. Romer's conclusion has since been verified by the phenomena of aberration of light. The velocity of light is about 183,000 miles per second. (See New Physics, p. 150.)
The god of time. Sign }, an ancient scythe.
Description.—We now reach, in our outward journey from the sun, the most remote world known to the ancients. On account of its distance, it shines with a feeble but steady pale yellow light, which distinguishes it from the fixed stars. Its orbit is so vast that its movement among the constellations may be easily traced through one's lifetime. It requires two and a half years to pass through a single sign of the zodiac; hence, when once known, it may be easily found again. The earth leaves it at conjunction, makes a yearly revolution about the sun, comes to its starting point, and overtakes Saturn in about thirteen days thereafter.* On account of its slow, dreary pace, Saturn was chosen by the ancients as the symbol for lead. It is smaller than Jupiter, but much more gorgeously attended. Besides a retinue of eight satellites, it is surrounded by a system of rings, some shining with a golden light and others transparent—a spectacle which is as wonderful as it is unique.
Motion In Space.— Saturn revolves about the sun at a mean distance of 872,000,000 miles. The eccentricity of its orbit is a trifle more than that of Jupiter,
* Prom this the year of Saturn may be determined. As 13 : 378 days :: Earth's year : Saturn's year = 30 yr. nearly.
so that while it may at perihelion come fifty million miles nearer than its mean distance, at aphelion it swings off as much beyond. We can form some estimate of the size of its immense orbit, when we remember that it is moving along at the rate of 21,000 miles per hour, and yet as we look at it from night to night, we can scarcely detect any change of place. The Saturnian year is equal to about thirty of ours, and comprises nearly 25,000 Saturnian days, each of which is about ten and a half hours in length.
Distance From Earth.—This is found in the same manner as that of the other superior planets, being least in opposition and greatest at conjunction. As the earth and Saturn occupy different portions of their orbits, the distances between them at different times may vary 200,000,000 miles.
Dimensions.—Its diameter is about 72,000 miles. Its volume is nearly 750 times that of the earth. Its density is very low indeed, being much less than that of water, and about the same as that of pine wood. The Saturnian force of gravity is therefore scarcely greater than the terrestrial, so that a stone falls toward the surface of that immense globe only about seventeen feet the first second.
Seasons.—The light and heat of the sun at Saturn are only jfo that which we receive. The axis of Saturn is inclined from a perpendicular to the plane of its orbit about 31°. The seasons therefore are similar to those on the earth, but on a | 0.842186 | 3.913075 |
Hello, and welcome to Beyond NERVA! Here, we look at the technology that will enable humanity to expand into the solar system, and eventually the stars.
It’s a trope in the space industry to comment after each failure that “space is hard.” The difficulties facing even now-routine space missions are seen every year, and the vast majority of these missions only go into orbit around the Earth, the first small step to going into space. As we go even further out, the challenges grow. In order to be able to have successful missions of any type, a huge number of different technologies have to come together; and often the value of the mission is limited by two key factors: reliability and power.
Reliability is an obvious concern; after all, there’s currently no chance of repairing the vast majority of systems that are launched into space (the Hubble Space Telescope being one of the only exceptions to this rule), and once a spacecraft has left Earth’s orbit there’s zero chance that repairs or maintenance can be performed.
Power is important in many different ways, and each is important. Power can mean the thrust needed to go to where you want to go, and to enter orbit or land when you get there; it can be electrical power for the experiments and other systems on board the spacecraft; finally, it can be heat to prevent the different components from literally freezing to death due to the harsh conditions found in the vast majority of the solar system. Every power system has its own advantages and limitations, but a key concept to consider in this is power density: how much power, of what kind (kinetic, electric, thermal), is available compared to the mass of the power supply that’s providing that power. Another is system robustness: how well will this system function under less than ideal circumstances, and how “less than ideal” do those circumstances have to be before it becomes a large problem, possibly ending the mission?
Nuclear power offers both reliability and power, in far greater measure than any other type of system available. From nuclear thermal rockets, which turn the heat of a nuclear reactor directly into thrust, to nuclear electric power supplies for both propulsion and the electricity that’s needed to survive in space, to nuclear pulse propulsion which uses controlled microdetonations of nuclear material to propel a spacecraft, to radioisotope generators which use the natural decay of radioactive material, nuclear power offers unique advantages in space. This is something that has been recognized, researched, and tested since the dawn of the nuclear age, but as of yet has been used in relatively few spacecraft.
Just because it hasn’t been used as much doesn’t mean that it hasn’t been researched extensively, though. Millions of man-years of effort, and billions of dollars, have been spent worldwide to research, design, and test a huge variety of concepts, and quite a number of them never flew only because there wasn’t a mission that required them.
Beyond NERVA looks into those concepts, the testing that has gone into them, and the future of nuclear power in space. With the rapid growth of the space industry over the last few decades, and the incredible leap in interest in the general public for returning to the Moon, going to Mars, and beyond, the challenges that were once considered possible but not practical in the past are now becoming much nearer to reality than they ever have been.
The fundamental challenges of spaceflight, however, have not changed. The same reasons that the early pioneers of space flight looked to nuclear power to solve the incredible challenges in front of them are leading the next generation of ambitious mission designers to once again turn to nuclear power to provide the power needed for these missions, in the mass budget that current launch vehicles – and the next generation as well – impose.
Beyond NERVA is a website with several parts. By far the most popular, and most updated, is the blog, which can be found here. Every few weeks (as often as I’m able to get the material together, often these posts involve dozens of hours of gathering sources, and dozens more reading them, before writing even begins!), we’ll look at either a particular system that has been proposed or flown in the past, a new system that is currently under development, or the fundamental technology and testing associated with bringing these systems to mission readiness. The next is topic-specific pages, exploring everything from overviews of different applications of nuclear power in space to particular types of technologies to the testing equipment and experiments needed to prepare these systems for spaceflight. Finally, at a future date we will be adding unique resources other than archival research and accessible information on historical and current designs, however that portion of the website is still in the early planning stages, and thousands of hours of work are left in compiling the information that’s already available (if not necessarily easily accessible) on the various aspects of nuclear technology for space.
Feel free to explore! Our Facebook group is fairly active, and growing every week. A new Twitter feed has also been started as well! On these, I share papers, articles, and other information relating to in-space nuclear power, and the FB group is a great place to discuss concepts for nuclear power and propulsion with a wide range of both professional and amateur enthusiasts on the subjects we cover here! | 0.848195 | 3.3667 |
November 15, 2018 – Analyzing data from NASA’s Magnetospheric Multiscale (MMS) mission, a team led by Southwest Research Institute (SwRI) has found that the small regions in the Earth’s magnetosphere that energize the polar aurora are remarkably calm and nonturbulent. The new observations, which also revealed intense electron jets associated with the regions where magnetic reconnection occurs, were outlined in a paper published in Science November 15.
“On the sunward side, explosive magnetic reconnection events dump energy into Earth’s magnetosphere, the region surrounding the Earth dominated by its magnetic field,” said the paper’s lead author, Dr. Roy Torbert, the heliophysics program director at SwRI’s Department of Earth, Oceans and Space at the University of New Hampshire, Durham. “Reconnection on the night side is dumping energy into Earth’s atmosphere, as electrons travel down magnetic field lines and excite aurora. The more we understand about these processes, the better we can understand and model how ‘space weather’ could affect the technology we depend on.”
Magnetic reconnection — which occurs in both natural plasma environments such as those in space and in laboratory fusion experiments — is at the heart of space weather. Reconnection is responsible for explosive solar events, such as solar flares and coronal mass ejections, and drives disturbances in Earth’s space environment. Such disturbances not only produce spectacular auroras, but also the high-energy electromagnetic radiation they send toward Earth can shut down electrical power grids and disrupt satellite-based communication and navigation systems.
NASA’s four Magnetospheric Multiscale (MMS) satellites have spent the last three years studying magnetic reconnection in the near-Earth environment. For the first half of the mission, the satellites studied reconnection that occurs in the sunward side of Earth where the solar wind — the constant flow of charged particles from the Sun — pushes into Earth’s magnetic field. The two sides connecting have different densities, which cause magnetic reconnection to occur asymmetrically, spewing electrons away at supersonic speeds. In the magnetotail, the trailing portion of the magnetosphere blown back by the solar wind, only the Earth’s field lines are colliding, so the particles are accelerated nearly symmetrically.
“For the first time, we have observed the details of the energy dissipation regions where symmetric reconnection occurs,” Torbert said. “We measured the aspect ratio of these remarkably small regions, just a few hundred kilometers in size. We’re beginning to understand the efficiency of energy release and how it connects in our environment.”
The unprecedented resolution and accuracy of the MMS measurements revealed these events last only a few seconds, producing extremely high velocity electron jets — over 15,000 kilometers per second and intense electric fields and electron velocity distributions.
“The process appears to be very efficient,” Torbert said. “Any turbulence is not strong enough to disturb discrete features of the electron velocity distributions created in the electromagnetic fields around the energy dissipation region.”
These discoveries — which have significant implications for space and solar physics, astrophysics and fundamental plasma physics — were published November 15 in Science [doi: 10.1126/science.aat2998 (2018)].
MMS is the fourth NASA Solar Terrestrial Probes Program mission. Goddard Space Flight Center built, integrated and tested the four MMS spacecraft and is responsible for overall mission management and mission operations. The principal investigator for the MMS instrument suite science team is based at SwRI in San Antonio, Texas. Science operations planning and instrument commanding are performed at the MMS Science Operations Center at the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder. | 0.803203 | 3.943585 |
NASA has announced that our next destination in the solar system is the unique, richly organic world Titan. Advancing our search for the building blocks of life, the Dragonfly mission will fly multiple sorties to sample and examine sites around Saturns icy moon.
Dragonfly will launch in 2026 and arrive in 2034. The rotorcraft will fly to dozens of promising locations on Titan looking for prebiotic chemical processes common on both Titan and Earth. Dragonfly marks the first time NASA will fly a multi-rotor vehicle for science on another planet; it has eight rotors and flies like a large drone. It will take advantage of Titans dense atmosphere four times denser than Earths to become the first vehicle ever to fly its entire science payload to new places for repeatable and targeted access to surface materials.
Titan is an analog to the very early Earth, and can provide clues to how life may have arisen on our planet. During its 2.7-year baseline mission, Dragonfly will explore diverse environments from organic dunes to the floor of an impact crater where liquid water and complex organic materials key to life once existed together for possibly tens of thousands of years. Its instruments will study how far prebiotic chemistry may have progressed. They also will investigate the moons atmospheric and surface properties and its subsurface ocean and liquid reservoirs. Additionally, instruments will search for chemical evidence of past or extant life.
With the Dragonfly mission, NASA will once again do what no one else can do, said NASA Administrator Jim Bridenstine. Visiting this mysterious ocean world could revolutionize what we know about life in the universe. This cutting-edge mission would have been unthinkable even just a few years ago, but were now ready for Dragonflys amazing flight.
Dragonfly took advantage of 13 years worth of Cassini data to choose a calm weather period to land, along with a safe initial landing site and scientifically interesting targets. It will first land at the equatorial Shangri-La dune fields, which are terrestrially similar to the linear dunes in Namibia in southern Africa and offer a diverse sampling location. Dragonfly will explore this region in short flights, building up to a series of longer leapfrog flights of up to 5 miles (8 kilometers), stopping along the way to take samples from compelling areas with diverse geography. It will finally reach the Selk impact crater, where there is evidence of past liquid water, organics the complex molecules that contain carbon, combined with hydrogen, oxygen, and nitrogen and energy, which together make up the recipe for life. The lander will eventually fly more than 108 miles (175 kilometers) nearly double the distance traveled to date by all the Mars rovers combined.
Titan is unlike any other place in the solar system, and Dragonfly is like no other mission, said Thomas Zurbuchen, NASAs associate administrator for Science at the agencys Headquarters in Washington. Its remarkable to think of this rotorcraft flying miles and miles across the organic sand dunes of Saturns largest moon, exploring the processes that shape this extraordinary environment. Dragonfly will visit a world filled with a wide variety of organic compounds, which are the building blocks of life and could teach us about the origin of life itself.
Titan has a nitrogen-based atmosphere like Earth. Unlike Earth, Titan has clouds and rain of methane. Other organics are formed in the atmosphere and fall like light snow. The moons weather and surface processes have combined complex organics, energy, and water similar to those that may have sparked life on our planet.
Titan is larger than the planet Mercury and is the second largest moon in our solar system.As it orbits Saturn, it is about 886 million miles (1.4 billion kilometers) away from the Sun, about 10 times farther than Earth. Because it is so far from the Sun, its surface temperature is around -290 degrees Fahrenheit (-179 degrees Celsius). Its surface pressure is also 50 percent higher than Earths.
Dragonfly was selected as part of the agencys New Frontiers program, which includes the New Horizons mission to Pluto and the Kuiper Belt, Juno to Jupiter, and OSIRIS-REx to the asteroid Bennu. Dragonfly is led by Principal Investigator Elizabeth Turtle, who is based at Johns Hopkins Universitys Applied Physics Laboratory in Laurel, Maryland. New Frontiers supports missions that have been identified as top solar system exploration priorities by the planetary community. The program is managed by the Planetary Missions Program Office at NASAs Marshall Space Flight Center in Huntsville, Alabama, for the agencys Planetary Science Division in Washington.
The New Frontiers program has transformed our understanding of the solar system, uncovering the inner structure and composition of Jupiters turbulent atmosphere, discovering the icy secrets of Plutos landscape, revealing mysterious objects in the Kuiper belt, and exploring a near-Earth asteroid for the building blocks of life, said Lori Glaze, director of NASAs Planetary Science Division. Now we can add Titan to the list of enigmatic worlds NASA will explore. | 0.894516 | 3.608354 |
Much more detail on Milky Way
Australian scientists have helped create the most detailed map of the Milky Way, using the world’s largest radio telescopes.
The HI4PI project, which is a combination of an Australian survey and a German survey, provides the most sensitive and detailed view of all of the hydrogen gas in and around the Milky Way and will help solve the mysteries of our galaxy.
Team leader for the Australian survey, Professor Naomi McClure-Griffiths from ANU, said the study revealed for the first time the fine details of structures between stars in the Milky Way.
“Very small gas clouds appear to have helped form stars in the Milky Way over billions of years,” she said.
The data map could be used to answer the big questions about the Milky Way and neighbouring galaxies.
“How does the Milky Way get the new gas it requires to continue forming stars? And where are all of the small dwarf galaxies that must surround our Milky Way? The next steps will be exciting,” Prof McClure-Griffiths said.
The map will also help to hone the Square Kilometre Array and the Australian Square Kilometre Array Pathfinder, which will provide even more detailed maps of the Milky Way.
The HI4PI project used the largest fully steerable radio telescopes in the southern and northern hemispheres, Australia's 64m CSIRO Parkes dish and the 100m Max-Planck telescope in Effelsberg, Germany.
The project improved on a previous neutral hydrogen study, the Leiden-Argentine-Bonn (LAB) survey, by a factor of two in sensitivity and a factor of four in angular resolution.
The team created a video animation that shows all of the hydrogen gas in the Milky Way and neighbouring galaxies, accessible below. | 0.802477 | 3.022264 |
One reason I wanted to run yesterday’s article about the Opher et al. paper on the heliosphere, aside from its innate scientific interest (and it is a very solid, well crafted piece of work) is to illustrate how much we still have to learn about the balloon-like bubble carved out by the solar wind. The entire Solar System fits within it easily, but we observe only from inside and have little knowledge of its structure. None of the paper’s authors would argue that we have the definitive answer on the shape of the heliosphere. That will take a good deal more data, as the paper notes:
Future remote-sensing and in situ measurements will be able to test the reality of a rounder heliosphere. In Fig. 6, we show our prediction for the interstellar magnetic field ahead of the heliosphere at V2. In addition, future missions such as the Interstellar Mapping and Acceleration Probe will return ENA [energetic neutral atom] maps at higher energies than present missions and so will be able to explore ENAs coming from deep into the heliospheric tail. Thus, further exploration of the global structure of the heliosphere will be forthcoming and will put our model to the test.
We’ll learn more from the Voyagers, in other words, as well as from IMAP (more about this one in a later article), New Horizons, and whatever probe we next send out to system’s edge. Our two Voyager spacecraft may well last another seven years, which would give them 50 years of data return since their launch in 1977.
Image: And here’s something we’ve learned from New Horizons. The SWAP instrument aboard the spacecraft has confirmed that the solar wind slows as it travels farther from the Sun. This schematic of the heliosphere shows the solar wind begins slowing at approximately 4 AU radial distance from the Sun and continues to slow as it moves toward the outer solar system and picks up interstellar material. Current extrapolations reveal the termination shock may currently be closer than found by the Voyager spacecraft. However, increasing solar activity will soon expand the heliosphere and push the termination shock farther out, possibly to the 84-94 AU range encountered by the Voyager spacecraft. Credit: Southwest Research Institute; background artist rendering by NASA and Adler Planetarium.
The interstellar probe NASA has been contemplating, under study at various centers but most visibly at the Johns Hopkins Applied Physics Laboratory (APL) would, unlike Voyager, be built from the start with a 50 year goal in mind. Voyager 1 is now about 141 AU from Earth (21.2 billion kilometers). Interstellar Probe (APL capitalizes its design) would go for 1000 AU, but at much improved speeds, reaching the distance in 50 years.
How to do this? For one thing, achieve a boost from one of the huge rockets now coming onto the market, perhaps NASA’s own Space Launch System (SLS), or a commercial entry from a private company, perhaps SpaceX or Blue Origin. We’re not talking about launching until 2030, and that’s assuming the mission gets the green light in the upcoming heliophysics decadal survey, which will put in place missions related to the Sun over a ten year period.
A gravity assist at Jupiter added on to its kick from a massive booster would put us in familiar territory, given Jupiter’s history of flinging spacecraft like Voyager and New Horizons on their way, but a solar gravity assist is also contemplated, one that would take Interstellar Probe a good deal closer to the Sun than the Parker Solar Probe. You’d think closer is better, but at this stage in our technology, the perihelion numbers will be decided by factoring the weight of the required heat shielding. A balancing act ensues to get the most bang for the buck.
Exactly which instruments would fly on this modern era Voyager Plus would depend upon how instrument packages can be combined to save mass while maximizing power and data rates on the communications side. If you have a look at the APL page devoted to Interstellar Probe, you’ll see a notional payload, meaning this is what we’d like to cover with an ideal probe. The instrumentation includes:
A particle and fields suite for exploring the interstellar medium and its interaction with the heliosphere, with detectors such as:
- energetic neutral atom (ENA) camera
- energetic particles/cosmic rays
- solar /interstellar plasma and neutral wind
- vector helium magnetometer
- plasma wave
Beyond the particle and fields instrumentation, the probe should include:
- Optical cameras for flyby imaging and astrometry
- A suite to measure dust and its basic composition
- Infrared cameras for obtaining the 3D distribution of dust beyond our planetary neighborhood
We know that Voyager 1 and 2 have both left the heliosphere, Voyager 1 in August of 2012 and Voyager 2 in November of 2018, the two craft on widely divergent trajectories (recall Voyager 1’s dogleg at Saturn to get a look at Titan, whereas Voyager 2 moved on for close passes at Uranus and Neptune). Yesterday’s paper offered a new proposal for the shape of the heliosphere which is rather interesting in this regard. If the heliosphere really is more circular, lacking that presumed cometary ‘tail,’ then getting outside it won’t necessarily be determined by what would have been considered the shortest route, avoiding a tail that was estimated to trail thousands of AU. Here astrophysics and engineering work together in the choice of optimum trajectories.
Yesterday we looked at the need to get beyond the heliosphere so we could study its structure and gain insights into other planetary systems. But there are other reasons that take us much farther afield. It’s worth remembering that within the heliosphere, we have to contend with the foreground infrared radiation from dust within the Solar System, known as the zodiacal cloud. Going beyond the heliosphere opens up the possibility of studying diffuse infrared radiation from other stars and galaxies that has been effectively blocked for us by that cloud.
We also get a look at the nature of the dust disk, one that we can observe around other stars but are unable to measure in terms of large-scale structure from within our own. Learning how the Sun affects the structure of the heliosphere will help us understand the dynamics of other stellar systems, and the data a probe like this will take will be crucial at defining the local interstellar medium, through which our much longer-range probes will eventually move.
Needless to say, a great deal of science can be accomplished along the way. Interstellar Probe would reach the Kuiper belt in a scant four years, where flybys of KBOs and long-range observation of the environment there would complement and extend what we are learning from New Horizons. The APL trade study is designed to craft “a realistic mission architecture that includes available (or soon-to-be available) launch vehicles, kick stages, operations concepts and reliability standards.” All of this produces the reference materials that will be needed for the science and technology definition team that will turn aspirations into hard designs.
We should always be thinking about the kinds of mission that might one day fly, the long-range improvements that can enable them, and the audacious targets we someday want to reach. But as we draw up these conjectures and think about eventually engineering them, we also must be thinking about the kind of missions that can fly today. An interstellar probe of the kind now under study at APL and other NASA centers was a part of the discussion for the last decadal survey, but only now are we reaching a technological level to make 1000 AU in 50 years possible.
We need these early steps to make the broader strides that will occur later, on a path toward a Solar System infrastructure that will eventually support probes into the Oort Cloud and one day beyond. So tracking the fortunes of Interstellar Probe will be a priority for Centauri Dreams in coming months. | 0.88807 | 3.979944 |
You sit there coarsely oscillating,
Calling to us through the ether
Beneath a blanket of stars.
You swim against the tide,
Pass a tent of clouds,
And come to rest.
This is a nonet inspired by recent research, which investigated the peculiar behaviour of the KIC 8462852 star in the Cygnus constellation. This star first came to prominence in 2015, when astronomers noticed that it underwent a series of dimming events that were both short in time and non-periodic in their occurrence. Suggestions for why these events occurred ranged from a large group of comets orbiting the star and blocking out the incoming starlight to a giant alien megastructure passing across the star’s surface!
Rather this solving this mystery, this new research has found another conundrum associated with KIC 8462852: it is getting dimmer. Over the three-year period that the researchers observed the star using NASA’s Kepler space telescope, they found that its brightness diminished by 3%, which given that the average lifetime of a star in our galaxy is approximately 50 billion years, is an incredibly large amount. The researchers are unsure as to what has caused this dimming event, as no currently known phenomena can explain such results.
This poem was also written in honour of National Poetry Day in the UK, whose theme for 2016 is Messages.
An audio version of the poem can be heard here. | 0.83895 | 3.105377 |
The 'Habitable Edge' of Exomoons
Astronomers have their fingers crossed that within the haul of data collected by NASA’s Kepler mission, which has already detected nearly three thousand possible exoplanets, hide the signatures of the very first exomoons.
The discovery of alien moons will open up an exciting new frontier in the continuing hunt for habitable worlds outside the Solar System. With the confirmation of exomoons likely right around the corner, researchers have begun addressing the unique and un-Earthly factors that might affect their habitability.
Because exomoons orbit a larger planetary body, they have an additional set of constraints on their potential livability than planets themselves. Examples include eclipses by their host planet, as well as reflected sunlight and heat emissions. Most of all, gravitationally-induced tidal heating by a host planet can dramatically impact a moon’s climate and geology.
In essence, compared to planets, exomoons have additional sources of energy that can alter their "energy budgets," which, if too high, can turn a temperate, potential paradise into a scorched wasteland.
"What discriminates the habitability of a satellite from the habitability of a planet in general is that it has different contributions to its energy budget," said René Heller, a postdoctoral research associate at the Leibniz Institute for Astrophysics in Potsdam, Germany.
The "habitable edge"
In a series of recent papers, Heller and his colleague Rory Barnes from the University of Washington and the NASA Astrobiology Institute tackled some of the big-picture problems to habitability posed by the relationship between exomoons and their host planets.
Heller and Barnes have proposed a circumplanetary "habitable edge," similar to the well-established circumstellar "habitable zone." This zone is the temperature band around a star within which water neither boils off or freezes away on a planet’s surface – not too hot, not too cold, thus earning it the nickname "the Goldilocks zone."
The habitable edge is rather different. It is defined as the innermost circumplanetary orbit in which an exomoon will not undergo what is known as a runaway greenhouse effect. "To be habitable, moons must orbit their planets outside of the habitable edge," said Heller.
A runaway greenhouse effect occurs when a planet’s or moon’s climate warms inexorably due to positive feedback loops. An example is thought to have taken place right next door, so to speak, to the other planet most like Earth that we know of: Venus.
There, the heat from a young, brightening Sun could have increasingly evaporated a primordial ocean. This evaporative process put ever more heat-trapping water vapor in the atmosphere, which led to more evaporation, and so on, eventually drying the planet out as the water was broken apart into hydrogen and oxygen by the Sun’s ultraviolet radiation. The atmospheric hydrogen on Venus escaped into space, and without hydrogen, no more water could form.
Moons situated in fairly distant orbits from their planets should be safely beyond the habitable edge wherein this desiccation takes place.
"Typically, and especially in the solar system, stellar illumination is by far the greatest source of energy on a moon," said Heller. "In wide planetary orbits, moons will be fed almost entirely by stellar input. But if a satellite orbits its host planet very closely, then the planet’s stellar reflection, its own thermal emission, eclipses and tidal heating in the moon can become substantial."
The cumulative effects of the non-tidal heating effects are small, but could be the difference between an exomoon being inside or outside the habitable edge.
Basking in the glow
Here on Earth, we get a little extra energy from the Moon in the form of moonlight, which is reflected light from the Sun.
Moons, though, get bathed in a lot more sunlight from their planetary neighbors; Earth shines almost 50 times as brightly in the lunar sky as the Moon does in our night sky. In addition to reflected sunlight, planets also emit absorbed sunlight as thermal radiation onto their exomoons.
This "planetshine" can add a not-insubstantial amount of energy to an exomoon’s overall intake. Imagine a gas giant planet orbiting a Sun-like star at about the same distance that Earth orbits our Sun. For a moon with a relatively close orbit around this planet, like Io’s orbit around Jupiter, Heller calculates that the moon could absorb an additional seven or so watts per square meter of power. (Earth absorbs about 240 watts per square meter from the Sun).
Periodic plunges into darkness
Eclipses can potentially offset some of the extra energy input from planetshine. For eclipses, Heller calculated that lost stellar illumination for an exomoon in a close orbit (similar to the closest found in our solar system) is up to 6.4 percent.
Interestingly, because most moons including ours are tidally locked to their planet – that is, one side of the moon constantly faces the planet – eclipses, as well as planetshine, would only darken and lighten one hemisphere. This phenomenon could modify the climate, as well as the behavior of life forms, in ways not seen on Earth.
"Asymmetric illumination on the moon could induce wind and temperature patterns, both in terms of geography and in time, which are unknown from planetary climates," Heller noted. "Life on a moon with regular, frequent eclipses would surely have to adapt their sleep-wake and hunt-hide rhythms as well, but only those creatures on the planet-facing hemisphere."
Although the eclipse-related loss of several percentage points of illumination is not a huge loss of energy, a moon-planet duo might need to be closer to its star to compensate for this deficit if the moon were still to be considered habitable from a Goldilocks zone perspective.
However, this situation introduces another hurdle to habitability: The closer a planet is to its star, the stronger the star’s gravitational pull is on the planet’s moons. This extra pull can tug moons into non-circular, or eccentric orbits about their planets. Eccentric orbits, in turn, result in varying amounts of gravitational stress exerted on the moon as it orbits.
These “tidal forces,” as they are called, cause heating due to friction. The ocean tides we experience on Earth occur partly as a result of the Moon’s gravity tugging more on the water and land nearest it, which distorts Earth’s shape. The effect goes both ways, of course, but not equally, with planets inducing significantly greater tidal heating within their much smaller moons.
If an exomoon’s orbit takes it too close to its planet, tidal heating could push the energy budget too high, culminating in a runaway greenhouse effect. At the extremes, the tidal heating could unleash massive volcanic activity, leaving the satellite covered in magma and distinctly inhospitable, like the "pizza moon" Io.
On the other hand, it should be noted, tidal heating might be a savior for life. Tidal heating could help sustain a subsurface ocean, like the one suspected to exist within Saturn’s moon Europa, alternatively making an otherwise unwelcoming exomoon outside the traditional habitable zone potentially livable.
Small stars, dead moons
Another factor comes into play as eclipses rob a bit of energy from an exomoon and require the moon-planet pair to be closer to their star. To remain gravitationally bound to a planet and not be ripped away by the star’s gravity, a moon must fall within a so-called “Hill radius” – the planet’s sphere of gravitational dominance. This radius shrinks with greater proximity to the host star. The closer the planet and moon are to their star, the less space is available outside the habitable edge.
For planets and attendant moons around dim, cool, low-mass stars called red dwarfs, this dynamic becomes important. The habitable zone around red dwarf stars is very tight; for a star with a quarter of the Sun’s mass, for instance, the Goldilocks zone is thought to be around just 13 percent the Sun-Earth distance – in other words, a third of Mercury’s orbital distance from the Sun.
In a red dwarf solar system, not only must a moon then be closer to its habitable zone planet, but given the planet’s necessary proximity to its star, the moon’s orbit will tend to be eccentric. These qualities increase the chances that the moon will fall within the habitable edge.
Heller calculated that for many red dwarf stars, the odds of them hosting habitable moons is accordingly slim.
"There is a critical stellar mass limit below which no habitable moon can exist," Heller said. "Around low-mass stars with masses of about twenty percent the mass of the Sun, a moon must be so close to its habitable zone planet to remain gravitationally bound that it is subject to intense tidal heating and cannot under any circumstances be habitable."
A little here, a little there
Many factors beyond habitable edge considerations, of course, ultimately determine an exomoon’s habitability. To be considered broadly habitable by creatures other than, say, subsurface bacteria, an exomoon must meet some of the same basic criteria as a habitable, Earth-like exoplanet: It must have liquid surface water, a long-lived substantial atmosphere, and a magnetic field to protect it from solar radiation (and, in the case of exomoons around gas giants like Jupiter, from the charged particles created in the giant exoplanet’s magnetosphere).
To possess these qualities, which scientists say grow likelier with increasing mass, a habitable exomoon will likely be quite large compared to those in the solar system – more on the order of the size of Earth itself. The biggest moon in our Solar System, Jupiter’s Ganymede, is just 2.5 percent of Earth’s mass. But previous studies have suggested that monstrous moons by the solar system’s standards are indeed possible.
The Kepler mission is expected to be able to detect exomoons down to about 20 percent of the mass of the Earth. The data, which consists of measuring the extremely small dips in the amount of starlight as their planets (or moons) block it from our point of view – should reveal a moon’s mass and orbital parameters as well.
Armed with this information – and now with habitable edge considerations – astronomers can thus hope to make some ballpark speculations on any soon-to-be-discovered exomoon’s propensity to support living beings.
Heller hopes that there will be a list of candidate exomoons ready for observing by next-generation instruments, such as the James Webb Space Telescope and thirty meter-class ground telescopes. These observatories, coming online in the next decade, could be able to characterize exomoon atmospheres and offer tantalizing evidence of life.
"The first exomoons that we find will be large – maybe Mars- or even Earth-sized – and therefore intrinsically more likely to be habitable than small moons," Heller said. "With Kepler finding many more giant planets than terrestrial planets in stellar habitable zones, it’s really important that we try to figure out what conditions might be like on the moons of these giants to gauge if they can host extraterrestrial life." | 0.926489 | 3.93682 |
GUIDES to the galaxy might call it Zona Galactica Incognita – the half of our home galaxy we know little about. Indeed, the Milky Way is one of the least charted spiral galaxies in the nearby universe. Now it seems that stars kicked out of their birth clusters can help fill in the void and create the first proper map of the entire galaxy.
Young star clusters and clouds of hydrogen that formed in our galaxy help trace the shapes of the Milky Way’s arms, so astronomers are reasonably certain that it has a spiral structure (see right). Observations of stellar motion show that there is a supermassive black hole at its core.
But figuring out how fast the arms rotate or even counting how many there are is tricky, in part because we are embedded in one of its arms and unable to get an outsider’s view. In addition, everything behind the galactic centre is shrouded by a dense wall of stars and dust, blanking out a whole area of the Milky Way map.
“It’s quite difficult to see the actual structure,” says Manuel Silva of the University of Lisbon in Portugal. “I’m a little upset, really, that we don’t know our own galaxy that well.”
A space telescope called Gaia, scheduled for launch later this year, will map the positions and distances of about one billion stars on our side of the Milky Way, plotting the three-dimensional structure in unprecedented detail. But even Gaia won’t be able to pierce the material that blocks our view of the far side.
Instead of trying to look across, Silva and his colleagues suggest looking up, where hundreds of runaway stars fly high above the disc of the galaxy. These stars are born in clusters inside the Milky Way but get ejected during gravitational jostling with other stars. Precise measurements of their velocities, ages and distances would allow astronomers to trace the stellar fugitives back to their homes, even on the far side.
“The idea is that the runaway stars act as signal flares, showing the position of the spiral arm, the same way someone lost in the middle of a dense forest could fire one to the sky to show his or her location to an outsider,” says Silva.
His team traced the origins of about 40 runaway stars, observed by the Hipparcos satellite, ranging from roughly 1000 to 100,000 light years above the galactic plane (arxiv.org/abs/1302.0761v1). Although none of these stars came from the far side, the technique seems to work because the results agreed with previous studies that mapped star clusters in the visible section of the galaxy.
“The idea is a new one, and is an interesting one,” says Jacques Lepine of the University of São Paulo in Brazil, who was not involved in the new study. Comparing Gaia’s view of stars with the runaways will be helpful, he adds. “It is good to have different methods, to compare results. If the results are similar, we get more confident.”
Jacques Vallée of the Canadian National Research Council in Victoria, British Columbia, agrees that the proof of concept is impressive. But that doesn’t stop him fantasising about easier ways: “Wish I had a friend on a planet around a runaway star in the halo, sending me back a photo.”
This article appeared in print under the headline “Runaway stars flesh out Milky Way map”
More on these topics: | 0.818912 | 3.930074 |
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