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When searching for life, scientists first look for an element key to sustaining it: fresh water.
Although today’s Martian surface is barren, frozen and inhabitable, a trail of evidence points to a once warmer, wetter planet, where water flowed freely. The conundrum of what happened to this water is long standing and unsolved. However, new research published in Nature suggests that this water is now locked in the Martian rocks.
Scientists at Oxford’s Department of Earth Sciences, propose that the Martian surface reacted with the water and then absorbed it, increasing the rocks oxidation in the process, making the planet uninhabitable.
Previous research has suggested that the majority of the water was lost to space as a result of the collapse of the planet’s magnetic field, when it was either swept away by high intensity solar winds or locked up as sub-surface ice. However, these theories do not explain where all of the water has gone.
Convinced that the planet’s minerology held the answer to this puzzling question, a team led by Dr Jon Wade, NERC Research Fellow in Oxford’s Department of Earth Sciences, applied modelling methods used to understand the composition of Earth rocks to calculate how much water could be removed from the Martian surface through reactions with rock. The team assessed the role that rock temperature, sub-surface pressure and general Martian make-up, have on the planetary surfaces.
The results revealed that the basalt rocks on Mars can hold approximately 25 per cent more water than those on Earth, and as a result drew the water from the Martian surface into its interior.
Dr Wade said: ‘People have thought about this question for a long time, but never tested the theory of the water being absorbed as a result of simple rock reactions. There are pockets of evidence that together, leads us to believe that a different reaction is needed to oxidise the Martian mantle. For instance, Martian meteorites are chemically reduced compared to the surface rocks, and compositionally look very different. One reason for this, and why Mars lost all of its water, could be in its minerology.
‘The Earth’s current system of plate tectonics prevents drastic changes in surface water levels, with wet rocks efficiently dehydrating before they enter the Earth’s relatively dry mantle. But neither early Earth nor Mars had this system of recycling water. On Mars, (water reacting with the freshly erupted lavas’ that form its basaltic crust, resulted in a sponge-like effect. The planet’s water then reacted with the rocks to form a variety of water bearing minerals. This water-rock reaction changed the rock mineralogy and caused the planetary surface to dry and become inhospitable to life.’
As to the question of why Earth has never experienced these changes, he said: ‘Mars is much smaller than Earth, with a different temperature profile and higher iron content of its silicate mantle. These are only subtle distinctions but they cause significant effects that, over time, add up. They made the surface of Mars more prone to reaction with surface water and able to form minerals that contain water. Because of these factors the planet’s geological chemistry naturally drags water down into the mantle, whereas on early Earth hydrated rocks tended to float until they dehydrate.’
The overarching message of Dr Wade’s paper, that planetary composition sets the tone for future habitability, is echoed in new research also published in Nature, examining the Earth’s salt levels. Co-written by Professor Chris Ballentine of Oxford’s Department of Earth Sciences, the research reveals that for life to form and be sustainable, the Earth’s halogen levels (Chlorine, Bromine and Iodine) have to be just right. Too much or too little could cause sterilisation. Previous studies have suggested that halogen level estimates in meteorites were too high. Compared to samples of the meteorites that formed the Earth, the ratio of salt to Earth is just too high.
Many theories have been put forward to explain the mystery of how this variation occurred, however, the two studies combined elevate the evidence and support a case for further investigation. Dr Wade said ‘Broadly speaking the inner planets in the solar system have similar composition, but subtle differences can cause dramatic differences — for example, rock chemistry. The biggest difference being, that Mars has more iron in its mantle rocks, as the planet formed under marginally more oxidising conditions.’
We know that Mars once had water, and the potential to sustain life, but by comparison little is known about the other planets, and the team are keen to change that.
Dr Wade, said: ‘To build on this work we want to test the effects of other sensitivities across the planets — very little is known about Venus for example. Questions like: what if the Earth had more or less iron in the mantle, how would that change the environment? What if the Earth was bigger or smaller? These answers will help us to understand how much of a role rock chemistry determines a planet’s future fate.
When looking for life on other planets it is not just about having the right bulk chemistry, but also very subtle things like the way the planet is put together, which may have big effects on whether water stays on the surface. These effects and their implications for other planets have not really been explored.’ | 0.838317 | 3.867283 |
"These are galaxies of the Hercules Cluster, an archipelago of island universes a mere 500 million light-years away. Also known as Abell 2151, this cluster is loaded with gas and dust rich, star-forming spiral galaxies but has relatively few elliptical galaxies, which lack gas and dust and the associated newborn stars. The colors in this remarkably deep composite image clearly show the star forming galaxies with a blue tint and galaxies with older stellar populations with a yellowish cast.
Click image for larger size.
The sharp picture spans about 3/4 degree across the cluster center, corresponding to over 6 million light-years at the cluster's estimated distance. Diffraction spikes around brighter foreground stars in our own Milky Way galaxy are produced by the imaging telescope's mirror support vanes. In the cosmic vista many galaxies seem to be colliding or merging while others seem distorted - clear evidence that cluster galaxies commonly interact. In fact, the Hercules Cluster itself may be seen as the result of ongoing mergers of smaller galaxy clusters and is thought to be similar to young galaxy clusters in the much more distant, early Universe.”
Hubble Ultra Deep Field, “Looking To The End Of Time” | 0.866242 | 3.362907 |
|Delivery Type||Delivery length / details|
|Assessment Type||Assessment length / details||Proportion|
|Semester Assessment||Example Sheets. Deadlines are detailed in the Year 2 Example Sheet Schedule distributed by the Department Course Work: Example Sheets||30%|
|Semester Exam||2 Hours End of semester examinations||70%|
After taking this module students should be able to:
- demonstrate an understanding of the basic features of observational astronomy.
- explain the physical processes whereby a section of the ISM collapses to a star.
- demonstrate an understanding of the nature of the final states of stars.
- explain the importance in stellar evolution of the size and rate of a mass loss of stars.
- demonstrate an understanding of the simple physics of galactic systems.
This module considers the physics of stars and galaxies. Starting with a review of laws and the various star classification schemes used in astronomy, the module describes the methods used to determine the distance of stars and hence their luminosity, radii and mass. A description of the Herzspring-Russell diagram illustrates an account of the physical processes involved in stellar formation and evolution, leading to the end-states of white dwarfs, neutron stars and black holes. The physical properties, structure and morphology of the galaxies are studied. The subject of galactic dynamics is introduced.
Coordinate systems. Magnitudes and Brightness. Absolute and Apparent, Visual and Photometric, Bolometric Magnitudes. Stellar distances. Mass-luminosity relation. Introduction to the Hertzsprung-Russell diagram.
STAR FORMATION AND MAIN SEQUENCE
Interstellar medium. Conditions for gravitational collapse of a molecular cloud. Free fall time, hydrostatic equilibrium. The virial theorem, protostar temperatures, complications beyond the simple theory. Observations of star formation, T-Tauri stars. Entry to the Main Sequence. Energy sources in stars. The nature of matter under stellar core conditions. Hydrogen Burning in MS stars. The CN cycle and p-p chain. Energy transport.
Post-main sequence evolution for low and high mass stars. The end states of stars: Black holes, neutron stars, white dwarfs. Supernovae, planetary nebulae.
Structure of the Galaxy: core, spiral arms, halo, clusters.
The virial equation, hidden mass. Types of galaxies: spiral, elliptical, irregular.
Active galaxies: Seyfert, quasars.
Introductory skills for using the Internet and other electronic sources of information.
This module is at CQFW Level 5 | 0.881266 | 3.193354 |
Solar Orbiter will orbit our nearest star, the Sun, observing it up close. It will take the first-ever direct images of its poles, while also studying the inner heliosphere – the bubble-like region around the Sun created by the stream of energised, charged particles released in the solar wind.
At its closest, Solar Orbiter will come within about 42 million km of the Sun: closer than the scorched planet Mercury, just over a quarter of the average distance between Earth and the Sun, and closer than any European spacecraft in history.
To get it into this unique orbit at the centre of the Solar System, edging close to the Sun’s poles instead of orbiting in a ‘flat’ plane, like the planets, teams at mission control in Darmstadt, Germany, have planned an intricate path.
Solar Orbiter is due to launch from Cape Canaveral, Florida, on an Atlas V 411 rocket supplied by NASA in early February. Once it has separated from the launch vehicle, a 22- minute automatic activation sequence takes place, after which point the control team takes over the reins for the Launch and Early Orbit Phase (LEOP).
These early moments in the life of a mission are critical. It is now that the spacecraft wakes up, extends its solar arrays and teams on the ground check its health after the rigours of launch.
Elements of Solar Orbiter’s science instruments are located along a 4.4 metre ‘boom’, which keeps them away from the main body of the spacecraft and any potential interference. This boom should be deployed before certain chemical thrusters are fired, which have the potential to contaminate the instruments during manoeuvres.
Once Solar Orbiter’s systems and instruments are up and running, it enters into the ‘cruise phase’, which will last until November 2021. During this time, it will perform two gravity-assist manoeuvres around Venus and one around Earth to alter the spacecraft’s trajectory, guiding it towards the innermost regions of the Solar System.
The first close solar pass will take place at the end of March 2022 at around a third of the distance between Earth and the Sun. At this point, the spacecraft will be in an elliptical orbit that initially takes 180 days to complete, making a close approach of the Sun every six months.
An orbit with a view
Solar Orbiter’s path will see it travel out of the ‘plane of the ecliptic’. So, instead of orbiting in the same flat plane around the Sun as the planets, moons and minor bodies of the Solar System, it will ‘leap’ up from the solar equator, delivering views of the Sun’s polar regions that have never been seen before.
To do this, Solar Orbiter will not travel in a ‘fixed’ orbit. Instead, the spacecraft will follow a constantly changing elliptical path that will be continually tilted and squeezed, edging it higher and higher and closer to the Sun’s poles.
As such, the spacecraft’s orbit has been chosen to be ‘in resonance’ with Venus, which means that it will return to the planet’s vicinity every few orbits and can again use the planet’s gravity to alter or tilt its orbit.
While Solar Orbiter initially orbits in the same ‘flat’ plane as the planets of the Solar System, each encounter with Venus will increase its inclination. This means that each time Solar Orbiter encounters the Sun, it will be looking at it from a different perspective.
By the end of 2021, the spacecraft will reach its first nominal orbit for science, which is set to last for four years. During this time, Solar Orbiter will reach 17° degrees of inclination, allowing the spacecraft to capture high-resolution images of the Sun’s poles, for the first time.
During its proposed extended mission phase, Solar Orbiter would lift into an even higher inclination orbit. At 33° above the solar equator, the polar regions would come even more directly into view.
Data gathered by Solar Orbiter will be stored on the spacecraft, then beamed (or, ‘downlinked’) to Earth during eight-hour communication windows, via the 35 m Malargüe ground station in Argentina.
Other Estrack stations such as New Norcia in Australia and Cebreros in Spain will act as backups.
Handling the heat
To survive getting so up-close and personal with our star, experiencing a maximum temperature of 520 degrees Celsius and receiving a barrage of intense radiation, Solar Orbiter’s main body and vital instruments will be protected by a titanium heat shield that will face the Sun at all times.
Even the spacecraft’s solar panels, designed to take in energy from the Sun, will need to be protected. As Solar Orbiter edges closer to the giant ball of heat and radiation, its panels – sticking out either side of the spacecraft, bringing it to 18.9 m across – will need to tilt away from the Sun, limiting the amount of light they take in to ensure they do not overheat. | 0.837514 | 3.795798 |
The appearance of a massive white cap on Uranus may seem alarming, but as planetary scientists are learning, this is what a prolonged summer looks like on the remote ice giant.
Ice giants Uranus and Neptune have water-rich interiors coated with hydrogen, helium, and a pinch of methane, the latter of which gives these outer planets their distinctive cyan complexion. Unlike Earth, where seasons last just a few months, Neptune and Uranus experience seasons that last for decades, resulting in strange and intense atmospheric phenomena.
New images released by the Outer Planet Atmospheres Legacy (OPAL) program highlight a evolving atmospheric events on both ice giants, namely an extended white cap over Uranus’ north pole and a new dark vortex on Neptune. A long-term side project of the Hubble program, OPAL is an annual effort to map these two planets when their orbital paths bring them closest to Earth. The new data, captured during the autumn of 2018, are providing important new insights into the seasonal variations on both Neptune and Uranus.
“The yearly observations are helping us to understand the frequency of storms, as well as their longevity,” Amy Simon, a scientist at NASA’s Goddard Space Flight Center who leads the OPAL mission, told Gizmodo. “That’s important because these planets are quite far from the Sun, so this will help constrain how they are forming and more about the internal heat and structure of these planets. Most of the extrasolar planets that have been found are this size of planet, though at all sorts of distances from their parent stars.”
The large white cap strewn over the north pole of Uranus is particularly dramatic. The likely cause of this feature has to do with the planet’s unique tilt, which causes sunlight to shine directly onto the north polar regions for an extended period of time during the summer. It’s currently mid-summer at Uranus’ north pole, resulting in the protracted white cap.
“The November 2018 image of Uranus occurs at a time 10 years after the equinox, when the northern hemisphere was just emerging into spring sunlight after spending decades in polar winter,” Leigh Fletcher, an astronomer at the University of Leicester, told Gizmodo. “Back in 2007, there didn’t appear to be anything like this polar cap over the springtime pole. But as time progressed, a reflective band—whitish against Uranus’ blue hues—began to appear encircling the north pole. And now, 10 years on, that band has turned into a thick polar cap of aerosols that’s hiding the deeper polar region from view.”
Fletcher said it’s a “spectacular example of seasonal change” on this ice giant, with “the aerosol cap evolving as spring becomes summer.” The exact causes of these aerosol changes, he said, remain a mystery, with possibilities including warming temperatures, unusual chemistry, some large-scale atmospheric circulation pattern, or a combination of all these.
“Thankfully we’re not too far away from having an answer, as the James Webb Space Telescope will be able to diagnose the temperatures and chemistry responsible for these reflectivity changes that Hubble has been monitoring,” added Fletcher.
Patrick Irwin, a planetary scientist at Oxford University, said the phenomenon is not a storm, as NASA described it in its release. Rather, “it’s caused mainly—at least in our models—by a lowering of the methane abundance above the main cloud deck accompanied by a possible slight increase in the haze opacity,” he told Gizmodo.
Simon thought the expanded Uranian polar feature was cool, but “more interesting to me is that bright storm just below it,” she told Gizmodo. “That particular storm had flared up and was visible in small ground-based telescopes just prior to these observations, which shows how quickly they can change.”
Looking at the new Neptune image, it appears that a dark vortex has once again reared its ugly—yet fascinating—head. The new anti-cyclonic storm, seen at the top center of the photo above, is about 11,000 kilometers (6,800 miles) across. This is now the fourth dark vortex observed by Hubble since 1993. Two of these storms were observed by the Voyager 2 probe during its flyby of the system in 1989. Taken together, these observations affirm the transient and recurring nature of these storms. A polar vortex observed in 2016, for example, has largely faded away.
“The Neptune dark spot is much larger than the one we saw a few years ago, and is comparable in size to the Voyager Great Dark Spot seen in 1989,” said Simon. “This is also the first time we could see the region before a storm of that size formed, so that will help us in modeling the formation process.”
The causes of these dark spots is a mystery, but because they’re only seen at the bluest wavelengths, “my money is on some sort of coloration of the clouds,” said Irwin.
Often overshadowed by their larger cousins, Jupiter and Saturn, these distant ice giants are proving to be fascinating in their own right. We now await next year’s OPAL observations with much anticipation. | 0.853606 | 3.928287 |
This is an artist's impression of a massive neutron star's pulse being delayed by the passage of a white dwarf star between the neutron star and Earth. Astronomers have detected the most massive neutron star to date due to this delay.
The European Southern Observatory's VISTA telescope captured a stunning image of the Large Magellanic Cloud, one of our nearest galactic neighbors. The near-infrared capability of the telescope showcases millions of individual stars.
Astronomers believe Comet C/2019 Q4 could be the second known interstellar visitor to our solar system. It was first spotted on August 30 and imaged by the Canada-France-Hawaii Telescope on Hawaii's Big Island on September 10, 2019.
A star known as S0-2, represented as the blue and green object in this artist's illustration, made its closest approach to the supermassive black hole at the center of the Milky Way in 2018. This provided a test for Einstein's theory of general relativity.
This is a radio image of the Milky Way's galactic center. The radio bubbles discovered by MeerKAT extend vertically above and below the plane of the galaxy.
A kilanova was captured by the Hubble Space Telescope in 2016, seen here next to the red arrow. Kilanovae are massive explosions that create heavy elements like gold and platinum.
This is an artist's depiction of a black hole about to swallow a neutron star. Detectors signaled this possible event on August 14.
This artist's illustration shows LHS 3844b, a rocky nearby exoplanet. It's 1.3 times the mass of Earth and orbits a cool M-dwarf star. The planet's surface is probably dark and covered in cooled volcanic material, and there is no detectable atmosphere.
An artist's concept of the explosion of a massive star within a dense stellar environment.
Galaxy NGC 5866 is 44 million light-years from Earth. It appears flat because we can only see its edge in this image captured by NASA's Spitzer Space Telescope.
The Hubble Space Telescope took a dazzling new portrait of Jupiter, showcasing its vivid colors and swirling cloud features in the atmosphere.
This is an artist's impression of the ancient massive and distant galaxies observed with ALMA.
Glowing gas clouds and newborn stars make up the Seagull Nebula in one of the Milky Way galaxy's spiral arms.
An artist's concept of what the first stars looked like soon after the Big Bang.
Spiral galaxy NGC 2985 lies roughly over 70 million light years from our solar system in the constellation of Ursa Major.
Early in the history of the universe, the Milky Way galaxy collided with a dwarf galaxy, left, which helped form our galaxy's ring and structure as it's known today.
An artist's illustration of a thin disc embedded in a supermassive black hole at the center of spiral galaxy NGC 3147, 130 million light-years away.
Hubble captured this view of a spiral galaxy named NGC 972 that appears to be blooming with new star formation. The orange glow is created as hydrogen gas reacts to the intense light streaming outwards from nearby newborn stars.
This is jellyfish galaxy JO201.
The Eta Carinae star system, located 7,500 light-years from Earth, experienced a great explosion in 1838 and the Hubble Space Telescope is still capturing the aftermath. This new ultraviolet image reveals the warm glowing gas clouds that resemble fireworks.
'Oumuamua, the first observed interstellar visitor to our solar system, is shown in an artist's illustration.
An artist's impression of CSIRO's Australian SKA Pathfinder radio telescope finding a fast radio burst and determining its precise location.
The Whirlpool galaxy has been captured in different light wavelengths. On the left is a visible light image. The next image combines visible and infrared light, while the two on the right show different wavelengths of infrared light.
Electrically charged C60 molecules, in which 60 carbon atoms are arranged in a hollow sphere that resembles a soccer ball, was found by the Hubble Space Telescope in the interstellar medium between star systems.
These are magnified galaxies behind large galaxy clusters. The pink halos reveal the gas surrounding the distant galaxies and its structure. The gravitational lensing effect of the clusters multiplies the images of the galaxies.
This artist's illustration shows a blue quasar at the center of a galaxy.
The NICER detector on the International Space Station recorded 22 months of nighttime X-ray data to create this map of the entire sky.
NASA's Spitzer Space Telescope captured this mosaic of the star-forming Cepheus C and Cepheus B regions.
This is an artist's rendering of ancient supernovae that bombarded Earth with cosmic energy millions of years ago.
Galaxy NGC 4485 collided with its larger galactic neighbor NGC 4490 millions of years ago, leading to the creation of new stars seen in the right side of the image.
Astronomers developed a mosaic of the distant universe, called the Hubble Legacy Field, that documents 16 years of observations from the Hubble Space Telescope. The image contains 200,000 galaxies that stretch back through 13.3 billion years of time to just 500 million years after the Big Bang.
A ground-based telescope's view of the Large Magellanic Cloud, a neighboring galaxy of our Milky Way. The inset was taken by the Hubble Space Telescope and shows one of the star clusters in the galaxy.
One of the brightest planetary nebulae on the sky and first discovered in 1878, nebula NGC 7027 can be seen toward the constellation of the Swan.
The asteroid 6478 Gault is seen with the NASA/ESA Hubble Space Telescope, showing two narrow, comet-like tails of debris that tell us that the asteroid is slowly undergoing self-destruction. The bright streaks surrounding the asteroid are background stars. The Gault asteroid is located 214 million miles from the Sun, between the orbits of Mars and Jupiter.
The ghostly shell in this image is a supernova, and the glowing trail leading away from it is a pulsar.
Hidden in one of the darkest corners of the Orion constellation, this Cosmic Bat is spreading its hazy wings through interstellar space two thousand light-years away. It is illuminated by the young stars nestled in its core despite being shrouded by opaque clouds of dust, their bright rays still illuminate the nebula.
In this illustration, several dust rings circle the sun. These rings form when planets' gravities tug dust grains into orbit around the sun. Recently, scientists have detected a dust ring at Mercury's orbit. Others hypothesize the source of Venus' dust ring is a group of never-before-detected co-orbital asteroids.
This is an artist's impression of globular star clusters surrounding the Milky Way.
An artist's impression of life on a planet in orbit around a binary star system, visible as two suns in the sky.
An artist's illustration of one of the most distant solar system objects yet observed, 2018 VG18 -- also known as "Farout." The pink hue suggests the presence of ice. We don't yet have an idea of what "FarFarOut" looks like.
This is an artist's concept of the tiny moon Hippocamp that was discovered by the Hubble Space Telescope. Only 20 miles across, it may actually be a broken-off fragment from a much larger neighboring moon, Proteus, seen as a crescent in the background.
In this illustration, an asteroid (bottom left) breaks apart under the powerful gravity of LSPM J0207+3331, the oldest, coldest white dwarf known to be surrounded by a ring of dusty debris. Scientists think the system's infrared signal is best explained by two distinct rings composed of dust supplied by crumbling asteroids.
An artist's impression of the warped and twisted Milky Way disk. This happens when the rotational forces of the massive center of the galaxy tug on the outer disk.
This 1.3-kilometer (0.8-mile)-radius Kuiper Belt Object discovered by researchers on the edge of the solar system is believed to be the step between balls of dust and ice and fully formed planets.
A selfie taken by NASA's Curiosity Mars rover on Vera Rubin Ridge before it moves to a new location.
The Hubble Space Telescope found a dwarf galaxy hiding behind a big star cluster that's in our cosmic neighborhood. It's so old and pristine that researchers have dubbed it a "living fossil" from the early universe.
How did massive black holes form in the early universe? The rotating gaseous disk of this dark matter halo breaks apart into three clumps that collapse under their own gravity to form supermassive stars. Those stars will quickly collapse and form massive black holes.
NASA's Spitzer Space Telescope captured this image of the Large Magellanic Cloud, a satellite galaxy to our own Milky Way galaxy. Astrophysicists now believe it could collide with our galaxy in two billion years.
A mysterious bright object in the sky, dubbed "The Cow," was captured in real time by telescopes around the world. Astronomers believe that it could be the birth of a black hole or neutron star, or a new class of object.
An illustration depicts the detection of a repeating fast radio burst from a mysterious source 3 billion light-years from Earth.
Comet 46P/Wirtanen will pass within 7 million miles of Earth on December 16. It's ghostly green coma is the size of Jupiter, even though the comet itself is about three-quarters of a mile in diameter.
This mosaic image of asteroid Bennu is composed of 12 PolyCam images collected on December 2 by the OSIRIS-REx spacecraft from a range of 15 miles.
This image of a globular cluster of stars by the Hubble Space Telescope is one of the most ancient collections of stars known. The cluster, called NGC 6752, is more than 10 billion years old.
An image of Apep captured with the VISIR camera on the European Southern Observatory's Very Large Telescope. This "pinwheel" star system is most likely doomed to end in a long-duration gamma-ray burst.
An artist's impression of galaxy Abell 2597, showing the supermassive black hole expelling cold molecular gas like the pump of a giant intergalactic fountain.
An image of the Wild Duck Cluster, where every star is roughly 250 million years old.
These images reveal the final stage of a union between pairs of galactic nuclei in the messy cores of colliding galaxies.
A radio image of hydrogen gas in the Small Magellanic Cloud. Astronomers believe that the dwarf galaxy is slowly dying and will eventually be consumed by the Milky Way.
Further evidence of a supermassive black hole at the center of the Milky Way galaxy has been found. This visualization uses data from simulations of orbital motions of gas swirling around about 30% of the speed of light on a circular orbit around the black hole.
Does this look like a bat to you? This giant shadow comes from a bright star reflecting against the dusty disk surrounding it.
Hey, Bennu! NASA's OSIRIS-REx mission, on its way to meet the primitive asteroid Bennu, is sending back images as it gets closer to its December 3 target.
These three panels reveal a supernova before, during and after it happened 920 million light-years from Earth(from left to right). The supernova, dubbed iPTF14gqr, is unusual because although the star was massive, its explosion was quick and faint. Researchers believe this is due to a companion star that siphoned away its mass.
This is an artist's illustration of what a Neptune-size moon would look like orbiting the gas giant exoplanet Kepler-1625b in a star system 8,000 light-years from Earth. It could be the first exomoon ever discovered.
An artist's illustration of Planet X, which could be shaping the orbits of smaller extremely distant outer solar system objects like 2015 TG387.
This is an artist's concept of what SIMP J01365663+0933473 might look like. It has 12.7 times the mass of Jupiter but a magnetic field 200 times more powerful than Jupiter's. This object is 20 light-years from Earth. It's on the boundary line between being a planet or being a brown dwarf.
The Andromeda galaxy cannibalized and shredded the once-large galaxy M32p, leaving behind this compact galaxy remnant known as M32. It is completely unique and contains a wealth of young stars.
Twelve new moons have been found around Jupiter. This graphic shows various groupings of the moons and their orbits, with the newly discovered ones shown in bold.
Scientists and observatories around the world were able to trace a high-energy neutrino to a galaxy with a supermassive, rapidly spinning black hole at its center, known as a blazar. The galaxy sits to the left of Orion's shoulder in his constellation and is about 4 billion light-years from Earth.
Planets don't just appear out of thin air -- but they do require gas, dust and other processes not fully understood by astronomers. This is an artist's impression of what "infant" planets look like forming around a young star.
These negative images of 2015 BZ509, which is circled in yellow, show the first known interstellar object that has become a permanent part of our solar system. The exo-asteroid was likely pulled into our solar system from another star system 4.5 billion years ago. It then settled into a retrograde orbit around Jupiter.
A close look at the diamond matrix in a meteorite that landed in Sudan in 2008. This is considered to be the first evidence of a proto-planet that helped form the terrestrial planets in our solar system.
2004 EW95 is the first carbon-rich asteroid confirmed to exist in the Kuiper Belt and a relic of the primordial solar system. This curious object probably formed in the asteroid belt between Mars and Jupiter before being flung billions of miles to its current home in the Kuiper Belt.
The NASA/ESA Hubble Space Telescope is celebrating its 28th anniversary in space with this stunning and colorful image of the Lagoon Nebula 4,000 light-years from Earth. While the whole nebula is 55 light-years across, this image only reveals a portion of about four light-years.
This is a more star-filled view of the Lagoon Nebula, using Hubble's infrared capabilities. The reason you can see more stars is because infrared is able to cut through the dust and gas clouds to reveal the abundance of both young stars within the nebula, as well as more distant stars in the background.
The Rosette Nebula is 5,000 light-years from Earth. The distinctive nebula, which some claim looks more like a skull, has a hole in the middle that creates the illusion of its rose-like shape.
KIC 8462852, also known as Boyajian's Star or Tabby's Star, is 1,000 light-years from us. It's 50% bigger than our sun and 1,000 degrees hotter. And it doesn't behave like any other star, dimming and brightening sporadically. Dust around the star, depicted here in an artist's illustration, may be the most likely cause of its strange behavior.
This inner slope of a Martian crater has several of the seasonal dark streaks called "recurrent slope lineae," or RSL, that a November 2017 report interprets as granular flows, rather than darkening due to flowing water. The image is from the HiRISE camera on NASA's Mars Reconnaissance Orbiter.
This artist's impression shows a supernova explosion, which contains the luminosity of 100 million suns. Supernova iPTF14hls, which has exploded multiple times, may be the most massive and longest-lasting ever observed.
This illustration shows hydrocarbon compounds splitting into carbon and hydrogen inside ice giants, such as Neptune, turning into a "diamond (rain) shower."
This striking image is the stellar nursery in the Orion Nebula, where stars are born. The red filament is a stretch of ammonia molecules measuring 50 light-years long. The blue represents the gas of the Orion Nebula. This image is a composite of observation from the Robert C. Byrd Green Bank Telescope and NASA's Wide-field Infrared Survey Explore telescope. "We still don't understand in detail how large clouds of gas in our Galaxy collapse to form new stars," said Rachel Friesen, one of the collaboration's co-Principal Investigators. "But ammonia is an excellent tracer of dense, star-forming gas."
This is an illustration of the Parker Solar Probe spacecraft approaching the sun. The NASA probe will explore the sun's atmosphere in a mission that begins in the summer of 2018.
See that tiny dot between Saturn's rings? That's Earth, as seen by the Cassini mission on April 12, 2017. "Cassini was 870 million miles away from Earth when the image was taken," according to NASA. "Although far too small to be visible in the image, the part of Earth facing Cassini at the time was the southern Atlantic Ocean." Much like the famous "pale blue dot" image captured by Voyager 1 in 1990, we are but a point of light when viewed from the furthest planet in the solar system.
NASA's Hubble Space Telescope, using infrared technology, reveals the density of stars in the Milky Way. According to NASA, the photo -- stitched together from nine images -- contains more than a half-million stars. The star cluster is the densest in the galaxy.
This photo of Saturn's large icy moon, Tethys, was taken by NASA's Cassini spacecraft, which sent back some jaw-dropping images from the ringed planet.
This is what Earth and its moon look like from Mars. The image is a composite of the best Earth image and the best moon image taken on November 20, 2016, by NASA's Mars Reconnaissance Orbiter. The orbiter's camera takes images in three wavelength bands: infrared, red and blue-green. Mars was about 127 million miles from Earth when the images were taken.
PGC 1000714 was initially thought to be a common elliptical galaxy, but a closer analysis revealed the incredibly rare discovery of a Hoag-type galaxy. It has a round core encircled by two detached rings.
NASA's Cassini spacecraft took these images of the planet's mysterious hexagon-shaped jetstream in December 2016. The hexagon was discovered in images taken by the Voyager spacecraft in the early 1980s. It's estimated to have a diameter wider than two Earths.
A dead star gives off a greenish glow in this Hubble Space Telescope image of the Crab Nebula, located about 6,500 light years from Earth in the constellation Taurus. NASA released the image for Halloween 2016 and played up the theme in its press release. The agency said the "ghoulish-looking object still has a pulse." At the center of the Crab Nebula is the crushed core, or "heart" of an exploded star. The heart is spinning 30 times per second and producing a magnetic field that generates 1 trillion volts, NASA said.
Peering through the thick dust clouds of the galactic bulge, an international team of astronomers revealed the unusual mix of stars in the stellar cluster known as Terzan 5. The new results indicate that Terzan 5 is one of the bulge's primordial building blocks, most likely the relic of the very early days of the Milky Way.
An artist's conception of Planet Nine, which would be the farthest planet within our solar system. The similar cluster orbits of extreme objects on the edge of our solar system suggest a massive planet is located there.
An illustration of the orbits of the new and previously known extremely distant Solar System objects. The clustering of most of their orbits indicates that they are likely be influenced by something massive and very distant, the proposed Planet X.
Say hello to dark galaxy Dragonfly 44. Like our Milky Way, it has a halo of spherical clusters of stars around its core.
A classical nova occurs when a white dwarf star gains matter from its secondary star (a red dwarf) over a period of time, causing a thermonuclear reaction on the surface that eventually erupts in a single visible outburst. This creates a 10,000-fold increase in brightness, depicted here in an artist's rendering.
Gravitational lensing and space warping are visible in this image of near and distant galaxies captured by Hubble.
At the center of our galaxy, the Milky Way, researchers discovered an X-shaped structure within a tightly packed group of stars.
Meet UGC 1382: What astronomers thought was a normal elliptical galaxy (left) was actually revealed to be a massive disc galaxy made up of different parts when viewed with ultraviolet and deep optical data (center and right). In a complete reversal of normal galaxy structure, the center is younger than its outer spiral disk.
NASA's Hubble Space Telescope captured this image of the Crab Nebula and its "beating heart," which is a neutron star at the right of the two bright stars in the center of this image. The neutron star pulses 30 times a second. The rainbow colors are visible due to the movement of materials in the nebula occurring during the time-lapse of the image.
The Hubble Space Telescope captured an image of a hidden galaxy that is fainter than Andromeda or the Milky Way. This low surface brightness galaxy, called UGC 477, is over 110 million light-years away in the constellation of Pisces.
On April 19, NASA released new images of bright craters on Ceres. This photo shows the Haulani Crater, which has evidence of landslides from its rim. Scientists believe some craters on the dwarf planet are bright because they are relatively new.
This illustration shows the millions of dust grains NASA's Cassini spacecraft has sampled near Saturn. A few dozen of them appear to have come from beyond our solar system.
This image from the VLT Survey Telescope at ESO's Paranal Observatory in Chile shows a stunning concentration of galaxies known as the Fornax Cluster, which can be found in the Southern Hemisphere. At the center of this cluster, in the middle of the three bright blobs on the left side of the image, lies a cD galaxy -- a galactic cannibal that has grown in size by consuming smaller galaxies.
This image shows the central region of the Tarantula Nebula in the Large Magellanic Cloud. The young and dense star cluster R136, which contains hundreds of massive stars, is visible in the lower right of the image taken by the Hubble Space Telescope.
In March 2016, astronomers published a paper on powerful red flashes coming from binary system V404 Cygni in 2015. This illustration shows a black hole, similar to the one in V404 Cygni, devouring material from an orbiting star.
A new map of the Milky Way was released February 24, 2016, giving astronomers a full census of the star-forming regions within our own galaxy. The APEX telescope in Chile captured this survey.
This image shows the elliptical galaxy NGC 4889, deeply embedded within the Coma galaxy cluster. There is a gigantic supermassive black hole at the center of the galaxy.
An artist's impression of 2MASS J2126, which takens 900,000 years to orbit its star, 1 trillion kilometers away.
Caltech researchers have found evidence of a giant planet tracing a bizarre, highly elongated orbit in the outer solar system. The object, nicknamed Planet Nine, has a mass about 10 times that of Earth and orbits about 20 times farther from the sun on average than does Neptune.
An international team of astronomers may have discovered the biggest and brightest supernova ever. The explosion was 570 billion times brighter than the sun and 20 times brighter than all the stars in the Milky Way galaxy combined, according to a statement from The Ohio State University, which is leading the study. Scientists are straining to define the supernova's strength. This image shows an artist's impression of the supernova as it would appear from an exoplanet located about 10,000 light years away.
Astronomers noticed huge waves of gas being "burped" by the black hole at the center of NGC 5195, a small galaxy 26 million light years from Earth. The team believes the outburst is a consequence of the interaction of NGC 5195 with a nearby galaxy.
An artist's illustration shows a binary black hole found in the quasar at the center of the Markarian 231 galaxy. Astronomers using NASA's Hubble Space Telescope discovered the galaxy being powered by two black holes "furiously whirling about each other," the space agency said in a news release.
An artist's impression of what a black hole might look like. In February, researchers in China said they had spotted a super-massive black hole 12 billion times the size of the sun.
Are there are oceans on any of Jupiter's moons? The Juice probe shown in this artist's impression aims to find out. Picture courtesy of ESA/AOES
Astronomers have discovered powerful auroras on a brown dwarf that is 20 light-years away. This is an artist's concept of the phenomenon.
Venus, bottom, and Jupiter shine brightly above Matthews, North Carolina, on Monday, June 29. The apparent close encounter, called a conjunction, has been giving a dazzling display in the summer sky. Although the two planets appear to be close together, in reality they are millions of miles apart.
Jupiter's icy moon Europa may be the best place in the solar system to look for extraterrestrial life, according to NASA. The moon is about the size of Earth's moon, and there is evidence it has an ocean beneath its frozen crust that may hold twice as much water as Earth. NASA's 2016 budget includes a request for $30 million to plan a mission to investigate Europa. The image above was taken by the Galileo spacecraft on November 25, 1999. It's a 12-frame mosaic and is considered the the best image yet of the side of Europa that faces Jupiter.
This nebula, or cloud of gas and dust, is called RCW 34 or Gum 19. The brightest areas you can see are where the gas is being heated by young stars. Eventually the gas burst outward like champagne after a bottle is uncorked. Scientists call this champagne flow. This new image of the nebula was captured by the European Space Organization's Very Large Telescope in Chile. RCW 34 is in the constellation Vela in the southern sky. The name means "sails of a ship" in Latin.
The Hubble Space Telescope captured images of Jupiter's three great moons -- Io, Callisto, and Europa -- passing by at once.
A massive galaxy cluster known as SDSS J1038+4849 looks like a smiley face in an image captured by the Hubble Telescope. The two glowing eyes are actually two distant galaxies. And what of the smile and the round face? That's a result of what astronomers call "strong gravitational lensing." That happens because the gravitational pull between the two galaxy clusters is so strong it distorts time and space around them.
Using powerful optics, astronomers have found a planet-like body, J1407b, with rings 200 times the size of Saturn's. This is an artist's depiction of the rings of planet J1407b, which are eclipsing a star.
A patch of stars appears to be missing in this image from the La Silla Observatory in Chile. But the stars are actually still there behind a cloud of gas and dust called Lynds Dark Nebula 483. The cloud is about 700 light years from Earth in the constellation Serpens (The Serpent).
This is the largest Hubble Space Telescope image ever assembled. It's a portion of the galaxy next door, Andromeda (M31).
NASA has captured a stunning new image of the so-called "Pillars of Creation," one of the space agency's most iconic discoveries. The giant columns of cold gas, in a small region of the Eagle Nebula, were popularized by a similar image taken by the Hubble Space Telescope in 1995.
Astronomers using the Hubble Space pieced together this picture that shows a small section of space in the southern-hemisphere constellation Fornax. Within this deep-space image are 10,000 galaxies, going back in time as far as a few hundred million years after the Big Bang.
Planetary nebula Abell 33 appears ring-like in this image, taken using the European Southern Observatory's Very Large Telescope. The blue bubble was created when an aging star shed its outer layers and a star in the foreground happened to align with it to create a "diamond engagement ring" effect.
This long-exposure image from the Hubble Telescope is the deepest-ever picture taken of a cluster of galaxies. The cluster, called Abell 2744, contains several hundred galaxies as they looked 3.5 billion years ago; the more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang.
This Hubble image looks a floating marble or a maybe a giant, disembodied eye. But it's actually a nebula with a giant star at its center. Scientists think the star used to be 20 times more massive than our sun, but it's dying and is destined to go supernova.
Composite image of B14-65666 showing the distributions of dust (red), oxygen (green), and carbon (blue), observed by ALMA and stars (white) observed by the Hubble Space Telescope.
Artist's impression of the merging galaxies B14-65666 located 13 billion light years-away. | 0.935873 | 3.512062 |
Weak gravitational lensing
While the presence of any mass bends the path of light passing near it, this effect rarely produces the giant arcs and multiple images associated with strong gravitational lensing. Most lines of sight in the universe are thoroughly in the weak lensing regime, in which the deflection is impossible to detect in a single background source. However, even in these cases, the presence of the foreground mass can be detected, by way of a systematic alignment of background sources around the lensing mass. Weak gravitational lensing is thus an intrinsically statistical measurement, but it provides a way to measure the masses of astronomical objects without requiring assumptions about their composition or dynamical state.
Gravitational lensing acts as a coordinate transformation that distorts the images of background objects (usually galaxies) near a foreground mass. The transformation can be split into two terms, the convergence and shear. The convergence term magnifies the background objects by increasing their size, and the shear term stretches them tangentially around the foreground mass.
To measure this tangential alignment, it is necessary to measure the ellipticities of the background galaxies and construct a statistical estimate of their systematic alignment. The fundamental problem is that galaxies are not intrinsically circular, so their measured ellipticity is a combination of their intrinsic ellipticity and the gravitational lensing shear. Typically, the intrinsic ellipticity is much greater than the shear (by a factor of 3-300, depending on the foreground mass). The measurements of many background galaxies must be combined to average down this "shape noise". The orientation of intrinsic ellipticities of galaxies should be almost entirely random, so any systematic alignment between multiple galaxies can generally be assumed to be caused by lensing.
Another major challenge for weak lensing is correction for the point spread function (PSF) due to instrumental and atmospheric effects, which causes the observed images to be smeared relative to the "true sky". This smearing tends to make small objects more round, destroying some of the information about their true ellipticity. As a further complication, the PSF typically adds a small level of ellipticity to objects in the image, which is not at all random, and can in fact mimic a true lensing signal. Even for the most modern telescopes, this effect is usually at least the same order of magnitude as the gravitational lensing shear, and is often much larger. Correcting for the PSF requires building for the telescope a model for how it varies across the field. Stars in our own galaxy provide a direct measurement of the PSF, and these can be used to construct such a model, usually by interpolating between the points where stars appear on the image. This model can then be used to reconstruct the "true" ellipticities from the smeared ones. Ground-based and space-based data typically undergo distinct reduction procedures due to the differences in instruments and observing conditions.
Angular diameter distances to the lenses and background sources are important for converting the lensing observables to physically meaningful quantities. These distances are often estimated using photometric redshifts when spectroscopic redshifts are unavailable. Redshift information is also important in separating the background source population from other galaxies in the foreground, or those associated with the mass responsible for the lensing. With no redshift information, the foreground and background populations can be split by an apparent magnitude or a color cut, but this is much less accurate.
Weak lensing by clusters of galaxiesEdit
Galaxy clusters are the largest gravitationally bound structures in the Universe with approximately 80% of cluster content in the form of dark matter. The gravitational fields of these clusters deflect light-rays traveling near them. As seen from Earth, this effect can cause dramatic distortions of a background source object detectable by eye such as multiple images, arcs, and rings (cluster strong lensing). More generally, the effect causes small, but statistically coherent, distortions of background sources on the order of 10% (cluster weak lensing). Abell 1689, CL0024+17, and the Bullet Cluster are among the most prominent examples of lensing clusters.
The effects of cluster strong lensing were first detected by Roger Lynds of the National Optical Astronomy Observatories and Vahe Petrosian of Stanford University who discovered giant luminous arcs in a survey of galaxy clusters in the late 1970s. Lynds and Petrosian published their findings in 1986 without knowing the origin of the arcs. In 1987, Genevieve Soucail of the Toulouse Observatory and her collaborators presented data of a blue ring-like structure in Abell 370 and proposed a gravitational lensing interpretation. The first cluster weak lensing analysis was conducted in 1990 by J. Anthony Tyson of Bell Laboratories and collaborators. Tyson et al. detected a coherent alignment of the ellipticities of the faint blue galaxies behind both Abell 1689 and CL 1409+524. Lensing has been used as a tool to investigate a tiny fraction of the thousands of known galaxy clusters.
Historically, lensing analyses were conducted on galaxy clusters detected via their baryon content (e.g. from optical or X-ray surveys). The sample of galaxy clusters studied with lensing was thus subject to various selection effects; for example, only the most luminous clusters were investigated. In 2006, David Wittman of the University of California at Davis and collaborators published the first sample of galaxy clusters detected via their lensing signals, completely independent of their baryon content. Clusters discovered through lensing are subject to mass selection effects because the more massive clusters produce lensing signals with higher signal-to-noise.
The projected mass density can be recovered from the measurement of the ellipticities of the lensed background galaxies through techniques that can be classified into two types: direct reconstruction and inversion. However, a mass distribution reconstructed without knowledge of the magnification suffers from a limitation known as the mass sheet degeneracy, where the cluster surface mass density κ can be determined only up to a transformation where λ is an arbitrary constant. This degeneracy can be broken if an independent measurement of the magnification is available because the magnification is not invariant under the aforementioned degeneracy transformation.
Given a centroid for the cluster, which can be determined by using a reconstructed mass distribution or optical or X-ray data, a model can be fit to the shear profile as a function of clustrocentric radius. For example, the singular isothermal sphere (SIS) profile and the Navarro-Frenk-White (NFW) profile are two commonly used parametric models. Knowledge of the lensing cluster redshift and the redshift distribution of the background galaxies is also necessary for estimation of the mass and size from a model fit; these redshifts can be measured precisely using spectroscopy or estimated using photometry. Individual mass estimates from weak lensing can only be derived for the most massive clusters, and the accuracy of these mass estimates are limited by projections along the line of sight.
Cluster mass estimates determined by lensing are valuable because the method requires no assumption about the dynamical state or star formation history of the cluster in question. Lensing mass maps can also potentially reveal "dark clusters," clusters containing overdense concentrations of dark matter but relatively insignificant amounts of baryonic matter. Comparison of the dark matter distribution mapped using lensing with the distribution of the baryons using optical and X-ray data reveals the interplay of the dark matter with the stellar and gas components. A notable example of such a joint analysis is the so-called Bullet Cluster. The Bullet Cluster data provide constraints on models relating light, gas, and dark matter distributions such as Modified Newtonian dynamics (MOND) and Λ-Cold Dark Matter (Λ-CDM).
In principle, since the number density of clusters as a function of mass and redshift is sensitive to the underlying cosmology, cluster counts derived from large weak lensing surveys should be able to constrain cosmological parameters. In practice, however, projections along the line of sight cause many false positives. Weak lensing can also be used to calibrate the mass-observable relation via a stacked weak lensing signal around an ensemble of clusters, although this relation is expected to have an intrinsic scatter. In order for lensing clusters to be a precision probe of cosmology in the future, the projection effects and the scatter in the lensing mass-observable relation need to be thoroughly characterized and modeled.
Galaxy-galaxy lensing is a specific type of weak (and occasionally strong) gravitational lensing, in which the foreground object responsible for distorting the shapes of background galaxies is itself an individual field galaxy (as opposed to a galaxy cluster or the large-scale structure of the cosmos). Of the three typical mass regimes in weak lensing, galaxy-galaxy lensing produces a "mid-range" signal (shear correlations of ~1%) that is weaker than the signal due to cluster lensing, but stronger than the signal due to cosmic shear.
J.A. Tyson and collaborators first postulated the concept of galaxy-galaxy lensing in 1984, though the observational results of their study were inconclusive. It was not until 1996 that evidence of such distortion was tentatively discovered, with the first statistically significant results not published until the year 2000. Since those initial discoveries, the construction of larger, high resolution telescopes and the advent of dedicated wide field galaxy surveys have greatly increased the observed number density of both background source and foreground lens galaxies, allowing for a much more robust statistical sample of galaxies, making the lensing signal much easier to detect. Today, measuring the shear signal due to galaxy-galaxy lensing is a widely used technique in observational astronomy and cosmology, often used in parallel with other measurements in determining physical characteristics of foreground galaxies.
Much like in cluster-scale weak lensing, detection of a galaxy-galaxy shear signal requires one to measure the shapes of background source galaxies, and then look for statistical shape correlations (specifically, source galaxy shapes should be aligned tangentially, relative to the lens center.) In principle, this signal could be measured around any individual foreground lens. In practice, however, due to the relatively low mass of field lenses and the inherent randomness in intrinsic shape of background sources (the "shape noise"), the signal is impossible to measure on a galaxy by galaxy basis. However, by combining the signals of many individual lens measurements together (a technique known as "stacking"), the signal-to-noise ratio will improve, allowing one to determine a statistically significant signal, averaged over the entire lens set.
Galaxy-galaxy lensing (like all other types of gravitational lensing) is used to measure several quantities pertaining to mass:
- Mass density profiles
- Using techniques similar to those in cluster-scale lensing, galaxy-galaxy lensing can provide information about the shape of mass density profiles, though these profiles correspond to galaxy-sized objects instead of larger clusters or groups. Given a high enough number density of background sources, a typical galaxy-galaxy mass density profile can cover a wide range of distances (from ~1 to ~100 effective radii). Since the effects of lensing are insensitive to the matter type, a galaxy-galaxy mass density profile can be used to probe a wide range of matter environments: from the central cores of galaxies where baryons dominate the total mass fraction, to the outer halos where dark matter is more prevalent.
- Mass-to-light ratios
- Comparing the measured mass to the luminosity (averaged over the entire galaxy stack) in a specific filter, galaxy-galaxy lensing can also provide insight into the mass to light ratios of field galaxies. Specifically, the quantity measured through lensing is the total (or virial) mass to light ratio – again due to the insensitivity of lensing to matter type. Assuming that luminous matter can trace dark matter, this quantity is of particular importance, since measuring the ratio of luminous (baryonic) matter to total matter can provide information regarding the overall ratio of baryonic to dark matter in the universe.
- Galaxy mass evolution
- Since the speed of light is finite, an observer on the Earth will see distant galaxies not as they look today, but rather as they appeared at some earlier time. By restricting the lens sample of a galaxy-galaxy lensing study to lie at only one particular redshift, it is possible to understand the mass properties of the field galaxies that existed during this earlier time. Comparing the results of several such redshift-restricted lensing studies (with each study encompassing a different redshift), one can begin to observe changes in the mass features of galaxies over a period of several epochs, leading towards a better understanding of the evolution of mass on the smallest cosmological scales.
- Other mass trends
- Lens redshift is not the only quantity of interest that can be varied when studying mass differences between galaxy populations, and often there are several parameters used when segregating objects into galaxy-galaxy lens stacks. Two widely used criteria are galaxy color and morphology, which act as tracers of (among other things) stellar population, galaxy age, and local mass environment. By separating lens galaxies based on these properties, and then further segregating samples based on redshift, it is possible to use galaxy-galaxy lensing to see how several different types of galaxies evolve through time.
The gravitational lensing by large-scale structure also produces an observable pattern of alignments in background galaxies, but this distortion is only ~0.1%-1% - much more subtle than cluster or galaxy-galaxy lensing. The thin lens approximation usually used in cluster and galaxy lensing does not always work in this regime, because structures can be elongated along the line of sight. Instead, the distortion can be derived by assuming that the deflection angle is always small (see Gravitational Lensing Formalism). As in the thin lens case, the effect can be written as a mapping from the unlensed angular position to the lensed position . The Jacobian of the transform can be written as an integral over the gravitational potential along the line of sight
where is the comoving distance, are the transverse distances, and
is the lensing kernel, which defines the efficiency of lensing for a distribution of sources .
As in the thin-lens approximation, the Jacobian can be decomposed into shear and convergence terms.
Shear correlation functionsEdit
Because large-scale cosmological structures do not have a well-defined location, detecting cosmological gravitational lensing typically involves the computation of shear correlation functions, which measure the mean product of the shear at two points as a function of the distance between those points. Because there are two components of shear, three different correlation functions can be defined:
where is the component along or perpendicular to , and is the component at 45°. These correlation functions are typically computed by averaging over many pairs of galaxies. The last correlation function, , is not affected at all by lensing, so measuring a value for this function that is inconsistent with zero is often interpreted as a sign of systematic error.
The functions and can be related to projections (integrals with certain weight functions) of the dark matter density correlation function, which can be predicted from theory for a cosmological model through its Fourier transform, the matter power spectrum.
Because they both depend on a single scalar density field, and are not independent, and they can be decomposed further into E-mode and B-mode correlation functions. In analogy with electric and magnetic fields, the E-mode field is curl-free and the B-mode field is divergence-free. Because gravitational lensing can only produce an E-mode field, the B-mode provides yet another test for systematic errors.
The E-mode correlation function is also known as the aperture mass variance
where and are Bessel Functions.
An exact decomposition thus requires knowledge of the shear correlation functions at zero separation, but an approximate decomposition is fairly insensitive to these values because the filters and are small near .
Weak lensing and cosmologyEdit
The ability of weak lensing to constrain the matter power spectrum makes it a potentially powerful probe of cosmological parameters, especially when combined with other observations such as the cosmic microwave background, supernovae, and galaxy surveys. Detecting the extremely faint cosmic shear signal requires averaging over many background galaxies, so surveys must be both deep and wide, and because these background galaxies are small, the image quality must be very good. Measuring the shear correlations at small scales also requires a high density of background objects (again requiring deep, high quality data), while measurements at large scales push for wider surveys.
While weak lensing of large-scale structure was discussed as early as 1967, due to the challenges mentioned above, it was not detected until more than 30 years later when large CCD cameras enabled surveys of the necessary size and quality. In 2000, four independent groups published the first detections of cosmic shear, and subsequent observations have started to put constraints on cosmological parameters (particularly the dark matter density and power spectrum amplitude ) that are competitive with other cosmological probes.
For current and future surveys, one goal is to use the redshifts of the background galaxies (often approximated using photometric redshifts) to divide the survey into multiple redshift bins. The low-redshift bins will only be lensed by structures very near to us, while the high-redshift bins will be lensed by structures over a wide range of redshift. This technique, dubbed "cosmic tomography", makes it possible to map out the 3D distribution of mass. Because the third dimension involves not only distance but cosmic time, tomographic weak lensing is sensitive not only to the matter power spectrum today, but also to its evolution over the history of the universe, and the expansion history of the universe during that time. This is a much more valuable cosmological probe, and many proposed experiments to measure the properties of dark energy and dark matter have focused on weak lensing, such as the Dark Energy Survey, Pan-STARRS, and Large Synoptic Survey Telescope.
Weak lensing also has an important effect on the Cosmic Microwave Background and diffuse 21cm line radiation. Even though there are no distinct resolved sources, perturbations on the origining surface are sheared in a similar way to galaxy weak lensing, resulting in changes to the power spectrum and statistics of the observed signal. Since the source plane for the CMB and high-redshift diffuse 21 cm are at higher redshift than resolved galaxies, the lensing effect probes cosmology at higher redshifts than galaxy lensing.
Negative weak lensingEdit
Minimal coupling of general relativity with scalar fields allows solutions like traversable wormholes stabilized by exotic matter of negative energy density. Moreover, Modified Newtonian Dynamics as well as some bimetric theories of gravity consider invisible negative mass in cosmology as an alternative interpretation to dark matter, which classically has a positive mass.
As the presence of exotic matter would bend spacetime and light differently than positive mass, a Japanese team at the Hirosaki University proposed to use "negative" weak gravitational lensing related to such negative mass.
Instead of running statistical analysis on the distortion of galaxies based on the assumption of a positive weak lensing that usually reveals locations of positive mass "dark clusters", these researchers propose to locate "negative mass clumps" using negative weak lensing, i.e. where the deformation of galaxies is interpreted as being due to a diverging lensing effect producing radial distortions (similar to a concave lens instead of the classical azimuthal distortions of convex lenses similar to the image produced by a fisheye). Such negative mass clumps would be located elsewhere than assumed dark clusters, as they would reside at the center of observed cosmic voids located between galaxy filaments within the lacunar, web-like large-scale structure of the universe. Such test based on negative weak lensing could help to falsify cosmological models proposing exotic matter of negative mass as an alternative interpretation to dark matter.
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- Hoekstra, H.; Franx, M.; Kuijken, K.; Carlberg, R. G.; Yee, H. K. C. (April 2003). "Lensing by galaxies in CNOC2 fields". Monthly Notices of the Royal Astronomical Society. 340 (2): 609–622. arXiv:astro-ph/0211633. Bibcode:2003MNRAS.340..609H. doi:10.1046/j.1365-8711.2003.06350.x.
- Parker, Laura C.; Hoekstra, Henk; Hudson, Michael J.; van Waerbeke, Ludovic; Mellier, Yannick (November 2007). "The Masses and Shapes of Dark Matter Halos from Galaxy-Galaxy Lensing in the CFHT Legacy Survey". The Astrophysical Journal. 669 (1): 21–31. arXiv:0707.1698. Bibcode:2007ApJ...669...21P. doi:10.1086/521541.
- Sheldon, Erin S.; Johnston, David E.; Frieman, Joshua A.; Scranton, Ryan; McKay, Timothy A.; Connolly, A. J.; Budavári, Tamás; Zehavi, Idit; Bahcall, Neta A.; Brinkmann, J.; Fukugita, Masataka (May 2004). "The Galaxy-Mass Correlation Function Measured from Weak Lensing in the Sloan Digital Sky Survey". The Astronomical Journal. 127 (5): 2544–2564. arXiv:astro-ph/0312036. Bibcode:2004AJ....127.2544S. doi:10.1086/383293.
- Mandelbaum, Rachel; Seljak, Uroš; Kauffmann, Guinevere; Hirata, Christopher M.; Brinkmann, Jonathan (May 2006). "Galaxy halo masses and satellite fractions from galaxy-galaxy lensing in the Sloan Digital Sky Survey: stellar mass, luminosity, morphology and environment dependencies". Monthly Notices of the Royal Astronomical Society. 368 (2): 715–731. arXiv:astro-ph/0511164. Bibcode:2006MNRAS.368..715M. doi:10.1111/j.1365-2966.2006.10156.x.
- Miralda-Escudé, Jordi (October 1991). "The Correlation Function of Galaxy Ellipticities Produced By Gravitational Lensing". Astrophysical Journal. 380: 1–8. Bibcode:1991ApJ...380....1M. doi:10.1086/170555.
- Schneider, P.; van Waerbekere, L.; Kilbinger, M.; Mellier, Y. (December 2002). "Analysis of two-point statistics of cosmic shear". Astronomy and Astrophysics. 396: 1–19. arXiv:astro-ph/0206182. Bibcode:2002A&A...396....1S. doi:10.1051/0004-6361:20021341.
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- Hossenfelder, Sabine (June 2009). Antigravitation. 17th International Conference on Supersymmetry and the Unification of Fundamental Interactions. Boston: American Institute of Physics. arXiv:0909.3456. doi:10.1063/1.3327545.
- Mbarek, S.; Paranjape, M. B. (November 2014). "Negative mass bubbles in de Sitter space-time". Physical Review D. 90 (10): 101502. arXiv:1407.1457. Bibcode:2014PhRvD..90j1502M. doi:10.1103/PhysRevD.90.101502.
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- Piran, Tsvi (November 1997). "On Gravitational Repulsion". General Relativity and Gravitation. 29 (11): 1363–1370. arXiv:gr-qc/9706049. Bibcode:1997GReGr..29.1363P. doi:10.1023/A:1018877928270. | 0.853537 | 4.201861 |
Quarter* ♍ Virgo
Moon phase on 11 June 2054 Thursday is Waxing Crescent, 6 days young Moon is in Virgo.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 5 days on 6 June 2054 at 02:40.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Moon is passing first ∠4° of ♍ Virgo tropical zodiac sector.
Lunar disc appears visually 4.2% wider than solar disc. Moon and Sun apparent angular diameters are ∠1970" and ∠1890".
Next Full Moon is the Strawberry Moon of June 2054 after 8 days on 20 June 2054 at 03:42.
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 6 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 673 of Meeus index or 1626 from Brown series.
Length of current 673 lunation is 29 days, 7 hours and 54 minutes. It is 40 minutes longer than next lunation 674 length.
Length of current synodic month is 4 hours and 50 minutes shorter than the mean length of synodic month, but it is still 1 hour and 19 minutes longer, compared to 21st century shortest.
This lunation true anomaly is ∠316.1°. At the beginning of next synodic month true anomaly will be ∠336°. 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°).
2 days after point of perigee on 8 June 2054 at 21:43 in ♋ Cancer. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 13 days, until it get to the point of next apogee on 24 June 2054 at 17:32 in ♒ Aquarius.
Moon is 363 905 km (226 120 mi) away from Earth on this date. Moon moves farther next 13 days until apogee, when Earth-Moon distance will reach 405 098 km (251 716 mi).
Moon is in ascending node in ♍ Virgo at 07:33 on this date, it crosses the ecliptic from South to North. Moon will follow the northern part of its orbit for the next 13 days to meet descending node on 25 June 2054 at 04:56 in ♒ Aquarius.
At 07:33 on this date the Moon is completing its previous draconic month and is entering the new one.
3 days after previous North standstill on 7 June 2054 at 14:08 in ♊ Gemini, when Moon has reached northern declination of ∠19.164°. Next 9 days the lunar orbit moves southward to face South declination of ∠-19.200° in the next southern standstill on 20 June 2054 at 19:41 in ♑ Capricorn.
After 8 days on 20 June 2054 at 03:42 in ♐ Sagittarius, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.194877 |
One time I ordered a beer then straight away spilled it all over the bar. There was just a tiny sip left in the glass. Not my finest hour (frowny face).
Here is what we think we know about ‘Oumuamua. All our information comes from measurements of the object’s brightness (which oscillates dramatically) and its spectrum (which is reasonably-well characterized):
- It has a stretched-out shape. Exactly how stretched-out is debated, but it’s probably cigar-shaped with a long axis 5 to 10 times longer than the two shorter ones. The dimensions are ballpark: 230 m × 35 m × 35 m (800 ft × 100 ft × 100 ft).
- It spins in about 7 hours but in an irregular way, not along any of its main axes. This is called tumbling and is rare among asteroids and comets.
- Its spectrum is similar to those of primitive, organic-rich objects in the Solar System (certain classes of comets and water-rich asteroids) but without showing any water.
In a previous post I presented a simple origins story for ‘Oumuamua. It went like this: ‘Oumuamua was born in a planet-forming disk around a young star. That same disk also formed two or more gas giant planets. The orbits of the gas giants became unstable and they underwent a violent instability. A huge pile of planetary leftovers — called planetesimals — were launched by the giant planets into interstellar space. ‘Oumuamua is one of those planetesimals. Here is a simulation of this process (the star is at zero (not shown), the big black things are gas giants, small colored dots are planetesimals and the growing rocky planets):
There is a new twist to this story that fixes a small but important problem. Let me explain.
For decades we have expected to find rogue interstellar planetesimals like ‘Oumuamua. After all, we’ve already found rogue planets (see here), and there should be a whole lot more small guys out there than big ones. But we want to know how many are out there, because that number matters (at least to people like me in the planet formation business).
If we know how efficient we are at finding interstellar objects like ‘Oumuamua, we can estimate how abundant they are. We can compare it to the number of stars. Finally, assuming ‘Oumuamua to be a member of a population of such bodies, we can figure out how much mass in planetesimals each star ejects on average.
To do this last part, think of ‘Oumuamua as a pea in a distribution of interstellar peas and pumpkins. There are 1000 peas for every pumpkin. So, by number you should expect to see peas, but one pumpkin has much more mass than a thousand peas. So, if our calculation tells us that there are a million peas, then we know there must be a thousand pumpkins. If we know the mass of a pumpkin then we’re golden.
From this simple calculation I find that, in order to explain the detection of ‘Oumuamua, each star must eject hundreds to thousands of Earth masses in planetesimals! That is such a big number that it makes no sense! A typical planet-forming disk only contains a total of between about ten and a few hundred Earth masses, and it can’t all be ejected! What is going on?
I was confused so I changed approach. I took a closer look at the behavior of planetesimals as they are kicked out of their planetary systems. Planetesimals are kicked around by giant planets 10-100 times or so on their way to getting ejected. But about one in every hundred planetesimals gets really close to a giant planet during this process. So close that it should be tidally disrupted. Disruption happens when the gravity on one side of an object is different enough from the gravity on the other side that is is literally torn to pieces.
We have seen tidal disruption in action. Back in 1992 comet Shoemaker-Levy 9 flew too close to Jupiter and was torn to shreds:
Those pieces eventually fell back onto Jupiter in 1994 (some on my 17th birthday!)
About 1% of planetesimals ejected into interstellar space undergo such close encounters that they must have disrupted like comet Shoemaker-Levy 9. This leads to a new thought: what if ‘Oumuamua is not a planetesimal, but a fragment of a disrupted planetesimal?
‘Oumuamua as a fragment may explain some of its puzzling characteristics. First, it is really stretched-out. Tidal disruption is the process of stretching something out until it breaks, so it’s not a big surprise that the shreds should be stretched-out. Its weird tumbling might also be explained by disruption. And who knows, maybe that type of event could have dried ‘Oumuamua out as well.
If ‘Oumuamua is a fragment it also fixes the problem I pointed out before, that to explain ‘Oumuamua’s detection every star needs to eject hundreds of Earth masses in planetesimals. Let’s go back to thinking of interstellar planetesimals as peas and pumpkins. When planetesimals form, for every thousand peas there is one pumpkin. As those objects were ejected into interstellar space, 99% of them did not change and have the same 1000-to-1 pea to pumpkin ratio. But remember, 1% of planetesimals were torn to pieces. So, let’s take 1% of the pumpkins and shred them into pea-sized pieces. That’s a *lot* of peas. It’s so many that the 1000-to-1 pea to pumpkin ratio is now much higher. If we take that into account, each star only needs to eject about one Earth’s worth of planetesimals to explain ‘Oumuamua’s detection. That is easy to explain. Problem solved.
Here is the main idea:
So there you go: ‘Oumuamua may be a fragment of a planetesimal that was torn to pieces by a gas giant before being ejected into interstellar space. Boom!
Our (updated) paper can be downloaded here.
Questions? Comments? Words of wisdom? | 0.808913 | 3.765322 |
1 . Aditya-L1
Source – Hindu
- Sometime in 2019 or 2020 India will send ISRO’s solar mission Aditya-L1 to a vantage point in space, known as the L1 Lagrange point, to do imaging and study of the sun.
- This launch will happen in the early part of the next solar cycle – an occurrence in which sunspots form on the face of the sun, growing in size and number and eventually diminishing, all over a period of eleven years.
- It will be a mission of many firsts.
- The so-called L1 point is 1.5 million kilometres away.
- Here, due to the delicate balance of gravitational forces, the satellite will require very little energy to maintain its orbit.
- Also it will not be eclipsed from the sun.
- The 1,500-kg class satellite will be programmed to orbit this point and image the sun’s magnetic field from space for the very first time in the world.
- Few other space agencies have successfully placed their satellites at this location.
- Among the few, the Solar and Heliospheric Observatory (SOHO), a NASA-ESA collaboration involving America and Europe, and NASA’s Advanced Composition Explorer (ACE) are at L1 exclusively to study the sun and space weather, respectively.
- Aditya-L1 is expected to be the very first to study from space two months from the time of launch, the magnetic field of the sun’s corona.
- It will be the first 100% Indian mission which will not only negotiate a challenging orbit, but will also benefit the global scientific community in understanding the sun.
- The mission will carry seven payloads,consisting of a coronagraph, equipment that will image the sun using ultraviolet filters, X-ray spectrometers, and particle samplers all being made within the country.
- The largest payload, or instrument, aboard the satellite, will be the Visible Emission Line Coronagraph (VLEC). This can view the sun more closely than has been done before even by SOHO.
- With this advantage, the instrument has the capacity to observe the loop-like magnetic structures that form in the corona, the outer layer of the sun.
- This will be the first experiment to measure the coronal magnetic field from a space platform. This was not even done by SOHO.
- Apart from this, the two in situ particle-detection payloads – Aditya Solar wind Particle EXperiment (ASPEX) and Plasma Analyser Package for Aditya (PAPA) will study aspects that affect space weather. the origin of solar wind ions, their reaction to coronal mass ejections, the distribution of these in the heliosphere – the space around the sun that extends up to Pluto – and so on.
- The payloads alone will weigh close to 250 kg. The biggest of these is the VLEC, about 170 kg. The next is SUIT, weighing around 35 kg; others are much lighter.
2 . Space Activities Bill, 2017
Source – Hindu
What is it?
It is a proposed Bill to promote and regulate the space activities of India. The new Bill encourages the participation of non-governmental/private sector agencies in space activities in India under the guidance and authorisation of the government through the Department of Space.
When, where, who?
The draft was posted on the website of Indian Space Research Organisation (ISRO) on November 21, 2017.
Why has it been posted?
The Bill seeks comments on the draft from stakeholders and the public. ISRO has given a month’s time to read the 20-page draft and send comments.
What does the Bill propose?
- The provisions of this Act shall apply to every citizen of India and to all sectors engaged in any space activity in India or outside India
- A non-transferable licence shall be provided by the Central Government to any person carrying out commercial space activity
- The Central Government will formulate the appropriate mechanism for licencing, eligibility criteria, and fees for licence.
- The government will maintain a register of all space objects (any object launched or intended to be launched around the earth) and develop more space activity plans for the country
- It will provide professional and technical support for commercial space activity and regulate the procedures for conduct and operation of space activity
- It will ensure safety requirements and supervise the conduct of every space activity of India and investigate any incident or accident in connection with the operation of a space activity.
- It will share details about the pricing of products created by space activity and technology with any person or any agency in a prescribed manner.
- If any person undertakes any commercial space activity without authorisation they shall be punished with imprisonment up to 3 years or fined more than ₹1 crore or both.
3 . Constitution Day (National Law Day)
Source – pib
- Constitution Day (National Law Day), also known as Samvidhan Divas, is celebrated in India on 26 November every year to commemorate the adoption of Constitution of India.
- On 26 November 1949, the Constituent Assembly of India adopted the Constitution of India, and it came into effect on 26 January 1950.
- The Government of India declared 26 November as Constitution Day on 19 November 2015 by a gazette notification.
- The Prime Minister of India Narendra Modi made the declaration on 11 October 2015 while laying the foundation stone of the B. R. Ambedkar memorial in Mumbai.
- The year of 2015 was the 125th birth anniversary of Ambedkar, who had chaired the drafting committee of the Constituent Assembly and played a pivotal role in the drafting of the constitution.
- Previously this day was celebrated as Law Day.
- 26 November was chosen to spread the importance of the constitution and to spread thoughts and ideas of Ambedkar. | 0.8403 | 3.532876 |
These days I feel confident saying there are two things I can rely on: 1) the Hubble Space Telescope will continue to reveal amazing things about the Universe around us, and 2) Pluto will continue to surprise us. This week we had both!
Hubble released a new data analysis of two of Pluto’s five moons, Nix and Hydra, that show them to be wobbling all over the place. It might be surprising, but Hubble can’t actually *see* Pluto and its moons in the same way that it sees the brilliant galaxies and nebulae you are used to hearing about. This is because Pluto doesn’t produce any light itself, but rather only reflects what little of the Sun’s light reaches it. As a small, dark, rocky object at a great distance, that’s not much.
However, using the change in the light Hubble receives from the Pluto system over time, astronomers can begin to constrain their best estimates for the size, shape, and motion of Pluto’s moons. The latest data shows that Nix and Hydra are likely oblong, shaped like potatoes, and they are not rotating about an axis of symmetry. So as they orbit around Pluto, the light they reflect appears to change erratically.
NASA’s New Horizons spacecraft is closing in on Pluto as we speak with its closest approach scheduled for July 14, 2015. If all goes well, we’ll know just how chaotic this system really is before the summer is out.
Here’s some more geek from the week:
- This octopus is a pro at hauling its baggage across the ocean floor. [VIDEO]
- The symbiotic relationships between lichens and algae are like soap operas in the sea.
- Seven new frog species discovered in the cloud forests of Brazil.
- Mind-blowing balloon sculptures of animals and insects.
- Turns out getting bug guts off your windshield is actually rocket science.
- Sound waves might be the next big thing in cheese making. [AUDIO]
- The science of making the perfect french fry (or chips to you Brits). Turns out moving to Jupiter might be good.
- How one photographer spent twenty-years trying to make time stand still.
- Toilets in elevators could become a thing. At least in Japan.
- The National Park Service has created a map of the quietest places in the country. [VIDEO]
- The physics of how mountains can sometimes be larger on top. [VIDEO]
- Intense physical analysis of Thor’s Hammer. [WITH VIDEO]
Keep on geeking!
@Summer_Ash, In-house Astrophysicist | 0.80978 | 3.102429 |
Fun stuff: Some astronomical maps and tables of nearby stars and exoplanets.
And Galaxies too... And more !
In the series: Note 1: Some maps, tables of nearby stars, and stuff about Galaxies etc...
Version 0.8, 21 April, 2020.
By Albert van der Sel.
- I hope that especially young folks like this sort of stuff...
- For a few interactive links, you need to have Java.
- Please refresh the page, to see any updates.
1. Some Maps of (nearby) stars:
(Static) Map of nearby stars (< 14 ly)
(Interactive) Map of nearby stars
(Static) Map of nearby stars (< 10 parsec, or 32.6 ly)
(Static) atlasoftheuniverse.com: Map of Nearby stars (< 12.5 ly)
(Static) atlasoftheuniverse.com: Map of Nearby stars (< 50 ly)
(Static) atlasoftheuniverse.com: Map of Nearby stars (< 250 ly)
(Static) Knotted Map of nearby stars (< 14 ly)
(Interactive) Nearby stars - Interactive 3D Rotatable map (You need Java, and activate it)
(Interactive) Nearby stars - Interactive 3D map (up, down, left, right)
(Interactive) Great map of constellations, stars, objects
Suppose we represent the Sun as a ball of 10 cm (= 0.1 m = 0.0001 km).
Then how far is the nearest star, "Proxima Centauri" from the Sun, using the above scale?
The distance of Proxima Centauri to the Sun, is about 4.2 lightyears.
This is about 4.2 * 9.4 * 1012 km = 39.5 * 1012 km.
The real diameter of the Sun is about 1392700 km.
Transforming the diameter of Sun, to the scale of 0.1 m (0.0001 km), we have then as the rescaled distance
of Proxima Centauri to the Sun, as: (0.0001/1392700) * 39.5 * 1012 = (about) 2800 km.
(Note: in the calculation above, all values are in km, It's just a rough calculation,
to show the order of magnitude we are dealing with. So, the number is somewhere around 2500km or something like that).
So, if the Sun would be rescaled to a ball somewhat larger than a tennisball, then
proxima centauri would be about 2800 km (or about 1750 miles) away.
Now, this is only about the nearest star. Yes, the nearest star (except for the Sun, ofcourse).
2. Some Tables of (nearby) stars and exoplanets:
List of Exoplanets (rather complete)
List of Exoplanets
List of Exoplanets
List of Exoplanets
List of Exoplanets
List of Exoplanets
List of important stars
And Ofcourse Wikipedia pages:
List of Exoplanets per period of discovery
Potentially habital exoplanets
3. Looking into the Sky, is looking in the Past:
In Astronomy, the unit to express distances, often is the "lightyear", abbreviated to "ly",
which is the distance that light has travelled in one year of time.
Since light travels with about 300000 km/s in vacuum, the ly is an enormous distance
on a Human scale.
It also means that if you watch the night sky, and you watch for example the star called "Sirius",
which is (only) about 8.6 ly away from us, then you see the light that was send out
8.6 years ago.
In a way, you are looking "in the past", if you watch objects in the nightsky.
Take look at the link below. It's a picture of the "Andromeda" spiral galaxy (also denoted by "M31").
It's about 2.5 million ly away from us.
From Wikipedia: The "Andromeda" spiral galaxy.
So, actually, we are looking at M31 "as it was" 2.5 million years ago.
Suppose "now", somewhere in M31, a heavy star explodes into a Supernova. Suppose that happens
somewhere at the rim of that Galaxy. Then we have to wait for 2.5 million years to observe
a rather bright spot at that location at the rim of M31.
Note 1: the distance of M31 to us, varies slightly in scientific articles. Usually it is listed
as in between 2.2 to 2.56 million ly. Don't worry too much about that.
Note 2: The "disk" of M31 is usually estimated to be about 250000 ly across. This "star island"
is often estimated to contain 300 to 400 * 109 stars.
But, the "halo" (a sort of sphere around it) contains many stars and objects as well.
Astronomers also often use the "parsec" (pc) to express distances in the Universe.
1 parsec is about 3.26 ly.
So, if an astronomer would tell you that an object is about 100 Mpc away (100 Mega parsec),
then it would be about 100 * 1000000 * 3.26 = (about) 326000000 ly = 3.26 * 108 ly distance.
It's not really neccessary (for the scope of this note) to explore the origin of the "parsec",
but maybe you like to Google on it.
4. Relative sizes of various Stars:
Although the smaller e.g. K- and M-types of stars (like red dwarfs) seem to be very abundant,
there exists a large "variety" of stars, in terms of Mass, Luminocity, Spectral Class, and size.
Sure, the extremely large stars, are in a strong minority compared to the main stream stars.
However, it's fun to see some comparisons in size, of the larger, to extremely large, stars.
If the diameter of our Sun is denoted by "Rsol", then a few of the largest stars
observed so far, would be:
UY Scuti: about 1700 * Rsol, Rigel: about 80 * Rsol, VY Canis Majoris: about 1400 * Rsol
Betelgeuse: about 850 * Rsol, etc.. etc..
Although the sizes with comparision to the Sun, can be very large (like 1500 * Rsol), their Masses
usually have not such extremely values. For example, It's rather rare if a (normal) star would have
a mass more than 30 * the mass of the Sun (for good reasons from Physics).
Indeed, the "density" of such stars is much less compared to the more mundane main stream stars.
However, masses of the Largest ones, which are over 30 * Mass (Sun), actually do exist.
It's generally assumed that large stars, with a mass near or over 8 * Mass (Sun), may end up
as a Neutron Star, after they end their "star-life" in a Supernova explosion.
Even more heavier stars, may end into a Black Hole. It must be said however, that such numbers seem not to have
full (?) consensus among astronomers and other scientists in related fields.
So, I like to be a bit carefull here.
Now, Chandrasekhar determined, on the basis of the theory of Gravity, and Quantum Mechanics,
that there exists a limit of about 1.4 Solar Mass (with respect to the collapsing core).
If the mass of the collapsing core < 1.4 Solar Mass, we probably end up with a white dwarf star.
If the mass > 1.4 Solar Mass, then there is a good chance for a route to become a Neutron star.
See the links below for some nice illustrations, about extreme sizes of some famous stars.
Size of the Sun, compared to Arcturus and Antares
Comparison from "schoolsobservatory.org"
Comparison from "jpl.nasa.gov"
5. Some Maps of our Milkyway (our own Spiral Galaxy, we live in):
There are 3 main types of Galaxies (or 4, if you would subdivide the Spiral Galaxies
into Spirals- and Barred-Spirals).
The main types are: Elliptical (shaped), Spiral (shaped), and Irregular (no obvious structure).
I must immediately say that there are certainly more ways to characterize Galaxies.
Like for example some folks characterize a certain system as a "lenticular" system.
And indeed, some other types exists too.
However, the three main types listed above, are the most prominent ones.
Our own Milky way is a Spiral Galaxy, with a rather dense "core", and spiralling "arms",
which contain stars, gas, and dust clouds.
Here are some nice "maps" illustrating the structure of our own Milky way.
(Static) Map 1
(Static) Map 2
(Interactive) Map 3
(Static) Map 4
(Static) Map 5 Illustration of Globular clusters around the Milky way.
And next we have a striking picture, which zooms in to the position of the Sun
in the local Spiral arms (the yellow circle represents the Sun):
(Static) Zoomed in position of the Sun.
- Our Milky way, has the appearance of a disk, having spiral arms around a dense, and luminous center of stars.
Spherically around the disk, there is a Halo with older stars, and somewhere in the order of
150-200 or so, Globular clusters.
The disk is about 105 ly across, and it is estimated that our Milky way contains
close to 200 * 109 stars (spiral arms plus center plus halo).
-Especially in the spiral arms, we find gas and dust clouds, and a large variety of young
and older stars. It has been found that new stars are mainly born in those spiral arms.
But between those arms, there are many stars as well, but the most of the youngest and brightest ones,
are in the arms.
-It seems rather typical, that spiral galaxies, have a number of smaller, compact, "globular clusters"
distributed around them. Compared to a Galaxy, they are rather small, containing
several tens of thousands-, to several hundreds of thousends-, or sometimes close to a million stars.
So they are really not that small, but compared to the Galaxy as a whole, where they are near,
they seem relatively small.
They live in the Halo, and in the disk, of our Milky way. They have certain orbits around the Galaxy.
Typically, they contain mostly "low metallic" stars, which strongly suggest that they are
Tip: why don't you Google on "types of galaxies", and see the most remarkable
and beautiful galaxies yourself ?
6. Some Images of Superclusters of Galaxies ("Milky ways"):
The Individual Galaxies, most often are part of a "Cluster" of galaxies, which themselves form Superclusters.
The Observable Universe resembles a sort of "soap bubbles" type of large scale structure, with large
empty voids, and strings and/or walls of Superclusters (consisting of member Galaxies).
Some of the images below, try to illustrate this "large scale structure".
The nearest Superclusters (1) (atlas of the Universe)
The nearest Superclusters (2) (atlas of the Universe)
The 2MASS redshift survey
Our local patch in the cluster (about 10 million ly accross), is the "The Local Group",of which
the Galaxies M33, M31 (Andromeda) and our own Milky way are the most prominent members.
However, a large number of smaller dwarf- and elliptical systems, are distributed among this region.
The figure in the link below, nicely illustrates the Local Group.
Our local patch: The Local Group of Galaxies.
Tip: For very large structures: You might like to Google on "The Sloan great wall" and the "BOSS great wall"
as observed superstructures (of clusters) in the Universe. Great stuff to read.
7. A few words on modern Black Hole theories:
The next phrase is not entirely correct, but if you would approach a black hole (ofcourse still being
at a large distance), it would resemble a pitch black "spherical" object.
It's indeed often said, that at the "event horizon" (or "Schwarzschild radius"), gravity is so high
that even light cannot escape anymore.
Some folks argue (or have good reasons) to rephrase that to: SpaceTime near the Horizon is so streched,
so that light is so extremely far redshifted, that it becomes "invisible".
Then it only "looks like" as if Gravity is so strong that even light cannot escape anymore.
Indeed, talking about Black Holes can be confusing at certain moments. However, it remains true
that from the "outside", near the Horizon, gravitational effects, like strong Spacetime curvature, time dillatation,
and other effects we expect to happen according General Relativity, seems all to be true.
Many different theoretical studies have been done, and still are intensively active, on the "nature"
of a Black hole. Classically, one important tool has always been Einstein's General Theory of Relativity (GTR).
But, many modern insights and theories have emerged the last decades.
1. An example of a modern approach:
One important other approach, using elements from Thermodynamics, surely produced
additional insights. For example, take a look at the Bekenstein-Hawking relation below:
kB * A
4 * Lp
The most important elements here, are "S" (entropy) and "A" (surface area of the Black Hole).
We can ignore the other parameters (kB and Lp), for now.
The notion of "Entropy" (S) is often interpreted as a measure of the number of microstates that "sits"
behind a particular macrostate.
Many folks also interpret this as a measure of "information". The remarkable thing about the
upper formula is, that this Black Hole entropy seems to be proportional to the Surface Area "A"
of the Black Hole (at the horizon).
Note the remarkable fact, that this view is unrelated to the interior of the Black Hole.
It's just the area defined by the horizon, which plays a role.
It's indeed very remarkable ! Contrary: If a Black Hole would be a "singularity", then many folks often
argued that when matter is sucked in into the Black Hole, information would be lost forever.
Indeed, for many physicists a true infinitely small "singularity" was never much appealing.
However, the Bekenstein-Hawking relation might suggest that information (in whatever form)
might get "stored" (?) at (or near) the Horizon (the surface "A").
This model is actually rather close to the socalled "Firewall model" of Black Holes.
In a way, the more microstates a system has (larger Entropy), the more information it caries.
You might wonder why this is so. An analogy from ordinary datatransmission (networking) might help.
A monotone signal has no intrinsic information. But if you "modulate" it, by varying the frequency
or amplitude, then it can carry information. As it were, the number of "states" have increased.
You might thus go as far, as saying that when a Black Hole aggresively sucks up matter,
then "A" would increase, and so does it's entropy, and so does the "information".
All in all, I have not mentioned a lot here, but I tell you that it is quite a different approach
compared to the idea of an infinite small singularity, with a "Schwarzschild radius" (or event horizon)
which "surrounds" it.
2. The semi-classical approach, using Relativity Theory:
It's also important to take a look at the (semi-) Classical approach using General Relativity.
It's still very important, since many physicist uses GTR, or derived theories (like EiBI gravity),
which still up to this day, produces stunning results.
In a nutshell, the semi-classical approach goes a bit like this:
SpaceTime is a 4D continuum, and Einstein uses a lot of differential Geometry (a sort of Math),
to search for his answers. One main result is, that SpaceTime "warps" or "is curved" when Mass-Energy
is near. Curved SpaceTime can be associated with Gravity.
When there is no Mass-Energy, or we are very far from it, SpaceTime is "flat" (and no Gravity).
This is all reflected in his General "Field Equations".
Einstein's field equations provide for a framework, but not a specific solution like a "metric",
for example, to calculate a distance in a certain SpaceTime.
Schwarzschild found a solution, that is a "way" to calculate distances, and a general description of SpaceTime,
which conforms to Einstein's equations.
But there are also very interesting collaries to his findings. It became clear (in this semi-classical theory),
that any mass has a "critical radius", meaning that if you would extremely compress that mass
under that treshold, it would fully collapse into a Black Hole. Intially, the interpretation
was such, that at that "critical radius", gravitation would be so strong that even light could
not escape anymore.
In somewhat "better" words, the "mass-density" would be so high, that the surrounding SpaceTime would be so
streched, that even light would so redshifted, that it does not show anymore.
For that critical radius, called Rs, Schwarzschild found that the relation
to any Mass "M" is:
Rs = 2 G M / c2
Where "G" is the gravitational constant, "c" is the speed of light, and "M" is the mass inside
the critical radius "Rs".
For any mass "M", a corresponding critical Schwartzschild Radius rs (or "R") can be calculated,
which defines the Horizon, and effectively says when then mass becomes a "black hole".
For example, if the Sun's Total mass were to be compressed within (about) 2 miles (the Rs for that Mass)
then it would become a black hole. For Earth, we need to compress our planet within 1 cm.
All in all, also the semi-classical theories provided the framework to describe Black Holes.
I must be extremely carefull in not suggesting of the existence of any "structure" inside the Black Hole.
It's simply not known.
-The classical model seems to point at an infinitely small "singularity" within the critical radius (Horizon).
-The conjectures of Bekenstein/Hawking seem to suggest a sort of storage of information at or near the Horizon.
At least, a singularity seems to be in conflict with Quantum Theories.
There is a tiny problem perhaps in using phrases as "length stretches", or "SpaceTime stretches"
and that sort of statements.
We know from Special Relativity, that the SpaceTime distance between "events" must be constant.
That requirement has not dropped.
The only thing we can rightfully say is that SpaceTime gets very curved as you approach the critical radius,
And it will even be asymptotic at, or very near, the critical radius.
This means, according to most physicists, SpaceTime is so streched, that light will be infinitely redshifted.
Indeed, also according to GTR, the clock will go slower and slower, nearer and nearer to the Horizon.
In many discussions, it is often said that a remote observer may see a spacecraft to get "spagettified",
as it would get nearer and nearer to the critical radius. The observation however, is indeed correct.
It's correct for a remote observer, since light and time seems to "freeze" for that observer,
when the object get's very near the Horizon.
For that spacecraft itself, it's probably true that other events will take place.
Lastly, I must say that many treatments of Black Holes, consider Mass, Charge, and Angular momentum
at the initial state, and then looks (theoretically) what happens when a Black Hole forms,
when for example a massive star collapses at the end of her life.
Different models go around, like e.g. the Kerr Black Hole, and others.
Even rather exotic models were published. It never found much support in the community (as it seems
to me), but maybe you like to Google on the "Fuzzball" black hole theory.
It's a valid model, or maybe I should say, a valid attempt to explore Black Holes.
3. Now, what has been observed in reality, so far? Here are just a few examples.
Also from my youth, I remember that it was strongly suspected that Cygnus X-1 was likely
to be a black hole. It's a black hole near a (normal) large blue star, and the black hole is
rather brutally sucking material away from it, leading to intense X-ray radiation.
The intense radiation, is produced due to the large acceleration of the material towards
the black hole, in a rotating disk, spiraling towards the black hole.
The radiation was detected during the '60's/'70's of the former century.
Today, almost nobody doubts that we actually have a black hole in this system.
It then would be the first one, that was ever discovered.
It's about 6000 ly away, and the black hole itself is likely to have a mass of (only) 0.8 Solar Mass.
-Massive Black Hole in the Center of our Milky way.
Gradually, it became clearer and clearer, that a very massive Black Hole, sits in the center
of our own spiral galaxy (the Milkyway). It's located at Sagittarius A, the center of the Milky way.
Even stronger: Today, It is generally assumed that having a massive Black Hole at it's center, is a
rather common feature of Spiral Galaxies in general !
For the Milky way: many clues were acumulated. For example, the socalled "S" stars have very close
orbits near that massive black hole, and have enormous speeds in higly rosettic orbits (elliptic with precession).
Using that data, it can be inferred that this Black Hole has a mass of around 4 million Solar Masses.
If you see the data on the orbit of star "S2" around the Black Hole, you can hardly believe it.
It is indeed fenomenal, that the orbit is exactly for what General Relativity predicts.
For more info: see one of the links below.
-Massive (and not so massive) Primordial Black Holes.
Interestingly, rather recently, more and more articles appear from astronomers who make a case for abundant
massive "primordial" black holes.
For example, in the "arxiv" library, many recent articles can be found.
However, the theory is not new, but it seems that it received a renewed interest from the community.
It's indeed highly remarkble. In essence, the abundant number of massive "primordial" black holes
came into existence, relatively short after the Big Bang. A number of astronomers believe
that they were actually a motor around Galaxy formation.
Note: For about Galaxy formation after the Big Bang: it was often assumed that small fluctuations during
the Inflationary period, were actually the source for later Galaxy formations.
But, it seems now, that an alternative is considered.
-Detected Gravitational waves due to Black Hole collisions.
Already predicted by Einstein's GTR, finaly, in september 2015, the first "direct" observation
of gravitational waves was performed by the the LIGO and Virgo Scientific Collaboration.
Only after extremely careful examinations, the result was announced to the public, in februari 2016.
Since Relativity Theory plays in a Continuum "background", all relative motions (especially accelerations)
of Mass-Energies must produce distortions in SpaceTime which propagate, not unlike
the usual ElectroMagnetic radiation (like radio waves). However, those are generally extremely weak
and connot currently be detected.
However, when Massive Black Holes gets nearer and nearer, they have an "interaction" (acceleration)
resulting in evenly proportional distortions (waves) in SpaceTime, which might be
detected, here on Earth.
And that's exactly what happened in 2016!
The label of the event: GW150914
The source: 2 black holes of approximately 30 and 35 Solar Masses, spiraled to each other
ever faster and faster, resulting in an incredible sort of "merger" of those two entities.
Distance: About 1.4 * 109 ly away from our Sun.
Peak signal: due to the merger, resulting in 3 Solar Masses energy conversion into Gravitational waves.
Note: ofcourse, since the event was calculated to be as far as 1.4 * 109 lightyears away from us,
we must understand that it actually happened about 1.4 * 109 years ago (indeed: that far in the past).
Tip: Why don't you Google on the LIGO detection equipment, and it's ability to measure extremely
small distortions in SpaceTime. I am quite sure you will knocked out of your socks!
-April 2019: The very first photo of the Massive black hole in M87.
In April 2019, the "Event Horizon Telescope" organization, published the first image
of a very massive black hole in the galaxy M87.
M87 is a galaxy, at a distance of about 55 * 106 ly.
Using a worldwide array of radiotelescopes, with telescopic devices distributed across the Globe,
it has proven to be possible to capture images of the Black Hole in the core of M87.
In that period, typically about 350 Terrabytes per telescope, per day, were processed by Supercomputers,
using smart algolrithms, ultimately resulting in very clear pictures.
The pictures essentially show extremely hot matter and gas, under the enormous gravitational pull
of that super massive black hole. On the pictures, the "shadow" of the Event Horizon is visible.
Also the twists of the matter and gas near the Horizon, due to extreme gravity, is shown.
The true Event Horizon is about 2.5 smaller than the Shadow it casts on the clouds.
It has been calculated to be around 7 * 109 km, which makes it quite comparable
to the size of our own Solar system. How about that !
The mass of this Black Hole is about 6.5 * 109 Solar masses.
Some links about the pictures of the Black Hole of M87:
Event Horizon Telescope
Picture and explanation M87 and it's supermassive Black Hole
Picture and explanation M87 and it's supermassive Black Hole
Nice article of National Geographic
8. Hubble redshifts and interpretations:
1. Origin and basic idea:
You may generally say, that well before the year 1920, the observed Nebula (even those with a spiral structure),
were not generally understood to be real Galaxies (independent "star islands", like our own Milky way).
Well, that is, by the main stream astronomers. Already in the early 1800's, some folks really
already suspected, that some nebula were "star islands", just like our own Spiral Galaxy is.
Then, in the early 1920's, it became more and more accepted that many Nebula were indeed
independent "star islands", that is, Galaxies.
It's all very facinating history ofcourse. But one feature stood out: The more distant a Galaxy
seemed to be from us, the more "redshift" was noticable in it's spectrum.
That was quite weird in a Universe which most folks, at that time, characterized as "Stable" and "Steady".
But it seemed that those remote Galaxies, recede from us, and "the further they are, the faster they go".
Hubble found a way to explain it. It's like the "doppler effect" with sound waves.
If a car with a sirene races towards you, the pitch is higer. When it has passed, and drives
away from you, the pitch gets lower.
The same effect occurs with light. Ofcourse, the speed of light is constant, independend
of the "frame of reference". But if a Galaxy moves with a high velocity
towards you, the wavelength of it's light gets shorter, and the light will shift to the "blue" side
of the spectrum.
The other way around: if that Galaxy moves away from you, the wavelength gets longer, and the light
shifts to the red side of the spectrum.
And: the higher the speed, the more the blue shift, or red shift.
Hubble found that remote Galaxies recede from us, and the further away they are, the more redshift
there is, and thus the faster they go away from us.
As you yourself may have suspected, it looks like some sort of a hint to some "Big Bang" in the remote past.
As historians have made clear, it was Lemaitre who came in 1927 with the idea that such an expanding universe
can be "calculated back" in time, to some "sort" of origin.
However, it remains rather peculiar that galaxies flee away faster and faster, depending
on the distance to us. Even today, this is not fully solved, but complex ideas exists
like "some Dark Energy" which is responsible for the effect, but other theories exists too.
One nice analogy is a balloon. If you blow a small bit of air in it, you can draw some small galaxies
on the surface. Now, you inflate the balloon more and more. As you will notice, for every galaxy,
it seems that all others flee away. No galaxy is "special", and for every galaxy, it seems that all
others go further and further away. In this example, the balloon surface streches more and more,
explaining the observed effect.
But what about the real Universe? Does SpaceTime "strech out" as time goes by, or what?
Let's first get back to Hubble, or I should say "Hubble-Lemaitre", since both independently had the same
sort of ideas (actually, so it seems, Lemaitre a little bit before Hubble).
The mathematical relation Hubble and Lemaitre found, describing the receding speed "v" and distance "d",
looks remarkable "simple". It's just a linear relation:
v = H0 * d
Where H0 is a constant (Hubble's constant).
So, it relates the speed of a fleeing Galaxy, with respect to it's distance to us.
It must be said, that the relation does not work well, with objects which are "relatively" close,
that is, within 300 million ly (or thereabout). Do not take that lower limit "too strict".
However, for relatively remote objects, the "law" works "rather" well, but has limitations.
For one thing, it turned out that's not so easy to determine the Hubble constant H0,
and different considerations produced different values over time.
One recent study (2017) produced a generally accepted value of approximately "70 kilometres per second per megaparsec".
The theory presented sofar, is an oversimplification ofcourse. But, it's a note by Albert,
so we already knew that fact.
However, we are not done yet with Hubble's constant. The modern (socalled) Planck CMB data,
have introduced a rather remarkable "tension", between established methods to determine Hubble's constant,
and what we can derive from Planck CMB data.
It might well be that the Hubble constant is dependent on the densities of normal matter, dark matter, and
dark energy. See section 9 for more information.
2. Accelerated expansion?:
That the Universe expands, might not sound too strange, if one accepts the Big Bang model
of the Universe.
For many Physicsts, Astronomers and other scientists, the socalled "Inflationary epoch" seems
to be good refinement of the Big Bang Theory.
A Universe which expands is one thing, but there seems to exist strong indications that we might
have an accelerated expansion, and this, possibly, is somewhat harder to understand.
One experimental study (1998) was with observations on Supenova Type 1a, which are supposed to behave
as "standard candles" and provide a well-defined luminocity (they all have the same brightness).
This standard brightness can be used to calculate the distance. At the same time, the researchers
can use the redshift to determine the distance and relative speed.
The study turned out to deliver somewhat slightly unexpected results.
The Supernova were "fainter" (less bright) as what was expected from redshift/distance calculations.
Or, they seem farther away, then was expected. Below you can see how the experimental data looks like.
The "Supernova Cosmology Project" data.
Although the data does not seem to deviate a lot, by the "eye", it's still scientifically significant.
All in all, the data seems to point to an acceleration of remote objects.
The "acceleration" should be perhaps be interpreted as follows (it's not an explnation):
The way SpaceTime determines the "metric", or how to "calculate" a distance, is changing.
In such an opinion, it's not really so that Space is added, or Space gets streched,
but an intrinsic property of SpaceTime, still unknown to us, rescales the distance between objects.
This sounds somewhat mysterious, and most people simply say that Space streches more and more.
Anyway, whether the above is true, or something else is going on, for remote objects,
it "looks like" if they are moving through Space, but it is actually Space
itself, which "streches" (or perhaps in better words, rescales itself continuously).
For ease of argument, I will often say that SpaceTime will strech over time, but that
might be an incomplete statement.
Next should follow an explanation of this effect. I think it's fair to say that it is still
a subject that's debated, and investigated, intensively.
Indeed: one fundamental question thus seems to be: What is it exactly, that expands, in an expanding Universe??
One line of reasoning, is the proposition that the Vacuum has an intrinsic energy which is the
driving force behind the streching, or rescaling, of SpaceTime. However, nobody knows for sure right now.
Anyway, the objective of this section, namely a few words on the Hubble Redshift,
is hopefully achieved.
9. The "Age" and "size" of the Universe:
In this section we like to see, if the are any answers about the "age" and "size" of the Universe.
For about the "size", we will see that there are some extra considerations we must keep in mind.
But, there are reasonable answers to these questions.
What about the age of the Universe?
Astronomers have a rather large tookit, to determine to age of the Universe.
1. Using Hubble's law in a backwards calculation:
Hubble's Law tells us that the universe is expanding, and we already have seen in the section above,
that "v=H0 * d". If needed, please see section 8 again.
Using solely that relation, and assuming a constant expansion (which procedure in this case
is not fully correct), you can calculate backwards, to the "point" where it all started.
I must explicitly state, that this calculation is extremely rough, and can do no better
than to point us to the order of magnitude of the age of the Universe.
-> What's more, how do we know for sure that Hubble's constant does not depend on time?
For example, was it the same value, 3 billion years ago?
For now, as many astronomers do, Hubble's constant is taken as constant with respect to time.
-> Also, let's assume a constant expansion (which is probably incorrect too).
Not withstanding all counter arguments, I am not "a piece of cotton wool", so let's simply
try our shaky calculation:
Note: you do not need to follow this calculation.
v=H0 * d and we have d = v * t (constant expansion) => t = d/v thus:
t=d/v = d/(H0 * d) thus:
A good (*) value for H0 seems to be H0=72 km/s*Mpc, where 1 Mpc=(about) 3 * 1019km
Now, we have a time unit (s) in the relation above, so we can rework H0 to:
1/t = 72/(3*1019) = 24/10-19 => 1/t = 2.4 * 10-18
=> t = 1/2.4 * 10-18 = 4.2 * 1017 seconds.
Now, let's rework the number in seconds, to years:
=> t = 13.3 * 109 year.
So, this very rough calculation (which is quite shaky indeed), gives us 13.3 billion years,
or 13.3 * 109 years, for the age of the Universe.
Amazingly, this comes quite close to the value which astronomers believe to be the
correct (or reasonable) value of 13.8 * 109 year.
(*): Since the WMAP and Planck CMB data, there exists a "tension" between different
methodologies to determine H0. Below we find some more information on this.
2. Investigating old stars, and Globular Clusters:
Astronomers say that especially Globular Clusters are very, very old.
If one would study articles about Globular Clusters, then a typical age is somewhere
around 11 to 12 * 109 years. Actually, they must have been formed
rather shortly after the birth of the Universe.
Serious thoughts are, that for example for the Globular Clusters around our Milky way,
that they might be older than the Milky way itself.
In a way, these Clusters place a lower limit to the minimum age, because obviously,
the Universe must have been created, before Globular Clusters could have formed.
So, from the study of some established older objects, like Globular Clusters, we can say
that the age of the Universe must be larger than 12 * 109 years.
3. CMB data:
The "start" of the Universe, is widely believed to be described by the Big Bang Theory.
In 1980, a possible refinent was proposed (or added), called the "Inflationary epoch",
or "Inflationary Cosmology" (by Guth). Since then, many revisions to the theory happened, leading to a large
amount of great articles and opinions.
However, in the scientific community, as (almost) always, we have scientist who are "pro",
but also quite a few of other scientists which don't like it much.
But, Inflation certainly has an answer to some former "tough problems" like the "horizon-" and "flatness" problems.
And, the recent Planck CMD data (see below), makes it really hard to dispute the Inflationary scenario.
The Inflationary theory says, that at an (almost) absurdly small time scale from the very start of the Universe,
from say, 10-37 to 10-31 seconds, a period of exponential (extremely rapid) expansion
of SpaceTime took place.
At slightly later phases, after inflation, several rather complicated events happened.
(For this note, the details are not important).
Let's say that, as of 10-6 seconds (or so), more "mundane" (or familiar) physics took over.
After the "Inflationary epoch", Universe expanded further (non-inflationary), and also cooled down.
A while later on, was a rather lengthy period where particles like protons, electrons, and
intense radiation was present, as a "plasma", or soup of loose particles, where photons constantly interacted
with those particles.
So, for this radiation, the Universe was opaque, and "free paths" were impossible.
Then, approximately 380000 years after the Big Bang, the Universe was sufficienly cooled down
for particles to finally form atoms (primarily Hydrogen). For radiation, it meant a "free path",
and the Universe became transparant for radiation. Finally set free !
This first free radiation of the early Universe, is the source of the "Cosmic Microwave Background" radiation,
or CMB, as we observe it today.
At that time, at the moment the Universe became transparant, the temperature was about 3000K.
From then, up to now, the Universe has steadily expanded, cooled down, and the present "afterglow"
is about 2.72K. As the Universe expanded over time, so did this radiation, until it reached
microwave length, as it is today.
It's really a background radiaton, corresponding to about 2.72K, observable at all places,
where ever you would measure it.
There exists very slight variations in the radiation. After carfefull examination, they seem
to match extremely early quantum flucuations, which were preserved during the Inflationary period.
This is reflected in very small Temperature variations in CMB maps.
Although the very firs ideas of CMB, already slumbered around in 1948, it was actually
only discovered in 1964, by Penzias and Wilson.
However, in the last couple of decades, better and highly detailed maps were devised.
For example, using the COBE satellite (1989), and quite some time later, by using the WMAP
satellite (2001). Lastly, the Planck Surveyor mission (launched in 2009), provided the best details
in the map of the CMB. Indeed, COBE and WMAP did not have the enormous precision of the Planck data.
All in all, the details of the Planck data, really seems to hint to "dark energy" for example,
and other facinating features, like a rather strange "colder spot".
Putting this even stronger: there is a lot of new physics to be discovered.
Some nice links on Planck CMB data:
Planck CMB map (1)
Planck CMB map (2), and a facinating explanation.
The age of the Universe, as established by the Planck Collaboration team, is 13.8 * 109 years.
This was done on the basis of the Planck CMB data. Amazingly, the Hubble constant they derived
is quite a bit lower than the values derived from study of ordinary objects.
For about the age of the Universe, a (rather spicy) derivation can be found in:
Flat Space, Dark Energy, and the Cosmic Microwave Background (arxiv)
At page 14, you can see a mathematical integral, showing the calculated age of the Universe.
Such scientific articles are indeed a bit hard to read.
I primarily placed the link here, to show you (or prove to you), that the Planck CMB data, actually
gives rise to a number of renewed astronomical parameters, among which is the age of the Universe.
In the article, and other articles on CMB data, folks very cleverly expressed the Hubble constant
in density rates (density of all matter/energy, depending on time from t="0" to t="now", and integrating
the whole lot, and amazingly producing the number of 13.8 * 109 years. Simply stunning.
What about the "size" of the Universe? (see next note).
This is a bit of a spicy question.
In the past, I always believed that SpaceTime over a Global Scale, had curvature, maybe positive,
or perhaps negative (hyperbolic, ever expanding), also depending on the density of mass-energy.
However, for example by the "Inflationary Theory", or the latest data, e.g. from the Planck CMB data,
and even lots of more clues, it'really seems that SpaceTime is flat (except for local curvature near Masses).
Or is it not flat, but (positively?) curved? Is the data really convincing to say the one
or the other? Well, according to the standardized model called ΛCDM, and the latest data, it seems flat.
Many pointers say that SpaceTime is flat. Do not laugh, but I personally, am still not convinced...
Some scientist indeed still have doubts, if you scan modern articles.
To say something usefull, it's unavoidable to talk about a Primary Cosmological model of today,
which is the ΛCDM model of the Universe, but some other ideas are important too.
All in all, it's quite a bit of material to discuss.
I will try that in the next note.
Appendix 1. Optional section. Fun stuff: Parallel Universes?
Parallel Universes? No..., I am not really a "believer".
There exists no real clues that it's actually true, or neccessary.
However..., some theories are pretty strong. And it's fun to see a serious collection
of such theories. But, I like to emphasize on the "fun" part of it.
Still, it may help to give an additional perspective on our Universe. Who knows?
If you like to see it, use the following link:
A simple overview of some "Parallel Universe" theories.
Last update: 21 April, 2020.
That's it for now! Hope you enjoyed it. | 0.88443 | 3.018611 |
Kepler data reveals most Earth-like exoplanet in size and temperature yet
A review of early data returned by NASA's Kepler mission has revealed one of the most Earth-like exoplanets discovered so far. Located 300 light-years away, the new planet is slightly larger than our own, is estimated to have a similar temperature, and orbits in the habitable zone of its parent star.
Like going through the pockets of an old suit in search of overlooked cash, revisiting old scientific data can often reap remarkable benefits. A case in point is the data sent back by NASA's Kepler space telescope. Though the unmanned orbital observatory was retired in 2018, the information it gleaned is still telling scientists a great deal about planets orbiting stars outside the solar system.
According to NASA, Kepler-1649c was overlooked by initial analysis, but this wasn't due to carelessness. Kepler looked for exoplanets by measuring dips in the light curves of various stars. Such a dip can be caused by a planet passing between the star and Kepler like a mini-eclipse. However, planets aren't the only cause of such dips. Other phenomena, such as the natural variability of the star or passing clouds of cosmic dust can produce what is called a false positive 88 percent of the time.
To avoid these false positives and speed up analysis, NASA used a computer algorithm called Robovetter. The space agency realized early on that this approach wasn't perfect, so it set up the Kepler False Positive Working Group, which is tasked with reviewing the Kepler data with a finer computer comb to see which false positives are really false negatives. In other words, misidentified exoplanets.
With Kepler-1649c, the group hit the jackpot with the closest analog to the Earth yet seen. The rocky exoplanet is only 1.06 times larger than Earth and it receives 75 percent as much light from its sun as the Earth does, meaning that it may have a similar temperature – although the composition of the planet's atmosphere remains unknown which could affect its temperature. Most importantly, its orbit is inside the habitable zone of the star Kepler-1649. That is, the area where liquid water can exist on a planet's surface.
NASA says that though some exoplanets are closer to Earth in size and some closer in temperature, and a number have been found inside their star's habitable zone, this is the first one to match so closely in all three critical categories.
However, the agency stresses that Kepler-1649c may not be all that pleasant. Its parent star, which it orbits once every 19.5 Earth days, is a red dwarf. This is a type of star prone to throwing out deadly stellar flares that are loaded with radiation. In addition, the calculations used have a very wide margin of error that could affect habitability.
On the plus side, the planet's orbit appears stable, so it should have a long life, and red dwarfs are the most common type of star in our galaxy, suggesting that such Earth-like planets are very common as well.
"The more data we get, the more signs we see pointing to the notion that potentially habitable and Earth-size exoplanets are common around these kinds of stars," says Andrew Vanderburg, a researcher at the University of Texas at Austin. "With red dwarfs almost everywhere around our galaxy, and these small, potentially habitable and rocky planets around them, the chance one of them isn't too different than our Earth looks a bit brighter."
The research was published in The Astrophysical Journal. | 0.872557 | 3.735996 |
California Institute of Technology scientists Mike Brown and Konstantin Batygin shocked the world when they announced the possible existence of a ninth planet in our solar system earlier this year.
The only problem is their research paper is based on a mathematical model, not on direct observation of the planet.
Spotting the planet and proving it exists is not going to be an easy task. Brown and Batygin think planet nine is orbiting so far out on the fringes of our solar system that it likely takes somewhere between 10,000 and 20,000 years for it to complete a lap around the sun. That's a huge ring of sky to search through. It really is like looking for a needle in a haystack.
So Brown and Batygin asked other astronomers to help them start looking, and one team has already answered the call. New research published in the journal Astronomy & Astrophysics has made the haystack a lot smaller.
If planet nine exists, it should have some kind of gravitational influence on the other planets in the outer solar system, the researchers behind this new study reasoned. They modeled how planet nine might influence the other planets and then compared that to their actual position. They relied specifically on Saturn since the Cassini spacecraft currently circling the planet can provide a very precise location for it. The team was able to rule out two sections of the sky this way, effectively cutting the search area in half, according to Agence France-Presse.
This is actually a very similar method to the one that astronomers used to discover Neptune. They compared theoretical models to the location of Uranus, and figured out where in the sky to start searching for Neptune.
Still, it will likely take years to find planet nine. We'll be able to eliminate more patches of the sky and the search will go faster if the Cassini mission is extended until 2020, the researchers said.
h/t Universe Today | 0.909506 | 3.133754 |
Engineers developed the model as part of its Space Weather Modeling Framework, which is the first “first principles” model to simulate CMEs including their magnetic structure open to the public.
The dynamic space environment that surrounds Earth – the space our astronauts and spacecraft travel through – can be rattled by huge solar eruptions from the sun, which spew giant clouds of magnetic energy and plasma, a hot gas of electrically charged particles, out into space. The magnetic field of these solar eruptions are difficult to predict and can interact with Earth’s magnetic fields, causing space weather effects.
A new tool called EEGGL – short for the Eruptive Event Generator (Gibson and Low) and pronounced “eagle” – helps map out the paths of these magnetically structured clouds, called coronal mass ejections or CMEs, before they reach Earth. EEGGL is part of a much larger new model of the corona, the sun’s outer atmosphere, and interplanetary space, developed by a team at the University of Michigan. Built to simulate solar storms, EEGGL helps NASA study how a CME might travel through space to Earth and what magnetic configuration it will have when it arrives. The model is hosted by the Community Coordinated Modeling Center, or CCMC, at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The new model is known as a “first principles” model because its calculations are based on the fundamental physics theory that describes the event – in this case, the plasma properties and magnetic free energy, or electromagnetics, guiding a CME’s movement through space.
Such computer models can help researchers better understand how the sun will affect near-Earth space, and potentially improve our ability to predict space weather, as is done by the U.S. National Oceanic and Atmospheric Administration.
Taking into account the magnetic structure of a CME from its initiation at the sun could mark a big step in CME modeling; various other models initiate CMEs solely based on the kinematic properties, that is, the mass and initial velocity inferred from spacecraft observations. Incorporating the magnetic properties at CME initiation may give scientists a better idea of a CME’s magnetic structure and ultimately, how this structure influences the CME’s path through space and interaction with Earth’s magnetic fields – an important piece to the puzzle of the sun’s dynamic behavior.
The model begins with real spacecraft observations of a CME, including the eruption’s initial speed and location on the sun, and then projects how the CME could travel based on the fundamental laws of electromagnetics. Ultimately, it returns a series of synthetic images, which look similar to those produced of actual observations from NASA and ESA’s SOHO or NASA’s STEREO, simulating the CME’s propagation through space.
A team led by Tamas Gombosi at the University of Michigan’s Department of Climate and Space Sciences and Engineering developed the model as part of its Space Weather Modeling Framework, which is also hosted at the CCMC. All of the CCMC’s space weather models are available for use and study by researchers and the public through runs on request. In addition, EEGGL, and the model it supports, is the first “first principles” model to simulate CMEs including their magnetic structure open to the public. | 0.817599 | 4.046736 |
With all the large asteroids hitting the news lately, it would have been easy for a small one to sneak under the radar. In fact, one very nearly did. On April 27, astronomers discovered a new asteroid, a little pixie of a space rock between 4 and 8 metres (13 to 26 feet) across.
It was already close to Earth at this point, and the probability of a collision was calculated at around 10 percent. At its size, it would have burnt up on atmospheric entry, so it posed no threat to humans anyway.
But the asteroid's trajectory would bring it very close to the geostationary ring, the volume of space around Earth in which bodies can maintain geostationary orbit. That space is packed with satellites.
On April 28, this asteroid - later named 2020 HS7 - skimmed past Earth at a distance around nine times closer than the average distance of the Moon.
At a distance of 42,735 kilometres (26,554 miles) from the centre of Earth - the Earth-Moon distance is 384,400 kilometres (238,855 miles) from centre to centre on average - 2020 HS7 pulled off one of the closest asteroid flybys we've ever seen.
And it skimmed the nearest satellite by just 1,200 kilometres (746 miles). That may sound a bit scary, but neither we nor our satellites were in any particular danger.
"Small asteroids like 2020 HS7 safely pass by Earth a few times per month," said astronomer Lindley Johnson of NASA's Planetary Defense Coordination Office just prior to the flyby. "It poses no threat to our planet."
In fact, 2020 HS7 was a good thing. It allowed scientists to test their detection, observation, follow-up and prediction capabilities on a small near-Earth asteroid. And they showed they were able to predict and track the path of 2020 HS7 with incredible accuracy, even with just a day's notice.
You may have been hearing about near-Earth asteroids a lot recently. In just the last few months, we've had larger asteroids such as 2020 BX12 and 1998 OR2 (which had its close flyby just a day after 2020 HS7) swing past.
Astronomers have also just watched comet 2I/Borisov, the interstellar visitor, crumble into pieces. But although it may seem like there are more rocks than ever in our vicinity, in reality, we're just getting really, really good at spotting and tracking them.
This is great news for us, because it means we are becoming better equipped to deal with an asteroid that will pose a threat to Earth. Detection, observation and prediction are the first steps.
What comes after that is still being ironed out, but we're getting there. In 2022, space agencies around the world will be working together to ram a spacecraft into an asteroid (one that's not headed for Earth) to see if we are able to deflect its course.
If it works, we will have another brilliant tool in our kit for keeping giant rocks from raining fiery death on our planet. | 0.83025 | 3.672675 |
Saturn’s F ring is certainly a curious structure. Orbiting the giant planet 82,000 kilometers above its equatorial cloud tops, the F ring is a ropy, twisted belt of bright ice particles anywhere from 30-500 km wide. It can appear as a solid band or a series of braided cords surrounded by a misty haze, and often exhibits clumps and streamers created by the gravitational influence of embedded moonlets or passing shepherd moons.
In the picture above, acquired by the Cassini spacecraft on Feb. 13, 2013 and released on May 27, we see a section of the F ring separated into long ropes and spanned by connecting bands of bright material — the “ladder” structure suggested in the title.
Scientists believe that interactions between the F ring and the moons Prometheus and Pandora cause the dynamic structure of the F ring. (Watch an animation of the F ring and shepherd moons here.)
Made of particles of water ice finer than cigarette smoke, the F ring orbits Saturn beyond the outer edge of the A ring across the expanse of the 2,600-km-wide Roche Division. In these images, Saturn and the main ring systems are off frame to the left.
This view looks toward the unilluminated side of the rings from about 32 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft’s narrow-angle camera (NAC).
The view was obtained at a distance of approximately 426,000 miles (686,000 kilometers) from Saturn and at a phase angle of 162 degrees. Image scale is 2 miles (4 kilometers) per pixel. | 0.814924 | 3.383581 |
Was the Moon created by a nuclear explosion on Earth?
By Daily Mail Reporter
29th January 2010
How the Moon was created and came to orbit the Earth has long puzzled scientists.
The most commonly held theory is that when the solar system was first formed, an object collided with Earth, knocking off a chunk of rock that fell into orbit around it.
But now two scientists have come up with a new explanation. They believe the Moon did not break away from the Earth because of an impact or an explosion in space, but because of a nuclear explosion on Earth itself.
Their idea is based on the fission theory which was first outlined in the 19th century.
The fission theory suggested that the Earth and Moon were both created out of the same blob of spinning molten rock - with a part becoming separated which later became the moon.
However, aside from an impact, scientists couldn't explain how the blob which became the moon spun off.
Rob de Meijer at University of the Western Cape and Wim van Westrenen at VU University in Amsterdam believe the Moon was blasted out of the Earth by a nuclear explosion on our planet.
In their research paper, 'An alternative hypothesis for the origin of the Moon', they explain that if the moon had been separated from the Earth by an impacting external force, the moon would be composed of whatever knocked into it and the Earth.
'Models of solar system evolution show that it is highly unlikely for the chemical composition of the Earth and impactor to be identical,' they state.
Yet recent lunar samples show that the moon is almost identical in chemical composition to the Earth - suggesting there was no impactor involved.
'A more likely possibility for the large degree of compositional similarity... is that the moon derives directly from terrestrial material,' the research paper states.
They believe that the energy that caused the moon to break into orbit around Earth was 'supplied by a supercritical georeactor in Earth’s core-mantle boundary producing sufficient heat to vaporize and eject part of the bulk silicate earth'.
Clay Dillow from Popular Science supports the theory. He states: 'According to their explanation, the centrifugal forces on Earth concentrated heavier elements like uranium and thorium near the surface around the equatorial plane.
'Enough of these elements in high enough concentrations could set off a runaway nuclear chain reaction, similar to the kind that cause nuke plant meltdowns.
'In this way, a natural-born nuclear georeactor was pushed to supercritical levels and: BOOM! The moon was cleaved from the Earth and rocketed into orbit by a massive nuclear explosion.
'It’s a tough theory to test, but we do know that nuclear georeactors existed, their legacy left behind in the uranium we mine from the Earth today. '
De Meijer and van Westrenan conclude that proving their theories will depend on future moon missions returning lunar samples from greater depths. | 0.823194 | 3.020649 |
Even if this effect occurred 4.5 billion decades back,”it might take many, many centuries for the heavy substance to repay down into a dense heart under the conditions suggested by the newspaper”, said researchers who assessed readings from NASA’s Juno spacecraft.
The research team conducted tens of thousands of computer simulations and discovered a fast-growing Jupiter could have perturbed the orbits of local”planetary embryos,” protoplanets which were at the first phases of planet formation.
“Because it is compact, and it comes in with a great deal of energy, the impactor will be just like a bullet which goes through the air and strikes the heart head-on,” Isella explained.
“That is perplexing. It indicates that something occurred that awakened the heart, and that is where the giant effect comes into play,” explained Rice astronomer and research co-author Andrea Isella at a newspaper printed in the journal Nature.
An enormous, head-on collision involving Jupiter and a still-forming world from the solar system, about 4.5 billion decades back, has abandoned Jupiter’s heart less dense and more extended that anticipated, say investigators.
“Ahead of effect, you’ve got an extremely dense core, surrounded by air. The head-on effect brings out things, diluting the center.”
Isella said major theories of planet formation imply Jupiter started as a compact, rocky or icy world that afterwards accumulated its thick air in the primordial disk of dust and gas which birthed our sunlight.
The crash scenario became more compelling after Liu conducted 3D computer models that revealed the way the crash could impact Jupiter’s core.
The Juno assignment was created to help scientists understand Jupiter’s origin and development.
“The only situation that caused a core-density profile very similar to that which Juno measures now is that a head-on influence using a planetary embryo approximately ten times more massive than Earth,” Liu explained.
Isella stated that he was skeptical when research lead author Shang-Fei Liu initially suggested the thought that the information could be clarified by a giant effect that awakened Jupiter’s heart, mixing the dense contents of its heart with significantly less dense layers over. | 0.881626 | 3.541318 |
Pic NASA's Hubble Space Telescope has captured a stunning shot of the Eta Carinae system's largest star suffering a near-death experience before it goes supernova in the near future.
The beginning of the end for the Eta Carinae star. Credit: ESA/NASA
Earlier this month boffins published a study into the Eta Carinae star's near-nova explosion during which it shed ten solar masses*. The violent detonation was seen in 1843 and, discounting our Sun, made the heavenly body the second brightest star in the sky. The only star brighter was Sirius, which is nearly a thousand times closer to Earth.
Now the star is once more visible to the naked eye at night, although it's nowhere near as bright as it was back in the 19th century.
This pic shows the cloud of material, now known as the Homunculus Nebula, thrown out during the star's brush with death - what space boffins call a "supernova impostor event".
The image, consisting of ultraviolet and visible light images from the High Resolution Channel of Hubble's Advanced Camera for Surveys, shows that the debris from the event wasn't thrown out uniformly, but in a dumbbell shape.
Boffins are fairly confident that the Eta Carinae star is on its way out and they expect its supernova in the near future. Of course, this being in astronomical timescales, "near future" could be as much as a million years from now.
Whenever it does eventually go off, the star will be one of the closest to Earth to explode when there was someone here to see it, giving an impressive view to folks on the surface - Eta Carinae is only 7,500 light years away.
The brightest supernova ever observed was SN 2005ap [PDF], a star of the same type, located 4.7bn light years away and detected by the McDonald observatory in West Texas. ®
* One solar mass is equivalent to 1.98892 x 1030 kilograms
Sponsored: Webcast: Simplify data protection on AWS | 0.884177 | 3.393521 |
The galaxy we inhabit, the Milky Way, may be getting even bigger, according to recent astronomical research.
Researchers calculated that galaxies like the Milky Way are growing at around 500 meters per second, fast enough to cover the distance from Liverpool to London in about twelve minutes.
A composite image of NGC 4565 used in the new study. Credit: C. M. Lombilla / IAC
“The Milky Way is pretty big already. But our work shows that at least the visible part of it is slowly increasing in size, as stars form on the galactic outskirts,” said Cristina Martínez-Lombilla, a PhD candidate at the Instituto de Astrofísica de Canarias in Tenerife, Spain.
“It won’t be quick, but if you could travel forward in time and look at the galaxy in 3 billion years’ time it would be about 5% bigger than today.”
Astronomers set out to establish whether other spiral galaxies similar to the Milky Way really are getting bigger, and if so what this means for our own galaxy. Martínez-Lombilla and her team used the ground-based SDSS telescope for optical data, and the two space telescopes GALEX and Spitzer for near-UV and near-infrared data respectively, to look in detail at the colors and the motions of the stars at the end of the disc found in the other galaxies.
The researchers measured the light in these regions, predominantly originating from young blue stars, and measured their vertical movement (up and down from the disc) of the stars to work out how long it will take them to move away from their birthplaces, and how their host galaxies were growing in size.
This slow growth may be moot in the distant future. The Milky Way is predicted to collide with the neighbouring Andromeda Galaxy in about 4 billion years, and the shape of both will then change radically as they merge.
Research will be presented on Tuesday 3 April, 2018 at the European Week of Astronomy and Space Science in Liverpool. | 0.802462 | 3.442655 |
ALMA's world at night
This panoramic view of the Chajnantor plateau, spanning about 180 degrees from north (on the left) to south (on the right) shows the antennas of the Atacama Large Millimeter/submillimeter Array (ALMA) ranged across the unearthly landscape. Some familiar celestial objects can be seen in the night sky behind them. These crystal-clear night skies explain why Chile is the home of not only ALMA, but also several other astronomical observatories. This image is just part of an even wider panorama of Chajnantor.
In the foreground, the 12-metre diameter ALMA antennas are in action, working as one giant telescope, during the observatory’s first phase of scientific observations. On the far left, a cluster of smaller 7-metre antennas for ALMA’s compact array can be seen illuminated. The crescent Moon, although not visible in this image, casts stark shadows over all the antennas.
In the sky above the antennas, the most prominent bright “star” — on the left of the image — is in fact the planet Jupiter. The gas giant is the third brightest natural object in the night sky, after the Moon and Venus. The Large and Small Magellanic Clouds can also be clearly seen on the right of the image. The Large Magellanic Cloud looks like a puff of smoke, just above the rightmost antenna. The Small Magellanic Cloud is higher in the sky, towards the upper-right corner. Both “clouds” are in fact dwarf irregular galaxies, orbiting the Milky Way galaxy, at distances of about 160 000 and 200 000 light-years respectively.
On the far left of the panorama, just left of the foreground antennas, is the elongated smudge of the Andromeda galaxy. This galaxy, more than ten times further away than the Magellanic Clouds, is our closest major neighbouring galaxy. It is also the largest galaxy in the Local Group — the group of about 30 galaxies which includes our own — and contains approximately one trillion stars, more than twice as many as the Milky Way. It is the only major galaxy visible with the naked eye. Even though only its most central region is apparent in this image, the galaxy spans the equivalent of six full Moons in the sky.
This photograph was taken by Babak Tafreshi, the latest ESO Photo Ambassador. Babak is also founder of The World At Night, a programme to create and exhibit a collection of stunning photographs and time-lapse videos of the world’s most beautiful and historic sites against a nighttime backdrop of stars, planets and celestial events.
ALMA is being built on the Chajnantor plateau at an altitude of 5000 metres. The observatory, which started Early Science operations on 30 September 2011, will eventually consist of 66 antennas operating together as a single giant telescope. This international astronomy facility is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
- Time-lapse videos of ALMA on Chajnantor made by Babak Tafreshi: one, two
- ESO Photo Ambassadors
- More about ALMA at ESO: http://www.eso.org/public/teles-instr/alma.html
- The Joint ALMA Observatory: http://www.almaobservatory.org/
- The World At Night: http://www.twanight.org/
ESO/B. Tafreshi (twanight.org)
About the Image
|Release date:||12 December 2011, 10:00|
|Size:||11919 x 3836 px|
|Field of View:||120° x 50°|
About the Object
|Name:||Atacama Large Millimeter/submillimeter Array, Panorama|
|Type:||Unspecified : Technology : Observatory| | 0.803654 | 3.77567 |
- This event has passed.
Physics Colloquium Series: Professor Bruce Wilking
(Physics Lecture Series) University of Missouri-St. Louis, Department of Physics and Astronomy
“Formation of Low Mass Stars and Substellar Objects”
Stars form in filamentary clouds of cold and dense molecular gas. Recent evidence that the majority of stars in the Galaxy are born in embedded star clusters will be reviewed. Using infrared imaging to study these clusters, one can gain insight into the formation and evolution of young stellar objects and the timescales for their evolution. Through infrared spectroscopy, the ages and masses of young stars can be inferred as well as their dynamical evolution. The “initial mass function” for a cluster can also be constructed for comparison with other clusters including the frequency of substellar mass objects called brown dwarfs. The embedded cluster in the nearby Rho Ophiuchi molecular cloud will be presented as an example. | 0.830831 | 3.108166 |
Science fiction stories that involve interstellar travel typically contain some method of faster-than-light travel. After all, the spaces between stars are incomprehensibly vast, and no conventional spacecraft could hope to cross these gulfs in anything resembling a timely manner. As such, stars in our own galaxy can feel impossibly distant.
Reasonably speaking, then, what’s the fastest we could get a spaceship moving in the real world? Physics, as we understand, doesn’t offer many promising ways to even get close to the speed of light, let alone exceed that rational upper limit on movement.
But could we find a way to accelerate up to a meaningful fraction of the speed of light?
Enter Freeman Dyson’s Theories
Freeman Dyson, well-known for his Dyson Sphere theory of deep-space megastructures, conceived of a highly advanced civilization that could harness the power of gravity to accelerate their ships to speeds that made interstellar travel feasible within an individuals’ lifetime.
How would they do this, you ask? Let’s talk about slingshot orbits.
In 1977, the Voyager mission used the gravity well of Jupiter for what is known as a “gravitational assist,” or a slingshot orbit. This is a process by which a craft uses a celestial body, like a planet or a star, to drop into a long, looping orbit that then has them exit on another vector with much more velocity.
According to Dyson’s research, a craft could exit a slingshot orbit up to twice the velocity of the celestial body used for the assist.
Going Bigger, Going Faster
Voyager used Jupiter as a springboard to launch itself deep into interstellar space, proving that such a maneuver was feasible. However, to truly put a dent in the time it takes to travel interstellar distances, a craft would need to use a much denser celestial body than a gas giant as its assist. That’s where the Dyson Slingshot comes into play.
Dyson conceived of a theoretical cosmic structure that a sufficiently advanced species could either discover or engineer for the express purpose of slinging their craft into space at high velocities. To be truly effective at interstellar travel, the structure would need to be an orbiting pair of neutron stars.
Binary Neutron Systems
A binary neutron system is two stars, locked in a death spiral on the verge of becoming black holes, held together only by their own neutron resistance. They are among the densest objects in the observable universe, and they orbit one another at an astonishing speed.
A ship with just the right trajectory could use the immense gravity field of such a binary system to accelerate up to a quarter of the speed of light.
This would make interstellar travel more than just feasible. It would allow a vessel to cross the gulfs between stars in a matter of decades instead of hundreds of thousands of years.
The Problems with the Dyson Slingshot
Of course, there are some issues preventing humanity from using a slingshot orbit to fling ourselves out into the cosmos. Firstly, there are no nearby neutron stars. There are certainly no nearby binary neutron star systems. In fact, there aren’t even any nearby binary star systems that could be accelerated into a neutron state.
The second problem with this theory is that the trajectory needed to actually receive a gravity assist from a pair of neutron stars would need to be exceedingly precise. One degree out of place, and your vessel could quickly become a plasmatic film coating the surface of one of the stars as it is pulled in by the gravity well.
Science Fact or Science Fiction?
The very existence of this theory gives credence to the otherwise outlandish notion of interstellar travel. One can envision a hyper-advanced alien species capable of transforming binary star systems they encounter into neutron systems to allow their ships to travel deeper into the cosmos.
They could use a relay of these systems to venture from one end of the galaxy to the other in a matter of centuries rather than millions of years. Such a society would have as close to a mastery of the stars as our current understanding of physics allows. | 0.894524 | 3.921262 |
The Hubble Space Telescope’s Advanced Camera for Surveys has captured a remarkable image of a spiral in space. No, not a spiral galaxy, (and not another Norway Spiral!) but the formation of an unusual pre-planetary nebula in one of the most perfect geometrical spirals ever seen. The nebula, called IRAS 23166+1655, is forming around the star LL Pegasi (also known as AFGL 3068) in the constellation of Pegasus.
The image shows what appears to be a thin spiral pattern of amazing precision winding around the star, which is itself hidden behind thick dust. Mark Morris from UCLA and an international team of astronomers say that material forming the spiral is moving outwards at a speed of about 50,000 km/hour and by combining this speed with the distance between layers, they calculate that the shells are each separated by about 800 years.
The spiral pattern suggests a regular periodic origin for the nebula’s shape, and astronomers believe that shape is forming because LL Pegasi is a binary star system. One star is losing material as it and the companion star are orbiting each other. The spacing between layers in the spiral is expected to directly reflect the orbital period of the binary, which is estimated to be also about 800 years.
A progression of quasi-concentric shells has been observed around a number of preplanetary nebulae, but this almost perfect spiral shape is unique.
Morris and his team say that the structure of the AFGL 3068 envelope raises the possibility that binary companions are responsible for quasi-concentric shells in most or all of the systems in which they have been observed, and the lack of symmetry in the shells seen elsewhere can perhaps be attributed to orbital eccentricity, to different projections of the orbital planes, and to unfavorable illumination geometries.
Additionally – and remarkably — this object may be illuminated by galactic light.
This image appears like something from the famous “Starry Night” painting by Vincent van Gogh, and reveals what can occur with stars that have masses about half that of the Sun up to about eight times that of the Sun. They do not explode as supernovae at the ends of their lives, but instead can create these striking and intricate features as their outer layers of gas are shed and drift into space. This object is just starting this process and the central star has yet to emerge from the cocoon of enveloping dust. | 0.882903 | 3.915625 |
Water on an extrasolar planet
11 July 2007 Scientists report the first conclusive discovery of the presence of water vapour in the atmosphere of a planet beyond our Solar System. The discovery was made by analysing the transit of the gas giant HD 189733b across its star in the infrared.
Giovanna Tinetti, ESA fellow at the Institute d’Astrophysique de Paris, and colleagues from around the world, used data from NASA’s Spitzer Space Telescope. They targeted planet HD 189733b, 63 light-years away, in the constellation Vulpecula.
The planet was discovered in 2005 as it dimmed the light of its parent star by some three percent when transiting in front of it. Using Spitzer, Tinetti and the team observed the star, which is slightly fainter than the Sun. They watched its starlight dim at two infrared bands (3.6 and 5.8 micrometres).
Had the planet been a rocky body devoid of atmosphere, both these bands and a third one (8 micrometres), recently measured by a team at Harvard, would have shown the same behaviour.
Instead, as the planet’s tenuous outer atmosphere slipped across the face of the star, the starlight absorbed showed a different, distinctive pattern. The atmosphere absorbed less infrared radiation at 3.6 micrometres than at the other two wavelengths.
“Water is the only molecule that can explain that behaviour,” says Tinetti.
The presence of water vapour does not necessarily make it a good candidate in the search for planets that harbour life. “This is a far from habitable world,” she adds.
Instead of a rocky world like Earth, HD 189733b is large, about 1.15 times the mass of Jupiter. Located just 4.5 million km from its star, it orbits it in 2.2 days. In comparison, Earth is 150 million km from the Sun; even Mercury, the innermost planet, is 70 million km away.
Astronomers classify such worlds as ‘hot Jupiters’. These planets tend to have extensive atmospheres because heat from the nearby star gives them energy to expand. HD 189733b is no exception; its diameter is 1.25 times that of Jupiter.
HD 189733b’s atmospheric temperature is about 1000 Kelvin (a little more than 700°C) or higher, implying that the significant amounts of water vapour in the atmosphere cannot condense to fall as rain or form clouds. The temperature would have to be about five times lower to form clouds of water vapour or rain.
That does not mean the atmosphere is sedate, however. The planet is gripped so tightly by the gravity of its star that one hemisphere constantly faces the star, heating the planet only on one side. This probably generates fierce winds sweeping from the day-side to the night-side. “There are a thousand things to learn about these planets,” says Tinetti.
Although, being a gas giant, the planet is an unlikely candidate in the search for life, these results increase hopes for the detection of water on other rocky planets, which astronomers hope to discover in the near future.
France‘s COROT mission, in which ESA participates, is expected to detect dozens of transiting gas giants, and has been working so well that it may also detect nearly Earth-sized worlds.
Atmospheres of rocky planets should be much more tenuous, so they will have to wait for future space telescopes, such as the James Webb Space Telescope, before they can be investigated.
The mission Darwin is expected to be proposed to ESA under the Cosmic Vision Programme, with a possible launch date sometime after 2018. A constellation of four spacecraft, Darwin’s goal would be to find and analyse atmospheres of Earth-sized planets, looking for telltale signs of water vapour and other gases that might betray life on those worlds.
NASA’s Jet Propulsion Laboratory (JPL), Pasadena, California, manages the Spitzer Space Telescope for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology (Caltech), also in Pasadena. Caltech manages JPL for NASA. | 0.90165 | 3.941177 |
BU astrophysicist and collaborators reveal a new model of our heliosphere that's shaped somewhere in between a croissant and a beach ball.
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found striking orbital geometries in protoplanetary disks around binary stars. While disks orbiting the most compact binary star systems share very nearly the same plane, disks encircling wide binaries have orbital planes that are severely tilted. These systems can teach us about planet formation in complex environments.
A team of researchers have published new calculations that predict a striking and intricate substructure within black hole images from extreme gravitational light bending.
This scene of stellar creation, captured by the NASA/ESA Hubble Space Telescope, sits near the outskirts of the famous Tarantula Nebula. This cloud of gas and dust, as well as the many young and massive stars surrounding it, is the perfect laboratory to study the origin of massive stars.
Despite Mercury's 400 C daytime heat, there is ice at its caps, and now a study shows how that Vulcan scorch probably helps the planet closest to the sun make some of that ice.
A team of researchers has shown a way to determine the origins and nature of quasar light by its polarization. The new approach is analogous to the way cinema glasses produce a 3D image by feeding each eye with the light of a particular polarization: either horizontal or vertical. The authors managed to distinguish between the light coming from different parts of quasars -- their disks and jets -- by discerning its distinct polarizations.
Researchers at the North Carolina Museum of Natural Sciences have developed a technique to accurately measure the winding arms of spiral galaxies that is so easy, virtually anyone can participate. This new and simple method is currently being applied in a citizen science project, called Spiral Graph, that takes advantage of a person's innate ability to recognize patterns, and ultimately could provide researchers with some insight into how galaxies evolve.
Using data from the Dark Energy Survey, researchers have found and cataloged more than 300 minor planets beyond Neptune, including more than 100 new discoveries. This updated catalog of trans-Neptunian objects, and the methods used to find them, could aid in future searches for undiscovered planets in the far reaches of the solar system.
Nature magazine is publishing today a surprising study about the giant, ultra-hot planet WASP-76b in which researchers from the Instituto de Astrofísica de Canarias (IAC) have taken part.
An international team of researchers, affiliated with South Korea's Ulsan National Institute of Science and Technology (UNIST) has for the first time succeeded in demonstrating the ionization cooling of muons. | 0.92069 | 3.954093 |
- Published on 16 April 2018
Personal recollections of an astrophysicist shed new light on the 1995 discovery on 51 Pegasi b
In recent history, a very important achievement was the discovery, in 1995, of 51 Pegasi b, the first extrasolar planet ever found around a normal star other than the Sun. In a paper published in EPJ H, Davide Cenadelli from the Aosta Valley Astronomical Observatory (Italy) interviews Michel Mayor from Geneva Observatory (Switzerland) about his personal recollections of discovering this exoplanet. They discuss how the development of better telescopes made the discovery possible. They also delve into how this discovery contributed to shaping a new community of scholars pursuing this new field of research. In closing, they reflect upon the cultural importance that the 51 Pegasi b discovery had in terms of changing our view of the cosmos.
Michel Mayor was born in Lausanne in 1942. He turned to astronomy when he did his PhD at the Geneva Observatory, where he focused on elucidating the theoretical nature of the spiral arms of galaxies, which make it possible for stars and nebulae to pass through without permanently remaining inside the arms. Later on his interest shifted to solar-type stars, and in 1991 he published the result of 15 years of work on the statistics of such solar-type stars. In hindsight, this paper played a significant role in boosting, at a later time, his interest in brown dwarfs and planets. He feels that the search for exoplanets was a direct continuation of that work.
He then relates what drove the development of a spectrograph called ELODIE, designed to offer very high sensitivity in measuring the radial velocities of stars. ELODIE commenced operation in April 1994, and Mayor and his colleague Queloz discovered 51 Peg b in July 1995. As the first planet ever discovered around a normal star other than the Sun, it was a ground-breaking achievement. A few years later, Mayor contributed to designing and building another state-of-the-art spectrograph, called HARPS, that is now allowing astronomers to probe the universe further. Altogether about 300 new exoplanets have been discovered by Mayor and his co-workers since 51 Peg b.
“Exoplanets: the beginning of a new era in astrophysics” by Michel Mayor and Davide Cenadelli (2018), European Physical Journal H, DOI 10.1140/epjh/e2018-80063-1 | 0.823679 | 3.681341 |
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You don’t want to get close to a magnetar. From a distance of hundreds of miles, the universe’s most powerful magnets would tug at the electrons in your body’s atoms, pulling the atoms out of shape — and causing you to fall apart.
The first magnetar was discovered 40 years ago today. A wave of gamma rays swept across the solar system — the most powerful outburst seen to that time. It was detected by spacecraft in Earth orbit and beyond, allowing astronomers to pinpoint the source: clouds of debris from an exploded star.
It took a while for astronomers to understand what they were seeing, though: the star’s highly magnetized corpse, now called a magnetar.
A magnetar forms at the end of a massive star’s life. The star can no longer produce energy in its core, so the core collapses. The core is about twice the mass of the Sun, but it’s compressed into a ball only about a dozen miles across. The resulting “corpse” is known as a neutron star.
As the core shrinks, its magnetic field intensifies. The “squeezed” field can be more than a million million times the strength of Earth’s magnetic field.
The field is strong enough to trigger “quakes” in the star’s ultra-dense surface. These tremors produce intense outbursts of gamma-rays — like the one detected in 1979.
A magnetar’s magnetic field decays quickly. So in about 10,000 years, the magnetar loses most of its field — and settles into life as a “normal” neutron star. More tomorrow.
Script by Damond Benningfield | 0.860036 | 3.428198 |
The Lucy mission will be traveling to a record-breaking number of targets that independently orbit the Sun. Below there is a brief introduction to each target, including an artist’s conception of the target inspired by Earth-based observations. We won’t know what they really look like until Lucy gets there!
The first small body that Lucy will encounter is (52246) Donaldjohanson. This is the smallest of Lucy's targets, measuring only 4 km (2-3 miles) in diameter. While this object will mostly provide a test rehearsal for all of Lucy's instruments, it is also an interesting object itself as it has been identified as a fragment of a massive collision that occurred around 130 million years ago that produced the Erigone family of asteroids. Lucy will fly by this C-type asteroid on April 20, 2025.
The first Trojan Asteroid that Lucy will visit is (3548) Eurybates. Eurybates is much larger than Donaldjohanson with a diameter of 64 km (40 miles), but it does share some similarities. It is also a C-type asteroid and a member of a collisional family (the only known disruptional collisional family in the Trojans). The flyby of Eurybates will help us understand one of the mysteries of the Trojans: Why is the only collisional family in the Trojans a C-type, which, while quite common in the main asteroid belt, is quite rare in the rest of the Trojan swarm? And why are there no D-type families in either the asteroid belt or the Trojans? Maybe D-type asteroids disintegrate when they are hit? Maybe D-type asteroids become C type asteroids when they are hit? In January of 2019 the Lucy team learned that Eurybates has a satellite that is likely around 1 km (0.5 miles) in size. So this flyby will be two for the price of one! This flyby on August 12, 2027 should help answer these questions!
As Lucy continues to fly through the Greek camp of Trojan asteroids at L4, its next target is (15094) Polymele. This is the smallest of Lucy's Trojan targets at 21 km (13 miles) in diameter. It is a P-type asteroid, the same type as the much larger Patroclus and Menoetius binary. This will be the first time a spacecraft has ever flown by this dark, reddish class of asteroid that is believed to be rich in organics. Scientists think that Polymele is a collisional fragment of a larger P-type asteroid, and thus it will be very interesting to compare to its larger brethren. Lucy will fly by on September 15, 2027.
Lucy's next target is (11351) Leucus. This 34 km (21 mile) D-type asteroid rotates extremely slowly. Its day is 466 hours! This slow rotation period means that it will likely get hotter during the day and colder at night than the other asteroids, so by comparing it with other D-type asteroids we should learn more about the materials that make up these asteroids. Also, as it rotates its brightness as observed from Earth varies a lot, suggesting that it is quite elongated. Lucy will know for sure when it flies by on April 18, 2028.
Only a few months after the flyby of Leucus, Lucy will get a close up look of another D-type Trojan, (21900) Orus. Lucy will be able to compare this larger 51 km diameter Trojan to both the smaller Leucus, which is of the same type of very dark, very red objects thought to be rich in organics and carbon, and to the similarly-sized, but different spectrally typed, Eurybates. Lucy will fly by on November 11, 2028.
The final encounter of Lucy's primary mission will give two for the price of one. After a long journey from the Greek L4 swarm to the Trojan L5 swarm Lucy will fly by the binary pair of asteroids (617) Patroclus and Menoetius. They are large P-type Trojans, with average diameters of 113 km and 104 km (about 70 and 65 miles), respectively. Scientists hypothesize that they may be primordial asteroids left over from the very early Solar System. Lucy is very lucky to be able to fly by this large binary pair of asteroids because they are on a relatively high inclination heliocentric orbit (22 deg). This means that they spend most of their time above and below the ecliptic plane, in regions that are very difficult for a spacecraft to reach. Fortunately, the pair just happen to be passing through the region that is accessible to Lucy, allowing for this amazing flyby on March 2, 2033. | 0.806799 | 3.743602 |
For as long as I can remember, the night sky has been bathed in light pollution. While growing up in Southern Ontario, bright lights from the nearby cities would obscure all but the brightest of stars. In Vancouver the problem was exacerbated due to the sheer size of the city. In Japan, there are clear nights where even Orion's Belt is practically invisible due to the overwhelming intensity of omnidirectional lamps that scratch away at the darkness, as though the nation's residents were terrified of imaginary monsters that lurked in the shadows. Never have I seen the Milky Way with my own eyes. Never have I peered through a telescope to see the planets closest to our home. Despite all this, my passion for space and the exploration of the universe has been as constant as the northern star, and I'd like to do something with it.
In the summer of '99, I joined UCB's [email protected] project and have contributed a portion of my CPU cycles ever since. Over these 18 years, I've not been credited with a single discovery of an extraterrestrial signal but, as one might expect, neither has anyone else. Since this time, though, thousands of planets outside our solar system have been discovered and more are identified and confirmed every week. Most worlds are detected with methods such as measuring a star's radial velocity and transit photometry, or via reflection/emission modulations and relativistic beaming, or examination of ellipsoidal variations, pulsar timing, variable star timing and transit timing. All of these have worked in the past to identify worlds both large and small in our galactic neighbourhood. But I'd like to do something different. I'd like to use direct imaging to try and identify worlds around distant stars.
The problem is not a small one. Seeing a planet light years away amid the glare of its host star is akin to spotting a dime on the ground next to a bonfire from a kilometre away. It's not an impossible task, but it's not an easy one, either. There are dozens of teams at universities around the world working on this and, as of today, fewer than a dozen planets have been identified through direct imaging. They're all the size of Neptune or larger, and they're all pretty far away from their host star. What I'd like to do is take a crack at writing software that can help out.
NASA makes a lot of its data available to the general public, as do many universities around the world. What I hope to do is acquire a large number of images from various sources and begin the search for planets by writing the software that'll analyze photos from the same patch of sky again and again looking for differences. When something is found, then I can take a look and see what sort of pattern was found. If the results look like a planet orbiting a distant star, then I can see if the world has already been catalogued and perhaps pass on some more information. If the world has not been catalogued, then I'll be as giddy as a child on Christmas Eve. There are a lot of stars out there, and there's no reason to believe that I couldn't help the scientific community just a little bit, even if it turns out I've done little more than corroborate the existence of worlds already identified.
Ultimately, this will give me the ability to write some software that will hopefully add value to something that has genuinely fascinated me since I was a young boy watching Star Trek with my father. I don't get a lot of free time anymore, but I do have the opportunity to sit down, study patterns, and create algorithms that can do the same work with greater efficiency. Who knows, perhaps by working on software like this, another avenue will open up in the future.
One can certainly dream … | 0.893414 | 3.458533 |
Six months ago, satellite telescopes spotted an exceptionally bright burst of energy that would have been the most distant object in the universe ever visible to the naked eye, if anyone saw it.
Even though no humans have reported seeing it directly, the gamma-ray burst, an explosion that signals the violent death of a massive star, is changing theories of how these events look. Gamma ray bursts are typically accompanied by intense releases of other forms of radiation, from X-rays to visible light.
This burst, dubbed GRB 080319B, was first detected by the Swift satellite on March 19, while the spacecraft was serendipitously looking at another gamma-ray burst in the same area of the sky.
The light it emitted in the visible part of the spectrum was so intense that the burst would have been visible to the naked eye in the constellation Bootes for about 40 seconds — no other gamma-ray burst has ever been visible without a telescope.
The incredible amount of energy given off across the entire electromagnetic spectrum during a gamma-ray burst is what Jonathan Grindlay of the Harvard-Smithsonian Center for Astrophysics calls "the birth pangs of a black hole. This is the scream."
It took the light of GRB 080319B about 7.4 billion years to reach Earth, placing the explosion "more than halfway back to the Big Bang and the origin of our universe," Grindlay wrote in an editorial accompanying a new study of the burst in the Sept. 10 issue of the journal Nature.
This means that the explosion happened 3 billion years before the sun or Earth even formed, Grindlay added. When astronomers see such distant objects, they are in effect looking back in time.
After the Swift detection, telescopes around the world were alerted and trained their eyes onto the new gamma-ray burst, giving scientists a highly detailed view of these explosions — the most luminous in the universe — whose formation and structure still hold many mysteries. The findings in the new study of GRB 080319B challenge some of the commonly-held views of gamma-ray bursts.
A violent death and birth
Gamma-ray bursts are something of an extreme form of supernovas, the bright explosions that mark the deaths of massive stars.
But possibly one in every 1,000 supernovae is not one of these "normal" explosions; instead of the star simply dying, its core collapses to form a black hole — that event generates a gamma-ray burst. (Just what the conditions are that boost a normal supernova into a gamma-ray burst are not known.)
The gamma-ray burst is actually a powerful jet of material sent out by the spinning accretion disk that surrounds a newborn black hole. This bright part of the burst typically only lasts between 3 and 100 seconds, and an afterglow follows that can last for days or weeks.
GRB 080319B's jet was one of the brightest ever observed in terms of gamma rays, and it was unusually bright in optical wavelengths.
"It was unexpected that it was this bright," said lead author of the new study Judith Racusin, a graduate student at Penn State University.
The study suggests that the jet of the gamma-burst actually has two components: a narrow, ultra-fast jet at the core of a wider, slightly slower jet.
The narrow part of the jet of GRB 080319B was so fast that it shot material directly toward Earth at 99.99995 percent the speed of light.
Scientists think that it was because the jet was pointed straight at us that it appeared so much brighter than previously-observed gamma-ray bursts. The researchers speculate that it is rare to detect the inner core of the jet because it is so narrow — only about 1/100th the size of the full moon as seen from Earth.
For this reason, astronomers think they may have missed the narrow core of the jet in previous bursts: "We're primarily just seeing the outer jet," Grindlay told SPACE.com, because we are not seeing those bursts head-on.
Racusin said that it isn't know for sure that all gamma-ray bursts have this two component structure to their jets, but that the theory fits what they saw with GRB 080319B.
To see a similarly bright burst, astronomers would have to catch another one aimed directly at Earth, which Racusin and her colleagues calculated should happen about once ever three to 10 years.
Swift may not still be around in 10 years, but the recently launched GLAST satellite (recently renamed Fermi) and other missions in the planning stages could catch a glimpse of them.
But whether or not they do, Racusin knows one thing: With GRB 080319B, "we got lucky." | 0.854889 | 4.050913 |
Fifty years ago Saturday, more than half a billion people watched Neil Armstrong become the first human to set foot on another celestial body. Necessary and impressive though they are, no robotic explorer could ever generate so much attention. We want to go. People yearn to explore space, if not ourselves personally, then at least vicariously through our astronaut proxies.
The most important reasons for the human expansion into space are not the standard things you hear all the time from the space agencies—the jobs, wealth creation, or even new science. It has more to do with human nature and the way we will change as we move into this new frontier. Dr. Charles Laughlin, emeritus professor of Carleton University’s Department of Sociology & Anthropology, said that these changes are so important that the establishment of a permanent, self-sufficient, human presence in space will become our most crucial activity over the next century.
This is not merely a science fiction-driven fantasy. Manned space exploration satisfies a basic human drive to engage in geographic exploration in a way no other activity does in today’s world. The fact that Star Trek became a global phenomenon suggests that there is far more to the popular appeal to “boldly go where no one has gone before” than most people understand. We need to look to the social sciences—anthropology, history, and psychology, for example—to properly understand this phenomenon.
Laughlin explained that the drive to engage in geographic exploration is an important part of us. It is a characteristic of the way in which the higher orders of the human nervous system function—the awareness of new physical frontiers is essential to the health of humanity. American anthropologist Dr. Ben Finney labeled humans “the exploring animal” and maintained that a withdrawal from the exploration and development of space would put the brakes on our cultural and intellectual advancement. A quick look at the history of our species shows why satisfying this urge is a crucial part of what it means to be fully human.
The ancestors of modern human beings began as a population of only a few hundred thousand individuals in the tropical regions of Sub-Saharan Africa. Around 1-2 million years ago, they began to expand into new habitats and gradually migrated into Europe and Asia, and from there into Australia, Oceania, the New World and, eventually, as modern human beings, even to Antarctica. And the migration did not stop there. People have now lived under the ocean in submarines and research stations, briefly on the Moon, and in low Earth orbit.
In other words, it is in our very nature to explore and expand outwards into available spaces. It is clearly an extension of this drive that motivates our intense desire for a manned space program.
The idea that exploration is a genetic imperative isn’t surprising if you consider the survival advantages that an expansionary species has over one which never moves beyond a single ecosystem. That is one of the reasons Space X founder Elon Musk gives for his efforts to reduce the cost of space exploration to hopefully open up the cosmos to humans. Musk is afraid that one day there will be another mass extinction event and then the human race would end if all of us stayed here. Musk said, “We must preserve the light of consciousness by becoming a spacefaring civilization [and] extending life to other planets.”
Relying on robots is not enough. However useful they are for science, and preparing the way for us, robots will never replace red-blooded astronauts. Sharing adventures with other people has given us psychological benefits since our ancestors first told stories around the fire. Even today, tales of exploration by human adventurers tend to balance the often-negative mind states generated by people facing the stresses and frustrations of daily life. Throughout history, our most treasured stories have been about heroes who do remarkable things and have extraordinary adventures. We love to talk about heroes. They inspire us, because they represent the drive to accomplish the seemingly impossible, to go beyond the horizons of mundane human limitations. By sending special people out into space we personify a shared vision of what we humans may one day become: citizens of the solar system, citizens of the Milky Way, citizens of the universe.
Yet, in a way, this is nothing new. Historians have shown us that geographic exploration has been an invigorating activity for civilizations throughout history. Whether it was the European exploration of the world, the massive Chinese expeditions along the coasts of Southeast Asia, India and Africa or the impressive reed boat voyages of the Polynesians and Micronesians in the vast Pacific, there has always been a strong correlation between geographic exploration and general cultural vitality. Arizona State University historian Stephen Pyne asserts, “Choosing to explore the solar system will not, by itself, assure us continued status as a world civilization. But choosing not to explore will ensure that we will not retain that stature.”
Finally, the exploration and development of space is a catalyst encouraging the next phase in the evolution of our species. Each movement outwards to face new and more difficult living conditions will be accomplished by a very select group, people who possess the physiological and mental attributes to survive in ever more challenging conditions. These pioneers will combine the very best characteristics of humanity—good health, the ability to work well with other people, advanced systems consciousness (the understanding that they are part of an environmental system that must be properly cared for) and of course high intelligence—all characteristics we urgently need at this time in history to solve our global problems. Space colonization will have the effect of accelerating the adoption of these characteristics as successive waves of humanity move out to settle the high frontier.
Finney maintained that “the space revolution is leading humanity into an entirely new and uncharted social realm.” He predicted that the act of settling space “will change humankind utterly and irreversibly.” As much as possible with the enormous distances involved, we will certainly want to remain in touch with our extraterrestrial cousins, for they will become our teachers in ways we have yet to imagine.
Tom Harris is former aerospace engineer and an Ottawa-based science and technology writer and public speaker. He may be contacted at [email protected]. | 0.865143 | 3.181292 |
Seeing Stars – Inverness Courier, Friday 3rd June, 2005
Here Comes the Sun
By Andy Ferguson
4,600 million years ago a huge, cold cloud of hydrogen gas, mixed with minute dust particles from old supernova explosions, received a wake up call. A passing star, or perhaps another nearby stellar explosion, caused a shock wave to pass through this cloud and as a result, it began to compress. Gravity took over and the cloud began to spin and flatten into a disk. As the gas moved towards the centre of the disk, the rocky particles began to collide, stick together and accumulate into planets. The remnants of gas in the extremities of the disk formed into giant gas planets.
Meanwhile, the gas at the centre of the disk had compressed into a huge spinning sphere. Enormous pressure and temperature built up in the centre of the sphere and eventually reached a point where thermonuclear fusion reactions were triggered, converting hydrogen into helium and releasing vast quantities of energy and light in the process. The resulting initial blast blew away the remaining gas and small particles in the disc – The Sun and Solar System had been born.
The Sun, actually a star with, as far as stars go, a modest diameter of 1.4 four million kilometres, is the dominant direct energy input into the terrestrial ecosystem. It affects all physical, chemical and biological processes on Earth. It takes a million years for the heat produced in the core to work its way to the surface but only 8.3 minutes to reach us. As a result of the nuclear fusion, the Sun is losing about 5 million tons of mass per second. Don’t worry; there is enough of it to last another 5 billion years or so.
From an estimated 20 million degrees at the core the temperature drops to 4 million degrees in the convection zone, where convective cells carry the heat to the surface, or photosphere. This is the part of the Sun we normally see and is a relatively cool 5,800 degrees. Despite the massive size of the Sun, the photosphere is only a few hundred kilometres thick and the surface is covered by the tops of the convective cells, which are called granules, giving the surface a mottled appearance.
Sunspots are darker, cooler areas of the photosphere where the magnetic fields of the convective cells block heat from getting to the surface. They lie slightly below the surface. This is most visible when the sunspots are near the limb and is called the Wilson Effect, after Scottish astronomer Alexander Wilson who first observed it. Around the dark sunspot is the slightly lighter, and frilly, penumbra. Above the photosphere is the Sun’s atmosphere or Corona. This cloud of charged particles is a million degrees C and only visible with specialised equipment, or during the brief moments of a total solar eclipse.
Expensive hydrogen-alpha filters show bright luminous hydrogen clouds, called faculae, above areas where sunspots are about to form. Due to the magnetic disturbances around sunspots, flares, or filaments, can often be seen emanating from them. Occasionally, magnetic reconnection takes place and a huge explosion of plasma, called a coronal mass ejection, or CME, takes place. Billions of tons of charged particles are hurled into space, sometimes towards Earth, where they give us the ethereal Aurora Borealis, damage satellites, interfere with radio and television and even overload power grids. Astronauts have to shelter in screened compartments on the International Space Station to avoid radiation poisoning from gamma rays. Fortunately Earth’s magnetic field protects us from real harm. H-alpha filters also show huge prominences, many times the size of Earth and jutting from the surface into the Corona, as huge loops of fire arcing off the surface and crashing back down thousands of miles away.
Our Sun is a giant dynamo that produces a huge magnetic field which is largely responsible for the phenomena we can see and for blasting out particles throughout the Solar System. Far from being a quiet, stable star, the Sun goes through an 11 year cycle, producing large crops of sunspots at its peak and reversing its magnetic field before taking a rest for a few years. It is currently slipping into its quiet phase.
Despite being our nearest star, the Sun still holds many mysteries we have so far been unable to solve. Current space missions, like Soho, Trace and Ulysses, continue to investigate, photograph and monitor it, to try and improve our current level of knowledge.
WARNING! viewing the Sun can be highly dangerous!! Even looking at it with the naked eye can damage your eyesight. Using unfiltered binoculars or telescopes will permanently damage eyesight or cause blindness in a fraction of a second. Specialised filters are the only safe way to observe with these instruments. Inexpensive ‘White light’ filters can be used to view sunspots and granulation but the safest way to observe is by ‘eyepiece projection’ onto a white card. A telescope or one ‘leg’ of a binocular (blank off the unused one at the front) is aimed at the Sun and an image projected from the eyepiece onto a white card, or similar. To increase image visibility you can put a guard made of cardboard around the instrument to block off extraneous light. | 0.854857 | 3.610708 |
Impact craters are formed on a planet or moon when a smaller object collides with the surface at a very high velocity (typically 15 000 ms-1). An impact crater is identifiable by its approximately circular shape, raised rim, pattern of ejected material and crater floor that is lower than the surrounding surface.
Many objects in the Solar System, for example Mars, Earth’s Moon and Mercury, have their surface covered in impact craters. For other objects, including the Earth, visible impact craters are far less common; these objects have active geological processes and the impact craters become weathered over time.
The smallest impact craters on a planet’s surface are called simple craters, because they have simple bowl-like shapes. These craters are excavated when an impactor, i.e. an asteroid or comet hits the surface creating a shock wave that radiates into the crust of the planet.
Download Stage 1, 2 and 3 of simple cratering
Large impactors, i.e. asteroids and comets, produce complex craters with crater walls that are so steep they are prone to collapse and uplifted rock in the centre that forms high central peaks or central peak rings.
Contact [email protected], for further information. | 0.856724 | 3.235034 |
Astronomers have found the most massive neutron star yet discovered, a rapidly rotating pulsar orbiting in lockstep with a white dwarf that crams 2.17 solar masses into a city-size sphere just 30 kilometres (18.6 miles) across. The pulsar appears to be close to the tipping point between matter’s ability to resist the crush of gravity versus collapse into a black hole.
“Neutron stars are as mysterious as they are fascinating,” said Thankful Cromartie, a graduate student at the University of Virginia and a pre-doctoral fellow at the National Radio Astronomy Observatory in Charlottesville, Virginia. She is first author of a paper accepted by Nature Astronomy.
“These city-sized objects are essentially ginormous atomic nuclei. They are so massive that their interiors take on weird properties. Finding the maximum mass that physics and nature will allow can teach us a great deal about this otherwise inaccessible realm in astrophysics.”
Neutron stars and their fast-spinning cousins – pulsars – are formed in supernova explosions when the core of a massive star runs out of nuclear fuel. In the sudden absence of fusion energy radiating outward, gravity takes over and the core collapses, blowing away the star’s outer layers in spectacular fashion.
Depending on how much mass is present, the collapse will either halt due to quantum mechanical effects, leaving a compact neutron star in its wake, or continue to the point where a black hole forms.
Observations of gravity waves generated in the merger of two neutron stars suggests that tipping point is very close to 2.17 solar masses.
“Neutron stars have this tipping point where their interior densities get so extreme that the force of gravity overwhelms even the ability of neutrons to resist further collapse,” said Scott Ransom, an astronomer at NRAO and coauthor on the Nature Astronomy paper. “Each ‘most massive’ neutron star we find brings us closer to identifying that tipping point and helping us to understand the physics of matter at these mindboggling densities.”
The newly confirmed record holder is a millisecond pulsar known as J0740+6620. In a chance alignment, the pulsar and it’s white dwarf companion orbit each other edge on as seen from Earth.
Cromartie and her colleagues took advantage of that alignment to measure the mass of the white dwarf. Because the mass of the dwarf distorts the space around it in accordance with Einstein’s theory of general relativity, radiation from the pulsar is delayed on its way to Earth by about 10 millionths of a second when the pulsar passes behind its companion.
That delay was a direct indication of the white dwarf’s mass and from that, along with the time needed to make one rotation, the researchers could calculate the mass of the pulsar.
“The orientation of this binary star system created a fantastic cosmic laboratory,“ Ransom said. | 0.874544 | 3.988284 |
Record-Setting X-ray Jet Discovered
This composite image shows the most distant X-ray jet ever observed. X-ray data from NASA's Chandra X-ray Observatory are shown in blue, radio data from the NSF's Very Large Array are shown in purple and optical data from NASA's Hubble Space Telescope are shown in yellow. The jet was produced by a quasar named GB 1428+4217, or GB 1428 for short, and is located 12.4 billion light years from Earth. Labels for the quasar and jet can be seen by mousing over the image. The shape of the jet is very similar in the X-ray and radio data.
Giant black holes at the centers of galaxies can pull in matter at a rapid rate producing the quasar phenomenon. The energy released as particles fall toward the black hole generates intense radiation and powerful beams of high-energy particles that blast away from the black hole at nearly the speed of light. These particle beams can interact with magnetic fields or ambient photons to produce jets of radiation.
As the electrons in the jet fly away from the quasar, they move through a sea of background photons left behind after the Big Bang. When a fast-moving electron collides with one of these so-called cosmic microwave background photons, it can boost the photon's energy into the X-ray band. Because the quasar is seen when the universe is at an age of about 1.3 billion years, less than 10% of its current value, the cosmic background radiation is a thousand times more intense than it is now. This makes the jet much brighter, and compensates in part for the dimming due to distance.
-Megan Watzke, CXC
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Read the privacy statement | 0.865553 | 3.361603 |
Everyone who isn’t Christopher Hitchens or Richard Dawkins already knows about the standard fine-tuning argument. But have you ever considered what it takes to make a planet that is capable of supporting the minimal requirements of living systems? The area of science that specializes in answering this question is called astrobiology. Let’s take a look!
I will be working from a lecture (with Q&A) delivered in October 2007 at California State University – Fresno, by two of my favorite scholars, Jay Wesley Richards and Guillermo Gonzalez.
The Copernican Principle
Richards introduces the idea of the Copernican Principle. This principle states that the progress of science will show that there is nothing special (designed) about man’s place in the universe.
The minimal requirements for life
I’ve written about this before here, but basically life requires a minimum amount of encoded biological information to allow it to replicate itself. The only element in the periodic table that allows you to encode information is carbon. Carbon is the hub of large molecules which form the paper and text of biological information. No carbon = no life.
Secondly, you need some environment in which to form molecules around the carbon, such as amino acids and proteins. That environment is liquid water. And you need the liquid water to be at the surface the planet where you want life to exist.
The requirements of a habitable planet
Here are just a few of the requirements mentioned in the lecture.
- a solar system with a single massive Sun than can serve as a long-lived, stable source of energy
- a terrestrial planet (non-gaseous)
- the planet must be the right distance from the sun in order to preserve liquid water at the surface – if it’s too close, the water is burnt off in a runaway greenhouse effect, if it’s too far, the water is permanently frozen in a runaway glaciation
- the solar system must be placed at the right place in the galaxy – not too near dangerous radiation, but close enough to other stars to be able to absorb heavy elements after neighboring stars die
- a moon of sufficient mass to stabilize the tilt of the planet’s rotation
- plate tectonics
- an oxygen-rich atmosphere
- a sweeper planet to deflect comets, etc.
- planetary neighbors must have non-eccentric orbits
Note that these requirements are connected. If you mess with one, some of the others will be thrown out of tune. For more habitability requirements, see this article by Gonzalez and Richards.
What are the probabilities that we will get these conditions?
Richards explains that the question of whether this is designed is like winning the lottery. Your chance of winning depends on two things:
- the odds of getting all the conditions correct
- the number of tries that you get
If the odds of winning are 1 in a million, you could still win by buying a million tickets with all the different numbers. In the universe, there are only about 10^22 possible solar systems. So if the odds of getting a habitable planet are 1 in 10^9, you’ll get tons of life. But what if the odds are 1 in 10^40? Then you’re not likely to win.
But this is not the argument that these two are making, because even though there are a lot of factors needed for a habitable planet, we still can’t say for certain how likely it is that each of these conditions will obtain. Therefore, we can’t make the argument except by estimating the odds of getting each condition.
Although you could use very generous estimates, it would still be guessing, and you can win a debate by guessing. So are we stuck?
How to make a design argument using habitability
Gonzalez explains why you can still make an argument for design by arguing that the coorelation between habitability and measurabiliy is intentional. (By measurability, he really means the ease of making scientific discoveries). And you do this by correlating the conditions for sustaining life with the conditions for allowing scientific discoveries.
Gonzalez gives two examples:
- Solar eclipses require that the sun and moon have certain sizes and certain distances from the sun. The surface of the Earth is the optimal location in our solar system for observing solar eclipses. We were able to make many valuable discoveries due to this fine-tuning, not the least of which was confirming the theory of general relativity, which was cruicial to the science of cosmology.
- The location of our solar system is fine-tuned within two spiral arms of a spiral galaxy. We escape from radiation and other dangers, but to also allow use to capture heavy elements that are needed to make a suitable Sun and humans bodies, too. But the same conditions that allow life also allow us to make scientific discoveries, such as star formation theory and cosmic microwave background radiation measurements, which was needed in order to confirm the creation of the universe out of nothing (the big bang).
Spooky. And what until they list off a half-dozen more examples in their book “The Privileged Planet”. It’s downright terrifying!
Richards sums up the argument with an illustration. He asks why scientists construct observatories high up on mountains. The answer is in order to avoid “light pollution” from nearby cities, which ruin the ability of scientists to observe the stars and make discoveries. And this is what we see with our planet and solar system. No one builds a planet that can be used to make scientific discoveries in a place that doesn’t support life. It turns out that the very places in the universe that are good for making observations are also the best places for supporting life.
I would recommend checking out the documentary DVD, if you find the book too scary. There is also a university lecture DVD with both authors, filmed at Biola University. If you want to see the DVD online for FREE, then click here (narrated by John-Rhys Davies). Awesome! Go science! | 0.84437 | 3.369306 |
To infinity, ... and beyond
How vast is the universe? That's one question Dr. Jenniferpursues as an astronomer and senior project scientist for the Hubble Space Telescope. A standing-room-only crowd turned out Saturday to hear the Mountain Home native discuss what scientists are learning about the universe, especially through Hubble.
More than 160 people packed the Knox Community Room of the Donald W. Reynolds Library for her presentation on the Hubble's 25anniversary and what the world is learning from its discoveries.
told the audience that growing up on a cattle ranch in Mountain Home is where she first encountered the stars, and where her love of astronomy began. She said on clear nights her family would go for walks and she'd gaze into the sky, enraptured by the stars and vastness.
As Mountain Home's grown through the years, and more light fills the night sky, it's become more difficult to see what she saw as a child, althoughpointed out that putting domes over street lamps to keep light focused on the ground can prevent the light pollution. But, she added, you still can go out to a truly dark place and see the "full grandeur of the night sky."
Much of her nearly 11/2-hour program involved photos from Hubble during its 25 years in orbit above Earth. From its position, unobstructed by clouds and the atmosphere, the space telescope can see far into the universe and has produced spectacular finds, she said. It's enabled scientists to see more than they ever have before, according to , from the birth of stars to their deaths, from how galaxies form to finding new planets circling other stars.
In the short time of Hubble's existence, astronomers have learned far more than they have since Galileo first turned a telescope skyward in the 16century, according to . For example, she said prevailing theories about the universe for years had been that its expansion will one day stop, or that gravity eventually will make it collapse back in on itself. Those were the main schools of thought when the 1983 Mountain Home High School graduate entered the astronomy field.
But in 2011, three scientists — two of whom were in graduate school with her, said— won the Nobel Prize for their research showing the universe not only continues expanding, but does so at an increasing rate.
With the Hubble Space Telescope,said, astronomers and scientists are able to see farther into the universe, and farther back in time, because the furthest reaches are some of the oldest-known parts thrown out by the "Big Bang," or, as she likes to call it, the "Let there be light" theory. Thanks to Hubble, researchers are learning there may be billions of galaxies throughout the universe, she said.
As humankind discovers more about the universe, science opens the door to more philosophical questions and thought, said, questions such as, "What will be the long-term future of the universe?" and, "Are we significant given the vastness of the universe in size and time, or even the possibility of a ?"
The Hubble Space Telescope was built to be serviced by astronauts, but in 2009, it saw its final servicing with the cessation of the shuttle missions.showed a video she shot of the launch of the Space Shuttle Atlantis for that mission, and said that during the mission, she got to be in the mission control room. said they let her work with communications, "like Lt. ." ( was a communications officer in the TV series Star Trek.)
said scientists hope to keep Hubble working through 2020, and that it will be replaced by the James Webb Space Telescope which, with more technologically advanced equipment and higher orbits, should give astronomers and scientists an even more spectacular view of the universe. | 0.816246 | 3.452607 |
UPDATE: Photos of the Moon, Mercury, Jupiter and Mars Conjunction from the 23rd February.
Conjunctions of the Moon and Planets can be quite special events, as we saw on December 1st 2008 when The Smiley Face Conjunction graced our skies. A conjunction is an alignment or grouping together of 2 or more celestial bodies (usually the moon and planets) in the sky, from our vantage point on Earth. The objects aren’t necessarily physically close to each other in space, but from where we see them, we call the grouping a conjunction.
A conjunction doesn’t have any particularly special meaning, but they can be interesting to observe because very close conjunctions are quite rare events. It can be very exciting to see two planets in the same field of view of your telescope! Not only that, but conjunctions, especially with the moon and/or bright planets are involved, are just a lovely spectacle to look at and photograph.
Given that, there’s a few conjunctions coming up later in February and in late April that are worth getting up early to see and photograph:
- February 23rd: Conjunction with the Moon, Jupiter, Mercury and Mars (Photos here)
- February 25th: Conjunction with Jupiter, Mercury and Mars
- April 23rd: Conjunction with the Moon, Venus and Mars
Continue reading for more information including sky charts and tips for observing and photographing the conjunctions.
All three conjunctions appear in the pre-dawn sky low in the East, and are best observed from around 30-60 minutes before dawn local time. They will be able to be seen until the sky brightens too much due to the rising sun.
All you need is a pair of eyes and a good unobstructed Easterly aspect. If you have trees or houses to the East, head to the nearest beach, lake or park to see the conjunction and watch the sunrise as well.
Sky Chart – 23rd February: Moon, Jupiter, Mercury and Mars
The trio of planets actually start converging earlier in February, and on the 18th February, Mars and Jupiter are at their closest – only 33 arc minutes apart (that’s just over half a degree, or about the width of the full moon). At that distance, they’ll be able to be seen in the same field of view of most telescopes with a wide field eyepiece.
On the 22nd February, the trio of planets is joined by the Moon, and the 4 bodies form an almost straight line in the East.
On the 23rd February, the thin waning Crescent Moon and Mercury are under 1 degree apart, with Jupiter 1.5 degrees below Mercury, and Mars almost 3 degrees further below. See the screenshot below for a sky chart.
Sky Chart – 25th February: Jupiter, Mercury and Mars
On the 24th and 25th February, the Moon departs the scene while Jupiter and Mercury converge closer together. On both the 24th and 25th, they are approx 50 arc minutes apart – just under 1 degree. Mars still hangs around 3 degrees below the pair.
See the screenshot below for the sky chart of the 25th February.
Sky Chart – 23rd April: Moon, Venus and Mars
Skipping forward now, over the next few weeks Jupiter rises earlier and is higher in the sky, while Mars continues it’s northward trek. On the 2nd March, Mercury and Mars are just 30 arc minutes (half a degree) apart though they’ll both be fairly dim.
Venus appears in the morning sky in early April, and on April 23rd the thin waning crescent Moon joins Venus and Mars for a conjunction with the trio forming a triangle separated by 3-4 degrees.
Uranus isn’t too far away, but will be too dim to see naked eye. The Sky Chart below shows the scene.
How to Photograph a Conjunction
Photographing these conjunctions is generally quite easy, and most cameras, even the compacts, will do a reasonable job of it however you’ll get better results with the cameras that allow you to adjust the settings manually to capture a longer exposure.
- A camera
- A tripod
- A pleasing foreground
- An obstructed view to the East
In general, you’ll need an exposure of around 1 to 4 seconds, so the tripod is a must. Of course with digital, it’s very easy to preview your shot afterwards and adjust accordingly – so take lots of shots of varying exposures until the scene is well lit (not underexposed) but not overexposed in your preview screen.
It’s easy to take pictures from home with powerlines or rooftops in the view, but the most pleasing shots will be the ones where you make an effort to get to a spot with a nice scenic foreground to compose with the conjunction in the sky. Make sure you give yourself plenty of time to arrive at your location, find the best spot and set up your tripod and camera.
The conjunction isn’t over in an instant so you have time to recompose, try different settings etc, but remember that the dawn light can change very rapidly so it might help to go out a day or two before to find the best location and take some practise shots in similar conditions at a similar time of day. Even just that 1 day of practise can mean the difference between an ok shot and a great shot.
They’re one of my favourite scenes to photograph – a terrestrial landscape photo with some astronomical interest in the sky. If you need a little inspiration, why not check out my Conjunction Photo Gallery to see how I’ve captured them in the past.
If you capture some images of any of these conjunctions, I’d love to see them! Either post the links here in the comments section, or post them in the IceInSpace Solar System forum.
Thanks for reading. | 0.85873 | 3.373346 |
aerodynamic heating(redirected from Aerothermal heating)
aerodynamic heating[‚e·ro·dī′nam·ik ′hēt·iŋ]
heating of a body which moves through air or another gas at a high velocity. Aerodynamic heating results from the fact that air molecules flying against the body cause localized braking of the body. If a flight proceeds at a supersonic velocity, the effect of braking is primarily that of a shock wave, which is produced in front of the body. Further deceleration of air molecules occurs at the very surface of the body, in the so-called boundary layer. As a result of deceleration, the thermal energy of air molecules increases; that is, the temperature of the gas near the surface of the moving body increases. The maximum temperature to which a gas in the vicinity of the moving body can be heated is close to the so-called stagnation temperature:
To = Tn + v2/2Cp
where Tn is the temperature of the impacting air, ν is the velocity of the body in flight, and Cn is the specific heat capacity of the gas at constant pressure. Thus, for example, in the flight of a supersonic aircraft at three times the speed of sound (about 1 km/sec), the stagnation temperature amounts to about 400°C, whereas in the reentry of a spacecraft into the earth’s atmosphere at the first cosmic velocity (8.1 km/sec), the stagnation temperature reaches 8000°C. If in the first case for a sufficiently extended flight the temperature of the shell of the aircraft reaches such a temperature, then in the second case the surface of the spacecraft will surely disintegrate as a result of the inability of the material to withstand such high temperatures.
Heat is transferred to the moving aircraft from the region of superheated gas, resulting in aerodynamic heating. Two forms of aerodynamic heating exist—convective and radiative. Convective heating is a consequence of heat transfer from the outer “hot” part of the border layer to the surface of the body. Quantitatively, convective heat flow is defined by the equation
qk = ∝(Te − T)
where Te is the equilibrium temperature (the limiting temperature to which the surface of the body would be heated if there were no energy outflow), Tw is the actual temperature of the surface, and a is the coefficient of convective heat exchange, which depends on the velocity and altitude of the aircraft, on the shape and dimensions of the body, and on other factors. The equilibrium temperature is close to the stagnation temperature. The type of dependence of the coefficient a on the enumerated parameters is determined by the conditions of flow in the boundary layer (laminar or turbulent). In the case of turbulent flow, convective heating becomes more intensive. This is bound up with the fact that besides molecular heat conduction, an essential role in the transfer of energy is played by turbulent velocity pulsations in the boundary layer.
As the aircraft velocity increases, the temperature behind the shock wave and in the boundary layer grows, as a result of which dissociation and ionization of molecules occur. This produces atoms, ions, and electrons which are diffused into a colder region—against the surface of the aircraft. At that point, the reverse reaction occurs (recombination), proceeding with the liberation of heat. This also contributes to the process of convective aerodynamic heating.
At aircraft velocities on the order of 5,000 m/sec, the temperature behind the shock wave becomes significant, and the gas begins to radiate. As a consequence of the transfer of radiant energy from the area of superheated temperatures to the surface of the aircraft, radiative heating occurs. Radiation in the ultraviolet regions of the spectrum plays an important role in radiative heating. For an aircraft in the earth’s atmosphere at a velocity below the first cosmic velocity (8.1 km/sec), radiative heating is small as compared with convective. At the second cosmic velocity (11.2 km/sec), their values become close, and at aircraft velocities of 13–15 km/sec and higher, corresponding to the speed of return to earth after flights to other planets, radiative heating makes the major contribution.
A special case of aerodynamic heating pertains to the heating of a body moving in the upper layers of the atmosphere, where the streamline condition involves free molecules; that is, the length of the free path of air molecules is commensurate with and even exceeds the dimensions of the body.
A particularly important role is played by aerodynamic heating in the entry of spaceships into the earth’s atmosphere (for example, Vostok, Voskhod, Soiuz). Spaceships neutralize aerodynamic heating through the installation of special heat-shielding systems.
REFERENCESOsnovy teploperedachi v aviatsionnoi i raketnoi lekhnike. Moscow, 1960.
Dorrance, W. H. Giperzvukovye techeniia viazkogo gaza. Moscow, 1966. (Translated from English.)
Zel’dovich, la. B., and Iu. P. Raizer. Fizika udarnykh voln i vyso-kotemperaturnykh gidrodinamicheskikh iavlenii, 2nd ed. Moscow, 1966.
N. A. ANFIMOV | 0.85937 | 3.60154 |
A piece of a planet that survived the cataclysmic explosion of its star has been spotted orbiting the stellar corpse. This gives us a glimpse of what our solar system may look like when the sun dies.
Christopher Manser at the University of Warwick in Coventry, UK, and his colleagues noticed something unusual when they were observing a white dwarf — the remnant of a star that has consumed all of its fuel — 400 light years away.
The team were looking at a dusty ring around the star thought to be formed from planets destroyed when the dying star exploded in a supernova. They detected a fluctuation in the wavelength of the light emitted by the dust. The signal repeated every two hours, suggesting there was a moving stream of gas in the ring, orbiting the white dwarf rapidly.
Although the team is unable to see the source of the gas because it is small and faint, Manser says it is probably a solid object like an asteroid or a piece of a planet. It may have a radius of 400 kilometres, almost as big as that of Ceres, the largest asteroid in our solar system. It is probably producing gas as it sublimes or collides with dust particles as it whirls around the white dwarf.
Moreover, the object is very close to the white dwarf because it completes a full orbit every two hours – if it was in the same orbit in our solar system, it would be inside the sun, Manser says.
That means it must be very dense and perhaps made of iron or other heavy metals to prevent it from being torn apart by the white dwarf’s gravity, he says.
“Most rocky planets in our galaxy are also composed of the same elements,” says Ben Zuckerman at the University of California, Los Angeles. So he suggests that planets in our solar system could share the same fate.
Experience Argentina’s 2020 total solar eclipse: Witness a rare celestial event on a New Scientist Discovery Tour
It is thought that our sun will die in about five billion years, and Mercury, Venus and Earth will almost certainly be engulfed in the explosion, but Mars, which is further from the sun, may survive and continue to orbit the remains.
Journal reference: Science, DOI: 10.1126/science.aat5330
More on these topics: | 0.904898 | 3.77271 |
Image credit: Hubble
The most recent photos released from the Hubble Space Telescope show objects so old they might be from a time when stars in the universe were just starting to shine in significant numbers – about 13 billion years ago. These objects are at the limit of Hubble’s resolving power, but the next generation James Webb Space Telescope is expected to see the entire group of proto-galaxies, and look back even further.
Researchers using NASA’s Hubble Space Telescope reported today they are seeing the conclusion of the cosmic epoch called the “Dark Ages,” a time about a billion years after the big bang when newly-formed stars and galaxies were just starting to become visible.
“With the Hubble Telescope, we can now see back to the epoch when stars in young galaxies began to shine in significant numbers, concluding the cosmic ‘dark ages’ about 13 billion years ago,” said Haojing Yan, a Ph.D. graduate student at Arizona State University (ASU). The results are being presented at the meeting of the American Astronomical Society in Seattle, WA.
Current theory holds that after the big bang that created the universe, there was a time of expansion and cooling that led to what is known as the “dark ages” in cosmic terms. The universe cooled sufficiently for protons and electrons to combine to form neutral hydrogen atoms and block the transmission of light. This epoch started about 300,000 years after the big bang, and may have ended about a billion years later. Stars and galaxies started to form at some point during this era, but the omni-present neutral hydrogen in the universe absorbed the ultraviolet light produced by stars and can not be seen by current telescopes.
The ASU team reports that Hubble’s Advanced Camera for Surveys (ACS) is revealing numerous faint objects that may be young star-forming galaxies seen when the universe was seven times smaller than it is today and less than a billion years old.
This was an important transition in the evolution of the universe. Because ionized hydrogen does not absorb ultraviolet light as easily as neutral hydrogen, the Dark Ages came to an end when enough hot stars had formed that their ultraviolet light pervaded the universe and re-ionized the neutral hydrogen. The shining stars opened a window for astronomers to look very far back into time.
“The objects we found are in the epoch when the universe started to produce stars in significant numbers ?- the hard-to-find young galaxies,” says Rogier Windhorst, professor of astronomy at ASU. “These galaxies are at the boundary of the directly observable universe.”
The ASU team found the objects while examining a small portion of the sky in the spring zodiacal constellation Virgo. This particular area of the sky contains no known bright galaxies, helping reduce light contamination in the observations. The entire ACS field of view shows about thirty such faint red objects. The distances to the suspected young galaxies are believed to be quite large, based on how red the observed objects are compared with nearby galaxies.
Based on this sample, the ASU researchers estimate that at least 400 million such objects filled in the entire universe at this cosmic epoch, to the limit of this Hubble image. And, they say they are able to see only the tip of the iceberg with current telescopes such as Hubble. NASA’s planned 7-meter James Webb Space Telescope is expected to see the entire population of these proto-galactic objects after it is launched in 2010.
Original Source: Hubble News Release | 0.850776 | 4.009021 |
How Are the Surfaces of the Moon & Mercury Similar?
As the smallest planet in the solar system, Mercury often stands in comparison not to other planets but to Earth's moon, which NASA categorizes as only slightly smaller than the first planet from the sun. Mercury and the moon have more in common than their sizes, however. The appearances of their surfaces and the nature of substances found in and on top of those surfaces form the basis of similarities between these two bodies.
Rocky, Cratered Surfaces
People may be tempted to compare Mercury and the moon because one's surface looks much like the other's. Both Mercury and the moon have surfaces, or crusts, composed almost entirely of rock and pocked with craters. Unlike Earth, which has an element-rich atmosphere in which incoming meteorites often burn, Mercury and the moon have thin atmospheres, called exospheres, that hold little gas and offer little insulation. Their craters are considered evidence of numerous meteorite strikes.
Signs of Volcanic Activity
Additionally, their surfaces bear other features that, though resembling craters, actually are believed to be long-dormant volcanoes. Different from Earth's tall, mountainous monoliths, many of Mercury's volcanic structures likely resulted from lava oozing from vents in the crust. According to David Blewett of Johns Hopkins University, the lava spread from the vents and settled over Mercury's surface. Volcanoes on the far side of Earth's moon, where steep-sided domes dot the surface, may be the product of similar activity.
Evidence of Polar Ice Masses
Looking at what lies above these bodies' geological markings, scientists have observed evidence of ice at the magnetic poles of both Mercury and the moon. Messenger, an exploratory spacecraft sent to Mercury in 2011, discovered hydrogen at the planet's north and south poles in amounts consistent with frozen water. Recent investigations by NASA's Lunar Reconnaissance Orbiter of the Shackleton Crater at the moon's south pole suggest that ice may lie in the reflective substance lining the crater's floor.
Minerals and Metals in Surface Rocks
Similarities between Mercury's surface and the moon's extend even to surface composition. Both crusts contain large amounts of silicon and oxygen, together forming mineral silicates. Mercury's composition, in fact, may be 30 percent silicates. Like the moon, Mercury has a reflective surface; on the moon, this quality is traced to the presence of elements like aluminum and titanium. Mercury's crust also contains metals, including aluminum, though here enters one difference: Much of Mercury's metal exists in its dense iron core.
- National Aeronautics and Space Administration: Solar System Explation: Mercury: Overview
- National Aeronautics and Space Administration: Solar System Explation: Earth's Moon: Overview
- ThePlanets.org: Mercury
- Universe Today: A Volcanic View of Mercury
- Space.com: Rare Volcanoes Discovered on Far Side of the Moon
- National Aeronautics and Space Administration: Messenger Finds New Evidence for Water Ice at Mercury's Poles
- Space.com: Huge Moon Crater's Water Ice Supply Revealed
- University of Tennessee, Knoxville: Surface Properties of the Moon
- Universe Today: Composition of Mercury
- Phys.org: Characterizing the Surface Composition of Mercury
- Stockbyte/Stockbyte/Getty Images | 0.831429 | 3.932776 |
Nova, “new star”; supernova, a “super” nova; hypernova, a super-duper, or super super, nova!
This word appeared in the astronomical literature at least as early as 1982, and refers to a kind of core-collapse supernova far brighter (>100 times) than usual; its meaning has changed somewhat, and today generally refers to the core collapse of particularly massive stars (>100 sols), whether or not they are spectacularly brighter than other core-collapse supernovae (though they are that too).
Most times you’ll come across hypernovae in material on gamma ray bursts (GRBs), many of which seem to involve emission of electromagnetic radiation with total energy many times that from ordinary supernovae (whether core collapse or Type Ia). Long-duration GRBs have jets, presumably from the poles of the temporary accretion disk which forms around the new black hole at the heart of the collapsed core of the progenitor (short-duration GRBs, which also produce jets, are thought to be the merger of two neutron stars, or a neutron star and a stellar-mass black hole), but even when viewed side-on (i.e. not looking into one of the jets), these GRBs are intrinsically much brighter than other core collapse supernovae.
If a supernova were to occur a few hundred light-years from us, we’d certainly notice it, and there might be some impact on our atmosphere; if there was a hypernova the same distance away, we’d suffer (not only from the increased incidence of cancer due to the far greater intensity of cosmic rays, but also from changes in weather and climate, and damage to ecosystems); if the jet were aimed directly at us, we’d be toast (while those on the other side of the world would survive the few seconds-long blast, they’d die from the consequences).
Fortunately, it seems there are no stars likely to go hypernova on us … at least not within a few tens of thousands of light-years. Whew!
Have I whet your appetite for more? Check these sites out! Brighter than an Exploding Star, It’s a Hypernova! (NASA’s Imagine the Universe), Face on Beauty (Phil Plait), and Hypernova (Swinburne University).
Like everyone else, Universe Today writers love a good story about explosions … so there are quite a few on hypernovae! Some examples: Gamma Ray Bursts and Hypernovae Linked, ESO Watches Burst Afterglow for Five Weeks, and Carbon/Oxygen Stars Could Explode as Gamma Ray Bursts.
No surprise that Astronomy Cast episode Gamma-Ray Bursts features hypermovae! Back in 2007, after attending the American Astronomical Society meeting, Pamela learning something new about hypernovae; what? Well, check out the episode, What We Learned from the American Astronomical Society and find out for yourself! | 0.858762 | 3.956769 |
Messier 71 (M71) is a globular cluster located in the small northern constellation Sagitta, the Arrow.
The cluster lies at an approximate distance of 13,000 light years from Earth and has an apparent magnitude of 6.1. It has the designation NGC 6838 in the New General Catalogue.
Messier 71 is one of the smallest globular clusters known. It occupies an area of 7.2 arc minutes of apparent sky, which corresponds to a spatial diameter of 27 light years.
M71 is located within the Summer Triangle asterism, formed by the bright stars Deneb, Altair and Vega. It lies just into the triangle going from Altair, halfway between Gamma Sagittae (magnitude 3.5) and Delta Sagittae (3.7), two stars that form part of the Arrow asterism. M71 can be found 2 degrees to the southwest of Gamma Sagittae.
The cluster appears as a hazy patch of light in binoculars. Small telescopes begin to hint at resolution, but to resolve the cluster into stars, one needs at least a medium-sized telescope. The best time of year to observe M71 is during the summer.
Messier 71 is about 13,200 times more luminous than the Sun and has about 17 percent of the Sun’s heavy elements (or metals), which is quite a lot for a globular cluster. Stars in globular clusters are generally very old and very metal-poor. For this reason, astronomers debated whether M71 was a globular or an open cluster for centuries.
The diameter of M71 may extend to about 90 light years, but the stars that are further away from the centre and more diffuse are not confirmed members of the cluster.
The cluster has a mass of about 17,000 solar masses. It contains at least 20,000 stars, but lacks RR Lyrae-type variables, which are commonly found in globulars. This is explained by the relative youth of M71. The cluster has an estimated age of 9 to 10 billion years, which also explains its abundance of metals.
Messier 71 is home to the irregular variable star Z Sagittae, a red giant star with the spectral classification of M6IIIe that shows variations from magnitude 13.5 to 15.7 over a period of 190.8 days. Z Sagittae is one of the six known M-type giant stars in M71.
Until the 1970s, M71 was believed to be a densely populated open cluster, much like Messier 11 (Wild Duck Cluster), and classified as such. In 1943, James Cuffey of Kirkwood Observatory in Bloomington, Indiana, found that it was more like a loosely populated globular cluster, one like Messier 68. However, further studies in 1959 once again pegged M71 as an open cluster.
Today, M71 is classified as a very loosely concentrated globular cluster, with a density classification of X or XI.
Messier 71 was discovered by the Swiss astronomer Jean-Philippe Loys de Chéseaux in 1746. German astronomer Johann Gottfried Koehler discovered the cluster independently between 1772 and 1779. He described the object as a “very pale nebula in the Arrow [Sagitta] at 1deg 50′ [Aqr] [301d 50′] and 39d northern latitude.”
Charles Messier’s friend and colleague Pierre Méchain discovered the cluster on June 28, 1780. Messier added it to his catalogue as a nebula without stars based on his own observations on October 4, 1780. He noted:
Nebula discovered by M. Méchain on June 28, 1780, between the stars Gamma and Delta Sagittae. On October 4 following, M. Messier looked for it: its light is very faint & it contains no star; the least light makes it disappear. It is situated about 4 degrees below [south of] that which M. Messier discovered in Vulpecula. See No. 27 [Dumbbell Nebula, Messier 27]. He reported it on the Chart of the Comet of 1779.” (diam 3.5′)
William Herschel was the first to resolve individual stars in the cluster in 1783. He later observed M71 in his 20-foot telescope and noted, “It is situated in the milky way, and the stars are probably in the extent of it; it is however considerably condensed; about 3 minutes in diameter.”
John Herschel catalogued the cluster as h 2056 and later added it to the General Catalogue as GC 4520. He described it as a “cluster; very large; very rich; pretty much compressed; stars from 11th to 14th magnitude.”
Admiral William Henry Smyth observed the cluster in July 1836 and offered the following description:
A rich compressed Milky-Way cluster on the shaft of the arrow, and 10deg north-a quarter-east from Altair. It was discovered by Mechain in 1781, and described by Messier as a nebula unaccompanied by stars, and of a very feeble light. Piazzi seems to have observed it meridionally as a star of the 8th magnitude, by admitting the light of a lamp upon it (312 P. xix), but his darkened field ought to have shown that it is flanked with four telescopic stars, besides other larger companions in view. It was first resolved into stars by Sir William Herschel, in 1783, who esteemed its profundity to be of the 243rd order.
|Designations: Messier 71, M71, NGC 6838, Collinder 409, GCl 115, C 1951+186, CSI+18-19515, GCRV 12241, MWSC 3200|
|Right ascension: 19h 53m 46.49s|
|Distance: 13,000 light years (4,000 parsecs)|
|Age: 9 to 10 billion years|
|Number of stars: >20,000|
|Apparent magnitude: +6.1|
|Apparent dimensions: 7′.2|
|Radius: 13 light years| | 0.83164 | 3.950847 |
Radar scans of the red planet suggest that a stable reservoir of salty, liquid water measuring some 12 miles across lies nearly a mile beneath the planet’s south pole. What’s more, the underground lake is not likely to be alone.
“There are other areas that seem to be similar. There’s no reason to say this is the only one,” says Elena Pettinelli of Italy’s Roma Tre University, a coauthor of the paper reporting the discovery today in the journal Science.
If confirmed, the buried pocket of water could answer a few questions about where Mars’s ancient oceans went, as well as provide a resource for future human settlements. Even more thrilling for astrobiologists, such a feature may be an ideal habitat for extraterrestrial life-forms.
“In this kind of environment that we know of on Earth, in the Antarctic, we have bacteria,” Pettinelli says. “They can be deep in the ice.”
“Mars will come to fear my botany powers.”
Billions of years ago, Mars was likely warm and covered in seas like its larger, bluer neighbor. But the Mars of today is a parched, toxic desert, and for decades, scientists have been trying to decipher what happened to the water that once soaked, sloshed, and tumbled over its sands.
To date, scientists have found water on Mars multiple times, but it’s usually quite transient or inaccessible, either hovering in the atmosphere, locked into permafrost or polar caps, or perhaps seasonally seeping down crater slopes. And the amount we’ve found doesn’t quite fill those ancient Martian seas or make crop-growing particularly easy.
“We know there was a lot of water on Mars’s surface, and we can’t quite account for all of it today,” says Bobby Braun of the University of Colorado, Boulder. So, scientists hypothesized that some of the missing water could be trapped in subsurface aquifers containing vast stores of liquid.
“I'm going to have to science the s--t out of this.”
However, humans didn’t launch spacecraft capable of sniffing out buried water until earlier this millennium.
One of them, the European Space Agency’s Mars Express spacecraft, has been orbiting the fourth rock from the sun since 2003; riding on board is an instrument called MARSIS, which uses radar pulses to see into the Martian subsurface. It works by sending low-frequency radio waves into the planet, which burrow beneath the ground until they bounce off geologic structures and boundaries. By studying how those waves are reflected back to the spacecraft, scientists can infer what might lie beneath.
In 2008, the MARSIS team saw glimmers of what could be some very bright reflections near the planet’s south pole, in an area where frozen ice sheets are stacked atop one another. On Earth, the brightest radar reflectors are pools of briny water—and so the team decided to take a closer look at the region.
From its blood-like hue to its potential to sustain life, Mars has intrigued humankind for thousands of years. Learn how the red planet formed from gas and dust and what its polar ice caps mean for life as we know it.
After a few years of gathering data that weren’t exactly useful, the team finally began collecting enough observations in 2012 to assemble a bigger picture. From there, it took another three years and 29 spacecraft passes before scientists had enough information to work with.
“We knew that there was something there, and we were curious to know what was under that area,” Pettinelli recalls. “And we were stubborn enough to do the data analysis.”
Sorting through the MARSIS data wasn’t easy. Over the next two years, the team compiled and processed the observations and worked very hard to rule out alternate possibilities, such as deeper layers of carbon dioxide ice.
Eventually, by comparing the reflectance patterns on Mars with those seen on Earth, scientists were convinced that they’d found a subglacial lake. Perhaps several feet deep, the lake contains various salts that help keep it liquid at extremely cold temperatures, the team speculates.
“This is space. It does not cooperate.”
The Mars Express team compares the discovery to lakes tucked beneath the ice sheets of Greenland and Antarctica, which are sometimes huge and certainly more than capable of hosting life as we know it.
But not everyone is convinced that the “lake” is actually a lake. Even according to the team, it could instead be a deposit of dampened sludge, more like muddy sediments than a pocket filled with liquid. Determining the exact nature of the structure will require a different instrument, Pettinelli says.
“We can’t choose between one or the other. We don’t have enough information to say this is a lake or saturated sediment like an aquifer,” Pettinelli says. “The lake will be more interesting.”
There is another ground-penetrating radar orbiting Mars right now, and it adds an interesting twist.
“We do not see this reflector,” says Bruce Campbell of Smithsonian’s National Air and Space Museum, who is a member of the team operating an instrument called SHARAD on NASA’s Mars Reconnaissance Orbiter.
MRO has orbited Mars since 2006, sweeping its radar over vast swaths of alien landscape, including many passes over the south pole’s layered deposits, and it hasn’t turned up anything resembling a reservoir.
Dark basins and bright polar caps are among the most distinctive features on Mars.
PHOTOGRAPH BY NASA, JPL, USGS
This is likely because MRO’s radar uses different wavelengths that are scattered by the polar ice before they reach the potential reservoir’s depth, says Jack Holt of the University of Arizona. But anything as reflective as a liquid lake should be identifiable by SHARAD, he notes.
“A brine is probably the strongest radar reflector you can come up with, aside from metal,” he says. “A lake would mean a smooth, mirror-like reflection that is more likely to show up in SHARAD [but] if it’s saturated sediments, it could be a rougher surface and therefore easier to miss with SHARAD.”
In all, scientists are eager to confirm the finding—including those on the MARSIS team.
“I think, we’ve done a good job in trying to kill this idea, in the sense that we have been trying to destroy the possibility that it was water many times,” Pettinelli says. “So we are quite convinced now, and we hope to be more convinced in the future with other data.”
“The good thing is, I know the recipe: You take hydrogen, you add oxygen, and you burn.”
Assuming it’s there, this little pocket of saltwater may help solve the mystery of Mars’s missing oceans. It’s also a clue about the planet’s hydrological cycle, which is theorized to involve buried aquifers charged by melting polar ice caps, with the bulk of the water running north from the southern highlands, says Nathalie Cabrol of the SETI Institute.
“You can intuit that there would be either very damp sediments at the poles of Mars, or a lens of liquid water,” she says. “This is where you expect this reservoir to be.”
No stranger to water in weird places, Cabrol’s work on Earth includes investigating Mars analog environments, which sometimes requires diving into lakes tucked among the peaks of the high Andes. Whether the MARSIS find is soggy sediments or an actual lake, she says it’s thrilling.
“What you see here is potentially the presence of water, of shelter ... and you’re going to produce nutrients out of the minerals,” she says. “What you need is a source of energy … and if there were recent volcanoes in the polar regions, then this is definitely a place that would become a high habitability and life target.”
On the other hand, she notes, “it would be a very problematic place to go, because it would be under the special regions for planetary protection,” she says, referring to the UN regulations aimed at preventing interplanetary contamination of habitable environments.
The new reservoir is also the kind of resource that humans interested in settling on Mars might want to take advantage of—though perhaps not right away.
“I think it’s very unlikely the first humans on Mars are going to drill down to several kilometers,” says Braun, an advisor for National Geographic’s MARS series and NASA’s former chief technologist.
“But I think it’s probably true that if this is a lake, there are other bodies of water like it that are perhaps closer to the surface,” he says, “and if we knew that there was a big body of water at tens of meters down, that would be something you’d certainly want to know about when you’re planning a base camp.”
Lead Image: An orbital view shows the south polar cap on Mars, where scientists using radar may have found a buried watery reservoir.
PHOTOGRAPH BY SCIENCE HISTORY IMAGES, ALAMY STOCK PHOTO | 0.801863 | 3.738439 |
Atoms are composed of a massive, central nucleus surrounded by a swarm of fast-moving electrons. The nucleus is made up of protons and, in most cases, neutrons. Almost all of the mass (more than 99%) of an atom is contained in the dense nucleus.
An atomic nucleus is much, much smaller than an atom. The cloud of electrons that "orbit" the nucleus and define the "size" of an atom is roughly 100,000 times as large as that atom's nucleus! For example, a helium atom has a size of about 1 Ångström (0.1 nanometers or 10-10 meters), while its nucleus is only 1 femtometer (10-15 meters) in diameter. If you made a scale model of an atom with a nucleus the size of a pea, the electrons would zing around in a space larger than a major sports stadium! An atom is mostly empty space.
The number of protons in the nucleus determines what type of element the atom is. The number of protons is called the element's "atomic number". For example, hydrogen has an atomic number of one, since all hydrogen atoms have one proton in their nucleus. Carbon has 6 protons, so its atomic number is 6; oxygen has 8 protons, so its atomic number is 8. Uranium has 92 protons, so its atomic number is 92! If we count the number of protons plus neutrons, we get an atom's atomic mass. Most elements come in different versions, called "isotopes", with different numbers of neutrons. For example, the most common form of carbon is carbon-12 (12C); that isotope of carbon has 6 protons and 6 neutrons, and thus an atomic mass of twelve. Another isotope of carbon, carbon-14 (12C), has 6 protons and 8 neutrons, hence and atomic mass of fourteen. 12C is radioactive and is used to determine how old things are in a technique called "carbon dating".
Sometimes the electrons get stripped away from an atom. If an atom loses all of its electrons, leaving behind a "naked" atomic nucleus, the nucleus is called an ion. Ions moving at high speeds make up one type of particle radiation. These ions are usually made from relatively small nuclei, like the nucleus of a hydrogen atom (a single proton) or a helium atom (two neutrons and two protons). They can be much larger, though; some cosmic rays are very heavy ions from more massive atoms. | 0.826847 | 3.856751 |
Fourteen years ago, a 25 year old version of myself stumbled across a faint new comet in the constellation of Aquarius. Circling the Sun every ~7 years, the comet is intrinsically faint and could be rightly considered a runt. This year the comet was perfectly placed with perihelion and opposition occurring within days of each other (perihelion on October 1). As a result this comet which only comes within 1.41 AU of the Sun is also passing within 0.42 AU of Earth. Based on its previous behavior it should have only brightened to 14-15th magnitude which is nothing special. Surprisingly it has experienced a series of outbursts and is now bright enough to be seen in small telescopes or even binoculars at magnitude 9.2 to 9.8.
I’m probably one of the last people to write about the outburst of comet 168P/Hergenrother which is surprising since it’s one of my finds. It was discovered on images taken with the Catalina Schmidt (then a 0.41-m) telescope during the course of the Catalina Sky Survey (CSS). It was the 2nd of my four comet discoveries and my first CCD find [my first comet, C/1996 R1 (Hergenrother-Spahr) was found with photographic film]. Though I was the first to spot the comet the actual images were taken by either me, John Brownlee and/or Tim Spahr. Discovery images can be seen to the right. It’s not much to look at and the bad column sure didn’t help.
At that time, the CSS had just finished upgrading the Schmidt from a photographic instrument to a digital CCD equipped instrument. We still had a ways to go and didn’t even have automatic detection software yet. Instead we would take 3 images spaced about 10-15 minutes apart and difference (subtract one image from another after lining them up relative to field stars) 2 of the images. Objects that didn’t move such as stars would mostly disappear leaving a positive and negative spot for moving objects. We would then blink all three of the original images to make sure our suspects were real objects. It was highly inefficient but resulted in a few new near-Earth asteroid and comet discoveries before the automated detection system was available.
The 2012 return started routinely wit the comet brightening up to its expected 15th magnitude. The first sign of outburst activity was reported by J. J. Gonzalez (Spain) who visually sighted 168P at magnitude 11.2 on September 6. A second outburst must have occurred around the start of October. By October 3rd, observers such as Michael Mattiazzo (Australia) were reporting the comet at magnitude 9.8. Over the last few weeks brightness estimates have ranged between 9.2 and 10.0.
My own estimates are given below:
Oct. 11.10, 9.2, 6′ (C. W. Hergenrother, Tucson, Arizona, 30×125 binoculars);
Oct. 09.13, 9.6, 6′ (C. W. Hergenrother, Tucson, Arizona, 30×125 binoculars);
Oct. 08.19, 9.3, 3′ (C. W. Hergenrother, Tucson, Arizona, 30×125 binoculars);
Oct. 04.10, 9.8, 1.5′ (C. W. Hergenrother, Tucson, Arizona, 30×125 binoculars);
Oct. 04.10, 9.9, 2′ (C. W. Hergenrother, Tucson, Arizona, 0.31-m reflector).
The comet was easy in 30×125 binoculars from my backyard (LM = +5.7-6.0). Though the comet was visible in 10×50 binoculars it was hard to make an accurate brightness estimate due to the dense star field. My yard is fairly dark for a suburban site. If you live under brighter skies a larger telescope will be required to see the comet.
Since the start of its outbursts, the comet has looked relatively normal in CCD images with no sign of jets or secondary nuclei. Yesterday, Gianluca Masi (Italy) emailed me with images showing a ‘cloud’ of material tailward of the nucleus. Luckily I was scheduled on the University of Arizona’s Kuiper 1.5-m telescope and was able to confirm Gianluca’s observation. The image below shows the “cloud” trailing the nucleus in the anti-solar direction.
So what’s happening? Luckily we saw something similar back in 2006 when comet 73P/Schwassmann-Wachmann 3 made a close approach to Earth. SW3 had undergone a splitting event back in 1995 which produced two major components (the original nucleus and a smaller secondary one). The smaller component (called 73P-B) was still experiencing outbursts and shedding material in 2006. From time to time, “clouds” of material would appear to drift back from the nucleus. High-resolution images showed this “cloud” to be composed of hundreds of small mini-comets, many probably no larger than a meter in size. As these mini-comets disintegrated they would produce short-lived mini-comae that lasted for only a day or so.
Only a few weeks later the Hubble Space Telescope and ground-based telescopes such as the Vatican 1.8-m were able to resolve 73P-B’s “clouds” into a group of hundreds of mini-comets. More images of 73P-B taken with the SAO 1.2-m, Kuiper 1.5-m and VATT 1.8-m can be found here.
Could the same thing be happening with 168P? Possibly. Right now we aren’t sure what is exactly going on with 168P. The fact that the comet is experiencing outbursts means it is releasing a large amount of dust. It is very possible that it has also released a number of meter sized boulders. These boulders may be releasing dust causing the “cloud” visible trailing the main nucleus. Perhaps larger telescopes will provide better images over the coming weeks.
In the meantime, the comet is still visible to small telescope users as it moves northward from Pegasus to Andromeda. A finder chart can be found at Comet Chasing.
I can’t lie that I’ve had been waiting for this apparition of 168P and hoping it would become bright enough to be seen visually. As both an amateur and professional astronomer I still get a thrill seeing a comet with my own eyes. Having it be one of mine makes it even better. (Of my four discoveries, this is the 2nd I’ve been able to see visually. C/1996 R1 was 10th magnitude at discovery.) I look forward to seeing what other surprises 168P throws our way.
Good job, little 168P! | 0.831577 | 3.752601 |
Water. It’s always about the water when it comes to sizing up a planet’s potential to support life. Mars may possess some liquid water in the form of occasional salty flows down crater walls, but most appears to be locked up in polar ice or hidden deep underground. Set a cup of the stuff out on a sunny Martian day today and depending on conditions, it could quickly freeze or simply bubble away to vapor in the planet’s ultra-thin atmosphere.
Evidence of abundant liquid water in former flooded plains and sinuous river beds can be found nearly everywhere on Mars. NASA’s Curiosity rover has found mineral deposits that only form in liquid water and pebbles rounded by an ancient stream that once burbled across the floor of Gale Crater. And therein lies the paradox. Water appears to have gushed willy-nilly across the Red Planet 3 to 4 billion years ago, so what’s up today?
Blame Mars’ wimpy atmosphere. Thicker, juicier air and the increase in atmospheric pressure that comes with it would keep the water in that cup stable. A thicker atmosphere would also seal in the heat, helping to keep the planet warm enough for liquid water to pool and flow.
Different ideas have been proposed to explain the putative thinning of the air including the loss of the planet’s magnetic field, which serves as a defense against the solar wind.
Convection currents within its molten nickel-iron core likely generated Mars’ original magnetic defenses. But sometime early in the planet’s history the currents stopped either because the core cooled or was disrupted by asteroid impacts. Without a churning core, the magnetic field withered, allowing the solar wind to strip away the atmosphere, molecule by molecule.
Solar wind eats away the Martian atmosphere
Measurements from NASA’s current MAVEN mission indicate that the solar wind strips away gas at a rate of about 100 grams (equivalent to roughly 1/4 pound) every second. “Like the theft of a few coins from a cash register every day, the loss becomes significant over time,” said Bruce Jakosky, MAVEN principal investigator.
Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) suggest a different, less cut-and-dried scenario. Based on their studies, early Mars may have been warmed now and again by a powerful greenhouse effect. In a paper published in Geophysical Research Letters, researchers found that interactions between methane, carbon dioxide and hydrogen in the early Martian atmosphere may have created warm periods when the planet could support liquid water on its surface.
The team first considered the effects of CO2, an obvious choice since it comprises 95% of Mars’ present day atmosphere and famously traps heat. But when you take into account that the Sun shone 30% fainter 4 billion years ago compared to today, CO2 alone couldn’t cut it.
“You can do climate calculations where you add CO2 and build up to hundreds of times the present day atmospheric pressure on Mars, and you still never get to temperatures that are even close to the melting point,” said Robin Wordsworth, assistant professor of environmental science and engineering at SEAS, and first author of the paper.
Carbon dioxide isn’t the only gas capable of preventing heat from escaping into space. Methane or CH4 will do the job, too. Billions of years ago, when the planet was more geologically active, volcanoes could have tapped into deep sources of methane and released bursts of the gas into the Martian atmosphere. Similar to what happens on Saturn’s moon Titan, solar ultraviolet light would snap the molecule in two, liberating hydrogen gas in the process.
When Wordsworth and his team looked at what happens when methane, hydrogen and carbon dioxide collide and then interact with sunlight, they discovered that the combination strongly absorbed heat.
Carl Sagan, American astronomer and astronomy popularizer, first speculated that hydrogen warming could have been important on early Mars back in 1977, but this is the first time scientists have been able to calculate its greenhouse effect accurately. It is also the first time that methane has been shown to be an effective greenhouse gas on early Mars.
When you take methane into consideration, Mars may have had episodes of warmth based on geological activity associated with earthquakes and volcanoes. There have been at least three volcanic epochs during the planet’s history — 3.5 billion years ago (evidenced by lunar mare-like plains), 3 billion years ago (smaller shield volcanoes) and 1 to 2 billion years ago, when giant shield volcanoes such as Olympus Mons were active. So we have three potential methane bursts that could rejigger the atmosphere to allow for a mellower Mars.
The sheer size of Olympus Mons practically shouts massive eruptions over a long period of time. During the in-between times, hydrogen, a lightweight gas, would have continued to escape into space until replenished by the next geological upheaval.
“This research shows that the warming effects of both methane and hydrogen have been underestimated by a significant amount,” said Wordsworth. “We discovered that methane and hydrogen, and their interaction with carbon dioxide, were much better at warming early Mars than had previously been believed.”
” … maybe we’re on Mars because of the magnificent science that can be done there — the gates of the wonder world are opening in our time. Maybe we’re on Mars because we have to be, because there’s a deep nomadic impulse built into us by the evolutionary process, we come after all, from hunter gatherers, and for 99.9% of our tenure on Earth we’ve been wanderers. And, the next place to wander to, is Mars. But whatever the reason you’re on Mars is, I’m glad you’re there. And I wish I was with you.” | 0.823266 | 4.008739 |
Start studying Astronomy Ch Visual Activity: Phases of Venus. Learn vocabulary, terms, and When would a new Venus be highest in the sky? - at noon. Imagine that Venus is in its full phase today. If we could see it, at what time would the full Venus be highest in the sky? noon. When would a new Venus be. In Ptolemy's Earth-centered model for the solar system, Venus's phase is never full as viewed from Earth When would a new Venus be highest in the sky?.
which of the following statements about copernican model for the solar system is false?
Cards marked as Correct will not be shown again until you hit Shuffle or Start Over. Click Card to .. When would a new Venus be highest in the sky? at noon. Part C When would a new Venus be highest in the sky? Hint 1. Where is Venus in its new phase? Venus's phase is new as viewed from Earth when ______. Part B Imagine that Venus is in its full phase today. If we could see it, at what time would the full Venus be highest in the sky? At Noon Venus's phase is new as.
The planet is often visible in the sky, yet its brightness varies. When Venus's orbit is on the far side of the sun, you can see most of the surface that is . As the new moon gradually becomes full, you can observe it gradually grow lighter. The bright planet Venus can be easily seen from Earth, and in Weather permitting, Venus is the first planet night sky observers can spot, and it is . 1, Greatest Eastern Elongation: Venus passed that point in the sky 17 Venus is emerging as a new morning “star” rising in the east-southeast at mid-dawn. Greatest brilliancy for Venus is a delicate balance between how much we see of its day side, and the At that time, it will leave the evening sky to enter the morning sky. At inferior conjunction, Venus is at the new phase.
Phases of Venus: AST — Prof Steven Finkelstein visible close to the Sun in our sky. To the right is a 5) When would a new Venus be highest in the sky?. Hence, the maximum Venus can get from the Sun (either in the morning sky or the Jagadheep built a new receiver for the Arecibo radio telescope that works. Venus will soon pass in front of the Sun at inferior solar conjunction. From Mountain 27 Mar , – Venus reaches highest point in evening sky. 13 Aug
which statement correctly describes the way in which the surface of venus is renewed
As it does this, Venus gets bigger and brighter and the planet's illumination angle changes. can witness the telescopic phases of this planet in the early evening sky. . The Venus / Earth connection at a higher turn of the spiral is symbolic of the A New Venus, like a New Moon, can only be seen when its orbit passes. Late this month, Venus will reach its greatest elongation, meaning Constant confusion: New studies deepen mystery of universe's expansion. The orders of the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Venus is farther away from the sun and can be seen higher in the sky at night. The planet's large apparent diameter also means that the crescent can be On November 30th Venus attains its greatest brilliancy for this apparition at . Star map of Scorpius, showing the five stars formally assigned new names by the IAU. Venus can sometimes be seen in broad daylight with the Sun in the sky if you know Venus reaches greatest eastern elongation (highest in the evening sky) on. You can either choose a filter (I like red) or plan your observations in early twilight minutes after sundown when Venus is both highest in the sky. Venus orbits the Sun faster than the Earth so it will either appear in the sky The highest point occurs at the summer solstice, while the lowest. The phases of Venus are the variations of lighting seen on the planet's surface, similar to lunar Since the planet has an atmosphere it can be seen at new in a telescope by the halo of light refracted around the planet. Venus reaches its greatest magnitude of − when it is an intermediate crescent Sky & Telescope. This sky map shows the location of the Venus and the moon in the late daytime sky Venus is now the most dazzling that it will be for all of and in on Thursday but is just 4 percent illuminated on New Year's Day. In Ptolemy's Earth-centered model for the solar system (not shown), Venus's phase is never full as viewed When would a new Venus be highest in the sky?. | 0.880317 | 3.588614 |
Birthday boy Édouard Jean-Marie Stephan was born on August 31st, 1837, in Sainte Pezenne, a commune on the outskirts of the town of Niort, in the Deux-Sèvres department of France. Stephan discovered two asteroids, 89 Julia and 91 Aegina, both of which have been featured in these pages. But it was on the deep sky that he focused much of his attention, discovering more new nebulae than most, and the now famous (as groups of galaxies go) Stephan’s Quintet.
His work did not go unnoticed, and in 1884 he was awarded the Prix Valz by the French Academy of Sciences. A report on the award in the American journal Scientific News described him as “a savant whose discovery of seven hundred nebulae does honor to French astronomy”.
Stephan would have been in good company at the awards ceremony (I have no idea whether they had one or not), as that year’s physics prize went to the great Henri Becquerel, co-discoverer of radioactivity.
Edward Mills Purcell, born August 30th 1912 (died March 7th 1997) was supervisor of the Harvard team responsible for detecting the elusive 21 cm line of neutral galactic hydrogen.
They achieved this by using a home-made horn antenna, built at a cost of just $500, and installed outside the Lyman Lab at Harvard.
Discovery of the 21cm line was important because it allowed radio astronomers to peer through the Earth’s atmosphere with minimal interference and calculate the rotation curve of the galactic spiral arms.
ALSO TODAY . . .
1984 – First flight (mission STS-41-D) of the space shuttle Discovery.
1880 – Asteroid 217 Eudora discovered by Jérôme Eugène Coggia.
1974 – The Astronomical Netherlands Satellite (Astronomische Nederlandse Satelliet) was launched.
74 Galatea (discovered August 29th, 1862) was the third of five asteroids to be discovered by the German astronomer Ernst Wilhelm Leberecht Tempel(comets were more his thing – he found an impressive 21!).
Galatea is a large, dark, C-type main belt asteroid, and if it seems as though every asteroid I mention fits that description it’s because 75% of all known asteroids are C-types, and the main belt contains 93% of all the numbered minor planets.
Two possibilities exist for the choice of the name Galatea. Ovid tells us on the one hand that it was the name of the ivory statue carved by the sculptor Pygmalion, with which he fell in love. But on the other hand he also uses the name to describe a nereid (sea nymph) whose lover, the river spirit Acis was killed by a boulder thrown by Galatea’s jealous suitor, Polyphemus the cyclops. Ovid omits to discuss what kind of aim a cyclops would have.
Enceladus was discovered on this day in 1789by William Herschel. This 500km diameter moon of Saturn has been proven recently to have the most impresive volcanoes in the Solar System. They are cryovolcanoes, so what comes out is cold (in this case water), and study of them has shown that they have been able to project water as far as Saturn itself, as well as providing enough ice to make up the parent planet’s “E ring”.
Enkelados was one of the Gigantes, children of Uranus and Gaia. This particular one, for his sins, was wounded in battle by Athene and buried under Mount Etna. Being buried under a volcano was a common fate for the assorted monsters and giants defeated by the Olympian gods. I suppose it was a handy method for explaining away subterranean rumblings.
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ALSO TODAY . . . .
Asteroid 167 Urdadiscovered in 1876 by Christian H F Peters. George Eric Deacon Alcock MBE was born in Peterborough, 1912.
Asteroid 240 Vanadis was discovered by the French astronomer Alphonse Borelly on August 27th 1884. It is a “C” type asteroid in the main belt, about 94km in diameter, with a day lasting just over 10 and a half hours. It has an absolute magnitude of 9.0.
Vanadis is another name for Freyja, a Norse goddess associated with fertility, love and beauty. Like a lot of Norse deities, she’s a bit quirkier than your average Greek or Roman goddess. Her peculiarities include always having a boar at her side, and driving a chariot pulled by cats. It is from Freyja that those of us who use partly or wholly Germanic languages derive the name Friday. Her alternative name, Vanadis , means something along the lines of “spirit of the Vanir” (a group of deities associated with nature and fertility).
ALSO TODAY . . . .
1962 – launch of the first successful probe to Venus,Mariner 2.
August 26th 1981 was the date on which Voyager 2made its closest approach to Saturn (at 01:21 UT). Voyager 1 had already been and gone 9 months previously, despite being launched second, and between them the Voyager twins greatly increased our knowledge of the most beautiful of all the planets. They found, among other things, that (i) the atmosphere is nearly all hydrogen and helium (Saturn would float in water if an appropriately-sized bath could be constructed); (ii) it is a very cold place (-200 to -300°F); (iii) it’s also a bit blowy (wind speeds recorded over 1,100 mph), and (iv) it rotates every 10 hours 39 minutes and 24 seconds.
It’s hard to say exactly where Voyager 2 is at the moment, because I’m typing this several days before I post it, and a Voyager can get about 30 miles further away in the time it takes me to type the word “miles”. If you want to know, then your best bet is to go to the JPL Voyager Mission Status web page. For now, I’ll round it up to something that only changes very rarely: 121 AU (1 Astronomical Unit is about 93 million miles, so it’s a safe figure for a few weeks).
Today in 2003, Cupid and Mab, moons of Uranus, both of which had been too dim to see on Voyager photographs, were discovered by Mark R Showalter and Jack J Lissauer using the Hubble Space Telescope. Cupid was named after the character in William Shakespeare’s rarely performed and possibly incomplete play Timon of Athens, and Mab after the queen of the fairies who is mentioned in Romeo and Juliet (and as a long-time fan I would also refer you to The Fairy Feller’s Master Stroke on the album Queen II). Mab has unusual hobbies. She drives her chariot (which I believe is made from an acorn) up people’s noses to enable her to influence their dreams, and she is thought to decide who gets infected by herpes simplex.
Neither Cupid nor Mab could be described as impressive bodies. Cupid measures about 18 km in diameter, while Mab is thought to be about 24 km.
Also today, asteroid 84 Klio was discovered by R Luther in 1865. Clio (or Klio or Kleio) was the muse of history. A daughter of Zeus and Mnemosyne, she had one son, to whom she gave the butchly masculine name Hyacinth. Her own name is derived from the verb kleô, meaning to celebrate or make famous.
1889 – Asteroid 287 Nephthys discovered by C F H Peters, and is the last of his incredible haul of 48 asteroids. Nephthys is a large, S-type main belt asteroid, and for a change is named after a character from Egyptian mythology, the daughter of Nut and Geb, and sister of Isis.
I’m going to have to do some digging on Peters, because I find it hard to believe that after 28 years of tracking the things, he doesn’t have an asteroid named after him. I’ve found two so far named after people called Peters, and he isn’t either of them.
Finally today,Voyager 2 made its closest approach to Neptune on August 25th, 1989. This was the end of a bit of a purple patch for NASA. Photographs from the outer planets had enthralled the inhabitants of this one for more than a decade, and Neptune didn’t disappoint. Voyager 2 was able to get some great shots of the planet, including the “Great Dark Spot” which seems to have subsequently vanished. There was also time for a visit to Triton, Neptune’s volcanically active largest moon, thought to be a captured Kuiper Belt object.
Although they didn’t know it at the time, this fly-by marked the point at which every planet in the solar system had been visited (back in the day they still had Pluto on the list, but it would eventually be removed).
The large, dark, C-type main-belt asteroid93 Minerva was discovered today in 1867 by the American-Canadian astronomer James Craig Watson. Minerva was the second of his 22 asteroids. Several occultations of stars by Minerva have been observed since discovery to give an estimated diameter of 150 km. It has recently become apparent that Minerva is in fact a trinary asteroid, with two tiny moons (just 3 and 4km across).
Minerva was the Roman equivalent of Athena, a goddess primarily associated with wisdom, although she did have several other attributes on her curriculum vitae (or resumé if you insist) including music, poetry and magic.
The moons of Minerva have been given names associated with their parent. S/(93)1 is now known as Aegis, after the animal skin worn by Athena, while S/(93)2 Gorgoneion refers to a protective amulet (of the Gorgon’s head) worn by certain deities.
Today’s second picture is the shrine to Minerva at Handbridge in Chester. You can’t see a great deal of detail, and the surrounding stonework is nineteenth century, but it is “Grade I” listed and the only one of its kind in situ in western Europe, so it deserves a mention.
Main belt asteroid 124 Alkesteis an S-type of just over 76 km diameter, discovered on August 23rd, 1872 by C H F Peters from Hamilton College in New York State. The name refers to Alcestis, daughter of the mythological Greek king Pelias, and eponymous subject ofthe play by Euripides which won second prize at the City Dionysia in 438 BC.
The name was chosen by Adelinde Weiss, wife of the Austrian astronomer Edmund Weiss.
We almost have a photograph of today’s birthday girl, although actually it’s a series of images of the star Beta Virginis, the fifth brightest star in the constellation Virgo. This star was occulted (temporarily hidden) by Alkeste on June 24th, 2003. If enough people within the area from which the occultation can be seen make images of the track of the occulted star, these can be combined to give a rough guide to the size and shape of the asteroid. The area in question was a slender 80 or so kilometre slice across New Zealand and southern Australia, but enough observations were taken on the night to give the above indication of Alkeste’s shape.
Asteroid 19 Fortuna, discovered today in 1852, is a large, dark, main-belt asteroid. In fact, it is one of the darkest large asteroids known. It was discovered by John Russell Hind, an English astronomer who was working at the private observatory of George Bishop, having previously been at Greenwich. Hind will hopefully be given the full treatment on his birthday (May 12) but for now I’ll just mention that his wife had the wonderfully Bond girl-esque name of Fanny Fuller.
Fortuna, of course, was the Roman goddess of luck. Being a goddess of fate as well though, the luck she brought couldn’t be relied upon to be of the good variety (an amulet mentioning her was found at Pompeii, for example).
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ALSO TODAY . . . .
1868 – Discovery of asteroid 102 Miriam by C H F Peters. Miriam is named after the sister of Moses. Back in the 1880s asteroids were named after mythological figures, so the choice caused a stir at the time, the inference being that she may not have been a real person.
1882 – Discovery of C-type main belt asteroid 229 Adelinda by Johann Palisa. | 0.845738 | 3.00438 |
Will the Sun go Nova one day?
I have been wondering this for quite some time, so I had decided to post this question here.
My question is will the sun go Nova one day? If so, does anyone know when it will go Nova and how many planets will it destroy or demolish in it's path? I know the sun is really big and is capable of destroying a few planets (including Earth) after it had gone Nova. Please be honest with this as much as you can since I don't like guesses, so don't guess - be honest.
- Bullet MagnetLv 41 decade agoFavorite Answer
If the sun went nova it would destroy every known planet in the Solar System.
But the sun is not massive enough to go nova. In 4-5 billion years the Hydrogen fuel in the sun's core will have all been converted to helium. The core will contract and heat up, and upon reaching 100 million degrees Celsius, Helium fusion will begin. The outer layers of the sun will expand to about Earth's orbit, becoming a red giant, but the loss of mass early in this phase will mean that Earth will probably move to a wider orbit, and not be engulfed as Mercury would be and Venus would probably be. Although the expansion cools the sun somewhat and makes it emit redder light, the heat emitted will be much higher than today, and despite being further out, Earth's oceans will boil away, and become like Venus now, until the atmosphere, too, is lost to space.
The red giant phase will be short lived, and eventually the outer layers will puff away due to thermal pulsations, forming a planetary nebula, leaving the core a tiny white dwarf that will slowly cool and dim.
There will be no nova here, but the outlook for Earth is not good. Fortunately, we'll all be extinct long before the red giant phase.
- Anonymous6 years ago
Sun can well can Nova
- Old Punk DadLv 61 decade ago
No it won't go nova, not enough mass nor is it part of a binary system. It will go into a red giant phase though, as the hydrogen is used up and it begins to fuse heavier and heavier elements. The earth will for sure be gone but it probably won't reach as far as the orbit of mars. Near the end the sun will blow off most of its mass in a series of convulsions as it nears the point of fusing elements into Iron. Fusion will stop there and all that will be left is a white dwarf that will eventually cool and go dark.
Don't worry, the Sun is only middle aged so you have a couple of billion years, at least, before you have to worry about it.
- Dennis HLv 41 decade ago
Nuclear astrophycists currently predict that the sun will continue to convert hydrogen to helium as a main sequence star for another 5 billion years or so. When it runs out of hydrogen, it will collapse and heat up until it becomes hot enough to fuse helium nuclei to form carbon. This reaction produces more energy than the H --> He reaction it is currently undergoing, so it will swell out to about the orbit of Mars. That means the eart will be orbiting INSIDE the sun!
When the sun runs out of Helium, it will collapse again, this time it will Nova, but the Earth and Mercury will already have been disintegrated by the red giant phase.
We should probably work to have an escape plan worked out before the red giant phase happens.
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- BrantLv 71 decade ago
Just a comment on some of the answers. There is a difference between a nova and a supernova. The sun will probably nova, which just means it increases dramatically in brightness because of changes in the interior processes and the balance between contraction and expansion. The sun will not supernova, though.
- Anonymous1 decade ago
The Sun will not go Nova, but it will shed of its outter shells. When this happens it will more than likely wipe out all the inner planets, it will also provide enough energy to ignite Jupiter and Saturn, so that they begin to burn like our Sun. This has always been a mystery as to why the planets Jupiter and Saturn have the ability to have made small stars, but never did.They are classified as brown dwarfs, and emit more heat than they absorb, so it still remains a mystery.
- 1 decade ago
Our sun is a main sequence star it is too small to become a super nova, eventually our sun will expand to envelope the entire solar system then it will contract to become a dwarf star and cool into a lump of ash.
- eriLv 71 decade ago
No. The Sun is not nearly massive enough to explode. It will expand into a red giant, engulfing the inner planets (possibly out as far as Mars), and then will puff out it's outer layers into space, leaving a white dwarf star behind that slowly cools.
- gabegm1Lv 41 decade ago
not likely as you need at least an equivent of about 4 or 5 solar mass to have a star to go nova. the sun is most likely to shrink and form a dwarf and perhaps finally a neutron star.
- 1 decade ago
I don't think so, the sun is mideum sized star, it will not becomes a nova but it will goes dark when it runs out of power. Other stars that larger than the sun will become Novas and Supernovas, when they run out of power, they will exploded and the rest will become blackholes. | 0.905292 | 3.337406 |
Comet Siding Spring is expected to travel exceptionally close to Mars at 126,000 mph (202,000 kph) on October 19, according to NASA, which says it will strategically maneuver its craft orbiting the Red Planet away from the comet’s impacts.
Siding Spring will come within 87,000 miles (139,500 km) of Mars, which is “less than half the distance between Earth and our moon and less than one-tenth the distance of any known comet flyby of Earth,”NASA said.
NASA holdings that are orbiting and roving around Mars will collect data on the comet and its effects on the planet’s atmosphere.
“This is a cosmic science gift that could potentially keep on giving, and the agency’s diverse science missions will be in full receive mode,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate.
“This particular comet has never before entered the inner solar system, so it will provide a fresh source of clues to our solar system’s earliest days.”
“The hazard is not an impact of the comet nucleus itself, but the trail of debris coming from it,” said Rich Zurek, chief scientist for the Mars Exploration Program at NASA’s Jet Propulsion Laboratory.
“Using constraints provided by Earth-based observations, the modeling results indicate that the hazard is not as great as first anticipated. Mars will be right at the edge of the debris cloud, so it might encounter some of the particles — or it might not.”
NASA said the greatest risk to orbiters will begin at about 90 minutes after the closest approach of the comet’s nucleus. This high-point for potential danger will last for 20 minutes, as Mars will at this time come closest to the center of the comet’s trail of dust.
Orbiters are expected to gather data on Siding Spring’s “size, rotation and activity of the comet’s nucleus, the variability and gas composition of the coma around the nucleus, and the size and distribution of dust particles in the comet’s tail,” NASA said.
Mars rovers Opportunity and Curiosity will be protected from any dust thanks to the atmosphere of the planet. Both will collect data from the flyby.
NASA devices on Earth, including the Hubble Space Telescope, will be positioned to observe Siding Spring. NASA space observatories will also monitor the flyby.
NASA’s asteroid tracker, the Near-Earth Object Wide-field Infrared Survey Explorer, is monitoringSiding Spring’s movements, the agency said, while NASA’s two Heliophysics spacecraft, Solar TErrestrial RElations Observatory and Solar and Heliophysics Observatory, will image the comet upon arrival. | 0.879576 | 3.414518 |
Crescent ♏ Scorpio
Moon phase on 2 August 2098 Saturday is Waxing Crescent, 6 days young Moon is in Libra.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 5 days on 28 July 2098 at 08:51.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Moon is passing about ∠21° of ♎ Libra tropical zodiac sector.
Lunar disc appears visually 1.1% wider than solar disc. Moon and Sun apparent angular diameters are ∠1912" and ∠1891".
Next Full Moon is the Sturgeon Moon of August 2098 after 9 days on 12 August 2098 at 01:44.
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 6 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 1219 of Meeus index or 2172 from Brown series.
Length of current 1219 lunation is 29 days, 7 hours and 2 minutes. It is 1 hour and 22 minutes shorter than next lunation 1220 length.
Length of current synodic month is 5 hours and 42 minutes shorter than the mean length of synodic month, but it is still 27 minutes longer, compared to 21st century shortest.
This New Moon true anomaly is ∠355.1°. At beginning of next synodic month true anomaly will be ∠10.1°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
4 days after point of perigee on 28 July 2098 at 15:50 in ♌ Leo. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 9 days, until it get to the point of next apogee on 11 August 2098 at 14:55 in ♒ Aquarius.
Moon is 374 916 km (232 962 mi) away from Earth on this date. Moon moves farther next 9 days until apogee, when Earth-Moon distance will reach 406 374 km (252 509 mi).
Moon is in descending node in ♎ Libra at 04:55 on this date, it crosses the ecliptic from North to South. Moon will follow the southern part of its orbit for the next 14 days to meet ascending node on 16 August 2098 at 17:55 in ♈ Aries.
12 days after beginning of current draconic month in ♈ Aries, the Moon is moving from the middle to the last part of it.
7 days after previous North standstill on 26 July 2098 at 04:44 in ♋ Cancer, when Moon has reached northern declination of ∠28.239°. Next 5 days the lunar orbit moves southward to face South declination of ∠-28.295° in the next southern standstill on 8 August 2098 at 03:03 in ♑ Capricorn.
After 9 days on 12 August 2098 at 01:44 in ♒ Aquarius, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.158335 |
Space should be churned up like a speedboat-filled lake, crisscrossed by gravitational waves rushing at the speed of light in every direction. That’s because any kind of acceleration, of any kind of mass, will produce a gravitational wave. When you whoosh your arm through the air, you are launching a gravitational wave that will travel forever. The Earth produces gravitational waves as it orbits the sun. So do black holes that twirl around or crash into each other.
Every accelerating mass produces a signal, and all those signals should add together into a detectable background.
So where is it? Scientists have been trying to tune in to the staticky drone of gravitational wave background noise for years. An experiment that uses the timing of distant pulsars has been running for over a decade, searching for the portion of the background due to pairs of supermassive black holes. But they haven’t heard a peep.
Then, early this year, the Laser Interferometer Gravitational-Wave Observatory (LIGO) achieved a positive detection of a single gravitational wave event, resulting from the merger of lighter, stellar-mass black holes. The more subtle mission of the pulsar timing experiments and their search for background seemed to get drowned out. They have, after all, produced a null result.
But sometimes silence speaks volumes.
Gravitational waves come in different frequencies, just like light waves. Their frequency is based on their motion—objects in a year-long orbit, no matter their mass, will make waves with the same frequency (though lighter objects will produce a lower-amplitude wave).
Some gravitational-wave sources are strong and close enough that scientists can pick up individual events, like the 200-hertz-frequency “chirp” they detected at LIGO this February, which happened when two black holes around 30 times the mass of the sun merged into one. Others are distant and hard to resolve individually—like close-orbiting, destined-to-merge pairs of supermassive black holes, which can be billions of times bigger than the sun and are often billions of light-years away. These latter, in aggregate, should create a constant background at a much lower frequency than what LIGO can pick up.
“Imagine a gravitational-wave background as being like the surface of the ocean, and we’re on the Earth on a boat.”
It was in the summer of 1967 that astronomer Jocelyn Bell first saw the signal that would give scientists the tools they needed to listen in on this background. She had been hunting for distant galaxies with a radio telescope, when a spike rose above the baseline noise in her data, a pulse of radio waves that reappeared every 1.3 seconds. It looked like a steady heartbeat on an EKG. She was mystified by the regular blip-blip-blip of it. The only objects she knew that could produce such fast, reliable signals were synthetic. She and her advisor, Anthony Hewish, half-jokingly suggested they were looking at a message from aliens, and dubbed the source of the radio waves LGM-1 for “Little Green Man 1.”
Soon, though, astronomers discovered that the signal was coming from something almost as bizarre as aliens—a neutron star, a city-sized star made mostly of crushed-close neutrons that is the remnant left behind after a supernova. Around the time that Bell found her strange signal, two astronomers—Franco Pacini and Thomas Gold—noted that a spinning neutron star surrounded by a magnetic field could emit radiation (although, to this day, scientists cannot explain all the details of why). Gold connected this to Bell’s discovery, explaining how the spin could periodically point a beam of radiation at Earth, making a pulse blip across our telescopes.
Neutron stars can spin around hundreds of times per second, sweeping their beams across space as they do. If these beams happen to be aligned with the Earth, they would briefly illuminate our planet like a distant lighthouse. When scientists found a second pulsing source in 1968, the connection was confirmed: It was located in the middle of the Crab Nebula, which is gas left over from a supernova explosion.
Pulsar clocks are extremely reliable. Because they are so dense, so spherical, and have so much spin momentum, almost nothing can change their rotation rate. The timing of their lighthouse sweep is remarkably constant, earning them the moniker “nature’s best clocks.” The most precise ones—which are also the fastest, called millisecond pulsars—slow their spins by just a few picoseconds per year. By comparison, the most precise atomic clock ever created loses about 66 picoseconds a year.
By 1979, astronomers had realized that they—or, really, someone else in the future with better telescopes—could use these strange, ultra-precise clocks to detect gravitational waves. Steven Detweiler of the University of Florida in Gainesville and Mikhail Vasilievich Sazhin of Moscow State University independently discovered that if a gravitational wave passed over a pulsar, or the Earth, the time at which the pulsar’s emissions arrived at the Earth would change. Astronomers wouldn’t get the tick-tick-tick at the hyper-regular intervals they expected.
“If a gravitational wave passes through the pulsar, it changes the effective distance to that pulsar, rocking it back and forth,” says Maura McLaughlin of West Virginia University in Morgantown, and the former chair of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). That changes how far the emissions have to travel and when they arrive at our planet. The same thing happens if a wave passes through the Earth.
For a tens of billions of solar masses pair of supermassive black holes hundreds of millions of light-years away, a millisecond pulsar’s pulse arrival time would change by microseconds. But most such binaries are expected to be farther away and less massive, and the skew would be just tens of nanoseconds or smaller. In Detweiler and Sahzin’s time, telescope instruments could not take and dump data that fast; computers could not store and process the terabyte-level output; and no one had yet discovered any millisecond pulsars. They needed something else.
In 1982, Ronald Hellings of the Jet Propulsion Laboratory and George Downs of the California Institute of Technology, both in Pasadena, made a breakthrough: They suggested scientists look at lots of pulsars at once, and use their collective late-and-early arrivals to detect the whole noisy gravitational-wave background at once—not individual disturbances. They modeled how that staticky background, buzzing across the universe, would show up in the blips of a bunch of pulsars, which scientists later called a “pulsar timing array.”
Try picturing it, suggests Chiara Mingarelli of the California Institute of Technology in Pasadena. “You can imagine a gravitational-wave background as being like the surface of the ocean,” she says. “And we’re on the Earth on a boat, and we’re bobbing up and down in this gravitational-wave sea.”
So are the pulsars, but their bobbing in the sea looks like pure noise, says McLaughlin, “because they are all happening at different times and are hence uncorrelated.”
It would describe not just individual objects—like the LIGO detection did—but also the formations and evolutions of entire galaxy populations.
But the bobbing from Earth, while it’s noisy, has some structure. That structure is what Hellings and Downs mapped out. When gravitational waves make the Earth bob, they change the arrivals of flashes from all pulsars at the same time. Gravitational waves squeeze in one direction, compressing spacetime, while stretching in the other, expanding it. Imagine that along a north-south line, space condenses. At the same time, east-west expands. Two pulsars in the northern direction of our sky would show similar speedups in the timing of their blips, and two pulsars in an eastern direction would have similar slowdowns.
Hellings and Downs laid out how these late and early arrivals should match up with pulsars spread across the sky. Using their predicted signature and a passel of pulsars, the scientists were able to gain sensitivity over looking at single pulsars. The Hellings-Downs Curve, as the signature signal is now called, is still what astronomers look for today. At the time that Hellings and Downs did their work, though, the technology wasn’t good enough, and astronomers had not discovered any ultra-precise millisecond pulsars. “There was no way,” says McLaughlin. They would need to bury their technique into a time capsule for the future to find.
But they also realized the potential for new science. No one was close to a direct detection of gravitational waves, and LIGO wouldn’t receive its first funding for 12 more years. Pulsar astronomers had a shot at being the first to prove beyond doubt that gravitational waves exist. And on top of that, they could use those gravitational waves to learn about how the universe came to be the way it is. They knew how to be sensitive to the signal, and they knew computers would catch up to the processing speeds the project needed.
Throughout the ’80s and ’90s, people continued work on the gravitational-wave background—in the background. “But they hadn’t really been giving it all they had because we weren’t at the level where we could really expect to make a detection,” says McLaughlin.
Challenging scientists to reconsider their notions of galaxy formation could lead to interesting new science.
But as the years passed, telescope instruments gained more processing power. New pulsars piled up. While astronomers knew of just four millisecond pulsars in the 1980s, they found 31 more in the 1990s, and 65 more between 2000 and 2010. They have discovered 150 since then, bringing the total to 250.
In 2005, Dick Manchester of Australia Telescope National Facility decided it was time to act. He and his colleagues founded the first pulsar search for background gravitational waves: the Parkes Pulsar Timing Array. Using the pastorally located 209-foot Parkes Telescope in New South Wales, which often has sheep meandering beneath its dish, the team began its search. They collected blip after blip from 20 of the most precise pulsars, watching them like airport departure/arrival screens, searching for the Hellings-Downs Curve.
Farther north, astronomers formed the European Pulsar Timing Array later the same year, catching pulsar radio waves with five different telescopes in Effelsberg, Germany; Cheshire, England; Nançay, France; Pranu Sanguni, Italy; and Westerbork, the Netherlands. Each measures 210 to 330 feet across, and they are still running today, keeping time with 18 high-precision pulsars. Because only 24 hours exist in a day, and most telescopes aren’t all-pulsars-all-the-time, having more telescopes involved allows astronomers to spread more observations across instruments.
In the United States, pulsar astronomers were behind, but they had a secret weapon. For telescopes, bigger is better. And like American sodas, American telescopes outweighed the competition. U.S. astronomers had access to the Arecibo Telescope in Puerto Rico, which measures 1,000 feet across, and the Green Bank Telescope in West Virginia, which is 328 feet wide, compared to Europe’s 330-footers and Australia’s single 209-foot dish.
Fred Lo, the director of the National Radio Astronomy Observatory, which operates the Green Bank Telescope, wanted to take advantage of that size difference. In 2008, he called together a group of prominent pulsar scientists who worked at or used his observatory, like McLaughlin, Duncan Lorimer of West Virginia University, and observatory scientist Scott Ransom. Each scientist was working on his or her individual projects, chipping away on their own favorite pulsars. He connected them, telling them to get their act together and start collaborating, and join the hunt for the gravitational-wave background.
“At that time we picked an acronym,” McLaughlin continues. “The most important part, of course.” They called themselves NANOGrav, for the North American Nanohertz Observatory for Gravitational Waves.
Each of the three teams collected and analyzed data from the telescopes they were most familiar with, by virtue of their geographical proximity and federal funding sources. But they all knew that if they combined their work, they would have a better shot at sensing the waves sooner. All three groups linked up in 2009 to form a network of networks: the International Pulsar Timing Array (IPTA). Using a list of 39 of the best pulsars, they got to work. Today, that list has grown to roughly 100. And while some competition exists among pulsar-precisionist groups, the scientific benefits of sharing data outweigh the costs. “There are people who really want to be the ones to do it and to get the glory, but I think that is a small group of people,” says McLaughlin. “Nearly everyone has accepted that the first detection will come from IPTA data.”
In a sense, though, NANOGrav has already produced new science, even without recording a single bit of signal.
What’s not widely appreciated is that the silence from pulsar timing array experiments is some of the first science—beyond “we found them!” or “we didn’t find them!”—to come out of decades of experimental gravitational-wave work. That’s why McLaughlin gets upset when the LIGO discovery looms so large that no other research seems important. “I’ve had several people say, ‘So are you guys just going to give up now?’ ” she says. “I’m like, ‘Noooo, that’s not the point.’ ”
Because the gravitational background noise that NANOGrav is searching for would come from a whole population of supermassive black holes, it would describe not just individual objects—like the LIGO detection did—but also the formations and evolutions of entire galaxy populations. As a result, the size of the signal reflects some of the basic features of our universe.
To estimate the size of that signal, scientists used models of how many double supermassive black holes the universe holds, how big they are, how fast they whip around each other, and where they are. These estimates reflected the state of the art understanding about how galaxies form, how they change over time, and how they get bigger. The conclusion was that, if they monitored around 20 pulsars for five to 10 years, their sensitivity should be sufficient to hear the nanohertz gravitational background drone. When, 11 years after array initiation, they still had found nothing, they effectively learned that some of those initial assumptions were wrong. All three teams estimated in 2015 that the actual noise amplitude had to be at least 10 times lower than their initial estimates.
This lowering of expected signal strength was a kind of anti-news, the opposite of LIGO’s historic detection. But challenging scientists to reconsider their notions of galaxy formation and evolution could lead to interesting new science. Perhaps fewer galaxies host big black holes in their centers than scientists thought—and right now scientists think that almost all substantial (non-dwarf) galaxies do. Maybe galaxy mergers are less frequent than was estimated. (Right now, says Mingarelli, they are trying to figure out what “fewer” actually means.) Or maybe the time between the first encounter between two black holes and their coalescence doesn’t quite follow the equation theorists have developed. It could also be that most black hole mergers stall out somehow before the holes are close enough to emit swelling (detectable) gravitational waves, and that the pair just keep orbiting each other endlessly and never merge. Or maybe scientists have been sizing supermassive black holes all wrong, and they are smaller than once thought, so that their waves are smaller. Right now, all of these scenarios are in play as possibilities.
Of course, the goal remains to make an actual detection. Based on new calculations from their nine-year dataset, NANOGrav estimates that they will reach the sensitivity necessary to finally hear the static in another five to 10 years. In their latest paper, their sensitivity estimates include adding four new hyperstable pulsars each year, taking them from 54 to around 100. “I think pulsar-timing is ready in terms of people, techniques, and analysis,” says Michele Vallisneri, a member of the LIGO collaboration, a visiting associate at the California Institute of Technology, and a research scientist at the Jet Propulsion Laboratory. But, he cautions, it is also possible that “nature may have put our goal farther than we think it is.”
Time to detection also depends on something more down-to-Earth: funding. “[If] we lose access to either the Green Bank Telescope or Arecibo, the time to detection is pushed back several years … and possibly forever if we lose both,” says McLaughlin. The National Science Foundation will stop funding Green Bank in 2017 or 2018, and the observatory is pursuing private partnerships. At Arecibo, threats of closure have popped up for years—including this summer, as one also did for Parkes—but both telescopes remain open. Those in Europe are, so far, safe.
Whatever happens, NANOGrav is one example of what will become many categories of instruments to complement LIGO’s initial discovery, says Vallisneri. As he puts it, “astronomers didn’t stop looking after Galileo first saw the satellites of Jupiter and the phases of Venus.”
Sarah Scoles is a writer based in Denver, Colorado, and a contributor at Wired Science.
The lead photocollage was created with images from: ESO/G. Bono & CTIO and Pixabay | 0.863957 | 4.094982 |
In an unprecedented feat, an American research team discovered hidden secrets of an elusive exoplanet using a powerful new instrument at the 8-meter Gemini North telescope on Maunakea in Hawai’i. The findings not only classify a Jupiter-sized exoplanet in a close binary star system, but also conclusively demonstrate, for the first time, which star the planet orbits.
The breakthrough occurred when Steve B. Howell of the NASA Ames Research Center and his team used a high-resolution imaging instrument of their design — named ‘Alopeke (a contemporary Hawaiian word for fox). The team observed exoplanet Kepler-13b as it passed in front of (transited) one of the stars in the Kepler-13AB binary star system some 2,000 light-years distant.
Prior to this attempt, the true nature of the exoplanet was a mystery. The research was published in the Astronomical Journal. Howell said:
“There was confusion over Kepler-13b: Was it a low-mass star or a hot Jupiter-like world? So we devised an experiment using the sly instrument ‘Alopeke.
“We monitored both stars, Kepler A and Kepler B, simultaneously while looking for any changes in brightness during the planet’s transit.
“To our pleasure, we not only solved the mystery, but also opened a window into a new era of exoplanet research.”
Chris Davis of the National Science Foundation, one of Gemini’s sponsoring agencies, added:
“This dual win has elevated the importance of instruments like ‘Alopeke in exoplanet research.
“The exquisite seeing and telescope abilities of Gemini Observatory, as well as the innovative ‘Alopeke instrument, made this discovery possible in merely four hours of observations.”
‘Alopeke performs “speckle imaging,” collecting a thousand 60-millisecond exposures every minute. After processing this large amount of data, the final images are free of the adverse effects of atmospheric turbulence — which can bloat, blur, and distort star images. Howell said:
“About one half of all exoplanets orbit a star residing in a binary system, yet, until now, we were at a loss to robustly determine which star hosts the planet.”
The team’s analysis revealed a clear drop in the light from Kepler A, proving that the planet orbits the brighter of the two stars. Moreover, ‘Alopeke simultaneously provides data at both red and blue wavelengths, an unusual capability for speckle imagers. Comparing the red and blue data, the researchers were surprised to discover that the dip in the star’s blue light was about twice as deep as the dip seen in red light.
This can be explained by a hot exoplanet with a very extended atmosphere, which more effectively blocks the light at blue wavelengths. Thus, these multi-color speckle observations give a tantalizing glimpse into the appearance of this distant world.
Early observations once pointed to the transiting object being either a low-mass star or a brown dwarf (an object somewhere between the heaviest planets and the lightest stars). But Howell and his team’s research almost certainly shows the object to be a Jupiter-like gas-giant exoplanet with a “puffed up” atmosphere due to exposure to the tremendous radiation from its host star.
‘Alopeke has an identical twin at the Gemini South telescope in Chile, named Zorro, which is the word for fox in Spanish. Like ‘Alopeke, Zorro is capable of speckle imaging in both blue and red wavelengths.
The presence of these instruments in both hemispheres allows Gemini Observatory to resolve the thousands of exoplanets known to be in multiple star systems. Team member and ‘Alopeke instrument scientist Andrew Stephens at the Gemini North telescope said:
“Speckle imaging is experiencing a renaissance with technology like fast, low noise detectors becoming more easily available.
“Combined with Gemini’s large primary mirror, ‘Alopeke has real potential to make even more significant exoplanet discoveries by adding another dimension to the search.”
First proposed by French astronomer Antoine Labeyrie in 1970, speckle imaging is based on the idea that atmospheric turbulence can be “frozen” when obtaining very short exposures. In these short exposures, stars look like collections of little spots, or speckles, where each of these speckles has the size of the telescope’s optimal limit of resolution.
When taking many exposures, and using a clever mathematical approach, these speckles can be reconstructed to form the true image of the source, removing the effect of atmospheric turbulence. The result is the highest-quality image that a telescope can produce, effectively obtaining space-based resolution from the ground — making these instruments superb probes of extrasolar environments that may harbor planets.
The discovery of planets orbiting other stars has changed the view of our place in the Universe. Space missions like NASA’s Kepler/K2 Space Telescope and the Transiting Exoplanet Survey Satellite (TESS) have revealed that there are twice as many planets orbiting stars in the sky than there are stars visible to the unaided eyes; to date, the total discovery count hovers around 4,000.
While these telescopes detect exoplanets by looking for tiny dips in the brightness of a star when a planet crosses in front of it, they have their limits. Howell said:
“These missions observe large fields of view containing hundreds of thousands of stars, so they don’t have the fine spatial resolution necessary to probe deeper.
“One of the major discoveries of exoplanet research is that about one-half of all exoplanets orbit stars that reside in binary systems. Making sense of these complex systems requires technologies that can conduct time sensitive observations and investigate the finer details with exceptional clarity.”
“Our work with Kepler-13b stands as a model for future research of exoplanets in multiple star systems.
“The observations highlight the ability of high-resolution imaging with powerful telescopes like Gemini to not only assess which stars with planets are in binaries, but also robustly determine which of the stars the exoplanet orbits.”
Provided by: Gemini Observatory [Note: Materials may be edited for content and length.] | 0.841558 | 3.904151 |
Tuesday, September 9, 2014
Two models of the dark matter distribution in the halo of a galaxy like the Milky Way, separated by the white line are shown. The colors represent the density of dark matter, with red indicating high-density and blue indicating low-density. On the left is a simulation of how non-interacting cold dark matter produces an abundance of smaller satellite galaxies. On the right the simulation shows the situation when the interaction of dark matter with other particles reduces the number of satellite galaxies we expect to observe around the Milky Way. (Credit: Durham University)
Cassini spied just as many regular, faint clumps in Saturn’s narrow F ring (the outermost, thin ring), like those pictured here, as Voyager did. But it saw hardly any of the long, bright clumps that were common in Voyager images. (Credit: NASA/JPL-Caltech/SSI)
Oscillations of photons create an image of frozen light. At first, photons in the experiment flow easily between two superconducting sites, producing the large waves shown at left. After a time, the scientists cause the light to “freeze,” trapping the photons in place. Fast oscillations on the right of the image are evidence of the new trapped behavior. (Credit: Princeton University)
Erlangen-based physicists have sent bright pulses in sensitive quantum states through the window of a technical services room on the roof of the Max Planck Institute for the Science of Light to a building of the University Erlangen-Nürnberg. These types of light flashes are easy to receive even when the sun is shining brightly, unlike the signals of individual photons used to date. (Credit: MPI for the Science of Light)
The gravity of a black hole swallows the matter around it. The link between tensor networks and quantum entanglement may prove useful in studying the physics of black holes, some physicists propose. (Credit: M. Weiss, Chandra X -ray Center/NASA)
Square, cage-shaped molecules called diamondoids (left) linked to soccer-ball shaped buckyballs (right) create a new molecule called a buckydiamondoid, center, in this illustration. These new hybrid molecules may be useful for developing molecular electronic devices in the future. (Credit: Manoharan Lab/Stanford University)
Machines have surpassed humans in physical strength, speed and stamina. What if they surpassed human intellect as well? Science fiction movies have explored this question. In the classic “2001: A Space Odyssey,” astronaut David Bowman, played by Keir Dullea, struggles for control of the spacecraft against the sentient computer HAL 9000. | 0.810491 | 3.702157 |
While life is rapidly changing all over the globe right now, the rest of the solar system is going about business as usual. And that includes our planetary neighbor Mars, where NASA’s Mars Reconnaissance Orbiter has captured a particularly stunning image of the strange ridges and channels formed on the planet’s surface by erosion.
This area of Mars is called the Juventae Chasma, a huge canyon that stretches over 150 miles wide and which is named after the mythical fountain of youth. On the floor of the canyon, you’ll find sand dunes and a mountain of sulfate deposits which is one and a half miles high. This region has many areas of striking layers, in which different sediments have been deposited on top of one another and eroded to form elaborate patterns that can be seen from orbit.
You can see a large, high-resolution version of the image here to appreciate all the beautiful details of this literally unearthly scene.
“There are three distinct terrains in this image, plains with possible inverted channels, plains with exposed layers, and layers on a wall of Juventae Chasma,” the HiRISE researchers explained in a post. “Layers are common in the Martian canyons, but it is unknown what process formed them. The layers in the plains here are likely made of the same material as the layer in the canyons.”
This particular image was captured with an instrument called the High-resolution Imaging Experiment (HiRISE) camera on board the Mars Reconnaissance Orbiter (MRO). The MRO has been an essential NASA tool for observing Mars since it entered orbit around the planet in 2006. As well as cameras, the MRO also carries scientific instruments including spectrometers and radar, which can be used in combination to study the geography and weather of Mars.
HiRISE has captured plenty of stunning images of Mars in its career, including snapping photos of both of NASA’s explorers, Curiosity and InSight, on the surface of the planet. But perhaps its most famous finding was something even more out of this world, when last year it captured an image of a martian lava formation that looked strikingly like the Star Trek logo.
- We’re going to the red planet! All the past, present, and future missions to Mars
- See how volcanoes and tectonic activity shaped the Martian surface
- How NASA’s Perseverance Rover will search for life on Mars
- NASA shakes, rattles, and rolls Perseverance rover in Mars 2020 test
- Even on Mars, the Curiosity rover needs to wash its hands | 0.864551 | 3.625157 |
A team of scientists has discovered the farthest planet within our Solar System during their search for the legendary Planet Nine. The mysterious object is a dwarf planet that is located at more than 120 times more distant than Earth is from the Sun.
International Astronomical Union’s Minor Planet Center announced the existence of this dwarf planet. As its official name is hard to remember, 2018 VG18, its discoverers nicknamed it Farout. The US scientists Scott Sheppard of the Carnegie Institute, David Tholen of the University of Hawaii, and Chad Trujillo of the University of Northern Arizona have discovered the new planet by chance.
What they were really looking for was the mysterious Planet Nine. Although it has not been possible to observe this so-called Planet X for now, the team of astronomers believes that it exists because of the supposed influence that its gravity exerts on other smaller bodies.
“2018 VG18 is farther and moves slower than any other object in the Solar System, so it will take us years to determine what its orbit is,” Sheppard said in a press release.
Astronomers Discovered The Farthest Planet Within Our Solar System
“The planet was found at a point in the sky close to that of other more distant bodies known so that it may have an orbit similar to the rest. The similarities in the orbits of many of these objects are the basis for the possible existence of a massive planet at several hundred astronomical units, that influences their orbits,” the astronomer added.
The new planet takes more than 1,000 years to orbit the Sun. According to the researchers, the “Farout” dwarf planet is about 500 kilometers in diameter and appears in pink nuances, suggesting the presence of large amounts of ice on its surface. Also, this small planet, like the other distant ones found so far by astronomers, indicate that a more massive body exists farther away in the Solar System. It could be the legendary Planet Nine.
“The orbital similarities shown by many of the known small, distant Solar System bodies was the catalyst for our original assertion that there is a distant, massive planet at several hundred AU shepherding these smaller objects,” Sheppard added.
Vadim is a passionate writer on various topics but especially on stuff related to health, technology, and science. Therefore, for Great Lakes Ledger, Vadim will cover health and Sci&Tech news. | 0.813862 | 3.067025 |
Hubble: A Journey To Infinity
We, humans, are always fascinated by the night sky from the time unknown. Before the invention of the telescope we used to observe the sky with naked eyes. With these observations we found patterns in the stars which are known as constellations.
Here we faced an unfortunate complication that human eyes have limits. They cannot dip into the infinity where millions of galaxies, stars, nebulas exist. Here came the man, Galileo Galilei, who is 1609, invented the first telescope, and enjoyed the unseen beauty of the night sky for the first time.
As nothing is final in the field of science and everything keeps on evolving with time, telescopes are no exception to this. After Galileo, larger and more accurate telescopes were invented. We fix telescopes at one place and then take observations with revolving them in desired directions
Need of the Hubble telescope:
As discussed above, if we can make the most advanced telescopes in laboratories and put them in the desired locations, then why we need a telescope like Hubble? A simple answer to this question is, we need the Hubble telescope because of atmospheric factors like dust, smog, pollution effect on images captured by normal telescopes.
The Hubble telescope is placed in space away from earth, so Hubble telescope can capture images without any distraction of dust or pollution. So the cleanest images can be obtained using the Hubble telescope.
Why the name ‘ Hubble’:
The name Hubble is given to this telescope to honor the exceptional contribution by U. S. Astronomer Edwin Hubble to the field of astronomy. Hubble revolutionized the field of astronomy in several aspects like the size of the universe and classification of galaxies. The Hubble Sequence created by Edwin Hubble is still used by scientists for the classification of the galaxies.
After years since his death, Hubble remains the most famous astronomer in the world. In 1920, Mr. Hubble used the largest telescope of his time, which was placed on the Mount Wilson Laboratory to discover distant galaxies.
So no wonder why NASA (National Aeronautics Space Research and Administration) considered the name Hubble for their space telescope mission in 1990.
Structure of Hubble:
The Hubble telescope has a mirror-based optical system. The optical telescope assembly gives Hubble a unique view gathering infrared, visible and ultraviolet light.
Hubble utilizes two mirrors which are fixed in a Cassegrain manner. Hubble includes fine guidance sensors which can be locked at the planets or other celestial bodies. The third wide-field camera is the main camera on Hubble.
The advanced camera for surveys is used to capture the large space. The cosmic origins spectrograph captures ultraviolet light. A space telescope imaging spectrograph is used to inspect the temperature of astronomical bodies. The multi-object spectrometer senses the deep space objects with the amount of heat they liberate.
How Hubble works?
Hubble is an astronomical telescope that revolves around the earth with a speed of 8 km/hr. It completes one revolution around the earth within 97 minutes. Hubble is fitted with several scientific instruments. Hubble’s mirror captures the light and then pass it within these instruments.
Light first of all hits the primary mirror, then gets bounced to the secondary mirror and then to the hole through which it continues to move towards these scientific instruments. The point should be noted that Hubble focuses on capturing more and more light from the distant parts of the universe rather than magnifying objects.
All the Hubble’s functions are powered by Sunlight only. Obviously, with sunlight, come the solar panels. Hubble uses solar arrays that directly convert sunlight into electricity. Like on earth we have nights the shadow of the earth affects the efficiency of these solar arrays. Some batteries keep the telescope in the working condition when the telescope is within the shadow of the earth. The cosmic origins spectrograph mainly focuses upon collecting the ultraviolet light from the distant and unknown parts of the universe.
Feats of the Hubble Telescope:
The Hubble telescope has expanded the boundaries of the universe beyond the limit of our imagination. Here are some of the Hubble’s unmatched feats:
- Calculation of the exact age of the universe:
The Hubble space telescope is the first device to calculate the right age of the universe. To achieve this feat with Hubble scientists used the brightness of Cepheid variable stars which are a special kind of stars which pulse on a set cycle.
Today, we know that the universe is 13.7 billion years old and all this prediction is possible with the help of Hubble’s data only.
Capturing earliest galaxies:
We all know that there are countless galaxies in the universe just like our milky way. But knowing the galaxies that were a part of the beginning universe can help us to find how the universe was made.
Five years after the launch from 1990, mission controllers directed Hubble towards an empty spot in the space. Guess what they found, the image that Hubble found became one of the most iconic images and revealed the existence of thousands of new and early age galaxies.
Dark matter is the matter which is invisible but comes into the light with the perspective of gravity. Dark matter occupies 23 % of the observable universe.
Hubble has helped to create the biggest scale 3D maps of places where the dark matter exists. These observations conclude that the clumpiness of the dark matter has increased over time.
More the star-forming in a galaxy more will be the gamma-ray bursts. Gamma-ray bursts are the biggest explosions ever known to science. These explosions release energies that the sun can emit in 10 billion years within a few seconds. These bursts are a result of stars which are collapsed to form black holes.
Hubble has helped to know these mysterious explosions with a better perspective.
The Stunning Collapse of Comet Shoemaker-Levy 9:
As we all have the idea that Jupiter is the heaviest object in the solar system. Jupiter has got a massive gravitational pull that keeps on attracting heavy astronomical bodies.
In 1994, the Comet Shoemaker-Levy 9 came into contact with this powerful gravity of Jupiter and collided with this massive planet, shattering into pieces. All moments of this thrilling journey were captured by the Hubble telescope.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2020 Suyash | 0.810147 | 3.612356 |
Mar 21, 2019
The Milky Way is built from plasma.
NASA launched the Fermi Gamma-Ray Space Telescope on June 11, 2008. Its primary mission is observing high frequency electromagnetic waves in space, including gamma-rays. Gamma-rays are the most energetic of the three types of radioactivity, with values 10^15 times greater than visible light. They also have short wavelengths, less than 0.1 nanometers, in some instances. Since gamma-rays are unable to penetrate Earth’s atmosphere, Fermi was placed in high orbit.
A recent press release announced that Fermi detected several sources of gamma-ray emissions from the center of the Milky Way. Gamma-rays are theoretical particles called photons: “massless” force carriers known as bosons. However, since they travel at velocities that can exceed 2.993 x 10^10 centimeters per second, “relativistic effects” come into play. That velocity is thought to impart significant momentum to the photons, enough for them to have an impact on normal matter. Thus, gamma-rays are “ionizing radiation”, since they can knock electrons out of an atom.
Plasma is defined by charged particles: neon lights, lightning, planetary magnetospheres, stars, and galaxies are composed of various plasmas. It is important to remember that plasmas are a condition of matter. Although solid, liquid and gaseous states might prevail on Earth, plasma is another form of matter that exhibits unique properties.
Electricity can move through plasma in circuits. Electric circuits in space distinguishes Electric Universe theory from conventional viewpoints. Mysterious phenomena can be explained using observational evidence coupled with the results from laboratory experiments. That distinguishes Electric Universe concepts from others, since gravity cannot be examined in the laboratory.
Stars and galaxies are embedded in a circuit of electricity that flows through the Universe, so electromagnetism should be used as a basis for theories about their origins and evolution. For example, gamma rays extend axially beyond the Milky Way’s center, arising from an “X” shaped central structure. Each hourglass-shaped formation is about 65,000 light-years in diameter.
Lobes of radiation from the galactic core are clues to the formation of the X. The hourglass is a signature of Birkeland currents squeezing plasma and charged dust into z-pinch compression zones. Electric forces align those channels into filaments that attract each other. Electric fields generate a force that can be 39 orders of magnitude greater than gravity. However, when they get close to each other, the plasma “cables” twist into a helix that rotates faster as it compresses tighter. It is those “cosmic transmission lines” that make up galactic circuits.
Electric currents flow out along the galactic spin axis and form double layers that, as mentioned, can sometimes be seen as X-ray and gamma-ray lobes around active galaxies. The electric fields then spread out around the galaxy’s circumference, returning to the core along the spiral arms. Large-scale plasma discharges exhibit electrodynamic behavior. Gravity contributes to galaxies, but it is not the fundamental energy source.
Helical Birkeland currents, traveling through regions of high flux density, are forming the X in the center of the Milky Way. Concentrations of stars can identify Birkeland currents, so the circuits in the Milky Way are mapped-out by its glow discharges. | 0.897035 | 4.095939 |
NASA’s newest planetary probe, the OSIRIS-REx asteroid sampling spacecraft, is merrily snapping its ‘First-Light’ images following the successful power up and health check of all of the probes science instruments, barely three weeks after a stunning sunset launch from the Florida Space Coast – as it is outbound to asteroid Bennu.
“The spacecraft has passed its initial instrument check with flying colors as it speeds toward a 2018 rendezvous with the asteroid Bennu,” NASA officials reported in a mission update.
All five of the Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft science instruments and one of its navigational instruments were powered on, starting last week on September 19.
NASA says they are all fully healthy for the groundbreaking mission whose purpose is to visit the carbon rich asteroid Bennu, snatch samples from the black as coal surface and return them to Earth in 2023 inside a Sample Return Capsule that will soft land by parachute in the Utah desert.
The seven year roundtrip mission to Bennu and back could potentially bring back samples infused with the organic chemicals like amino acids that are the building blocks of life as we know it.
“The data received from the checkout indicate that the spacecraft and its instruments are all healthy.”
The ‘First-Light’ image shown above was taken on Sept. 19, 2016 by the probes OCAMS MapCam camera and recorded a star field in Taurus, north of the constellation Orion along with Orion’s bright red star Betelgeuse.
“MapCam’s first color image is a composite of three of its four color filters, roughly corresponding to blue, green, and red wavelengths. The three images are processed to remove noise, co-registered, and enhanced to emphasize dimmer stars,” researchers said.
The OSIRIS-REx Camera Suite (OCAMS) was the first of the five science instrument to be tested and checlked out perfectly with “no issues.” It was provided by the University of Arizona and is comprised of three cameras which will image and map Bennu in high resolution.
All the other instruments were also powered on and checked out flawlessly – including the OSIRIS-REx Laser Altimeter (OLA) which fired its laser, the OSIRIS-REx Visible and Infrared Spectrometer (OVIRS), the OSIRIS-REx Thermal Emissions Spectrometer (OTES), and the student designed Regolith X-ray Imaging Spectrometer (REXIS).
Lastly, the Touch and Go Camera System (TAGCAMS) navigational camera was successfully powered on and tested.
Furthermore, TAGCAMS took a dramatic image of the spacecraft’s Sample Return Capsule (below) – which is designed to bring at least a 60-gram (2.1-ounce) sample of Bennu’s surface soil and rocks back to Earth in 2023 for study by scientists using the world’s most advanced research instruments.
The capsule image was captured by the StowCam portion of TAGCAMS when it was 3.9 million miles (6.17 million km) away from Earth and traveling at a speed of 19 miles per second (30 km/s) around the Sun.
The StowCam image of the Sample Return Capsule shows it “is in perfect condition,” according to the science team.
The OSIRIS-REx spacecraft departed Earth with an on time engine ignition of a United Launch Alliance Atlas V rocket under crystal clear skies on Thursday, September 8 at 7:05 p.m. EDT from Space Launch Complex 41 at Cape Canaveral Air Force Station.
The ULA Atlas V injected OSIRIS-Rex perfectly onto its desired trajectory.
“We got everything just exactly perfect,” said Dante Lauretta, the principal investigator for OSIRIS-REx at the University of Arizona, at the post launch briefing at the Kennedy Space Center. “We hit all our milestone within seconds of predicts.
The space rock measures about the size of a small mountain at about a third of a mile in diameter.
“The primary objective of the OSIRIS-Rex mission is to bring back pristine material from the surface of the carbonaceous asteroid Bennu, OSIRIS-Rex Principal Investigator Dante Lauretta told Universe Today in a prelaunch interview in the KSC cleanroom with the spacecraft as the probe was undergoing final preparations for shipment to the launch pad.
“We are interested in that material because it is a time capsule from the earliest stages of solar system formation.”
“It records the very first material that formed from the earliest stages of solar system formation. And we are really interested in the evolution of carbon during that phase. Particularly the key prebiotic molecules like amino acids, nucleic acids, phosphates and sugars that build up. These are basically the biomolecules for all of life.”
The asteroid is 1,614-foot (500 m) in diameter and crosses Earth’s orbit around the sun every six years.
After a two year flight through space, including an Earth swing by for a gravity assisted speed boost in 2017, OSIRIS-REx will reach Bennu in Fall 2018 to begin about 2 years of study in orbit to determine the physical and chemical properties of the asteroid in extremely high resolution.
Watch my up close launch video captured directly at the pad with the sights and sounds of the fury of blastoff:
Video Caption: ULA Atlas V rocket lifts off on September 8, 2016 from Space Launch Complex 41 at Cape Canaveral Air Force Station carrying NASA’s OSIRIS-REx asteroid sampling spacecraft, in this remote camera view taken from inside the launch pad perimeter. Credit: Ken Kremer/kenkremer.com
Watch for Ken’s continuing OSIRIS-REx mission reporting. He reported on the spacecraft and launch from on site at the Kennedy Space Center and Cape Canaveral Air Force Station, FL.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news. | 0.867427 | 3.305626 |
A new dawn casts vibrant light onto the fatigued dreamers. Warmth resonates throughout the chamber as the inhabitants slowly awaken. Hopeful eyes trace the luminous glow as the halls of the vessel illuminate. “Might the visions be realized?”, an elder occupant inquires, as his voice begins to crack. “Are we starting the adventure?”, a young child asks with wide eyes.
For those enthralled by the wonders of the Universe, space exploration often embodies the ultimate means of connecting with our origins.
Through the lenses of our telescopes, we are reminded of the true extent of our backyard. Yet, the pane of glass through which we observe the cosmos reflects the lingering barrier between our ground locked civilization and the boundless corridors of space.
Seldom moments of lucidity whisper softly that we are not alienated fragments displaced in a grand celestial web, but that we comprise its very fibers.
Can we dissolve the barrier?
Astronomy remains one of the few scientific fields that require little to no tools to engage with. In fact, the only tool you need is your eye - the first telescope ever designed (thank you nature)!
As a result, observing the night sky has threaded our human history. For millennia, we have peered above to comprehend the dynamics of brilliant stars, neighboring rocky and gaseous worlds, and even the Universe itself. We’ve even linked deities to heavenly bodies due to their ethereal nature.
Could the ancient cultures have envisioned that one day we would command instruments that now venture along the outskirts of our solar system, uncovering its secrets along the way? Perhaps, even more striking for them would be our trips to the Moon or our residency aboard the International Space Station.
What milestones will astonish our descendants?
The Darkness Beckons
The Moon is the furthest our species has ever voyaged (last visited in 1972).
On average, the Moon is 384,400 kilometers (238,855 miles) away from Earth. Comparatively, the most distant planet in our solar system, Neptune, is 4.4 billion kilometers (2.8 billion miles) from Earth. If the Earth-Neptune distance was equivalent to the New York-California distance, the Earth-Moon distance would be less than a quarter of the length of the Brooklyn Bridge (~ 1 mile).
We tread cautiously along the sandy shoreline of the vast cosmic seas. In the distance, gems twinkle in the darkness. Vivid spherical structures collapse dense pockets of matter to birth new stars. Photons traverse infinite depths to illuminate hidden columns of gas and dust.
Obscured worlds, potentially teeming with life, orbit parent stars beyond our veil.
Will we depart our dock?
A Flicker in the Night
In 2019, NASA announced a plan to return humans to the Moon in the 2020s, with the assistance of commercial partners. The program was termed “Artemis”, the twin sister of Apollo and the goddess of the Moon in Greek Mythology. The agency subsequently declared its intention to utilize the Moon as a base station for future travel to Mars.
The doorway impeding exploration opens anew. A generation frozen in nostalgia gradually regains motion. Sparks glisten within the spirits of children and adults born after Apollo. Enthusiasm blossoms in the hearts of astronauts daring enough to charter into the unknown.
What will embark with us?
Throughout human evolution, profound changes have altered our cultural, economic, and political structures; yet, certain elements invariably surface across all human epochs. Conflict scars much of our brief history on this planet.
As we avert our gaze towards new horizons, what aspects of our humanity will be transported along the trek? Will we sail as a species or as separate nations? If commercial partners invest, what return will be their return? Can land be owned beyond Earth?
Uncertainty permeates the collective mind. However, the desire to explore remains ingrained and the call to push the bounds of familiarity prevails.
The desire to stretch our cosmic perspective burns fiercely through the night for the tireless dreamers.
Will we unite?
The Cosmic Sail initiates its routine start-up sequence. The floor rumbles as the vessel’s engines fire. “We’ll be taking off shortly, folks. Please buckle up until we clear Earth’s gravity. We’ll do our best to ensure a smooth journey”, the captain affirms in a soothing tone.
The Sun shines intensely this morning.
A mother smiles as she buckles in her daughter. “Yes Amber, we are starting our grand adventure today.” | 0.89583 | 3.572829 |
New York Herald Tribune
March 3, 1935
Nikola Tesla Doubts Link Between Rays and Outburst of Nova Herculis. Inventor Says Light and Particles do Not Travel at the Same Speed.
The Herald Tribune of January 20, 1935, contained a report relating to some observations of cosmic rays made by Dr. Werner Kolhoester, director of the Observatory of Potsdam, in connection with the outburst of Nova Herculis (the "new" star) noted in December of last year. I had intended to offer a few words of comment upon the same at that time, but thought it advisable to read first the original statement published in the Supplement of the "Berliner Tageblatt" of January 20, 1935, which has been forwarded to me through the courtesy of the German Consulate.
Would Confirm His Theory
This news item has interested me, as the results announced, if valid, would be another confirmation of my theory of cosmic rays advanced in 1896 according to which these radiations can only emanate from such vast and incandescent heavenly bodies as our sun, placed in an almost perfect vacuum and charged to tremendous potentials, sufficient for imparting to minute similarly electrified particles immense speeds and energies by electrostatic repulsion. I have proved this theory rigorously by experiments and deductions, but had I not done so, it would still be established as a scientific truth, for there is no force or effect produced in the universe which, even if amplified millions of times, could account for the cosmic phenomena discovered by me.
Now, a Nova, in its phase of greatest brightness and transcending temperature at the surface, is a generator of cosmic rays incomparably more powerful than our sun. But while this is unquestionably true, the findings of the German radiologist are open to serious objections.
In the first place, calculation conformable to my theory shows that in order to cause an increase in the intensity of the rays of the order found, the surface temperature of the star, assuming its distance 1,200 light years, could not have been much less than 5,000,000 degrees centigrade. Such a high value is extremely improbable although in a Nova, in which radiation of heat from the inside is greatly facilitated by expansion, the difference in the temperatures of the central and peripheral parts may not be very great.
Then, again, the increase recorded, amounting to about 1 percent of the intensity of cosmic rays emitted by our sun, is too small for drawing a reliable conclusion in view of the influence of weather conditions and other disturbing causes. It must also be borne in mind that the coincidence method adopted is far from being accurate.
There exists, however, an element of incertitude which in itself is sufficient to invalidate completely the results obtained and of which Dr. Kolhoerster does not seem to have thought. Light is a wave motion of definite velocity, determined by the elastic force and density of the medium. Cosmic rays are particles of matter, the speed of which depends on the propelling force and mass and may be much smaller or greater than that of light.
Difference in Speeds
Consequently, there can be no concordance in the phases of the two disturbances at the place of observation. The cosmic rays, generated during the maximum brightness of the star, may reach the place many centuries sooner or later than the light, according to their speed. It thus appears that the results announced cannot have been due to Nova Herculis. Considering further the briefness and small number of star outburts, it is evident that the Novae cannot contribute appreciably to the steady rain of cosmic particles pouring upon the earth from the countless suns of the universe. | 0.803251 | 3.184346 |
How Salts on the Surface Could Aid in Modeling Europa’s Ocean
Even though there are planned missions to explore Jupiter’s moon Europa, they are unlikely to sample the depths of its potentially habitable ocean. So a new paper, published in the journal Icarus, lays out how we may be able to probe those deep waters from their expression on the surface.
Europa is one of Jupiter’s 79 moons, and one of the largest moons in the Solar System. Inside Europa, beneath sheets of ice, liquid water rests on top of a rocky core, similar to Earth, and the chemical interaction between the water and the rock could make Europa one of the best known candidates for other life in our Solar System.
Most of what we know about the moon is thanks to NASA’s Galileo mission, which launched in 1989 and found evidence for Europa’s salty oceans. To date, no mission has landed on the moon.
Current models, based on the interactions between the ocean’s water and the moon’s rocky core, predict that the ocean’s chemistry is dominated by four species of ionic components (ions being electrically-charged atoms and molecules): sodium (Na), magnesium (Mg2), chlorides (Cl-) and sulphates (SO42). These ions are able to inter-act with each other, forming a range of compounds. It is the relative concentration of their resulting compounds that helps determine whether the ocean could be habitable.
“For comparison, many species thrive in the mildly salty oceans on Earth, whereas only a few species have been able to adapt to extremely salty environments like the Dead Sea,” says Mathieu Choukroun, who is a planetary scientist at NASA’s Jet Propulsion Laboratory and who was speaking on behalf of the authors of the Icarus paper, on which he is a co-author.
The researchers developed flowcharts, modeling the abundance of the different components under various scenarios, and then tested them in the laboratory. So, for example, a low concentration of magnesium ions (Mg2+) on the frozen surface would indicate an acidic ocean, whereas a high level would point to alkali waters. This constrains the type of life that could exist there.
Also, the presence of certain combinations of compounds on the surface could indicate the origin of other compounds. For example, it would not be possible for sodium chloride and magnesium sulphate to form together while freezing in an ocean-like mixture – one would form, or the other, depending on the concentration. If both were ob-served together on the surface, it would imply that one of them must have formed on the surface. “This would likely be the magnesium sulphate, formed from the frozen magnesium chloride that [was] later on subject yo sulphur implantation,” Choukroun explains.
He says that the flowcharts are the first step toward a convenient way to estimate the relative ionic concentrations in the water below Europa’s frozen surface.
Objectives for Europa Clipper
Planned future missions will be able to hunt for these ionic species via instruments in orbit or in-situ. The Europa Clipper mission, which is set to launch in 2023, will study Europa’s surface and interior through a series of fly-bys. Some of the onboard scientific instruments will be able to identify these components on the surface.
NASA is also considering a Europa lander mission, with the goal of sending a science platform to the surface of that moon to search for past and present life, and whether Europa could be habitable.
“A Europa lander mission is in formulation, but there is no current plan to drill [into the surface] all the way to the ocean,” says Choukroun. “Thus, until a future mission, whether it is a lander, rover, or submarine, is able to reach the ocean directly, our understanding of the ocean composition will only be through indirect physical measurements.”
As the authors write in their paper, “as exciting as these missions will be, they will only be able to access and interrogate the near surface … Our near-term ability to characterize the sub-surface ocean fluids will rely on their expression on the surface.”
Jeffrey Kargel, who is a senior associate research scientist at the University of Arizona in the United States, says that the paper could direct aspects of future research on Europa’s oceans, and “serves to keep attention focused on the fact that the composition of the surface and the ocean are likely linked.” However, he says that a major weak-ness in the research is that the authors did not include mixed salts, such as bloedite, which is a hydrated sodium magnesium sulfate mineral.
“We don’t know the temperature of the ocean, so we cannot conclude that the temperature rules out such salts,” Kargel says. Such salts provide a close match to the near-infrared spectra recorded during the Galileo mission, according to research published in 1999.
In the paper, the authors acknowledge that their research only examines a few possible ions. Choukroun says that, “Depending on future results of geochemical models applied to Europa, we will refine this list of species that are predicted to be both somewhat abundant and important for biology.”
The study, “Insights into Europa’s ocean composition derived from its surface expression,” was published in the journal Icarus. The work was supported in part through the NASA Astrobiology Institute (NAI) element of the NASA Astrobiology Program. | 0.855156 | 3.927643 |
The French mathematical astronomer Urbain Jean Joseph Leverrier (1811-1877) made theoretical investigations which led to the discovery of the planet Neptune.
Born at Saint-Lô in Normandy on March 11, 1811, U. J. J. Leverrier entered the highly competitive école Polytechnique to prepare for a career as a professional scientist. His early interest was in chemistry; but when the teaching post in astronomy fell vacant at the Polytechnique in 1837, Leverrier took it and thereby entered the discipline in which he was to spend the rest of his life.
The aspect of astronomy with which Leverrier was primarily concerned was celestial mechanics, the mathematical analysis of the planetary motions. According to the principles of celestial mechanics, each planet was supposed to move around the sun in an essentially elliptical orbit with minor deviations due to attractions by the rest of the planets. The computations involved were very complicated, but the results were generally sufficient to provide predictions of considerable accuracy. There was, however, one prominent exception—the planet Uranus. Although it had been the subject of a great deal of study since its discovery in 1781, attempts to reduce its motion to rule had yet to meet with complete success. The remaining error was small by ordinary standards (1 minute of arc, or the angle subtended by a nickel at a distance of 100 yards), but it was a scandal in a profession accustomed to accounting for angles less than one-tenth that size.
In 1845 Leverrier decided to look into the question. After concluding that the difficulty was probably due to the action of an unknown planet whose effects were not being taken into account, he undertook a series of detailed calculations which culminated in an estimation of the location of the unknown planet. On Sept. 23, 1846, the planet, later named Neptune at Leverrier's suggestion, was discovered by J. G. Galle, the director of the Berlin Observatory, less than a degree from the spot indicated by Leverrier.
Leverrier's work was universally acclaimed as one of the outstanding scientific achievements of all time, and he received honors from virtually every country and scientific society in Europe. He embarked on similar but less successful investigations of a slight anomaly in the motion of Mercury which was resolved only in the 20th century through the work of Albert Einstein. Leverrier continued with exhaustive examinations and revisions of all the existing planetary theories. In addition, he served with distinction as director of the Paris Observatory, organized the French meteorological service, and worked for the inclusion of scientific instruction in the French educational system. He died in Paris on Sept. 23, 1877.
Further Reading on Urbain Jean Joseph Leverrier
There is no biography of Leverrier, nor is there any thorough discussion of his technical contributions. Most of what has been written about him is in French; but Morton Grosser, The Discovery of Neptune (1962), presents a good account of Leverrier and one aspect of his work. | 0.853824 | 3.681299 |
Researchers from Rice University say that around 4.4 billion years ago, a Mercury-like planet smashed into Earth, seeding our primordial planet with life-giving carbon. Had this never occurred, it’s an open question as to whether or not life could have ever emerged.
Geoscientists have struggled to explain how life was able to arise on Earth given that most of the planet’s carbon—an important prerequisite for life—should have either boiled away during the planet’s earliest stages or become trapped within the Earth’s core. By conducting high-pressure and high-temperature experiments in the lab, researchers from Rice University have concluded that virtually all of our planet’s carbon likely arrived when a Mercury-like planet smashed into the young Earth some 4.4 billion years ago.
Scientists aren’t entirely sure how Earth’s volatile elements, such as carbon, hydrogen, nitrogen, and sulfur, were able to remain outside the Earth’s core and stay locked within the mantle. Models show that most of our planet’s carbon should have vaporized into space, or ended up in the metallic core of our planet, sucked up by its iron-rich alloys.
Prior to the new study, many scientists speculated that these volatile elements came to Earth after our planet’s core finished forming. As Rice University geoscientist and study co-author Yuan Li pointed out in a statement, “Any of those elements that fell to Earth in meteorites and comets more than about 100 million years after the solar system formed could have avoided the intense heat of the magma ocean that covered Earth up to that point.” Trouble is, there are no known meteorites capable of producing the required ratio of volatile elements.
Three years ago, Li and his colleagues began to take a different approach to the problem. They conducted a series of experiments to assess how carbon’s affinity for iron may have been altered by other compounds present in the Earth’s early environment. Importantly, they considered the potential role of other celestial bodies with characteristically different chemical compositions.
“We thought we definitely needed to break away from the conventional core composition of just iron and nickel and carbon,” noted study co-author Rajdeep Dasgupta. “So we began exploring very sulfur-rich and silicon-rich alloys, in part because the core of Mars is thought to be sulfur-rich and the core of Mercury is thought to be relatively silicon-rich.”
Their experiments recreated the high-pressure and high-temperature conditions found deep inside the Earth and other rocky planets. Results showed that carbon could be excluded from the core and relegated to the Earth’s mantle, provided that the iron alloys in the core were rich in either silicon or sulfur. One scenario that explains this particular ratio is that an embryonic planet—one that already formed a silicon-rich core—slammed into Earth, and was absorbed by Earth.
“Because it’s a massive body, the dynamics could work in a way that the core of that planet would go directly to the core of our planet, and the carbon-rich mantle would mix with Earth’s mantle,” said Gupta.
The researchers say this collision likely happened about 4.4 billion years ago, which is only about 150 to 200 million years after the Earth formed. With carbon locked within the crust, and with the planet settling down to produce habitable conditions, life soon emerged. Indeed, the most recent estimates suggest that microbial life formed approximately 4.1 billion years ago.
It’s important to point out that evidence for this primordial collision is circumstantial as best. The researchers agree that more work is needed to support this theory, including analyses of abundant elements other than carbon. If true, however, it could mean that Earth only became a habitable oasis only after this tremendous cosmic smashup. Carbon forms a key component of all known life on Earth; complex molecules are comprised of carbon bonded with other elements, such as oxygen, hydrogen, and nitrogen.
Regardless, the theory makes you wonder about life on other planets, and how specific the conditions need to be for life to finally emerge on dead, rocky worlds. | 0.83716 | 3.780874 |
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2014 November 17
Explanation: What do other star systems look like? To help find out, astronomers are carrying out detailed observations of nearby stars in infrared light to see which have dust disks that might be forming planets. Observations by NASA's Spitzer Space Telescope and ESA's Herschel Space Observatory have found that planetary system HD 95086 has two dust disks: a hot one near the parent star and a cooler one farther out. An artist's illustration of how the system might appear is featured here, including hypothetical planets with large rings that orbit between the disks. The planets may have created the large gap between the disks by absorbing and deflecting dust with their gravity. HD 95086 is a blue star about 60 percent more massive than our Sun that lies about 300 light years from Earth and is visible with binoculars toward the constellation of Carina. Studying the HD 95086 system may help astronomers better understand the formation and evolution of our own Solar System as well as the Earth.
Authors & editors:
Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
A service of: ASD at NASA / GSFC
& Michigan Tech. U. | 0.916057 | 3.120901 |
Asteroid Icarus will safely pass by Earth at more than 21 times the distance of Earth to the moon on June 16. To put it another way, Icarus, one of the first near-Earth asteroids ever discovered (1949), will approach no closer than five million miles away (eight million kilometers). On June 14, 2090, the asteroid will approach marginally closer, with a close approach distance of about 17 lunar distances (four million miles, or six-and-a-half million kilometers).
Discovered back in 1949 using photographic plates on the 48-inch Schmidt telescope at Mount Palomar near San Diego, Icarus was one of early near-Earth asteroids. It has an eccentric orbit that takes it very close to the sun, only 17 million miles (27 million kilometers) above the sun's surface. That's less than half the distance of Mercury's average distance to the sun. The asteroid was appropriately named after the mythical boy whose wax wings melted when he flew too close to the sun. For many decades, Icarus held the record for the closest known sun-approaching asteroid, but we now know of many other asteroids that approach even closer.
In its current orbit, Icarus can approach to within about 4 million miles (6.5 million kilometers) to Earth, which means it's categorized as a potentially hazardous asteroid (PHA). Tuesday's flyby of about 5 million miles (8 million kilometers) is the closest Icarus has approached since 1968. That close encounter was noteworthy because it was the first time an asteroid was observed by radar. Icarus will be extensively observed by radar on this year's passage, and we may even obtain the first-ever images of this famous object.
NASA detects, tracks and characterizes asteroids and comets using both ground- and space-based telescopes. Elements of the Near-Earth Object Program, often referred to as "Spaceguard," discover these objects, characterize a subset of them and identify their close approaches to determine if any could be potentially hazardous to our planet. NASA's Near-Earth Object Program is part of the agency's asteroid initiative, which includes sending a robotic spacecraft to capture a boulder from the surface of a near-Earth asteroid and move it into a stable orbit around the moon for exploration by astronauts, all in support of advancing the nation's journey to Mars.
JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena.
More information about asteroids and near-Earth objects is at:
To get updates on passing space rocks, follow:
News Media ContactDC Agle
Jet Propulsion Laboratory, Pasadena, Calif.
NASA Headquarters, Washington | 0.807468 | 3.696761 |
The reason for why this new proposed discovery has not made headlines (my personal conjecture), must be related to minimize a hysteria reaction from the “Planet-X” community – and I would side for such reason having witnessed this wild unfounded speculation in the past. However, for such a proposed finding to go “undetected” until now is a bit unsettling.
It is still unclear to this writer, if this finding is separate from Caltec’s assertion earlier this year. I would suggest it is the same – but provides further evidence towards confirmation. The assertion is the 9th Planet was orbiting another star and then was captured by our Sun during the time of its stellar cluster breakout – which basically suggests the 9th Planet has been in orbit from the time of our solar systems creation.
Before I go into this just published claim, let me layout the strict criteria a researcher must meet to assert that of a 9th planet in our solar system. a) The encounter must be more distant than ∼150 AU to avoid perturbing the Kuiper belt. b) The other star must have a wide-orbit planet – a ≳ 100 au c) the planet must be captured onto an appropriate orbit to sculpt the orbital distribution of wide-orbit Solar System bodies.
Astronomers at the University of Lund show a computer simulation study of the so-called 9th Planet meets a high probability of sustaining an orbit in our solar system. Alexander Mustill, astronomer at the University of Lund, says “It is most ironic that while astronomers often find extrasolar planets hundreds of light years away in other solar systems, this one had been hiding in our own backyard”.
An extrasolar plane (exoplanet) has by definition been a planet located outside our own solar system. Now it seems the definition is not viable anymore. According to astronomers in Lund, indications show a 9th Planet was captured by our young Sun, has gone undetected until now, and is part of our solar system.
Stars are born in clusters often pass in very close proximity. It is in these meetings that a star can capture one or more planets in orbit around another star. This is probably what happened when our own Sun caught the 9th Planet.
Science of Cycles w/ Mitch Battros News Service Update
As with all coming summer time seasons, donations have almost come to a complete halt – however, the news of scientific breakthroughs with amazing findings are coming as rapidly as ever.
I have almost completely diminished out-of-pocket cost to keep this unique news service running and available to all. Your support is the lifeline of our services and we need you now more than just about any other time in our 21-year history. I know times are tough for almost everyone in the community, with no exception here. For those that can please consider a sponsorship with a monthly or annual commitment. And for those with ever tightening budgets, your donation of $5,10,20,50 will certainly help.
Go to the following link and submit your secure donations today. Unfortunately, time is not on our side, so please consider making your supportive effort at the speed of an X-15 solar flare.
For PayPal Sponsorship/Donation – Click on Banner or Click Here | 0.842892 | 3.163979 |
You could be forgiven for thinking this summer that the “supermoon” is now a monthly occurrence. But this coming weekend’s Full Moon is indeed (we swear) the closest to Earth for 2014.
What’s going on here? Well, as we wrote one synodic month ago — the time it takes for the Moon to return to the same phase at 29.5 days — we’re currently in a cycle of supermoons this summer. That is, a supermoon as reckoned as when the Full Moon falls within 24 hours of perigee, a much handier definition than the nebulous “falls within 90% of its orbit” proposed and popularized by astrologers.
The supermoons for 2014 fall on July 13th, August 10th and September 8th respectively. You could say that this weekend’s supermoon is act two in a three act movement, a sort of Empire Strikes Back to last month’s A New Hope.
Now for the specifics: Full Moon this weekend occurs on August 10th at 18:10 Universal Time (UT) or 2:10 PM EDT. The Moon will reach perigee or its closest point to the Earth at 17:44 UT/1:44 PM EDT just 26 minutes prior to Full, at 55.96 Earth radii distant or 356,896 kilometres away. This is just under 500 kilometres shy of the closest perigee that can occur at 356,400 kilometres distant. Perigee was closer to Full phase time-wise last year on June 23rd, 2013, but this value won’t be topped or tied again until November 25th, 2034. The Moon will be at the zenith and closest to the surface of the Earth at the moment it passes Full over the mid-Indian Ocean on Sunday evening nearing local midnight.
Now for a reality check: The August lunar perigee only beats out the January 1st approach of the Moon for the closest of 2014 by a scant 25 kilometres. Perigees routinely happen whether the Moon is Full or not, and they occur once every anomalistic month, which is the average span from perigee-to-perigee at 27.6 days. This difference between the anomalistic and synodic period causes the coincidence that is the supermoon to precess forward about a month a year. You can see our list of supermoon seasons out until 2020 here.
And don’t forget, the Moon actually approaches you to the tune of about half of the radius of the Earth while it rises to the zenith, only to recede again as it sinks back down to the horizon. The rising Full Moon on the horizon only appears larger mainly due to an illusion known as the Ponzo Effect.
The apparent size of the Moon varies about 14% in angular diameter from 29.3′ (known as an apogee “mini-Moon”) to 34.1′ at its most perigee “super-size” as seen from the Earth.
Astronomers prefer the use of the term Perigee Full Moon, but the supermoon meme has taken on a cyber-life of its own. Of course, we’ve gone on record before and stated that we prefer the more archaic term Proxigean Moon, but the supermoon seems here to stay.
And as with many Full Moon myths, this week’s supermoon will be implicated in everything from earthquakes to lost car keys to other terrestrial woes, though of course no such links exist. Coworkers/family members/strangers on Twitter will once again insist it was “the biggest ever,” and claim it took up “half the sky” as they unwittingly take part in an impromptu psychological perception test.
Fun fact: you could ring local the horizon with 633 supermoons!
And of course, many a website will recycle their supermoon posts, though of course not here at Universe Today, as we bake our science fresh daily.
So what can you expect? Well, a perigee Full Moon can make for higher than usual tides. New York City residents had the bad fortune of a Full Moon tidal surge in 2012 when Hurricane Sandy made landfall. Though there doesn’t seem to be a chance for a repeat of such an occurrence in 2014 in the Atlantic, super-typhoon Halong is churning towards the Japanese coastline for landfall this weekend…
Observationally, Full Moon is actually a lousy time for astronomical observations, causing many a deep sky astrophotographer to instead stay home and visit the family, while lurking astrophotography forums and debunking YouTube UFO videos.
Pro-tip: want your supermoon photo/video to go viral? Shoot the rising Moon just the evening prior when it’s waxing gibbous but nearly Full. Not only will it be more likely to be picked up while everyone is focused on supermoon lunacy, but you’ll also have the added bonus of catching the Moon silhouetted against a low-contrast dusk sky. We have a pre-supermoon rising video from a few years back that still trends with each synodic period!
Well, that’s it ‘til September, when it’ll be The Return (Revenge?) of the Supermoon. Be sure to send those pics in to Universe Today’s Flickr forum, you just might make the supermoon roundup! | 0.804749 | 3.295625 |
François Englert and Peter W. Higgs are jointly awarded the Nobel Prize in Physics 2013 “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron Collider”
François Englert and Peter W. Higgs are jointly awarded the Nobel Prize in Physics 2013 for the theory of how particles acquire mass. In 1964, they proposed the theory independently of each other (Englert together with his now deceased colleague Robert Brout). In 2012, their ideas were confirmed by the discovery of a so called Higgs particle at the CERN laboratory outside Geneva in Switzerland.
The awarded mechanism is a central part of the Standard Model of particle physics that describes how the world is constructed. According to the Standard Model, everything, from flowers and people to stars and planets, consists of just a few building blocks: matter particles. These particles are governed by forces mediated by force particles that make sure everything works as it should.
The entire Standard Model also rests on the existence of a special kind of particle: the Higgs particle. It is connected to an invisible field that fills up all space. Even when our universe seems empty, this field is there. Had it not been there, electrons and quarks would be massless just like photons, the light particles. And like photons they would, just as Einstein’s theory predicts, rush through space at the speed of light, without any possibility to get caught in atoms or molecules.
Nothing of what we know, not even we, would exist.
Both François Englert and Peter Higgs were young scientists when they, in 1964, independently of each other put forward a theory that rescued the Standard Model from collapse. Almost half a century later, on Wednesday 4 July 2012, they were both in the audience at the European Laboratory for Particle Physics, CERN, outside Geneva, when the discovery of a Higgs particle that finally confirmed the theory was announced to the world.
The model that created order
The idea that the world can be explained in terms of just a few building blocks is old. Already in 400 BC, the philosopher Democritus postulated that everything consists of atoms —átomos is Greek for indivisible.
Today we know that atoms are not indivisible. They consist of electrons that orbit an atomic
nucleus made up of neutrons and protons. And neutrons and protons, in turn, consist of smaller particles called quarks. Actually, only electrons and quarks are indivisible according to the Standard Model.
The atomic nucleus consists of two kinds of quarks, up quarks and down quarks. So in fact, three elementary particles are needed for all matter to exist: electrons, up quarks and down quarks. But during the 1950s and 1960s, new particles were unexpectedly observed in both cosmic radiation and at newly constructed accelerators, so the Standard Model had to include these new siblings of electrons and quarks.
Besides matter particles, there are also force particles for each of nature’s four forces — gravitation, electro magnetism, the weak force and the strong force. Gravitation and electromagnetism are the most well-known, they attract or repel, and we can see their effects with our own eyes. The strong force acts upon quarks and holds protons and neutrons together in the nucleus, whereas the weak force is responsible for radioactive decay, which is necessary, for instance, for nuclear processes inside the Sun.
The Standard Model of particle physics unites the fundamental building blocks of nature and three of the four forces known to us (the fourth, gravitation, remains outside the model). For long, it was an enigma how these forces actually work. For instance, how does the piece of metal that is attracted to the magnet know that the magnet is lying there, a bit further away? And how does the Moon feel the gravity of Earth?
Invisible fields fill space
The explanation offered by physics is that space is filled with many invisible fields. The gravitational field, the electromagnetic field, the quark field and all the other fields fill space, or rather, the four dimensional space-time, an abstract space where the theory plays out. The Standard Model is a quantum field theory in which fields and particles are the essential building blocks of the universe.
In quantum physics, everything is seen as a collection of vibrations in quantum fields. These vibrations are carried through the field in small packages, quanta, which appear to us as particles. Two kinds of fields exist: matter fields with matter particles, and force fields with force particles — the mediators of forces. The Higgs particle, too, is a vibration of its field — often referred to as the Higgs field.
Without this field the Standard Model would collapse like a house of cards, because quantum field theory brings infinities that have to be reined in and symmetries that cannot be seen. It was not until François Englert with Robert Brout, and Peter Higgs, and later on several others, showed that the Higgs field can break the symmetry of the Standard Model without destroying the theory that the model got accepted.
This is because the Standard Model would only work if particles did not have mass. As for the electromagnetic force, with its massless photons as mediators, there was no problem. The weak force, however, is mediated by three massive particles; two electrically charged W particles and one Z particle. They did not sit well with the light-footed photon. How could the electroweak force, which unifies electromagnetic and weak forces, come about? The Standard Model was threatened. This is where Englert, Brout and Higgs entered the stage with the ingenious mechanism for particles to acquire mass that managed to rescue the Standard Model.
The ghost-like Higgs field
The Higgs field is not like other fields in physics. All other fields vary in strength and become zero at their lowest energy level. Not the Higgs field. Even if space were to be emptied completely, it would still be filled by a ghost-like field that refuses to shut down: the Higgs field. We do not notice it; the Higgs field is like air to us, like water to fish. But without it we would not exist, because particles acquire mass only in contact with the Higgs field. Particles that do not pay attention to the Higgs field do not acquire mass, those that interact weakly become light, and those that interact intensely become heavy. For example, electrons, which acquire mass from the field, play a crucial role in the creation and holding together of atoms and molecules. If the Higgs field suddenly disappeared, all matter would collapse as the suddenly massless electrons dispersed at the speed of light.
So what makes the Higgs field so special? It breaks the intrinsic symmetry of the world. In nature, symmetry abounds; faces are regularly shaped, flowers and snowflakes exhibit various kinds of geometric symmetries. Physics unveils other kinds of symmetries that describe our world, albeit on a deeper level. One such, relatively simple, symmetry stipulates that it does not matter for the results if a laboratory experiment is carried out in Stockholm or in Paris. Neither does it matter at what time the experiment is carried out. Einstein’s special theory of relativity deals with symmetries in space and time, and has become a model for many other theories, such as the Standard Model of particle physics. The equations of the Standard Model are symmetric; in the same way that a ball looks the same from whatever angle you look at it, the equations of the Standard Model remain unchanged even if the perspective that defines them is changed.
The principles of symmetry also yield other, somewhat unexpected, results. Already in 1918, the
German mathematician Emmy Noether could show that the conservation laws of physics, such as the laws of conservation of energy and conservation of electrical charge, also originate in symmetry.
Symmetry, however, dictates certain requirements to be fulfilled. A ball has to be perfectly round; the tiniest hump will break the symmetry. For equations other criteria apply. And one of the symmetries of the Standard Model prohibits particles from having mass. Now, this is apparently not the case in our world, so the particles must have acquired their mass from somewhere. This is where the now-awarded mechanism provided a way for symmetry to both exist and simultaneously be hidden from view.
The symmetry is hidden but is still there
Our universe was probably born symmetrical. At the time of the Big Bang, all particles were massless and all forces were united in a single primordial force. This original order does not exist anymore — its symmetry has been hidden from us. Something happened just 10–11 seconds after the Big Bang. The Higgs field lost its original equilibrium. How did that happen?
It all began symmetrically. This state can be described as the position of a ball in the middle of a round bowl, in its lowest energy state. With a push the ball starts rolling, but after a while it returns down to the lowest point.
However, if a hump arises at the centre of the bowl, which now looks more like a Mexican hat, the position at the middle will still be symmetrical but has also become unstable. The ball rolls downhill in any direction. The hat is still symmetrical, but once the ball has rolled down, its position away from the centre hides the symmetry. In a similar manner the Higgs field broke its symmetry and found a stable energy level in vacuum away from the symmetrical zero posi tion. This spontaneous symmetry breaking is also referred to as the Higgs field’s phase transition; it is like when water freezes to ice.
In order for the phase transition to occur, four particles were required but only one, the Higgs particle, survived. The other three were consumed by the weak force mediators, two electrically charged W particles and one Z particle, which thereby got their mass. In that way the symmetry of the electroweak force in the Standard Model was saved — the symmetry between the three heavy particles of the weak force and the massless photon of the electromagnetic force remains, only hidden from view.
Extreme machines for extreme physics
The Nobel Laureates probably did not imagine that they would get to see the theory confirmed in their lifetime. It took an enormous effort by physicists from all over the world. For a long time two laboratories, Fermilab outside Chicago, USA, and CERN on the Franco-Swiss border, competed in trying to discover the Higgs particle. But when Fermilab’s Tevatron accelerator was closed down a couple of years ago, CERN became the only place in the world where the hunt for the Higgs particle would continue.
CERN was established in 1954, in an attempt to reconstruct European research, as well as relations between European countries, after the Second World War. Its membership currently comprises twenty states, and about a hundred nations from all over the world collaborate on the projects.
CERN’s grandest achievement, the particle collider LHC (Large Hadron Collider) is probably the largest and the most complex machine ever constructed by humans. Two research groups of some 3,000 scientists chase particles with huge detectors — ATLAS and CMS. The detectors are located 100 metres below ground and can observe 40 million particle collisions per second. This is how often the particles can collide when injected in opposite directions into the circular LHC tunnel, 27 kilometres long.
Protons are injected into the LHC every ten hours, one ray in each direction. A hundred thousand billion protons are lumped together and compressed into an ultra-thin ray — not entirely an easy endeavour since protons with their positive electrical charge rather aim to repel one another. They move at 99.99999 per cent of the speed of light and collide with an energy of approximately 4 TeV each and 8 TeV combined (one teraelectronvolt = a thousand billion electronvolts). One TeV may not be that much energy, it more or less equals that of a flying mosquito, but when the energy is packed into a single proton, and you get 500 trillion such protons rushing around the accelerator, the energy of the ray equals that of a train at full speed. In 2015 the energy will be almost the double in the LHC.
A puzzle inside the puzzle
Particle experiments are sometimes compared to the act of smashing two Swiss watches together in order to examine how they are constructed. But it is actually much more difficult than so, because the particles scientists look for are entirely new — they are created from the energy released in the collision.
According to Einstein’s well-known formula E = mc2, mass is a kind of energy. And it is the magic of this equation that makes it possible, even for massless particles, to create something new when they collide; like when two photons collide and create an electron and its antiparticle, the positron, or when a Higgs particle is created in the collision of two gluons, if the energy is high enough.
The protons are like small bags filled with particles — quarks, antiquarks and gluons. The majority of them pass one another without much ado; on average, each time two particle swarms collide only twenty full frontal collisions occur. Less than one collision in a billion might be worth following through. This may not sound much, but each such collision results in a sparkling explosion of about a thousand particles. At 125 GeV, the Higgs particle turned out to be over a hundred times heavier than a proton and this is one of the reasons why it was so difficult to produce.
However, the experiment is far from finished. The scientists at CERN hope to bring further ground breaking discoveries in the years to come. Even though it is a great achievement to have found the Higgs particle — the missing piece in the Standard Model puzzle — the Standard Model is not the final piece in the cosmic puzzle.
One of the reasons for this is that the Standard Model treats certain particles, neutrinos, as being vir tually massless, whereas recent studies show that they actually do have mass. Another reason is that the model only describes visible matter, which only accounts for one fifth of all matter in the universe.
The rest is dark matter of an unknown kind. It is not immediately apparent to us, but can be observed by its gravitational pull that keeps galaxies together and prevents them from being torn apart.
In all other respects, dark matter avoids getting involved with visible matter. Mind you, the Higgs
particle is special; maybe it could manage to establish contact with the enigmatic darkness. Scientists hope to be able to catch, if only a glimpse, of dark matter, as they continue the chase of unknown particles in the LHC in the coming decades. | 0.818977 | 3.828758 |
The International Astronomical Union – Without dark skies, astronomers are unable to receive the faint signals of light from distant objects in outer space. Dark skies are a critical scientific resource for understanding the mysteries of the universe. Dark skies are also an important part of the cultural and natural heritage of all civilizations.
Many astronomical observatories are built in remote locations in an effort to escape the light of cities and towns. Even so, these observatories are threatened by light pollution such as city lights encroaching upon the mountaintop of Mauna Kea, Hawaii. Mauna Kea Observatories is one of the best astronomical sites in the world. Lighting ordinances are an important tool to protect these sites from light pollution.
Bandar Seri Begawan – Tonight’s full moon was a Supermoon which is astronomically known as the perigee-syzygy. It occurs when the full moon is directly opposite the sun and at the closest juncture (perigee) to earth in its orbit.
Tonight’s full moon was the final Supermoon in 2020, and the next occurrence is on Tuesday, April 27, 2021 at 11:31 am. (Find out when is the next Supermoon from 2020 until 2030 here)
Here are some of tonight’s best supermoon snapshots from around Brunei Darussalam.
UPDATE (Thursday, 07 May 2020): A possible naked-eye outburst of Comet SWAN! Despite of bright moonlight and thin clouds, Comet C/2020 F8 (SWAN) is still visible from Brunei just before nautical twilight today, May 07, 2020 at 0520. The greenish coma is due to molecules of Cyanogen and Carbon gas ejected from the comet nucleus. In the following days, the comet is located very low on the Eastern horizon in early morning twilight, before it fades in full daylight next week.
Another comet observer, Abdul Waliyuddin, a member of Brunei Darussalam Astronomical Society (PABD), managed to capture the beautiful Comet Swan as it makes its way through our solar system. Waliyuddin said “The pre-dawn skies of Seria gave way to a clear view of the celestial ceiling this morning. It was spewing a tail of gas and dust that can extend up to hundreds of millions of kilometres away from its epicenter from Seria, Belait, Brunei Darussalam”
Comet SWAN was only discovered two months ago. There is much to be understood and learned from our skies. Whatever science tells us about the biology of our fingers will always be lesser than the true reality of the wonders of our finger. Likewise, whatever we know about our skies will always be lesser than the actual existential reality of the grandeur of space.
The sighting of the new moon is a particular subject in astronomy that has fascinated many observers since prehistory. Evidence of early human civilizations using the moon as a basis to measure time in the form of an actual lunar calendar has been discovered in the ancient plains of Scotland, dating back to 8,000 B.C. Professor Samuel L. Macey of the International Society for the Study of Time in his book, Encyclopedia of Time, says that using the moon to measure the passage of seasons was evident as far back as 28,000-30,000 thousand years. Therefore, the method by which we measure the beginning and the end of the new moon phase is indeed a crucial part of determining the accuracy of any lunar calendar.
Since the Islamic months follow a lunar calendar, the start of each month is marked by the first sighting of the crescent moon. It is important to note however, that the Islamic new moon is actually different to the “astronomical new moon”. We define the astronomical new moon as that point when it is in conjunction with the sun, and thus it is actually too close to the sun and is very dark, for most of the lunar disc is in shadow. This point marks the beginning of measurement for the true age of the moon.
By Hazarry bin Haji Ali Ahmad The Astronomical Society of Brunei Darussalam
Bandar Seri Begawan – A perfect alignment of the 3 celestial bodies, Earth-Moon-Sun, will occur on Sunday June 21, 2020, resulting in a spectacular annular solar eclipse which can only be view from specific areas on Earth.
The annular phase of this solar eclipse will be visible from parts of Africa including the Central African Republic, Congo, and Ethiopia; Asia in Yemen, Oman, south of Pakistan and northern India, China including Taiwan. You must be located within the narrow path of annularity represented on the map above by a red line (about 11,400 km long and 21 km width), where people in these areas will see the characteristic “ring of fire”.
Terkini (22 April 2020) – Komet Atlas yang pada mulanya menjadi sangat terang setelah baru 4 bulan ditemui kini telah hancur berkecai. Itulah sifat komet yang sukar untuk diramalkan, jadi ia tidak mengejutkan bahawa komet itu berpecah. Komet tersebut telah menjadi serpihan yang lebih kecil sehingga ia menjadi mustahil untuk melihatnya.
A large green meteor streaked through the sky over Brunei Darussalam last Sunday, with many excited observers taking to social media to discuss the natural phenomenon. The passing meteor was photographed at 7.27pm by Mohammad Nazhif bin Haji Abdul Khalid, who was taking pictures of the planet Venus in the clear sky at his home in Kampong Lambak.
He recalled, “At first, I thought that it was a fireworks display, but there were no exploding sounds.” | 0.89325 | 3.265182 |
A non-standard cosmology is any physical cosmological model of the universe that was, or still is, proposed as an alternative to the then-current standard model of cosmology. The term non-standard is applied to any theory that does not conform to the scientific consensus. Because the term depends on the prevailing consensus, the meaning of the term changes over time. For example, hot dark matter would not have been considered non-standard in 1990, but would be in 2010. Conversely, a non-zero cosmological constant resulting in an accelerating universe would have been considered non-standard in 1990, but is part of the standard cosmology in 2010.
Several major cosmological disputes have occurred throughout the history of cosmology. One of the earliest was the Copernican Revolution, which established the heliocentric model of the Solar System. More recent was the Great Debate of 1920, in the aftermath of which the Milky Way's status as but one of the Universe's many galaxies was established. From the 1940s to the 1960s, the astrophysical community was equally divided between supporters of the Big Bang theory and supporters of a rival steady state universe; this was eventually decided in favour of the Big Bang theory by advances in observational cosmology in the late 1960s. The current standard model of cosmology is the Lambda-CDM model, wherein the Universe is governed by General Relativity, began with a Big Bang and today is a nearly-flat universe that consists of approximately 5% baryons, 27% cold dark matter, and 68% dark energy.
Lambda-CDM has been an extremely successful model, but retains some weaknesses (such as the dwarf galaxy problem). Research on extensions or modifications to Lambda-CDM, as well as fundamentally different models, is ongoing. Topics investigated include quintessence, Modified Newtonian Dynamics (MOND) and its relativistic generalization TeVeS, and warm dark matter.
The Lambda-CDM modelEdit
Before observational evidence was gathered, theorists developed frameworks based on what they understood to be the most general features of physics and philosophical assumptions about the universe. When Albert Einstein developed his general theory of relativity in 1915, this was used as a mathematical starting point for most cosmological theories. In order to arrive at a cosmological model, however, theoreticians needed to make assumptions about the nature of the largest scales of the universe. The assumptions that the current standard model of cosmology, Lambda-CDM, relies upon are:
- the universality of physical laws – that the laws of physics don't change from one place and time to another,
- the cosmological principle – that the universe is roughly homogeneous and isotropic in space though not necessarily in time, and
- the Copernican principle – that we are not observing the universe from a preferred locale.
These assumptions when combined with General Relativity result in a universe that is governed by the Friedmann–Robertson–Walker metric (FRW metric). The FRW metric allows for a universe that is either expanding or contracting (as well as stationary but unstable universes). When Hubble's Law was discovered, most astronomers interpreted the law as a sign the universe is expanding. This implies the universe was smaller in the past, and therefore led to the following conclusions:
- the universe emerged from a hot, dense state at a finite time in the past,
- because the universe heats up as it contracts and cools as it expands, in the first moments that time existed as we know it, the temperatures were high enough for Big Bang nucleosynthesis to occur, and
- a cosmic microwave background pervading the entire universe should exist, which is a record of a phase transition that occurred when the atoms of the universe first formed.
These features were derived by numerous individuals over a period of years; indeed it was not until the middle of the twentieth century that accurate predictions of the last feature and observations confirming its existence were made. Non-standard theories developed either by starting from different assumptions or by contradicting the features predicted by Lambda-CDM.
Modern physical cosmology as it is currently studied first emerged as a scientific discipline in the period after the Shapley–Curtis debate and discoveries by Edwin Hubble of a cosmic distance ladder when astronomers and physicists had to come to terms with a universe that was of a much larger scale than the previously assumed galactic size. Theorists who successfully developed cosmologies applicable to the larger-scale universe are remembered today as the founders of modern cosmology. Among these scientists are Arthur Milne, Willem de Sitter, Alexander Friedman, Georges Lemaître, and Albert Einstein himself.
After confirmation of the Hubble's law by observation, the two most popular cosmological theories became the Steady State theory of Hoyle, Gold and Bondi, and the big bang theory of Ralph Alpher, George Gamow, and Robert Dicke with a small number of supporters of a smattering of alternatives. Since the discovery of the Cosmic microwave background radiation (CMB) by Arno Penzias and Robert Wilson in 1965, most cosmologists concluded that observations were best explained by the big bang model. Steady State theorists and other non-standard cosmologies were then tasked with providing an explanation for the phenomenon if they were to remain plausible. This led to original approaches including integrated starlight and cosmic iron whiskers, which were meant to provide a source for a pervasive, all-sky microwave background that was not due to an early universe phase transition.
Scepticism about the non-standard cosmologies' ability to explain the CMB caused interest in the subject to wane since then, however, there have been two periods in which interest in non-standard cosmology has increased due to observational data which posed difficulties for the big bang. The first occurred was the late 1970s when there were a number of unsolved problems, such as the horizon problem, the flatness problem, and the lack of magnetic monopoles, which challenged the big bang model. These issues were eventually resolved by cosmic inflation in the 1980s. This idea subsequently became part of the understanding of the big bang, although alternatives have been proposed from time to time. The second occurred in the mid-1990s when observations of the ages of globular clusters and the primordial helium abundance, apparently disagreed with the big bang. However, by the late 1990s, most astronomers had concluded that these observations did not challenge the big bang and additional data from COBE and the WMAP, provided detailed quantitative measures which were consistent with standard cosmology.
In the 1990s, a dawning of a "golden age of cosmology" was accompanied by a startling discovery that the expansion of the universe was, in fact, accelerating. Previous to this, it had been assumed that matter either in its visible or invisible dark matter form was the dominant energy density in the universe. This "classical" big bang cosmology was overthrown when it was discovered that nearly 70% of the energy in the universe was attributable to the cosmological constant, often referred to as "dark energy". This has led to the development of a so-called concordance ΛCDM model which combines detailed data obtained with new telescopes and techniques in observational astrophysics with an expanding, density-changing universe. Today, it is more common to find in the scientific literature proposals for "non-standard cosmologies" that actually accept the basic tenets of the big bang cosmology, while modifying parts of the concordance model. Such theories include alternative models of dark energy, such as quintessence, phantom energy and some ideas in brane cosmology; alternative models of dark matter, such as modified Newtonian dynamics; alternatives or extensions to inflation such as chaotic inflation and the ekpyrotic model; and proposals to supplement the universe with a first cause, such as the Hartle–Hawking boundary condition, the cyclic model, and the string landscape. There is no consensus about these ideas amongst cosmologists, but they are nonetheless active fields of academic inquiry.
Today, heterodox non-standard cosmologies are generally considered unworthy of consideration by cosmologists while many of the historically significant nonstandard cosmologies are considered to have been falsified. The essentials of the big bang theory have been confirmed by a wide range of complementary and detailed observations, and no non-standard cosmologies have reproduced the range of successes of the big bang model. Speculations about alternatives are not normally part of research or pedagogical discussions, except as object lessons or for their historical importance. An open letter started by some remaining advocates of non-standard cosmology has affirmed that: "today, virtually all financial and experimental resources in cosmology are devoted to big bang studies...."
General relativity, upon which the FRW metric is based, is an extremely successful theory which has met every observational test so far. However, at a fundamental level it is incompatible with quantum mechanics, and by predicting singularities, it also predicts its own breakdown. Any alternative theory of gravity would imply immediately an alternative cosmological theory since current modeling is dependent on general relativity as a framework assumption. There are many different motivations to modify general relativity, such as to eliminate the need for dark matter or dark energy, or to avoid such paradoxes as the firewall.
Ernst Mach developed a kind of extension to general relativity which proposed that inertia was due to gravitational effects of the mass distribution of the universe. This led naturally to speculation about the cosmological implications for such a proposal. Carl Brans and Robert Dicke were able to successfully incorporate Mach's principle into general relativity which admitted for cosmological solutions that would imply a variable mass. The homogeneously distributed mass of the universe would result in a roughly scalar field that permeated the universe and would serve as a source for Newton's gravitational constant; creating a theory of quantum gravity.
Modified Newtonian Dynamics (MOND) is a relatively modern proposal to explain the galaxy rotation problem based on a variation of Newton's Second Law of Dynamics at low accelerations. This would produce a large-scale variation of Newton's universal theory of gravity. A modification of Newton's theory would also imply a modification of general relativistic cosmology in as much as Newtonian cosmology is the limit of Friedman cosmology. While almost all astrophysicists today reject MOND in favor of dark matter, a small number of researchers continue to enhance it, recently incorporating Brans–Dicke theories into treatments that attempt to account for cosmological observations.
Tensor–vector–scalar gravity (TeVeS) is a proposed relativistic theory that is equivalent to Modified Newtonian dynamics (MOND) in the non-relativistic limit, which purports to explain the galaxy rotation problem without invoking dark matter. Originated by Jacob Bekenstein in 2004, it incorporates various dynamical and non-dynamical tensor fields, vector fields and scalar fields.
The break-through of TeVeS over MOND is that it can explain the phenomenon of gravitational lensing, a cosmic optical illusion in which matter bends light, which has been confirmed many times. A recent preliminary finding is that it can explain structure formation without CDM, but requiring a ~2eV massive neutrino (they are also required to fit some Clusters of galaxies, including the Bullet Cluster). However, other authors (see Slosar, Melchiorri and Silk) claim that TeVeS can't explain cosmic microwave background anisotropies and structure formation at the same time, i.e. ruling out those models at high significance.
f(R) gravity is a family of theories that modify general relativity by defining a different function of the Ricci scalar. The simplest case is just the function being equal to the scalar; this is general relativity. As a consequence of introducing an arbitrary function, there may be freedom to explain the accelerated expansion and structure formation of the Universe without adding unknown forms of dark energy or dark matter. Some functional forms may be inspired by corrections arising from a quantum theory of gravity. f(R) gravity was first proposed in 1970 by Hans Adolph Buchdahl (although φ was used rather than f for the name of the arbitrary function). It has become an active field of research following work by Starobinsky on cosmic inflation. A wide range of phenomena can be produced from this theory by adopting different functions; however, many functional forms can now be ruled out on observational grounds, or because of pathological theoretical problems.
Steady State theoriesEdit
The Steady State theory extends the homogeneity assumption of the cosmological principle to reflect a homogeneity in time as well as in space. This "perfect cosmological principle" as it would come to be called asserted that the universe looks the same everywhere (on the large scale), the same as it always has and always will. This is in contrast to Lambda-CDM, in which the universe looked very different in the past and will look very different in the future. Steady State theory was proposed in 1948 by Fred Hoyle, Thomas Gold, Hermann Bondi and others. In order to maintain the perfect cosmological principle in an expanding universe, steady state cosmology had to posit a "matter-creation field" (the so-called C-field) that would insert matter into the universe in order to maintain a constant density.
The debate between the Big Bang and the Steady State models would happen for 15 years with camps roughly evenly divided until the discovery of the cosmic microwave background radiation. This radiation is a natural feature of the Big Bang model which demands a "time of last scattering" where photons decouple with baryonic matter. The Steady State model proposed that this radiation could be accounted for by so-called "integrated starlight" which was a background caused in part by Olbers' paradox in an infinite universe. In order to account for the uniformity of the background, steady state proponents posited a fog effect associated with microscopic iron particles that would scatter radio waves in such a manner as to produce an isotropic CMB. The proposed phenomena was whimsically named "cosmic iron whiskers" and served as the thermalization mechanism. The Steady State theory did not have the horizon problem of the Big Bang because it assumed an infinite amount of time was available for thermalizing the background.
As more cosmological data began to be collected, cosmologists began to realize that the Big Bang correctly predicted the abundance of light elements observed in the cosmos. What was a coincidental ratio of hydrogen to deuterium and helium in the steady state model was a feature of the Big Bang model. Additionally, detailed measurements of the CMB since the 1990s with the COBE, WMAP and Planck observations indicated that the spectrum of the background was closer to a blackbody than any other source in nature. The best integrated starlight models could predict was a thermalization to the level of 10% while the COBE satellite measured the deviation at one part in 105. After this dramatic discovery, the majority of cosmologists became convinced that the steady state theory could not explain the observed CMB properties.
Although the original steady state model is now considered to be contrary to observations (particularly the CMB) even by its one-time supporters, modifications of the steady state model has been proposed, including a model that envisions the universe as originating through many little bangs rather than one big bang (the so-called "quasi-steady state cosmology"). It supposes that the universe goes through periodic expansion and contraction phases, with a soft "rebound" in place of the Big Bang. Thus the Hubble Law is explained by the fact that the universe is currently in an expansion phase. Work continues on this model (most notably by Jayant V. Narlikar), although it has not gained widespread mainstream acceptance.
Isotropicity – the idea that the universe looks the same in all directions – is one of the core assumptions that enters into the FRW equations. In 2008 however, scientists working on Wilkinson Microwave Anisotropy Probe data claimed to have detected a 600–1000 km/s flow of clusters toward a 20-degree patch of sky between the constellations of Centaurus and Vela. They suggested that the motion may be a remnant of the influence of no-longer-visible regions of the universe prior to inflation. The detection is controversial, and other scientists have found that the universe is isotropic to a great degree.
Exotic dark matter and dark energyEdit
In Lambda-CDM, dark matter is an extremely inert form of matter that does not interact with both ordinary matter (baryons) and light, but still exerts gravitational effects. To produce the large-scale structure we see today, dark matter is "cold" (the 'C' in Lambda-CDM), i.e. non-relativistic. Dark energy is an unknown form of energy that tends to accelerate the expansion of the universe. Both dark matter and dark energy have not been conclusively identified, and their exact nature is the subject of intense study. For example, scientists have hypothesized that dark matter could decay into dark energy, or that both dark matter and dark energy are different facets of the same underlying fluid (see dark fluid). Other theories that aim to explain one or the other, such as warm dark matter and quintessence, also fall into this category.
Proposals based on observational skepticismEdit
As the observational cosmology began to develop, certain astronomers began to offer alternative speculations regarding the interpretation of various phenomena that occasionally became parts of non-standard cosmologies.
Tired light theories challenge the common interpretation of Hubble's Law as a sign the universe is expanding. It was proposed by Fritz Zwicky in 1929. The basic proposal amounted to light losing energy ("getting tired") due to the distance it traveled rather than any metric expansion or physical recession of sources from observers. A traditional explanation of this effect was to attribute a dynamical friction to photons; the photons' gravitational interactions with stars and other material will progressively reduce their momentum, thus producing a redshift. Other proposals for explaining how photons could lose energy included the scattering of light by intervening material in a process similar to observed interstellar reddening. However, all these processes would also tend to blur images of distant objects, and no such blurring has been detected.
Traditional tired light has been found incompatible with the observed time dilation that is associated with the cosmological redshift. This idea is mostly remembered as a falsified alternative explanation for Hubble's law in most astronomy or cosmology discussions.
Dirac large numbers hypothesisEdit
The Dirac large numbers hypothesis uses the ratio of the size of the visible universe to the radius of quantum particle to predict the age of the universe. The coincidence of various ratios being close in order of magnitude may ultimately prove meaningless or the indication of a deeper connection between concepts in a future theory of everything. Nevertheless, attempts to use such ideas have been criticized as numerology.
Redshift periodicity and intrinsic redshiftsEdit
Some astrophysicists were unconvinced that the cosmological redshifts are caused by universal cosmological expansion. Skepticism and alternative explanations began appearing in the scientific literature in the 1960s. In particular, Geoffrey Burbidge, William Tifft and Halton Arp were all observational astrophysicists who proposed that there were inconsistencies in the redshift observations of galaxies and quasars. The first two were famous for suggesting that there were periodicities in the redshift distributions of galaxies and quasars. Subsequent statistical analyses of redshift surveys, however, have not confirmed the existence of these periodicities.
During the quasar controversies of the 1970s, these same astronomers were also of the opinion that quasars exhibited high redshifts not due to their incredible distance but rather due to unexplained intrinsic redshift mechanisms that would cause the periodicities and cast doubt on the Big Bang. Arguments over how distant quasars were took the form of debates surrounding quasar energy production mechanisms, their light curves, and whether quasars exhibited any proper motion. Astronomers who believed quasars were not at cosmological distances argued that the Eddington luminosity set limits on how distant the quasars could be since the energy output required to explain the apparent brightness of cosmologically-distant quasars was far too high to be explainable by nuclear fusion alone. This objection was made moot by the improved models of gravity-powered accretion disks which for sufficiently dense material (such as black holes) can be more efficient at energy production than nuclear reactions. The controversy was laid to rest by the 1990s when evidence became available that observed quasars were actually the ultra-luminous cores of distant active galactic nuclei and that the major components of their redshift were in fact due to the Hubble flow.
Throughout his career, Halton Arp maintained that there were anomalies in his observations of quasars and galaxies, and that those anomalies served as a refutation of the Big Bang. In particular, Arp pointed out examples of quasars that were close to the line of sight of (relatively) nearby active, mainly Seyfert galaxies. These objects are now classified under the term active galactic nuclei (AGN), Arp criticized using such term on the ground that it isn't empirical. He claimed that clusters of quasars were in alignment around cores of these galaxies and that quasars, rather than being the cores of distant AGN, were actually much closer and were starlike-objects ejected from the centers of nearby galaxies with high intrinsic redshifts. Arp also contended that they gradually lost their non-cosmological redshift component and eventually evolved into full-fledged galaxies. This stands in stark contradiction to the accepted models of galaxy formation.
The biggest problem with Arp's analysis is that today there are hundreds of thousands of quasars with known redshifts discovered by various sky surveys. The vast majority of these quasars are not correlated in any way with nearby AGN. Indeed, with improved observing techniques, a number of host galaxies have been observed around quasars which indicates that those quasars at least really are at cosmological distances and are not the kind of objects Arp proposes. Arp's analysis, according to most scientists, suffers from being based on small number statistics and hunting for peculiar coincidences and odd associations. Unbiased samples of sources, taken from numerous galaxy surveys of the sky show none of the proposed 'irregularities', nor that any statistically significant correlations exist.
In addition, it is not clear what mechanism would be responsible for intrinsic redshifts or their gradual dissipation over time. It is also unclear how nearby quasars would explain some features in the spectrum of quasars which the standard model easily explains. In the standard cosmology, clouds of neutral hydrogen between the quasar and the earth create Lyman alpha absorption lines having different redshifts up to that of the quasar itself; this feature is called the Lyman-alpha forest. Moreover, in extreme quasars one can observe the absorption of neutral hydrogen which has not yet been reionized in a feature known as the Gunn–Peterson trough. Most cosmologists see this missing theoretical work as sufficient reason to explain the observations as either chance or error.
Halton Arp has proposed an explanation for his observations by a Machian "variable mass hypothesis". The variable-mass theory invokes constant matter creation from active galactic nuclei, which puts it into the class of steady-state theories. With the passing of Halton Arp, this cosmology has been relegated to a dismissed theory.
In 1965, Hannes Alfvén proposed a "plasma cosmology" theory of the universe based in part on scaling observations of space plasma physics and experiments on plasmas in terrestrial laboratories to cosmological scales orders of magnitude greater. Taking matter–antimatter symmetry as a starting point, Alfvén together with Oskar Klein proposed the Alfvén-Klein cosmology model, based on the fact that since most of the local universe was composed of matter and not antimatter there may be large bubbles of matter and antimatter that would globally balance to equality. The difficulties with this model were apparent almost immediately. Matter–antimatter annihilation results in the production of high energy photons which were not observed. While it was possible that the local "matter-dominated" cell was simply larger than the observable universe, this proposition did not lend itself to observational tests.
Like the steady state theory, plasma cosmology includes a Strong Cosmological Principle which assumes that the universe is isotropic in time as well as in space. Matter is explicitly assumed to have always existed, or at least that it formed at a time so far in the past as to be forever beyond humanity's empirical methods of investigation.
While plasma cosmology has never had the support of most astronomers or physicists, a small number of plasma researchers have continued to promote and develop the approach, and publish in the special issues of the IEEE Transactions on Plasma Science. A few papers regarding plasma cosmology were published in other mainstream journals until the 1990s. Additionally, in 1991, Eric J. Lerner, an independent researcher in plasma physics and nuclear fusion, wrote a popular-level book supporting plasma cosmology called The Big Bang Never Happened. At that time there was renewed interest in the subject among the cosmological community along with other non-standard cosmologies. This was due to anomalous results reported in 1987 by Andrew Lange and Paul Richardson of UC Berkeley and Toshio Matsumoto of Nagoya University that indicated the cosmic microwave background might not have a blackbody spectrum. However, the final announcement (in April 1992) of COBE satellite data corrected the earlier contradiction of the Big Bang; the popularity of plasma cosmology has since fallen.
One of the major successes of the Big Bang theory has been to provide a prediction that corresponds to the observations of the abundance of light elements in the universe. Along with the explanation provided for the Hubble's law and for the cosmic microwave background, this observation has proved very difficult for alternative theories to explain.
Theories which assert that the universe has an infinite age, including many of the theories described above, fail to account for the abundance of deuterium in the cosmos, because deuterium easily undergoes nuclear fusion in stars and there are no known astrophysical processes other than the Big Bang itself that can produce it in large quantities. Hence the fact that deuterium is not an extremely rare component of the universe suggests that the universe has a finite age.
Theories which assert that the universe has a finite life, but that the Big Bang did not happen, have problems with the abundance of helium-4. The observed amount of 4He is far larger than the amount that should have been created via stars or any other known process. By contrast, the abundance of 4He in Big Bang models is very insensitive to assumptions about baryon density, changing only a few percent as the baryon density changes by several orders of magnitude. The observed value of 4He is within the range calculated.
- See the Planck Collaboration's 2015 data release.
- Hoyle, F., Home is Where the Wind Blows, 1994, 1997, 399-423
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- Skordis, C.; Mota, D. F.; Ferreira, P. G.; Boehm, C. (2006). "[astro-ph/0505519] Large Scale Structure in Bekenstein's theory of relativistic Modified Newtonian Dynamics". Physical Review Letters. 96 (11301): 011301. arXiv:astro-ph/0505519. Bibcode:2006PhRvL..96a1301S. doi:10.1103/PhysRevLett.96.011301. PMID 16486433.
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- Wright, E. L. (20 December 2010). "Errors in the Steady State and Quasi-SS Models". UCLA, Physics & Astronomy Department.
- A. Kashlinsky; F. Atrio-Barandela; D. Kocevski; H. Ebeling (2009). "A measurement of large-scale peculiar velocities of clusters of galaxies: technical details" (PDF). Astrophys. J. 691 (2): 1479–1493. arXiv:0809.3733. Bibcode:2009ApJ...691.1479K. doi:10.1088/0004-637X/691/2/1479. Retrieved 15 July 2010.
- Daniela Saadeh (22 September 2016). "Does the Universe look the same in all directions?". Retrieved 16 December 2016.
- "Errors in Tired Light Cosmology". ucla.edu.
- ""Tired-Light" Hypothesis Gets Re-Tired". Science. 28 June 2001. Retrieved 16 December 2016.
- Segal, I.E., Nicoll, J.F., Wu, P., Zhou, Z. 1993, Statistically Efficient Testing of the Hubble and Lundmark Laws on IRAS Galaxy Samples, Astrophys. J. 465-484
- Arp, H., Seeing Red, Redshifts, Cosmology and Academic Science, 1998
- Schneider; et al. (2007). "The Sloan Digital Sky Survey Quasar Catalog. IV. Fifth Data Release". The Astronomical Journal. 134 (1): 102–117. arXiv:0704.0806. Bibcode:2007AJ....134..102S. doi:10.1086/518474.
- Antonucci, R. (1993). "Unified Models for Active Galactic Nuclei and Quasars". Annual Review of Astronomy and Astrophysics. 31 (1): 473–521. Bibcode:1993ARA&A..31..473A. doi:10.1146/annurev.aa.31.090193.002353.
- Urry, P.; Paolo Padovani (1995). "Unified schemes for radioloud AGN". Publications of the Astronomical Society of the Pacific. 107: 803–845. arXiv:astro-ph/9506063. Bibcode:1995PASP..107..803U. doi:10.1086/133630.
- Arp and others who agree with him have been known to support the argument for a varying non-cosmological redshift by referring to a so-called "magnitude-redshift discrepancy". When a Hubble's law-type plot of quasar magnitudes versus redshift is made, a graph with a diffuse scatter and no clear linear relation is generated. However, since absolute magnitudes can only be independently calibrated to an upper limit using size constraints from variability and an Eddington luminosity, it is likely that quasars are exhibiting differing luminosities that cannot necessarily be derived from such simplistic first principles. Arp, Burbidge, and others maintain that the scatter in these plots further supports the idea that quasars have a non-cosmological component to their redshift, but nearly everyone else in the field accepts that quasars have variable luminosity.
- The first instance of observing the host galaxies around quasars was announced in 1983 by Gehren as published in the Proceedings of the Twenty-fourth Liege International Astrophysical Colloquium. p. 489-493.
- Overbye, Dennis (6 January 2014). "Halton Arp, 86, Dies; Astronomer Challenged Big Bang Theory". The New York Times.
- Tang, Sumin; Shuang Nan Zhang (2008). "Evidence against non-cosmological redshifts of QSOs in SDSS data". arXiv:0807.2641 [astro-ph].
- For a description of mainstream cosmology's view of Arp's suggestions in this regard see Jones, H. What makes an astronomical controversy? Astronomy Now Vol. 19, No. 3, p. 58–61 (2005).
- Flat Spacetime Cosmology: A unified framework for extragalactic redshifts in Astrophysical Journal by J Narlikar and H Arp
- “When he died, he took a whole cosmology with him,” said Barry F. Madore, a senior research associate at the Carnegie Observatories in Pasadena, Calif. https://www.nytimes.com/2014/01/07/science/space/halton-c-arp-astronomer-who-challenged-big-bang-theory-dies-at-86.html
- Hannes Alfvén, "On hierarchical cosmology" (1983) Astrophysics and Space Science (ISSN 0004-640X), vol. 89, no. 2, Jan. 1983, p. 313-324.
- (See IEEE Transactions on Plasma Science, issues in 1986, 1989, 1990, 1992, 2000, 2003, and 2007 Announcement 2007 Archived 28 September 2007 at the Wayback Machine here)
- Michael Lemonick (2003). Echo of the Big Bang. Princeton University Press. pp. 63–64. ISBN 978-0-691-10278-8.
- Arp, Halton, "Seeing Red". Apeiron, Montreal. August 1998. ISBN 0-9683689-0-5
- Hannes, Alfvén D., "Cosmic Plasma". Reidel Pub Co., February 1981. ISBN 90-277-1151-8
- Hoyle, Fred, and Geoffrey Burbidge, and Jayant V. Narlikar, "A Different Approach to Cosmology: From a Static Universe through the Big Bang towards Reality". Cambridge University Press. February 17, 2000. ISBN 0-521-66223-0
- Lerner. Eric J., "Big Bang Never Happened", Vintage Books, October 1992. ISBN 0-679-74049-X
- Mitchell, William C., "Bye Bye Big Bang: Hello Reality". Cosmic Sense Books. January 2002. ISBN 0-9643188-1-4
- Narlikar, Jayant Vishnu, "Introduction to Cosmology". Jones & Bartlett Pub. January 1983. IUCAA. ISBN 0-86720-015-4
- Peratt, Anthony L., "Physics of the Plasma Universe". Springer-Verlag, 1991, ISBN 0-387-97575-6
- Santanu Das, 2012, Cosmological solution of Machian gravity
- Lopez-Corredoira, Martín, 2003, Observational Cosmology: caveats and open questions in the standard model, Recent Research Developments in Astronomy & Astrophysics, vol. 1, S. G. Pandalai, Ed., Research Signpost, Kerala, pp. 561–589
- Lopez-Corredoira, Martín, 2009, Sociology of Modern Cosmology (ASP Conf. Ser. 409), in: J. A. Rubiño Martin, J. A. Belmonte, F. Prada, & A. Alberdi, Eds., Cosmology across Cultures, ASP, S. Francisco, pp. 66–73
- Narlikar, Jayant V. and T. Padmanabhan, "Standard Cosmology and Alternatives: A Critical Appraisal". Annual Review of Astronomy and Astrophysics, Vol. 39, p. 211-248 (2001).
- Tifft, W. G. Evidence for Quantization and Variable Redshifts in the Cosmic Background Rest Frame. Steward Observatory, University of Arizona, Tucson, Arizona
- Wright, Edward L. "Cosmological Fads and Fallacies:" Errors in some popular attacks on the Big Bang
- Cosmology at Curlie | 0.824492 | 4.144367 |
eso9719 — Science Release
Hints About Dark, Light-Bending Matter in the Distant Universe
25 July 1997: About 20 cases of gravitationally lensed (GL) quasars are known. This special physical effect, also known as a cosmic mirage, occurs when the rays of light of a distant quasar on their way to us pass near a massive object, for instance a galaxy. As a result, two or more images of the same quasar will be seen near each other. This phenomenon is described in more detail in the Appendix. A new study by a group of three European astronomers, headed by Frederic Courbin ( Institut d'Astrophysique, Universite de Liege, Belgium, and Observatoire de Paris-Meudon, France) , has led to the discovery of the object responsible for the double images of a remote quasar in the gravitational lens HE 1104-1805 . The investigation is based on infrared observations at the ESO La Silla Observatory in Chile and the `lensing system' turns out to be a distant, massive galaxy. Nevertheless, the geometry of the object is unusual and an additional gravitational lens of `dark' (invisible) matter may possibly be involved. | 0.85858 | 3.410782 |
Gibbous ♏ Scorpio
Moon phase on 10 March 2015 Tuesday is Waning Gibbous, 19 days old Moon is in Scorpio.Share this page: twitter facebook linkedin
Previous main lunar phase is the Full Moon before 4 days on 5 March 2015 at 18:06.
Moon rises in the evening and sets in the morning. It is visible to the southwest and it is high in the sky after midnight.
Moon is passing about ∠12° of ♏ Scorpio tropical zodiac sector.
Lunar disc appears visually 6.1% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1818" and ∠1932".
Next Full Moon is the Pink Moon of April 2015 after 25 days on 4 April 2015 at 12:06.
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 19 days old. Earth's natural satellite is moving from the middle to the last part of current synodic month. This is lunation 187 of Meeus index or 1140 from Brown series.
Length of current 187 lunation is 29 days, 9 hours and 49 minutes. It is 28 minutes longer than next lunation 188 length.
Length of current synodic month is 2 hours and 55 minutes shorter than the mean length of synodic month, but it is still 3 hours and 14 minutes longer, compared to 21st century shortest.
This New Moon true anomaly is ∠354.5°. At beginning of next synodic month true anomaly will be ∠9.9°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
5 days after point of apogee on 5 March 2015 at 07:35 in ♍ Virgo. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 9 days, until it get to the point of next perigee on 19 March 2015 at 19:38 in ♓ Pisces.
Moon is 394 296 km (245 004 mi) away from Earth on this date. Moon moves closer next 9 days until perigee, when Earth-Moon distance will reach 357 584 km (222 192 mi).
2 days after its ascending node on 7 March 2015 at 21:04 in ♎ Libra, the Moon is following the northern part of its orbit for the next 10 days, until it will cross the ecliptic from North to South in descending node on 21 March 2015 at 02:19 in ♈ Aries.
2 days after beginning of current draconic month in ♎ Libra, the Moon is moving from the beginning to the first part of it.
11 days after previous North standstill on 27 February 2015 at 07:19 in ♊ Gemini, when Moon has reached northern declination of ∠18.335°. Next 3 days the lunar orbit moves southward to face South declination of ∠-18.262° in the next southern standstill on 14 March 2015 at 01:39 in ♐ Sagittarius.
After 9 days on 20 March 2015 at 09:36 in ♓ Pisces, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.124455 |
Dec 5, 2018
The moons of Mars are scarred worlds.
The two moons of Mars are called Phobos and Deimos, meaning “fear and “panic”. Phobos is extensively studied by Earth-based telescopes and by satellites in Mars orbit. Deimos, however, is so small that major observations are impossible from Earth.
Stickney crater dominates one hemisphere of Phobos. It is a 10-kilometer-wide, 100-meter-deep scar that is supposed to be the result of an impact. Previous Pictures of the Day illustrate the physical problems associated with that theory, since blasting large craters into small bodies ought to disrupt their overall structure. For example, there is a hole in asteroid 253 Mathilde big enough to disintegrate the asteroid, except that it is still there.
Phobos is a mere 28 by 20 kilometers in size, so Stickney crater is nearly half as big as the asteroid-sized moon. Why are both objects intact? Planetary scientists speculate that asteroids (and small moons) are loosely aggregated, similar to a gravel pit. Since the celestial bodies in question were not blown apart, it is thought that they behave like piles of sand, cushioning the shocks.
Since Phobos is about the same size as asteroids Mathilde, Eros and Ida, is there something that can form similar structures without obliterating the objects in the first place? The answer is electricity.
Some astronomers think that fracture lines around Stickney crater prove that the moon underwent severe shock, and that it was distorted on impact. On closer examination, the grooves are chains of small craters, not “fracture lines”. The area around the crater is blunted and smooth, with no large breccias, although the moon is covered with a meter of ultra-fine dust. A recent press release ascribes the furrows to “rolling boulders”, although a telling comment from the article states, “But there’s a problem: we don’t see any boulders on the surface.”
Picture of the Day articles about Mars reveal that millions of cubic kilometers of rock and dust were blasted out of the planet, reaching escape velocity. Stone blocks larger than Manhattan Island also fell back to Mars from a great height, which explains the fields of boulders with sharp edges covering thousands of square kilometers.
The electrical history of the solar system includes intensely energetic events and violent interactions. Plasma discharges excavated surface depressions, scooped out material and then blasted it into space, leaving cleanly cut features. The lightning bolts that carved Mars threw large chunks of its crust into orbit. The result was that Phobos and the aforementioned asteroids are covered in dust, and are defined by huge craters that look half-melted.
Phobos and Deimos are the remnants of a catastrophic event that electrically devastated Mars. | 0.880502 | 3.8821 |
Why did a picturesque volcanic eruption in Iceland create so much ash? Although the large ash plume was not unparalleled in its abundance, its location was particularly noticeable because it drifted across such well-populated areas. The Eyjafjallajökull volcano in southern Iceland began erupting on 2010 March 20, with a second eruption starting under the center of a small glacier on 2010 April 14. Neither eruption was unusually powerful. The second eruption, however, melted a large amount of glacial ice which then cooled and fragmented lava into gritty glass particles that were carried up with the rising volcanic plume. Pictured here during the second eruption, lightning bolts illuminate ash pouring out of the Eyjafjallajökull volcano.
How smooth is the Sun? The new Swedish 1-m Solar Telescope, deployed in the Canary Islands only last year, allows imaging of objects less than 100-km across on the Sun's surface. When pointed toward the Sun's edge, surface objects now begin to block each other, indicating true three-dimensional information. Close inspection of the image reveals much vertical information, including spectacular light-bridges rising nearly 500-km above the floor of sunspots near the top of the image. Also visible in the above false-color image are hundreds of bubbling granules, each about 1000-km across, and small bright regions known as faculas.
Watch Juno zoom past Jupiter again. NASA's robotic spacecraft Juno is continuing on its 53-day, highly-elongated orbits around our Solar System's largest planet. The featured video is from perijove 16, the sixteenth time that Juno has passed near Jupiter since it arrived in mid-2016. Each perijove passes near a slightly different part of Jupiter's cloud tops. This color-enhanced video has been digitally composed from 21 JunoCam still images, resulting in a 125-fold time-lapse. The video begins with Jupiter rising as Juno approaches from the north. As Juno reaches its closest view -- from about 3,500 kilometers over Jupiter's cloud tops -- the spacecraft captures the great planet in tremendous detail. Juno passes light zones and dark belt of clouds that circle the planet, as well as numerous swirling circular storms, many of which are larger than hurricanes on Earth. As Juno moves away, the remarkable dolphin-shaped cloud is visible. After the perijove, Jupiter recedes into the distance, now displaying the unusual clouds that appear over Jupiter's south. To get desired science data, Juno swoops so close to Jupiter that its instruments are exposed to very high levels of radiation.
Why would the sky look like a giant fan? Airglow. The featured intermittent green glow appeared to rise from a lake through the arch of our Milky Way Galaxy, as captured during 2015 next to Bryce Canyon in Utah, USA. The unusual pattern was created by atmospheric gravity waves, ripples of alternating air pressure that can grow with height as the air thins, in this case about 90 kilometers up. Unlike auroras powered by collisions with energetic charged particles and seen at high latitudes, airglow is due to chemiluminescence, the production of light in a chemical reaction. More typically seen near the horizon, airglow keeps the night sky from ever being completely dark.
How do distant asteroids differ from those near the Sun? To help find out, NASA sent the robotic New Horizons spacecraft past the classical Kuiper belt object 2014 MU69, nicknamed Ultima Thule, the farthest asteroid yet visited by a human spacecraft. Zooming past the 30-km long space rock on January 1, the featured image is the highest resolution picture of Ultima Thule's surface beamed back so far. Utima Thuli does look different than imaged asteroids of the inner Solar System, as it shows unusual surface texture, relatively few obvious craters, and nearly spherical lobes. Its shape is hypothesized to have formed from the coalescence of early Solar System rubble in into two objects -- Ultima and Thule -- which then spiraled together and stuck. Research will continue into understanding the origin of different surface regions on Ultima Thule, whether it has a thin atmosphere, how it obtained its red color, and what this new knowledge of the ancient Solar System tells us about the formation of our Earth. | 0.876966 | 3.179652 |
Sep 26, 2012
Did sulfurous compounds from ancient volcanoes help warm up Mars and form the now extinct Martian oceans?
Speculations about the existence of liquid oceans on Mars have been around for centuries. The Mars Science Laboratory, known as Curiosity, is currently seeking evidence for that conjecture. Images from orbiting cameras supposedly confirm that water once flowed on the surface of the now frozen and barren planet. However, recent publications cast doubt on that idea.
At this point, after several years of exploration, no confirmation either way has been forthcoming. Some discoveries, such as the presence of olivine deposits on the surface, seem to preclude the existence of water on Mars since olivine is readily dissolved and dispersed in water. Any large deposits would have been washed away eons ago if there had been large quantities of liquid.
Scientists from the University of California at Berkeley wrote one of the more interesting “confirmations” for the liquid ocean hypothesis. Although the oceans have been gone for over 2 billion years, two “shorelines” extending for thousands of kilometers have been overlooked in past analyses of satellite imagery.
Crustal folds have supposedly obscured the shape of a fossil coastline as the planet deformed during a change in its rotational direction in the past. Due to some kind of imbalance in the mass distribution inside Mars the planet tilted over by at least 50 degrees on its axis, causing crustal distortions. Due to the change in orientation, increased exposure to the solar wind caused much of the water that once occupied the ocean basins to be lost.
It is proposed by planetary scientists that one-fifth of the Martian surface was once covered with water, so there “must be” more water remaining, locked-up in the rocks or buried underground in giant blocks of ice.
Another factor that contributed to the Martian oceans is carbon dioxide with large percentages of sulfur dioxide and hydrogen sulfide. Today, the average temperature on Mars is -45 C, with a mean surface atmospheric pressure equivalent to standing on top of a mountain six times taller than Mount Everest. The atmosphere is frozen, dry and thin to the point where water would immediately sublime and dissociate, so somehow that atmosphere must have been thicker and warmer in the past.
The present carbon dioxide atmosphere is said to indicate an older version of the planet with greater atmospheric density containing more gas, according to conventional understanding: a “greenhouse effect”. The problem is that no amount of carbon dioxide in the evolution of any planet is sufficient to warm up the atmosphere by itself.
Other researchers speculate that volcanoes on Mars once erupted with tremendous quantities of sulfurous gases, acidifying the then extant oceans and preventing the formation of carbonates. Mars has a lot more sulfur than Earth, so the sulfuric acid is supposed to have dissolved away the limestone beds, for instance, while at the same time acting as a booster to the greenhouse environment.
Earth and Mars are presumed to have been similar in the past so many explanations have been offered for why the two planets diverged into their disparate natural settings. It is not surprising that electricity in the form of plasma discharges and lighting bolts has never been considered in the development of each world.
As Electric Universe advocate Wal Thornhill wrote:
“The idea of former oceans and rivers existing on Mars came from the many scoured channels and the flat, low terrain in the northern hemisphere. This marked hemispheric dichotomy is inexplicable by any known geological or astronomical effect. It has never occurred to geologists that the agent involved was electrified plasma. Why should it? Astrophysicists tell them that we live in an electrically neutral universe in which cosmic charge separation is impossible. But if that single assumption is incorrect everything changes. If the visible universe suffers cosmic charge separation then we have a source of energy to build and shape galaxies, light stars, give birth to planets, organize stable orbits and leave the resulting scars of electrical transactions on all solid bodies.” | 0.834637 | 3.894366 |
Feb 01, 2013
Galactic tails, bright comas, and central nuclei are reminiscent of comets.
What is a comet? Most astronomers think comets are small, fragile, irregularly shaped objects composed mostly of water ice and dust, along with carbon and silicon-based compounds. “Dirty snowballs,” as Fred Whipple described them in 1950. Consensus opinions continue to support the theory after almost 60 years.
According to Whipple’s proposal, when a comet approaches the Sun, the “hot” solar wind transforms its solid nuclei directly into a vapor through sublimation, bypassing the liquid phase. Material begins to expand outward, forming a cloud of gas and dust otherwise known as the coma. Sunlight and the solar wind interact with the cloud to form a long tail.
However, Electric Universe advocates see them differently.
Comets spend most of their time far from the Sun where the charge density is low. Since comets move slowly, their electric charges reach equilibrium with the weak, radial solar electric field. When a comet falls in to the inner Solar System closer to the Sun, however, its nucleus accelerates into regions of increasing charge density and voltage.
Charge polarization in the nucleus respond to the increasing electrical stress, forming a vast coma (plasma sheath) around the comet. Discharge jets flare up and move across the surface, similar to the plumes on Jupiter’s moon, Io. If the internal electrical stress becomes too great, the nucleus may explode like an overcharged capacitor, breaking into fragments or vanishing forever. Similar effects are most likely responsible for meteoric explosions in Earth’s atmosphere, such as the one that occurred over Tunguska in Siberia.
Surprisingly, an image from the Hubble Space Telescope highlights an “odd-looking spiral galaxy” moving at 3.5 million kilometers per hour through Abell 2667. Its high velocity is primarily attributed to the gravitational forces exerted by dark matter, hot gas, and other galaxies in the cluster.
“This unique galaxy, situated 3.2 billion light-years from Earth, has an extended stream of bright blue knots and diffuse wisps of young stars driven away by the tidal forces and the ‘ram pressure stripping’ of the hot dense gas.”
In past Picture of the Day articles, shock waves, hot gas, and collisions in deep space are not considered appropriate explanations when discussing high-energy electromagnetic radiation in the cosmos. From gamma rays down through X-rays and extreme ultraviolet, conventional theories rely upon gravitational acceleration, explosions and collisions as the only way for them to be produced in space.
The conventional story of gas being stripped from this galaxy by ram pressure and stars being torn from it by the gravity of the galactic cluster has no place in an Electric Universe. The gas and stars are subject to more powerful electromagnetic influences both external and internal to the galaxy. The conventional mechanical comet model is as inappropriate for the “Comet Galaxy” as it is for comets in our solar system.
Electrical connections exist throughout the Universe. From the smallest scale atomic interactions to the largest scale cosmic conglomerations, electricity provides the power and demonstrates its activity in plain sight.
Stephen Smith and Wal Thornhill
Click here for a Spanish translation | 0.920465 | 4.058205 |
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In January 2018 scientists announced the discovery of eight cliffs with visible exposed ice layers in the high mid-latitudes of Mars. At the time, those eight ice scarps were limited to a single crater in the northern hemisphere (Milankovic Crater) and a strip of land in the southern highlands at around latitude 55 degrees south.
In the past two years scientists have been using the high resolution camera on Mars Reconnaissance Orbiter (MRO) to monitor these scarps for changes. So far they have seen none, likely because the changes are below the resolution of the camera.
They have also been able to find more scarps in the southern hemisphere strip beyond that strip at 55 degrees south.
Now they have found more scarps in the northern hemisphere as well, and these are outside Milankovic Crater. As in the south, the new scarps are still all along a latitude strip at about 55 degrees.
The map above shows with the black dots the newer scarps located in the past two years. The scarp to the east of Milankovic Crater is typical of all the other scarps, a steep, pole-facing cliff that seems to be retreating away from the pole..
The scarp to the west of Milankovic Crater is striking in that it is actually a cluster of scarps, all inside a crater in the northern lowland plains. Moreover, these scarps are more indistinct, making them more difficult to identify. According to Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona,
One of the scarps in that image has some very slight bluish coloration and the morphology is basically similar. Our interpretation is that these are scarps that have become covered by a lag of dust as they sublimate, rather than shedding the dust to keep a good exposure of ice. That would also account for the less-distinct appearance.
The image to the right shows this cluster of indistinct scarps, all located on interior slope of the crater’s south rim.
Dundas also hinted in his email to me that they have found even more scarps in the north. In March at the 51st Lunar and Planetary Science Conference in Texas, he will be presenting more results on this subject [pdf]. As I will be attending this conference, I will be able to get the most up-to-date results for my readers. | 0.820659 | 3.178734 |
On October 19, 2017 astronomer Robert Weryk discovered an object passing by the sun, and it was determined that it had experienced repeated episodes of non-gravitational acceleration. The object, named ‘Oumuamua (meaning ‘messenger from afar arriving first’ in Hawaiian), is considered the first interstellar traveler we’ve detected passing through our solar system at an incredible speed, but no one knows exactly what it is or where it came from.
Well, Harvard astronomer Avi Loeb thinks he knows and suggested this object may be an alien spacecraft with a light sail sent on a reconnaissance mission, and that no one should blindly dismiss his idea because “That is a prejudice that we shouldn’t have.” Instead, we should be open-minded, he suggests.
This isn’t the first time scientists thought they discovered evidence of intelligent alien life. Back in 2015 scientists found a star (called Boyajian’s Star) above the Milky Way with ‘megastructures’ thought to look like something one would “expect an alien civilization to build.”
But why would any rational scientist think this? According to Penn State Astronomer Jason Wright, “I can’t figure this thing out and that’s why it’s so interesting, so cool- it just doesn’t seem to make sense.” Ok, so, because it doesn’t make sense, it’s gotta be aliens! Right.
The funny thing is that these claims are taken very seriously by some. In this case scientists actually suggested these ‘megastructures’ were big solar panels placed around the star to collect energy. Of course, there are plenty of natural explanations for the observed phenomena- such as debris from comets, but some people do believe in aliens, and any anomaly is enough to spark the imagination.
As for Oumuamua, it has been classified as both an asteroid or a comet at one time or another, then considered neither an asteroid or comet, and now it’s thought to be an asteroid again. Nonetheless we can reasonably conclude that it originated outside our solar system because it has the same reddish hue as objects outside our solar system, and it’s traveling at such a high rate of speed that it can’t be captured in solar orbit. There are no radio emissions or other signals coming from it; it’s thought to be up to a half mile long, extremely elongated, tumbling through space, and scientists have concluded that the acceleration is due to jets of gasses escaping the object as it races through space.
I think it’s far more reasonable to conclude that both Oumuamua and Boyajian’s star are natural phenomena and not alien in nature, and as we gather more information, we can make better assessments. There is no scientific evidence for alien life, except for evolutionary speculation and conjecture. We don’t need to resort to aliens whenever something doesn’t make sense. Doing so halts scientific progress because it stops further research and inquiry. Instead, we should continue researching to find the answers to our questions. Aliens are never the answer. | 0.906182 | 3.559152 |
We always see the same side of the Moon. It’s always up there, staring down at us with its terrifying visage. Or maybe it’s a creepy rabbit? Anyway, it’s always showing us the same face, and never any other part.
This is because the Moon is tidally locked to the Earth; the same fate that affects every single large moon orbiting a planet. The Moon is locked to the Earth, the Jovian moons are locked to Jupiter, Titan is locked to Saturn, etc.
As the Moon orbits the Earth, it slowly rotates to keep the same hemisphere facing us. Its day is as long as its year. And standing on the surface of the Moon, you’d see the Earth in roughly the same spot in the sky. Forever and ever.
We see this all across the Solar System.
But there’s one place where this tidal locking goes to the next level: the dwarf planet Pluto and its large moon Charon are tidally locked to each other. In other words, the same hemisphere of Pluto always faces Charon and vice versa.
It take Pluto about 6 and a half days for the Sun to return to the same point in the sky, which is the same time it takes Charon to complete an orbit, which is the same time it takes the Sun to pass through the sky on Charon.
Since Pluto eventually locked to its moon, can the same thing happen here on Earth. Will we eventually lock with the Moon?
Before we answer this question, let’s explain what’s going on here. Although the Earth and the Moon are spheres, they actually have a little variation. The gravity pulling on each world creates love handle tidal bulges on each world.
And these bulges act like a brake, slowing down the rotation of the world. Because the Earth has 81 times the mass of the Moon, it was the dominant force in this interaction.
In the early Solar System, both the Earth and the Moon rotated independently. But the Earth’s gravity grabbed onto those love handles and slowed down the rotation of the Moon. To compensate for the loss of momentum in the system, the Moon drifted away from the Earth to its current position, about 370,000 kilometers away.
But Moon has the same impact on the Earth. The same tidal forces that cause the tides on Earth are slowing down the Earth’s rotation bit by bit. And the Moon is continuing to drift away a few centimeters a year to compensate.
It’s hard to estimate exactly when, but over the course of tens of billions of years, the Earth will become locked to the Moon, just like Pluto and Charon.
Of course, this will be long after the Sun has died as a red giant. And there’s no way to know what kind of mayhem that’ll cause to the Earth-Moon system. Other planets in the Solar System may shift around, and maybe even eject the Earth into space, taking the Moon with it.
What about the Sun? Is it possible for the Earth to eventually lock gravitationally to the Sun?
Astronomers have found extrasolar planets orbiting other stars which are tidally locked. But they’re extremely close, well within the orbit of Mercury.
Here in our Solar System, we’re just too far away from the Sun for the Earth to lock to it. The gravitational influence of the other planets like Venus, Mars and Jupiter perturb our orbit and keep us from ever locking. Without any other planets in the Solar System, though, and with a Sun that would last forever, it would be an inevitability.
It is theoretically possible that the Earth will tidally lock to the Moon in about 50 billion years or so. Assuming the Earth and Moon weren’t consumed during the Sun’s red giant phase. I guess we’ll have to wait and see. | 0.840871 | 3.609146 |
Moon* ♈ Aries
Moon phase on 22 September 2067 Thursday is Full Moon, 14 days old Moon is in Pisces.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 ∠22° of ♓ Pisces tropical zodiac sector.
Lunar disc appears visually 2.3% wider than solar disc. Moon and Sun apparent angular diameters are ∠1956" and ∠1912".
The Full Moon this days is the Harvest of September 2067.
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 837 of Meeus index or 1790 from Brown series.
Length of current 837 lunation is 29 days, 15 hours and 19 minutes. It is 33 minutes longer than next lunation 838 length.
Length of current synodic month is 2 hours and 35 minutes longer than the mean length of synodic month, but it is still 4 hours and 28 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠207.1°. At the beginning of next synodic month true anomaly will be ∠237.7°. 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 21 September 2067 at 11:31 in ♓ Pisces. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 11 days, until it get to the point of next apogee on 3 October 2067 at 12:21 in ♌ Leo.
Moon is 366 436 km (227 693 mi) away from Earth on this date. Moon moves farther next 11 days until apogee, when Earth-Moon distance will reach 405 262 km (251 818 mi).
6 days after its ascending node on 15 September 2067 at 19:19 in ♐ Sagittarius, the Moon is following the northern part of its orbit for the next 5 days, until it will cross the ecliptic from North to South in descending node on 28 September 2067 at 09:08 in ♊ Gemini.
6 days after beginning of current draconic month in ♐ Sagittarius, the Moon is moving from the beginning to the first part of it.
6 days after previous South standstill on 16 September 2067 at 01:16 in ♐ Sagittarius, when Moon has reached southern declination of ∠-22.627°. Next 6 days the lunar orbit moves northward to face North declination of ∠22.519° in the next northern standstill on 28 September 2067 at 17:33 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 | 3.110406 |
Pluto fans are attempting to reignite a contentious astronomy debate: What is a planet?
Is Pluto a planet?
It’s not a question scientists ask in polite company.
“It’s like religion and politics,” said Kirby Runyon, a planetary scientist at Johns Hopkins University. “People get worked up over it. I’ve gotten worked up over it.”
The issue can bring conversations to a screeching halt, or turn them into shouting matches. “Sometimes,” Runyon said, “it’s just easier not to bring it up.”
But Runyon will ignore his own advice this week when he attends the annual Lunar and Planetary Science Conference in Houston. In a giant exhibit hall crowded with his colleagues, he’s attempting to reignite the debate about Pluto’s status with an audacious new definition for planet — one that includes not just Pluto, but several of its neighbors, objects in the asteroid belt, and a number of moons. By his count, 102 new planets could be added to our solar system under the new criteria.
When the IAU voted in 2006, scientists came to the conclusion that gravitational dominance is what distinguishes the eight planets from the solar system’s other spheres. From giant Jupiter to tiny Mercury, each is massive enough to make them the bullies of their orbits, absorbing, ejecting or otherwise controlling the motion of every other object that gets too close. According to the definition, planets must also orbit the sun.
Pluto, which shares its zone of the solar system with a host of other objects, was reclassified as a “dwarf planet” — a body that resembles a planet but fails to “clear its neighborhood,” in the IAU’s parlance.
But to Runyon, that distinction is less important than what dozens of solar system worlds have in common: geology.
“I’m interested in an object’s intrinsic properties,” he said. “What it is on its surface and in its interior? Whether an object is in orbit around another planet or the sun doesn’t really matter for me.”
Runyon calls his a “geophysical” definition. A planet, he says, is anything massive enough that gravity pulls it into a sphere (a characteristic called “hydrostatic equilibrium”), but not so massive that it starts to undergo nuclear fusion and become a star.
If you talk to enough scientists on either side of this debate, you’ll notice that their arguments start to echo each other. They use the same terms to criticize the definitions they don’t like: “not useful,” “too emotional,” “confusing.” Both groups want the same thing: for the public to understand and embrace the science of the solar system. But each is convinced that only their definition can achieve that goal. And each accuses the other of confusing people by prolonging the debate.
Give us Pluto back! | 0.900723 | 3.46571 |
Venus Express, Europe’s first mission to Venus, has now successfully orbited our closest neighbour 355 times during the past year. Coincidentally on its first anniversary on 11 April, Venus and the constellation Pleiades are very close in the sky, for your viewing pleasure.
The celestial spectacle is clearly visible with the naked eye – provided that there are no clouds to cover it. Venus and Pleiades can be seen drawing closer together in the western sky; after sunset and before midnight. The planet and the star cluster will be close enough to fit behind an upturned thumb held at arm's length.
Although the time of closest approach as seen from Earth is during the early morning hours of 12 April, it will not be visible then since Venus sets at midnight. Given that there is currently no moon in the evening hours, the uncommon occurrence will be even more obvious.
Venus and the Pleiades form a peculiar couple. Venus is extravagantly bright surrounded by a thick atmosphere reflecting 70 percent of all received light. The Pleiades however are dim and slight, since the young and not yet completely formed cluster is 400 light years away. These opposite characteristics offer a pretty view for star-gazers as well as photographers and astronomers.
Thanks to its intense reflection, Venus is the brightest planet within the solar system making it fairly easy to distinguish the ensemble as it outshines all stars and planets in the evening sky.
Take a look and raise a toast to Venus Express’ first anniversary! | 0.834571 | 3.106289 |
In astronomy, all elements other than hydrogen and helium are referred to as “metals.” For this reason, a measure of the amount of other elements a star contains is known as its metallicity. One way to define the metallicity of a star is simply as the fraction of a star’s mass which is not hydrogen or helium. For the Sun, this number is Z = 0.02, which means that about 2% of the Sun’s mass is “metal”. Another way to express the metallicity of a star is by its ratio of Iron to Hydrogen, known as [Fe/H]. This is given on a logarithmic scale relative to the ratio of our Sun. So the [Fe/H] of our Sun is zero. Stars with lower metallicity will have negative [Fe/H] values, and ones with higher metallicity have positive values.When it comes to planetary systems, it’s generally been thought that planets would tend to form around stars with a higher metallicity. At a broad level that makes sense because rocky planets such as Earth can only form in a system where there are enough metals like iron, silicon, carbon and the like. You can’t make a terrestrial planet out of just hydrogen and helium. But now that we’ve discovered lots of exoplanetary systems, we can actually put this idea to the test. A recent paper in Nature has done just that, and they’ve found something rather interesting.1
In the paper, the authors looked at about 400 stars with exoplanets (about 600 exoplanets in all). They then compared the size of the exoplanets with the metallicity of their stars. What they found was that there was a distinct relation between the metallicity of a star and the type of planets it has. Stars with a metallicity similar to our Sun’s were more likely to have terrestrial planets, while stars with higher metallicity tend to have gas dwarfs, or gas giants (Jupiter-like). The study also showed that high metallicity stars are likely to have so-called “hot-Jupiters”. That is, large gas giants orbiting close to a star.
We’ve seen in computer models how large protoplanets will tend to migrate inward toward the star as they form. This new work would seem to support that idea, since higher metallicity stars would be more likely to form gas giants early on, thus allowing them to migrate inward to become hot Jupiters.
So it seems that metallicity is a significant factor in planetary formation, and higher metallicity stars will tend to form larger planets. But it also seems that stars similar to the Sun are better suited for having terrestrial planets like ours.
Buchhave, Lars A., et al. “Three regimes of extrasolar planet radius inferred from host star metallicities.” Nature 509.7502 (2014): 593-595. ↩︎ | 0.818887 | 3.896219 |
The Voyager probes have been in the news recently as the first Voyager launched has now left the bubble of weather in space that the sun forms around itself, meaning that both Voyagers 1 and 2 are now in interstellar space.
The background for these two probes is fascinating The year picked allowed the probes to accelerate using the motion of the planets. It’s likely that nothing will ever critically fail, they’ll just outlive the half-life of their nuclear fuels. Each holds golden records of information of life on Earth. As you can tell, I could go on.
The thing that is incredible about them from a human point of view is something that is often commented upon as only a sentence or two, but requires some context.
Over the course of history, humanity has achieved a lot. We have built the 7 wonders of the world, created countries, created cultures, travelled into space and landed on alien worlds. Given that we have only been around for approximately 300 thousand years, we’ve done well.
In the end though, it’s likely that all the wonders we have created will be lost. In 4 – 5 billion years the sun will end its main sequence and start to become a red giant. At this point, the Earth will either be consumed by the Sun or very likely, be literally melted by it. Either fate will destroy essentially everything we have ever created.
Radiowaves that we have transmitted will survive as will probes that we have sent into space.
The remaining wonders
The transmitted radio waves will become ever fainter to the point where they will likely be undetectable from noise and the probes in the solar system will eventually be destroyed by collisions with other objects. The only physical things we have built to remain intact will be Pioneers 10 & 11, New Horizons and the Voyager probes.
As of the 5th of November 2018, the two Voyager probes left the solar system and took up orbits around the Milkey way in their own rights. Their orbits are predicted to be last for billions of years (as there is so little in the interstellar medium), meaning that they will likely outlive the Earth, us and everything else we have ever built.
The current wonders of the world have survived the test of time. They are (by modern terms) simple, and simple survives. Technology is renowned for breaking or being temperamental. When you look at the pyramids of Giza you see a human construction that has survived for over four and a half thousand years. It’s hard to believe that, to date, five delicate probes, pieces of high technology, will be the only physical proof that we were ever here. | 0.817437 | 3.139317 |
Crescent ♍ Virgo
Moon phase on 30 July 2060 Friday is Waxing Crescent, 3 days young Moon is in Virgo.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 2 days on 27 July 2060 at 12:49.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Moon is passing about ∠13° of ♍ Virgo tropical zodiac sector.
Lunar disc appears visually 5% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1798" and ∠1890".
Next Full Moon is the Sturgeon Moon of August 2060 after 12 days on 12 August 2060 at 00:51.
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 749 of Meeus index or 1702 from Brown series.
Length of current 749 lunation is 29 days, 12 hours and 7 minutes. It is 2 hours and 50 minutes shorter than next lunation 750 length.
Length of current synodic month is 37 minutes shorter than the mean length of synodic month, but it is still 5 hours and 32 minutes longer, compared to 21st century shortest.
This New Moon true anomaly is ∠84.5°. At beginning of next synodic month true anomaly will be ∠119.2°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
10 days after point of perigee on 20 July 2060 at 04:58 in ♈ Aries. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 3 days, until it get to the point of next apogee on 3 August 2060 at 08:10 in ♎ Libra.
Moon is 398 681 km (247 729 mi) away from Earth on this date. Moon moves farther next 3 days until apogee, when Earth-Moon distance will reach 404 228 km (251 176 mi).
9 days after its ascending node on 20 July 2060 at 22:57 in ♈ Aries, the Moon is following the northern part of its orbit for the next 4 days, until it will cross the ecliptic from North to South in descending node on 3 August 2060 at 14:41 in ♎ Libra.
9 days after beginning of current draconic month in ♈ Aries, the Moon is moving from the beginning to the first part of it.
5 days after previous North standstill on 25 July 2060 at 08:10 in ♋ Cancer, when Moon has reached northern declination of ∠27.680°. Next 9 days the lunar orbit moves southward to face South declination of ∠-27.761° in the next southern standstill on 8 August 2060 at 17:40 in ♐ Sagittarius.
After 12 days on 12 August 2060 at 00:51 in ♒ Aquarius, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.848363 | 3.201627 |
New Exoplanet Discovered
This week, a team of astronomers at the Keck Observatory announced the discovery of Gliese 581g, a planet orbiting Gliese 581, a red dwarf star twenty light years away (and part of the constellation Libra). Gliese 581g is one of six planets that have been detected around this star, but it is the first that seems to "fit" the requirements for life, which led Steven Vogt to term it the "Goldilocks planet."
Vogt, one of the leads on the team that discovered Gliese 581g, is a professor of astronomy and astrophysics at UC Santa Cruz and a member of the Science Buddies Advisory Board.
Goldilocks is "a well-worn analogy," said Vogt, "but in this case it fits. We had planets on both sides of the habitable zone—one too hot and one too cold—and now we have one in the middle that's just right."
Similar in size to the Earth, Gliese 851g is orbiting in the "habitable zone" around the star, a distance not too close and not too far away—a distance where liquid water could be found. Astronomers describe the planet as "potentially habitable," and one media account of the news included this headline: "Odds of Alien Life on Newly Spotted Exoplanet are '100 Percent' Says Its Discover."
According to reports, Gliese 581g has a nearly circular orbit of almost 37 days and a mass 3 to 4 times that of the Earth. According to Vogt, the increased mass potentially indicates that Gliese 581g has a rocky terrain—and enough gravity to anchor an atmosphere. The planet does not rotate, however, as the Earth does. Instead, it is "tidally locked" to the star. This means that one side of the planet is always in daylight and one side is always in darkness. This might also mean that the likelihood of life on the planet sits somewhere in the middle.
The Powerful Keck
Astronomers deem the discovery of Gliese 581g as "fast," but time and distance are relative when it comes to astronomy and astrophysics. The news of Gliese 581g emerges based on 11 years of observations at the Keck Observatory by a team of astronomers led by Vogt (University of California, Santa Cruz) and Paul Butler (Carnegie Institution of Washington D.C.).
Using the Keck's HIRES spectrometer, the team was monitoring changes in the radial velocity of Gliese 581, changes that can indicate the presence of an orbiting planet. The process is time consuming. "It's really hard to detect a planet like this," Vogt said. "Every time we measure the radial velocity, that's an evening on the telescope, and it took more than 200 observations with a precision of about 1.6 meters per second to detect this planet."
The team's radial velocity observations were balanced by night-to-night "brightness measurements" conducted by team members using robotic telescopes at Tennessee State University. The brightness studies offered a way to ensure the radio velocity changes were indicative of a new planet and not due to other star activity.
The Keck Observatory sits at the top of Hawaii's dormant Mauna Kea volcano where the twin Keck telescopes offer astronomers an unparalleled precision view into distant space. Standing over eight stories tall, and with primary mirrors that are 10 meters in diameter, these are the world's largest optical and infrared telescopes.
Students interested in exploring the use of sophisticated astronomy equipment to make observations may find the following Science Buddies project ideas illuminating:
- Using the Solar & Heliospheric Observatory Satellite (SOHO) to Measure the Motion of a Coronal Mass Ejection (Difficulty: 7-9)
- Using the Solar & Heliospheric Observatory Satellite (SOHO) to Determine the Rotation of the Sun (Difficulty: 7)
Or, to really get down to the nitty-gritty of what's involved, start from the ground up and build your own telescope (Difficulty: 9-10).
Official Keck announcement:
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Make A Tissue Paper Parachute - STEM Activity | 0.866373 | 3.744987 |
Space near the Sun is mostly empty, devoid of gas and stars. But travel 7500 light years in the direction of the constellation Carina and you'll slam into one of the largest and most complex star-forming regions in the galaxy: the sprawling Carina nebula. Massive stars being born there blast out radiation and winds that sculpt the surrounding material, creating weird and wonderful shapes.
So what better way for astronomers to celebrate the Hubble Space Telescope's 20th year in orbit than to use it to take a huge mosaic of Carina? This astonishing portrait shows the towering pillars of gas and dust being eaten away by cosmic erosion; the narrow, focused jets of material blasting away from stars eating away at their cocoons; ribbons and sheets of compressed gas lighting up space; and the nascent stars themselves as they turn on for the first time.
The Whirlpool is actually two galaxies interacting with one another. The spiral galaxy is nearly face-on, and you can easily trace the magnificent arms, laced with red gas clouds forming new stars, and dark lanes of dust created when stars are born and when they die. The other galaxy is the orange blobby one, a dwarf irregular. It may have already passed through the bigger galaxy twice, and will eventually merge with it. We think all big galaxies grow by consuming smaller ones in this manner. In a few hundred million more years there won't be two galaxies left to see, just one somewhat bigger one. Our own Milky Way Galaxy probably underwent a similar event many times! | 0.879398 | 3.289095 |
Given that each light-year — defined as the distance light travels in one Earth year — is about 6 trillion miles (9 trillion km), a black hole that lies 1,000 light-years away may not seem very close. However, to astronomers who are accustomed to cosmic distance scales, the recently-discovered HR 6819's black hole, which lies in the constellation Telescopium, is an extremely close neighbor.
"On the scale of the Milky Way, it's in our backyard," said Thomas Rivinius, an astronomer at the European Southern Observatory (ESO) in Chile who led the research. "Almost on our doorstep." The scientist says it is so close that the black hole's two orbiting stars can be observed with the naked eye in the Southern Hemisphere's skies on a clear night.
A black hole forms when a massive dying star collapses under its own gravity and shrinks until all of its mass is contained in an infinitely dense point called a singularity. Since black holes do not allow light to escape, they remain invisible until their strong gravitational pull starts to draw in nearby stars. The process is so luminous that it can be observed from Earth. "Sometimes they [black holes] become the brightest objects in the sky," says Erin Kara, an astrophysicist at MIT who studies black holes. However, since HR 6819's two stars are too far away to be pulled in by its gravity, the black hole managed to remain undetected despite being so close to Earth.
“It seems like it’s been hiding in plain sight,” says astronomer Kareem El-Badry, a Ph.D. student at the University of California, Berkeley, who specializes in binary star systems but wasn’t involved with the study. “It’s a bright enough star [system] that people have been studying it since the 80s, but it seems like it’s had some surprises.”
The ESO astronomers stumbled upon the discovery when they began analyzing the data collected on the HR 6819 system as part of their research on stars that orbit in pairs. They found that unlike other binary star systems, which move in synch, HR 6819's inner star was orbiting at a much faster pace than its outer star. This led the astronomers to suspect there was a third object located at the center of the star system. After further investigating the inner star's motion and orbit pattern, the team came to the conclusion that the unseen body is a black hole – the remnant of a third star which had once been a part of the HR 6819 star system. Their calculations suggest that the black hole has a mass roughly four times that of our Sun.
The discovery, published in the journal Astronomy & Astrophysics on May 6, 2020, is giving scientists hope that there are many more black holes near Earth that are just waiting to be discovered. "It's important to emphasize that it's the closest we've found yet," says Sera Markoff, an astrophysicist at the University of Amsterdam who was not involved with the latest research. "There might be closer ones."
Resources: TheAtlantic.com, Vox.com, Gizmondo.com | 0.931441 | 3.999966 |
Using footage from the International Space Station (courtesy of NASA’s Johnson Space Center), National Geographic filmmaker Fede Castro has created one of the most breathtaking time-lapse videos of Earth from space.
The video is just over four minutes, and features the world’s major cities, as well as the aurora borealis (Northern Lights) and a few massive thunderstorms, among other things.
Take a trip around the world in just minutes in National Geographic’s video “Nuestra Tierra—Our Earth”:
Okay so everyone hopefully understands that you can’t just simply survive in the openness of outer space. That’s why astronauts are required to wear sophisticated suits to keep them safe.
There are many reasons why outer space is not naturally habitable for humans, the lack of air and extreme temperatures being just the tip of the iceberg.
But with a proper suit built to provide protection and breathable air, one can spend limited amounts of time in outer space.
According to Space.com four of the most hostile elements in space are:
1. The Empty Vacuum – The vacuum force, caused by a lack of air in space, can be large and significant. If instruments are unsealed they can break apart. If an astronaut has a suit leak or damage it will be exposed and compromised.
2. Extreme Temperature/Temperature Variation – According to Space.com,
“If an astronaut’s back is facing the sun and the front is not, the temperature difference can be as much as 275°F”
That is an extreme temperature difference for just the direction that you are facing. Astronaut suits must have heavily shielded face plates to protect astronauts from the sun, as well as the capability to handle both temperature exteremes (hot and cold).
Universetoday.com did a great piece called “How Cold is Space” that helped answer a few questions on how extreme the temperatures get in outer space. According to them, the International Space Station…
“…under constant sunlight can get as hot as 260 degrees Celsius (500 F). This is dangerous to astronauts who have to work outside the station. If they need to handle bare metal, they wrap it in special coatings or blankets to protect themselves. And yet, in the shade, an object will cool down to below -100 degrees Celsius (-148 F).”
3. Meteorite Impacts – Although colliding with other objects in space is rare, it is entirely possible and a legit threat. If you are within the orbit of a planet, where much of this debris gets captured, the threat is even higher.
The amount of satellites in space is growing by the day, steadily increasing the amount of “space junk” within Earth’s orbit. Aside from that, small meteorites zoom past the outskirts of space and into our ozone everyday.
4. Radiation Damage – This is one of the most significant threats in space, especially to equipment. There are several sources and forms of radiation in space which can all be harmful to human health in a large enough dose.
The main issue, however, is that this radiation can damage the finely-tuned instrumentation used by astronauts to do experiments in space. The radiation can alter and destroy data, and eventually renders almost all instruments in space useless.
But the mood has become a bit more somber with the end of the Cup and the resurgence of the conflict in the Middle East.
In a blog post he wrote for the European Space Agency’s website, Gerst gave insight into the astronauts’ perspective on the Israeli-Palestinian conflict. His introduction is very powerful:
“Some things that on Earth we see in the news every day and thus almost tend to accept as a ‘given,’ appear very different from our perspective. We do not see any borders from space.
We just see a unique planet with a thin, fragile atmosphere, suspended in a vast and hostile darkness. From up here it is crystal clear that on Earth we are one humanity, we eventually all share the same fate.
What came to my mind at the time of this photo was, if we ever will be visited by another species from somewhere in the universe, how would we explain to them what they might see as the very first thing when they look at our planet?”
How would we explain to them the way we humans treat not only each other but also our fragile blue planet, the only home we have? I do not have an answer for that.”
On July 15, 1975, NASA launched an Apollo spacecraft carrying three US astronauts. Two days later, on July 17th, this craft docked with the Soviet Union “Soyuz” spacecraft.
The Soviet craft had two Soviet cosmonauts on board and the rendezvous marked the first ever international space mission.
According to NASA, the Apollo-Soyuz mission was,
“Designed to test the compatibility of rendezvous and docking systems and the possibility of an international space rescue, the nine-day Apollo-Soyuz mission brought together two former spaceflight rivals: the United States and the Soviet Union.”
The “Soyuz” spacecraft was the primary Soviet manned spacecraft since it was introduced in 1967.
The docking module used in this mission was designed and constructed by NASA. Prior to the Apollo-Soyuz mission, astronauts had never transferred from one spacecraft to another in outer space.
The docking modules served as an air-locked corridor that allowed the astronauts to travel between the two spacecrafts. The docking was successful.
The U.S. and Soviet astronauts spent two days together, carrying out five joint experiments. At the end of their time together, they exchanged commemorative items.
The success of their mutual efforts paved the way for decades of international cooperation in space exploration, and laid the political groundwork which eventually led to the construction of the International Space Station, which began in November 1998.
On June 12, 2009, the International Space Station’s orbit happened to take it over the Kuril Islands (northeast Japan).
The Kuril Islands were built by volcanic activity and still have active volcanoes. The most active is Sarychev Peak, located on the northwestern end of Matua Island.
Although Sarychev Peak hadn’t erupted since 1989, it was somewhat overdue for one, considering it had previously erupted in 1986, 1976, 1954, and 1946.
By a stroke of luck, the ISS was flying overhead when Sarychev Peak was in the early stages of its eruption on that June day in 2009, and captured a series of amazing images which were converted into the incredible GIF below:
The images (which you can view frame by frame courtesy of NASA here) are remarkable for a number of reasons.
Firstly, there was little to no shearing wind to spread and disperse the ash plume, so the ISS was able to capture crucial features of the eruption, like the pyroclastic flow at the base.
The small white cloud at the top of the ash plume is known as a pileus cloud. It was formed as the eruption rapidly pushed the moist air above the island upwards with the plume. As this moist air is pushed upwards, it cools and condenses, forming a cloud. When a pileus cloud in above an eruption or explosion, it’s called an “ice cap”.
One of the coolest features of these images has actually caused a bit of controversy in the science world. If you look around the edges of the images, you will see that the ash plume is emerging from a large circular opening in the clouds.
When the photo was originally published, NASA postulated that the hole was “punched” through the clouds by the upward shockwave of the eruption. But this explanation sparked a debate between meteorologists, geoscientists, and volcanologists who viewed the images. SInce then, two other possible theories have been proposed.
One is that the hole has nothing to do with the eruption at all. In areas where islands are surrounded by oceans with cool surface temperature, it is very common for sheets of clouds to form and drift along with the low-level winds.
When these clouds drift over an island, the moist air closer to the surface is pushed up by the island. Since the air above the marine layer (where the clouds form) is dryer and warmer than the air over the water, the portion of the cloud over the island evaporates, leaving a hole.
The final theory is that as the ash plume rises, the air above it flows down its sides, like water flowing off the back of a surfacing whale. As this air falls, it tends to warm, which could also cause an evaporation of the clouds around the volcano plume.
Whatever the reason, I think we can all agree that watching a volcano erupt from space is a truly mesmerizing site.
Check out the original post from NASA’s Earth Observatory here.
The World Cup is in full swing, with billions of people tuning in to watch the games all over the planet. But there are also a couple of guys watching the world’s largest sporting event from space.
To commemorate the start of the tournament, NASA astronauts Reid Wiseman and Steve Swanson joined German astronaut Alexander Gerst of the European Space Agency to create this awesome video of them practicing some moves in zero-G.
Then yesterday they released this video of their best goal celebrations:
This is the second World Cup that astronauts have viewed from the International Space Station (they also tuned in for the 2010 Cup). It’s pretty fitting that the astronauts are watching a tournament that brings together countries from all over the world- the ISS itself was built by five different space agencies representing 15 different countries.
The German and American astronauts actually made a bet over yesterday’s game: if the U.S. won, they could draw a U.S. flag on Gerst’s bald head. But if the U.S. lost, both the American’s had to shave their heads. I hope Gerst isn’t rubbing in that German win too much though.
Last month, on May 2, SpaceX conducted a test flight of their new Falcon 9 Reusable (F9R) spacecraft. Check out the video below to see it in action.
The “rocketcams” in the video feature a shot from the nose of the rocket followed by video footage from the ground. The test flight took place in McGregor, Texas under a FAA Experimental Permit.
*The coolest part is the landing in my opinion*
This was a successful 1000m test flight of the F9R, a developing spacecraft that will have the ability to carry astronauts to and from space.
The “steerable fins” included on this spacecraft are unique and allow the rocket to carefully maneuver in mid-air to facilitate a smoother landing. These types of steerable fins have been used on smaller spacecraft by SpaceX earlier this year, but they are now incorporating them on their more important and larger crafts, like the F9R.
The successful testing of the F9R means that SpaceX may soon be sending U.S. astronauts to the ISS (right now we’re contracting Russian shuttles to launch them into orbit). Rocket development and the growth of the space industry are truly in full steam. | 0.810088 | 3.0403 |
Jules Verne (1828-1905) wrote adventure stories about a trip “From the Earth to the Moon” and a visit to “The Mysterious Island;” only two of his many science fiction adventures. His writings inspired the imagination, spurring interest in adventure and scientific exploration for many of us, including the rocket genius Robert Goddard and astronomer Edwin Hubble.
Verne’s imagination has been surpassed by the science of the 21st Century. We know so much more about the world today, and our capabilities of exploring the solar system with robots have yielded hints of other strange worldly places that he never imagined.
Jupiter is so large the entire solar system would fit within its volume and an armada of 69 moons within its gravitational grasp.
On January 7, 1610, Galileo wrote of his discovery of moons orbiting Jupiter and 369 years later the Voyager 1 spacecraft passed by Jupiter imaging its four Galilean moons sending pictures back to earth. Just as mysterious as the story of an undiscovered island from mind of Verne, scientists discovered future adventure for generations of explorers within the Moons of Jupiter.
Imagine, a trip to Jupiter, 500 million miles from the Sun, a planet so large the entire solar system would fit within its volume and an armada of 69 moons within its gravitational grasp. An adventurous voyage of this magnitude would surely merit space within the pages of one of Verne’s books.
Jupiter’s moons vary wildly in size and description, from regular to irregular. The irregular are 60 plus small satellites less than 160 miles in size orbiting in prograde and retrograde directions up to millions of miles from the planet. The regular are much closer, with two having orbital periods less than a Jovian day, and four as large as our own moon.
Io is the closest of the four largest we call the Galilean moons. It orbits Jupiter every 40 hours and is a strange place with more than 100 active volcanos, a thin atmosphere of sulfur dioxide and mountains higher than Mount Everest. Io has temperatures varying from 3,000 F near volcanos to -202 F in frozen fields of sulfur dioxide. An expedition to explore this place would be no less daring than being shot out of a cannon to the Moon.
Yet, the most mysterious moon may be Europa. It’s frozen icy crust is almost devoid of craters revealing dynamics renewing its surface by interaction with subsurface liquid water. Yes water, maybe subterranean lakes and a hidden salty ocean where the wonder of life may exist beyond the bounds of the planet Earth?
NASA is considering a robotic mission to this distant place to fly by and capture water ejected from geysers they have found spouting from Europa’s crust. What would they find within their sample? If life was found it would be as strange as one of Verne’s fantastic tales come to life. Imagine the great burden of scientists on the mission team formulating a message to the public telling them life is not constrained to the Earth alone.
And if we did find life, would humans want to venture to Europa to study the creatures that gave evidence we are not alone? Would we begin a 21st Century legacy of Verne with a trip to The Mysterious Moons of Jupiter? | tahoestartours.com | 0.885937 | 3.452799 |
- The sun, the moon and all those objects shining in the night sky are called celestial bodies
- The celestial bodies which have their own heat and light, which they emit in large amounts are called stars
- Different groups of stars are called constellations. Ex: Ursa Major or Big Bear
- One of the most easily recognizable constellation is the small bear or the Saptarishi, a part of the Ursa Major constellation
- The North Star or the Pole Star indicates the north direction. It always remain in the same position in the sky
- Some celestial bodies do not have their own heat and light. They are lit by the light of the stars. Such bodies are called Planets.
- The word ‘Planet’ comes from the Greek word “Planetai” which means ‘wanderers’.
The Solar System:
The sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the solar system.
- The sun is about 150 million km away from the earth.
- There are eight planets in our solar system. In order of their distance from the sun, they are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
- Mercury is nearest to the sun. Takes only about 88 days to complete one revolution
- Venus is considered as ‘Earth’s-twin’ because its size and shape are very much similar to that of the earth.
- ‘Pluto’ may be called a ‘dwarf planet’.
- The earth is the third nearest planet to the sun.
- In size, it is the fifth largest planet.
- It is slightly flattened at the poles. That is why, its shape is described as a Geoid.
- The earth is a unique planet as it has life-supporting conditions like water, air and oxygen.
- Earth is called a blue planet as its two-thirds surface is covered by water.
- The earth has only one satellite, that is, the moon.
- It’s diameter is only one-quarter that of the earth.
- It is about 3,84,400 km away from the earth.
- The moon moves around the earth in about 27 days. It takes exactly the same time to complete one spin.
- A Satellite is a celestial body that moves around the planets in the same way as the planets move around the sun.
- A Human-made Satellite is an artificial body. It is designed by scientists to gather information about the universe or for communication. Some of the Indian satellites in space are INSAT, IRS, EDUSAT etc.
Apart from the stars, planets and satellites, there are numerous tiny bodies which also move around the sun. These bodies are called asteroids. They are found between the orbits of Mars and Jupiter.
The small pieces of rocks which move around the sun are called meteoroids.
A galaxy is a huge system of billions of stars, and clouds of dust and gases. There are millions of such galaxies that make the Universe. Our solar system is a part of the Milky Way galaxy. | 0.860934 | 3.035114 |
Thursday, February 20, 2020
The Habitable Zone Planet Finder spectrograph at Texas’ Hobby-Eberly Telescope, helped astronomers to verify the existence of an exoplanet first detected by the Kepler spacecraft.
Using the Habitable Zone Planet Finder instrument, a team of scientists – including UCI astronomer Paul Robertson – has confirmed that an object previously detected by the Kepler space telescope is an exoplanet, a planet orbiting a star outside our solar system. The team’s findings were published recently in The Astronomical Journal. Called G 9-40b, the body is about twice the size of the Earth, slightly smaller than Neptune, and orbits a low-mass M dwarf star only 100 light years away. Kepler detected the planet by observing its transit across the star’s front, with an expected dimming of light cast by the host. Through precise measurements of infrared signals, the sophisticated Habitable Zone Planet Finder – or HPF – spectrograph was able to accurately identify G 9-40b as an exoplanet, ruling out the possibility of a close stellar neighbor or binary companion to the dwarf star. High-contrast adaptive optics imaging observations using the ShARCS camera on the 3-meter C. Donald Shane telescope at California’s Lick Observatory showed that the host star was the true source of the transits. | 0.879026 | 3.431961 |
Voyager 1 is now at the edge of the solar system, and the data coming back is surprising astrophysicists. It was generally believed that the transition between the sun’s extended atmosphere and the beginning of interstellar space would be abrupt, but that isn’t proving to be the case:
Voyager 1 has been crusing through these doldrums since April 2010, putting it on the doorstep of the heliopause, the point at which the sun’s atmosphere yields to interstellar space beyond. Indeed, if the new calculations are correct, humanity’s first rudimentary starship – now 34 years into its journey – could break free of the solar system by the end of next year.
The evidence comes from a detector on Voyager that counts the number of protons streaming from the sun as solar wind. By counting the proton hits in all directions, the team can calculate the speed and direction of the solar wind – after adjusting for the spacecraft’s speed of some 38,000 m.p.h.
During the past three years, the wind’s speed has dropped from 93,000 m.p.h. to zip.
“That wasn’t supposed to happen,” says Stamatios Krimigis, a solar physicist and emeritus head of the Space Department at the Johns Hopkins University’s Applied Physics Laboratory in Laurel, Md., who led the team that conducted the study. “We’re not supposed to be in a wind that isn’t going anywhere.”
So, it’s possible for a “consensus of scientists” to be wrong? Somebody alert Al Gore!
Voyager 1 Fun Fact: Within two weeks the spacecraft will enter an area known as the “heliopause,” which is so distant that by the time Anthony Weiner’s sext messages reach it, New Yorkers will have just re-elected him for yet another term in 2024. | 0.85453 | 3.492149 |
The respected physics historia Helge Kragh writes: Galileo in early modern Denmark, 1600-1650
The scientific revolution in the first half of the seventeenth century, pioneered by figures such as Harvey, Galileo, Gassendi, Kepler and Descartes, was disseminated to the northernmost countries in Europe with considerable delay. In this essay I examine how and when Galileo's new ideas in physics and astronomy became known in Denmark, and I compare the reception with the one in Sweden. It turns out that Galileo was almost exclusively known for his sensational use of the telescope to unravel the secrets of the heavens, meaning that he was predominantly seen as an astronomical innovator and advocate of the Copernican world system. Danish astronomy at the time was however based on Tycho Brahe's view of the universe and therefore hostile to Copernican and, by implication, Galilean cosmology. Although Galileo's telescope attracted much attention, it took about thirty years until a Danish astronomer actually used the instrument for observations. By the 1640s Galileo was generally admired for his astronomical discoveries, but no one in Denmark drew the consequence that the dogma of the central Earth, a fundamental feature of the Tychonian world picture, was therefore incorrect.This is not surprising. The Dane Tycho invented the instruments that made the best astronomical observations in the world, and that data was used for the best models. Galileo had nothing to compete with that.
Galileo said Mathematics is the language in which God has written the universe, but his telescopic observations and heliocentric arguments were not very mathematical.
Whereas Galileo was well known and highly reputed in the first two decades of the seventeenth century, it took longer before he was discovered by astronomers and natural philosophers in the Nordic countries. Tycho Brahe was aware of him at an early date, but he was an exception. The first time Galileo was mentioned in print by a Danish scholar was in 1617, and five years later he appeared in a Swedish publication. Yet, still around 1640 there were only few references to his scientific work. What eventually attracted attention to the innovative Italian were almost exclusively his astronomical discoveries made by means of the amazing telescope. His advocacy of the Copernican world system was noted, but without making any impact. In the first half of the century there still were no Copernicans in either Denmark or Sweden. Astronomers were either Tychonians or supporters of the Ptolemaic theory.Kepler's astronomy was a whole lot more important than Galileo's during this period. Galileo was the first to publish observations about the moons of Jupiter, but others made the same conclusions once they get telescopes. Kepler had a sophisticated mathematical model that was way beyond Tycho's, and Tycho's was way beyond Galileo's. There was no good reason for Danes to pay much attention to Galileo's astronomy. Galileo's confrontation with the Pope made a good story, but scientifically, it wasn't that important.
Galileo’s international fame undoubtedly rested on his telescopic discoveries, but of course he also did pioneering work in mechanics and other branches of natural philosophy. First of all, he introduced the experimental method. There seems to be no mention in the Danish scholarly literature of the physical rather than astronomical Galileo. One looks in vain for awareness of or comments on his theory of the pendulum, his laws of freely falling bodies or his ideas about inertial motion; nor is his views on atomism, the void and the nature of heat to be found in the learned literature. These parts of Galileo’s work were foreign to Danish natural philosophers who predominantly thought in terms of Aristotelian concepts and tended to interpret the Bible quite literally. The situation in Sweden was not very different. Finally it is worth mentioning that apparently the process against Galileo in 1633 did not create much interest. It was known but not, as far as I can tell, discussed in print until much later. | 0.83439 | 3.245679 |
If there were ever a planet with an unfair reputation for its inability to be readily observed, it would have to be Mercury, which is known in some circles as the "elusive planet." But over the next two weeks, skywatchers will have an excellent opportunity to see Mercury in the early morning dawn sky.
Mercury is often cited as the most difficult of the five brightest naked-eye planets to see, because it is the planet closest to the sun. As such, it never strays too far from the sun’s vicinity in our sky.
Mercury is called an "inferior planet" because its orbit is nearer to the sun than the Earth's orbit. From our vantage point, it always appears to be in the same general direction as the sun. Thus, relatively few people have set eyes on it; there is even a rumor that the great Polish astronomer, Nicolaus Copernicus, never saw it. [Mercury Quiz: How Well Do You Know the Innermost Planet?]
Yet, it's not particularly hard to see Mercury. You simply must know when and where to look, and find a clear horizon.
Mercury was very near to the sun on Nov. 1. In its orbit, Mercury crossed to the north side of the ecliptic, or the sun's apparent path, on Nov. 3 (a boon to observers in the Northern Hemisphere). The planet reached perihelion — its closest point to the sun — four days later, when its angular motion around the sun was greatest. This combination of geometries is what suddenly brought this speedy planet into view in the morning sky.
If you are an early riser, it's possible you may have stumbled across Mercury on your own recently. Since Nov. 12, it has been rising at least 90 minutes before sunrise, which is also just about the same time that morning twilight is beginning. If you scan low along the east-southeast horizon about 45 minutes before sunrise, Mercury is visible as a distinctly bright, yellowish-orange "star." [Stargazer Photos: Amazing November Night Sky Views]
This past weekend, Mercury rose more than 100 minutes before the sun, even before the break of dawn. This means, for a short while, Mercury will be visible against a completely dark sky.
Mercury's greatest western elongation, or its greatest angular distance from the sun in the sky, occurred Monday morning (Nov. 18), with the planet appearing a full 20degreesfrom the sun. Mercury, like Venus, appears to go through phases like the moon. Soon after it moved into the morning sky, Mercury was just a skinny crescent.
Currently, the planet appears roughly half-illuminated and the amount of its surface illuminated by the sun will continue to increase in the days to come. The phases are best viewed by aiming a telescope at Mercury and tracking it through sunrise, to bring the planet higher in the sky.
Although it will begin to turn back toward the sun's vicinity this week, it will brighten a bit more, which should help keep it in easy view over the next couple of weeks.
Toward the end of November, Mercury will increase in brightness to magnitude –0.6. Astronomers refer to the magnitude of a star or planet to determine how bright an object appears in the night sky. Put simply, the lower the magnitude of an object, the brighter it appears in the sky. Among stars, only Canopus and Sirius are brighter than magnitude -0.6. At the end of the month, Mercury should still be relatively easy to find, low in the east-southeast sky about 45 minutes before sunrise.
Here comes Saturn
Near the end of the month, Mercury will also have a close encounter with another bright planet: Saturn.
Like two ships passing in the twilight, Mercury will approach the ringed planet Saturn during the final week of November. Mercury will appear to fall back toward the sun, while Saturn will appear to climb out of the solar glare. The two planets will appear closest together on Nov. 26.
We will have more to say about this "dynamic duo" later this month.
Editor's note: If you have an amazing photo of Mercury or any other night sky object, and you'd like to share it for a possible story or image gallery, please contact managing editor Tariq Malik at [email protected].
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmer's Almanac and other publications, and he is also an on-camera meteorologist for News 12 Westchester, N.Y. Follow SPACE.com on Twitter @Spacedotcom. We're also on Facebook & Google+. Original story on SPACE.com. | 0.87035 | 3.632403 |
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